Document ID: EPA-HQ-OW-2016-0405-0208
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2023-05-05T04:00Z

Economic Analysis for Proposed Federal Baseline Water Quality Standards for Indian Reservations
                                       
                                       
                                       
                                       
                                 April 5, 2023
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                 Prepared for:
                 United States Environmental Protection Agency
                                Office of Water
                       Office of Science and Technology
                        1200 Pennsylvania Avenue, N.W.
                            Washington, D.C. 20460

Table of Contents
Acronyms and Abbreviations	viii
Executive Summary	1
1.	Introduction	9
1.1	Background	9
1.1.1	Regulatory Background	9
1.2	Purpose and Scope of the Analysis	10
1.3	Report Organization	11
2.	Applicability and Current Regulatory Framework	13
2.1	Indian Reservations and Waters Subject to the Analysis	13
2.2	Current Regulatory Framework on these Lands/Waters	14
3.	Derivation of Economic Analysis Criteria	16
3.1	Overall Assumptions for Purposes of this Analysis	16
3.1.1	Applicable Designated Uses	16
3.1.2	Aquatic Life Criteria	17
3.1.3	Human Health Criteria	17
3.2	Geographic-Specific Assumptions	19
3.2.1	Fish Consumption Rates	19
3.2.2	Great Lakes Initiative	19
3.3	Economic Analysis Criteria	20
4.	Potential Benefits	26
4.1	Human Health Benefits	26
4.1.1	Reduced Health Risk from Fish, Shellfish, and Aquatic Plant Consumption	27
4.1.2	Benefits from Improved Water Quality in Drinking Water Sources	28
4.1.3	Reduced Risk of Gastrointestinal Illnesses from Recreation	29
4.2	Market Benefits	29
4.2.1	Commercial Fisheries	30
4.2.2	Enhanced Property Values	30
4.3	Nonmarket Water Quality Benefits	31
4.3.1	Cultural and Traditional Use Benefits	31
4.3.2	Recreational Benefits	32
4.3.3	Nonuse Benefits	32
4.4	Summary of Benefits	33
5.	Method for Estimating Potential Costs: Point Sources	35
5.1	Identification of Potentially Affected Permittees	35
5.1.1	Methodology for Sampling	37
5.1.2	Extrapolation Process	39
5.2	Determining Reasonable Potential	39
5.3	Projecting Effluent Limits	41
5.4	Identifying Control Scenarios	45
5.4.1	Process Optimization	45
5.4.2	Source Controls (Pollution Prevention Programs)	46
5.4.3	Effluent Treatment	48
5.4.4	Alternative Compliance Mechanisms	49
6.	Method for Identifying Potential Impairments and Characterization of Nonpoint Sources	51
6.1	Available Data to Evaluate Impairments	51
6.2	Identifying Potential Impairments	53
6.3	Nonpoint Source Discharge Categories	54
6.3.1	Agriculture	54
6.3.2	Forestry	55
6.3.3	Mining	55
6.3.4	Septic Systems	56
6.3.5	Atmospheric Deposition	57
6.3.6	Contaminated Sediments/Legacy Sources	57
6.4	Identifying Potential Control Actions and Costs	58
7.	Potential Compliance Costs	60
7.1	Potential Compliance Costs for Point Sources	60
7.2	Potential Compliance Costs for Nonpoint Sources and Stormwater	66
7.3	Uncertainties in the Analysis	66
7.3.1	Data Limitations	66
7.3.2	Point Source Load Reductions	68
7.3.3	Response to Requirements	68
References	69
Appendix A - Facility Analyses	74
Appendix B - Source Control and Alternative Compliance Mechanism Supplemental Information and Costs	139
Appendix C - Effluent Treatment Control and Costs	143
Appendix D - Pollutant Impacts	153

List of Exhibits
Exhibit ES-1 Summary of Estimated Potential Costs (2020 $Millions) for Major Facilities	7
Exhibit 2-1 Indian Reservations with Waters in Yellow and White Included in this Analysis	14
Exhibit 3-1 Detection Limits and Aquatic Life Economic Analysis Criteria (ug/L)	20
Exhibit 3-2 Detection Limits and Human Health Economic Analysis Criteria (expressed in ug/L, unless specified otherwise)	22
Exhibit 4-1 Human Health Effects Associated with Pollutants with Potential Impairments based on Economic Analysis Criteria	27
Exhibit 4-2 Summary of Benefits from Promulgating WQS for Indian Reservation Waters	34
Exhibit 5-1 NPDES Facilities that May be Affected by the Proposed Baseline WQS	36
Exhibit 5-2 Sample NPDES Dischargers for Reasonable Potential Analyses	38
Exhibit 5-3 Pollutants Triggering RP for Sample NPDES Dischargers	40
Exhibit 5-4 Summary of WQBELs for Sampled Facilities (ug/L unless specified otherwise)	43
Exhibit 5-5 Summary of Potential Effluent Treatment Technologies	48
Exhibit 6-1 Available Water Quality Data for Tribal Waters for Parameters with Economic Analysis Criteria	52
Exhibit 6-2 Number of Reaches on Indian Reservation Waters that are Potentially Impaired by Economic Analysis Criteria and Parameter*	53
Exhibit 6-3 Potential Control Actions Required for Nonpoint Sources of Contamination	58
Exhibit 7-1 Estimated Potential Costs (2020 dollars) for Facilities Discharging to Indian Reservation Waters	62
Exhibit 7-2 Estimated Potential Costs (2020 dollars) for Industrial Facilities Discharging Upstream of Indian Reservation Waters	63
Exhibit 7-3 Estimated Potential Costs (2020 dollars) for Sample Sewerage Treatment Plants Discharging Upstream of Indian Reservation Waters	64
Exhibit 7-4 Summary of Estimated Potential Costs (2020 $Millions) for Major Facilities	65
Exhibit A-1: Summary of Available Effluent Data for CRSJV (ug/L)	75
Exhibit A-2: Summary of Reasonable Potential Analysis for CRSJV (ug/L)	76
Exhibit A-3: Summary of Limits for Parameters with Reasonable Potential (ug/L)	76
Exhibit A-4: CRSJV Estimated Incremental Costs (1.2 MGD)	77
Exhibit A-5: Summary of Available Effluent Data for Mesa Northwest (ug/L)	78
Exhibit A-6: Summary of Reasonable Potential Analysis for Mesa Northwest (ug/L)	78
Exhibit A-7: Summary of Limits for Mesa Northwest for Parameters with Reasonable Potential (ug/L)	79
Exhibit A-8: Summary of Available Effluent Data for Mt. Pleasant WWTP	80
Exhibit A-9: Summary of Limits for Mt. Pleasant for Parameters with Reasonable Potential (cfu/100 mL)	80
Exhibit A-10: Summary of Available Effluent Data for Pearl River WWTP (ug/L)	82
Exhibit A-11: Summary of Reasonable Potential Analysis for Pearl River WWTP (ug/L)	82
Exhibit A-12: Summary of Limits for Pearl River WWTP for Parameters with Reasonable Potential (ug/L)	83
Exhibit A-13: Pearl River WWTP Estimated Incremental Costs (1.50 MGD)	84
Exhibit A-14: Summary of Available Effluent Data for City of Hardin WTP (ug/L)	85
Exhibit A-15: Summary of Reasonable Potential Analysis for City of Hardin WTP (ug/L)	86
Exhibit A-16: Summary of Limits for City of Hardin WTP for Parameters with Reasonable Potential (ug/L)	86
Exhibit A-17: City of Hardin Estimated Incremental Costs (2.16 MGD)	87
Exhibit A-18: Summary of Available Effluent Data for Salamanca WWTP (ug/L)	88
Exhibit A-19: Summary of Reasonable Potential Analysis for Salamanca WWTP (ug/L)	89
Exhibit A-20: Summary of Limits for Salamanca WWTP for Parameters with Reasonable Potential (ug/L)	89
Exhibit A-21: Salamanca WWTP Estimated Incremental Costs (2.00 MGD)	90
Exhibit A-22: Summary of Available Effluent Data for City of Phoenix WWTP (ug/L)	90
Exhibit A-23: Summary of Reasonable Potential Analysis for City of Phoenix WWTP (ug/L)	91
Exhibit A-24: Summary of Calculated Limits for Parameters with Reasonable Potential for City of Phoenix WWTP (ug/L)	92
Exhibit A-25: City of Phoenix WWTP Estimated Incremental Costs (230 MGD)	93
Exhibit A-26: Summary of Available Effluent Data for Town of Florence WWTP (ug/L)	95
Exhibit A-27: Summary of Reasonable Potential Analysis for Town of Florence WWTP (ug/L)	96
Exhibit A-28: Summary of Calculated Limits for Parameters with Reasonable Potential for Town of Florence WWTP (ug/L)	96
Exhibit A-29: Town of Florence WWTP Estimated Incremental Costs (2.5 MGD)	98
Exhibit A-30: Summary of Available Effluent Data for Coachella Mid-Valley WRC (ug/L)	100
Exhibit A-31: Summary of Reasonable Potential Analysis for Coachella Mid-Valley WRC (ug/L)	101
Exhibit A-32: Summary of Calculated Limits for Parameters with Reasonable Potential for Coachella Mid-Valley WRC (ug/L)	102
Exhibit A-33: Coachella Mid-Valley WRC Estimated Incremental Costs (9.9 MGD)	104
Exhibit A-34: Summary of Available Effluent Data for Pagosa Area WWTP (ug/L)	105
Exhibit A-35: Summary of Reasonable Potential Analysis for Pagosa Area WWTP (ug/L)	106
Exhibit A-36: Summary of Calculated Limits for Parameters with Reasonable Potential for Pagosa Area WWTP (ug/L)	107
Exhibit A-37: Pagosa Area WWTP Estimated Incremental Costs (3.9 MGD)	109
Exhibit A-38: Summary of Available Effluent Data for CF Industries Nitrogen (ug/L)	110
Exhibit A-39: Summary of Reasonable Potential Analysis for CF Industries Nitrogen (ug/L)	110
Exhibit A-41: Summary of Available Chlorine Effluent Data for Neal South (ug/L)	113
Exhibit A-42: Summary of Chlorine Reasonable Potential Analysis for Neal South by Outfall (ug/L)	113
Exhibit A-44: Summary of Available Effluent Data for Pocatello WPCF (ug/L)	115
Exhibit A-45: Summary of Reasonable Potential Analysis for Pocatello WPCF (ug/L)	116
Exhibit A-46: Summary of Calculated Limits for Parameters with Reasonable Potential for Pocatello WPCF (ug/L)	116
Exhibit A-47: Pocatello WPCF Estimated Incremental Costs (12 MGD)	117
Exhibit A-48: Summary of Available Effluent Data for City of Devils Lake WWTF (ug/L)	118
Exhibit A-49: Summary of Reasonable Potential Analysis for City of Devils Lake WWTF (ug/L)	118
Exhibit A-50: Summary of Calculated Limits for Parameters with Reasonable Potential for City of Devils Lake WWTF (ug/L)	119
Exhibit A-51: Summary of Available Effluent Data for MG Waldbaum (ug/L)	120
Exhibit A-52: Summary of Reasonable Potential Analysis for the MG Waldbaum (ug/L)	120
Exhibit A-53: Summary of Calculated Limits for Parameters with Reasonable Potential for MG Waldbaum (ug/L)	121
Exhibit A-54: MG Waldbaum Estimated Incremental Costs (0.70 MGD)	122
Exhibit A-55: Summary of Available Effluent Data for Los Alamos WWTF (ug/L)	122
Exhibit A-56: Summary of Reasonable Potential Analysis for Los Alamos WWTF (ug/L)	123
Exhibit A-57: Summary of Calculated Limits for Parameters with Reasonable Potential for Los Alamos WWTF (ug/L)	123
Exhibit A-58: Summary of Available Effluent Data for Los Alamos Lab, Outfall 001 (ug/L)	125
Exhibit A-59: Summary of Reasonable Potential Analysis for Los Alamos Lab, Outfall 001 (ug/L)	125
Exhibit A-60: Summary of Calculated Limits for Parameters with Reasonable Potential for Los Alamos National Laboratory, Outfall 001 (ug/L)	126
Exhibit A-61: Summary of Available Effluent Data for the Phillips 66 Ponca City Refinery (ug/L)	127
Exhibit A-62: Summary of Reasonable Potential Analysis for Phillips 66 (ug/L)	127
Exhibit A-63: Summary of Calculated Limits for Parameters with Reasonable Potential for Phillips 66 (ug/L)	128
Exhibit A-64: Phillips 66 Ponca City Refinery Estimated Incremental Costs (5.32 MGD)	128
Exhibit A-65: Summary of Available Effluent Data for Kenyon Industries, Inc. (ug/L)	129
Exhibit A-66: Summary of Reasonable Potential Analysis for Kenyon Industries, Inc. (ug/L)	130
Exhibit A-67: Summary of Calculated Limits for Parameters with Reasonable Potential for Kenyon Industries, Inc. (ug/L)	130
Exhibit A-68: Kenyon Industries Estimated Incremental Costs (0.55 MGD)	131
Exhibit A-69: Summary of Available Effluent Data for Bustamante WWTF (ug/L)	132
Exhibit A-70: Summary of Reasonable Potential Analysis for Bustamante WWTF (ug/L)	133
Exhibit A-71: Summary of Calculated Limits for Parameters with Reasonable Potential for Bustamante WWTF (ug/L)	133
Exhibit A-72: Bustamante WWTF Estimated Incremental Costs (39 MGD)	133
Exhibit A-73: Summary of Available Effluent Data for Domtar A.W., LLC WRC (ug/L)	135
Exhibit A-74: Summary of Reasonable Potential Analysis for Domtar A.W., LLC WRC (ug/L)	135
Exhibit A-75: Summary of Available Effluent Data for the Baraboo WWTP (ug/L)	136
Exhibit A-76: Summary of Reasonable Potential Analysis for the Baraboo WWTP (ug/L)	137
Exhibit A-77: Summary of Calculated Limits for Parameters with Reasonable Potential for the Baraboo WWTP (ug/L)	137
Exhibit A-78: City of Baraboo WWTP Estimated Incremental Costs (2.53 MGD)	138
Exhibit B-1 Potential Initial and Annual Cost for P2 Program for Copper[a]	139
Exhibit B-2 Potential Level of Effort to Investigate Technological Feasibility for a Variance	140
Exhibit B-3 Potential One-Time Cost to Apply for and Review WQS Variances for Economic and Social Impacts (40 CFR 131.10(g)(6))	141
Exhibit B-4 Potential Costs for a Dilution Study	141
Exhibit C-5 Parameters Provided for Costing RO and Ion Exchange Systems for Wastewater	150
Exhibit D-1 Parameters with Potential Human Health Criteria Impairments and Adverse Health Impacts[a]	153
Exhibit D-2 Parameters with Potential Aquatic Life Impairments and Adverse Impacts to Aquatic Species[a]	154

Acronyms and Abbreviations 
AL	Aquatic life
AML	Average monthly limit
ATSDR	Agency for Toxic Substances and Disease Registry 
AWQC	Ambient water quality criterion 
BAF 	Bioaccumulation factor 
BHC	Benzene hexachloride 
BLS	Bureau of Labor Statistics
BLM	Biotic Ligand Model
BMP	Best management practice
BOD	Biochemical oxygen demand
BOD5	Five-day biochemical oxygen demand
BW	Body weight 
°C 	Degrees Celsius
CBOD	Carbonaceous biochemical oxygen demand
CFR	Code of Federal Regulations 
cfu 	Colony-forming units 
CV	Coefficient of variation
DL	Detection limit
CWA	Clean Water Act
DDT 	Dichlorodiphenyltrichloroethane
DI	Drinking water intake 
DOC	Dissolved organic carbon
ECHO	Enforcement and Compliance History Online
EPA	United States Environmental Protection Agency
FCR	Fish consumption rate
FI	Fish intake
FWS	United States Fish and Wildlife Service 
GAC	Granular activated carbon
GIS	Geographic information system
GLI	Great Lakes Initiative
gpd	Grams per day
HCH	Hexachlorocyclohexane
HH	Human health
HUC	Hydrologic Unit Code
ICIS	Integrated Compliance Information System
kg	Kilograms
L	Liter
LTA	Long-term average 
MCL	Maximum contaminant level
MCLG	Maximum contaminant level goal
MDL	Maximum daily limit
MGD	Million gallons per day
mg/L	Milligrams per liter
MRDS 	Mineral Resources Data System (from USGS)
N/A	Not applicable
NEMI 	National Environmental Methods Index 
NHD	National Hydrography Dataset
NOAA	National Oceanic and Atmospheric Administration 
NPDES	National Pollutant Discharge Elimination System
O&M	Operation and maintenance
PAH 	Polycyclic aromatic hydrocarbons
PCBs 	Polychlorinated biphenyls
POTW	Publicly owned treatment works
P2	Pollution prevention
RfD 	Reference dose based on noncancer human health effects 
RMZ	Regulatory mixing zone
RP	Reasonable potential
RPA	Reasonable potential analysis
RSC 	Relative source contribution
T&E	Threatened and endangered
TAS 	Treatment in a similar manner as a state
TBEL	Technology-based effluent limit
TCDD	2,3,7,8-Tetrachlorodibenzo-p-dioxin
TDS	Total dissolved solids
THM	Trihalomethane
TRC	Tissue residual concentration 
TSS 	Total suspended solids 
ug/L	Micrograms per liter
USGS	United States Geological Survey
WLA	Wasteload allocation
WPCF	Water pollution control facility
WQBEL	Water quality-based effluent limit
WQC	Water quality criterion
WQP	Water quality portal
WQS	Water quality standards
WRF	Wastewater reclamation facility
WRP 	Water reclamation plant 
WTP	Water treatment plant
WWTF	Wastewater treatment facility
WWTP	Wastewater treatment plant

Executive Summary
The United States Environmental Protection Agency (EPA) is proposing to establish federal water quality standards (WQS) for Indian reservation waters that currently do not have WQS in effect under the Clean Water Act (CWA or the Act), with limited exceptions. Such WQS (referred to as baseline WQS) would establish human health and environmental objectives as the basis for CWA protections for these Indian reservation waters. This report is an economic analysis that provides estimates of the potential compliance actions and costs that may be associated with such baseline WQS and identifies the potential benefits and beneficiaries of the standards.
Background
Although over 300 Tribes with Indian reservations could apply to administer their own WQS program under the CWA, only 84 Tribes have been found eligible to administer a WQS program (i.e., have obtained approval for treatment in a similar manner as a state, or TAS). EPA has approved WQS for 47 of these Tribes and has promulgated federal WQS for one Tribe (the Colville Reservation). 
As a result, 50 years after enactment of the CWA, over 80% of Indian reservations do not have this foundational protection for their waters as authorized by Congress in the CWA. Therefore, EPA is proposing to promulgate baseline WQS for Indian reservation waters that do not have CWA-effective WQS in place. The term "reservation" includes all lands formally designated as reservations by the United States, and lands held in trust by the United States for the benefit of Tribal governments ("Tribal trust lands") that may not be located within the boundaries of formal reservations. 
Having such baseline WQS, together with WQS already approved or promulgated by EPA, would ensure that all Tribes have access to full water quality protections for their reservations under the CWA. 
Purpose and Scope of Analysis 
The purposes of this document are to estimate the costs that could arise as a result of promulgating baseline WQS and identify the potential benefits and beneficiaries of the baseline WQS. The document also describes how the proposed standards could benefit stakeholders (e.g., health, improved recreation opportunities). 
WQS themselves do not impose costs on any entity. The purpose of the cost analysis is to identify, using available water quality and discharge data and information, the potential control actions and costs that publicly owned treatment works (POTWs), industrial point source dischargers, and other regulated point source dischargers may incur as a result of implementing the baseline WQS.
The proposed baseline WQS may impact dischargers to waters located within the boundaries of the Indian reservations themselves, as well as dischargers to waters of other jurisdictions shared with, or upstream from, the reservations. The proposed baseline WQS may result in new or more stringent water quality-based effluent limits (WQBELs) in the National Pollutant Discharge Elimination System (NPDES) permits for discharging facilities. The estimates of nationwide control costs in this analysis reflect the potential impacts of such new or more stringent WQBELs. 
Although the focus of the cost analysis is to estimate control costs for point sources, attaining the proposed baseline WQS would likely depend on additional actions such as nonpoint source controls. Nonpoint source controls, whether required through a nonpoint source program or implemented voluntarily, may lead to nonpoint sources incurring costs as an indirect result of the proposed baseline WQS. Conversely, implementing nonpoint source controls may relieve a portion of the estimated indirect burden on and cost to point sources within the same watershed. However, quantitative evaluation of the potential control needs beyond those addressed under the NPDES program is not possible given the limited available data. Thus, EPA identified the types of controls and unit costs that may be incurred for nonpoint sources but did not develop nationwide nonpoint source cost estimates.
Costs are anticipated to be accompanied by benefits resulting from the control actions. Economic impacts in the form of municipal and industrial expenditures financed through user fees and profits would be accompanied by increased employment, incomes, revenues, and profits to sectors supplying treatment technologies and services (which may be within or external to Tribal areas). The scope of this analysis is limited to qualitatively identifying and describing the potential benefits of promulgating baseline WQS for Indian reservation waters.
This economic analysis covers Indian reservation waters where the proposed baseline WQS would apply, with certain exceptions. Specifically, the economic analysis covers all Indian reservation waters with the following exclusions, per the proposed rule, and exceptions, for the purposes of the economic analysis:
Exclusion: Indian reservation waters where EPA has approved TAS for the Tribe and the Tribe has adopted WQS that EPA has approved  -  currently the 47 Tribes mentioned above. Exception: The economic analysis does not make any adjustments for future TAS approvals. 
Exclusion: Indian reservation waters where EPA has promulgated other federal WQS for a Tribe  -  currently the Confederated Tribes of the Colville Reservation (see 40 CFR 131.35, finalized in 1989). Exception: The economic analysis does not make any adjustments for future such promulgations. 
Exclusion: Indian reservation waters where a Tribe cannot adopt its own WQS because EPA has explicitly found that a state has jurisdiction to administer WQS for those waters  -  currently for 12 Tribes in four states, plus any Tribal waters for which state jurisdiction is granted in the future. Exception: The economic analysis does not make any adjustments for future such jurisdictional findings. Additional exception: The economic analysis does not examine any Indian reservation lands in Oklahoma due to the lack of appropriate geospatial information. For example, for many Oklahoma Tribes the only lands potentially covered by the proposed baseline WQS would be checkerboarded Tribal trust lands for which EPA has no reliable geospatial information. 
Exclusion: Indian reservation waters where the Regional Administrator uses authority in the proposed rule to approve an additional exclusion in the future on a case-by-case basis in consultation with the affected Tribe. Exception: The economic analysis does not make any adjustments for such future actions.
Current Regulatory Framework
The current regulatory framework is the set of currently applicable requirements under the CWA without this proposed rule. These requirements include the following two elements of the NPDES program.
Technology-based effluent limits (TBELs). These include secondary treatment standards for POTWs prior to discharge  -  including five-day biochemical oxygen demand (BOD5), total suspended solids removal, and pH  -  and best available treatment standards for industrial dischargers, including requirements established for their industry through EPA's effluent limitations and guidelines regulations (effluent guidelines), when available. TBELs are based on best professional judgement on a case-by-case basis in the absence of national guidelines.
WQBELs. These limits are established whenever a discharge causes, has the reasonable potential to cause, or contributes to an excursion above any applicable CWA WQS. For example, even where there are currently no applicable WQS for a water body, WQBELs may be needed to comply with the applicable WQS of a downstream jurisdiction at the boundary of the reservation. 
Some Tribes may have adopted standards solely under Tribal law, and those standards may have guided EPA permit writers when setting effluent limits. In addition, some facilities may have effluent limits based on requirements in neighboring states. For purposes of this economic analysis, point source costs only reflect incremental changes that are needed to comply with new or more stringent effluent limits derived from the proposed baseline WQS.
Economic Analysis Criteria Used in the Economic Analysis
EPA is proposing to promulgate narrative criteria with binding numeric translation procedures designed to protect the designated uses promulgated by this rule. The binding numeric translation procedures include the ability to rely on EPA's national CWA section 304(a) recommended quality criteria to protect human health and aquatic life. The numeric values and their relevant assumptions identified in this document were developed solely for the purposes of this economic analysis. They are not final criteria that would apply to Indian reservation waters and are referred to as "economic analysis criteria" for purposes of this document. 
The economic analysis criteria include EPA's national CWA section 304(a) recommended water quality criteria to protect human health and aquatic life with some exceptions discussed below. 
For purposes of this analysis, EPA made the following assumptions: 
 Standards for all waters, including coastal environments, are assumed to be protective of fish and shellfish harvesting for human consumption, and of the protection and propagation of aquatic life.
 All Indian reservation waters are assumed to be designated for protection of cultural and traditional uses and rely on criteria developed to protect drinking water sources (excluding coastal saltwater environments).
 All Indian reservation waters are assumed to be designated for primary contact recreation, which would rely on EPA's 2012 recreational water quality criteria. 
EPA calculated most water quality criteria for the protection of human health based on consumption of water and organisms (e.g., fish), as well as on consumption of organisms only, using the latest federal methodology and using a fish consumption rate (FCR) of 142 grams per day to account for subsistence fishing practices (EPA, 2000).
In March 1995, EPA published a regulation at 40 Code of Federal Regulations (CFR) Part 132, Water Quality Guidance for the Great Lakes System, commonly known as the Great Lakes Initiative (GLI), which provides detailed methodologies to develop criteria for Great Lakes waters. Great Lakes states and Tribes are required to adopt WQS as protective as the water quality criteria, methodologies, policies, and procedures in the GLI. For the purposes of this analysis, EPA calculated criteria specific to the Great Lakes region for Indian reservation waters located in the Great Lakes system using the more stringent of the GLI-calculated criteria or the criteria calculated using the methodologies, policies and procedures used to develop criteria for the rest of the country.
The economic analysis criteria were calculated based on the assumptions outlined above. In addition, for these pollutants, EPA identified the lowest detection limits (DLs) for readily available methods approved in the 40 CFR Part 136 Guidelines Establishing Test Procedures for the Analysis of Pollutants. The DL is the minimum concentration that can be measured and reported with 99% confidence that the concentration is greater than zero. When identifying control costs, EPA assumed that if a calculated WQBEL for a parameter is less than the DL, the discharger may have to ensure that it controls the discharge of that parameter to a level where it is not detected in the discharger's effluent.
Benefits Evaluation
Improved water quality in Indian reservation waters will benefit Tribes as well as anyone who recreates on Indian reservation waters or values environmental quality regardless of their current or anticipated uses of Indian reservation waters. Water quality improvements on Indian reservations are particularly important to Tribal communities because natural resources are often integral to the Tribes' subsistence, spirituality, culture, and daily life. Ceremonial and subsistence harvests of fish and shellfish can play a central role in daily nutrition and Tribal gatherings. Indian reservations also attract visitors from around the world. The Navajo Nation, for example generates millions of dollars in revenue each year and creates over a thousand jobs (Navajo Tourism Department, 2012). 
Although the proposed baseline WQS for Indian reservation waters would likely yield benefits to Tribal members, estimating the dollar value of these improvements to Tribal members may not be feasible recognizing the difficulty often expressed by Tribes to place a monetary value on ecosystem services, given the belief that these resources are sacred and beyond any earthly value. In addition, estimating the value of water quality improvements to visitors of Indian reservations is also challenging due to the paucity of site-specific visitation, use (e.g., recreational fishing) and valuation data. 
Therefore, EPA assessed benefits from the baseline WQS proposed rule qualitatively. Potential benefits include reduced human health risks from fish/shellfish consumption and water recreation and consumption, larger fish and shellfish populations, enhanced property values, improved water supplies, improved water quality for cultural and traditional uses, enhanced recreational uses, and other nonuse values. Section 4 discusses these benefit categories in more detail. 
Method for Evaluating Potential Costs for Point Sources
EPA used a multi-step method for evaluating the effect of the proposed baseline WQS applying to point sources. This method included the following steps: identification of potentially affected permittees, process for selecting a sample of permits and for extrapolating results, determining the need for WQBELs (reasonable potential analysis), and projecting effluent limits.
The potential control actions to meet those limits are based on likely sources of the pollutants in the effluent and the effectiveness of different methods to reduce effluent concentrations. Dischargers would most likely pursue the lowest cost means available for meeting effluent limits. Dischargers would most likely first evaluate whether they can optimize current treatment processes to increase pollutant removal efficiencies (e.g., adding chemicals to increase flocculation efficiency in an existing chemical precipitation treatment unit). As part of this effort, dischargers may also try to identify potential upstream sources of pollution through a source control program (e.g., pollution prevention (P2)). If optimizing processes and/or source control are insufficient for the discharger to meet their effluent limits, dischargers may pursue installing effluent treatment technology. If none of the control scenarios discussed above result in meeting all relevant effluent limitations, dischargers would likely pursue some form of relief from the requirements through alternative compliance mechanisms such as WQS variances or dilution credits (e.g., new or revised mixing zones).
Method for Identifying Potential Water Quality Impairments
EPA downloaded available instream monitoring water quality data in Indian reservation waters from the EPA and U.S. Geological Survey's Water Quality Portal (WQP) and compared it to the economic analysis criteria to identify stream reaches from the National Hydrography Dataset that do not meet the proposed baseline WQS. Although not necessarily representative of all Indian reservation surface waters, the locations for which monitoring data exceed the economic analysis criteria are places where additional nonpoint controls could improve water quality.
EPA did not estimate the costs of reducing pollution from nonpoint sources to meet the economic analysis criteria for this analysis. This type of analysis would require site-specific knowledge and modeling that are beyond the scope of this analysis. Nonpoint source discharges are difficult to quantify because they are intermittent, variable, and occur under hydrologic or climatic conditions associated with precipitation events. In addition, nonpoint sources are not subject to regulatory programs under the CWA. 
Results
Point Source Costs
EPA identified facilities discharging to Indian reservation waters as well as facilities within a five-mile radius and discharging upstream from Indian reservation waters (refer to Appendix A). EPA focused its analysis on the 57 major facilities identified. Seven of those facilities discharge directly to Indian reservation waters, and all seven are sewerage systems. Of the other 50 major facilities discharging upstream from Indian reservation waters, 9 are industrial facilities, and 41 are sewerage systems. EPA evaluated all 7 direct dischargers to Indian reservation waters and all 9 upstream industrial facilities and selected a sample of 10 upstream sewerage systems from which to extrapolate for purposes of estimating potential point source costs.
EPA evaluated compliance scenarios and associated costs for the sample facilities based on available information about the facilities, their treatment systems, and current effluent quality. EPA determined whether a facility would most likely achieve compliance through optimization, P2, and source control; additional effluent treatment; or alternative compliance mechanisms (such as WQS variances). P2 programs have a one-time cost component for development and a recurring annual cost component for implementation. WQS variances are represented solely by a one-time cost component for developing the supporting justifications for the purpose of this analysis. Additional effluent treatment has a capital cost component which can be annualized using an assumed discount rate over a period of years and a recurring annual cost for operation and maintenance. In some cases, available information did not clearly point to one compliance alternative. In such cases, EPA estimated a range of costs for compliance.
EPA extrapolated costs to the remaining major upstream sewerage systems from the sample based on facility flow. Exhibit ES-1 summarizes the estimated potential costs for major facilities by facility category.
Exhibit ES-1 Summary of Estimated Potential Costs (2020 $Millions) for Major Facilities
Facility Category
Total One-Time Costs
Total Annual Costs
(n = 20 yr; i = 3%)
Total Annual Costs
(n = 20 yr; i = 7%)
Low estimate
Facilities discharging to Indian reservation waters (7)
                                                                         $0.24 
                                                                         $0.15 
                                                                         $0.18 
Upstream industrial facilities (9)
                                                                         $0.12 
                                                                         $1.79 
                                                                         $2.20 
Sampled upstream sewerage systems (10)
                                                                         $2.37 
                                                                         $3.43 
                                                                         $4.18 
Extrapolated upstream sewerage systems (31)
                                                                         $3.38 
                                                                        $10.14 
                                                                        $12.38 
Total (low estimate)
                                                                         $6.10 
                                                                        $15.51 
                                                                        $18.94 
High estimate
Facilities discharging to Indian reservation waters (7)
                                                                         $0.41 
                                                                         $0.72 
                                                                         $0.80 
Upstream industrial facilities (9)
                                                                         $0.12 
                                                                         $2.23 
                                                                         $2.63 
Sampled upstream sewerage systems (10)
                                                                         $0.30 
                                                                        $11.77 
                                                                        $14.17 
Extrapolated upstream sewerage systems (31)
                                                                         $0.40 
                                                                        $15.81 
                                                                        $18.84 
Total (high estimate)
                                                                         $1.23 
                                                                        $30.54 
                                                                        $36.45 

Total One-Time Costs is the sum of P2 and WQS variance one-time costs. Total Annual Costs is the sum of annualized effluent treatment and annual P2 costs. Total One-Time Costs are larger in the low estimate summary than in the high estimate summary because one-time WQS variance costs are often used in lieu of annualized effluent treatment costs for facility-specific low estimates for certain pollutants. Detailed analyses for each evaluated facility are presented in Appendix A. Total cost estimates range from $15.51 million in annualized costs over 20 years at a 3 percent discount rate (with $6.1 million in one-time costs) to $30.54 in annualized costs over 20 years at a 3 percent discount rate (with $1.23 million in one-time costs). Using a discount rate of 7 percent over 20 years, total annualized costs range from $18.94 million (also with $6.1 million in one-time costs) to $36.45 million (also with $1.23 million in one-time costs).
Potential Water Quality Impairments
EPA's analysis of water quality data available for Indian reservation waters identified potential impairments of Indian reservation waters for 25 pollutants for either human health, aquatic life, or both types of economic analysis criteria. EPA identified 215 reaches that are potentially impaired for at least one pollutant, and 500 total potential impairments across all reaches and pollutants. 
Uncertainties in the Analysis 
There are a number of uncertainties in the analysis associated with data limitations, potential pollutant load reductions achievable, and the methods dischargers would use to comply with potential requirements and permit conditions that affect the estimated costs. 
For the economic analysis criteria, EPA used a conservative approach to estimate certain concentration criteria values (e.g., copper criteria derived from conservative dissolved organic carbon concentration assumptions to the biotic ligand model, selenium criteria assuming all waters are lentic, ammonia criteria assuming a water temperature of 25 degrees Celsius), which may differ from the approach that would be employed to establish numeric values for specific Tribes. However, some of the economic analysis criteria may be less stringent than site-specific criteria that could be derived using local water quality data (e.g., dissolved metals in areas with hardness lower than 100 milligrams per liter). Therefore, costs may be over- or under-estimated depending on the pollutant and approach.
EPA was unable to quantify and monetize benefits, which could potentially outweigh some or all of the costs. 
EPA relied on NPDES data for individual permits of major dischargers only and was unable to estimate costs associated with either general permits or individual permits for minor dischargers due to a lack of available data for these facilities.
Complete data were not readily available for all pollutants at all NPDES-permitted facilities and, when only limited data were available, they may not be representative of typical conditions. For example, for this analysis EPA was able to assemble information from final permit documents but not from permit applications. In addition, information on existing controls was not always available. Therefore, costs for point source dischargers may be over or under-estimated. 
The lack of available in-stream monitoring data for some water bodies and the use of a single set of economic analysis criteria instead of site-dependent economic analysis criteria prevent reliable estimation of impairment status of ambient conditions.
Assumptions made in the analysis when ambient data were not available (e.g., using a value equal to one-half the DL or zero if one-half of the DL exceeds the most stringent criteria) may lead to over- or under-estimating the need for additional NPDES permit limits and the associated costs for point source dischargers.
For point sources, it is uncertain whether any particular control option would guarantee meeting the economic analysis criteria. For example, the effluent reductions achievable through P2 activities and the level of controls needed are highly site-specific and cannot be accurately estimated without a detailed analysis of a given facility's service area and existing plant processes and operations. 
The costs of controls are likely facility-specific and may be higher or lower than shown. Thus, it is uncertain how much system improvements will cost without facility-specific source identification studies.
Introduction
The United States Environmental Protection Agency (EPA) is proposing to establish federal water quality standards (WQS) for Indian reservation waters that currently do not have WQS in effect under the Clean Water Act (CWA or the Act), with limited exceptions. Such WQS (referred to as baseline WQS) would establish human health and environmental objectives as the basis for CWA protections for these Indian reservation waters. This report is an economic analysis that provides estimates of the potential compliance actions and costs that may be associated with the proposed baseline WQS and identifies the potential benefits and beneficiaries of the proposed baseline WQS.
Background
Regulatory Background
The CWA sets the basic structure for regulating pollutant discharges into the waters of the United States. In the CWA, Congress established the national objective to "restore and maintain the chemical, physical, and biological integrity of the Nation's waters," and to achieve "wherever attainable, an interim goal of water quality which provides for the protection and propagation of fish, shellfish, and wildlife and for recreation in and on the water" (CWA sections 101(a) and 101(a)(2)).
The CWA establishes the basis for the current WQS regulation and program. CWA section 303 addresses the development of state and authorized Tribal WQS. WQS reflect the CWA national objectives for each water body. The core components of these standards are designated uses, water quality criteria, and antidegradation requirements. Designated uses establish the environmental objectives for a water body, while water quality criteria define the minimum conditions necessary to achieve those environmental objectives. The antidegradation requirements complement designated uses and criteria by providing a framework for maintaining and protecting water quality.
In 1987, Congress amended the CWA to add several provisions, including section 518(e) which allows the Administrator to treat an Indian Tribe in a similar manner as a state (TAS) for purposes of various CWA provisions, including section 303(c), provided that the Tribe meets certain eligibility criteria. In 1991, EPA issued a final rule to implement section 518(e) for the WQS program (40 CFR 131.8). The rule adopts the criteria contained in CWA section 518 that Tribes must meet to be eligible to administer a WQS program and establishes procedures for the EPA Regional Administrator to receive and make determinations on Tribal applications. The rule was re-interpreted in 2016 to streamline the application process for Tribes to obtain TAS. 
Although over 300 Tribes with Indian reservations could apply to administer their own WQS program under the CWA, only 84 Tribes have been found eligible to administer a WQS program (i.e., have obtained approval for treatment in a similar manner as a state, or TAS). EPA has approved WQS for 47 of these Tribes and has promulgated federal WQS for one Tribe (the Colville Reservation). 
As a result, 50 years after enactment of the CWA, over 80% of Indian reservations do not have this foundational protection for their waters as authorized by Congress in the CWA. Therefore, EPA is proposing to promulgate baseline WQS for Indian reservation waters that do not have CWA-effective WQS in place. The term "reservation" includes all lands formally designated as reservations by the United States, and lands held in trust by the United States for the benefit of Tribal governments ("Tribal trust lands") that may not be located within the boundaries of formal reservations. 
Having such baseline WQS, together with WQS already approved or promulgated by EPA, would ensure that all Tribes have access to full water quality protections for their reservations under the CWA. 
In EPA's proposed rule, the baseline WQS would apply to all Indian reservation waters of the United States except for: 
Indian reservation waters where EPA has approved TAS for the Tribe and the Tribe has adopted WQS that EPA has approved  -  currently the 47 Tribes mentioned above, plus any that EPA may approve in the future.
Indian reservation waters where EPA has promulgated other federal WQS for a Tribe  -  currently the Confederated Tribes of the Colville Reservation (see 40 CFR 131.35, finalized in 1989), plus any for which EPA promulgates other federal WQS in the future.
Indian reservation waters where a Tribe cannot adopt its own WQS because EPA has explicitly found that a state has jurisdiction to administer WQS for those waters  -  currently for 12 Tribes in four states, plus any Tribal waters for which state jurisdiction is granted in the future. 
Indian reservation waters where the Regional Administrator uses authority in the proposed rule to approve an additional exclusion in the future on a case-by-case basis in consultation with the affected Tribe.
Purpose and Scope of the Analysis
The purposes of this document are to estimate the costs that could arise as a result of promulgating baseline WQS and to identify the potential benefits and beneficiaries of the baseline WQS. The document also describes how the proposed WQS could benefit stakeholders (e.g., health, improved recreation opportunities). 
Water quality standards themselves do not impose costs on any entity. The purpose of the cost analysis is to identify, using available water quality and discharge data and information, the potential control actions and costs that publicly owned treatment works (POTWs) and industrial point source dischargers may incur as a result of implementing the baseline WQS. 
The proposed baseline WQS may impact dischargers to waters located within the boundaries of the Indian reservations themselves, as well as dischargers to waters of other jurisdictions shared with, or upstream from, the reservations. The proposed baseline WQS may result in new or more stringent water quality-based effluent limits (WQBELs) contained in the National Pollutant Discharge Elimination System (NPDES) permit for these facilities. The estimates of nationwide control costs in this analysis reflect the potential impacts on dischargers of such new or more stringent WQBELs.
Although the focus of the cost analysis is to estimate control costs for point sources, attaining the proposed baseline WQS would likely depend on additional actions such as nonpoint source controls. Nonpoint source controls, whether required through a nonpoint source program or implemented voluntarily, may lead to nonpoint sources incurring costs as an indirect result of the proposed baseline WQS. Conversely, implementing nonpoint source controls may relieve a portion of the estimated indirect burden on and cost to point sources within the same watershed. However, quantitative evaluation of the potential control needs beyond those addressed under the NPDES program is not possible given the limited available data. Thus, EPA identified the types of controls and unit costs that may be incurred for nonpoint sources but did not develop nationwide nonpoint source cost estimates.
Costs are anticipated to be accompanied by benefits resulting from the control actions. Economic impacts in the form of municipal and industrial expenditures financed through user fees and profits would be accompanied by increased employment, incomes, revenues, and profits to sectors supplying treatment technologies and services (which may be within or external to Tribal areas). The scope of this analysis is limited to qualitatively identifying and describing the potential benefits of promulgating baseline WQS for Indian reservation waters.
Report Organization 
This report is organized as follows:
Section 2: Applicability and Current Regulatory Framework  -  describes the lands and waters to which this rule applies and the current regulatory framework for these lands and waters.
Section 3: Derivation of Economic Analysis Criteria  -  describes the method EPA used to derive "economic analysis criteria" for the purpose of this analysis. EPA is not proposing the specific numeric criteria in this economic analysis as the WQS that would appear in a regulation. 
Section 4: Potential Benefits  -  provides a qualitative discussion of the benefits and beneficiaries of the proposed baseline WQS.
Section 5: Method for Estimating Potential Costs: Point Sources  -  describes the method for estimating point source control costs for potential revisions to NPDES permits to meet the economic analysis criteria.
Section 6: Method for Identifying Potential Impairments and Characterization of Nonpoint Sources  -  describes the method for identifying waters that may be impaired based on comparison of available monitoring data to the economic analysis criteria, and provides a characterization of potential nonpoint sources than that may affect water quality.
Section 7: Potential Control Costs  -  provides estimates of potential costs to comply with the proposed baseline WQS and discusses the uncertainties associated with the estimates. 
References  -  provides the references used in the analysis. 
The appendices provide detailed analyses and additional information:
Appendix A: provides data and information on individual sample facilities used to estimate point source costs.
Appendix B: describes pollution prevention programs and estimated costs.
Appendix C: provides details for various effluent treatment technologies, including estimated costs, where available.
Appendix D: provides additional information on pollutant impacts in support of the potential benefits evaluation in Section 4. 
Applicability and Current Regulatory Framework
This section describes the lands and waters to which the proposed baseline WQS would apply. It also describes the current regulatory framework under the CWA. The current regulatory framework serves as the economic baseline, which is a reference point that reflects the world without the proposed regulation and is the starting point for determining the potential benefits and costs of the proposed regulation.
Indian Reservations and Waters Subject to the Analysis
This economic analysis covers Indian reservation waters where the proposed baseline WQS would potentially apply, as described under Background above, with certain exceptions. Specifically, the economic analysis covers all Indian reservation waters with the following exclusions, per the proposed rule, and exceptions, for the purposes of the economic analysis:
Exclusion: Indian reservation waters where EPA has approved TAS for the Tribe and the Tribe has adopted WQS that EPA has approved  -  currently the 47 Tribes mentioned above. Exception: The economic analysis does not make any adjustments for future approvals. 
Exclusion: Indian reservation waters where EPA has promulgated other federal WQS for a Tribe  -  currently the Confederated Tribes of the Colville Reservation (see 40 CFR 131.35, finalized in 1989). Exception: The economic analysis does not make any adjustments for future such promulgations. 
Exclusion: Indian reservation waters where a Tribe cannot adopt its own WQS because EPA has explicitly found that a state has jurisdiction to administer WQS for those waters  -  currently for 12 Tribes in four states, plus any Tribal waters for which state jurisdiction is granted in the future. Exception: The economic analysis does not make any adjustments for future such jurisdictional findings. Additional exception: The economic analysis does not examine any Indian reservation lands in Oklahoma due to the lack of appropriate geospatial information. For example, for most Oklahoma Tribes the only lands potentially covered by the proposed baseline WQS would be checkerboarded Tribal trust lands and on-reservation Indian allotments for which EPA has no reliable geospatial information. 
Exclusion: Indian reservation waters where the Regional Administrator uses authority in the proposed rule to approve an additional exclusion in the future on a case-by-case basis in consultation with the affected Tribe. Exception: The economic analysis does not make any adjustments for such future actions.
Exhibit 2-1 provides a map of the Indian reservations with waters depicted in light and dark yellow that are represent the areas that would be affected by the proposed rule and are included in this analysis. 
Exhibit 2-1 Indian Reservations with Waters in Light and Dark Yellow 
Included in this Analysis

Current Regulatory Framework on these Lands/Waters
The current regulatory framework is the set of currently applicable requirements under the CWA without this proposed rule. These requirements include the following elements of the NPDES program:
Technology-based effluent limits (TBELs). These include secondary treatment standards for POTWs prior to discharge  -  including five-day biochemical oxygen demand (BOD5), total suspended solids (TSS) removal, percent removal of BOD5 and TSS, and pH  -  and best available treatment standards for industrial dischargers, including requirements established for their industry through EPA's effluent limitations and guidelines regulations (effluent guidelines), when available. TBELs are based on best professional judgement on a case-by-case basis in the absence of national guidelines.
WQBELs. These limits are established whenever a discharge causes or has the reasonable potential to cause or contribute to an excursion above any applicable CWA WQS. For example, even where there are currently no applicable WQS for a water body, WQBELs may be needed to comply with the applicable WQS of a downstream jurisdiction at the boundary of the reservation. 
Some Tribes may have adopted standards solely under Tribal law, and those standards may have guided EPA permit writers when setting effluent limits. In addition, some facilities may have effluent limits based on requirements in neighboring states. For purposes of this economic analysis, EPA assumed that all permitted facilities meet their current effluent limits or would be required to take the steps needed to meet those limits under the current regulatory framework. This means that the incremental cost to a point source considered in this analysis is the incremental cost of complying with WQBELs derived from the proposed baseline WQS. In other words, the analysis only represents costs to point source dischargers that may be imposed as a result of implementing the proposed rule and do not reflect any costs required under the current regulatory framework. Thus, the analysis assesses point source costs only when incremental changes are needed to comply with new or more stringent effluent limits derived from the proposed baseline WQS.
Derivation of Economic Analysis Criteria
EPA is proposing a national rule to establish baseline WQS to safeguard water quality for certain Indian reservation waters by ensuring that the core CWA framework to protect water quality is in place for these waters until such time as the Tribe applies for TAS to administer a WQS program and adopts its own Tribal WQS for EPA approval consistent with CWA section 303(c). EPA is proposing to establish the following WQS: designated uses consistent with the CWA protection and restoration goals for aquatic life and users of surface water, and a designated use that protects cultural and traditional uses; water quality criteria to protect those uses; an antidegradation policy with associated implementation procedures; and general WQS polices such as a mixing zone policy and compliance schedule authorizing provision. The antidegradation policy and other general WQS policies are not part of the economic analysis. 
EPA is proposing to promulgate narrative criteria with binding numeric translation procedures designed to protect the designated uses promulgated by this rule. The binding numeric translation procedures include the ability to rely on EPA's national CWA section 304(a) recommended water quality criteria to protect human health and aquatic life. The numeric values and their relevant assumptions identified in this document were developed solely for the purposes of this economic analysis. They are not the final criteria that would apply to Indian reservation waters and are referred to as "economic analysis criteria" for purposes of this document. EPA permit writers would follow the narrative requirements in deriving the specific limits in the permit.
The economic analysis criteria include EPA's national CWA section 304(a) recommended human health and aquatic life water quality criteria published pursuant to section 304(a) of the CWA, with exceptions discussed in Sections 3.1 and 3.2 below. Section 3.3 presents a list of pollutants and their criteria calculated and used in this analysis.
Overall Assumptions for Purposes of this Analysis
This section describes the general assumptions used for developing the economic analysis criteria. These assumptions apply to all geographic areas evaluated for this analysis. Regional-specific assumptions (e.g., Great Lakes area) and economic analysis criteria are provided in Sections 3.2 and 3.3, respectively. 
Applicable Designated Uses
For the purposes of this analysis, EPA made the following assumptions: 
All waters, including coastal environments, are assumed to have designated uses and water quality criteria for the protection of fish and shellfish harvesting for human consumption, and for the protection and propagation of aquatic life.
All Indian reservation waters are assumed to be designated for protection of cultural and traditional uses and rely on criteria developed to protect drinking water sources (excluding coastal saltwater environments).
All Indian reservation waters are assumed to be designated for primary contact recreation, which would rely on EPA's 2012 recreational water quality criteria. 
Aquatic Life Criteria
For purposes of this analysis, the economic analysis criteria are based on EPA's national CWA section 304(a) recommended aquatic life criteria available online, including most dissolved metals, except for a few pollutants discussed below.
Due to the high variability of temperature across the country, no single temperature was appropriate for a nationwide assessment, and EPA did not assess temperature as a pollutant. Similarly, nationwide values for total phosphorus and total nitrogen concentrations are not appropriate; therefore, EPA did not derive economic analysis criteria for nutrients. 
EPA did not derive economic analysis criteria for polychlorinated biphenyls (PCBs) and focused the analysis for this pollutant on human health criteria, which are much more stringent. An economic assessment of this pollutant was not conducted for aquatic life. 
For copper, EPA ran the Biotic Ligand Model (BLM) model. EPA assumed a neutral pH (pH = 7) across the country, which is reasonable for most regions given daily and seasonal fluctuations typically observed. The BLM model is not very sensitive to temperature, and EPA selected a temperature of 25 degrees Celsius (°C) as representative of a temperature applicable across the U.S. EPA calculated copper criteria based on a dissolved organic carbon (DOC) concentration of 2 milligrams per liter (mg/L). Finally, EPA used conservative values for all missing parameters by selecting the median of the tenth percentile distributions across Level III eco-regions for all missing parameters (EPA, 2016a). 
Other pollutant exceptions are listed below: 
For selenium, EPA used the final 2016 criteria, and made the conservative assumption that all freshwaters are lentic. 
EPA calculated ammonia economic analysis criteria for both freshwater and saltwater assuming a neutral pH of 7 across all waters and a conservative temperature of 25 °C.
For dissolved oxygen, EPA identified a minimum value of 5 mg/L (i.e., dissolved oxygen measurements below 5 mg/L indicate a water quality issue).
Human Health Criteria
For purposes of this analysis, as with the aquatic life criteria, the economic analysis criteria are based on EPA's national CWA section 304(a) recommended human health criteria. EPA calculated most economic analysis criteria for the protection of human health based on consumption of water and organisms (e.g., fish), and consumption of organisms only, using EPA's 2015 human health criteria updates or a combination of the most recent updated equation for a given pollutant and the 2015 updated assumptions. Updates to federal criteria assumptions published in 2015 included a body weight of 80 kilograms (kg) per adult, a drinking water intake of 2.4 liters (L) per person per day, and revised fish consumption rates (FCRs) by trophic level.
To reflect potentially greater fish consumption among Tribal members than by the general population, EPA also used an FCR of 142.4 grams per day (gpd) (the sum for trophic levels 2, 3, and 4), which is higher than the 21.3 gpd FCR used to derive the federal criteria. 
Most human health criteria are calculated based on the pollutant reference dose (for non-carcinogens) or cancer potency factor (for carcinogens), bioconcentration factor, and FCR as follows (EPA, 1980), with the inputs described above:
AWQC (non‐carcinogen) = (RfD xRSC) x BWDI+(FIxBAF)
AWQC (carcinogen)=10-6q1*xBWDI+(FIxBAF)
Where:
AWQC	= 	ambient water quality criterion (mg/L)
BW	= 	human body weight (kg)
RfD 	= 	reference dose based on noncancer human health effects (mg/kg BW-day)
RSC 	= 	relative source contribution (%)
DI	= 	drinking water intake (L/day)
FI	= 	human fish intake (kg fish/day)
BAF 	= 	bioaccumulation factor (L/kg fish)
q1*	= 	cancer potency factor (kg BW-day/mg).
In 2001, EPA published a revised methylmercury criterion based on the concentration of methylmercury in fish tissue. For the purpose of this economic analysis, EPA calculated economic analysis criteria for methylmercury using the following equation (EPA, 2001a):
TRC=BWx(RfD-RSC)i=24FIi
Where:
TRC	= 	tissue residual concentration in methylmercury (mg /kg fish)
FIi 	= 	human fish consumption of trophic level i (kg fish/day)
RSC	= 	relative source contribution in methylmercury (mg/kg/BW-day).
For pathogens, and pathogen indicators, EPA used the 2012 recommended recreation geometric mean criterion for E. coli for the point source analysis and statistical threshold values for E. coli and Enterococci for analysis of ambient water quality and potential impairments (EPA, 2012a). 
For pollutants for which federal criteria are based on drinking water regulations (e.g., maximum contaminant level (MCL)), or are not based on FCRs or toxic effects, EPA used the federal criteria as listed on its current National Recommended Human Health Criteria table (available online at: https://www.epa.gov/wqc/national-recommended-water-quality-criteria-human-health-criteria-table). These pollutants include: asbestos, barium, copper, manganese, nitrates, pH, and dissolved solids and salinity. 
Finally, EPA did not evaluate the following three pollutants for protection of human health in this economic analysis because translation of these parameters to economic analysis criteria raises specific technical issues that require additional considerations beyond the scope of this economic analysis:
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD; Dioxin),
Arsenic, and
Thallium.
Geographic-Specific Assumptions
Fish Consumption Rates
Using national results from a food survey conducted by the United States Department of Agriculture, EPA identified 142.4 gpd as an approximation of average fish consumption for subsistence fishers in its methodology for deriving human health criteria (EPA, 2000). Therefore, for purposes of this economic analysis, EPA is assuming an FCR of 142.4 gpd. The assumption EPA made for FCR affects only economic analysis criteria for human health.
Great Lakes Initiative
In March of 1995, EPA published Water Quality Guidance for the Great Lakes Watershed, commonly known as the Great Lakes Initiative (GLI), which provides detailed methodologies to develop criteria for Great Lakes waters. Great Lakes states and Tribes are required to use the water quality criteria, methodologies, policies, and procedures in the GLI, so EPA calculated criteria specific to the Great Lakes region for purposes of this analysis using these specific inputs. However, to ensure economic analysis criteria are based on the latest science, in its GLI calculations for purposes of this analysis, EPA used the updated the body weight of 80 kg, daily drinking water intake of 2.4 L/day, and FIs by trophic level presented in Exhibit 3-1; as well as an FCR of 142.4 gpd.
EPA recalculated the 18 numeric human health criteria defined by GLI formulas, compared the results to the economic analysis criteria calculated for the rest of the country with an FCR of 142.4, and used the more stringent of the two economic analysis criteria. For the remaining pollutants not covered by the GLI, EPA used the same economic analysis criteria as were calculated for the rest of the country with an FCR of 142.4 gpd. 
EPA also recalculated the 15 numeric aquatic life criteria defined by GLI formulas and compared them to the economic analysis aquatic life criteria calculated for the rest of the country. For consistency across the two sets of economic analysis criteria, EPA assumed a hardness of 100 mg/L for calculating dissolved metal criteria. EPA compared the economic analysis aquatic life criteria for the GLI and the rest of the country and selected the more stringent of the two for application in the Great Lakes region for the purpose of this cost analysis. All aquatic life GLI economic analysis criteria were either identical or less stringent than the economic analysis criteria across the rest of the country, so for purposes of this analysis, EPA used the same aquatic life economic analysis criteria regardless of location. Section 3.3 presents a list of pollutants and their economic analysis aquatic life criteria evaluated in this analysis.
Economic Analysis Criteria
This section presents the economic analysis criteria used for purposes of this analysis based on the assumptions described above, as well as DLs for these economic analysis criteria, which represent the minimum level to which dischargers may need to measure each pollutant. 
EPA identified the lowest available DL for readily available methods approved in the Code of Federal regulations (CFR) under 40 CFR Part 136 Guidelines Establishing Test Procedures for the Analysis of Pollutants. The DL is the minimum concentration that can be measured and reported with 99% confidence that the concentration is greater than zero. When identifying control costs, EPA assumed that if a calculated WQBEL for a parameter is less than the DL, the discharger may have to ensure that it controls the discharge of that parameter to a level where it is not detected in the effluent.
EPA searched the National Environmental Methods Index (NEMI) database for DLs listed under 40 CFR 136 approved methods for all human health and aquatic life pollutants. When available, EPA selected the lowest DL listed. When not available, EPA searched 40 CFR 136 to identify approved methods for a contaminant, reviewed readily available methods, and selected the lowest DL for the reviewed methods as the DL for that pollutant. For searches outside the NEMI database, EPA focused primarily on EPA approved methods when available.
Exhibit 3-1 lists the aquatic life economic analysis criteria derived for purposes of this economic analysis, as well as the lowest DLs for these economic analysis criteria, when available through the methodology described above. The exhibit provides chronic and acute criteria for both freshwater and saltwater environments, expressed in micrograms per liter (ug/L) unless specified otherwise. Blank DLs identify DLs that could not be determined from either the NEMI database or the methods listed under 40 CFR 136. Blanks in the economic criteria columns identify economic analysis criteria that were not evaluated as part of this analysis.
Exhibit 3-1 Detection Limits and Aquatic Life Economic Analysis Criteria (ug/L)
Pollutant 
DL 
Freshwater acute criterion
Freshwater chronic criterion
Saltwater acute criterion
Saltwater chronic criterion
4,4'- Dichlorodiphenyltrichloroethane (DDT)
                                     0.012
                                      1.1
                                     0.001
                                     0.13
                                     0.001
Acrolein
                                      0.7
                                       3
                                       3
                                       
                                       
Aldrin
                                     0.004
                                       3
                                       
                                      1.3
                                       
Alkalinity
                                     10000
                                       
                                     20000
                                       
                                       
alpha-Endosulfan
                                     0.014
                                     0.22
                                     0.056
                                     0.034
                                    0.0087
Aluminum (pH 6.5-9)
                                       
                                      750
                                      87
                                       
                                       
Ammonia
                                      10
                                     11000
                                     1400
                                     44000
                                     6600
Arsenic
                                      0.4
                                      340
                                      150
                                      69
                                      36
beta-Endosulfan
                                     0.004
                                     0.22
                                     0.056
                                     0.034
                                    0.0087
Carbaryl
                                     0.22
                                      2.1
                                      2.1
                                      1.6
                                       
Cadmium
                                     0.05
                                      1.8
                                     0.72
                                      33
                                      7.9
Chlordane
                                     0.014
                                      2.4
                                    0.0043
                                     0.09
                                     0.004
Chloride
                                       4
                                    860000
                                    230000
                                       
                                       
Chlorine
                                      10
                                      19
                                      11
                                      13
                                      7.5
Chlorpyrifos
                                     0.004
                                     0.083
                                     0.041
                                     0.011
                                    0.0056
Chromium (III)
                                       
                                      570
                                      74
                                       
                                       
Chromium (VI)
                                      0.3
                                      16
                                      11
                                     1100
                                      50
Copper*
                                      0.5
                                      4.4
                                      2.7
                                      4.8
                                      3.1
Cyanide
                                       5
                                      22
                                      5.2
                                       1
                                       1
Demeton
                                     0.25
                                       
                                      0.1
                                       
                                      0.1
Diazinon
                                     0.012
                                     0.17
                                     0.17
                                     0.82
                                     0.82
Dieldrin
                                     0.002
                                     0.24
                                     0.056
                                     0.71
                                    0.0019
Endrin
                                     0.002
                                     0.086
                                     0.036
                                     0.037
                                    0.0023
gamma-benzene hexachloride (BHC) (Lindane)
                                     0.004
                                     0.95
                                       
                                     0.16
                                       
Guthion
                                     0.009
                                       
                                     0.01
                                       
                                     0.01
Heptachlor
                                    0.0015
                                     0.52
                                    0.0038
                                     0.053
                                    0.0036
Heptachlor Epoxide
                                     0.001
                                     0.52
                                    0.0038
                                     0.053
                                    0.0036
Iron
                                       1
                                       
                                     1000
                                       
                                       
Lead
                                      0.6
                                      65
                                      2.5
                                      210
                                      8.1
Malathion
                                     0.011
                                       
                                      0.1
                                       
                                      0.1
Methylmercury
                                       
                                      1.4
                                     0.77
                                      1.8
                                     0.94
Methoxychlor
                                     0.02
                                       
                                     0.03
                                       
                                     0.03
Mirex
                                     0.015
                                       
                                     0.001
                                       
                                     0.001
Nickel
                                      0.5
                                      470
                                      52
                                      74
                                      8.2
Nonylphenol
                                       
                                      28
                                      6.6
                                       7
                                      1.7
Oxygen, Dissolved 
                                       
                                       5
                                       5
                                       5
                                       5
Parathion
                                     0.01
                                     0.065
                                     0.013
                                       
                                       
Pentachlorophenol
                                     0.014
                                      19
                                      15
                                      13
                                      7.9
Selenium
                                      0.6
                                       
                                      1.5
                                      290
                                      71
Silver
                                      0.1
                                      3.2
                                       
                                      1.9
                                       
Sulfide-Hydrogen Sulfide
                                       
                                       
                                       2
                                       
                                       2
Toxaphene
                                     0.24
                                     0.73
                                    0.0002
                                     0.21
                                    0.0002
Tributyltin (TBT)
                                       
                                     0.46
                                     0.072
                                     0.42
                                    0.0074
Zinc
                                     0.05
                                      120
                                      120
                                      90
                                      81
pH (no units)
                                       
                                       
                                   6.5  -  9
                                       
                                  6.5  -  8.5
Note: 
* Freshwater copper criteria listed in this exhibit assume a DOC of 2 mg/L. EPA also ran the BLM model with a DOC of 8 mg/L, which resulted in a freshwater acute criterion of 17 ug/L and a freshwater chronic criterion of 11 ug/L. EPA selected the most conservative economic analysis criteria for purposes of this analysis. 
Exhibit 3-2 lists human health economic analysis criteria calculated for purposes of this economic analysis. For each set of assumptions EPA provides in this exhibit the human health economic analysis criteria assuming the consumption of drinking water and organisms (i.e., fish), and the consumption of organisms only. The exhibit also lists the lowest DLs for these economic analysis criteria, when available through the methodology described above. Blanks identify DLs that could not be determined from either the NEMI database or the methods listed under 40 CFR 136. All values in the exhibit are expressed in ug/L unless specified otherwise. 
Exhibit 3-2 Detection Limits and Human Health Economic Analysis Criteria (expressed in ug/L, unless specified otherwise)

Tribal
GLI
Pollutant
DL
Water + Organism
Organism Only
Water + Organism
Organism Only
Bis(2-Chloro-1-Methylethyl) Ether 
                                      0.8
                                      200
                                      500
                                      200
                                      500
1,1-Dichloroethylene
                                     0.01
                                      300
                                     2000
                                      300
                                     2000
1,1,1-Trichloroethane
                                     0.005
                                     9000
                                     30000
                                     9000
                                     30000
1,1,2-Trichloroethane
                                     0.01
                                     0.41
                                      1.3
                                     0.41
                                      1.3
1,1,2,2-Tetrachloroethane
                                     0.03
                                      0.1
                                      0.4
                                      0.1
                                      0.4
1,2-Dichlorobenzene
                                     0.02
                                      400
                                      500
                                      400
                                      500
1,2-Dichloroethane
                                     0.02
                                      9.1
                                      97
                                      9.1
                                      97
1,2-Dichloropropane
                                     0.01
                                     0.77
                                      4.6
                                     0.77
                                      4.6
1,2-Diphenylhydrazine
                                      20
                                     0.02
                                     0.03
                                     0.02
                                     0.03
1,2-Trans-Dichloroethylene
                                     0.01
                                      100
                                      600
                                      100
                                      600
1,2,4-Trichlorobenzene
                                     0.02
                                     0.011
                                     0.011
                                     0.011
                                     0.011
1,2,4,5-Tetrachlorobenzene
                                       
                                     0.004
                                     0.004
                                     0.004
                                     0.004
1,3-Dichlorobenzene
                                     0.01
                                       2
                                       2
                                       2
                                       2
1,3-Dichloropropene
                                       
                                     0.24
                                      1.8
                                     0.24
                                      1.8
1,4-Dichlorobenzene
                                     0.01
                                      100
                                      100
                                      100
                                      100
2-Chloronaphthalene
                                     0.94
                                      200
                                      200
                                      200
                                      200
2-Chlorophenol
                                     0.31
                                      30
                                      100
                                      30
                                      100
2-Methyl-4,6-Dinitrophenol
                                      16
                                       1
                                       4
                                       1
                                       4
2,4-Dichlorophenol
                                     0.027
                                       6
                                       9
                                       6
                                       9
2,4-Dimethylphenol
                                     0.32
                                      100
                                      400
                                      100
                                      400
2,4-Dinitrophenol
                                     0.31
                                      10
                                      50
                                      10
                                      50
2,4-Dinitrotoluene
                                     0.02
                                     0.042
                                     0.25
                                     0.042
                                     0.25
2,4,5-Trichlorophenol
                                      0.2
                                      80
                                      90
                                      80
                                      90
2,4,6-Trichlorophenol
                                     0.046
                                     0.37
                                     0.42
                                     0.37
                                     0.42
3-Methyl-4-Chlorophenol
                                     0.36
                                      200
                                      400
                                      200
                                      400
3,3'-Dichlorobenzidine
                                     0.13
                                     0.017
                                     0.022
                                     0.017
                                     0.022
4,4'-DDD
                                       
                                   0.000019
                                   0.000019
                                   0.000019
                                   0.000019
4,4'-DDE
                                       
                                   0.0000026
                                   0.0000026
                                   0.0000026
                                   0.0000026
4,4'-DDT
                                     0.012
                                   0.000004
                                   0.000004
                                   0.000004
                                   0.000004
Acenaphthene
                                      1.8
                                      10
                                      10
                                      10
                                      10
Acrolein
                                      0.7
                                       3
                                      60
                                       3
                                      60
Acrylonitrile
                                      0.5
                                     0.058
                                       1
                                     0.058
                                       1
Aldrin
                                     0.004
                                  0.00000012
                                  0.00000012
                                  0.00000012
                                  0.00000012
alpha-BHC
                                       0
                                   0.000058
                                   0.000058
                                   0.000058
                                   0.000058
alpha-Endosulfan
                                     0.014
                                       4
                                       4
                                       4
                                       4
Anthracene
                                     0.66
                                      50
                                      60
                                      50
                                      60
Antimony
                                      0.4
                                       5
                                      90
                                       5
                                      90
Asbestos
                                       
                                    7000000
                                       
                                    7000000
                                       
Barium
                                      0.8
                                     1000
                                       
                                     1000
                                       
Benzene- Upper CSF
                                     0.01
                                     0.48
                                      2.4
                                     0.48
                                      2.4
Benzidine
                                     0.08
                                    0.00013
                                    0.0016
                                    0.00013
                                    0.0016
Benzo(a) Anthracene
                                     0.01
                                    0.0002
                                    0.0002
                                    0.0002
                                    0.0002
Benzo(a) Pyrene
                                     0.016
                                    0.00002
                                    0.00002
                                    0.00002
                                    0.00002
Benzo(b) Fluoranthene
                                     0.018
                                    0.0002
                                    0.0002
                                    0.0002
                                    0.0002
Benzo(k) Fluoranthene
                                     0.017
                                     0.002
                                     0.002
                                     0.002
                                     0.002
beta-BHC (beta-HCH)
                                       
                                    0.0019
                                    0.0021
                                    0.0019
                                    0.0021
beta-Endosulfan
                                     0.004
                                       6
                                       6
                                       6
                                       6
Bis(2-Chloroethyl) Ether
                                      0.3
                                     0.028
                                     0.33
                                     0.028
                                     0.33
Bis(2-Ethylhexyl) Phthalate
                                     0.46
                                     0.055
                                     0.057
                                     0.055
                                     0.057
Bis(Chlormethyl) Ether
                                       
                                    0.00014
                                    0.0026
                                    0.00014
                                    0.0026
Bromoform
                                     0.004
                                      5.2
                                      18
                                      5.2
                                      18
Butylbenzyl Phthalate
                                     0.34
                                     0.02
                                     0.02
                                     0.02
                                     0.02
Carbon Tetrachloride
                                     0.002
                                      0.3
                                      0.7
                                      0.3
                                      0.7
Chlordane
                                     0.014
                                   0.000047
                                   0.000047
                                    0.00003
                                    0.00003
Chlorobenzene
                                     0.01
                                      60
                                      100
                                      60
                                      100
Chlorodibromomethane
                                     0.001
                                     0.66
                                      3.1
                                     0.66
                                      3.1
Chloroform
                                     0.01
                                      60
                                      300
                                      60
                                      300
Chlorophenoxy Herbicide (2,4-D)
                                      1.2
                                      790
                                     1800
                                      790
                                     1800
Chlorophenoxy Herbicide (2,4,5-TP) [Silvex]
                                     0.17
                                      50
                                      60
                                      50
                                      60
Chrysene
                                     0.15
                                     0.02
                                     0.02
                                     0.02
                                     0.02
Copper
                                      0.5
                                     1300
                                       
                                     1300
                                       
Cyanide
                                       5
                                       4
                                      70
                                       4
                                      70
Di-n-Butyl Phthalate
                                     0.36
                                       4
                                       4
                                       4
                                       4
Dibenzo(a,h) Anthracene
                                     0.03
                                    0.00002
                                    0.00002
                                    0.00002
                                    0.00002
Dichlorobromomethane
                                     0.003
                                     0.79
                                       4
                                     0.79
                                       4
Dieldrin
                                     0.002
                                  0.00000019
                                  0.00000019
                                  0.00000019
                                  0.00000019
Diethyl Phthalate
                                     0.49
                                      100
                                      100
                                      100
                                      100
Dimethyl Phthalate
                                     0.29
                                      300
                                      300
                                      300
                                      300
Dinitrophenois
                                       
                                      10
                                      100
                                      10
                                      100
Endosulfan Sulfate
                                     0.066
                                       5
                                       6
                                       5
                                       6
Endrin
                                     0.002
                                     0.005
                                     0.005
                                     0.005
                                     0.005
Endrin Aldehyde
                                     0.023
                                      0.2
                                      0.2
                                      0.2
                                      0.2
Ethylbenzene
                                     0.01
                                      17
                                      19
                                      17
                                      19
Fluoranthene
                                     0.21
                                       3
                                       3
                                       3
                                       3
Fluorene
                                     0.21
                                      10
                                      10
                                      10
                                      10
Gamma-BHC (HCH); Lindane
                                     0.004
                                     0.66
                                     0.66
                                     0.06
                                     0.06
Heptachlor
                                    0.0015
                                  0.00000088
                                  0.00000088
                                  0.00000088
                                  0.00000088
Heptachlor Epoxide
                                     0.001
                                   0.0000048
                                   0.0000048
                                   0.0000048
                                   0.0000048
Hexachlorobenzene
                                     0.001
                                   0.000012
                                   0.000012
                                   0.000012
                                   0.000012
Hexachlorobutadiene
                                     0.34
                                     0.001
                                     0.001
                                     0.001
                                     0.001
Hexachlorocyclohexane (HCH)  -  Technical
                                       
                                    0.0014
                                    0.0015
                                    0.0014
                                    0.0015
Hexachlorocyclopentadiene
                                     0.004
                                      0.6
                                      0.6
                                      0.6
                                      0.6
Hexachloroethane
                                     0.03
                                     0.02
                                     0.02
                                     0.02
                                     0.02
Indeno(1,2,3-cd) Pyrene
                                     0.04
                                    0.0002
                                    0.0002
                                    0.0002
                                    0.0002
Isophorone
                                      2.2
                                      31
                                      280
                                      31
                                      280
Manganese
                                      0.1
                                      50
                                      100
                                      50
                                      100
Methoxychlor
                                     0.02
                                     0.003
                                     0.003
                                     0.003
                                     0.003
Methyl Bromide
                                      0.1
                                      100
                                     2000
                                      100
                                     2000
Methylene Chloride
                                     0.02
                                      20
                                      200
                                      20
                                      200
Methylmercury
                                       
                                       
                                     0.04
                                       
                                     0.04
N-Nitrosodi-n-Propylamine
                                     0.46
                                    0.0045
                                     0.071
                                    0.0045
                                     0.071
N-Nitrosodimethylamine
                                     0.15
                                    0.00065
                                     0.42
                                    0.00065
                                     0.42
N-Nitrosodiphenylamine
                                     0.81
                                     0.75
                                     0.84
                                     0.75
                                     0.84
Nickel
                                      0.5
                                      180
                                      240
                                      180
                                      240
Nitrates
                                       2
                                     10000
                                       
                                     10000
                                       
Nitrobenzene
                                     0.015
                                      10
                                      80
                                      10
                                      80
Nitrosamines
                                       
                                    0.00076
                                     0.065
                                    0.00076
                                     0.065
Nitrosodibutylamine
                                       
                                    0.0051
                                     0.031
                                    0.0051
                                     0.031
Nitrosodoiethylamine 
                                       
                                    0.00076
                                     0.065
                                    0.00076
                                     0.065
Nitrosopyrrolidine
                                       
                                     0.016
                                      4.8
                                     0.016
                                      4.8
Pathogens and Pathogen indicators (cfu/100 mL)
                                       
                                      100
                                      100
                                      100
                                      100
Pentachlorobenzene
                                       
                                     0.02
                                     0.02
                                     0.02
                                     0.02
Pentachlorophenol (PCP)
                                     0.014
                                     0.005
                                     0.005
                                     0.005
                                     0.005
Phenol
                                     0.14
                                     4000
                                     40000
                                     4000
                                     40000
PCBs
                                     0.028
                                   0.000009
                                   0.000009
                                  0.00000047
                                  0.00000047
Pyrene
                                     0.27
                                       4
                                       4
                                       4
                                       4
Selenium
                                      0.6
                                      130
                                      590
                                      130
                                      590
Solids Dissolved and Salinity
                                       
                                    250000
                                       
                                    250000
                                       
Tetrachloroethylene
                                     0.002
                                      3.4
                                      4.3
                                      3.4
                                      4.3
Toluene
                                     0.01
                                      35
                                      78
                                      35
                                      78
Toxaphene
                                     0.24
                                    0.00011
                                    0.00011
                                   0.0000082
                                   0.0000082
Trichloroethylene
                                     0.002
                                      0.4
                                       1
                                      0.4
                                       1
Vinyl Chloride
                                     0.02
                                     0.02
                                     0.24
                                     0.02
                                     0.24
Zinc
                                     0.05
                                     2600
                                     3600
                                     2600
                                     3600
Note: 
cfu = colony-forming units
Economic analysis criteria for pathogens and pathogen indicators such as E. coli and Enterococci are not dependent on an FCR. To estimate costs associated with these pollutants, EPA used the 2012 Recreational Water Quality Criteria (EPA, 2012a), with estimated illness rates of 32/1,000. For evaluation of NPDES dischargers, EPA used the geometric mean concentration of 100 colony-forming units (cfu)/100 mL for E. coli as a pathogen indicator. For surface water quality and impairment purposes, EPA used the statistical threshold values of 320 cfu/100 mL for E. coli and 110 cfu/100 mL for Enterococci. 
Potential Benefits
Promulgating baseline WQS for Indian reservation waters would promote the implementation of pollution control measures and best practices to help improve water quality and prevent future degradation of Indian reservation waters as well as potentially providing positive water quality benefits to waters in adjacent jurisdictions. Improved water quality in Indian reservation waters will benefit Tribes as well as anyone who recreates on Indian reservation waters or values environmental quality regardless of their current or anticipated uses of Indian reservation waters.
Water quality improvements on Indian reservations are particularly important to Tribal communities because natural resources are often integral to the Tribes' subsistence, culture, traditions, and daily life. Fish and shellfish harvesting have been a mainstay of many Indian Tribes for thousands of years. Tribal members harvest a variety of finfish species as well as clams, crab, oysters, shrimp, and many other species for commercial and ceremonial/subsistence use (Noble et al., 2016). Ceremonial and subsistence harvests of fish and shellfish can play a central role in daily nutrition and Tribal gatherings. The distinctive beauty, story, art, and culture of reservations also attract millions of visitors from around the world, generating billions of dollars in revenue each year and creating tens of thousands of jobs (American Indian and Alaska Native Tourism Association, 2018).
For Tribes without TAS authority to administer a WQS program under the CWA, protecting water quality by relying on federally promulgated baseline WQS will allow continued uses of Indian reservation waters, including instream use (e.g., fishing and fish consumption, recreation, cultural activities, aesthetic enjoyment), off-stream uses (e.g., drinking water), and nonuse benefits (e.g., preservation of natural ecosystems and cultural heritage; EPA, 2004). Although implementation of baseline WQS is likely to yield significant benefits to Tribal members, estimating the dollar value of these improvements to Tribal members may not be feasible recognizing the difficulty often expressed by Tribes to place a monetary value on ecosystem services, given the belief that these resources are sacred and beyond any earthly value. Estimating the value of water quality improvements to visitors of Indian reservations is also challenging due to the paucity of site-specific visitation, use (e.g., recreational fishing) and valuation data. Therefore, EPA assessed these benefits qualitatively, as described in the remainder of this section.
Human Health Benefits
Individuals are potentially exposed to pollutants present in Indian reservation waters via the consumption of contaminated fish or during recreational or ceremonial uses of surface waters. Populations served by drinking water utilities located downstream from contaminated Indian reservation waters may also be exposed to toxic pollutants via contaminated drinking water in cases of imperfect contaminant detection or treatment. Many of these pollutants may increase risks to human health. Toxic bioaccumulative pollutants are of particular concern because they do not volatilize or biodegrade; can be toxic to plants, invertebrates and fish; adsorb to sediments; and bio-concentrate in fish tissues (EPA, 2003). 
As described in Section 6.2, existing water quality data show that Indian reservation waters may be impaired for 12 parameters based on the human health economic analysis criteria enumerated in Section 3.3, including one known carcinogen (nickel). Exhibit 4-1 summarizes the human health effects of the pollutants with human health economic analysis criteria impairments. EPA's review of available monitoring data showed potential impairments in 136 Indian reservation stream reaches for at least one human health toxicant. Appendix D provides the full list of contaminants reviewed by EPA and their associated human health effects.
Exhibit 4-1 Human Health Effects Associated with Pollutants with Potential Impairments based on Economic Analysis Criteria
Human Health Effects
Number of Pollutants with Potential Impairments
Number of Waterbodies with Potential Impairments
Gastrointestinal
                                                                              7
                                                                             93
Respiratory
                                                                              5
                                                                             60
Cardiovascular
                                                                              5
                                                                             60
Neurological
                                                                              4
                                                                             59
Reproductive
                                                                              4
                                                                             59
Hematological
                                                                              4
                                                                             76
Hepatic
                                                                              3
                                                                              3
Developmental
                                                                              3
                                                                              3
Immunological
                                                                              3
                                                                              3
Endocrine
                                                                              3
                                                                             20
Renal
                                                                              2
                                                                              2
Dermal
                                                                              2
                                                                             19
Ocular
                                                                              2
                                                                              2

EPA sets the proposed standards at levels that are protective of human health during exposure through ingestion of aquatic organisms and ingestion of water and aquatic organisms. Accordingly, reducing the frequency at which human health-based economic analysis criteria are exceeded should translate into reduced health risk. The most important benefits stem from reduced risk of illness associated with the consumption of fish, shellfish, and other aquatic organisms that are taken from Indian reservation waters or reduced exposure to contaminated waters during recreation activities. The following subsections provide more detail on the types of human health benefits expected from promulgating baseline WQS for Indian reservation waters.
Reduced Health Risk from Fish, Shellfish, and Aquatic Plant Consumption
Aquatic biological resources (e.g., fish, shellfish) are integral to the Tribes' subsistence, spirituality, culture, and daily life. Tribal members and citizens consume fish, mussels, crustaceans, amphibians, frogs, turtles, and waterfowl as food. Several studies indicate that the daily fish intake of Tribal members is higher than that of the general population (Chan et al., 1997; CRITFC, 1994; Fitzgerald et al., 1998), making Tribal members particularly susceptible to adverse health effects from consuming contaminated fish tissue. For this analysis, EPA identified 142.4 gpd as an approximation of average fish consumption for subsistence fishers compared to 21.3 gpd for the general population (Section 3.2.1). Therefore, Tribal members who consume fish caught in Indian reservation waters are the primary beneficiaries of water quality improvements in Indian reservation waters. Non-Tribal recreational anglers who fish in Indian reservation waters and consume their catch may also benefit from reduced contamination of fish tissue.
Tribes also have a history of harvesting aquatic plants such as wild rice, Cattails and Wapato for consumption as food while aquatic plants such as Rat-tail, Stinkweed, Bitterroot, and Labrador Tea are used for medicinal purposes (Grijalva, 2020). Improved and protected water quality would reduce the risk of exposure from ingesting the aquatic plants, promote unobstructed growth of the plants, and protect additional cultural uses (e.g., using reeds, sedges, and rushes for basket-weaving, nets, and cordage).
Reduced Exposure to Carcinogens
Examples of health risks from exposure to carcinogens found in Indian reservation waters include skin, lung, liver, kidney, and bladder cancer, and leukemia. Nickel was found at levels exceeding the economic analysis criterion and is linked to lung and nasal cancers. Implementing WQS for Indian reservation waters may lead to a decrease in carcinogen concentrations in fish and shellfish tissue and, as a result, reduce cancer risk to Tribal members and recreational anglers who consume fish, shellfish, and other crustaceans caught in Indian reservation waters.
Reduced Exposure to Non-carcinogenic Human Health Toxicants
Tribal members and recreational anglers consuming fish caught in Indian reservation waters are also at risk of developing other health problems. Adverse health effects from exposure to non-carcinogenic toxic pollutants include neurological, systemic, reproductive, immunological, or circulatory problems. Examples of pollutants posing non-cancer health risks include metals (e.g., aluminum, copper, cyanide, silver, and zinc) and toxic organic pollutants. 
Individuals exposed to elevated levels of zinc may experience a range of adverse health effects. Possible symptoms of exposure to high levels of zinc in food and water may include abdominal cramps, vomiting, nausea, and general gastric irritation (EPA, 2005). Implementing WQS health toxicants in Indian reservation waters would reduce ambient pollutant concentrations in the Indian reservation stream reaches currently exceeding the economic analysis criterion and, as a result, reduce human health risk from exposure to contaminated fish and aquatic organisms.
Benefits from Improved Water Quality in Drinking Water Sources
Pollutants found in Indian reservation waters may affect the quality of water used for public drinking supplies. Public drinking water supplies are subject to legally enforceable MCLs established by EPA (EPA, 2012b). As the term implies, an MCL for drinking water specifies the highest level of a contaminant that is allowed in drinking water. The MCL is related to the MCL Goal (MCLG), which is the level of a contaminant in drinking water below which there is no known or expected risk to human health. EPA sets the MCL as close to the MCLG as possible, with consideration for the best available treatment technologies and costs. Pursuant to MCLs, public drinking water supplies are already treated for pollutants that pose human health risks. However, detection and treatment of the pollutants is imperfect, as evidenced by reported MCL violations for inorganic and other contaminants at community water systems (EPA, 2013; GAO, 2011). 
Drinking water systems that currently draw water from Indian reservation waters could benefit from implementation of the proposed baseline WQS. One potential benefit is forgone public water system treatment costs from improvements in upstream water quality as a result of implementing baseline WQS. For example, water systems may be able to forgo treatment (and the associated costs which may include capital and operation and maintenance (O&M) costs) for chemicals with established MCLs if upstream controls prevent the contaminant from occurring within the water system at levels/frequency that would otherwise require treatment. However, EPA has not assessed locations of drinking water intakes along Indian reservation waters and so cannot quantify the extent of these benefits. 
Reduced Risk of Gastrointestinal Illnesses from Recreation
Recreational activities such as swimming, wading, water-skiing, skin and scuba diving, surfing, and whitewater activities involve frequent and prolonged water contact, during which ingestion of water is reasonably possible. Tribal members and participants in water-based recreation on Indian reservations may become exposed to waters contaminated with enteric pathogens, such as fecal bacteria and viruses during recreational activities (e.g., swimming, water skiing). Exposure to high pathogen levels in swimmable waters has been linked to a number of adverse health effects, including gastrointestinal illness, respiratory illness, eye ailments, and ear ailments (Abt Associates, 2006; Rodriguez-Tapia and Morales-Novelo, 2017). The cost of illness associated with recreational exposure can be significant. Therefore, establishing WQS for pathogens could reduce the risk of gastrointestinal diseases and other adverse health effects for Tribal members and non-Tribal users of water resources in Indian reservations.
Market Benefits
Some of the social benefits expected from implementation of baseline WQS on Indian reservation waters will manifest themselves in economic markets through changes in price, cost, or quantity of market-valued activities. Benefits related to goods and services traded in markets, such as increased yields from commercial fisheries, are typically measured using standard market approaches based on data including market prices and quantities (Boardman et al., 2001). Competitive prices can also be used to measure benefits related to avoided costs associated with market goods and services. Improved water quality resulting from implementation of baseline WQS for Indian reservation waters is expected to generate numerous market benefits, including water supply and use, commercial fishing or shellfishing, and increased property values near Indian reservation waters or downstream stream reaches.
Commercial Fisheries
Tribes harvest shellfish and finfish commercially in waters both on and off Indian reservations, according to the Tribal treaty and reserved rights. Commercially harvested fish and shellfish are then sold to licensed seafood buyers who either sell fish and shellfish directly to the public or to other commercial entities. Salmon are especially important in Tribal commercial fisheries. Tribal salmon from the Columbia River grossed $4 million in 2008 (CRITFC, 2016). Salmon also comprises the majority of the Gray's Harbor Fall commercial fish catch for the Quinault Tribe, while Steelhead dominates the winter harvest (Washington Department of Fish and Wildlife, 2016). Bivalves are an important commercial food source for Tribal communities, particularly in the Pacific Northwest. For instance, the Quinault Indian Nation relies on razor clam fisheries along the Washington coast (Huppert and Trainer, 2014).
Pollutants found in Indian reservation waters or downstream can reduce fish populations by inhibiting reproduction, growth, and survival of aquatic species (EPA, 2009, 2011; Friedman et al. 1996; Niimi and Kissoon 1994) resulting in fewer and smaller fish. These changes may negatively affect commercial fishing and shellfishing conducted by Tribal members and other fishers, as well as consumers of fish, shellfish, and other seafood products. Degraded water quality has already reduced Tribal shellfish fisheries. Shellfish used to be an abundant food source, but 75 percent of mussel species found in North American lakes and streams are now endangered, and most of the shellfish harvest in the Pacific Northwest now comes from farming operations (Columbia River Inter-Tribal Fish Commission, 2016; Noble et al. 2016). Shellfish bed closures due to pathogen contamination are expensive and have wide-ranging direct and indirect impacts on consumers and the fishing industries, resulting in millions of dollars of lost clam and oyster revenues (Ofiara and Seneca, 2006). For example, a commercial razor clam closure for the Quinault fishery would cause approximately $117,000 in lost income from a half year closure and $1.4 million for a full year closure (Huppert and Trainer, 2014). Additionally, news of a toxic substance in seafood or a disease outbreak can cause changes in consumer behavior and reduce demand for shellfish, resulting in significant economic losses (Ofiara and Seneca, 2006). Implementation of baseline WQS in Indian reservation waters that provide nursery habitat for commercially harvested fish and shellfish species would enhance species habitat. This would contribute to species reproduction and survival and to larger fish and shellfish harvests, which in turn would lead to an increase in producer and consumer surplus.
Enhanced Property Values
Excess sediment is one of the leading causes of water quality impairment in Indian reservation waters. Aesthetic degradation of land and water resources resulting from increased water turbidity due to sediments and other pollutants can reduce the market value of property and thus affect the financial status of property owners. For example, a hedonic price study by Bejranonda et al. (1999) found that "the rate of sediment inflow entering the lakes has a negative influence on lakeside property rent" (p. 216).
Implementation of baseline WQS on Indian reservation waters is expected to improve the aesthetic quality of the water resources by reducing pollutant discharges and thus, enhancing water clarity, odor, and color in the receiving and downstream stream reaches. Several studies (Bin and Czakowski, 2013; Boyle et al., 1999; Leggett and Bockstael, 2000; Poor et al., 2001; Tuttle and Heintzelman, 2014; Walsh et al., 2011) suggest that waterfront property is more desirable when located near unpolluted water. Therefore, implementation of baseline WQS for Indian reservation waters is expected to enhance property values near Indian reservation waters or downstream stream reaches. EPA was unable to find studies to support property value benefit valuations from improved water quality to Indian reservation waters since Indian reservation land is typically not sold in open markets. However, it is reasonable to assume that the owners would benefit from water quality improvements.
Nonmarket Water Quality Benefits
Promulgation of baseline WQS for Indian reservation waters is expected to provide ecological benefits through improvements in the habitats or ecosystems (aquatic and riparian) that are adversely affected by pollution. Many pollutants found in Indian reservation waters can adversely affect the survival, growth, and reproduction of aquatic organisms. Such effects are ecologically significant when they affect the size, structure, or function of populations. As discussed above, toxic pollutants found in Indian reservation waters may also contaminate fish tissue and therefore decrease the value of fishery resources.
Promulgation of baseline WQS can help reestablish productive ecosystems in damaged waterways and protect resident species, including threatened and endangered (T&E) species. EPA expects promulgation of baseline WQS for Indian reservation waters to enhance the general health of fish and invertebrate populations, increase their propagation to waters currently impaired, and expand fisheries for subsistence, recreational, and commercial purposes. The resulting improvements in water quality will also benefit recreational activities such as swimming, boating, fishing, and water skiing. Finally, EPA expects the promulgation of baseline WQS for Indian reservation waters to augment nonuse values (e.g., option, existence, and bequest values) of the affected water resources.
Cultural and Traditional Use Benefits
Promulgation of baseline WQS for Indian reservation waters is expected to reduce ambient pollutant concentrations in the affected waters and thus enhance uses of these waters for cultural and traditional uses. The impact of contaminants on water quality can affect the ability of Tribes to maintain traditions and cultural landscapes, which form a connection between the land and the people (Big Valley Band of Pomo Indians and Karuk Tribe, 2019). 
Some aquatic plants and animals have traditional and sacred cultural significance to Tribes. For example, the Ojibwe and Dakota Tribes in Minnesota have significant cultural ties to wild rice (MPCA, 2017). Wild rice has been gathered by Ojibwe peoples for generations, and its use by the Tribe can be traced back to the time its ancestors migrated to the area. Pollution from ions, such as sulfate, is of significant concern to the Tribes because of the effects on wild rice. 
Numerous fish species are culturally significant as both a food and cultural resource for Tribes throughout North America. For example, in the Pacific Northwest, salmon play very important roles in traditional meals and ceremonies. Tribal people pass on expert knowledge of ecosystems and the history of preceding generations; this expert cultural exchange of information about fish and water preserves the rich cultural traditions of many Tribes (NEJAC, 2002). In addition, water itself is also a part of cultural ceremonies where it is used to purify the body before eating and is then consumed to purify foods that are eaten (NEJAC, 2002).
These examples illustrate important cultural benefits that Tribal members value from water resources. These cultural benefits have generational traditions and a rich history that serve a significant basis for many Tribal beliefs and values.
Recreational Benefits
Under federal law, Indian lands are private trust assets which cannot be used by non-Tribal members without a permit or license to fish, boat, hunt, camp, or otherwise use natural resources. However, many Tribes sell licenses for a wide variety of recreational activities on Indian reservations, including camping, boating, fishing, and hunting. Recreational activities that may be enhanced by improved water quality in Indian reservation waters include:
   Outings. Activities that take place near water such as hiking, jogging, picnicking, and wildlife viewing may be adversely affected by pollutant discharges that lead to a decrease in the aesthetic qualities of a waterbody or that negatively impact populations of fish, wildlife, and local flora.
   Recreational Fishing. Degraded water can reduce fish populations by inhibiting reproduction and survival of an aquatic species, leading to fewer and smaller fish and a reduction of the game fish population. Pollutants may also reduce the aesthetics of the water body, which may reduce anglers' enjoyment of their fishing experience. Also, turbidity caused by pollutant discharges may affect recreational anglers by reducing the distance over which fish can see lures, resulting in lower catch rates (Clark et al., 1985).
   Boating. Polluted water reduces the aesthetic appeal of recreational boating activities and can affect the safety of boating. For example, turbidity may obscure underwater obstacles, making collisions more likely. Increased sediment concentrations may also create sandbars, increasing the chances of running aground.
   Swimming. Pollution of water by toxic chemicals or by fecal indicator bacteria may cause closure of water bodies for swimming. Eutrophication caused by nutrients and turbidity caused by sediment and other pollutants also may greatly reduce a swimmer's aesthetic enjoyment of a water body. Additionally, turbidity may create safety hazards for the swimmer by reducing the ability to see underwater hazards or increasing diving accidents by impairing the ability to gauge water depth.
   Hunting. Similar to the effect on outings, discharged pollutants may greatly detract from the hunters' aesthetic enjoyment of a water resource. Damage to flora and fauna may also affect the game population, reducing the number and quality of the game available. 
Conversely, improved water quality may translate into two components of recreational benefits: an increase in the value of a recreational trip resulting from a more enjoyable experience and an increase in recreational participation.
Nonuse Benefits
Use benefits are values individuals hold for an environmental improvement that can be inferred through a change in demand for one or more market goods (i.e., purchases of complementary goods such as equipment and travel). Thus, nonuse benefits are values individuals hold for an environmental improvement that are independent of purchases of market goods and services. The total benefits of an environmental improvement are the combination of use and nonuse benefits (Freeman III, 1993, 2003). Recent economic literature provides substantial empirical support that nonuse values, such as option and existence values, are greater than zero. In fact, small per capita nonuse values held by a substantial fraction of the population can be very large in the aggregate. Consequently, both EPA's own Guidelines for Preparing Economic Analysis and the Office of Management and Budget's (OMB) Circular A-4 governing regulatory analysis support the need to assess nonuse values (EPA, 2010b; USOMB, 2003). Excluding nonuse values from consideration is likely to substantially understate total social values.
Nonuse values may be more difficult to assess than use values for several reasons. First, nonuse values are not associated with easily observable behavior. Second, nonuse values may be held by both users and nonusers of a resource. Because nonusers may be less familiar with particular services provided by a resource, they may value the resource differently compared to users of the same resource. Third, the development of a defensible stated preference survey (the generally accepted technique for estimating nonuse values (EPA, 2010b; USOMB, 2003))is often a time- and resource-intensive process.
Although EPA is not always able to estimate changes in nonuse values as part of regulatory development, an extensive body of environmental economics literature demonstrates that the public holds significant value for services flowing from natural resources well beyond those associated with direct uses (Boyd et al., 2001; Fischman, 2001; Heal et al., 2001; Herman et al., 2001; Ruhl and Gregg, 2001; Salzman et al., 2001; Wainger et al., 2001). Studies have documented public values for the services provided by a variety of natural resources potentially affected by environmental impacts, including fish and wildlife (Loomis et al., 2000; Stevens et al., 1991); wetlands (Woodward and Wui, 2001); wilderness (Walsh et al., 1984); critical habitat for T&E species (Hagen et al., 1992; Loomis and Ekstrand, 1997; Whitehead and Blomquist, 1991); shoreline quality (Grigalunas et al., 1988); and beaches, shorebirds, and marine mammals (Rowe et al., 1992), among others. 
Many ecosystems provide goods and services that contribute to societal well-being, but may be generally unrecognized because of the indirect nature of the effect. As such, valuations based solely on the analysis of markets are unlikely to capture the full economic value of the affected ecosystem services (Costanza and Folke, 1997). 
Summary of Benefits
Exhibit 4-2 summarizes potential benefits from promulgating potential baseline WQS for certain Indian reservation waters, including environmental services affected by pollutant reductions and entities affected by environmental changes. 
Exhibit 4-2 Summary of Benefits from Promulgating WQS for Indian Reservation Waters
Activity
Environmental Services Potentially Affected by Tribal WQS
Entities Affected by Environmental Improvements

Private Sector*
Government**
Tribal Members***
Others**** (downstream)
Fish and Shellfish Consumption
Food safety (reduced exposure to carcinogens and human health toxicants)
                                       
                                       
                                       
                                       
Commercial Fishing and Shellfishing
Fish and shellfish populations
                                       
                                       
                                       
                                       
Subsistence Fishing
Fish and shellfish populations
                                       
                                       
                                       
                                       
Property Values
Aesthetics, property value, turbidity
                                       
                                       
                                       
                                       
Water Supply and Use (Drinking)
Water safety, turbidity
                                       
                                       
                                       
                                       
Cultural and Traditional Uses
Food and water safety, cultural resources
                                       
                                       
                                       
                                       
Recreation
  Fishing
  Near-water
  Boating
  Swimming
  Hunting
Water safety (reduced risk of gastrointestinal illness), aesthetics, water clarity, degree of sedimentation, eutrophication, fish and shellfish populations
                                       
                                       
                                       
                                       
Nonuse
  Bequest
  Existence
  Altruistic
Environmental health, ecosystem and habitat protection
                                       
                                       
                                       
                                       
Notes:
* Fishing-related industries potentially benefit from larger fish populations and fewer fish consumption advisories. Any firms that use water from affected waterbodies could benefit from water quality improvements. Businesses located near affected waterbodies may benefit from higher property values. Recreation-based businesses (e.g., sightseeing tours, equipment rentals) potentially benefit from improved recreational experiences.
** Governments may benefit if water quality improvements reduce treatment costs for drinking water and other water supplies. They could also benefit from increased property tax revenues if water quality improvements enhance property values.
*** Tribal members potentially benefit from all affected services, with the possible exception of enhanced property values. Indian reservation land is typically not sold in open markets. However, it is reasonable to assume that the owners would benefit from water quality improvements.
**** Assuming water quality improvements downstream from Indian reservation lands are significant, downstream residents potentially benefit from all affected services.
Method for Estimating Potential Costs: Point Sources
This section describes the method EPA used for estimating the potential costs to point sources associated with the proposed baseline WQS, specifically the economic analysis criteria described in Section 3.3. Control costs for municipal and industrial point sources may result from changes to individual NPDES permit requirements.
Identification of Potentially Affected Permittees
EPA's Integrated Compliance Information System (ICIS) database identifies 220 NPDES individual permits as discharging in Indian country, some of which are discharging to Indian reservation waters outside the scope of this analysis (e.g., Indian reservation waters with CWA-effective WQS). To select only the facilities within the scope of this analysis, EPA reviewed and mapped the ICIS Indian country data, and mapped the Indian reservations with waters that may be subject to the proposed baseline WQS. In addition, EPA mapped all individual NPDES dischargers in the United States to identify additional dischargers to Indian reservation waters that may not be labeled as discharging to Indian country in the ICIS database. 
The above analysis identified a total of 164 individual NPDES permits for facilities with discharges in Indian reservation waters subject to this analysis (7 majors and 157 minors). EPA uses the designation of "major" for municipal wastewater treatment plants (WWTPs) of 1 million gallons per day (MGD) or more, or serving a population of 10,000 or more, and industrial discharges with a major rating code over a specified value based on the presence of toxics and size of discharge flow (EPA, 2010a).
The proposed baseline WQS may also affect facilities upstream from Indian reservation waters, so EPA identified facilities within five miles of Indian reservation boundaries and upstream from Indian reservation waters. To identify those facilities, EPA conducted an initial nationwide ICIS query followed by geographic information system (GIS) mapping of latitude/longitude coordinates for the individual NPDES permittees, which identified 999 facilities (193 major and 806 minor). EPA then used surface water (i.e., streams and catchment areas/watersheds to those streams) GIS data from the United States Geological Survey (USGS) National Hydrography Dataset (NHD) to identify facilities upstream from Indian reservation waters. EPA relied on the following assumptions for the GIS upstream analysis: 
Facilities are upstream if they discharge to a catchment, or within the catchment (as defined by NHD) to a stream that either flows through Indian reservations or borders the Tribal boundary.
Facilities discharging upstream from, or in a non-flowing water body abutting Indian reservations are considered upstream from the reservation. 
Tidal influence into rivers was ignored at this time. 
The steps above narrowed the number of individual permit facilities upstream from Indian reservation waters to 274 (50 majors, 221 minors, and 3 without designation). 
For purposes of this analysis, facilities discharging to Indian reservation waters are referred to as "Tribal" facilities, while those discharging upstream from Indian reservations are identified as "upstream" facilities. Exhibit 5-1 shows the categories of individual NPDES permit facilities discharging to Indian reservation waters and upstream from those waters. Most of these facilities are sewerage systems, defined as those facilities both public and private that collect and treat primarily domestic wastewaters. Sewerage systems are also referred to as POTWs, wastewater treatment facilities (WWTFs), or WWTPs.
Exhibit 5-1 NPDES Facilities that May be Affected by the Proposed Baseline WQS

Tribal
Upstream

Category*
Major
Minor
N/A
Major
Minor
N/A
Total
Sewerage Systems
                                                                              7
                                                                             90
                                                                              0
                                                                             41
                                                                             98
                                                                              1
                                                                            237
N/A**
                                                                              0
                                                                             19
                                                                              0
                                                                              0
                                                                             49
                                                                              1
                                                                             69
Water Supply
                                                                              0
                                                                             13
                                                                              0
                                                                              0
                                                                              8
                                                                              0
                                                                             21
Crude Petroleum And Natural Gas
                                                                              0
                                                                             11
                                                                              0
                                                                              0
                                                                              5
                                                                              0
                                                                             16
Construction Sand And Gravel
                                                                              0
                                                                              4
                                                                              0
                                                                              0
                                                                              4
                                                                              0
                                                                              8
Hotels And Motels
                                                                              0
                                                                              4
                                                                              0
                                                                              0
                                                                              3
                                                                              0
                                                                              7
Poultry Slaughtering And Processing
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              4
                                                                              0
                                                                              5
Fish Hatcheries And Preserves
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              4
                                                                              0
                                                                              5
Dairy Farms
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              5
                                                                              0
                                                                              5
Electric Services
                                                                              0
                                                                              0
                                                                              0
                                                                              2
                                                                              2
                                                                              0
                                                                              4
Elementary And Secondary Schools
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              3
                                                                              0
                                                                              4
Refuse Systems
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              3
                                                                              0
                                                                              4
Copper Ores
                                                                              0
                                                                              2
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              3
Pulp Mills
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              1
                                                                              0
                                                                              2
Beef Cattle Feedlots
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              2
Sporting And Recreational Camps
                                                                              0
                                                                              0
                                                                              0
                                                                              0
                                                                              2
                                                                              0
                                                                              2
Nitrogenous Fertilizers
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
Crude Petroleum Pipelines
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
Petroleum Refining
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
Finishing Plants
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
Paper Mills
                                                                              0
                                                                              0
                                                                              0
                                                                              1
                                                                              0
                                                                              0
                                                                              1
All Others***
                                                                              0
                                                                             10
                                                                              0
                                                                              0
                                                                             28
                                                                              1
                                                                             39
Total
                                                                              7
                                                                            157
                                                                              0
                                                                             50
                                                                            221
                                                                              3
                                                                            438
Notes:
* Based on standard industrial classification code. Source: EPA Enforcement and Compliance History Online (ECHO) and ICIS databases; Accessed February 2021 and some information from facility permits and fact sheets.
** Facility type was not specified in the ICIS-NPDES system. 
*** Includes industrial categories with only one minor discharger and no major dischargers.
Methodology for Sampling
As shown in Exhibit 5-1, there are 57 major (7 Tribal and 50 upstream), and 378 minor (157 Tribal and 221 upstream) individually permitted dischargers to waters for which the proposed baseline WQS would apply. Factors that may affect the potential magnitude of control costs include flow and facility type. Larger flows are typically associated with the largest treatment costs, although per-unit costs may decrease due to economies of scale. While POTWs are typically designed to treat domestic wastewater using biological treatment, industrial facilities have a wide range of process wastewaters with different characteristics and types of treatment technologies. Therefore, the costs for treating industrial wastewater are often different than those identified for POTWs. 
Minor dischargers typically do not have monitoring requirements for toxic pollutants so data to evaluate reasonable potential and the need for WQBELs for these facilities is limited. In addition, these facilities may not contribute significantly to instream loads even if such pollutants were present in their effluent. Thus, the potential for minor facilities to incur costs as a result of criteria translations is low, and minor facilities were not included in the selected sample. However, EPA acknowledges minor facilities with smaller operating budgets, such as those managed by smaller communities, could have more difficulty complying with any additional requirements than would major facilities. EPA has programs and tools available to assist Tribes in these situations, such as the Lagoon Wastewater Treatment Action Plan and various infrastructure funding opportunities.
Stormwater discharges are generated by precipitation and runoff from land, pavement, building rooftops, and other surfaces. During rainfall events, stormwater washes over the loose soil on construction sites, along with various materials and products being stored outside, and can pick up pollutants like sediment, debris, and chemicals. Also, road and parking lot run-off can contain a variety of pollutants such as copper from worn out brake pads, oil and grease, and polycyclic aromatic hydrocarbons (PAHs). Metal rooftops and atmospheric deposition onto roofs can contribute to metals and PAHs in stormwater, while birds and other animals leave fecal matter on rooftops and in gutters, which can contribute bacteria to run-off. Roofs with wooden or asphalt shingles can increase concentrations of chemicals used for waterproofing or weathering treatment (DeBusk et al., 2009). Although stormwater from municipal and industrial areas and from construction projects may contribute pollutants to Indian reservation waters, most stormwater discharges are regulated through general permits and most NPDES permits for stormwater discharges, whether individual or general, require permittees to develop and implement programs and plans to reduce pollutant discharges. Implementing the proposed baseline WQS may lead to increased or additional nonstructural best management practices (BMPs) (e.g., institutional, educational, or pollution prevention (P2) practices designed to limit generation of runoff or reduce the pollutant load in runoff) and structural controls (e.g., engineered and constructed systems designed to provide water quantity or quality control) for stormwater dischargers. However, for the most part, stormwater permits do not include numeric WQBELs to control pollutant discharges. Consequently, EPA was unable to estimate incremental costs to permittees with stormwater permits that may result from implementation of the proposed baseline WQS.
To incorporate facilities with the highest potential for cost, EPA included all Tribal major dischargers (7 facilities) and all upstream major industrial dischargers (9 facilities). In addition, EPA selected a sample of 10 upstream major sewerage systems (out of 41) to analyze as a basis for extrapolation of costs for remaining upstream facilities as described in Section 0 below. To select the sample of sewerage systems, EPA downloaded available flow data from ICIS-NPDES for all the upstream majors for the past five years and identified facilities with a broad geographic distribution and the most available and relevant pollutant monitoring data. EPA selected ten of the sewerage systems with sufficient data to conduct reasonable potential analyses based on geographic distribution of those facilities. 
Exhibit 5-2 provides a list of the 26 facilities included in the sample for reasonable potential analyses, with the Tribal facilities listed first, followed by upstream facilities, sorted alphabetically by NPDES identifier number. 
Exhibit 5-2 Sample NPDES Dischargers for Reasonable Potential Analyses
NPDES ID
Facility Name
Location
Region
Type
AZ0021415
Colorado River Sewage Joint Venture*
Tribal
                                       9
                                     WWTP
AZ0024627
Mesa Northwest Water Reclamation Plant (WRP)*
Tribal
                                       9
                                     WWTP
MI0023655
Mt. Pleasant WWTP*
Tribal
                                       5
                                     WWTP
MI0055808
Union Township WWTP*
Tribal
                                       5
                                     WWTP
MS0053503
Pearl River WWTP*
Tribal
                                       4
                                     WWTP
MT0030759
City of Hardin Water Treatment Plant (WTP)*
Tribal
                                       8
                                     WWTP
NY0020508
Salamanca WWTP*
Tribal
                                       2
                                     WWTP
AZ0020524
City of Phoenix 91[st] Avenue WWTP
Upstream
                                       9
                                     WWTP
AZ0024121
Pima County WRC Arva Valley Wastewater Reclamation Facility (WRF)
Upstream
                                       9
                                     WWTP
AZ0025208
Town of Florence WWTP
Upstream
                                       9
                                     WWTP
CA0104973
Coachella Valley Mid-Valley WRP
Upstream
                                       9
                                     WWTP
CO0031755
Pagosa Area Vista WWTP
Upstream
                                       8
                                     WWTP
IA0004014
CF Industries Nitrogen
Upstream
                                       7
                                  Industrial
IA0004103
MidAmerican-Neal North Energy Center
Upstream
                                       7
                                  Industrial
IA0061859
MidAmerican-Neal South Energy Center
Upstream
                                       7
                                  Industrial
ID0021784
City of Pocatello Water Pollution Control Facility (WPCF)
Upstream
                                      10
                                     WWTP
ND0020681
City of Devils Lake WWTF
Upstream
                                       8
                                     WWTP
NE0113735
MG Waldbaum Company
Upstream
                                       7
                                  Industrial
NM0020141
Los Alamos County WWTF
Upstream
                                       6
                                     WWTP
NM0028355
Los Alamos National Laboratory
Upstream
                                       6
                                  Industrial
OK0000256
Phillips 66 Ponco City Refinery
Upstream
                                       6
                                  Industrial
RI0000191
Kenyon Industries, Inc.
Upstream
                                       1
                                  Industrial
TX0101605
Roberto R. Bustamante WWTP
Upstream
                                       6
                                     WWTP
WA0002925
McKinley Paper Company
Upstream
                                      10
                                  Industrial
WI0003620
Domtar A.W., LLC Water Reclamation Center (WRC)
Upstream
                                       5
                                  Industrial
WI0020605
City of Baraboo WWTP
Upstream
                                       5
                                     WWTP
Note:
* Identifies a facility discharging to Indian reservation waters. 
Extrapolation Process
EPA selected all major industrials and all Tribal facilities for reasonable potential analyses, so no extrapolation of industrial or Tribal facility costs is required for this analysis. As discussed in Section 7, EPA also evaluated reasonable potential for 10 upstream sewerage systems, which were used to extrapolate costs to the remaining upstream sewerage systems that were not included as part of the facility sample. EPA extrapolated costs on a design flow basis (or actual flow where design flow was not available). The total costs for the relevant sewerage systems were divided by their total flow to obtain a unit cost per MGD. EPA then derived the cost for the facilities outside of the sample by multiplying their design flow (or actual flow where design flow was not available) by the unit cost derived from the sample. 
Determining Reasonable Potential
EPA conducted an analysis to determine whether dischargers have the reasonable potential (RP) to cause or contribute to an exceedance of the proposed baseline WQS. The analysis followed the approach outlined in the EPA Technical Support Document for Water Quality-based Toxics Control (EPA, 1991). Reasonable potential analysis (RPA) and WQBEL tools from EPA Region 10 were used to assess the effluent quality of the selected dischargers to determine whether criteria values would be exceeded and WQBELs would need to be established. 
For all facilities evaluated, EPA used approved regulatory mixing zone (RMZ) dilution factors if authorized and detailed in the NPDES permit fact sheet. If dilution factors were not provided and critical flow data were available, those flows were used in the analysis to derive approximate dilution factors. If neither dilution factors nor critical flows were available for facilities discharging to flowing waters, or if the permit prohibited any mixing zones or dilution factors, an effluent analysis was performed (i.e., EPA made the conservative assumption of no dilution). For lake or marine discharges without available dilution factors, a 10:1 dilution factor was assumed. 
Discharge data for the facilities were obtained through ICIS-NPDES and used in the RPA process. For the RPA projections, EPA calculated the maximum effluent concentration of each pollutant analyzed for each facility and applied multipliers to the maximum observed effluent concentration to determine a statistical maximum expected concentration of the pollutant (EPA, 1991). EPA made the following assumptions to determine the maximum expected effluent concentration.
For aquatic life economic analysis criteria, EPA used available effluent data to statistically project the 99[th] percentile effluent concentration with 99% confidence and used this concentration in the RPA analysis.
For human health economic analysis criteria, EPA used available effluent data to calculate the 50[th] percentile effluent concentration if the data set included 10 or more data points or to statistically project the 50[th] percentile with 99% confidence from a smaller data set.
The fewer the number of data points available for the analysis, the larger the multiplying factor used to statistically project a maximum expected concentration of the pollutant. 
For purposes of effluent characterization in this analysis, if a result was reported as not detected because the result was below the DL, EPA assumed a result of zero. If the result was reported as less than a specific concentration or as not quantifiable, EPA assumed a result equal to one-half of the DL. 
If ambient data for a particular pollutant were not available, EPA used a value equal to one-half the DL for that pollutant as receiving water pollutant concentration in the analysis. However, if one-half of the DL exceeds the most stringent criteria, the RPA tool would calculate negative effluent limitations; to avoid this situation, EPA used a value of zero for receiving water pollutant concentration in such cases. 
When the projected concentration at the boundary of the RMZ or at the point of discharge (whichever is appropriate) is less than both the acute and chronic criteria for aquatic life and human health criteria (where applicable), there is no reasonable potential and a WQBEL is not necessary. If the concentration is greater than any applicable criterion, there is reasonable potential and the permit writer develops WQBELs for that pollutant. Exhibit 5-3 summarizes the RPAs for the potentially affected facilities. Appendix A provides the details of the analyses. 
Exhibit 5-3 Pollutants Triggering RP for Sample NPDES Dischargers 
NPDES ID
Facility Name
Pollutants Triggering RP 
(None if blank)
AZ0021415
Colorado River Sewage Joint Venture*
Zinc
AZ0024627
Mesa Northwest WRP*
Bacteria, Ammonia
MI0023655
Mt. Pleasant WWTP*
Bacteria
MI0055808
Union Township WWTP*

MS0053503
Pearl River WWTP*
Bacteria, Ammonia, Copper
MT0030759
City of Hardin WTP*
Bacteria, Copper, Zinc
NY0020508
Salamanca WWTP*
Bacteria, Chlorine
AZ0020524
City of Phoenix 91[st] Avenue WWTP
Bacteria, Ammonia, Chlorine
Cyanide, Manganese
AZ0024121
Pima County WRC Arva Valley WRF

AZ0025208
Town of Florence WWTP
Bacteria, Ammonia, Cyanide
Chlorodibromomethane, Selenium
CA0104973
Coachella Valley Mid-Valley WRP
Bacteria, 4-4'-DDT, alpha-BHC
Ammonia, Chloride, Chlorodibromomethane, Copper
Dichlorobromomethane, Selenium
Silver ,Solids, Dissolved and Salinity, Zinc
CO0031755
Pagosa Area Vista WWTP
Bacteria, Arsenic, Cadmium
Chromium (VI), Copper, Cyanide, Lead, Manganese, Nonylphenol, Selenium, Zinc
IA0004014
CF Industries Nitrogen
Ammonia
IA0004103
MidAmerican-Neal North Energy Center

IA0061859
MidAmerican-Neal South Energy Center
Chlorine
ID0021784
City of Pocatello WPCF
Bacteria, Ammonia, Copper, Selenium
ND0020681
City of Devils Lake WWTF
Ammonia
NE0113735
MG Waldbaum Company
Ammonia, Chlorine, Copper
NM0020141
Los Alamos County WWTF
Bacteria, Aluminum
NM0028355
Los Alamos National Laboratory
Copper, PCBs
OK0000256
Phillips 66 Ponco City Refinery
Ammonia, Chromium (VI), Selenium
RI0000191
Kenyon Industries, Inc.
Aluminum, Ammonia, Chlorine, Copper
TX0101605
Roberto R. Bustamante WWTP
Ammonia, Chlorine
WA0002925
McKinley Paper Company

WI0003620
Domtar A.W., LLC WRC

WI0020605
City of Baraboo WWTP
Ammonia, Chloride
Note:
* Identifies a facility discharging to Indian reservation waters. 
Projecting Effluent Limits
For each facility and parameter with RP, EPA calculated average monthly and maximum daily effluent limits using the methodology consistent with EPA's 1991 Technical Support Document for Water Quality-based Toxics Control (TSD). Specifically, EPA calculated wasteload allocations (WLAs) and WQBELs to be protective of aquatic life and human health economic analysis criteria in the receiving water. The methodology accounts for the allowable dilution, ambient concentration, effluent variability, and sampling frequency.
For aquatic life economic analysis criteria, EPA calculated the WLAs (chronic and acute, respectively) using the following equations:
WLAchronic= Dmzx x (WQCchronic  -  Cb) + Cb
and
WLAacute= Dmzx x (WQCacute  -  Cb) + Cb
where,
WLA	= Wasteload allocation
Dmzx	= Dilution factor (Qeff + Qrecevingwater)/Qeff
WQC	= Water quality criterion
Cb	= Ambient background concentration.
A corresponding long-term average (LTA) is calculated from each WLA assuming that the WLA is set at the 99[th] percentile concentration using the following equations:
LTAa = WLAacute x e[[0.5σ2  -  zσ]]
LTAc = WLAchronic x e[[][0.5σ]42  -  [zσ]4[]]
LTAc = WLAchronic x e[[][0.5σ]302  -  [zσ]30[]] (ammonia and selenium only)
where:
σ2 = ln(CV[2] +1) where CV is the coefficient of variation
σ4[2] = ln(CV[2] /4 +1)
σ30[2] = ln(CV[2] /30 +1)
Z= 2.2326 for 99[th] percentile probability basis.
As recommended in the TSD (EPA, 1991), EPA selected the lowest LTA for each facility to calculate the maximum daily limit (MDL) set at the 99[th] percentile concentration and average monthly limit (AML), set at the 95[th] percentile concentration. The AML calculation also depends on an assumed monthly monitoring frequency. The TSD recommends assuming a minimum of four samples per month. The analysis follows this recommendation with the exception of calculating AMLs for aluminum and selenium where the analysis assumes 30 samples per month. As stated in the TSD, assuming a number of samples per month that matches the averaging period of the chronic criteria (4 days for most chronic criteria and 30 days for ammonia and selenium) avoids calculating an AML that exceeds the chronic WLA.
Developing WQBELs for toxic pollutants affecting human health is somewhat different from calculating WQBELs for aquatic life. The exposure period of concern is generally longer (e.g., often a lifetime exposure) and the average exposure, rather than the maximum exposure, is of concern. This analysis followed EPA's recommended approach for setting WQBELs for toxic pollutants for human health protection. The AML is equal to the WLA calculated from the human health toxic pollutant economic analysis criterion and the MDL is calculated from the AML based on expected monitoring frequency and assuming that the MDL is set at a 99[th] percentile concentration and that the AML is set at a 95[th] percentile concentration. 
For those facilities demonstrating RP, EPA calculated the potential WQBELs, including the AML and the MDL, shown in Exhibit 5-4. If both effluent limitations were calculated based on aquatic life and human health, they were compared and the more stringent effluent limitation selected. Exhibit 5-4 also provides DLs for each pollutant. All values in Exhibit 5-4 are provided in ug/L unless specified otherwise. 
Exhibit 5-4 Summary of WQBELs for Sampled Facilities (ug/L unless specified otherwise)
NPDES ID
Facility Name
Pollutant
DL
AML
MDL
AZ0021415
Colorado River Sewage Joint Venture*
Zinc
                                                                           0.05
                                                                             61
                                                                            120
AZ0024627
Mesa Northwest WRP*
Bacteria (cfu/100 mL)
                                                                            - 
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                          1,400
                                                                          5,500
MI0023655
Mt. Pleasant WWTP*
Bacteria (cfu/100 mL)
                                                                             -
                                                                            100
                                                                              -
MI00555808
Union Township WWTP
-
                                                                              -
                                                                              -
                                                                              -
MS0053503
Pearl River WWTP*
Bacteria (cfu/100 mL)
                                                                             -
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                          1,400
                                                                          5,000

Copper
                                                                            0.5
                                                                            2.0
                                                                            4.4
MT0030759
City of Hardin WTP*
Bacteria (cfu/100 mL)
                                                                            - 
                                                                            100
                                                                              -

Copper
                                                                            0.5
                                                                            2.2
                                                                            4.4

Zinc
                                                                           0.05
                                                                             61
                                                                            120
NY0020508
Salamanca WWTP*
Bacteria (cfu/100 mL)
                                                                            - 
                                                                            100
                                                                              -

Chlorine
                                                                             10
                                                                             33
                                                                             42
AZ0020524
City of Phoenix 91[st] Avenue WWTP
Bacteria (cfu/100mL)
                                                                             -
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                          1,400
                                                                          2,500

Chlorine**
                                                                             10
                                                                            4.0
                                                                             14

Cyanide**
                                                                              5
                                                                            4.5
                                                                            7.9

Manganese
                                                                            0.1
                                                                             30
                                                                             64
AZ0024121
Pima County WRC Arva Valley WRF

                                                                              -
                                                                              -
                                                                              -
AZ0025208
Town of Florence WWTP
Bacteria (cfu/100mL)
                                                                             -
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                          1,400
                                                                          5,500

Cyanide**
                                                                              5
                                                                            3.3
                                                                            9.6

Chlorodibromomethane
                                                                          0.003
                                                                           0.66
                                                                            1.3

Selenium
                                                                            0.6
                                                                            1.5
                                                                            5.9

Zinc
                                                                           0.05
                                                                             61
                                                                            120
CA0104973
Coachella Valley Mid-Valley WRP
Bacteria (cfu/100mL)
                                                                            - 
                                                                            100
                                                                              -

4,4'-DDT**
                                                                          0.012
                                                                      0.0000040
                                                                      0.0000080

alpha-BHC
                                                                              -
                                                                       0.000058
                                                                        0.00012

Ammonia
                                                                             10
                                                                          1,400
                                                                          4,800

Chloride
                                                                              4
                                                                        190,000
                                                                        380,000

Chlorodibromomethane
                                                                          0.003
                                                                           0.66
                                                                            1.3

Copper
                                                                            0.5
                                                                            2.2
                                                                            4.4

Dichlorobromomethane
                                                                          0.003
                                                                           0.79
                                                                            1.6

Selenium
                                                                            0.6
                                                                            1.5
                                                                            2.0

Silver
                                                                            0.1
                                                                            1.9
                                                                            3.8

Solids, Dissolved and Salinity
                                                                              -
                                                                        250,000
                                                                        270,000

Zinc
                                                                           0.05
                                                                             61
                                                                            120
CO0031755
Pagosa Area Vista WWTP
Bacteria (cfu/100mL)
                                                                             -
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                          1,400
                                                                          5,200

Cadmium
                                                                           0.05
                                                                            0.5
                                                                            1.4

Chromium (VI)
                                                                            0.3
                                                                             11
                                                                             12

Copper
                                                                            0.5
                                                                            1.4
                                                                            4.4

Cyanide**
                                                                              5
                                                                            4.0
                                                                            4.0

Lead
                                                                            0.6
                                                                            1.4
                                                                            4.7

Manganese
                                                                            0.1
                                                                             50
                                                                             91

Nonylphenol
                                                                               
                                                                            4.9
                                                                             12

Selenium
                                                                            0.6
                                                                            1.5
                                                                            2.7

Zinc
                                                                           0.05
                                                                             61
                                                                            120
IA0004014
CF Industries Nitrogen
Ammonia
                                                                             10
                                                                         77,000
                                                                        200,000
IA0004103
MidAmerican-Neal North Energy Center
-
                                                                              -
                                                                              -
                                                                              -
IA0061859
MidAmerican-Neal South Energy Center: Outfall 001
Chlorine
                                                                             10
                                                                             13
                                                                             24

MidAmerican-Neal South Energy Center: Outfall 007
Chlorine
                                                                             10
                                                                             13
                                                                             27
ID0021784
City of Pocatello WPCF
Bacteria (cfu/100mL)
                                                                             -
                                                                            100
                                                                              -

Ammonia
                                                                             10
                                                                         2,6600
                                                                         12,000

Copper
                                                                            0.5
                                                                            5.0
                                                                            7.9

Selenium
                                                                            0.6
                                                                            3.0
                                                                            8.7
ND0020681
City of Devils Lake
Ammonia
                                                                             10
                                                                          2,600
                                                                         25,000
NE0113735
MG Waldbaum Company
Ammonia
                                                                             10
                                                                          1,400
                                                                          5,400

Chlorine**
                                                                             10
                                                                            8.1
                                                                             19

Copper
                                                                            0.5
                                                                            2.2
                                                                            4.4
NM0020141
Los Alamos County WWTF
Bacteria (cfu/100mL)
                                                                             -
                                                                            100
                                                                              -

Aluminum 
                                                                              -
                                                                             67
                                                                            150
NM0028355
Los Alamos National Laboratory
Copper
                                                                           0.5
                                                                            2.2
                                                                            4.4

PCBs**
                                                                           0.03
                                                                      0.0000090
                                                                       0.000018
OK0000256
Phillips 66 Ponco City Refinery
Ammonia
                                                                             10
                                                                          1,400
                                                                          5,300

Chromium (VI)
                                                                            0.3
                                                                            5.0
                                                                             16

Selenium
                                                                            0.6
                                                                            1.5
                                                                            2.4
RI0000191
Kenyon Industries, Inc.
Aluminum 
                                                                              
                                                                          1,200
                                                                          3,700

Ammonia
                                                                             10
                                                                         32,000
                                                                        104,000

Chlorine
                                                                             10
                                                                            190
                                                                            480

Copper
                                                                            0.5
                                                                             57
                                                                             82
TX0101605
Roberto R. Bustamante WWTP
Ammonia
                                                                             10
                                                                          1,400
                                                                          2,600

Chlorine
                                                                             10
                                                                             11
                                                                             12
WA0002925
McKinley Paper Co.
-
                                                                              -
                                                                              -
                                                                              -
WI0003620
Domtar A.W., LLC WRC
-
                                                                              -
                                                                              -
                                                                              -
WI0020605
City of Baraboo
Ammonia
                                                                             10
                                                                          1,400
                                                                          4,200

Chloride
                                                                              4
                                                                        220,000
                                                                        250,000
Notes:
* Identifies a facility discharging to Indian reservation waters. 
** DL is greater than AML, MDL, or both. Compliance cost estimates for this facility and pollutant are based on the DL. 
Identifying Control Scenarios
Analysis of the available data for the sampled facilities indicates that implementing the economic analysis criteria would likely result in exceedances of projected effluent limits for bacteria, ammonia, chlorine, cyanide, and various metals and organic compounds. Potential alternatives for compliance with effluent limits for these pollutants include: 
Optimizing treatment processes (e.g., adding chemicals to increase flocculation or filtration efficiency) to increase pollutant removal efficiencies; 
Source control (e.g., P2 programs); 
Installing effluent treatment technology (e.g., chemical precipitation and filtration, ion exchange granular activated carbon (GAC)); and,
Alternative compliance mechanisms such as WQS variances, dilution credits (e.g., new or revised mixing zones), or criteria based on site-specific conditions.
Dischargers will likely pursue the lowest cost means of compliance with effluent limits first and may pursue multiple compliance mechanisms (e.g., P2 and treatment). The following section describes the various options for compliance considered in this analysis. 
Process Optimization
The lowest cost option to comply with effluent limits is likely the adjustment of existing treatment (i.e., process optimization). This option would be most feasible where relatively low pollutant reductions are needed or monitoring data indicate that pollutant loads increase throughout the treatment process as a result of chemical additions or treatment techniques. 
Process optimization usually involves process analysis and process modifications. Process analysis is an investigation of the performance-limiting factors of the treatment process and is a key factor in achieving optimum treatment efficiency. Performance-limiting factors for common wastewater treatment processes (e.g., sedimentation, activated sludge, filtration) may include operator training, response to changes in wastewater quality, maintenance activities, automation, and process control testing. The cost of process analysis includes the cost of additional or continuous monitoring throughout the treatment process, and a treatment performance evaluation. These costs vary based on the number of treatment processes to be analyzed and the magnitude of the reductions needed. 
Process modifications include activities short of adding new treatment technology units (conventional or unconventional) to the treatment train. For increasing pollutant removal efficiencies, process modifications could include adjusting coagulant doses to increase settling, equalizing flow if pollutant concentrations change during wet weather events, increasing filter maintenance activities or backwash cycles, training operators, and installing automation equipment including necessary hardware and software. Several months of adjustments may be needed to achieve a desired level of process optimization. In practice, the process modifications necessary would be determined by the process analysis study.
The effectiveness of process optimization largely depends on the efficiency of current operations, the existing treatment processes, and the fate and transport of the pollutant through the treatment train. For example, if a facility is already well maintained and operated, implementing process optimization may not result in additional pollutant reductions because the existing treatment processes are already performing at their feasible limits. Also, because most conventional treatment technologies are designed to maximize removal of suspended solids, process optimization aimed at increasing those removal efficiencies may not result in significant reductions for pollutants existing primarily in dissolved form. Given the available information for the sample facilities, it is generally not possible to estimate the reductions achievable with process optimization; rather, a detailed, site-specific study would be necessary. However, it is expected that process optimization may address compliance with effluent limits on ammonia and bacteria (see Appendix C for information on process optimization). 
Source Controls (Pollution Prevention Programs)
If adjusting existing operations is not feasible or not sufficient to achieve the necessary reductions, source controls would likely be the next most cost-effective control option. Source control could be used alone, or in conjunction with process optimization. The feasibility of source control efforts depends on the makeup of the influent and potential sources of the pollutant. For example, certain toxic pollutants are primarily used in industrial processes. Thus, for a municipal facility with a pre-treatment program, a feasible source control option would be regulating indirect industrial dischargers through pretreatment permits. Municipal facilities without a pre-treatment program may seek to implement one targeting the toxic pollutants of concern. Facilities that primarily treat commercial and residential wastewater (e.g., POTWs with no indirect industrial discharger) would likely have to concentrate efforts on public outreach and education or a sewer use ordinance. 
Costs for source control activities depend on the pollutant and the measures or controls implemented. For this analysis, EPA estimated that, where pollutant reductions were needed, most of the sample facilities would pursue P2 programs for targeted pollutants. However, as contributing sources are identified and controlled, the cost-effectiveness and efficacy of a P2 program will diminish, and a discharger may need to pursue additional compliance mechanisms.
Successful P2 programs will likely include at least some of the following steps:
Identify sources  -  particularly sources that contribute the greatest load to the influent;
Form a workgroup  -  preferably composed of representatives from government, industry, community, and environmental organizations that are either familiar with P2 strategies or familiar with the pollutant(s);
Define program goals  -  including a statement of how the municipality intends to reduce pollutant levels in its effluent, the purpose for doing so, and a timeline for completion;
Develop an approach  -  including selecting sectors for P2 efforts, the criteria for targeting efforts (e.g., size of the source loading, authority available to control the source, time required to produce desired results), whether efforts will be voluntary or regulatory, and who will execute each program effort;
Estimate program costs  -  develop estimates and identify entities that will bear the costs;
Implement program  -  starting with the most cost-effective measures and modifying activities and approach based on measured results;
Assess progress  -  including both successes and failures (i.e., lessons learned) throughout the duration of the program;
Provide follow-up  -  necessary to ensure P2 measures continue to be implemented; and
Develop a contingency plan  -  including a description of actions to be taken if plan efforts are unsuccessful.
The focus and approach of the program will be different for each community and sector targeted. As such, plans vary in complexity and in the resources necessary to achieve the goals set forth. 
The reductions in pollutants achievable through P2, and thus the ability to achieve compliance with numeric effluent limits using P2 alone, will vary based on existing treatment processes, complexity of the facility (for industrial discharges), the makeup and size of the service area of a WWTP (e.g., number of potential pollutant sources), and the level of P2 already being implemented. For example, large municipal facilities with numerous potential pollutant sources may see significant reductions after implementation of a measure that targets a major influent copper source, such as: requiring a pre-treatment permit from a sheet metal manufacturer or encouraging the main drinking water utilities in the service area to adjust pH levels in drinking water to the extent feasible. However, facilities with much smaller service areas may not be able to achieve the same reductions in their effluent with P2 due to a lower percent of easily identifiable and controllable sources contributing to the influent pollutant load. For example, sources from the residential sector are not as easy to identify as those from industrial and commercial sectors because they may originate from a wide range of products, as well as residential water pipes. Smaller municipalities are likely to receive most of their inflow from the residential sector. 
Little information is available on the cost of P2 programs for individual pollutants. For municipal dischargers, community size is likely to be a factor affecting P2 program costs. For example, it is unlikely that a minor POTW would need the same resources for program development and outreach efforts as a large major municipal facility because the minor facility's service area is smaller and contains fewer households and commercial/industrial dischargers to target. Smaller facilities may also pool their resources and develop a joint P2 program to save time and money on program development and outreach materials. Likewise, smaller industrial facilities engaging in a limited number of manufacturing processes should need to expend less resources on a P2 program than a large, complex industrial facility with multiple operations processing a variety of raw materials. P2 programs and program costs are discussed further in Appendix B. 
Effluent Treatment
If process optimization or source control is not sufficient for compliance with the economic analysis criteria, alternative discharge options or effluent treatment technologies may be necessary. For some facilities and pollutants of concern, EPA assumed that the control options implemented would include both effluent treatment and a P2 program.
For metals such as copper and cadmium, technologies that primarily target the dissolved fraction of the pollutant are most likely to achieve low effluent levels because most of the particulate fraction will already be removed with existing treatment controls designed to remove solids (see discussion of Process Optimization). For organic pollutants such as 4,4-DDT and alpha-BHC, similar treatment technologies can be used, although operating parameters may have to be adjusted to achieve optimal removal rates. An effective way to reduce disinfection by-products (e.g., trihalomethanes such as chlorobromomethane and dichlorobromomethane) may be to remove precursors in the effluent prior to disinfection, or to change the disinfection process. 
Exhibit 5-5 summarizes selected effluent treatment technologies that could be used to remove the pollutants of concern. Note that although these technologies theoretically should be able to achieve the levels needed to meet the baseline and revised criteria, it is likely pilot studies would be required at each facility to confirm technology performance prior to full-scale effluent implementation at that facility. It should also be noted that local water quality information (e.g., hardness, DOC) for some of these facilities could significantly change the numeric translation of the baseline narrative criteria (e.g., copper and other dissolved metals). 
Exhibit 5-5 Summary of Potential Effluent Treatment Technologies
Technology
Pollutants Removed
Comments
Chemical Precipitation
Metals (e.g., copper and cadmium) 
Pre-oxidation likely necessary to achieve low effluent levels; removal rates may be highly dependent on pH and other wastewater characteristics.
Nitrification
Ammonia
Requires sufficient oxygen and alkalinity
Chlorination
Cyanide
Requires addition of dechlorination
Dechlorination
Chlorine
Use of sulfur dioxide gas for dechlorination requires numerous safety precautions
Ion Exchange
Metals (e.g., copper and cadmium), nitrate, and radionuclides
System would have to be optimized for removal of a specific pollutant to achieve low effluent levels.
Granular Activated Carbon
Refractory organics (e.g., DDT, BHC), cyanide, PCBs, and some dissolved metal ions
Pretreatment to remove solids and prevent fouling; disposal of spent media could be costly.
Reverse Osmosis
Inorganics (e.g., copper, cyanide), pesticides, and microbial pollutants
Pretreatment (e.g., microfiltration) to prevent fouling; may need multiple units in series to achieve low effluent levels.

Appendix C provides detailed information on each treatment technology.
Alternative Compliance Mechanisms
If none of the control options discussed above would result in meeting the potential effluent limitations, or if the costs of available treatment would be prohibitive, dischargers would likely pursue some form of relief from the requirements. EPA estimated costs for WQS variances and dilution credits as alternative compliance mechanisms.
WQS Variances
40 CFR 131.14 describes federal WQS variances. A WQS variance is a time-limited designated use and water quality criterion for a specific pollutant(s) or water quality parameter(s) that reflect the highest attainable condition during its term. 
WQS variances adopted in accordance with § 131.14 provide a flexible but defined pathway for states and authorized Tribes to make incremental water quality improvements when the state or authorized Tribe demonstrates that the applicable designated use and associated criteria are not immediately attainable but may be attainable in the future. Per § 131.14(b)(1)(ii), WQS variances specify the interim requirements that apply during the WQS variance term based on the highest attainable condition. Further, WQS variances, if approved by EPA, become the applicable WQS for certain purposes during the term of the WQS variance: most importantly, they serve as the basis for water quality based effluent limits in NPDES permits or when issuing certifications under section 401 of the Act, for the permittee, parameter, and water body identified in the WQS variance. (§ 131.14(a)(3)). Once the WQS variance expires, NPDES permits must be written to meet the underlying designated use and associated criterion. If dischargers are still unable to meet the WQBELs derived from the designated use and criterion once a WQS variance term is complete, the state or authorized Tribe may adopt a subsequent WQS variance consistent with § 131.14. 
Dischargers for whom meeting effluent limits is cost-prohibitive are most likely to pursue a WQS variance based on economic infeasibility (i.e., the sixth condition above). The analysis to support such an application likely begins with a technical feasibility analysis, costs for which are detailed in Appendix B and summarized in Section 4.4.5. EPA based unit costs for applying for WQS variances on estimates previously developed for the economic analysis for EPA's copper and cadmium rule for the State of Oregon (EPA, 2016b). To account for a nationwide potential cost, EPA updated the Oregon costs to reflect national labor rates. The WQS variance process and cost estimation are detailed in Appendix B and the costs are summarized in Section 4.4.5. 
Mixing Zones and Dilution Credits 
The CWA does not require that all criteria be met at the exact point where pollutants are discharged into a receiving water prior to the effluent mixing with the receiving water. Sometimes it is possible to expose aquatic organisms to a pollutant concentration above a criterion for a short duration within a limited, clearly defined area of a waterbody while still maintaining the designated use of the waterbody as a whole. Where this is the case, a state or authorized Tribe may find it appropriate to allow ambient concentrations of a pollutant above the criterion in small areas near point-source outfalls, referred to as mixing zones (EPA, 2014).
Mixing zones may be established when a discharger has applied all known and reasonable controls and a dilution study has been performed. This study is the basis for calculating a potential dilution credit for a given pollutant. Dilution credits account for the assimilative capacity of the receiving water when computing the WLA applicable to a specific parameter that then becomes the basis for effluent limitations. Once approved, a dilution credit can reflect no more than the level of effluent and ambient receiving water mixing that occurs under critical conditions.
Dischargers who cannot readily comply with effluent effluent limitations based on the economic analysis criteria and who do not currently have an approved dilution credit for a pollutant of concern may elect to pursue approval of a dilution credit to achieve compliance with effluent limitations. A number of the NPDES permits from the facility sample already include dilution credits, but the permittees could still apply for a revision of these provisions.
When applying for a dilution credit a specific study is required to estimate and document the level of mixing that is present in the receiving water under applicable critical conditions. Details on the cost estimate for a dilution study are provided in Appendix B. Costs for a dilution study are also shown in Section 4.4.5. 
Method for Identifying Potential Impairments and Characterization of Nonpoint Sources 
This section describes the method EPA used for estimating the number of waters that may be identified as impaired based on comparison of available water quality monitoring data to the economic analysis criteria described in Section 3.3. Identification of impairments may lead to the need to further address nonpoint sources. Therefore, this sections also describes the major categories of nonpoint sources and ways to control their impact on water quality.
Available Data to Evaluate Impairments
To assess the degree to which Tribal waters may be impaired, EPA evaluated available data to evaluate current conditions to the economic analysis criteria described in Section 3.3. EPA first downloaded available instream monitoring water quality data of Indian reservation waters from the EPA and USGS' Water Quality Portal (WQP) and matched each monitoring station to the nearest water body from the USGS' NHD. EPA then used this data to assess the degree to which existing conditions are in compliance with economic analysis criteria. Although not representative of all Indian reservation surface waters, the locations for which monitoring data exceed the economic analysis criteria are candidates for listings of impaired waters for the purpose of estimating impacts. 
The WQP has data for over 630,000 sampling locations across the U.S. but does not identify Tribal waters and/or locations. To narrow the sampling locations prior to downloading WQP data, EPA identified NHD waterbodies within two miles of Indian reservation waters and selected all sampling locations within one mile of those waterbodies (approximately 25,000 locations), and used these locations' hydrologic unit code (HUC) level 8 to download water quality data at the HUC8 level. EPA then identified the closest water body to each sampling location (e.g., stream, pond), grouped sampling locations by water body, and excluded non-Tribal waters from the analysis. 
EPA downloaded the WQP data from these sampling locations for all available pollutants from January 1, 2011 to December 31, 2020. This is a reasonable timeframe to potentially include all of the Tribes' regularly monitored waters while still being relevant in characterizing current conditions. EPA conducted a review of the data for potential unit conversions and issues (e.g., unexpected units or lack thereof, data out of expected range  -  such as for pH, multiple names/acronyms for the same pollutant), and used the remaining data to identify exceedances of the economic analysis criteria. EPA also restricted the data to include only a single observation for each station and parameter on a single date. In most cases, EPA used the maximum concentration but used the minimum in cases where the economic analysis criteria represent a minimum concentration (e.g., dissolved oxygen).
Exhibit 6-1 provides a summary of the data used for the impairments analysis. 
Exhibit 6-1 Available Water Quality Data for Tribal Waters for Parameters with Economic Analysis Criteria
Parameter
Number of Waterbodies with Observations 
Number of Observations* Across Waterbodies
2,4-Dichlorophenol
                                                                              1
                                                                              1
Alkalinity
                                                                            128
                                                                          2,027
Aluminum
                                                                             50
                                                                            437
Ammonia
                                                                            175
                                                                          2,248
Anthracene
                                                                              1
                                                                              1
Antimony
                                                                             32
                                                                            352
Arsenic
                                                                            103
                                                                          1,045
Barium
                                                                             51
                                                                            647
Benzene
                                                                              1
                                                                              1
Cadmium
                                                                             30
                                                                            125
Carbaryl
                                                                              2
                                                                             38
Chloride
                                                                            184
                                                                          2,418
Chlorine
                                                                              3
                                                                             21
Chlorpyrifos
                                                                              2
                                                                             27
Chromium (III)
                                                                             34
                                                                            209
Chromium (VI)
                                                                              1
                                                                              1
Copper
                                                                             58
                                                                            423
Cyanide
                                                                              1
                                                                              1
Diazinon
                                                                              3
                                                                             26
Dieldrin
                                                                              2
                                                                              4
E. coli
                                                                            125
                                                                          2,041
Enterococci
                                                                              3
                                                                             66
Fluoranthene
                                                                              7
                                                                             18
Iron
                                                                            123
                                                                          1,106
Isophorone
                                                                              8
                                                                             44
Lead
                                                                             59
                                                                            331
Malathion
                                                                              1
                                                                              1
Manganese
                                                                            128
                                                                          1,222
Methylmercury
                                                                              4
                                                                             32
Mirex
                                                                              1
                                                                              1
Nickel
                                                                             37
                                                                            533
Nitrates
                                                                             98
                                                                          1,419
Oxygen, Dissolved
                                                                            213
                                                                          3,017
pH
                                                                            348
                                                                          4,403
Phenol
                                                                              3
                                                                              5
Pyrene
                                                                              6
                                                                             11
Selenium
                                                                             90
                                                                            774
Silver
                                                                             15
                                                                            112
Toluene
                                                                              5
                                                                              8
Zinc
                                                                             58
                                                                            327
Notes:
* Includes records with reported values for parameters with economic analysis criteria (see Section 3.3) between 2011 and 2020. 
Identifying Potential Impairments
EPA used the GIS data for the USGS NHD streams and catchments to group the sampling locations by water body (i.e., NHD reach), and conduct the assessment at the reach basis (identified as feature ID in the NHD data). EPA assigned to each sampling location the feature ID of the stream catchment in which it is located, such that multiple sampling stations are assigned the same feature ID when they are located in the same catchment. 
Depending on the type of pollutant, EPA identified a potential impairment for a pollutant in a particular stream reach when the following assumptions were met: 
Conventional pollutants: 10 percent of all the samples in a five-year rolling window exceed the economic analysis criteria.
Toxic pollutants: two or more sample results collected on different sampling dates in a three-year rolling window exceed the economic analysis criteria. 
EPA applied the conventional pollutant methodology to alkalinity, bacteria, dissolved oxygen, and total dissolved solids (TDS) and assigned the toxic methodology to all other pollutants. The analysis showed impairments of Indian reservation waters for 25 pollutants for either human health, aquatic life, or both economic analysis criteria. Exhibit 6-2 summarizes the potential impairments to Indian reservation waters by providing the number of feature IDs (reaches) potentially impaired for each pollutant and economic analysis criteria. 
Exhibit 6-2 Number of Reaches on Indian Reservation Waters that are Potentially Impaired by Economic Analysis Criteria and Parameter*
Parameter
AL Acute 
AL Chronic
HH
Any Criteria**
Alkalinity***
                                                                               
                                                                            114
                                                                               
                                                                            114
Aluminum
                                                                              3
                                                                             15
                                                                               
                                                                             15
Ammonia
                                                                              0
                                                                              2
                                                                               
                                                                              2
Antimony
                                                                               
                                                                               
                                                                              1
                                                                              1
Arsenic
                                                                              1
                                                                              2
                                                                               
                                                                              2
Barium
                                                                               
                                                                               
                                                                              1
                                                                              1
Cadmium
                                                                              1
                                                                              3
                                                                               
                                                                              3
Chloride
                                                                              1
                                                                              1
                                                                               
                                                                              1
Chlorine
                                                                              3
                                                                              3
                                                                               
                                                                              3
Chromium (III)
                                                                              0
                                                                              1
                                                                               
                                                                              1
Copper
                                                                             10
                                                                             14
                                                                              1
                                                                             14
Dieldrin
                                                                              0
                                                                              0
                                                                              1
                                                                              1
E. coli***
                                                                               
                                                                               
                                                                             68
                                                                             68
Enterococci***
                                                                               
                                                                               
                                                                              3
                                                                              3
Iron
                                                                               
                                                                             22
                                                                               
                                                                             22
Lead
                                                                              1
                                                                             11
                                                                               
                                                                             11
Manganese
                                                                               
                                                                               
                                                                             56
                                                                             56
Methylmercury
                                                                              1
                                                                              1
                                                                              1
                                                                              1
Nickel
                                                                              0
                                                                              1
                                                                              1
                                                                              1
Nitrates
                                                                               
                                                                               
                                                                             18
                                                                             18
Oxygen, Dissolved***
                                                                             60
                                                                             60
                                                                               
                                                                             60
pH***
                                                                               
                                                                             74
                                                                             54
                                                                             74
Selenium
                                                                              0
                                                                             24
                                                                              0
                                                                             24
Silver
                                                                              2
                                                                               
                                                                               
                                                                              2
Zinc
                                                                              2
                                                                              2
                                                                              1
                                                                              2
Total
                                                                             85
                                                                            350
                                                                            206
                                                                            500
Notes: 
AL = aquatic life; HH = human health
* Blanks indicate that there is no economic analysis criteria for the parameter. 
**Note that the number of waterbodies with impairments under any economic analysis criteria is not the sum of the waterbodies with individual economic analysis criteria impairments, since one water body may be impaired across more than one economic analysis criteria.
***Impairments for these pollutants used the conventional pollutant methodology.
EPA's evaluation of water quality data indicates that 215 reaches on Indian reservations would be considered impaired for at least one pollutant and economic analysis criteria under the proposed WQS, with many reaches impaired for multiple pollutants. Impairments total 500 when including all waterbodies and pollutants, for an average of 2.3 pollutant impairments per reach. 
Nonpoint Source Discharge Categories 
Pollutants can be introduced to surface water through natural and human activities that occur over large, diffuse areas and do not discharge at single, identifiable locations. These sources are referred to as nonpoint sources and can include agriculture, forestry, mining, urban stormwater, septic systems, atmospheric deposition, and contaminated sediments (legacy sources). The following sections describe these categories of nonpoint source dischargers, including the types of pollutants they may introduce into surface waters. 
Agriculture
Pesticides, fertilizers, and other chemicals applied to agricultural land can reach surface waters through irrigation return flow, stormwater runoff, and erosion of soils. Many chemicals on the human health and aquatic life pollutant lists are used as part of current and past agricultural practices, and therefore may enter surface waters on Indian reservations. For example, atrazine is an herbicide used primarily on farms to kill weeds. Guthion is an organophosphorous pesticide that was used on many crops, especially apples, pears, cherries, peaches, almonds, and cotton. Its use is being phased out by EPA due to toxicity concerns, but guthion residue may persist in the environment. Endosulfin is a pesticide used to control insects on food and non-food crops and also as a wood preservative. Nitrate and phosphorous are key components of fertilizers. Metals, such as cadmium and copper, can also be present in agricultural fertilizers or pesticides. In addition, erosion of soil on agricultural lands can increase TSS loads in surface water.
Farm animals can contribute bacteria and excess nutrients to downstream waters through fecal waste. Also, chemicals may be added to their feed or used directly on the animals for veterinary purposes. As an example, chlorpyrifos is an insecticide used to control ticks on cattle, as well as a spray to control crop pests.
Forestry
Forestry can contribute to surface water pollution through timber harvesting, thinning, road construction, fertilization, and chemical application. For example, to meet requirements for rapid reforestation after harvesting, forest landowners apply herbicides to protect tree seedlings from competing plants. Other chemicals may be used to control insects on forestry crops, such as hexachlorocyclohexane (HCH). Soil erosion is a significant concern in areas that are actively managed for forestry products because removal of trees and creation of forest roads can lead to increased TSS loads and turbidity in downstream surface water.
The processing of forestry products may also generate pollutants. For example, chlorophenols (e.g., 2,4,5-trichlorophenol, 2,4,6-trichlorophenol, and 2,4-dichlorophenol) and dioxin (2,3,7,8-TCDD) may be formed during the chlorine bleaching process at pulp and paper mills. Dioxin is known to be a human carcinogen, according to the National Toxicology Program.
Mining
Both currently active and abandoned/inactive mine sites can contribute to elevated pollutant concentrations in surface waters. Mining activities require large amounts of water to process ore, which results in discharged effluent (regulated as a point source discharge under the NPDES program), as well as seepage from tailings storage facilities, and accidental releases (both of which may be considered nonpoint source discharges). In addition to this direct contamination, exploratory activities such as road building and erosion of mineralized overburden during mine construction can also contribute to the contamination of surface water (Jennings et al., 2008). The leaching of heavy metals from excavated rock is especially problematic when mine wastes with high acid-generating potential are oxidized through exposure to surface conditions. 
To gain an understanding of the types of active and inactive mines present on Indian reservations, EPA obtained geospatial data from the USGS Mineral Resources Data System (MRDS). MRDS has state-by-state geospatial data on mines and mineral resources. EPA selected five representative states that were anticipated to have numerous mines on Indian reservations: Arizona, Utah, Washington, California, and South Dakota. Mine data for Indian reservations within these states was then extracted from the MRDS layers. The mine data were then further refined based on development status: only those mine sites that were listed as "producer" or "past producer" were included in the analysis; mines whose development status was listed as "occurrence", "prospect", or "unknown" were not included. 
On Indian reservations in Arizona, Utah, Washington, California, and South Dakota, MRDS listed 925 mines that were either a "producer" or "past producer" (i.e., active or inactive) with information on the type of material mined at the site. Of these 925 mine sites, 44 percent indicated their primary commodity was sand and gravel, while 44 percent indicated their primary commodity was some combination of metals, including barium, beryllium, copper, lead, iron, manganese, mercury, silver, titanium, uranium, and zinc. The remaining 11 percent of mines had varied commodities, including sulfur, asbestos, nitrate, and phosphorous. This analysis of readily-available geospatial data provides a snapshot of the types of mines that may be present on Indian reservations and therefore, the types of pollutants that may make their way into site run-off. 
Other chemicals may be used in the mining process that can potentially contaminate surface waters. For example, cyanide is currently employed to separate gold and silver from ore, while liquid mercury was used in the past. According to the MRDS data, silver and gold are primary commodities for 208 and 52 past or present mine sites, respectively, on Indian reservations in Arizona, Utah, Washington, California, and South Dakota. Thus, cyanide and mercury could potentially leach from these active or inactive mines.
Septic Systems
Septic systems (also known as onsite wastewater disposal systems) are used to treat and dispose of sanitary waste and are particularly common in rural areas. When properly sited, designed, constructed, and operated, septic systems pose a relatively minor threat to water sources. However, improperly operated septic systems can be a significant nonpoint source of groundwater contamination, which can lead to surface water pollution at the groundwater-surface water interface. 
Septic systems are a significant source of groundwater contamination leading to waterborne disease outbreaks and other adverse health effects. The bacteria (e.g., Escherichia coli), protozoa, and viruses found in sanitary wastewater can cause numerous diseases, including gastrointestinal illness, cholera, hepatitis A, and typhoid. In addition, septic systems can be a significant source of nitrate (e.g., from urine, feces, food waste, and cleaning compounds present in sanitary wastewater), which can contaminate groundwater over time (EPA, 2001b).
Atmospheric Deposition
Atmospheric deposition may be a potential nonpoint source of pollutants to surface waters through either direct or indirect deposition. Direct deposition occurs when pollutants are deposited directly on surface waters from the atmosphere. Indirect deposition reflects the process by which pollutants deposited on the land surface are washed off during storm events and enter surface water through stormwater run-off. Atmospheric deposition is not directly addressed through any existing regulation.
Atmospheric deposition of pollutants from industrial emissions, fossil fuel combustion, open pit mining, wind erosion, and other activities can contribute to pollution of Indian reservation surface waters. For example, chlorinated dibenzo-p-dioxins, such as dioxin, are released into the air in emissions from municipal solid waste and industrial incinerators. PAHs can be formed during incomplete burning of coal, oil and gas, garbage, or other organic substances. In addition, PCBs can exist as vapor in air and can be either directly or indirectly deposited in surface water. PCBs have been used as coolants and lubricants in transformers, capacitors, and other electrical equipment. The manufacture of PCBs was stopped in the United States in 1977 because of evidence they build up in the environment and can cause harmful health effects. Products made before 1977 that may contain PCBs include old fluorescent lighting fixtures and electrical devices containing PCB capacitors, and old microscope and hydraulic oils. PCBs are reasonably anticipated to be a human carcinogen, according to the National Toxicology Program.
Contaminated Sediments/Legacy Sources
When pollutants enter a water body through run-off, precipitation, or other means, they can accumulate in sediment at the bottom of wetlands, ponds, lakes, or rivers. Once in the sediment, these pollutants can persist for many years and are therefore often referred to as "legacy sources." These pollutants can affect the health of benthic organisms and can degrade overall water quality when the sediments are disturbed and resuspended. 
There are several major migration pathways for pollutants to reach sediments. Tributaries can carry pollutants, such as nutrients and PCBs. Nutrients, pesticides, (e.g., atrazine, and chlordane), chlorinated solvents (e.g., dichloromethane, tetrachloroethene, trichloroethane, and tricholoroethene), and fuel hydrocarbons can reach sediments through the groundwater-surface water interface. Atmospheric deposition can be a source of pollutants to sediments, including dioxin, PCBs, PAHs, and mercury. In addition, agricultural runoff can add to pollutant burden in sediments with pesticides and nutrients (Adriaens et al., 2002)
Legacy sources can persist long after a chemical has been banned from use. For example, the pesticide DDT was once widely used to control insects in agriculture and insects that carry diseases such as malaria. The use of DDT in the United States was banned in 1972 because of harm to wildlife. However, studies have found evidence of DDT in river sediments decades after its use was banned (Phillips et al., 1997). 
Identifying Potential Control Actions and Costs
Implementation of economic analysis criteria could result in identifying the need for additional controls on nonpoint sources of pollution, such as agriculture, forestry, mining, urban stormwater, septic systems, atmospheric deposition, and contaminated sediment. Exhibit 6-3 summarizes potential control actions required for nonpoint source dischargers.
Exhibit 6-3 Potential Control Actions Required for Nonpoint Sources of Contamination
Nonpoint Source
Potential Control Actions
Agriculture
Changes in fertilizer or pesticide use, sediment erosion controls beyond those under existing regulations
Forestry
Changes in fertilizer or pesticide use, sediment erosion controls beyond those under existing regulations
Mining
Cleanup and remediation, including excavation and onsite capping of contaminated soils, capping of onsite solid waste mining debris, re-grading of tailings to mitigate mass wasting and off-site migration, and abatement and mitigation of physical hazards
Septic Systems
Improve O&M of existing septic systems, upgrade failing septic systems, build centralized wastewater treatment facilities to replace septic systems, where feasible
Atmospheric Deposition
Reduce air pollution at industrial facilities, control actions for point source dischargers and nonpoint sources 
Contaminated Sediments/Legacy Sources
Control actions for point source dischargers and nonpoint sources listed above, clean up and remediation including excavation of contaminated sediments

Many of the controls and BMPs described above can have positive cumulative effects. For example, BMPs that control the erosion of toxic-containing sediments, such as increased riparian buffers, may also reduce stream temperatures by providing shade, and reduce nutrient loads by increasing nutrient uptake by plants. Buffers also slow runoff (reducing erosion), filter pollutants, and trap sediments. Thus, it is possible that controls can be implemented to meet multiple economic analysis criteria.
Nonpoint source controls, whether required through a nonpoint source program or implemented voluntarily, may lead to nonpoint sources incurring costs as an indirect result of the proposed baseline WQS. EPA did not estimate the costs of reducing pollution from nonpoint sources to meet the proposed baseline WQS for this analysis. This type of analysis would require site-specific knowledge and modeling that are beyond the scope of this analysis. Nonpoint source discharges are difficult to quantify because they are intermittent, variable, and occur under hydrologic or climatic conditions associated with precipitation events. In addition, nonpoint sources are not subject to regulatory programs under the CWA. Thus, data are too limited to reliably estimate the extent of incremental nonpoint source controls needed to comply with the economic analysis criteria for purposes of this analysis.
Implementing nonpoint source controls may relieve a portion of the estimated indirect burden on and cost to point sources within the same watershed. Control of nonpoint sources of the pollutants of concern could reduce costs to point sources. 
Potential Compliance Costs
This section summarizes the estimates of potential costs of implementing the economic analysis criteria, and discusses the limitations and uncertainties associated with the analysis. It includes a discussion of the estimated potential costs to point sources and a brief discussion of potential costs to nonpoint sources.
Potential Compliance Costs for Point Sources
For the 26 major facilities in the sample for this economic analysis, EPA estimated costs associated with actions or controls to meet the economic analysis criteria. Appendix A provides additional details on the cost estimates for each of the 26 facilities in the sample. EPA identified nitrification, chlorination/dechlorination, chemical precipitation, adsorption, and ion exchange as the most likely control options where additional treatment may be required. As noted previously, EPA assumed that the control options implemented would include both effluent treatment and a P2 program for some facilities and pollutants of concern. If none of the control options considered would result in meeting the potential effluent limitations, or if the costs of available treatment would be prohibitive, dischargers would likely pursue relief through an alternative compliance mechanism, such as a WQS variance, along with a P2 program. Appendix B provides a detailed description of the estimated costs of alternative compliance mechanisms. Some facilities may be able to use alternative compliance mechanisms other than a WQS variance and accompanying P2 program (e.g., dilution credit) at a lower cost, so assuming a WQS variance with a P2 program as the main alternative compliance mechanism may over-estimate cost. For some facilities and pollutants of concern, the available data did not clearly point to a specific effluent treatment technology or an alternative compliance mechanism as the most likely approach to compliance. In such cases, EPA estimated a range of potential costs for the facility. These costs are summarized in Exhibits 7-1 through 7-3 below.
As discussed in Section 5.4.1, RPAs were conducted for all 7 major facilities discharging directly to Indian reservation waters. Only 2 of the 7 major dischargers to Indian reservation waters (Pearl River WWTP and Salamanca STP) were projected to potentially incur costs for additional treatment. EPA estimated the capital and O&M costs for effluent treatment at both facilities, EPA annualized capital costs over 20 years using a 3 and 7 percent discount rate. In addition, the Pearl River WWTP could also potentially pursue an alternative compliance mechanism (i.e., a WQS variance with a P2 program) rather than effluent treatment. The other five facilities either (1) have no reasonable potential for any pollutant, (2) should be able to optimize their treatment systems, or (3) would likely pursue source control (P2 program) and possibly a WQS variance. For the Pearl River WWTP, the WQS variance cost is part of the low estimate because it would be in lieu of effluent treatment. For others, the WQS variance cost is part of the high estimate because it would be in addition to P2 program costs where P2 alone may be insufficient for compliance for certain pollutants. The estimated range of potential costs for the seven major facilities discharging directly of Indian reservation waters are presented in Exhibit 7-1. 
The remaining 19 major facilities in the sample discharge upstream from Indian reservation waters. Of these, nine are industrial facilities. EPA estimated capital and O&M costs for effluent treatment at the facilities that would potentially incur such costs, identifying a range where alternatives were appropriate to consider. EPA annualized capital costs for installing additional treatment over 20 years using a 3 and 7 percent discount rate. EPA also estimated one time and annual costs for a P2 program in addition to effluent treatment for these facilities. The estimated range of potential costs for each of the nine major industrial facilities discharging upstream (within five miles) of Indian reservation waters are presented in Exhibit 7-2 .
As discussed in Section 5, EPA also identified 41 major sewerage treatment plants located within 5 miles of Indian reservations and discharging upstream from Indian reservation waters as potentially affected by the proposed rule. EPA analyzed a sample of these 41 facilities for this economic analysis. The sample comprises 10 facilities with the most available data. The sample of 10 sewerage treatment plants was extrapolated to represent the entire group of 41 major sewerage treatment plants discharging within 5 miles upstream from Indian reservation waters. EPA estimated potential costs for the 10 major sewerage treatment plants in the sample. As with other facilities, EPA estimated capital and O&M costs for effluent treatment for the facilities that would potentially incur such costs, identifying a range where alternatives were appropriate to consider. EPA annualized capital costs for installing additional treatment over 20 years using a 3 and 7 percent discount rate. EPA estimated one time and annual costs for a P2 program in addition to or in lieu of effluent treatment for some facilities. Finally, EPA estimated one-time cost for facilities that may pursue a WQS variance for certain pollutants either in lieu of effluent treatment, or in addition to a P2 program where P2 alone may not be sufficient for compliance. In the former case, WQS variance cost appears as part of the low estimate. In the latter case, WQS variance cost appears as part of the high estimate. The estimated range of potential costs for the sample of 10 major sewerage treatment plants discharging upstream (within five miles) of Indian reservation waters are presented in Exhibit 7-3. 

Exhibit 7-1 Estimated Potential Costs (2020 dollars) for Facilities Discharging to Indian Reservation Waters
NPDES ID
Facility Name
Facility Type
Design Flow (MGD)
Effluent Treatment
P2 Program
WQS Variance One-Time Cost

Capital Cost (present value)
Annual O&M Cost
Annualized Cost
(n = 20 yr;
i = 3%)
Annualized Cost
(n = 20 yr;
i = 7%)
One-Time Cost
Annual Cost

AZ0021415
Colorado River SJV (low estimate)
WWTP
                                                                            1.2
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                       $16,557 
                                                                        $9,934 
                                                                             $0
AZ0021415
Colorado River SJV (high estimate)
WWTP
                                                                            1.2
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                        $16,557
                                                                         $9,934
                                                                       $173,004
AZ0024627
Mesa Northwest WRP
WWTP
                                                                             18
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
MI0023655
Mt. Pleasant WWTP
WWTP
                                                                           4.14
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
MI0055808
Union Township WWTP
WWTP
                                                                            2.4
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
MS0053503
Pearl River WWTP (low estimate)
WWTP
                                                                           1.50
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                       $33,114 
                                                                       $19,868 
                                                                      $173,004 
MS0053503
Pearl River WWTP (high estimate)
WWTP
                                                                           1.50
                                                                    $1,715,000 
                                                                      $452,020 
                                                                      $567,295 
                                                                      $613,904 
                                                                       $33,114 
                                                                       $19,868 
                                                                             $0
MT0030759
City of Hardin WTP (low estimate)
WTP
                                                                           2.16
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                       $16,557 
                                                                        $9,934 
                                                                             $0
MT0030759
City of Hardin WTP (high estimate)
WTP
                                                                           2.16
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                        $16,557
                                                                         $9,934
                                                                       $173,004
NY0020508
Salamanca WWTP
WWTP
                                                                           2.00
                                                                    $1,020,000 
                                                                       $46,370 
                                                                      $114,930 
                                                                      $142,651 
                                                                             $0
                                                                             $0
                                                                             $0

Exhibit 7-2 Estimated Potential Costs (2020 dollars) for Industrial Facilities Discharging Upstream from Indian Reservation Waters
NPDES ID
Facility Name
Facility Type
Design Flow (MGD)
Effluent Treatment
P2 Program
WQS Variance One-Time Cost

Capital Cost (present value)
Annual O&M Cost
Annualized Cost
(n = 20 yr;
i = 3%)
Annualized Cost
(n = 20 yr;
i = 7%)
One-Time Cost
Annual Cost

IA0004014
CF Industries Nitrogen
Industrial
                                                                           2.23
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
IA0004103
MidAmerican Energy North
Industrial
                                                                           6.03
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
IA0061859
MidAmerican Energy South
Industrial
                                                                      804 (max)
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
NE0113735
MG Waldbaum Co. (low estimate)
Industrial
                                                                            0.7
                                                                     $1,882,361
                                                                       $175,689
                                                                       $302,213
                                                                       $353,371
                                                                        $16,557
                                                                         $9,934
                                                                             $0
NE0113735
MG Waldbaum Co. (high estimate)
Industrial
                                                                            0.7
                                                                     $1,503,236
                                                                       $410,762
                                                                       $511,803
                                                                       $552,657
                                                                        $16,557
                                                                         $9,934
                                                                             $0
NM0028355
Los Alamos Lab
Industrial
                                                                     0.33 (max)
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
OK0000256
Phillips 66
Industrial
                                                                     5.32 (avg)
                                                                    $11,521,000
                                                                       $369,050
                                                                     $1,143,442
                                                                     $1,456,550
                                                                        $66,230
                                                                        $30,908
                                                                             $0
RI0000191
Kenyon Industries (low estimate)
Industrial
                                                                     0.55 (max)
                                                                     $1,708,746
                                                                       $165,586
                                                                       $280,440
                                                                       $326,880
                                                                        $33,114
                                                                        $19,868
                                                                             $0
RI0000191
Kenyon Industries (high estimate)
Industrial
                                                                     0.55 (max)
                                                                     $1,782,000
                                                                       $395,930
                                                                       $515,708
                                                                       $564,138
                                                                        $33,114
                                                                        $19,868
                                                                             $0
WA0002925
McKinley Paper Co.
Industrial
                                                                             12
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
WI0003620
Domtar A.W., LLC WRC
Industrial
                                                                    16.74 (max)
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0

Exhibit 7-3 Estimated Potential Costs (2020 dollars) for Sample Sewerage Treatment Plants Discharging Upstream from Indian Reservation Waters
NPDES ID
Facility Name
Facility Type
Design Flow (MGD)
Effluent Treatment
P2 Program
WQS Variance One-Time Cost

Capital Cost (present value)
Annual O&M
Cost
Annualized Cost
(n = 20 yr; 
i = 3%)
Annualized Cost
(n = 20 yr;
i = 7%)
One-Time Cost
Annual Cost

AZ0020524
City of Phoenix (low estimate)
WWTP
                                                                            230
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                        $49,672
                                                                        $20,973
                                                                             $0
AZ0020524
City of Phoenix (high estimate)
WWTP
                                                                            230
                                                                    $28,600,000
                                                                       $992,000
                                                                     $2,914,369
                                                                     $3,691,638
                                                                        $49,672
                                                                        $20,973
                                                                             $0
AZ0024121
Pima County Arva Valley WRC
WWTP
                                                                              4
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
AZ0025208
Town of Florence (low estimate)
WWTP
                                                                            2.5
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                        $49,671
                                                                        $29,802
                                                                       $346,008
AZ0025208
Town of Florence (high estimate)
WWTP
                                                                            2.5
                                                                     $5,944,000
                                                                       $317,849
                                                                       $717,379
                                                                       $878,921
                                                                        $49,671
                                                                        $29,802
                                                                             $0
CA0104973
Coachella Valley Mid-Valley WRP (low estimate)
WWTP
                                                                            9.9
                                                                     $3,978,548
                                                                       $131,200
                                                                       $398,621
                                                                       $506,747
                                                                       $132,460
                                                                        $61,816
                                                                     $1,203,376
CA0104973
Coachella Valley Mid-Valley WRP (high estimate)
WWTP
                                                                            9.9
                                                                    $27,253,999
                                                                     $2,350,790
                                                                     $4,182,687
                                                                     $4,923,375
                                                                       $132,460
                                                                        $61,816
                                                                             $0
CO0031755
Pagosa Area Water (low estimate)
WWTP
                                                                            3.9
                                                                     $3,723,033
                                                                       $294,710
                                                                       $544,956
                                                                       $646,138
                                                                        $49,671
                                                                        $29,802
                                                                       $519,012
CO0031755
Pagosa Area Water (high estimate)
WWTP
                                                                            3.9
                                                                     $6,322,000
                                                                     $1,049,030
                                                                     $1,473,967
                                                                     $1,645,782
                                                                        $49,671
                                                                        $29,802
                                                                             $0
ID0021784
City of Pocatello
WWTP
                                                                             12
                                                                     $6,286,000
                                                                       $279,970
                                                                       $702,488
                                                                       $873,324
                                                                        $33,115
                                                                        $15,454
                                                                             $0
ND0020681
City of Devils Lake
WWTP
                                                                            5.5
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
NM0020141
Los Alamos County
WWTP
                                                                            1.4
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
                                                                             $0
TX0101605
Roberto Bustamante 
WWTP
                                                                             39
                                                                    $12,860,000
                                                                       $616,709
                                                                     $1,481,103
                                                                     $1,830,601
                                                                             $0
                                                                             $0
                                                                             $0
WI0020605
City of Baraboo (low estimate)
WWTP
                                                                           2.53
                                                                       $988,000
                                                                        $66,210
                                                                       $132,619
                                                                       $159,470
                                                                        $16,557
                                                                         $9,934
                                                                             $0
WI0020605
City of Baraboo (high estimate)
WWTP
                                                                           2.53
                                                                       $988,000
                                                                        $66,210
                                                                       $132,619
                                                                       $159,470
                                                                        $16,557
                                                                         $9,934
                                                                       $173,004

EPA excluded three of the sampled facilities from the extrapolation to the remaining upstream sewerage facilities to provide a more representative estimate. The 10 sewerage treatment plants sampled out of the 41 major sewerage treatment plants within 5 miles of Indian reservations and discharging upstream from Indian reservation waters include the City of Phoenix, which has a very large design flow of 230 MGD, and the Coachella Valley Mid-Valley WRP, which is a large 9.9 MGD lagoon system that is not representative of typical major sewerage systems. In addition, the sample included the Arva Valley Wastewater Reclamation Facility in Tucson, Arizona (AZ0024121). Although this facility has a design flow of 4.0 MGD, effluent is routinely directed to one of five percolation basins. The fact sheet for the current permit indicates that during the prior permit term the facility did not discharge to surface water; therefore, there were no estimated incremental costs for this facility. Because the facility has no discharge, which is not typical for most sewerage treatment plants, its flow was also excluded from the extrapolation. The 7 sewerage treatment systems remaining in the sample of 10 facilities have a cumulative flow of approximately 66.8 MGD. The remaining 31 major sewerage systems that are within five miles of Indian reservations and discharging upstream from Indian reservation waters have a cumulative flow of approximately 230 MGD. EPA extrapolated the cost to the non-sampled facilities by multiplying the cost for the 7 representative facilities by the ratio of the flow for the non-sampled facilities to the flow of the representative facilities (230/66.8).
Exhibit 7-4 summarizes the estimated potential costs for major facilities by facility category.
Exhibit 7-4 Summary of Estimated Potential Costs (2020 $Millions) for Major Facilities
Facility Category
Total One-Time Costs
Total Annual Costs
(n = 20 yr; i = 3%)
Total Annual Costs
(n = 20 yr; i = 7%)
Low estimate
Facilities discharging to Indian reservation waters (7)
                                                                         $0.24 
                                                                         $0.15 
                                                                         $0.18 
Upstream industrial facilities (9)
                                                                         $0.12 
                                                                         $1.79 
                                                                         $2.20 
Sampled upstream sewerage systems (10)
                                                                         $2.37 
                                                                         $3.43 
                                                                         $4.18 
Extrapolated upstream sewerage systems (31)
                                                                         $3.38 
                                                                        $10.14 
                                                                        $12.38 
Total (low estimate)
                                                                         $6.10 
                                                                        $15.51 
                                                                        $18.94 
High estimate
Facilities discharging to Indian reservation waters (7)
                                                                         $0.41 
                                                                         $0.72 
                                                                         $0.80 
Upstream industrial facilities (9)
                                                                         $0.12 
                                                                         $2.23 
                                                                         $2.63 
Sampled upstream sewerage systems (10)
                                                                         $0.30 
                                                                        $11.77 
                                                                        $14.17 
Extrapolated upstream sewerage systems (31)
                                                                         $0.40 
                                                                        $15.81 
                                                                        $18.84 
Total (high estimate)
                                                                         $1.23 
                                                                        $30.54 
                                                                        $36.45 

The low estimate summary is taken from the facility-specific low estimates or sole estimates depicted in Exhibits 7-1 through 7-3, whereas the high estimate summary is taken from the facility-specific high estimates or sole estimates depicted in Exhibits 7-1 through 7-3. Total One-Time Costs is the sum of P2 and WQS variance one-time costs. Total Annual Costs is the sum of annualized effluent treatment and annual P2 costs. Total One-Time Costs are larger in the low estimate summary than in the high estimate summary because one-time WQS variance costs are often used in lieu of annualized effluent treatment costs for facility-specific low estimates for certain pollutants. Detailed analyses for each evaluated facility are presented in Appendix A. Total cost estimates range from $15.51 million in annualized costs over 20 years at a 3 percent discount rate (with $6.1 million in one-time costs) to $30.54 in annualized costs over 20 years at a 3 percent discount rate (with $1.23 million in one-time costs). Using a discount rate of 7 percent over 20 years, total annualized costs range from $18.94 million to $36.45 million.
Potential Compliance Costs for Nonpoint Sources and Stormwater
As described in Section 6.4, control costs for nonpoint sources (e.g., agricultural and forest operations; contamination from historic mining sites) include those needed to reduce instream pollutant levels to meet the economic analysis criteria. Current pollutant loadings from these sources are unknown; however, costs for nonpoint source controls could include:
Agricultural and forest lands  -  pesticide controls, sediment and erosion controls beyond those specified under existing state and federal regulations and plans if existing regulations are not sufficient to control such point sources; and
Mining  -  cleanup and remediation including excavation and onsite capping of contaminated soils, capping of onsite solid waste mining debris, regrading of tailings to mitigate mass wasting and off-site migration, and abatement and mitigation of physical hazards.
Uncertainties in the Analysis
There are a number of uncertainties in the analysis associated with data limitations, potential pollutant load reductions achievable, and how dischargers would respond to potential requirements and permit conditions that affect the estimated costs.
Data Limitations
The lack of available data for both point and nonpoint sources adds uncertainty to the analysis of potential costs associated with meeting the revised criteria. Key areas of uncertainty in the cost analysis are described below.
Economic Analysis Criteria
For the economic analysis criteria, EPA used a conservative approach to estimate the concentration values (e.g., copper criteria derived from conserved assumptions to the BLM, selenium criteria assuming all waters are lentic, ammonia criteria assuming a water temperature of 25 °C), which may differ from the approach that would be employed to establish criteria concentrations for specific waters. However, some of the economic analysis criteria developed for purposes of this analysis may be less stringent than values that could be derived using local water quality data (e.g., dissolved metals in areas with hardness higher than 100 mg/L). Therefore, costs may be over- or under-estimated depending on the pollutant and approach.
Benefits
The benefits evaluation is currently provided as a qualitative evaluation due to insufficient data. 
Point Sources
EPA relied on NPDES data for individual permits of major POTWs and industrial dischargers only. EPA was unable to estimate costs associated with either general permits or individual permits of minor dischargers in these two categories of dischargers.
Furthermore, EPA was not able to estimate costs associated with either individual or general permits regulating the discharge of urban stormwater, including discharges from municipal separate storm sewer systems, construction sites, and industrial areas. As discussed in Section 5.1, though urban stormwater from municipal and industrial areas may contribute pollutants to Indian reservation waters, most NPDES permits for stormwater discharges do not include numeric WQBELs.
In addition, data are not available for all pollutants at all NPDES-permitted facilities. Without data, EPA is not able to determine whether the facility would meet the economic analysis criteria. Thus, costs could be higher than shown if additional data indicate a need for pollutant reductions. For other facilities with effluent data, the data available are limited. For example, there may be only one data point for certain pollutants and facilities. If the available data do not reflect typical loadings, then the control costs could be either over- or under-estimated.
Ambient data are also limited. Assumptions made in the analysis when ambient data were not available may lead to over or underestimating the need for additional NPDES permit limits and the associated costs for point source dischargers
EPA also made assumptions regarding effluent and ambient concentrations when a parameter could not be detected or could not be quantified. These assumptions may lead to overestimating or underestimating the need for additional effluent controls and the resulting costs.
Facility permits and evaluation reports do not always provide detailed information on the extent of controls and activities already underway. Thus, costs could be overestimated because facilities may already be implementing controls to address issues (e.g., P2 programs). Without such information, it is difficult to determine whether P2 or stricter pretreatment controls would effectively reduce pollutant concentrations.
Finally, EPA cannot estimate potential costs to point sources that might be unable to commence discharging or expand existing discharges as a result of new, baseline WQS. Depending on how the proposed baseline WQS are implemented, numeric or narrative requirements may preclude some new or expanded discharges to or upstream from Indian reservation waters. The costs to such point sources may include, for example, loss of opportunity for expansion and resulting loss of revenue or the cost of identifying an alternative discharge location.
Nonpoint Sources
The lack of available in-stream monitoring data for some water bodies and the use of a single set of economic analysis criteria instead of site-dependent values (e.g., copper and other metals) prevent reliable estimation of the need for reductions in pollutant loads from nonpoint sources. In addition, the available data may not be representative of the water bodies and may be geographically biased towards more easily accessible sampling locations. Furthermore, it is difficult to quantify nonpoint source discharges because most are intermittent, variable, and occur during precipitation events. There are no CWA programs regulating nonpoint sources. Together, these limitations mean that data are too limited to reliably estimate the extent of incremental nonpoint source controls needed to attain the proposed baseline WQS.
Point Source Load Reductions
Uncertainty also exists regarding the pollutant loading reductions from point sources that would be needed to meet the economic analysis criteria. The feasibility of meeting the effluent limitations for certain pollutants and compliance mechanisms is uncertain. If the controls are not effective, then the pollutant load reductions may be limited.
Response to Requirements
For point sources, it is uncertain whether any particular control option would guarantee meeting the economic analysis criteria. For example, the effluent reductions achievable through P2 activities and the level of controls needed are highly site-specific and cannot be estimated without a detailed analysis of the facility's service area and existing plant processes and operations. 
In addition, the costs of controls are likely facility-specific and may be higher or lower than shown. Thus, it is uncertain how much system rehabilitation will cost until the source identification study is complete.
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Washington Department of Fish and Wildlife. 2016. 2015-16 Willapa Bay and Grays Harbor Fall Commercial Non Indian and Tribal Salmon Landings.
Whitehead, J. C., and G.C. Blomquist. 1991. Measuring contingent values for wetlands: effects of information about related environmental goods. Water Resources Research 27(10):2523 - 2531.
Woodward, R.T., and Y.-S. Wui. 2001. The economic value of wetland services: a meta-analysis. Ecological Economics 37(2):257 - 270.
Facility Analyses
Appendix A provides details of the facility analyses that were conducted for major facilities discharging on Tribal lands and upstream from Tribal lands. 
Sections A.1 through A.7 summarize the analyses conducted for all major facilities discharging on Tribal lands: 
 Colorado River Sewage System Joint Venture (AZ0021415)
 Mesa Northwest WRP (AZ0024627)
 Mt. Pleasant WWTP (MI0023655)
 Union Township WWTP (MI0055808)
 Pearl River WWTP (MS0053503)
 City of Hardin WTP (MT0030759)
 City of Salamanca WWTP (NY0020508)
The remaining sections (A.8 through A.26) summarize the analyses conducted for all major industrial and a sample of major sewerage facilities discharging upstream from Tribal lands:
 City of Phoenix 91[st] Avenue WWTP (AZ0020524)
 Pima County WRC - Arva Valley WRF (AZ0024121)
 Town of Florence WWTP (AZ0025208)
 Coachella Valley Water District Mid-Valley WRP (CA0104973)
 Pagosa Area Sanitation District - Vista WWTP (CO0031755)
 CF Industries Nitrogen (IA0004014)
 MidAmerican Energy - Neal North Energy Center (IA0004103)
 MidAmerican Energy - Neal South Energy Center (IA0061859)
 City of Pocatello WPCF (ID0021784)
 City of Devils Lake WWTF (ND0020681)
 MG Waldbaum Company (NE0113735)
 Los Alamos County Department of Public Utilities WWTF (NM0020141)
 Los Alamos National Laboratory (NM0028355)
 Phillips 66 Ponca City Refinery (OK0000256)
 Kenyon Industries, Inc. (RI0000191)
 Roberto R. Bustamante WWTF (TX0101605)
 McKinley Paper Company (Bio Pappel International) (WA0002925)
 Domtar A.W., LLC WRC (WI0003620)
 City of Baraboo WWTP (WI0020605)

Colorado River Sewage Joint Venture (AZ0021415)
The Colorado River Sewage Joint Venture (CRSJV; NPDES permit number AZ0021415) owns and operates the POTW servicing the Town of Parker, Arizona, and the Colorado River Indian Tribes, with a total population of approximately 5,000. The CRSJV discharges to a main drainage canal that flows out to the Colorado River. 
EPA developed this facility analysis based on the 2015 permit and supporting fact sheet issued by EPA, which are the most recent available, together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The CRSJV has a design flow of 1.2 MGD. The average daily discharge is 0.63 MGD and the maximum daily discharge is 0.8 MGD. The permit includes effluent limitations for BOD, TSS, pH, E. coli, nitrite + nitrate, arsenic, boron, fluoride, and selenium. 
The CRSJV treatment system consists of a solids grinder, contact stabilization tanks with secondary clarifiers, aerobic digesters, and ultraviolet disinfection with backup chlorination/dechlorination. Effluent solids are dried on site and sludge is hauled off to a landfill. The CRSJV does not have an approved pretreatment program but does maintain city codes and local limits to control the flow of industrial pollutants into the POTW. The POTW has indicated that there is one significant industrial discharger -- Evoqua Water Technologies. The average daily volume of process wastewater from Evoqua Water Technologies is 0.14 MGD, which represents approximately 22 percent of the POTW's total average flow of 0.63 MGD. 
Reasonable Potential Analysis
EPA had sufficient data to conduct RPA for the parameters shown in Exhibit A-1. 
Exhibit A-1: Summary of Available Effluent Data for CRSJV (ug/L)
Parameter
Effluent Data[a] 
Detection Limit (ug/L)

Samples
50[th] Percentile
Max

Arsenic
                                                                              5
                                                                              -
                                                                             10
                                                                            0.4
Zinc
                                                                              5
                                                                              -
                                                                             70
                                                                           0.05
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99th percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50th percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50th percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50th percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-2 summarizes the RPA for all parameters with sufficient data. Based on the fact sheet for the permit's facility, no dilution was considered in the development of WQBELs; therefore, EPA did not assume any dilution for this analysis. 
Exhibit A-2: Summary of Reasonable Potential Analysis for CRSJV (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Arsenic
                                                                             42
                                                                             42
                                                                            9.3
                                                                            340
                                                                            150
                                                                               
                                      No
                                      N/A
Zinc
                                                                            290
                                                                            290
                                                                             65
                                                                            120
                                                                            120
                                                                          2,600
                                      Yes
                                      No
Notes:
[a] Calculated assuming no dilution.
As shown in Exhibit A-2, the facility has reasonable potential to exceed the zinc aquatic life criteria. Exhibit A-3 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the CRSJV. 
Exhibit A-3: Summary of Limits for Parameters with Reasonable Potential (ug/L)
Parameter
Limiting Criterion
Limits[a]
Max Conc
Exceeds Limit?

AML
MDL

Zinc
                                      AL
                                      61
                                      120
                                      70
                                      Yes
Note:
[a] Calculated assuming no dilution.
Summary
The RPA indicates that the discharge has reasonable potential for zinc, but the zinc concentrations in all measured effluent samples from the limited data set are below the MDL, all but one are below the AML, and the average is below the AML. Additional sampling would confirm whether treatment (e.g., coagulation/flocculation) is necessary or if the facility is able to meet the effluent limits for zinc derived from the economic analysis criteria with a P2 program. If the facility is unable to consistently meet the AML with its existing treatment system and additional effluenteffluent treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate its best compliance option as shown in Exhibit A-4, EPA estimated the cost to this facility of applying for a WQS variance in addition to the cost of implementing a P2 program to reduce effluent concentrations of zinc.
Exhibit A-4: CRSJV Estimated Incremental Costs (1.2 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Zinc
Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

Variance Feasibility
Analysis
                                      $0
                                    $45,164
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $127,840
                                      $0
                                      $0
                                      $0
TOTAL:
                                      $0
                                   $189,561
                                      $0
                                    $9,934
                                    $9,934
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Mesa Northwest WRP (AZ0024627)
The Mesa Northwest WRP (Mesa Northwest WRP; NPDES permit number AZ0024627) is a POTW owned and operated by the City of Mesa, Arizona, and is located on the south side of the Salt River. The Mesa Northwest WRP collects and treats wastewater from a service area in northwest portion of the City of Mesa with a population of approximately 120,000. The facility has four permitted effluent discharge locations, but the discharge locations that are the subject of this permit are Outfalls 002 and 005 (the other outfalls are under a different permit). Outfalls 002 and 005 are on a portion of the Salt River that falls within Salt River Pima Maricopa Indian Community (SRPMIC) Tribal territory. As of the time of the current permit, Outfall 002 had not been constructed and was intended to be used only if other outfalls became non-operational.
EPA developed this facility analysis based on the 2019 permit and fact sheet issued by EPA, which are the most recent available, together with discharge monitoring reports with data for Outfall 005 from between 2016 and 2021.
Effluent and Treatment Process
Mesa Northwest has a facility design flow of 18 MGD. The permit includes effluent limitations for BOD, TSS, E. coli, WET-chronic (C.dubia and P.promelas), total residual chlorine, and pH. 
The Mesa Northwest WRP treatment process includes mechanical climber screens, grinding pump, primary clarification, nitrification, and de-nitrification via activated sludge process, secondary clarification, filtration, and disinfection. Water discharged to the Salt River is disinfected by ultra-violet (UV) light or with chlorination as a back-up in case the UV system is not in operation. If chlorination is used, the effluent is dechlorinated before discharge. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-5. 
Exhibit A-5: Summary of Available Effluent Data for Mesa Northwest (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             38
                                                                          ND[b]
                                                                         201[c]
                                                                              -
Ammonia
                                                                             39
                                                                             ND
                                                                          2,340
                                                                             10
Arsenic
                                                                              4
                                                                              -
                                                                            7.4
                                                                            0.4
Chromium (III)
                                                                              4
                                                                              -
                                                                           1.48
                                                                              -
Nickel
                                                                              4
                                                                              -
                                                                            5.6
                                                                            0.5
Zinc
                                                                              4
                                                                              -
                                                                           25.0
                                                                           0.05
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99th percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50th percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50th percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50th percentile calculated from the effluent data set when there are less than 10 observations.
[b] The data included both detected and non-detected concentrations. The 50[th] percentile (median) value was reported as "not detected."
[c] While the daily maximum for this facility was measured as 201 cfu/100 mL, the maximum of monthly geometric means was 10.35 cfu/100 mL.
Exhibit A-6 summarizes the RPA for all parameters with sufficient data. The analysis assumed no dilution because the NPDES permit does not authorize a mixing zone.
Exhibit A-6: Summary of Reasonable Potential Analysis for Mesa Northwest (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Ammonia
                                                                          8,600
                                                                          8,600
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Arsenic
                                                                             35
                                                                             35
                                                                              -
                                                                            340
                                                                            150
                                                                              -
                                      No
                                      N/A
Chromium (III)
                                                                            2.2
                                                                            6.0
                                                                              -
                                                                            570
                                                                             74
                                                                              -
                                      No
                                      N/A
Nickel
                                                                             26
                                                                             26
                                                                            5.8
                                                                            470
                                                                             52
                                                                            180
                                      No
                                      No
Zinc
                                                                            116
                                                                            117
                                                                             26
                                                                            120
                                                                            120
                                                                          2,600
                                      No
                                      No
Notes:
[a] Dilution factors are 1 as the NPDES Permit does not authorize a mixing zone.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, the analysis shows that the discharge has reasonable potential for two parameters, bacteria and ammonia. Exhibit A-7 summarizes the average monthly and maximum daily effluent limitations calculated as part of the RPA for Mesa Northwest. 
Exhibit A-7: Summary of Limits for Mesa Northwest for Parameters with Reasonable Potential (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                            100
                                                                              -
                                                                          10[a]
                                      No
Ammonia
                                      AL
                                                                          1,400
                                                                          5,500
                                                                          2,300
                                      Yes
Notes:
[a] While the daily maximum for this facility was measured as 201 cfu/100 mL, the maximum of monthly averages was 10.35 cfu/100 mL.
Summary
The facility operates a UV system, followed by disinfection with chlorination/dechlorination as a back-up for disinfection. Effluent data (reported as the geometric mean) indicate that this facility meets the potential limit for bacteria with its existing treatment system. 
While the effluent data available for this facility indicate that the maximum ammonia concentration exceeds the AML, the maximum concentration is below the MDL. Furthermore, the facility's current permit requirements include ammonia pH and temperature dependent "action levels" that are used to determine whether further action to address ammonia would be required. In discussing these action levels, the permit fact sheet characterizes effluent ammonia concentrations as follows:
Maximum daily value: 1.72 mg/L (1,720 ug/L), and
Average daily value: 0.18 mg/L (180 ug/L) 
Based on the effluent characterization in the current permit fact sheet and data from discharge monitoring reports, the facility's existing treatment system should be capable of meeting ammonia limits derived from the economic analysis criteria. Therefore, EPA estimated no incremental compliance cost for this facility at this time.
Mt. Pleasant WWTP (MI0023655)
The Mt. Pleasant WWWTP (Mt. Pleasant WWTP; NPDES permit number MI0023655) is located within the boundaries of the Isabella Indian Reservation in Mt. Pleasant, Michigan. The facility discharges effluent through a single outfall (Outfall 001) to the Chippewa River. 
EPA developed this facility analysis based on the 2020 permit issued by EPA together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Mt. Pleasant WWTP has a facility design flow of 4.14 MGD. The permit includes effluent limitations for carbonaceous biochemical oxygen demand (CBOD), TSS, ammonia nitrogen, total phosphorus, E. coli, total residual chlorine, cyanide, pH, and total mercury. 
Wastewater enters the plant through either a bar screen or an inline grinder, from which it is pumped into an aerated grit removal chamber where it is also undergoes treatment for phosphorus removal. The flow is then split and forwarded to five primary clarifiers. After clarification, the effluent is pumped up to the biotowers for soluble CBOD removal, from which it is then sent through a series of rotating biological contactors for further CBOD and nitrogen removal. The effluent then proceeds to a final clarifier and then through one of two chlorine contact tanks. Finally, the effluent is dechlorinated and discharged over a cascade to aerate it further before it enters the Chippewa River via Outfall 001. Sludge is sent through two anaerobic digesters in series. Supernatant is decanted and routed back to the headworks. The sludge is then stored until it undergoes land application at agronomic rates. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-8. 
Exhibit A-8: Summary of Available Effluent Data for Mt. Pleasant WWTP
Parameter
Effluent Data (cfu/100 mL)

Samples
50[th] Percentile
Max 
Bacteria (E. coli; cfu/100 mL)
                                                                             47
                                                                              4
                                                                          210 a
Note:
[a] While the daily maximum for this facility was measured as 210 cfu/100 mL, the maximum of monthly averages was 6 cfu/100 mL.
Bacteria was the only parameter for which data were available. Since there was at least one observation exceeding 100 cfu/100 mL, EPA assumed that the discharge had reasonable potential for bacteria. However, an analysis of the E. coli data shows that this facility did not exceed 6 cfu/100mL on an average monthly basis, as shown in Exhibit A-9, and would meet the effluent limit based on the economic analysis criteria.
Exhibit A-9: Summary of Limits for Mt. Pleasant for Parameters with Reasonable Potential (cfu/100 mL)
Parameter
Limiting Criterion
Limits
Max Monthly Average Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                            100
                                                                              -
                                                                            6 a
                                      No
Note:
[a] While the daily maximum for this facility was measured as 210 cfu/100 mL, the maximum of monthly averages was 6 cfu/100 mL.
Summary
EPA estimated no incremental compliance cost for this facility at this time.
Union Township WWTP (MI0055808)
The Union Township WWTP (Union Township WWTP; NPDES permit number MI0055808) is located within the boundaries of the Isabella Indian Reservation in the Charter Township of Union, Michigan. The facility discharges effluent to the Chippewa River through Outfall 001. 
EPA developed this facility analysis based on the 2017 permit and fact sheet issued by EPA, which are the most recent available, together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Union Township WWTP has a facility design flow of 2.40 MGD. The permit includes effluent limitations for E. coli, BOD, TSS, ammonia, total phosphorous, total mercury, and pH.
Influent to the treatment facility passes through screening for grit removal and flows to oxidation ditches for biological treatment. Chemicals for phosphorous removal are added after the oxidation ditches and then wastewater flows to clarifiers for settling. After clarification, the wastewater flows through a tertiary filter for polishing followed by ultraviolet light disinfection before discharging to the Chippewa River. Sludge is processed through aerobic digesters and then land applied at agronomic rates. 
Reasonable Potential Analysis
Discharge monitoring reports did not include enough data for any parameters for EPA to conduct a reasonable potential analysis.
Summary
EPA estimated no incremental compliance cost for this facility at this time.
Pearl River WWTP (MS0053503)
The Pearl River WWTP (Pearl River WWTP; NPDES permit number MS0053503) is a POTW located within the Mississippi Band of Choctaw Indians Tribal boundary. The facility discharges to Wolf Creek (which flows to the Kentawka Canal then to the Pearl River). 
EPA developed this facility analysis based on the 2015 permit issued by EPA together with discharge monitoring reports from between 2016 and 2021. The 2015 permit expired in 2019; however, it is the most recent available, and EPA assumes it is still representative of the facility's operations.
Effluent and Treatment Process
The Pearl River WWTP has a facility design flow of 1.50 MGD. The permit includes effluent limitations for CBOD, TSS, ammonia nitrogen, total recoverable copper, pH, fecal coliform bacteria, total nitrogen, and total phosphorous.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-10. 
Exhibit A-10: Summary of Available Effluent Data for Pearl River WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max 

Bacteria (E. coli; cfu/100 mL)
                                                                             21
                                                                             44
                                                                        8,000 b
                                                                            - 
Ammonia
                                                                             59
                                                                            500
                                                                          4,800
                                                                             10
Copper
                                                                             57
                                                                           12.4
                                                                           42.2
                                                                            0.5
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99th percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50th percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50th percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50th percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 8,000 cfu/100 mL and the maximum of monthly averages was 1,876 cfu/100 mL
Exhibit A-11 summarizes the RPA for all parameters with sufficient data. EPA did not have information on whether mixing zones are authorized for this facility; therefore, for this analysis, EPA assumed no dilution was available.
Exhibit A-11: Summary of Reasonable Potential Analysis for Pearl River WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Ammonia
                                                                         11,200
                                                                         11,200
                                                                            500
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Copper
                                                                             76
                                                                             76
                                                                             12
                                                                            4.4
                                                                            2.7
                                                                          1,300
                                      Yes
                                      No
Notes:
[a] No dilution was used for this analysis. 
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, bacteria, ammonia, and chlorine have reasonable potential. Exhibit A-12 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Pearl River WWTP. 
Exhibit A-12: Summary of Limits for Pearl River WWTP for Parameters with Reasonable Potential (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                            100
                                                                              -
                                                                        1,876 a
                                      Yes
Ammonia
                                      AL
                                                                          1,400
                                                                          5,000
                                                                          4,800
                                      Yes
Copper
                                      AL
                                                                            2.0
                                                                            4.4
                                                                           42.2
                                      Yes
Note:
[a] This is the maximum of the geometric mean data reported for this facility.
Summary
The facility's permit requires this facility to meet an existing seasonal monthly limit on E. coli of 200 cfu/100 mL from May to October and 400 cfu/100 mL from November to April. Effluent data indicate the current permit limits were exceeded at least twice (1,876 cfu/100 mL in July 2019, and 587 cfu/100 mL in December 2020). Other data indicate effluent meeting the proposed criteria. Once the facility optimizes its existing disinfection system to meet its current effluent limits for bacteria, it would likely also meet the limits based on proposed criteria at limited or no additional cost.
While the effluent data available for this facility indicate that it would not always meet the proposed criterion for ammonia, data also indicate that the facility has not always met its current permit requirements: 
Monthly average: 2.0 mg/L (maximum reported monthly average of 2.3 mg/L), and
Weekly average: 3.0 mg/L (maximum reported weekly average of 4.8 mg/L).
Over the past two years, however, the average monthly concentration has been below the current proposed AML. In addition, the average weekly concentration has been at or below the existing average weekly limit and below the proposed MDL. Based on the available effluent data, it appears that the current system may be able to operate to comply with the current permit limits and limits derived from the economic analysis criteria. Performing a process analysis or modeling exercise may allow the facility to identify process steps that are not performing up to the limits of the technology and assure continued compliance with the current permit limits and limits based on the economic analysis criteria. This analysis may require additional water quality testing at the facility to conduct a process analysis and identify how to modify the unit processes in the current system to perform in such a way to meet effluent limits. Modifications may include additional aeration, extended times in nitrification reactors, addition of alkalinity, enhanced solids removal, and temperature control. EPA estimated the cost to this facility of applying implementing a process modeling program, water quality monitoring, and process modifications to reduce effluent concentrations of ammonia. For purposes of this analysis, EPA estimated these costs to be similar to the costs of a P2 program for other pollutants.
The current permit also specifies daily max, monthly average, and weekly average limits for copper, which depend on hardness. Effluent data for this facility indicate that hardness is on average 60mg/L, which would translate to the following existing limits for this facility: 
Daily max: 8.7 ug/L,
Weekly average: 9.0 ug/L, and
Monthly average: 6.0 ug/L
Reported monthly averages effluent copper concentrations at this facility range from 1.0 to 19.0 ug/L, indicating that the facility is not consistently meeting its current permit requirements. Information about the current treatment system is not available. Additional active removal to remove copper may include chemical precipitation to achieve copper reductions needed to achieve WQBELs derived from the economic analysis criteria. Alternatively, the facility could implement P2 activities and apply for a variance if the limits cannot be achieved without causing substantial and widespread socioeconomic impacts. EPA estimated a range of incremental costs for the facility from implementing a P2 program and applying for a variance to adding chemical precipitation along with a P2 program to reduce effluent concentrations of copper (Exhibit A-13).
Exhibit A-13: Pearl River WWTP Estimated Incremental Costs (1.50 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934
Copper
Chemical Precipitation
                                  $1,715,000
                                      $0
                                   $452,020
                                   $567,295
                                   $613,904

Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

                  Alternative Compliance Mechanism for Copper

Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

Variance Feasibility Analysis
                                      $0
                                    $45,164
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $127,840
                                      $0
                                      $0
                                      $0
TOTAL:
                                $0 -$1,715,000
                               $33,114 -$206,118
                                     $0 -
                                   $452,020
                               $19,868 -$587,163
                               $19,868 -$633,772
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
City of Hardin WTP (MT0030759)
The City of Hardin WTP (City of Hardin WTP; NPDES permit number MT0030759) in the City of Hardin, Montana, is just north of the Crow Indian Reservation. The lagoon system that receives the wastewater from the WTP and that could potentially discharge is on the Bighorn River's west bank, within the boundary of the Crow Nation. 
EPA developed this facility analysis based on the 2016 permit and statement of basis issued by EPA, which are the most recent available, together with discharge monitoring reports from between 2016 and 2021.
 Effluent and Treatment Process
The City of Hardin WTP has a facility design flow of 2.16 MGD. The permit includes effluent limitations for TSS, total residual chlorine, total recoverable aluminum, and pH. 
Hardin's process includes treating raw water before it enters a settling basin to be clarified. The sludge in the settling basin is removed three times per week. After flocculation, sand filters process the treated water and the water is chlorinated prior to distribution. Daily backwashing processes produce 15,000 gallons of backwash each time.
Filter backwash and wastewater from the facility's Trac Vac sludge collector are sent to two lagoons/drying ponds which are divided into three cells. The WTP lagoons are located next to the WWTP for the City of Hardin. The backwash wastewater is then pumped into a settling basin and then to a second cell of the lagoon. Backwash usually infiltrates or evaporates before it reaches the third cell. If the third cell fills up, a pipe to the Bighorn River via Outfall 001 can discharge wastewater. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-14. 
Exhibit A-14: Summary of Available Effluent Data for City of Hardin WTP (ug/L)
Parameter
Effluent Dataa 
Detection Limit 

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             32
                                                                            9.0
                                                                        4,500 b
                                                                            - 
Ammonia
                                                                              2
                                                                              -
                                                                             25
                                                                             10
Arsenic
                                                                              2
                                                                              -
                                                                             ND
                                                                           0.40
Copper
                                                                              4
                                                                              -
                                                                             10
                                                                           0.50
Phenol
                                                                              1
                                                                              -
                                                                       0.005[c]
                                                                           0.14
Selenium
                                                                              1
                                                                              -
                                                                        0.03[c]
                                                                           0.60
Zinc
                                                                              2
                                                                              -
                                                                             40
                                                                           0.05
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99th percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50th percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50th percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50th percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 4,500 cfu/100 mL, the maximum of monthly averages was 594 cfu/100 mL.
[c] This value is below the DL and is based on the assumption used in this analysis that measurements reported as "<" or "not quantified" are assumed to be one-half of the DL.
Exhibit A-15 summarizes the RPA for all parameters with sufficient data. Critical low flow data used in this analysis were provided in the permit and were used to calculate dilution factors for chronic criteria only; calculations for all other criteria assume no mixing, consistent with the current permit. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criterion. 
Exhibit A-15: Summary of Reasonable Potential Analysis for City of Hardin WTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL) b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Ammonia
                                                                            185
                                                                           5.01
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      No
                                      N/A
Arsenic
                                                                            0.0
                                                                        0.20[c]
                                                                              -
                                                                            340
                                                                            150
                                                                              -
                                      No
                                      N/A
Copper
                                                                           47.4
                                                                           0.25
                                                                           10.4
                                                                            4.4
                                                                            2.7
                                                                          1,300
                                      Yes
                                      No
Phenol
                                                                              -
                                                                              -
                                                                          0.008
                                                                              -
                                                                              -
                                                                          4,000
                                      N/A
                                      No
Selenium
                                                                              -
                                                                           0.30
                                                                           0.46
                                                                              -
                                                                            1.5
                                                                            130
                                      No
                                      No
Zinc
                                                                            185
                                                                           0.03
                                                                           41.5
                                                                            120
                                                                            120
                                                                          2,600
                                      Yes
                                      No
Notes:
[a] Calculated assuming no dilution for acute aquatic life criteria and human health criteria, and full dilution (25562) for chronic aquatic life criteria.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
[c] Because dilution is considered in the analysis of the chronic criterion, the concentration at the edge of the mixing zone reflects the ambient concentration.
As shown above, bacteria, copper, and zinc have reasonable potential. Exhibit A-16 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the City of Hardin WTP. 
Exhibit A-16: Summary of Limits for City of Hardin WTP for Parameters with Reasonable Potential (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria
                                      HH
                                                                            100
                                                                              -
                                                                          594 a
                                      Yes
Copper
                                      AL
                                                                            2.2
                                                                            4.4
                                                                           47.4
                                      Yes
Zinc
                                      AL
                                                                             61
                                                                            120
                                                                             40
                                      No
Note:
[a] While the daily maximum for this facility was measured as 4,500 cfu/100 mL, the maximum of monthly average effluent concentration was 594 cfu/100 mL.
Summary
Although the RPA indicates that the discharge from this facility has reasonable potential for zinc, actual effluent sampling results for these parameters meet effluent limits for zinc derived from the proposed WQS. The facility may wish to optimize its system to ensure it continues to operate within the potential limits and should be able to do so at minimal cost. EPA estimated no incremental compliance cost for zinc for this facility at this time.
While the effluent data available for this facility indicate that it would not meet the proposed criterion for bacteria, data also indicate that the facility has not always met its existing permit requirements:
Maximum daily value: 252/1,260 cfu/100 mL in April  -  October/November  -  May, respectively, and
Average monthly: 126/630 cfu/100 mL in April  -  October/November  -  May, respectively.
The most recent data (May 2019  -  April 2021), however, indicate that the facility has met both existing and proposed limits. Facility operations in the last two years indicate that the existing facility can meet the proposed limits as currently operated. Therefore, EPA estimated no incremental compliance cost for bacteria for this facility at this time.
The limited effluent data for copper indicate that the facility may have difficulty meeting effluent limitations for copper derived from the economic analysis criteria. Two of the four effluent data points were reported as annual average copper concentrations (2016 and 2017) of 10 ug/L. However, more recent data (2018 and 2019) reported annual average concentrations less than the DL. Additional copper data would be needed to definitively determine whether the facility would be required to take steps to reduce copper concentrations. As summarized in Exhibit A-17 and for purposes of this analysis, EPA considered the recent data showing that effluent concentrations are less than the DL, but conservatively assumed that the facility may need to take additional steps to reduce copper concentrations in its effluent. EPA estimated the cost to this facility of applying for a WQS variance paired with implementing a P2 program to reduce effluent concentrations of copper.
Exhibit A-17: City of Hardin Estimated Incremental Costs (2.16 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Copper
Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

Variance Feasibility Analysis
                                      $0
                                    $45,164
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $127,840
                                      $0
                                      $0
                                      $0
TOTAL:
                                      $0
                                   $189,5661
                                      $0
                                    $9,934
                                    $9,934
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Salamanca WWTP (NY0020508)
The Salamanca WWTP (Salamanca WWTP; NPDES permit number NY0020508) in the City of Salamanca is located within the boundaries of the Allegheny Reservation in Salamanca, New York. The facility discharges effluent to the Allegheny River. 
EPA developed this facility analysis based on the 2019 permit and supporting fact sheet issued by EPA, together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Salamanca WWTP has an annual average flow of 1.62 MGD and a facility design flow of 2.00 MGD. The permit includes effluent limitations for BOD, TSS, pH, fecal coliform and total coliform, and total residual chlorine. 
Salamanca's process includes a treatment system consisting of screening, grit removal, contact stabilization, settling and, chlorination. Sludge undergoes aerobic digestion. Biosolids from secondary gravity thickeners are injected subterraneously on permitted land or thickened and pressed for disposal to landfill. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-18. 
Exhibit A-18: Summary of Available Effluent Data for Salamanca WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit 

Samples
50[th] Percentile
Max

Bacteria (fecal coliform; cfu/100 mL)
                                                                             23
                                                                             10
                                                                       26,000 b
                                                                            - 
Chlorine
                                                                             29
                                                                          1,000
                                                                          1,500
                                                                             10
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99th percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50th percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50th percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50th percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 26,000 cfu/100 mL, the maximum of monthly average effluent concentration was 4,282 cfu/100 mL.
Exhibit A-19 summarizes the RPA for all parameters with sufficient data using a dilution factor of 5.0 for chlorine consistent with the NPDES permit fact sheet. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criteria, which is conservative assumption for chlorine. 
Exhibit A-19: Summary of Reasonable Potential Analysis for Salamanca WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)[b]
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                                                               
                                      N/A
                                      Yes
Chlorine
                                                                           370 
                                                                           370 
                                                                               
                                                                             19
                                                                             11
                                                                               
                                      Yes
                                      N/A
Notes:
[a] Calculated using a dilution factor of 5.0 for chlorine.
[b] For bacteria, EPA assessed fecal coliform data against the proposed E. coli value. E. coli is a species of fecal coliform; therefore, this assessment is conservative. The facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, both bacteria and chlorine have reasonable potential. Exhibit A-20 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Salamanca WWTP. 
Exhibit A-20: Summary of Limits for Salamanca WWTP for Parameters with Reasonable Potential (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli, cfu/100 mL)
                                      HH
                                                                            100
                                                                               
                                                                        4,282 a
                                      Yes
Chlorine
                                      AL
                                                                             33
                                                                             42
                                                                          1,500
                                      Yes
Note:
[a] The value is the maximum of the geometric means of fecal coliform data reported for this facility.
Summary
The Salamanca WWTP's permit specifies an average monthly limit of 200 cfu/100 mL (fecal coliform). The facility's fecal coliform concentration exceeded both the existing (fecal coliform) and proposed (E. coli) limits for bacteria in June 2018 (1,398 cfu/100 mL) and July 2018 (4,282 cfu/100 mL), but the next highest maximum monthly average effluent concentration was 17 cfu/100 mL, which indicates that the existing facility can meet effluent limits derived from the economic analysis criteria as currently operated. Therefore, EPA estimated no incremental compliance cost for bacteria for this facility at this time.
The facility has a current daily maximum effluent limit for chlorine of 1.3 mg/L and has consistently met that limit since it was exceeded one time in June 2016. However, the facility would not meet the WQBELs for chlorine derived from the economic analysis criteria as currently operated. The facility may need to add dechlorination in order to meet these WQBELs. Exhibit A-21 summarizes EPA's estimated costs for adding dechlorination to the current treatment system.
Exhibit A-21: Salamanca WWTP Estimated Incremental Costs (2.00 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Chlorine
Dechlorination
                                  $1,020,000
                                      $0
                                    $46,370
                                   $114,930
                                   $142,651
TOTAL:
                                  $1,020,000
                                      $0
                                    $46,370
                                   $114,930
                                   $142,651
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
City of Phoenix 91[st] Avenue WWTP (AZ0020524)
The City of Phoenix operates a WWTP at 91[st] Avenue in Tolleson, Arizona (City of Phoenix WWTP; NPDES permit number AZ0020524). The WWTP services a population of over 2 million residents in Glendale, Mesa, Phoenix, Scottsdale, and Tempe, in Maricopa County. The facility discharges into the Salt River. 
EPA developed this facility analysis based on the 2016 permit and fact sheet issued by EPA together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The City of Phoenix 91[st] Avenue WWTP has a design facility flow of 230 MGD and an annual average discharge rate that ranges between 40 and 130 MGD. The permit includes effluent limitations for CBOD, BOD, E. coli, pH, TSS, ammonia, dissolved oxygen, and chlorine.
The City of Phoenix WWTP consists of seven individual activated sludge WWTPs operated in parallel that merge before dechlorination and discharge. Each WWTP includes the following unit processes: screening, grit removal, flow measurement/flow distribution, primary sedimentation (with enhanced sedimentation possible), activated sludge biological treatment, secondary clarification, chlorine disinfection, centrifuge thickening of primary sludge and waste activated sludge, anaerobic sludge digestion, sludge drying beds, and centrifuge dewatering of digested sludge. Effluent flows to either constructed wetlands (70 MGD), the Palo Verde Nuclear Power Plant (70 MGD), or to the Salt River via the Tres Rios Flow Regulating Wetlands (FRW), discharged through Outfall 005. This analysis focuses on discharges from Outfall 005 to the Salt River. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-22. 
Exhibit A-22: Summary of Available Effluent Data for City of Phoenix WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit 

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             25
                                                                            5.0
                                                                        1,414 b
                                                                            - 
Ammonia
                                                                             10
                                                                          1,250
                                                                          2,100
                                                                             10
Barium
                                                                             11
                                                                             35
                                                                             49
                                                                            0.8
Chlorine
                                                                             61
                                                                          ND[c]
                                                                             25
                                                                             10
Chloroform
                                                                             10
                                                                           1.65
                                                                            2.5
                                                                           0.01
Cyanide
                                                                             61
                                                                            2.5
                                                                             11
                                                                              5
Endosulfan Sulfate
                                                                             48
                                                                             ND
                                                                       0.035[d]
                                                                           0.07
Manganese
                                                                             11
                                                                            520
                                                                           70.3
                                                                            0.1
Methylene Chloride
                                                                              3
                                                                              -
                                                                           1.00
                                                                           0.02
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 1,414 cfu/100 mL, the maximum of monthly averages was 265 cfu/100 mL.
[c] The data included both detected and non-detected concentrations. The 50th percentile (median) value was reported as "not detected."
[d] This value is below the DL and is based on the assumption used in this analysis that measurements reported as "<" or "not quantified" are one-half of the DL.
Exhibit A-23 summarizes the RPA for all parameters with sufficient data. Based on the fact sheet for the permit's facility, no dilution was considered in the development of water quality-based effluent limits; as such, EPA did not use dilution for this analysis.
Exhibit A-23: Summary of Reasonable Potential Analysis for City of Phoenix WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Ammonia
                                                                          4,200
                                                                          4,200
                                                                               
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Barium
                                                                              -
                                                                              -
                                                                             35
                                                                              -
                                                                              -
                                                                          1,000
                                      N/A
                                      No
Chlorine
                                                                            126
                                                                            126
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Chloroform
                                                                              -
                                                                              -
                                                                           1.65
                                                                              -
                                                                              -
                                                                             60
                                      N/A
                                      No
Cyanide
                                                                             16
                                                                             16
                                                                            2.5
                                                                             22
                                                                            5.2
                                                                            4.0
                                      Yes
                                      No
Endosulfan Sulfate
                                                                              -
                                                                              -
                                                                            0.0
                                                                              -
                                                                              -
                                                                            5.0
                                      N/A
                                      No
Manganese
                                                                              -
                                                                              -
                                                                             52
                                                                              -
                                                                              -
                                                                             50
                                      N/A
                                      Yes
Methylene Chloride
                                                                            5.6
                                                                            5.6
                                                                            1.2
                                                                              -
                                                                              -
                                                                             20
                                      N/A
                                      No
Notes:
a No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, five parameters (bacteria, ammonia, chlorine, cyanide, and manganese) have reasonable potential. Exhibit A-24 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the City of Phoenix WWTP. 
Exhibit A-24: Summary of Calculated Limits for Parameters with Reasonable Potential for City of Phoenix WWTP (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                            100
                                                                              -
                                                                         265[a]
                                      Yes
Ammonia
                                      AL
                                                                          1,400
                                                                          2,500
                                                                          2,100
                                      Yes
Chlorine
                                      AL
                                                                            4.0
                                                                             14
                                                                             25
                                      Yes
Cyanide
                                      AL
                                                                            4.5
                                                                            7.9
                                                                             11
                                      Yes
Manganese
                                      HH
                                                                             50
                                                                             64
                                                                             70
                                      Yes
Note:
[a] While the daily maximum for this facility was measured as 1,414 cfu/100 mL, the maximum of monthly average effluent concentration was 265 cfu/100 mL.
Summary
The City of Phoenix's permit specifies an average monthly limit of 126 cfu/100 mL, and a daily average of 575 cfu/100 mL for E. coli. Maximum monthly effluent data indicate that the facility does not always meet its existing effluent limits or limit derived from the economic analysis criterion for bacteria; however, the data show a significant reduction in monthly effluent concentrations between 2016 (range of 51 to 265 cfu/100mL) to recent months (January 2020 to April 2021) where the monthly average effluent concentration was reported as 1 cfu/100 mL with a range of daily maxima from 1 to 12 cfu/100mL. These data indicate that the existing facility can meet the effluent limit based on the economic analysis criterion as currently operated. Therefore, EPA estimated no incremental compliance cost for bacteria for this facility at this time.
The facility meets its current ammonia permit requirement of 2.2 to 2.7 mg/L daily. Ammonia effluent data were only available for 2016. At the time, the monthly average effluent concentration ranged from 0.4 to 1.5 mg/L, with an average of 1.0 mg/L, and the daily maximum ranged from 0.5 to 2.1 mg/L, with an average of 1.3 mg/L. The facility could optimize its treatment system to meet the effluent limits derived from the economic analysis criteria. EPA estimated no incremental compliance cost for ammonia for this facility at this time.
The facility consists of seven individual activated sludge WWTPs operated in parallel that merge before dechlorination and discharge. With the exception of two measured values, all chlorine effluent data were reported as non-detect. Effluent chlorine concentrations were reported as 0.6 and 0.83 mg/L for the monthly average, and 19.0 and 25.0 mg/L for the maximum daily in January and September 2016, respectively. Chlorine concentrations have been reported as non-detect since then. These data indicate that the existing facility can meet effluent limits derived from the economic analysis criteria as currently operated. Therefore, EPA estimated no incremental compliance cost for chlorine for this facility at this time.
Data for cyanide are mostly reported as non-detect. Two of the three numeric monthly average effluent concentrations and daily maxima meet the effluent limits; one measurement does not. The 2016 factsheet notes that the plant has been complying with the permit limits except for exceedances of cyanide levels at FRW-1, a monitoring station at the influent to wetlands. The City of Phoenix conducted investigations to understand and mitigate the exceedances and demonstrated to the satisfaction of EPA that these were likely caused by singular events unrelated to the underlying water quality of the effluent. (Note that the permit was issued by EPA because of unresolved jurisdictional issues.) Of the three measurements that occurred since 2016, only one exceeded the limits. This single exceedance in 2018 is consistent with EPA's pre-2016 findings. Therefore, EPA estimated no incremental compliance cost for cyanide for this facility at this time. 
The facility reported three maximum daily concentrations for manganese in 2016, ranging from 49.9 ug/L (below both the AML and MDL) to 70.2 ug/L (above both the AML and MDL). Eight measurements (taken twice per year) have been reported since then with manganese concentrations ranging from 36.2 to 63.0 ug/L with an average of 53.0 ug/L. Removal using potassium permanganate as a catalyst for oxidation has shown promising results; however, it is not clear that additional treatment for manganese would be needed for the facility to comply with effluent limits derived from the economic analysis criteria. EPA estimated a range of costs to address manganese. On the lower end of the range of costs is implementing a P2 program. The upper end of the range is, in addition to a P2 program, the estimated cost of additional treatment by adding chemical precipitation to the treatment system, which would have similar costs as oxidation for manganese removal using potassium permanganate and which can be estimated using the selected cost estimation software. EPA assumed that the City of Phoenix WWTP could use its existing primary clarifiers for chemical precipitation. The estimated costs are summarized in Exhibit A-25. 
Exhibit A-25: City of Phoenix WWTP Estimated Incremental Costs (230 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Manganese
Chemical Precipitation
                                  $28,600,000
                                      $0
                                   $992,000
                                  $2,914,369
                                  $3,691,638

Large Facility P2 Program
                                      $0
                                    $49,672
                                      $0
                                    $20,973
                                    $20,973

                Alternative Compliance Mechanism for Manganese

Large Facility P2 Program
                                      $0
                                    $49,672
                                      $0
                                    $20,973
                                    $20,973
TOTAL:
                               $0 - $28,600,000
                                    $49,672
                                 $0 - $992,000
                             $20,973 - $2,935,342
                             $20,973 - $3,712,611
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Pima County WRC - Arva Valley WRF (AZ0024121)
The Pima County Regional Wastewater Reclamation Department's Arva Valley Wastewater Reclamation Facility (Pima County Arva Valley WRF; NPDES permit number AZ0024121) is a POTW located approximately 10 miles southwest of Tucson, Arizona, and upstream from the Pasqua Yaqui Indian Reservation. The receiving water for the Pima County outfalls is Black Wash, tributary of Brawley Wash, which flows into the Santa Cruz River Basin. The POTW has a service population of approximately 17,370 people within the unincorporated areas of Pima County and the Pasqua Yaqui Indian Reservation. 
EPA developed this facility analysis based on the draft 2019 permit and fact sheet issued by the Arizona Department of Environmental Quality together with discharge monitoring reports from between 2016 and 2021. EPA assumes that these draft documents are representative of current permits.
Effluent and Treatment Process
The Pima County Arva Valley WRF has a facility design flow of 4.0 MGD. The permit includes effluent limitations for BOD, TSS, pH, E. coli, and total residual chlorine.
The treatment processes at the Pima County Arva Valley WRF consist of a biological nutrient removal oxidation ditch (BNROD), screening, secondary clarification, tertiary filtering and UV disinfection with possible, occasional chlorination disinfection (used when basin maintenance is required and or as an emergency backup system substitute for UV disinfection if required). The sludge handling facility consists of a sludge-holding tank, waste sludge thickener, and a sludge loading station. Thickened waste sludge is hauled by tanker truck to a Pima County conveyance system manhole that flows to the Agua Nueva WRF for further processing prior to land application. 
Reasonable Potential Analysis
The available monitoring data for the facility indicates that there have been no discharges to surface water of any pollutant of concern for this analysis between 2016 and 2020.
Summary
EPA assumes that there will be no incremental costs for this facility.
Town of Florence WWTP (AZ0025208)
Located in Pinal County, Arizona, the Town of Florence South WWTP (NPDES permit number AZ0025208) is a major NPDES facility that treats domestic wastewater from commercial and residential sources. The POTW's service area includes a population of 11,000 people in the Tohono O'odham Tribe Town of Florence on the Florence Village Reservation, in addition to the Florence Prison System. Effluent limitations seek to maintain the Water Quality Standards listed in Arizona Administrative Code (A.A.C.) R18-11-101 et. seq. 
EPA developed this facility analysis based on the draft 2020 permit and fact sheet from the Arizona Department of Environmental Quality, together with discharge monitoring reports from between 2016 and 2021. EPA assumes that these documents are representative of current facility operations.
Effluent and Treatment Process
The facility has a design flow of 2.5 MGD. It intermittently discharges treated effluent into an irrigation ditch for local agricultural use, recharges the effluent into on-site recharge containers, or discharges the effluent into the facility's receiving water, the Gila River, via Outfall 001. Treatment processes entail influent screening; grit removal; three (3) sequencing batch reactors (SBRs) using aeration, anoxic reaction, settling, and decanting; effluent equalization basin; reuse pump station; and three (3) recharge basins. The treated effluent passes through an ultra-violet (UV) contact chamber for disinfection; the chamber has a chlorination system as a backup. 
Sludge is treated in aerobic sludge digesters, pressed, and then disposed of at the local Apache Junction Landfill Corporation.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for E. coli, ammonia, chlorine, chloroform, cyanide, dichlorobromomethane, selenium, and zinc (shown in Exhibit A-26). 
Exhibit A-26: Summary of Available Effluent Data for Town of Florence WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Maximum

Bacteria (E. coli; cfu/100 mL)
                                                                             51
                                                                           6.0 
                                                                      2,420[b] 
                                                                            - 
Ammonia
                                                                             20
                                                                           405 
                                                                         3,140 
                                                                             10
Chlorine
                                                                             62
                                                                         ND[c] 
                                                                        0.03[c]
                                                                             10
Chloroform
                                                                              3
                                                                             - 
                                                                          8.46 
                                                                           0.01
Cyanide
                                                                             19
                                                                         ND[d] 
                                                                           7.0 
                                                                              5
Chlorodibromomethane
                                                                              3
                                                                             - 
                                                                          16.2 
                                                                         0.0001
Selenium
                                                                             20
                                                                          0.30 
                                                                           2.5 
                                                                            0.6
Zinc
                                                                              9
                                                                              -
                                                                            63 
                                                                           0.05
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 2,420 cfu/100 mL, the maximum of monthly averages was 6.58 cfu/100 mL.
c Reported value is below the DL.
[d] The data included both detected and non-detected concentrations. The 50th percentile (median) value was reported as "not detected."
Exhibit A-27 summarizes the RPA for all parameters with sufficient data. Based on the fact sheet for the facility's current permit, mixing zones are not authorized, so EPA assumed no dilution was available for purposes of this analysis.
Exhibit A-27: Summary of Reasonable Potential Analysis for Town of Florence WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                             --
                                                                             --
                                                                             --
                                                                             --
                                                                             --
                                                                             --
                                      N/A
                                      Yes
Ammonia
                                                                         17,700
                                                                         17,700
                                                                               
                                                                        11,000 
                                                                         1,400 
                                                                              -
                                      Yes
                                      N/A
Chlorine
                                                                           0.10
                                                                           0.10
                                                                               
                                                                             19
                                                                             11
                                                                              -
                                      No
                                      N/A
Chloroform
                                                                           47.6
                                                                           47.6
                                                                           10.2
                                                                               
                                                                               
                                                                             60
                                      N/A
                                      No
Cyanide
                                                                           36.2
                                                                           36.2
                                                                            NDc
                                                                             22
                                                                            5.2
                                                                            4.0
                                      Yes
                                      No
Chlorodibromomethane
                                                                           91.1
                                                                           91.1
                                                                           19.5
                                                                              -
                                                                              -
                                                                           0.66
                                      N/A
                                      Yes
Selenium
                                                                              -
                                                                           13.1
                                                                             ND
                                                                               
                                                                            1.5
                                                                            130
                                      Yes
                                      No
Zinc
                                                                            195
                                                                            196
                                                                             46
                                                                            120
                                                                            120
                                                                           2600
                                      Yes
                                      No
Notes:
[a] No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
[c] The data included both detected and non-detected concentrations. The 50th percentile (median) value was reported as "not detected."
As shown above, six parameters (bacteria, ammonia, cyanide, chlorodibromomethane, selenium, and zinc) have reasonable potential. Exhibit A-28 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Town of Florence WWTP. 
Exhibit A-28: Summary of Calculated Limits for Parameters with Reasonable Potential for Town of Florence WWTP (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL) 
                                      HH
                                                                            100
                                                                             --
                                                                         6.58 a
                                      No
Ammonia
                                      AL
                                                                          1,400
                                                                          5,500
                                                                          3,140
                                      Yes
Cyanide
                                      AL
                                                                            3.3
                                                                            9.6
                                                                            7.0
                                      Yes
Chlorodibromomethane
                                      HH
                                                                           0.66
                                                                            1.3
                                                                             16
                                      Yes
Selenium
                                      AL
                                                                            1.5
                                                                            5.9
                                                                            2.5
                                      Yes
Zinc
                                      AL
                                                                             61
                                                                            120
                                                                             63
                                      Yes
Note:
[a] While the daily maximum for this facility was measured as 2419.50 cfu/100 mL, the maximum of monthly average effluent concentration was 6.58 cfu/100 mL
Summary
This facility's permit specifies an average monthly limit of 126 cfu/100 mL, and a daily average of 575 cfu/100 mL for E. coli. Monthly average effluent data indicate that this facility met its existing monthly average effluent limits and limit derived from the economic analysis criterion for bacteria from 2016 to present. The facility data also show a significant reduction in daily effluent concentrations after 2016 (January 2017 to March 2021, range of 0 to 130 cfu/100mL). In the most recent months (January 2020 to April 2021) the monthly average effluent concentration was reported as 3 cfu/100 mL with a range of daily maxima from 0 to 8 cfu/100mL during that same period (only 3 measurements during that period were above 0). These data indicate that the existing facility can meet the effluent limit based on the economic analysis criterion as currently operated. Therefore, EPA estimated no incremental compliance cost for bacteria for this facility at this time.
The facility would meet the ammonia MDL of 5.5 mg/L derived from the economic analysis criteria; the daily maximum concentrations also meet the proposed AMD of 1.4 mg/L in all but one month. Based on the available effluent data, it appears that the current system may be able to operate to achieve WQBELs derived from the economic analysis criteria. Performing a process analysis or modeling exercise may allow the facility to identify process steps that are not consistently performing up to the limits of the technology and to assure compliance. For effluent ammonia concentration reductions, this analysis may require additional water quality testing at the facility to conduct a process analysis and identify how to modify the unit processes in the current system to perform in such a way as to meet effluent limits. Modifications may include additional aeration, extended times in nitrification reactors, addition of alkalinity, enhanced solids removal, and temperature control. EPA estimated the cost to this facility of implementing a process modeling program, water quality monitoring, and process modifications to reduce effluent concentrations of ammonia. For purposes of this analysis, EPA estimated these costs to be similar to the costs of a P2 program that might be implemented for other pollutants.
Data for cyanide are mostly reported as non-detect. Of the measurements taken since 2016, none exceeded the MDL of 9.6 ug/L, but 5 of the 19 measurements exceeded the AML of 3.3 ug/L. Additional sampling would confirm whether treatment such as GAC adsorption to remove cyanide is necessary for this facility or if the facility may be able to meet the cyanide WQBELs derived from the economic analysis criteria with a P2 program. If the facility is unable to consistently comply with the MDL and AML and additional treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate the its best compliance options, which may include addition of adsorption to remove cyanide. As shown in Exhibit A-29, EPA estimated the cost to this facility of applying for a WQS variance and implementing a P2 program to reduce effluent concentrations of cyanide and, at the upper end of the range of costs, the cost of adding adsorption to the treatment system along with a P2 program.
Exhibit A-29: Town of Florence WWTP Estimated Incremental Costs (2.5 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Small Facility Process Analysis
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934
Cyanide and Selenium
Adsorption
                                  $5,944,000
                                      $0
                                   $317,849
                                   $717,379
                                   $878,921

Small Facility P2 Program
                                      $0
                                    $33,144
                                      $0
                                    $19,868
                                    $19,868

           Alternative Compliance Mechanism for Cyanide and Selenium

Small Facility P2 Program
                                      $0
                                    $33,144
                                      $0
                                    $19,868
                                    $19,868

Variance Feasibility
Analysis
                                      $0
                                    $90,328
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $255,680
                                      $0
                                      $0
                                      $0
TOTAL:
                                $0 - $5,944,000
                              $49,701 - $395,709
                                 $0 - $317,849
                              $29,802 - $747,181
                              $29,802 - $908,723
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Data for chlorodibromomethane show that effluent concentrations exceed the MDL and AML. The data ranged 2.27 ug/L to 16.20 ug/L and averaged 9.17 ug/L. Treatment of trihalomethanes (THMs), like chlorodibromomethane, in wastewater can often be controlled at minimal cost by managing chlorination, such as reducing chlorine contact time, limiting sunlight exposure to the chlorine contact chamber, and modifying the pH. Reducing the precursors to the formation of THMs, however, can be far costlier in the wastewater treatment process using activated carbon, ion exchange, or membrane filtration. Since there are operational changes that can reduce the formation of chlorodibromomethane, EPA estimated no incremental compliance cost for chlorodibromomethane for this facility at this time.
Selenium data show 2 exceedances of the AML for selenium (1.5 ug/L) derived from the economic analysis criteria from 21measurements taken from 2016 to 2021; however, the average of daily maximum selenium concentrations was 0.46 ug/L and the maximum value was 2.5 ug/L. The maximum daily limit of 5.9 ug/L was not exceeded during this monitoring period. The facility may be able to meet the selenium effluent limits derived from the economic analysis criteria with a P2 program. If the facility is unable to consistently comply with the MDL and AML and additional treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate the its best compliance options. In addition, if activated carbon adsorption is added for cyanide removal, an additional benefit of the treatment process is removal of selenium. Therefore, EPA estimated a range of cost for compliance with selenium limits derived from the potential baseline WQS. These estimates include the cost of a P2 program and variance application or a P2 program and treatment, with no incremental compliance cost for treatment if an activated carbon adsorption unit is used for both cyanide and selenium removal.
Data for zinc ranged from 0.03 to 63 ug/L for the daily maximum. Of the concentrations reported since 2016, none exceeded the MDL of 120 ug/L and only 1 of the 9 daily measurements exceeded the AML of 61 ug/L (reported at 63 ug/L). EPA estimated no incremental compliance cost for additional zinc removal for this facility at this time.
Coachella Valley Water District Mid-Valley WRP (CA0104973)
The Coachella Valley Water District Mid-Valley WRP No. 4 (Coachella Mid-Valley WRC; NPDES permit number CA0104473) is located in the Riverside County, California,. The facility serves a population of approximately 63,000 in the City of La Quinta and surrounding areas and discharges treated municipal wastewater to the Coachella Valley Storm Water Channel.
EPA developed this facility analysis based on the 2012 permit and fact sheet issued by the Colorado River Basin Regional Water Quality Control Board together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Coachella Mid-Valley WRC has a treatment capacity of 9.9 MGD. The permit includes effluent limitations for CBOD, TSS, pH, cyanide, selenium, chlorine, and E. coli.
The treatment system includes consists of two treatment systems running in parallel; a lagoon
treatment system (7.0 MGD) and an activated sludge treatment system (2.9 MGD). The headworks system includes two pre-aeration ponds, automatic bar screens, conveyor, a washer-compactor, and a headworks building equipped with an air scrubber. Flow from the headworks is distributed to five treatment modules. Four of the treatment modules are part of the lagoon treatment system and one treatment module is part of the activated sludge treatment system. Each of the four lagoon treatment modules are comprised of four lined aerated lagoons and two lined polishing ponds (for a total of 16 aeration lagoons and 8 polishing ponds). All ponds are lined with a synthetic membrane liner. The activated sludge treatment system consists of two
activated sludge basins, two secondary clarifiers, and sludge handling facilities (including a gravity belt thickener and belt filter press). Combined effluent from the two systems is disinfected and dechlorinated, prior to discharge into the Coachella Valley Storm Water Channel.
Reasonable Potential Analysis
EPA had sufficient data from 2015 to 2020 to conduct reasonable potential analyses for the parameters shown in Exhibit A-30. 
Exhibit A-30: Summary of Available Effluent Data for Coachella Mid-Valley WRC (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             61
                                                                       < 1.8
                                                                          130 b
                                                                            - 
4-4'-DDT
                                                                              1
                                                                              -
                                                                           0.05
                                                                         0.0120
alpha-BHC
                                                                              1
                                                                               
                                                                           0.01
                                                                              -
alpha-Endosulfan
                                                                              1
                                                                              -
                                                                           0.01
                                                                          0.014
Ammonia
                                                                             28
                                                                           1800
                                                                           9400
                                                                             10
Arsenic
                                                                              3
                                                                              -
                                                                            2.5
                                                                            0.4
Chloride
                                                                              5
                                                                              -
                                                                        100,000
                                                                              4
Chlorodibromomethane
                                                                              6
                                                                              -
                                                                            2.6
                                                                          0.001
Chloroform
                                                                              9
                                                                              -
                                                                             42
                                                                           0.01
Chromium (III)
                                                                              3
                                                                              -
                                                                            2.3
                                                                              -
Chromium (VI)
                                                                              2
                                                                              -
                                                                           0.08
                                                                            0.3
Copper
                                                                              5
                                                                              -
                                                                             13
                                                                            0.5
Dichlorobromomethane
                                                                              9
                                                                              -
                                                                             12
                                                                          0.003
Nickel
                                                                              2
                                                                              -
                                                                            1.8
                                                                            0.5
Selenium
                                                                             17
                                                                           1.35
                                                                            2.2
                                                                            0.6
Silver
                                                                              1
                                                                              -
                                                                           0.52
                                                                            0.1
Solids, Dissolved and Salinity
                                                                             61
                                                                        497,000
                                                                        540,000
                                                                              -
Toluene
                                                                              1
                                                                              -
                                                                            1.0
                                                                           0.01
Zinc
                                                                              5
                                                                              -
                                                                           45.7
                                                                           0.05
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 130 cfu/100 mL, the maximum of monthly averages was not quantified (<1.8 cfu/100 mL).
In addition, all data for chlorine and cyanide were reported as below the DLs.
Exhibit A-31 summarizes the RPA for all parameters with sufficient data. The analysis assumes no dilution, as the permit does not authorize mixing zones for this POTW based on the nature of the receiving water and the nature of the effluent.
Exhibit A-31: Summary of Reasonable Potential Analysis for
Coachella Mid-Valley WRC (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
4-4'-DDT
                                                                              -
                                                                              -
                                                                          0.050
                                                                              -
                                                                              -
                                                                       0.000004
                                      N/A
                                      Yes
alpha-BHC
                                                                              -
                                                                              -
                                                                          0.010
                                                                              -
                                                                              -
                                                                       0.000058
                                      N/A
                                      Yes
alpha-Endosulfan
                                                                              -
                                                                              -
                                                                          0.010
                                                                              -
                                                                              -
                                                                              4
                                      N/A
                                      No
Ammonia
                                                                         29,200
                                                                         29,200
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Arsenic
                                                                           13.2
                                                                           13.2
                                                                              -
                                                                            340
                                                                            150
                                                                              -
                                      No
                                      N/A
Chloride
                                                                        419,000
                                                                        419,000
                                                                              -
                                                                        860,000
                                                                        230,000
                                                                              -
                                      Yes
                                      N/A
Chlorodibromomethane
                                                                              -
                                                                              -
                                                                           1.60
                                                                              -
                                                                              -
                                                                           0.66
                                      No
                                      Yes
Chloroform
                                                                              -
                                                                              -
                                                                           20.1
                                                                              -
                                                                              -
                                                                             60
                                      N/A
                                      No
Chromium (III)
                                                                           12.9
                                                                           12.9
                                                                              -
                                                                            570
                                                                             74
                                                                              -
                                      No
                                      N/A
Chromium (VI)
                                                                           0.59
                                                                           0.59
                                                                              -
                                                                             16
                                                                             11
                                                                              -
                                      No
                                      N/A
Copper
                                                                           61.6
                                                                           61.6
                                                                           8.33
                                                                            4.4
                                                                            2.7
                                                                          1,300
                                      Yes
                                      No
Dichlorobromomethane
                                                                              -
                                                                              -
                                                                           5.24
                                                                              -
                                                                              -
                                                                           0.79
                                      N/A
                                      Yes
Nickel
                                                                           13.3
                                                                           13.3
                                                                           1.70
                                                                            470
                                                                             52
                                                                            180
                                      No
                                      No
Selenium
                                                                              -
                                                                            3.3
                                                                           1.35
                                                                              -
                                                                            1.5
                                                                            130
                                      Yes
                                      No
Silver
                                                                           6.86
                                                                              -
                                                                              -
                                                                            3.2
                                                                              -
                                                                              -
                                      Yes
                                      N/A
Solids, Dissolved and Salinity
                                                                              -
                                                                              -
                                                                        497,000
                                                                              -
                                                                              -
                                                                        250,000
                                      N/A
                                      Yes
Toluene
                                                                              -
                                                                              -
                                                                            1.0
                                                                              -
                                                                              -
                                                                             35
                                      N/A
                                      No
Zinc
                                                                            155
                                                                            155
                                                                           32.8
                                                                            120
                                                                            120
                                                                          2,600
                                      Yes
                                      No
Notes:
[a] No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, 12 parameters have reasonable potential. Exhibit A-32 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for Coachella Mid-Valley WRP. The analysis shows a need for reductions of bacteria, chlorodibromomethane, copper, dibenzo(a,h) anthracene, dichlorobromomethane, and ideno(1,2,3-cd) pyrene in the discharge in order to comply with effluent limits derived from the proposed WQS. 
Exhibit A-32: Summary of Calculated Limits for Parameters with Reasonable Potential for Coachella Mid-Valley WRC (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria 
                                      HH
                                                                            100
                                                                            N/A
                                                                          1.8 a
                                      No
4-4'-DDT
                                      HH
                                                                      0.0000040
                                                                      0.0000080
                                                                           0.05
                                      Yes
alpha-BHC
                                      HH
                                                                       0.000058
                                                                        0.00012
                                                                           0.01
                                      No
Ammonia
                                      AL
                                                                          1,400
                                                                          4,800
                                                                          9,400
                                      Yes
Chloride
                                      AL
                                                                        190,000
                                                                        380,000
                                                                        100,000
                                      No
Chlorodibromomethane
                                      HH
                                                                           0.66
                                                                            1.3
                                                                            2.6
                                      Yes
Copper
                                      AL
                                                                            2.2
                                                                            4.4
                                                                             13
                                      Yes
Dichlorobromomethane
                                      HH
                                                                           0.79
                                                                            1.6
                                                                             12
                                      Yes
Selenium
                                      AL
                                                                            1.5
                                                                            2.0
                                                                            2.2
                                      Yes
Silver
                                      AL
                                                                            1.9
                                                                            3.8
                                                                           0.52
                                      No
Solids, Dissolved and Salinity
                                      HH
                                                                        250,000
                                                                        270,000
                                                                        540,000
                                      Yes
Zinc
                                      AL
                                                                             61
                                                                            120
                                                                           45.7
                                      No
Note:
[a] While the daily maximum for this facility was measured as 170 cfu/100 mL, the maximum of monthly average effluent concentration was < 1.8 cfu/100 mL.
Summary
Although the RPA indicates that the discharge from this facility has reasonable potential for bacteria, alpha-BHC, chloride, silver, and zinc, the maximum effluent concentrations do not exceed the AMLs or MDL. 
DMR data show that effluent ammonia concentrations average 2,15 mg/L and ranged from 0.30 to 9.4 mg/L during the monitoring period that included 26 samples. The effluent limits derived from the economic analysis criteria are an AML of 1.4 mg/L and MDL of 4.8 mg/L. A facility upgrade may be necessary to meet these limits. EPA estimated the cost of adding a nitrification step to the existing treatment process.
Data for chlorodibromomethane and dichlorobromomethane show that the effluent routinely exceeds the AML and MDL derived from the economic analysis criteria. Treatment of THMs, like dichlorobromomethane and chlorodibromomethane, in wastewater can often be controlled at minimal cost by managing chlorination, such as through reducing chlorine contact time, limiting sunlight exposure to the chlorine contact chamber, and modifying the pH. Reducing the precursors to the formation of THMs, however, can be far costlier in the wastewater treatment process using activated carbon, ion exchange, or membrane filtration. Since there are operational changes that can reduce the formation of THMs, EPA estimated no incremental compliance cost for dichlorobromomethane or chlorodibromomethane for this facility at this time.
Analysis of copper data indicate that the concentration in all but 4 of the 5 available samples exceeds the AML of 2.2 ug/L and 3 of the 5 exceed the MDL of 4.4 ug/L. Selenium data indicate a range of concentrations from 1.0 to 2.2 ug/L. While only 1 of 17 data points exceeds the MDL of 2.0 ug/L, 3 exceed the AML of 1.5 ug/L. EPA estimated the incremental costs of a P2 program for copper and selenium along with additional treatment using chemical precipitation to meet effluent limits based on the economic analysis criteria. If the facility is unable to consistently comply with the MDLs and AMLs for copper and selenium and additional treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate the its best compliance options. For this analysis, EPA assumed that the facility would implement a P2 program and apply for a variance for copper and selenium and estimated the cost of this alternative compliance mechanism.
The limited effluent data for 4,4'-DDT include 4 values reported as below the DL and 1 value reported as 0.05 ug/L. Additional data would be needed to determine whether it would be necessary to install additional treatment, such as GAC adsorption, to reduce the concentration of 4,4'-DDT in the effluent. In addition, all of the reported dissolved solids concentrations exceed the AML and MDL. EPA estimated the cost of a P2 program for 4,4'-DDT and dissolved solids along with additional treatment using GAC adsorption to comply with WQBELs derived from the economic analysis criteria. If the facility is unable to consistently comply with the MDLs and AMLs for 4,4'-DDT and dissolved solids and additional treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate the its best compliance options. For this analysis, EPA assumed that the facility would implement a P2 program and apply for a variance for 4,4'-DDT and dissolved solids and estimated the cost of this alternative compliance mechanism.
Exhibit A-33 summarizes the estimated incremental costs for the Coachella Mid-Valley WRC.
Exhibit A-33: Coachella Mid-Valley WRC Estimated Incremental Costs (9.9 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                  $3,978,548
                                      $0
                                   $131,200
                                   $398,621
                                   $506,747
Copper, Selenium, 

Chemical Precipitation
                                  $5,136,287
                                      $0
                                  $1,955,690
                                  $2,300,929
                                  $2,440,519

Medium Facility P2 Program
                                      $0
                                    $66,230
                                      $0
                                    $30,908
                                    $30,908

           Alternative Compliance Mechanism for Copper and Selenium

Medium Facility P2 Program
                                      $0
                                    $66,230
                                      $0
                                    $30,908
                                    $30,908

Variance Feasibility
Analysis
                                      $0
                                    $90,328
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $511,360
                                      $0
                                      $0
                                      $0
4,4'-DDT, Dissolved Solids
Adsorption
                                  $18,139,164
                                      $0
                                   $263,900
                                  $1,483,137
                                  $1,976,109

Medium Facility P2 Program
                                      $0
                                    $66,230
                                      $0
                                    $30,908
                                    $30,908

     Alternative Compliance Mechanism for 4,4'-DDT and Dissolved Solids

Medium Facility P2 Program
                                      $0
                                    $66,230
                                      $0
                                    $30,908
                                    $30,908

Variance Feasibility
Analysis
                                      $0
                                    $90,328
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $511,360
                                      $0
                                      $0
                                      $0
TOTAL:
                                       
                                       
                                       
                                       
                                       
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Pagosa Area Water and Sanitation District - Vista WWTP (CO0031755)
The Pagosa Area Water and Sanitation District - Vista WWTP (Pagosa Area WWTP; NPDES permit number CO0031755) is a POTW located in Pagosa Springs, Colorado. The facility treats wastewater from the Pagosa Area Water and Sanitation District 1 in addition to wastewater from the Pagosa Springs Sanitation General Improvement District. The Pagosa Area WWTP discharges into Stevens Draw, Martinez Creek, and Stollsteimer Creek. The authorized discharge point is Outfall 001A.
EPA developed this facility analysis based on the 2019 permit and associated fact sheet issued by the Colorado Department of Public Health and the Environment together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Pagosa Area WWTP has a facility design flow of 3.9 MGD (3.75 MGD January to March), with effluent limitations for E. coli, total residual chlorine, total inorganic nitrogen, ammonia, BOD, TSS, iron, copper, lead, manganese, mercury and selenium. No information about treatment processes was available.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-34. 
Exhibit A-34: Summary of Available Effluent Data for Pagosa Area WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             63
                                                                          30.0 
                                                                         120 b 
                                                                               
Ammonia
                                                                             63
                                                                          2,000
                                                                         19,800
                                                                            10 
Arsenic
                                                                             20
                                                                          1.45 
                                                                           2.1 
                                                                           0.4 
Cadmium
                                                                             20
                                                                          0.50 
                                                                          10.0 
                                                                          0.05 
Chloride
                                                                             20
                                                                        45,350 
                                                                        62,900 
                                                                             4 
Chromium (III)
                                                                             20
                                                                          10.0 
                                                                          12.0 
                                                                             - 
Chromium (VI)
                                                                             20
                                                                           8.0 
                                                                          10.4 
                                                                           0.3 
Copper
                                                                             21
                                                                           3.2 
                                                                          68.7 
                                                                           0.5 
Cyanide
                                                                             20
                                                                            10 
                                                                            10 
                                                                             5 
Iron
                                                                             20
                                                                          70.5 
                                                                           125 
                                                                             1 
Lead
                                                                             20
                                                                         0.500 
                                                                          35.6 
                                                                           0.6 
Manganese
                                                                             20
                                                                          61.3 
                                                                           129 
                                                                           0.1 
Nickel
                                                                             20
                                                                           3.2 
                                                                           5.5 
                                                                           0.5 
Nonylphenol
                                                                             20
                                                                          3.20 
                                                                          15.8 
                                                                             - 
Selenium
                                                                             20
                                                                           1.0 
                                                                           2.6 
                                                                           0.6 
Silver
                                                                             20
                                                                          0.20 
                                                                          0.30 
                                                                           0.1 
Zinc
                                                                             21
                                                                          22.2 
                                                                          72.5 
                                                                          0.05 
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
b While the daily maximum for this facility was measured as 120 cfu/100 mL, the maximum of monthly averages was 79 cfu/100 mL.
Exhibit A-35 summarizes the RPA for all parameters with sufficient data. No dilution was used, as the NPDES permit does not authorized mixing zones because effluent constitutes 100% of the flow. 
Exhibit A-35: Summary of Reasonable Potential Analysis for Pagosa Area WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                             - 
                                                                             - 
                                                                             - 
                                                                             - 
                                                                             - 
                                                                            -  
                                      N/A
                                      Yes
Ammonia
                                                                         47,040
                                                                        47,040 
                                                                              -
                                                                        11,000 
                                                                         1,400 
                                                                             - 
                                      No
                                      N/A
Arsenic
                                                                          2.91 
                                                                          2.91 
                                                                              -
                                                                           340 
                                                                           150 
                                                                            -  
                                      Yes
                                      N/A
Cadmium
                                                                          64.2 
                                                                           61.8
                                                                              -
                                                                           1.8 
                                                                          0.72 
                                                                            -  
                                      Yes
                                      N/A
Chloride
                                                                         77,420
                                                                         77,420
                                                                              -
                                                                       860,000 
                                                                       230,000 
                                                                            -  
                                      No
                                      N/A
Chromium (III)
                                                                          5.25 
                                                                           14.3
                                                                              -
                                                                           570 
                                                                            74 
                                                                            -  
                                      No
                                      N/A
Chromium (VI)
                                                                          11.3 
                                                                          11.0 
                                                                              -
                                                                            16 
                                                                            11 
                                                                            -  
                                      Yes
                                      N/A
Copper
                                                                           485 
                                                                           485 
                                                                          3.20 
                                                                           4.4 
                                                                           2.7 
                                                                         1,300 
                                      Yes
                                      No
Cyanide
                                                                          10.0 
                                                                          10.0 
                                                                          10.0 
                                                                            22 
                                                                           5.2 
                                                                           4.0 
                                      Yes
                                      Yes
Iron
                                                                               
                                                                           198 
                                                                            -  
                                                                               
                                                                         1,000 
                                                                            -  
                                      No
                                      N/A
Lead
                                                                           315 
                                                                            315
                                                                            -  
                                                                            65 
                                                                           2.5 
                                                                            -  
                                      Yes
                                      N/A
Manganese
                                                                              -
                                                                              -
                                                                          61.3 
                                                                              -
                                                                              -
                                                                            50 
                                      N/A
                                      Yes
Nickel
                                                                          7.65 
                                                                          7.65 
                                                                          3.20 
                                                                           470 
                                                                            52 
                                                                           180 
                                      No
                                      No
Nonylphenol
                                                                          52.2 
                                                                          52.2 
                                                                            -  
                                                                            28 
                                                                           6.6 
                                                                             - 
                                      Yes
                                      N/A
Selenium
                                                                               
                                                                          4.27 
                                                                          1.00 
                                                                               
                                                                           1.5 
                                                                           130 
                                      Yes
                                      No
Silver
                                                                          0.35 
                                                                              -
                                                                              -
                                                                           3.2 
                                                                              -
                                                                             - 
                                      No
                                      N/A
Zinc
                                                                           162 
                                                                            163
                                                                          22.2 
                                                                           120 
                                                                           120 
                                                                         2,600 
                                      Yes
                                      No
Notes:
[a] No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, 11 parameters have reasonable potential. Exhibit A-36 summarizes average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Pagosa Area WWTP. 
Exhibit A-36: Summary of Calculated Limits for Parameters with Reasonable Potential for Pagosa Area WWTP (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                            100
                                                                              -
                                                                           79 a
                                      No
Ammonia
                                      AL
                                                                          1,400
                                                                          5,200
                                                                         19,800
                                      Yes
Cadmium
                                      AL
                                                                            0.5
                                                                            1.4
                                                                           10.0
                                      Yes
Chromium (VI)
                                      AL
                                                                             11
                                                                             12
                                                                           10.4
                                      No
Copper
                                      AL
                                                                            1.4
                                                                            4.4
                                                                           68.7
                                      Yes
Cyanide
                                      HH
                                                                            4.0
                                                                            4.0
                                                                           10.0
                                      Yes
Lead
                                      AL
                                                                            1.4
                                                                            4.7
                                                                           35.6
                                      Yes
Manganese
                                      HH
                                                                             50
                                                                             91
                                                                          128.5
                                      Yes
Nonylphenol
                                      AL
                                                                            4.9
                                                                             12
                                                                           15.8
                                      Yes
Selenium
                                      AL
                                                                            1.5
                                                                            2.7
                                                                            2.6
                                      Yes
Zinc
                                      AL
                                                                             61
                                                                            120
                                                                           72.5
                                      Yes
Note:
[a] While the daily maximum for this facility was measured as 120 cfu/100 mL, the maximum of monthly averages was 79 cfu/100 mL.
Summary
Although the RPA indicates reasonable potential for bacteria and chromium VI, actual effluent sampling results for these parameters meet the effluent limits for these parameters derived from the economic analysis criteria, so EPA estimated no incremental compliance costs for meeting these limits.
Reported effluent concentrations of ammonia since 2016 have ranged from below the DL to 19,800 ug/L. Reported concentrations are frequently above the AML and MDL derived from the economic analysis criteria, with values exceeding the MDL more than 36% of the time. A facility upgrade may be necessary. As summarized in Exhibit A-37, EPA estimated the cost of a facility upgrade to add an additional nitrification step to the treatment process.
The RPA indicates reasonable potential for cadmium, but actual reported concentrations comply with the MDL derived from the economic analysis criteria in 18 of the 20 measurements. The exceedances were in April and November 2020. However, reported concentrations exceeded the AML in all cases. Likewise, copper concentrations reported since 2016 ranged from1.0 to 68.7 ug/L and frequently exceed the effluent limitations derived from the economic analysis criteria. Furthermore, manganese was measured from August 2019 through March 2021. The 20 measurements ranged from 12.75 to 128.5 ug/L and the average was 61.8 ug/L. Manganese control (e.g., using potassium permanganate for oxidation) will be necessary to meet the AML of 50 ug/L and the MDL of 91 ug/L.As summarized in Exhibit A-37, EPA estimated the cost of a P2 program and adding chemical precipitation and filtration/oxidation to the treatment system for metals removal. If the facility is unable to consistently comply with the MDLs and AMLs for copper, cadmium, or manganese and additional treatment is potentially infeasible (e.g., may cause substantial and widespread socioeconomic impact), the facility could apply for a WQS variance to investigate the its best compliance options. Therefore, EPA also included estimates for the cost of a P2 program and variance application for copper, cadmium, and manganese.
Cyanide was measured from August 2019 through March 2021. The 20 measurements were all 10 ug/L, which exceeds the AML and MDL of 4.0 ug/L. Removal for cyanide can be achieved with GAC adsorption or pH adjustments and chlorine. Since the facility currently uses UV for disinfection, EPA estimated the cost for addition of a chlorine contact chamber and dechlorination. These costs are summarized in Exhibit A-37.
Lead was measured from August 2019 through March 2021. The 20 measurements ranged from 0.50 to 35.6 ug/L and the average was 2.26 ug/L. All the measurements were 0.50 ug/L except for a single measurement of 35.6 ug/L. Based on this information, at this time, additional treatment for lead does not appear to be needed. However, chemical precipitation to remove other metals or GAC to control cyanide would have the additional benefit of reductions in lead.
Nonylphenol was measured from August 2019 through March 2021. The 20 measurements ranged from 0.00 to 15.80 ug/L and the average was 1.23 ug/L. Nonylphenol control may be necessary to consistently meet the average monthly limit of 4.9 ug/L and the maximum daily limit of 12 ug/L. Optimizing the existing treatment processes (including biosolids removal) can be used to remove nonylphenol. Therefore, EPA estimated no incremental compliance costs for meeting nonylphenol limits. In addition, if GAC is installed to control cyanide, an additional benefit will be reductions in nonylphenol.
Selenium was measured from August 2019 through March 2021. The 20 measurements ranged from 1.0 to 2.6 ug/L and the average was 1.23 ug/L. Selenium control may not be necessary to meet the AML of 1.5 ug/L and the MDL of 2.7 ug/L. No reported values were greater than the MDL and most results were reported below the AML. Therefore, EPA estimated no incremental compliance costs for meeting selenium limits.
Zinc was measured from January 2016 through March 2021. The 21 measurements ranged from 6.7 to 72.5 ug/L and the average was 26.2 ug/L. Zinc control may not be necessary to meet the AML of 60 ug/L and the MDL of 120 ug/L. There was a single reported concentration (72.5 ug/L) that was greater than the AML. Therefore, EPA estimated no incremental compliance costs for meeting zinc limits.
Exhibit A-37: Pagosa Area WWTP Estimated Incremental Costs (3.9 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                  $1,218,320
                                      $0
                                    $79,610
                                   $161,500
                                   $194,611
Cyanide
Chlorination (with Dechlorination)
                                  $2,504,713
                                      $0
                                   $215,100
                                   $383,456
                                   $451,527
Cadmium, Copper, Manganese
Chemical Precipitation
                                  $2,598,967
                                      $0
                                   $754,320
                                   $929,011
                                   $999,644

Small Facility P2 Program
                                      $0
                                    $49,671
                                      $0
                                    $29,802
                                    $29,802

      Alternative Compliance Mechanism for Cadmium, Copper, and Manganese

Small Facility P2 Program
                                      $0
                                    $49,671
                                      $0
                                    $29,802
                                    $29,802

Variance Feasibility
Analysis
                                      $0
                                   $135,492
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $383,520
                                      $0
                                      $0
                                      $0
TOTAL:
                            $3,723,033 - $6,322,000
                                  $49,671 - 
                                   $568,683
                             $294,710 - $1,049,030
                                  $574,758 - 
                                  $1,503,769
                                  $675,940 - 
                                  $1,675,584
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
CF Industries Nitrogen (IA0004014)
The CF Industries Nitrogen, LLC  -  Port Neal Nitrogen Complex (CF Industries Nitrogen; NPDES permit number IA0021784)  contains an ammonia plant, two nitric acid plants, two liquid urea plants, and a urea ammonium nitrate plant, all located in Woodbury County, Iowa, in Township 87N. CF Industries Nitrogen, LLC operates the facility. The industrial complex discharges treated industrial wastewater into the Missouri River, which is impaired for arsenic and habitat alteration. Outfall 001 combines waste streams from the plant.
EPA developed this facility analysis based on the 2015 permit as amended in 2018, which was issued by the Iowa Department of Natural Resources, together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
CF Industries Nitrogen has a design flow of 2.23 MGD. The permit stipulates effluent limitations for ammonia, nitrate nitrogen, organic nitrogen, and total residual chlorine. Treatment processes include septic tanks and leach fields that do not discharge to surface waters. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-38. 
Exhibit A-38: Summary of Available Effluent Data for CF Industries Nitrogen (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Ammonia
                                                                             64
                                                                         35,020
                                                                        131,670
                                                                             10
Chlorine
                                                                             64
                                                                             80
                                                                            350
                                                                             10
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-39 summarizes the RPA for all parameters with sufficient data. Critical low flow data used in this analysis were provided in the permit and were used to calculate dilution factors for use in the analysis. Where ambient data were not available, half the DL was used unless that value was above the applicable criteria. 
Exhibit A-39: Summary of Reasonable Potential Analysis for CF Industries Nitrogen (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Ammonia
                                                                         3,520 
                                                                         3,520 
                                                                              -
                                                                        11,000 
                                                                         1,400 
                                                                              -
                                      Yes
                                      N/A
Chlorine
                                                                          10.9 
                                                                          10.9 
                                                                              -
                                                                            19 
                                                                            11 
                                                                              -
                                      No
                                      N/A
Note:
[a] Calculated based on dilution factors for aquatic life acute (59), aquatic life chronic (59), human health non-carcinogens (82), and human health carcinogens (175) following the methods used in the fact sheet and based on flow conditions.
As shown above, the facility has reasonable potential for ammonia. Exhibit A-40 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for CF Industries. 
Exhibit A-40: Summary of Calculated Limits for Parameters with Reasonable Potential for CF Industries Nitrogen (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                    77,000
                                    200,000
                                  130,000[a]
                                      Yes

Summary
Since January 2016, the maximum daily effluent concentration of ammonia has not exceeded the proposed MDL and the average monthly concentration has not exceeded the proposed AML. The facility should be capable of meeting the proposed limits with its existing treatment processes, with optimization as needed. Consequently, EPA estimated no incremental compliance costs for meeting these limits.
MidAmerican Energy - Neal North Energy Center (IA0004103)
The MidAmerican Energy Company  -  Neal North Center (Neal North; NPDES permit number IA0004103) generates electricity for sale and distribution using coal with a thermal cycle that employs the steam water system as the thermodynamic medium. Neal North is located in Sergeant Bluff, Iowa, and discharges via three outfalls to the Missouri River: 003, 009, and 016. This industrial facility is located approximately 5 miles away from the Winnebago Tribe, also known as the Ho-Chunk Tribe. 
EPA developed this facility analysis based on the 2017 permit issued by the Iowa Department of Natural Resources together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Neal North has a facility design flow of 6.03 MGD. The permit includes effluent limitations for TSS, total iron, total copper, pH, selenium, aluminum, and chromium (VI) for Outfall 003. All three outfalls discharge into the Missouri River along a stretch of shoreline that is less than 2,000 feet long. 
Reasonable Potential Analysis
The available monitoring data for the facility do not include observations for any parameter of interest between 2016 and 2020, including some months where the facility reported no discharge. 
Summary
EPA assumes that there will be no incremental costs for this facility.
MidAmerican Energy - Neal South Energy Center (IA0061859)
The MidAmerican Energy Company  -  Neal South Center (hereinafter "Neal South;" NPDES permit number IA0061859 generates electricity for sale and distribution, using coal with a thermal cycle employing the steam water system as the thermodynamic medium. Neal South is in Salix, Iowa, and discharges to the Missouri River. The Missouri River is a Class A1 water, reflecting primary contact recreational uses. This industrial facility is located approximately 3 miles away from the Winnebago Tribe, also known as the Ho-Chunk Tribe. 
EPA developed this facility analysis based on the 2017 permit (as amended in 2018) and associated rationale issued by the Iowa Department of Natural Resources, together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Water is withdrawn from the Missouri River and used for once-through condenser cooling before returning to the River. This surface water is also used in some of the low-volume waste generating activities taking place at the facility. Well water is used in low-volume processes (reverse osmosis) and fire protection and for air preheater washing (non-chemical metal cleaning). Treated wastewater and river water are used in the bearing flush and seal water system. All waste streams from this facility are discharged to the Missouri River through several outfalls:
Outfall 001 discharges once-through condenser cooling water; it has an average monthly flow rate of 468 MGD and a maximum daily flow rate of 484 MGD. It has existing limits for temperature only, and the fact sheet notes that no other parameters are evaluated for this outfall since it is used for non-contact cooling water only and all concentrations are attributable to intake water from the Missouri River.
Outfall 004 discharges WTP filter backwash and rinse water, boiler blowdown, reverse osmosis reject, neutralized demineralizer waste, floor drains, oil water separator waste, coal combustion residual monofill leachate, and monofill stormwater runoff. It has an average monthly flow rate of 0.0833 MGD and a daily maximum flow rate of 0.161 MGD. It has limits for TSS, oil & grease, and acute toxicity.
Outfall 005 discharges underboiler quench water bath blowdown and has an estimated flow of 0.144 MGD.
Outfall 006 combines discharges from Outfalls 004, 005, and 008, stormwater runoff, and intermittent discharge from various water holding tanks and the fire protection system.
Outfall 007 discharges from the main condenser and has an identical location to Outfall 001; it has an average monthly flow of 302.4 MGD and a maximum daily flow of 320 MGD.
Outfall 008 infrequently discharges non-chemical metal cleaning wastes from the air heater wash pond at most once every two years.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for chlorine for the three outfalls shown in Exhibit A-41. The facility has limitations and monitoring requirements for additional outfalls and parameters, but no data were available for RPAs; all data for Outfall 005 indicate that it is not operational.
Exhibit A-41: Summary of Available Chlorine Effluent Data for Neal South (ug/L)
Outfall
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

001
                                                                             10
                                                                             45
                                                                             90
                                                                             10
006
                                                                             20
                                                                             20
                                                                             60
                                                                             10
007
                                                                             15
                                                                             30
                                                                            130
                                                                             10
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-42 summarizes the chlorine RPA. Critical low flow data were provided in the permit and were used to calculate dilution factors for use in the analysis. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criteria, which is conservative assumption for chlorine.
Exhibit A-42: Summary of Chlorine Reasonable Potential Analysis for Neal South by Outfall (ug/L)
Outfall
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
001[a]
                                                                            180
                                                                           61.5
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
006[b]
                                                                          0.110
                                                                         0.0100
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      No
                                      N/A
007[c]
                                                                            257
                                                                           70.1
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Notes:
[a] Calculated based on dilution factors for aquatic life acute (1.27), aquatic life chronic (3.73), human health non-carcinogens (4.82), and human health carcinogens (9.40) following the methods used in the fact sheet based on flow conditions. 
[b] Calculated based on dilution factors for aquatic life acute (1533), aquatic life chronic (15319), human health non-carcinogens (21447), and human health carcinogens (47190) following the methods used in the fact sheet based on flow conditions.
[c] Calculated based on dilution factors for aquatic life acute (1.42), aquatic life chronic (5.22), human health non-carcinogens (6.91), and human health carcinogens (14.00) following the methods used in the fact sheet based on flow conditions.
As shown above, two outfalls have reasonable potential for chlorine. Exhibit A-43 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA. 
Exhibit A-43: Summary of Calculated Chlorine Limits for Neal South Energy Center by Outfall (ug/L)
Outfall
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

001
                                      AL
                                                                             13
                                                                             24
                                                                           90.0
                                      Yes
007
                                      AL
                                                                             13
                                                                             27
                                                                            130
                                      Yes

Summary
Although available effluent data indicate reasonable potential for chlorine at Outfall 001 and 007, there are no reported measurements of chlorine since the August 2017 discharge monitoring report. Furthermore, the current permit fact sheet notes that the facility does not chlorinate once-through cooling water and the current permit prohibits the discharge of chlorine from Outfalls 001 and 007. In addition, Outfall 006, where there was no reasonable potential for chlorine, is a stormwater discharge, and the facility is required to perform stormwater management and monitoring activities.
Based on the available data and the requirements of the current permit, EPA estimated no incremental compliance costs for this facility to comply with chlorine limits derived from the economic analysis criteria.
City of Pocatello WPCF (ID0021784)
The City of Pocatello WPCF (Pocatello WPCF; NPDES permit number ID0021784)  is a POTW located in, and owned and operated by, the City of Pocatello, Idaho. The facility serves the cities of Pocatello and Chubbuck, with a combined resident population of approximately 68,000. The facility is located within one mile upstream from Fort Hall Tribal land. The secondary treatment plant discharges treated municipal wastewater to the Portneuf River. The collection system has no combined sewers. 
EPA developed this facility analysis based on the 2012 permit and supporting fact sheet issued by EPA. EPA subsequently transferred authority for issuing the permit to the state of Idaho in 2018; however, an updated state-issued permit is not available online. For this analysis, EPA assumed that the 2012 permit and its associated fact sheet are representative of this facility. EPA also used available discharge monitoring reports from between 2016 and 2021 to conduct the RPA.
Effluent and Treatment Process
The Pocatello WPCF has a facility design flow of 12 MGD. The permit contains effluent limitations for BOD, TSS, E.coli, pH, total residual chlorine, ammonia, and total phosphorous.
Pocatello's WPCF process includes screen and grit removal, primary clarification, activated sludge and nitrogen reduction, final clarification, disinfection using chlorine gas and dechlorination using sulfur dioxide gas. The treated wastewater is then discharged to the Portneuf River. Solids are further processed using anaerobic digestion and a sludge lagoon for thickening the solids before they are distributed for beneficial use as a fertilizer on local agriculture fields owned by the City of Pocatello. In addition, the digestion process produces biogas which fuels cogeneration engines that produce electricity used within the Pocatello WPCF. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-44. 
Exhibit A-44: Summary of Available Effluent Data for Pocatello WPCF (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             64
                                                                            3.0
                                                                       2,419[b]
                                                                            - 
Ammonia
                                                                             64
                                                                          1,440
                                                                         26,200
                                                                             10
Arsenic
                                                                             11
                                                                            1.5
                                                                            2.3
                                                                            0.4
Cadmium
                                                                             11
                                                                           0.05
                                                                           0.10
                                                                           0.05
Copper
                                                                             11
                                                                            6.0
                                                                             10
                                                                            0.5
Cyanide
                                                                             11
                                                                            2.5
                                                                            2.5
                                                                              5
Lead
                                                                             11
                                                                           0.25
                                                                           0.60
                                                                            0.6
Nickel
                                                                             11
                                                                            2.2
                                                                            3.0
                                                                            0.5
Selenium
                                                                             11
                                                                           0.50
                                                                            2.0
                                                                            0.6
Zinc
                                                                             11
                                                                             48
                                                                             68
                                                                           0.05
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the instantaneous maximum for this facility was measured as 2,419 cfu/100 mL, the maximum of monthly averages was 4 cfu/100 mL.
Exhibit A-45 summarizes the RPA for all parameters with sufficient data. Critical low flow data used in this analysis were provided in the permit and were used to calculate dilution factors for use in the analysis. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criteria. 
Exhibit A-45: Summary of Reasonable Potential Analysis for Pocatello WPCF (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)b
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Ammonia
                                                                         33,200
                                                                         29,200
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Arsenic
                                                                            3.9
                                                                         4.0[c]
                                                                              -
                                                                            340
                                                                            150
                                                                              -
                                      No
                                      N/A
Cadmium
                                                                           0.13
                                                                           0.11
                                                                              -
                                                                            1.8
                                                                           0.72
                                                                              -
                                      No
                                      N/A
Copper
                                                                            9.8
                                                                            8.7
                                                                            1.5
                                                                            4.4
                                                                            2.7
                                                                           1300
                                      Yes
                                      No
Cyanide
                                                                            4.0
                                                                            3.5
                                                                           0.93
                                                                            22.
                                                                            5.2
                                                                              4
                                      No
                                      No
Lead
                                                                           0.87
                                                                           0.76
                                                                              -
                                                                             65
                                                                            2.5
                                                                              -
                                      No
                                      N/A
Nickel
                                                                            2.5
                                                                            2.2
                                                                           0.98
                                                                            470
                                                                             52
                                                                            180
                                      No
                                      No
Selenium
                                                                            3.4
                                                                            3.0
                                                                           0.19
                                                                              -
                                                                            1.5
                                                                            130
                                      Yes
                                      No
Zinc
                                                                             67
                                                                             61
                                                                             18
                                                                            120
                                                                            120
                                                                           2600
                                      No
                                      No
Notes:
[a] Calculated based on dilution factors for aquatic life acute (1.9), aquatic life chronic (2.2), human health non-carcinogens (2.7), and human health carcinogens (4.5) following the methods used in the fact sheet based on flow conditions. 
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
[c] The concentration at the edge of the chronic mixing zone is greater than the concentration at the edge of the acute mixing zone because the ambient concentration is greater than the effluent concentration.
As shown above, bacteria, ammonia, copper, and selenium have reasonable potential. Exhibit A-46 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Pocatello WPCF. 
Exhibit A-46: Summary of Calculated Limits for Parameters with Reasonable Potential for Pocatello WPCF (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria
                                      HH
                                                                            100
                                                                               
                                                                              4
                                      No
Ammonia
                                      AL
                                                                          2,600
                                                                         12,000
                                                                         26,200
                                      Yes
Copper
                                      AL
                                                                            5.0
                                                                            7.9
                                                                             10
                                      Yes
Selenium
                                      AL
                                                                            3.0
                                                                            8.7
                                                                            2.0
                                      No

Summary
Although the RPA indicates reasonable potential for bacteria and selenium actual effluent sampling results for these parameters meet the effluent limits derived from the proposed WQSi for these parameters, so EPA estimated no incremental compliance costs for meeting these limits. 
The facility's current average monthly ammonia limits are 6.3 mg/L during Nov-June and 5.0 mg/L during July-Oct. The maximum daily limits are 16.4 mg/L during Nov-June and 13.0 mg/L during July-Oct. The limits derived from the economic analysis criteria are an AML of 2.6 mg/L MDL of 12 mg/L. DMR data suggest that the facility meets the current MDL about 84% of the time and the exceedances do not occur at predictable intervals. The facility currently meets the proposed MDL of 2.6 mg/L about 69% of the time. A treatment system upgrade may be necessary. As summarized in Exhibit A-47, EPA estimated the cost of a facility upgrade to add an additional nitrification step to the treatment process.
Copper data from April 2016 through April 2021 include 11 measurements ranging from 3.0 to 10 ug/L and averaging 6.2 ug/L. Most of the samples are less than the proposed MDL but greater than the proposed AML. To meet the AML, additional treatment may be necessary. As summarized in Exhibit A-47, EPA estimated the range of incremental cost to this facility of adding chemical precipitation along with implementing a P2 program to reduce effluent concentrations of copper. EPA assumed that the facility could adapt its existing primary clarifier for this process.
Exhibit A-47: Pocatello WPCF Estimated Incremental Costs (12 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                  $5,460,000
                                      $0
                                   $145,700
                                   $512,698
                                   $661,085
Copper
Chemical Precipitation
                                   $826,000
                                      $0
                                   $134,270
                                   $189,790
                                   $212,239

Medium Facility P2 Program
                                      $0
                                    $33,115
                                      $0
                                    $15,454
                                    $15,454
TOTAL:
                                  $6,286,000
                                    $33,115
                                   $279,970
                                   $717,942
                                   $888,778
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
City of Devils Lake WWTF (ND0020681)
The City of Devils Lake WWTF (Devils Lake WWTF; NPDES permit number ND0020681) is a POTW located in the City of Devils Lake, North Dakota. The facility services the City of Devils Lake, which had a population of 7,141 in 2020. Facility discharges are directed into Creel Bay at Devils Lake.
EPA could not locate permit documentation for this facility and based the analysis on discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Devils Lake WWTF is authorized to discharge domestic wastewater. The facility combines a Lemna system (which relies on the growth of duckweed to treat BOD, TSS, and inorganic contaminants) and facultative lagoon systems. The treatment system has a design flow of 5.50 MGD and consists of three waste stabilization ponds, the Lemna system, and an artificial wetland. Wastewater can be transferred from Cell 3 to the North Marsh (the artificial wetland) through Outfall 003. From the North Marsh, wastewater passes through the Lemna system. The North Marsh is located adjacent to the Devils Lake Municipal Airport's runway. Due to concerns about the number of birds present, the Devils Lake WWTF plans to use the North Marsh on an as needed basis for treatment or to address hydraulic issues and not as a routine part of treatment. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for ammonia and nitrates as shown in Exhibit A-48. 
Exhibit A-48: Summary of Available Effluent Data for City of Devils Lake WWTF (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Ammonia
                                                                             18
                                                                          2090 
                                                                         5,780 
                                                                           100
Nitrates
                                                                              8
                                                                              -
                                                                           240 
                                                                              2
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-49 summarizes the RPA for all parameters with sufficient data. Information about mixing zones authorized in the permit was not available; as such, EPA assumed a dilution factor of 10 for all parameters. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criteria.
Exhibit A-49: Summary of Reasonable Potential Analysis for City of Devils Lake WWTF (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Ammonia
                                                                         1,796 
                                                                         1,796 
                                                                               
                                                                        11,000 
                                                                         1,400 
                                                                             - 
                                      Yes
                                      N/A
Nitrates
                                                                               
                                                                               
                                                                          19.2 
                                                                               
                                                                               
                                                                        10,000 
                                      N/A
                                      No

As shown above, ammonia has reasonable potential. Exhibit A-50 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Devils Lake WWTF. 
Exhibit A-50: Summary of Calculated Limits for Parameters with Reasonable Potential for City of Devils Lake WWTF (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                                                          7,600
                                                                         25,000
                                                                          5,780
                                      No

Summary
Although the RPA indicates reasonable potential for ammonia, actual effluent sampling results meet the effluent limits derived from the economic analysis criteria. The facility may wish to optimize its system to ensure it continues to operate in a way that achieves compliance with the potential limits and should be able to do so at minimal cost. Therefore, EPA estimated no incremental compliance cost for this facility at this time.
MG Waldbaum Company (NE0113735)
The MG Waldbaum Company facility (MG Waldbaum; NPDES permit number NE0113735) is in Wakefield, Nebraska, and conducts dairy product production, poultry slaughtering and processing, and chicken egg production. The facility is owned by the Michael Foods Egg Products Company and discharges industrial wastewater into Logan Creek. 
EPA could not locate permit documentation for this facility and based the analysis on discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Outfall 001 is the effluent discharge from the iron filter and softener backwash water treatment system. The discharge is to Logan Creek. Outfall 003 discharges effluent from the extended aeration activated sludge system to Logan Creek through a diffuser. Effluent from the industrial lagoon treatment system may also be land applied. MG Waldbaum's permit includes effluent limits for TSS, BOD, ammonia nitrogen, hydrogen sulfide, and residual chlorine. Reported design flow for the facility in EPA's Enforcement and Compliance History Online (ECHO) is 0.70 MGD.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for Outfall 003 for the parameters shown in Exhibit A-51.
Exhibit A-51: Summary of Available Effluent Data for MG Waldbaum (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                              5
                                                                              -
                                                                            72 
                                                                               
Ammonia
                                                                             63
                                                                           400 
                                                                         7,600 
                                                                            10 
Cadmium
                                                                              4
                                                                         ND[b] 
                                                                            ND 
                                                                          0.05 
Chlorine
                                                                             25
                                                                            10 
                                                                            20 
                                                                            10 
Copper
                                                                              4
                                                                              -
                                                                            30 
                                                                           0.5 
Selenium
                                                                              4
                                                                          ND[b]
                                                                             ND
                                                                           0.6 
Zinc
                                                                              4
                                                                              -
                                                                            20 
                                                                          0.05 
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] Cadmium and selenium were not detected in the effluent.
Exhibit A-52 summarizes the RPA for all parameters with sufficient data. Information about allowed mixing in the permit was not available; as such, EPA assumed no dilution was available for any of the parameters analyzed.
Exhibit A-52: Summary of Reasonable Potential Analysis for the MG Waldbaum (ug/L)
Parameter
Conc at Edge of Mixing Zone[a] 
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)[b]
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      No
Ammonia
                                                                         19,200
                                                                         19,200
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Cadmium
                                                                            0.0
                                                                            0.0
                                                                              -
                                                                            1.8
                                                                           0.72
                                                                              -
                                      No
                                      N/A
Chlorine
                                                                             55
                                                                             55
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Copper
                                                                            140
                                                                            140
                                                                             31
                                                                            4.4
                                                                            2.7
                                                                          1,300
                                      Yes
                                      No
Selenium
                                                                              0
                                                                              0
                                                                              0
                                                                              -
                                                                            1.5
                                                                            130
                                      No
                                      No
Zinc
                                                                             95
                                                                             95
                                                                             21
                                                                            120
                                                                            120
                                                                          2,600
                                      No
                                      No
Notes:
[a] No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, ammonia, chlorine, and copper have reasonable potential. Exhibit A-53 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the MG Waldbaum facility. 
Exhibit A-53: Summary of Calculated Limits for Parameters with Reasonable Potential for MG Waldbaum (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                                                          1,400
                                                                          5,400
                                                                          7,600
                                      Yes
Chlorine
                                      AL
                                                                            8.1
                                                                             19
                                                                             20
                                      Yes
Copper
                                      AL
                                                                            2.2
                                                                            4.4
                                                                             30
                                      Yes

Summary
DMR data reported from January 2016 to April 2021 indicate that the facility has met the proposed MDL (5.4 mg/L) and AML (1.4 mg/L) for ammonia in all but one month. The facility may wish to optimize its system to ensure it continues to operate in a way that achieves compliance with the potential limits and should be able to do so at minimal cost. Therefore, EPA estimated no incremental compliance cost to comply with effluent limits for ammonia derived from the economic analysis criteria.
The facility had 25 detected measurements of chlorine from January 2016 to April 2021. The average of these detected measurements was 8.4 ug/L and the data ranged from 0 to 20 ug/L. To meet the limits derived from the potential baseline WQS of 8.1 ug/L as an AML and 19 ug/L as an MDL, the facility will need to add dechlorination. EPA estimated the cost of an upgrade to add dechlorination to the treatment process.
Copper was measured four times between July 2016 and April 2021. The 4 measurements ranged from 10 to 30 ug/L and averaged 17.50 ug/L, which exceeds both the AML of 2.2 ug/L and the MDL of 4.4 ug/L. To comply with the proposed AML and MDL for copper, the facility could evaluate a P2 program paired with additional treatment using a process such as chemical precipitation or ion exchange. EPA estimated the incremental cost of these options for this facility.
Exhibit A-54 summarizes the estimated costs for the treatment options considered for additional removal of ammonia, chlorine, and copper.
Exhibit A-54: MG Waldbaum Estimated Incremental Costs (0.70 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Chlorine
Dechlorination
                                   $440,167
                                      $0
                                    $35,276
                                    $64,862
                                    $76,825
Copper
Chemical Precipitation
                                  $1,063,069
                                      $0
                                   $375,486
                                   $446,941
                                   $475,832

Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

                       Alternative Treatment for Copper

Ion Exchange
                                  $1,442,194
                                      $0
                                   $140,413
                                   $237,351
                                   $276,546

Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934
TOTAL:
                            $1,503,236 - $1,882,361
                                    $16,557
                              $175,689 -$410,762
                             $312,147 - $521,737 -
                             $363,305 -$562,591 -
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Los Alamos County Department of Public Utilities WWTF (NM0020141)
Los Alamos County Department of Public Utilities WWTF (Los Alamos WWTF; NPDES permit number NM0020141) is located in Los Alamos, New Mexico. The facility discharges from one outfall (Outfall 001) into the receiving water Pueblo Canyon, which flows into Los Alamos Canyon, a tributary to the Rio Grande. 
EPA developed this facility analysis based on the EPA-issued 2017 permit together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Los Alamos WWTF has a facility design flow of 1.40 MGD. The permit includes effluent limitations for BOD, TSS, E. coli, total residual chlorine, thallium, aluminum, and pH. EPA does not have information about the treatment processes currently in use at the facility.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-55. 
Exhibit A-55: Summary of Available Effluent Data for Los Alamos WWTF (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             50
                                                                           15.6
                                                                         121[b]
                                                                              -
Aluminum
                                                                             15
                                                                             10
                                                                             60
                                                                              -
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 121.06 cfu/100 mL, the maximum of monthly averages was 31 cfu/100 mL.
Exhibit A-56 summarizes the RPA for all parameters with sufficient data. EPA did not have information on whether mixing is authorized for this facility; as such, EPA did not use dilution for this analysis. 
Exhibit A-56: Summary of Reasonable Potential Analysis for Los Alamos WWTF (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)[b]
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      Yes
Aluminum
                                                                            196
                                                                            196
                                                                              -
                                                                            750
                                                                             87
                                                                              -
                                      Yes
                                      N/A
Notes:
[a] No dilution was used for this analysis.
[b] For bacteria, the facility was assumed to have reasonable potential if the maximum effluent concentration (see above exhibit) exceeds 100 cfu/100 mL.
As shown above, both bacteria and aluminum have reasonable potential. Exhibit A-57 summarizes the effluent limitations that were calculated as part of the RPA for the Los Alamos WWTF. 
Exhibit A-57: Summary of Calculated Limits for Parameters with Reasonable Potential for Los Alamos WWTF (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Bacteria (E. coli; cfu/100 mL)
                                      HH
                                                                           100.
                                                                               
                                                                          31[a]
                                      No
Aluminum
                                      AL
                                                                             67
                                                                            150
                                                                           60.0
                                      No
Note:
[a] While the daily maximum for this facility was measured as 121.06 cfu/100 mL, the maximum of monthly averages was 31 cfu/100 mL.
Summary
Although the RPA indicates reasonable potential for bacteria and aluminum, actual effluent sampling results for these parameters meet effluent limits derived from the economic analysis criteria. The facility may wish to optimize its system to ensure it continues to operate within the potential limits and should be able to do so at minimal cost. Therefore, EPA estimated no compliance cost for this facility at this time. 
Los Alamos National Laboratory (NM0028355)
The Los Alamos National Laboratory (Los Alamos Lab; NPDES permit number NM0028355) is located in Los Alamos, New Mexico. The facility has a combined design flow of 1.40 MGD (see discussion of outfalls below) with discharge to a receiving water named Pueblo Canyon, which flows into Los Alamos Canyon, which is tributary to the Rio Grande. The Los Alamos Lab's permit is issued to both the Department of Energy and a private LLC that manages the laboratory on behalf of the federal government. 
EPA developed this facility analysis based on the EPA-issued 2019 permit and associated fact sheet together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
This facility is permitted to discharge industrial wastewater from multiple outfalls. Cooling water blowdown, roof runoff, and stormwater are also discharged through several outfalls.
Outfall 001 discharges cooling water from the power plant, treated and recycled sanitary wastewater, and treated cooling tower blowdown to a perennial reach of Sandia Canyon. It has a continuous discharge with a monthly average flow of 0.154 MGD and a daily maximum flow of 0.333 MGD. This Outfall has a whole effluent toxicity (WET) limit (Ceriodaphnia dubia) and effluent limits for copper, zinc, thallium, and PCBs.
Outfall 13S discharges treated sanitary wastewater to Canada del Buey, an ephemeral reach. The average treated flow rate is 0.229 MGD and the maximum daily flow is 0.418 MGD. This Outfall has effluent limitations for thallium and PCBs.
Outfalls 03A027, 03A048, 03A181, 03A199, and 03A022 discharge treated cooling water and blowdown from cooling towers to various ephemeral and perennial stream reaches. When discharges occur, they have average flow rates of up to 0.088 MGD and maximum daily flows of up to 0.169 MGD. These outfalls have limits for copper, zinc, thallium, chromium, aluminum, arsenic, and mercury.
Outfall 05A055 discharges treated wastewater from the High Explosives Wastewater Treatment Facility to an ephemeral tributary of Canon de Valle. Average flow is 0.0003 MGD and the daily maximum flow is 0.0021 MGD. Effluent is usually diverted to evaporators and there was no discharge from this outfall between October 2014 and September 2018. This Outfall entails effluent limitations for aluminum, copper, selenium, zinc, and lead.
Outfall 051 discharges treated radioactive liquid waste from the Radioactive Liquid Waste Treatment Facility. It has an average flow rate of 0.02 MGD and a maximum daily flow rate of 0.040, and it discharges approximately 4 days per week. There was one discharge between October 2014 and the time of permit issuance in February 2020. This Outfall has effluent limits for copper and thallium.
Reasonable Potential Analysis
EPA had sufficient data to conduct a reasonable potential analysis for the parameters shown in Exhibit A-58 for Outfall 001. 
Exhibit A-58: Summary of Available Effluent Data for Los Alamos Lab, Outfall 001 (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Bacteria (E. coli; cfu/100 mL)
                                                                             62
                                                                           2.0 
                                                                       33.1[b] 
                                                                              -
Aluminum
                                                                              5
                                                                             - 
                                                                            20 
                                                                              -
Copper
                                                                              5
                                                                             - 
                                                                            10 
                                                                            0.5
PCBs
                                                                              5
                                                                             - 
                                                                         0.010 
                                                                           0.03
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] While the daily maximum for this facility was measured as 33.10 cfu/100 mL, the maximum of monthly averages was 15.54 cfu/100 mL.
Exhibit A-59 summarizes the RPA for Outfall 001 for all parameters with sufficient data. EPA did not have any information providing dilution factors for this facility and, therefore, assumed that no dilution was available when conducting this analysis. 
Exhibit A-59: Summary of Reasonable Potential Analysis for Los Alamos Lab, Outfall 001 (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Bacteria (E. coli; cfu/100 mL)
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                                                              -
                                      N/A
                                      No
Aluminum
                                                                          83.8 
                                                                          83.8 
                                                                              -
                                                                           750 
                                                                            87 
                                                                              -
                                      No
                                      N/A
Copper
                                                                           26.1
                                                                           26.1
                                                                           5.81
                                                                           4.4 
                                                                           2.7 
                                                                      1,300.00 
                                      Yes
                                      No
PCBs
                                                                              -
                                                                              -
                                                                          0.093
                                                                              -
                                                                              -
                                                                      0.000009 
                                      N/A
                                      Yes
Note:
[a] Calculated assuming no dilution.
As shown above, copper and PCBs discharged from Los Alamos Lab Outfall 001 have reasonable potential. Exhibit A-60 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA. 
Exhibit A-60: Summary of Calculated Limits for Parameters with Reasonable Potential for Los Alamos National Laboratory, Outfall 001 (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Copper
                                      AL
                                                                            2.2
                                                                            4.4
                                                                            6.2
                                      Yes
PCBs
                                      HH
                                                                      0.0000090
                                                                       0.000018
                                                                          0.013
                                      Yes

Summary
Although the RPA indicates reasonable potential for copper, only one annual effluent sampling result for this parameter exceeded the proposed MDL. The current permit has copper limits at Outfall 001 of 8.7 ug/L as both an AML and MDL, which are less stringent than the limits derived from the economic analysis criteria. The facility may wish to optimize its system to ensure it is able to operate within the potential limits and should be able to do so at minimal cost. Therefore, EPA estimated no compliance cost for this facility.
DMR data indicated a single reported measurement of PCBs during annual monitoring at 0.01ug/L. Otherwise PCBs were reported as not detected. The one reported value exceeds the proposed effluent limits. The current permit requires reporting only for PCBs. EPA assumes that this requirement would be retained given that the facility is not a new source of PCBs and all reported values other than one were non-detects. Therefore, EPA estimated no compliance cost for this facility.
Phillips 66 Ponca City Refinery (OK0000256)
The Phillips 66 Co. Ponca City Refinery (Phillips 66; NPDES permit number OK0000256) processes light, medium, and heavy crude oil types, producing liquefied petroleum gas (LPG), anode-grade petroleum coke, aviation fuel, diesel fuel, and gasoline. The facility covers 2,500 acres in Ponca City, Oklahoma, and is owned and operated by the Phillips 66 Corporation.
EPA could not locate permit documentation for this facility and based the analysis on discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
EPA was unable to determine the existing facility treatment processes. EPA's ECHO reports an average facility flow of 5.32 MGD. The facility has effluent limits for ammonia nitrogen, sulfide, selenium, phenols, chromium, hexavalent chromium, TSS, TDS, BOD, pH, and COD.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-61. 
Exhibit A-61: Summary of Available Effluent Data for the Phillips 66 Ponca City Refinery (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Ammonia
                                                                             52
                                                                          1,150
                                                                         16,000
                                                                             10
Chromium (VI)
                                                                             64
                                                                          ND[b]
                                                                             20
                                                                            0.3
Selenium
                                                                             64
                                                                           40.5
                                                                             85
                                                                            0.6
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] The data included both detected and non-detected concentrations. The 50th percentile (median) value was reported as "not detected."
Exhibit A-62 summarizes the RPA for all parameters with sufficient data. EPA did not have information on whether mixing is authorized for this facility; as such, EPA did not assume any dilution for this analysis. 
Exhibit A-62: Summary of Reasonable Potential Analysis for Phillips 66 (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Ammonia
                                                                         44,100
                                                                         44,100
                                                                               
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Chromium (VI)
                                                                           73.3
                                                                           71.8
                                                                              -
                                                                             16
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Selenium
                                                                              -
                                                                            107
                                                                           40.5
                                                                              -
                                                                            1.5
                                                                            130
                                      Yes
                                      No
Note:
[a] No dilution was used in this analysis.
As shown above, ammonia nitrogen, chromium (VI), and selenium have reasonable potential. Exhibit A-63 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for Phillips 66. 
Exhibit A-63: Summary of Calculated Limits for Parameters with Reasonable Potential for Phillips 66 (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                                                         1,400 
                                                                         5,300 
                                                                        16,000 
                                      Yes
Chromium (VI)
                                      AL
                                                                           5.0 
                                                                            16 
                                                                            20 
                                      Yes
Selenium
                                      AL
                                                                           1.5 
                                                                           2.4 
                                                                            85 
                                      Yes

Summary
For ammonia, the limits derived from the economic analysis criteria are an AML of 1.4 mg/L and an MDL of 5.3 mg/L. DMR data suggest that the facility would have exceeded the proposed MDL three times during the monitoring period from January 2017 to April 2021 that included 52 measurements and that the facility would have had difficulty meeting the AML on multiple occasions, particularly over the past three years. A facility upgrade may be necessary, and EPA estimated the cost of adding an additional nitrification step to the treatment process. 
Selenium was measured from January 2016 through April 2021. The 64 measurements ranged from 25 to 85 ug/L and the average was 43 ug/L. Selenium control is necessary to meet the AML of 1.5 ug/L and the MDL 2.4 ug/L derived from the potential baseline WQS. EPA estimated the costs of implementing a P2 program along with the costs to add a carbon adsorption unit to the existing treatment system.
Chromium VI was measured from August 2020 through April 2021. The 5 measurements ranged from 10 to 20 ug/L and the average was 18 ug/L. Chromium VI control is necessary to meet the AML of 5.0 ug/L and the MDL of 16 ug/L. GAC shows some effectiveness at removing chromium from wastewater streams, so the addition of the carbon adsorption for selenium removal should also result in reductions of chromium VI. Therefore, EPA did not estimate any additional incremental cost for treating chromium VI beyond the cost of a P2 program focused on chromium.
Exhibit A-64 summarizes the estimated costs to this facility of additional treatment to comply with effluent limits derived from the economic analysis criteria.
Exhibit A-64: Phillips 66 Ponca City Refinery Estimated Incremental Costs (5.32 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                  $1,669,611
                                      $0
                                    $99,340
                                   $211,564
                                   $256,939
Chromium, Selenium
Adsorption
                                  $9,851,389
                                      $0
                                   $269,710
                                   $931,878
                                  $1,199,611

Medium Facility P2 Program
                                      $0
                                    $66,230
                                      $0
                                    $30,908
                                    $30,908
TOTAL:
                                 $11,521,000 
                                   $66,230 
                                   $369,050 
                                  $1,174,350 
                                  $1,487,458 
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Kenyon Industries, Inc. (RI0000191)
Kenyon Industries, Incorporated (Kenyon Industries; NPDES permit number RI0000191) is a textile mill located in Kenyon, Rhode Island. Production activities at the facility include coating woven fabrics, finishing, printing, dyeing, and scouring. The mill discharges treated domestic and industrial effluent into the Pawcatuck River through an effluent diffuser. 
EPA developed this facility analysis based on the 2010 permit and associated fact sheet issued by the Rhode Island Department of Environmental Management together with discharge monitoring reports from between 2016 and 2021. The 2010 permit had an expiration date of 2015; however, EPA was not able to locate an updated permit and assumed that the 2010 documents are still representative of the facility.
Effluent and Treatment Process
Kenyon Industries has a package sanitary wastewater treatment system to treat domestic and two aerated lagoons to treat industrial wastewater. The outlet from the second aeration lagoon (Outfall 001A) has a maximum flow rate of 0.55 MGD. The facility's permit includes effluent limitations at this outfall for BOD, COD, TSS, pH, sulfide, total chromium, copper, lead, cadmium, silver, total residual chlorine, fecal coliform, nickel, aluminum, zinc, phenols, and whole effluent toxicity. 
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-65. 
Exhibit A-65: Summary of Available Effluent Data for Kenyon Industries, Inc. (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Aluminum 
                                                                             21
                                                                           296 
                                                                        33,400 
                                                                             - 
Ammonia
                                                                             64
                                                                        12,850 
                                                                        59,100 
                                                                            10 
Cadmium
                                                                             64
                                                                             - 
                                                                          0.05 
                                                                          0.05 
Chlorine
                                                                             64
                                                                            40 
                                                                           320 
                                                                            10 
Chromium (III)
                                                                             64
                                                                           154 
                                                                           345 
                                                                               
Copper
                                                                             64
                                                                         171.5 
                                                                           254 
                                                                           0.5 
Lead
                                                                             64
                                                                           1.0 
                                                                           8.0 
                                                                           0.6 
Nickel
                                                                             21
                                                                           6.0 
                                                                            60 
                                                                           0.5 
Nitrates
                                                                             64
                                                                        31,550 
                                                                        74,300 
                                                                             2 
Phenol
                                                                             64
                                                                          69.5 
                                                                           191 
                                                                          0.14 
Silver
                                                                             64
                                                                             - 
                                                                      0.050[b] 
                                                                           0.1 
Zinc
                                                                             21
                                                                          38.0 
                                                                           115 
                                                                          0.05 
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] This value is below the DL and is based on the assumption used in this analysis that measurements reported as "<" or "not quantified" are one-half of the DL.
Exhibit A-66 summarizes the RPA for all parameters with sufficient data. The fact sheet for the existing permit authorizes mixing zones for this facility, which EPA used in the RPA. Ambient data were not available for the receiving water, so EPA assumed background concentrations were equal to half the DL unless that value was above the applicable criteria.
Exhibit A-66: Summary of Reasonable Potential Analysis for Kenyon Industries, Inc. (ug/L)
 Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Aluminum
                                                                          9,705
                                                                          9,705
                                                                              -
                                                                            750
                                                                             87
                                                                              -
                                      Yes
                                      N/A
Ammonia
                                                                          4,247
                                                                          4,247
                                                                              -
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Cadmium
                                                                        0.00816
                                                                       0.00786 
                                                                              -
                                                                            1.8
                                                                           0.72
                                                                              -
                                      No
                                      N/A
Chlorine
                                                                           25.6
                                                                           25.6
                                                                              -
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Chromium (III)
                                                                           5.77
                                                                           15.7
                                                                              -
                                                                            570
                                                                             74
                                                                              -
                                      No
                                      N/A
Copper
                                                                           12.6
                                                                           12.6
                                                                           1.90
                                                                            4.4
                                                                            2.7
                                                                          1,300
                                      Yes
                                      No
Lead
                                                                           0.52
                                                                           0.52
                                                                               
                                                                             65
                                                                            2.5
                                                                              -
                                      No
                                      N/A
Nickel
                                                                           11.6
                                                                           11.5
                                                                           0.43
                                                                            470
                                                                             52
                                                                            180
                                      No
                                      No
Nitrates
                                                                              -
                                                                              -
                                                                            305
                                                                              -
                                                                              -
                                                                         10,000
                                      N/A
                                      No
Phenol
                                                                              -
                                                                              -
                                                                           2.21
                                                                              -
                                                                              -
                                                                          4,000
                                      N/A
                                      No
Silver
                                                                         0.0086
                                                                              -
                                                                              -
                                                                            3.2
                                                                              -
                                                                              -
                                      No
                                      N/A
Zinc
                                                                           8.85
                                                                           8.92
                                                                           1.20
                                                                            120
                                                                            120
                                                                          2,600
                                      No
                                      No
Note:
[a] Dilution factors for acute and chronic criteria (25.5), carcinogenic human healthy (103.7), and non-carcinogenic human health (32.4) were devised for this analysis.
As shown above, aluminum, ammonia, chlorine, and copper have reasonable. Exhibit A-67 summarizes the effluent limitations that were calculated as part of the RPA for Kenyon Industries.
Exhibit A-67: Summary of Calculated Limits for Parameters with Reasonable Potential for Kenyon Industries, Inc. (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Aluminum
                                      AL
                                                                          1,200
                                                                          3,700
                                                                         33,400
                                      Yes
Ammonia
                                      AL
                                                                         32,000
                                                                        104,000
                                                                         59,100
                                      Yes
Chlorine
                                      AL
                                                                            190
                                                                            480
                                                                            320
                                      Yes
Copper
                                      AL
                                                                             57
                                                                             82
                                                                            254
                                      Yes

Summary
Aluminum was measured from July 2016 through March 2021. The 21 measurements ranged from 87 to 33,400 ug/L and averaged 3,409 ug/L, which exceeds the AML of 1,200 ug/L and the maximum daily limit of 3,700 ug/L. Additional treatment may be necessary in order to comply with effluent limits derived from the economic analysis criteria. The facility can actively remove aluminum with a process such as chemical precipitation or ion exchange. EPA estimated the incremental cost to this facility of adding chemical precipitation or ion exchange to the existing treatment system and implementing a P2 program to reduce effluent concentrations of aluminum.
The effluent limits for ammonia derived from the potential baseline WQS are an AML of 32 mg/L and MDL of 104 mg/L. DMR data suggest that the facility meets the proposed AML about 54% of the time during the monitoring period from January 2016 to April 2021 that included 64 measurements. The facility currently meets the proposed MDL all the time, but a facility upgrade may be necessary to ensure compliance with the AML. EPA estimated the cost of a facility upgrade to include an additional nitrification step in the treatment process. 
Copper was measured from July 2016 through April 2021. The 64 measurements ranged from 0.18 to 254 ug/L and averaged 168 ug/L, which exceeds the AML of 57 ug/L and MDL of 82 ug/L. To meet these effluent limits derived from the economic analysis criteria additional treatment may be necessary. The facility can evaluate P2 activities and active removal with a process such as chemical precipitation or ion exchange. EPA did not estimate additional incremental cost to the facility of adding chemical precipitation or ion exchange beyond the cost for these treatment processes for removal of aluminum. EPA did estimate the incremental cost of implementing an additional P2 program to reduce effluent concentrations of copper.
The facility had 64 detected measurements of chlorine from January 2016 to April 2021. The average of these detected measurements was 57.5 ug/L and the data ranged from 0.04 to 320 ug/L. No measurements exceeded the MDL derived from the economic analysis criteria, and only a single measurement exceeded the AML. Therefore, EPA did not estimate additional costs for treatment to meet chlorine limits at this facility.
Exhibit A-68 summarizes the estimated incremental costs for this facility.
Exhibit A-68: Kenyon Industries Estimated Incremental Costs (0.55 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                   $512,843
                                      $0
                                    $45,800
                                    $80,271
                                    $94,209
Aluminum, Copper
Chemical Precipitation
                                  $1,269,157
                                      $0
                                   $350,130
                                   $435,437
                                   $469,929

Small Facility P2 Program
                                      $0
                                    $33,114
                                      $0
                                    $19,868
                                    $19,868

                 Alternative Treatment for Aluminum and Copper

Ion Exchange
                                  $1,195,903
                                      $0
                                   $119,786
                                   $200,169
                                   $232,671

Small Facility P2 Program
                                      $0
                                    $33,114
                                      $0
                                    $19,868
                                    $19,868
TOTAL:
                            $1,708,746 -$1,782,000
                                    $33,114
                              $165,586 -$395,130
                              $300,308 -$535,576
                              $346,748 - $584,006
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Roberto R. Bustamante WWTF (TX0101605)
The Roberto R. Bustamante WWTF (Bustamante WWTF; NPDES permit number TX0101605) in El Paso, Texas, discharges treated domestic wastewater to either the Riverside intercepting drain or Riverside Canal of the Rio Grande River.
EPA could not locate permit documentation for this facility and based the analysis on discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The Roberto R. Bustamante WWTF reported permitted flow capacity is 39 MGD. The facility employs extended aeration activated sludge processes, biological nitrification.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-69.
Exhibit A-69: Summary of Available Effluent Data for Bustamante WWTF (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Ammonia
                                                                             35
                                                                          3,340
                                                                          5,420
                                                                             10
Chlorine
                                                                             55
                                                                          3,250
                                                                          3,810
                                                                             10
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-70 summarizes the RPA for all parameters with sufficient data. Critical flow data were not available; therefore no dilution was assumed for the RPA. 
Exhibit A-70: Summary of Reasonable Potential Analysis for Bustamante WWTF (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Ammonia
                                                                          8,300
                                                                          8,300
                                                                          3,340
                                                                         11,000
                                                                          1,400
                                                                              -
                                      Yes
                                      N/A
Chlorine
                                                                          4,100
                                                                          4,100
                                                                          3,250
                                                                             19
                                                                             11
                                                                              -
                                      Yes
                                      N/A
Note:
[a] No dilution was used for this analysis.
As shown above, ammonia and chlorine have reasonable potential to exceed WQBELs derived from the economic analysis criteria. Exhibit A-71 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the WWTF. 
Exhibit A-71: Summary of Calculated Limits for Parameters with Reasonable Potential for Bustamante WWTF (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                                                          1,400
                                                                          2,600
                                                                          5,420
                                      Yes
Chlorine
                                      AL
                                                                             11
                                                                             12
                                                                          3,810
                                      Yes

Summary
DMR data show that the facility reports an average effluent ammonia concentration of 3.4 mg/L, with concentrations ranging from 1.0 to 5.4 mg/L during the monitoring period from January 2016 to December 2018, which included 35 measurements. Effluent limits derived from the economic analysis criteria are an AML of 1.4 mg/L and an MDL of 2.6 mg/L A facility upgrade will likely be necessary to meet the more stringent limits. EPA estimated the cost of adding a nitrification step in the treatment process for this facility. 
The facility also reported 55 detected measurements of chlorine from January 2016 to July 2020. The average of these detected measurements was 3,328 ug/L with concentrations ranging from 2,710 to 3,810 ug/L. All measurements exceeded the AML of 10 ug/L and the MDL of 12 ug/L derived from the economic analysis criteria. Therefore, EPA estimated the cost of additional de-chlorination treatment for this facility.
Exhibit A-72 summarizes the estimated incremental costs for this facility.
Exhibit A-72: Bustamante WWTF Estimated Incremental Costs (39 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                  $4,682,717
                                      $0
                                   $302,910
                                   $617,662
                                   $744,925
Chlorine
Dechlorination
                                  $8,177,283
                                      $0
                                   $313,799
                                   $863,441
                                  $1,085,676
TOTAL:
                                  $12,860,000
                                      $0
                                   $616,709
                                  $1,481,103
                                  $1,830,601
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
McKinley Paper Company (WA0002925)
McKinley Paper Company (McKinley Paper; NPDES permit number WA0002925) is one of two paper mills that McKinley USA -- a subsidiary of Bio Pappel International and the largest paper manufacturer for packaging, containing, wrapping, and newspapers in the country -- operates in the United States. The facility is located in Port Angeles, Washington. This plant produces 295 tons/day of telephone directory paper by way of thermo-mechanical pulping, de-inking pulping, and non-integrated semi-bleach kraft pulping systems. The facility discharges treated wastewater, filtered backwash, and stormwater into the Salish Sea's Strait of Juan de Fuca. 
EPA developed this facility analysis based on the 2019 permit and associated fact sheet issued by Washington's Department of Ecology together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
The McKinley Paper Company's Washington plant has a facility design flow of 12 MGD. The permit includes effluent limitations for BOD, TSS, oil and grease, and pH.
Before discharging, McKinley treats its wastewater and stormwater on site via primary settling, secondary activated sludge treatment, and secondary clarification. Outfall 001 discharges secondary effluent into the Strait, while Outfall 002 discharges filter plant backwash to the same receiving water.
Reasonable Potential Analysis
Discharge monitoring reports did not include sufficient data for any parameters for EPA to conduct an RPA; therefore, EPA estimated no incremental compliance costs for this facility. 
Domtar A.W., LLC WRC (WI0003620)
Domtar A.W., LLC WRC (Domtar WRC; NPDES permit number WI0003620) is a complex of paper, paper coating, and kraft pulp production facilities -- Nekoosa Mill and Nekoosa Coated Products, LLC -- in addition to the Wastewater Reclamation Center that treats process wastewaters from the production facilities and site landfill leachates. The Domtar WRC is located between Port Edwards and Nekoosa, while the two production facilities are located in Nekoosa city. Domtar WRC discharges treated wastewater through a Parshall flume for flow measurement, to the Wisconsin River via Outfall 002. The facility has a maximum annual average flow of 16.74 MGD and an actual average flow of 16.21 MGD.
EPA developed this facility analysis based on the 2018 permit and associated fact sheet issued by the Wisconsin Department of Natural Resources together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
Domtar WRC processes wastewaters that include all vacuum pump seal waters from Nekoosa mill, process wastewaters from Nekoosa Coated Products, ash-bark landfill leachate, and stormwater.
Treatment mechanisms include primary clarification, UNOX high purity oxygen activated sludge, and secondary treatment. For primary treatment, the WRC employs two lined lagoons that effect flow equalization, cooling, and partial BOD removal for primary clarifier effluent. The effluent then proceeds to the UNOX biological treatment system.
Reasonable Potential Analysis
EPA had sufficient data to conduct a reasonable potential analysis for chlorine, as shown in Exhibit A-73. 
Exhibit A-73: Summary of Available Effluent Data for Domtar A.W., LLC WRC (ug/L)
Parameter
Effluent Data[a] (ug/L)
Detection Limit

Samples
50[th] Percentile
Max

Chlorine
                                                                             50
                                                                         ND[b] 
                                                                             ND
                                                                            10
Notes:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
[b] Reported results for chlorine were all below the DL.
Exhibit A-74 summarizes the RPA for all parameters with sufficient data. There was no information on authorization of mixing zones, so EPA assumed no mixing zones for this analysis.
Exhibit A-74: Summary of Reasonable Potential Analysis for Domtar A.W., LLC WRC (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Chlorine
                                                                            0.0
                                                                            0.0
                                                                               
                                                                             19
                                                                             11
                                                                               
                                      No
                                      N/A
Note:
[a] No dilution was used in this analysis.
As shown above, the facility does not have reasonable potential for chlorine; therefore, no additional effluent limitations were calculated as part of this analysis.
Summary
EPA estimated no incremental compliance costs for this facility. 
City of Baraboo WWTP (WI0020605)
The City of Baraboo's WWTP (Baraboo WWTP; NPDES permit number WI0020605) is in Baraboo, Wisconsin, and discharges via Outfall 001 to the Baraboo River.
EPA developed this facility analysis based on the 2021 permit issued by the Wisconsin Department of Natural Resources together with discharge monitoring reports from between 2016 and 2021.
Effluent and Treatment Process
This facility has an annual average design flow of 2.53 MGD. The permit requires that Baraboo WWTP perform seasonal disinfection from May 1 through September 30 each year but does not provide any further information on POTW's treatment processes. The permit includes effluent limitations for BOD, TSS, pH, ammonia nitrogen, other nitrogen species, fecal coliform, bacteria (E. coli), phosphorus, mercury, and whole effluent toxicity.
Reasonable Potential Analysis
EPA had sufficient data to conduct reasonable potential analyses for the parameters shown in Exhibit A-75. 
Exhibit A-75: Summary of Available Effluent Data for the Baraboo WWTP (ug/L)
Parameter
Effluent Data[a]
Detection Limit

Samples
50[th] Percentile
Max

Ammonia
                                                                             12
                                                                         11,750
                                                                         25,000
                                                                             10
Chloride
                                                                             12
                                                                        250,000
                                                                        300,000
                                                                              4
Note:
[a] For aquatic life economic analysis criteria, the reasonable potential analysis uses an estimate of the 99[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration. For human health criteria, the reasonable potential analysis uses either 1) the 50[th] percentile concentration from the existing effluent data set if the effluent data set includes 10 or more observations or 2) an estimate of the 50[th] percentile effluent concentration statistically projected from the maximum observed effluent concentration if the effluent data set includes fewer than 10 observations. Thus, this table does not include a 50[th] percentile calculated from the effluent data set when there are less than 10 observations.
Exhibit A-76 summarizes the RPA for all parameters with sufficient data. Critical flow data were not available, and no dilution factors were used in this analysis. 
Exhibit A-76: Summary of Reasonable Potential Analysis for the Baraboo WWTP (ug/L)
Parameter
Conc at Edge of Mixing Zone[a]
Applicable Criteria
RP

Acute
Chronic
HH
Acute
Chronic
HH
AL
HH
Ammonia
                                                                        98,300 
                                                                        98,300 
                                                                        11,750 
                                                                        11,000 
                                                                         1,400 
                                       -
                                      Yes
                                      N/A
Chloride
                                                                       351,300 
                                                                       351,300 
                                                                       250,000 
                                                                       860,000 
                                                                       230,000 
                                       -
                                      Yes
                                      N/A
Note:
[a] No dilution was used for this analysis.
As shown above, there is reasonable potential for ammonia and chloride. Exhibit A-77 summarizes the average monthly and maximum daily effluent limitations that were calculated as part of the RPA for the Baraboo WWTP. 
Exhibit A-77: Summary of Calculated Limits for Parameters with Reasonable Potential for the Baraboo WWTP (ug/L)
Parameter
Limiting Criterion
Limits
Max Conc
Exceeds Limit?

AML
MDL

Ammonia
                                      AL
                                                                          1,400
                                                                          4,200
                                                                         25,000
                                      Yes
Chloride
                                      AL
                                                                        220,000
                                                                        250,000
                                                                        300,000
                                      Yes

Summary
DMR data show that effluent ammonia concentrations average 12.5 mg/L and ranged from 0.33 to 25.0 mg/L during the monitoring period from January 2016 to December 2017 that included 12 measurements. The effluent limits derived from the economic analysis criteria are an AML of 1.4 mg/L and MDL of 4.2 mg/L. A facility upgrade may be necessary to meet these limits.
The facility reported 12 detected measurements of chloride from January 2017 to December 2017. The average of these detected measurements was 257 mg/L and the data ranged from 230 to 300 mg/L. Many of the measurements exceeded the AML of 223 mg/L, and the MDL of 253 mg/L derived from the economic analysis criteria, indicating that the facility may need additional treatment for removal of chlorides.
However, while the current permit includes seasonal effluent limits and monitoring requirements for ammonia, it does not include effluent limits or monitoring requirements for chloride. Furthermore, available DMR data for ammonia and chloride are available only for January 2016 through December 2017. Reverse osmosis, which would be required for chloride removal, is an expensive technology not widely used for wastewater treatment.
Based on these considerations, and as summarized in Exhibit A-78, EPA is estimating costs for this facility based on the cost of an additional nitrification step for ammonia removal to concentrations that would be required under the economic analysis criteria and either a P2 program or both a WQS variance and P2 program for chloride.
Exhibit A-78: City of Baraboo WWTP Estimated Incremental Costs (2.53 MGD)
Parameter
Control Option
Capital Cost
Other One-Time Cost
O&M Cost
Annual Cost (3%)[a]
Annual Cost (7%)[b]
Ammonia
Nitrification
                                   $988,000
                                      $0
                                    $66,210
                                   $132,619
                                   $159,470
Chloride
Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

                 Alternative Compliance Mechanism for Chloride

Small Facility P2 Program
                                      $0
                                    $16,557
                                      $0
                                    $9,934
                                    $9,934

Variance Feasibility Analysis
                                      $0
                                    $45,164
                                      $0
                                      $0
                                      $0

Variance Application
                                      $0
                                   $127,840
                                      $0
                                      $0
                                      $0
TOTAL:
                                   $988,000
                                   $189,561
                                    $66,210
                                   $142,553
                                   $169,404
Notes:
[a] Capital costs annualized over 20 years at a 3% discount rate. Other one-time costs are not annualized.
[b] Capital costs annualized over 20 years at a 7% discount rate. Other one-time costs are not annualized.
Source Control and Alternative Compliance Mechanism Supplemental Information and Costs
Source Control (P2 Program) Costs
As discussed in Section 4.4.2, controlling the source of pollutants entering a facility through a P2 program would likely be the next most cost-effective control option after process optimization. Some pollutants may also be present as a result of processes within a facility (e.g., contaminants from industrial processes for industrial dischargers). EPA reviewed requirements of P2 programs primarily for pollutants that triggered RP for sewerage systems, such as copper. It is expected that many facilities would at least attempt to limit influent concentrations or reduce pollutants used in their processes by exploring pollutant sources upstream through a P2 program. 
Facilities seeking to limit their compliance costs are likely to implement P2 programs for the pollutants with effluent limits lower than what they are currently meeting, either as their main compliance mechanism, or in conjunction with another mechanism.
Copper is a pollutant that is prevalent and triggered RP for several facilities. A P2 program for copper for a POTW is likely to include: program development, sampling and analysis, workshops and other consultant work, advertising (i.e., public service announcements) and/or a website. Costs for these components were estimated as part of the economic analysis associated with EPA's copper and cadmium rule for the State of Oregon (EPA, 2016). EPA is estimating the cost of a P2 program for copper at a POTW and using this cost as an estimate for P2 programs and other programs to identify and reduce pollutants prior to treatment for all categories of facilities. This assumption may lead to overestimating costs for some facilities (e.g., industrial facilities that can more readily identify and eliminate the source of a pollutant in their effluent because of its control of processes and process inputs).
Because the current analysis includes Tribal lands spread across multiple states, EPA updated costs from EPA's 2016 Economic Analysis for the Final Rule: Aquatic Life Criteria for Copper and Cadmium in Oregon to reflect national-scale labor rates and 2020 dollars (Bureau of Labor Statistics  -  BLS, 2020a; BLS, 2020b), as well as costs per sample based on a representative national average. Exhibit B-1 shows the estimated program costs (in 2020 dollars) at the national level for a copper P2 program for a small, medium and large facility. Costs for P2 programs for all pollutants were estimated based on experience with P2 programs for copper. 
Exhibit B-1 Potential Initial and Annual Cost for P2 Program for Copper[a]
Facility Size
Initial Costs
Annual Costs
Small Facility (1-5 MGD)
$16,557
$9,934
Medium Facility (>5-20 MGD)
$33,115
$15,454
Large Facility (>20 MGD)
$49,672
$20,973
Note:
[a] Cost estimates are based on January 2015 to January 2020 inflation (BLS, 2021).
Alternative Compliance Mechanisms
WQS Variance
As noted in Section 4.4.4, dischargers are most likely to pursue a WQS variance based on economic infeasibility (40 CFR 131.10(g)(6)). Such an evaluation may require a comprehensive literature search and analysis of the data compiled from the search. The literature search may encompass general information identifying the treatment technologies capable of removing the pollutants of concern, background on the processes driving the removal or reduction of pollutants, and performance data showing the effluent levels demonstrated for WWTPs at pilot- and full-scale. Costs for these components were estimated as part of the economic analysis associated with EPA's copper and cadmium rule for the State of Oregon (EPA, 2016). Exhibit B-2 provides estimates of levels of effort that may be associated with technological feasibility analyses, based on EPA's recent cost estimates for Oregon (EPA, 2016). Because the current analysis includes Tribal land spread across the entire country, EPA updated these costs to reflect national labor rates. 
Exhibit B-2 Potential Level of Effort to Investigate Technological Feasibility for a Variance 
Component
Hours
Cost[a]
Literature search
180
$25,405
Write up and evaluation of theory and performance data from search
100
$14,114
Evaluation of existing treatment performance
40
$5,645
Total
320
$45,164
Note:
[a] All cost estimates are based on a labor rate of $141/hr, reflecting the average wage for an environmental engineer in the USA in 2020 dollars (BLS, 2020b) and multiplied by a factor of 3.03 to account for overhead, benefits, and profit (PSMJ, 2007).
To evaluate the potential for control costs to cause "substantial and widespread economic and social impacts" (the regulatory language to be satisfied), dischargers are likely to follow EPA's Interim Economic Guidance for Water Quality Standards, which provides worksheets and instructions for public and private sector entities (EPA, 1995). Following this workbook, dischargers conduct a two-step analysis, first determining whether the control costs would have a substantial adverse financial impact and, if so, whether that impact would cause widespread adverse impacts on the surrounding community. 
EPA based unit costs for WQS variances on estimates previously developed for the economic analysis associated with EPA's copper and cadmium rule for the State of Oregon (EPA, 2016). To account for a nationwide potential cost, EPA updated the Oregon costs to reflect national labor rates. Exhibit B-3 shows the cost for a variance under 40 CFR 131.10(g)(6) for economic and social impacts.
Exhibit B-3 Potential One-Time Cost to Apply for and Review WQS Variances for Economic and Social Impacts (40 CFR 131.10(g)(6))
Facility Size
Cost for Variance Preparation[a]
Small Facility (1-5 MGD)
                                   $127,840
Medium Facility (5-20 MGD)
                                   $255,680
Large Facility (>20 MGD)
                                   $383,520
Note:
[a] Based on a labor rate of $141/hr, reflecting the average wage for an environmental engineer in the USA in 2020 dollars (BLS, 2020b) and multiplied by a factor of 3.03 to account for overhead, benefits, and profit (PSMJ, 2007).
This analysis does not address costs associated with implementing controls necessary to meet the highest attainable condition, which may be intermediate between current performance and fully meeting the WQBEL associated with the proposed WQS. 
EPA may require facilities to implement a P2 or source control program as part of the conditions for granting a variance. Thus, to be conservative (i.e., err on the side of overestimating costs), EPA assumed that facilities would need to implement a P2 program as part of a variance program. 
 Dilution Credit
When applying for an RMZ, a specific study is required to estimate and document the level of mixing which is likely to be present in the receiving water under applicable critical conditions. A study of this type will typically require data collection and the mathematical modeling of the discharge and ambient receiving environment. In developing costs associated with developing a dilution special study, EPA estimated that an environmental engineer would spend approximately 320 hours to develop and interpret the model. EPA assumed the costs to obtain modeling software would be negligible, as EPA distributes software appropriate to this application (i.e., VisualPlumes) free of charge. Exhibit B-4 shows the costs for a dilution study. 
Exhibit B-4 Potential Costs for a Dilution Study
Component
Hours
Cost
Dilution Study[a]
                                      320
                                    $45,120
      Note:
      [a] Based on a labor rate of $141/hr, reflecting the average wage for an environmental engineer in the USA in 2020 dollars (BLS, 2020b) and multiplied by a factor of 3.03 to account for overhead, benefits, and profit (PSMJ, 2007).

References
BLS (Bureau of Labor Statistics). 2020a. May 2020 National Occupational Employment and Wage Estimates, United States. Water and Wastewater Treatment Plant and System Operators Wages (Occupation Code 51-8031). http://www.bls.gov/oes/current/oes_nat.htm.
BLS (Bureau of Labor Statistics). 2020b. May 2020 National Occupational Employment and Wage Estimates, United States. Environmental Engineer Wages (Occupation Code 17-2081). http://www.bls.gov/oes/current/oes_nat.htm.
BLS (Bureau of Labor Statistics). 2021. CPI Inflation Calculator. https://www.bls.gov/data/inflation_calculator.htm. 
EPA (United States Environmental Protection Agency). 1995. The Great Lakes: An Environmental Atlas and Resource Book. Third Edition. EPA 905-B-95-001. 
EPA (United States Environmental Protection Agency). 2016. Economic Analysis for the Proposed Rule: Aquatic Life Criteria for Copper and Cadmium in Oregon. 
PSMJ (PSMJ Resources, Inc.). 2007. A/E Financial Performance Survey, 27th Edition: CEO Snapshot.

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Effluent Treatment Control and Costs
Based on the RPAs, analysis of monitoring data, and best professional judgement, described in detail in Appendix B, the pollutants that require further reduction are aluminum, ammonia, chloride. chlorine, chromium VI, copper, cyanide, manganese, nonylphenol, selenium, THMs, and zinc. 
The first step for a treatment facility is to optimize the existing treatment process(es) with minor modifications. For ammonia removal, it is important to have adequate control of biochemical oxygen demand (BOD), alkalinity, air supply, and proper control of oxygen. For THM reduction, a THM precursor removal prior to disinfection, a different injection point for chlorine in the process, or a different type of disinfectant should be considered. After treatment optimization is completed and if further reduction is required, an effluent treatment may be considered. Effluent treatments evaluated for the purposes of this analysis include:
Treatment process optimization
Chemical precipitation
Ion exchange (IX)
GAC
Nitrification
Dechlorination
Reverse osmosis (RO) 
Treatment Process Optimization
Treatment optimization costs (e.g., a few probes, addition of a carbon source or other chemicals) are typically minimal compared to effluent investments, and more importantly, are facility and treatment process-specific, and cannot be costed without an understanding of the specific facility. EPA assumed zero to minimal cost for most treatment process optimization actions.
Under process optimization, each unit process should be reviewed for target pollutant(s) removal, for example: 
Dissolved oxygen and an oxidation-reduction or ammonia probe could be considered in the biological treatment for ammonia removal
A change in the application point for disinfectant or use of a different disinfectant could be considered in the process stream for THM reduction (Metcalf and Eddy, 2013; HACH, 2016). 
Ammonia is removed when the ammonium ion (ammonia in water) is converted into nitrites and nitrates. These reactions require adequate amount of oxygen, alkalinity, and BOD. In the wastewater industry, biological processes are likely already equipped with dissolved oxygen, pH, and oxidation-reduction and/or ammonia probes to provide the information for process control and optimization of nitrification. To reduce ammonia concentrations, and comply with calculated WQBELs, some facilities may incur no cost or the minimal cost for a process analysis (similar to the one-time cost of a pollution prevention program).
Similarly, improving TDS removal will remove a portion of the THM precursors, which will reduce the formation of THMs during the disinfection (chlorination) process. A change of disinfectant application point(s) may also reduce the formation of THMs. Another option is to select a different disinfectant, such as a UV system, chlorine dioxide, and others. (Metcalf and Eddy, 2013). Addressing THMs is part of facility optimization, and EPA estimated no cost in addressing these pollutants. 
Chemical Precipitation
Chemical precipitation is a common practice in wastewater treatment. Many metals can be removed from wastewater by the addition of chemical reagents that cause the metal to form a solid, which can be settled, filtered, or otherwise removed from the system prior to discharge (EPA, 2000a). The removal of metals (such as copper, aluminum, and zinc) can often be achieved by adding one or more compounds that create insoluble metal carbonates or hydroxides that are then physically removed from the water (EPA, 2000a). Typical additives include lime (calcium oxide), ferrous sulfate, and alum (EPA, 2000a). These precipitation processes are influenced by pH and sometimes dissolved oxygen, to be effective. The amount of chemical used in the precipitation process can vary depending on pH, alkalinity, the point of injection and mixing performed post injection (EPA, 2000a). Often a benchtop analysis is performed to optimize the amount and specific additive mixture needed to perform optimally for a given wastewater treatment system. 
EPA (2000a) summarized the advantages and disadvantages of chemical precipitation:
Advantages
Chemical precipitation is a well-established technology with ready availability of
equipment and many chemicals.
Some treatment chemicals, especially lime, are very inexpensive.
Completely enclosed systems are often conveniently self-operating and low maintenance, requiring only replenishment of the chemicals used. Often times, a sophisticated operator is not needed.
Disadvantages
Competing reactions, varying levels of alkalinity and other factors typically make calculation of proper chemical dosages impossible. Therefore, frequent jar tests are necessary for confirmation of optimal treatment conditions. Overdosing can diminish the effectiveness of the treatment.
Chemical precipitation may require working with corrosive chemicals, increasing operator safety concerns.
The addition of treatment chemicals, especially lime, may increase the volume of waste sludge up to 50 percent.
Large amounts of chemicals may need to be transported to the treatment location.
Polymers can be expensive.
A typical chemical precipitation system has an automatic chemical feed component that adds the chemical(s), monitors the process, and controls the amounts being added. The components may include storage tanks, feed tanks, metering pumps (or other type of conveyance), overflow containment basins, mixers, aging tanks, injection ports, injection controls, pipes and fittings, and valves (EPA, 2000a). The specific system components will vary according to the chemicals being used; whether they are wet, gaseous, or dry; how corrosive each chemical is, and the volumes required. 
For aluminum, copper, and zinc control, mixtures of lime and ferrous sulfate may be used and for manganese removal, potassium permanganate may be used. For costing purposes, EPA assumed ferrous sulfate addition for chemical precipitation. In the costing analysis, for facilities where available information indicated that the treatment system currently has primary clarifiers, these clarifiers were specified as adaptable for the chemical precipitation/coagulation phase of the process. In the analysis, EPA made the conservative assumption that filtration would be added as a tertiary treatment process.
Nitrification
In some systems, the biological treatment process (oxidation ditch, activated sludge, lagoon, etc.) is not designed to sufficiently to remove ammonia to levels required in the ammonia criteria used as the basis for calculating WQBELs in the analysis. The first step for a facility with elevated ammonia levels should be an evaluation of the treatment processes that includes process modeling and optimization. When the modeling and optimization do not provide effluent levels of ammonia required to meet the criteria, additional process modifications are necessary to reduce the ammonia levels in the effluent. 
Nitrification is the process of biologically converting ammonia to nitrite and then to nitrate using nitrifying bacteria. The process is aerobic, so sufficient oxygen in the treatment system is essential. Also, alkalinity is consumed in the nitrification process, so some systems may require alkalinity additions to the process water. 
Nitrification processes in wastewater treatment can be achieved in fixed film reactors where a biofilm (containing nitrifying bacteria) is grown on some form of media in the process. For this analysis, several fixed film reactors were evaluated including trickling, rotating biological contactor (RBC), and moving bed biological reactor (MBBR). Nitrification can also be achieved in suspended growth processes where the bacterial film attaches to solids in the process water. Examples of suspended growth nitrification systems include oxidation ditches, sequencing batch reactors, and a variety of proprietary multi-stage reactors. Additional information on nitrification can be found in EPA fact sheets such as Trickling Filter Nitrification (EPA, 2000b). For costing purposes, EPA assumed the addition of a nitrifying trickling filter when an additional nitrification step was required.
Chlorination
Cyanide can be treated in wastewater with an alkaline oxidation process. This two-step process uses chlorine (using hypochlorite or chlorine gas) to oxidize cyanide to cyanate in an alkaline environment (which is achieved by adding a strong base, typically sodium hydroxide). Next cyanate is oxidized to carbon dioxide and nitrogen by adding more chlorine to the process water (Sensorex, 2021). 
Control of the system pH is essential in the conversion of cyanide to cyanate, so the process typically uses pH and oxidation-reduction potential (REDOX or ORP) sensors to help control the reactions (Sensorex, 2021). Chlorine and sodium hydroxide are added and mixed in the first step. The system pH is maintained at 10-11.5 and the ORP is controlled at 250-400mV for optimal results (Sensorex, 2021). In the second phase, the system pH is reduced to 8.5-9 and ORP maintained at 300-600mV for optimal results (Sensorex, 2021). 
Dechlorination
Dechlorination removes excess or residual chlorine from a waste stream prior to discharge. The most common dechlorination process uses sulfur dioxide. Other additives that can be used to dechlorinate water include carbon adsorption (see below), sodium metabisulfite, sodium bisulfite, and hydrogen peroxide (EPA, 2000c). Using sulfur dioxide requires equipment similar to the equipment used in systems that use chlorine gas for chlorination. Both chlorine gas and sulfur dioxide are dangerous and require numerous safety precautions to be in place. A typical dechlorination system has a chemical storage and delivery system, contact chambers, mixing, and sensors placed in the process water to ensure optimal results (EPA, 2000c). For costing purposes, EPA assumed that dechlorination would be accomplished using sodium sulfite (dry chemical) in a contact chamber.
Ion Exchange (IX)
Ion exchange technology has been designed to remove dissolved and ionic forms of pollutants from wastewater using resins selected specifically for their pollutant removal properties. The treatment system relies on adsorption and chemical bonding of ions through ion exchange, and works best when waste streams are pretreated to remove suspended and dissolved solids to enhance pollutant removal and eliminate competing ions (NDWC, 1997).
The ion exchange process consists of four operations: service, backwash, regeneration, and rinse. In the service step, the resin is contacted with the influent water. The resin is considered spent once it can no longer remove the desired amount of pollutant. Next, the backwash step is initiated to expand the bed and to remove fines that may be clogging the packed bed. The spent resin is regenerated using a concentrated solution of the original exchange ion, reversing the exchange process. Lastly, the rinse step removes excess regeneration solution before the column is brought back online for the next service cycle. Note that some sorbents cannot be regenerated, and once they are spent (i.e., there is no more capacity to adsorb copper, cyanide, and others), they are disposed of and replaced with fresh media. Advantages of ion exchange technology include:
A large variety of specific resins are available from manufacturers, tailored to removal of specific pollutants; and
Pollutants can be recovered from most resins upon regeneration (NDWC, 1997).
Use of ion exchange also has disadvantages:
Management and disposal of spent media or regenerated brine can be costly, due to high concentrations of the waste effluent;
Effluent quality may be highly variable (depending on sorbent loading); 
To achieve low pollutant levels in wastewater, extensive pretreatment may be necessary; and
Ion exchange units are sensitive to the presence of competing ions (NDWC, 1997).
For copper, historically, the use of sorbent resins has been limited to strong acid cationic resins applied to industrial wastewater containing inorganic copper and calcium. The selectivity of copper is less than that for calcium. Certain cationic resins can also be used to remove copper because they have a high selectivity for copper. Another resin that can be used to remove copper is a chelating resin, such as amidoxime chelating resin which is designed for removal of cations of metals, such as copper and iron from water at relatively low pH. Also, a typical ion exchange system is often designed with lead and lag vessels. When the treatment system is properly designed and maintained, the expected copper removal can reach 95 percent (WesTech, 2016). 
Granular Activated Carbon
GAC has been used successfully in advanced treatment of municipal and industrial wastewater for years. GAC is primarily used to adsorb refractory organics, such as 4,4'-DDT, alpha-BHC, dioxin, bis(2-ethylhexyl) phthalate, PCBs, THMs as well as residual amounts of inorganics such as nitrogen, sulfides, and heavy metals (Metcalf and Eddy, 2013). However, water-soluble compounds and small molecules are not adsorbed well (NAVFAC, 2008).
GAC adsorption occurs when pollutant molecules adhere to the internal walls of pores in carbon particles produced by thermal activation (EPA, 2000d). At municipal WWTPs, GAC is usually installed prior to disinfection, but after filtration (or some other type of pretreatment) that removes suspended solids in order to prevent fouling and maximize the time before breakthrough occurs (i.e., the point at which the pollutant is no longer absorbed).
Advantages of GAC include the following:
Proven, reliable technology for removing dissolved organics
Low space requirements
Easy to incorporate into existing systems (EPA, 2000d).
However, GAC is not without its disadvantages, including:
Under certain conditions, hydrogen sulfide may be generated from bacterial growth, creating odor and corrosion problems
Wet GAC is highly corrosive and abrasive
Requires pretreated wastewater with low suspended solids, and little variations in pH, temperature, and flow rate (EPA, 2000c)
Spent carbon may be a hazardous waste
Spent carbon must be regenerated or disposed of and the adsorbed pollutants must be destroyed, often by incineration (possibly re-releasing pollutants into the environment; organic pollutants are usually thermally degraded)
The presence of multiple pollutants can affect the process performance due to competitive adsorption of different classes of compounds; bench tests may be conducted to estimate carbon usage for mixtures
Some common chlorinated pollutants are weakly sorbed, resulting in low GAC capacity
Type and pore size of the carbon, as well as the operating temperature, must be carefully selected to optimize pollutant removal (NAVFAC, 2008).
EPA was not able to find any studies demonstrating GAC organics removal at WWTPs, although there are several plants throughout the country using GAC either to supplement secondary treatment or to enhance phosphorus removal. EPA's PCS database for these facilities contains no effluent data for toxic pollutants. GAC has been used for a number of groundwater cleanup operations. However, the removal rates vary based on the specific pollutant, quality of the source water, and operating parameters of the GAC unit (e.g., single versus dual stage).
Although GAC can remove low concentrations of certain metals, it has not been widely used for this purpose possibly due to the fact that spent carbon used for metals removal can be difficult to regenerate and may require treatment and/or disposal as a hazardous waste (EPA, 1991).
Use of this type of GAC for heavy metal removal at WWTPs discharging to surface waters has not been demonstrated on a full scale. The major disadvantage to this type of GAC it that it cannot be regenerated, so once its capacity is exhausted, it must be replaced with new media, which can be costly.
Reverse Osmosis (RO)
Theoretically, reverse osmosis (RO) can remove nearly all inorganic pollutants from water, (NDWC, 1997), as well as viruses and most organic pollutants, including some pesticides. The process removes pollutants from water using a semi-permeable membrane that permits only water molecules to pass through its pores. The contaminated water is subjected to high pressures that force pure water through the membrane, leaving pollutants behind in a brine solution (NDWC, 1997).
Properly operated RO units can achieve 96 percent removal of arsenic (III), arsenic (IV), barium, cadmium, chromium (III), chromium (VI), fluoride, lead, mercury, nitrite, selenium (IV), selenium (VI), and silver (NDWC, 1997). They will also likely achieve 95 percent removal of copper (WestTech, 2016). Multiple RO units operated in series, however, are capable of nondetectable or almost 100 percent removal rates (NDWC, 1997). RO has several advantages, including:
Removal of nearly all pollutant ions and most other dissolved pollutants
Relatively insensitive to flow and total dissolved solids levels
Also removes bacteria and particulates (NDWC, 1997).
However, despite these claims, there are no full scale performance data available from WWTPs discharging to surface waters that indicate that such removals are possible at these facilities on a consistent basis. This may be due to the fact that few, if any, facilities have been required to reduce toxic pollutants to such low levels through the use of end- of-pipe treatment. The use of RO for treating wastewater is limited, and therefore performance data are scarce. 
Even if the necessary pollutant levels are achievable with RO, it is important to consider the potential disadvantages and limitations of this technology, including:
Capital and operating (including energy) costs are high, and the latter increase with decreasing desired effluent concentrations;
Management and disposal of residuals (brine and media) is potentially costly and problematic;
Expensive pretreatment may be required to maintain the high treatment efficiency levels needed to achieve extremely low levels of pollutants (e.g., carbon prefilter for the reduction of chlorine, which can damage some types of chlorine sensitive RO membranes, sediment pre-filter or microfiltration to ensure that fine suspended materials do not clog the membrane);
Membranes are prone to fouling (NDWC, 1997);
The technology may not be feasible for treatment of large flows; and
RO does not remove pollutants from the environment, rather transfers them to another medium (pollutants are concentrated in the reject discharge or brine).
The most limiting of these disadvantages, especially for larger systems, is the management and disposal of residuals. Most RO systems reject about 10% to 25% of influent water as a concentrated brine solution (EPA, 1996). This brine contains the pollutants removed from the wastewater and must be treated prior to disposal. The more feasible residual disposal options for WWTPs include:
Land disposal (e.g., evaporation pond, underground injection)
Treatment (e.g., brine concentrator, thermal evaporation) (Metcalf and Eddy, 2013).
The first option requires that the waste be classified as nonhazardous. Otherwise, the brine must be disposed of as a hazardous waste, which can be extremely costly, especially for larger volumes. The land disposal option also may require a large amount of land, and if evaporation ponds are the only land disposal option, precipitation rates cannot be greater than evaporation rates. The treatment through controlled evaporation is feasible, although operating and maintenance costs may be extremely high. This approach is usually only employed where no other alternatives are available (Metcalf and Eddy, 2013).
In addition, these disposal options do not guarantee that the pollutants in the residuals will not be re-released into the environment. The pollutant is simply transferred from the effluent to a residual brine that must be disposed of in some manner. 
Because no WWTPs in the country have installed RO to remove toxics to very low levels for discharges to surface waters, there is no information on installed costs. Nor is information available from similar industrial applications. However, EPA contacted RO system manufacturers to obtain price quotes on RO system configurations set up to meet these low copper levels. Exhibit C-5 summarizes the assumptions used by the manufacturer to price an RO unit. 
Exhibit C-5 Parameters Provided for Costing RO and Ion Exchange Systems for Wastewater
Component
Input Value
Hardness
                                   140 mg/L
Alkalinity
                                   140 mg/L
pH
                                      7.5
Temperature
                                    20° C

Scaling is a concern in RO operation; the scaling potential may limit the water recovery percentage of each RO unit. The less water that is recovered from each unit, the greater volume of residual brine that needs treatment and disposal, thus increasing capital and operating costs. If the concentration of barium or sulfate is higher than shown in the exhibit, or if silica is present, water recovery could be limited.
Certain RO membranes are intolerant of free chlorine, and most microfiltration membranes have limited chlorine tolerance. Thus, prior to microfiltration, the wastewater should be dechlorinated if chlorine is used in previous treatment units. Note that dechlorination may result in an increase in sulfate ions, which, as mentioned above, could contribute to the scaling potential of the RO membranes. Costs may be higher than shown to account for these factors.
For the Los Alamos National Laboratory in Arizona, EPA considered two options for brine management: evaporation ponds with land application and blending with the plant's biosolids and hauling away for off-site disposal. Cost estimates do not include land cost, which may be federally owned, or the hauling cost because biosolids are most likely already being hauled and the tipping charge is assumed to be on a contract basis. Both options provide a range of disposal costs. The cost of land application rate (Tetra Tech, 2012) was adjusted to 2017 dollars. For disposal with biosolids, the final pollutant concentration of the blend of biosolids and brine concentrate may limit disposal options. 
Costing Discussion
For this economic analysis, EPA used CapdetWorks, which is a software tool for preliminary, planning-level design and cost estimation for WWTP construction project alternatives that is based on the CAPDET program originally developed by the U.S. Army Corps of Engineers (USACE). CapdetWorks designs user-specified unit processes based on influent characteristics and then estimates the capital and operation and maintenance (O&M) costs of the design. 
Capital cost estimates in CapdetWorks depend on several factors, including equipment cost for treatment units, land cost, construction labor wages, and other direct and indirect construction costs. CapdetWorks allows the user to overwrite default values for the equipment cost indices, land cost, and construction labor rate used in the program. EPA used construction cost indices for 2020 provided in CapdetWorks and construction labor rates based on construction worker wages from the Bureau of Labor Statistics (BLS) for 2020. 
O&M cost estimates in CapdetWorks consist of several components: operation, maintenance, material, chemicals, and energy. Operation costs are further divided by type of labor and include WWTP operator, administrative, and laboratory labor costs. Calculations in CapdetWorks assume that wages for administrative staff (e.g., plant managers, clerical staff) are, on average, the same as wages for WWTP operators. CapdetWorks allows the user to overwrite default values for labor rates and energy costs. EPA used labor rates based on BLS 2020 wage data and energy rates based on the 2020 national average electricity cost to commercial customers. WWTP operator, administrative, and laboratory labor make up the CapdetWorks estimate of operation costs while maintenance cost estimates in CapdetWorks consist solely of WWTP operator labor. 
For this assessment EPA estimated costs of additional treatment units using CapdetWorks by evaluating incremental costs above the cost of a baseline treatment system. Baseline systems for each facility were defined in CapdetWorks as a simplified version of the facility's existing treatment system as described in available information from NPDES permits and fact sheets or other available facility descriptions.
 References
EPA (United States Environmental Protection Agency). 1991. Engineering Bulletin: Granular Activated Carbon Treatment. EPA/540/2-91/024. 
EPA (United States Environmental Protection Agency). 2000a. Wastewater Technology Fact Sheet: Chemical Precipitation. EPA 832-F-00-018. 
EPA (United States Environmental Protection Agency). 2000b. Wastewater Technology Fact Sheet: Trickling Filter Nitrification. EPA 832-F-00-015.
EPA (United States Environmental Protection Agency). 2000c. Wastewater Technology Fact Sheet: Dechlorination. EPA 832-F-00-022.
EPA (United States Environmental Protection Agency). 2000d. Arsenic Removal from Drinking Water by Ion Exchange and Activated Alumina Plants. EPA 600-R-00-088.
HACH (HACH Company). 2016. Personal Communication with HACH Sales Representative for DO, pH, Oxidation/Reduction, and Ammonia Probes.
Metcalf and Eddy. 2013. Wastewater Engineering: Treatment and Reuse. Fifth Edition. McGraw Hill, Boston, MA
NAVFAC (Naval Facilities Engineering Command). 2008. Environmental Restoration and BRAC: Granular Activated Carbon (GAC) Adsorption (Liquid Phase). https://portal.navfac.navy.mil/portal/page?_pageid=181,5782928&_dad=portal&_schema=PORTAL. 
NDWC (National Drinking Water Clearinghouse). 1997. Tech Brief: Ion Exchange and Demineralization. https://wcwc.ca/wp-content/uploads/2021/01/NESC-Tech-Brief_Ion-Exchange-and-Demineralization.pdf?msclkid=26782e07b12b11ec81b8cf13d750e1b6.
Sensorex. 2021. What You Need to Know About Cyanide Wastewater Treatment. https://sensorex.com/blog/2016/04/26/cyanide-wastewater-treatment/ 
Tetra Tech (Tetra Tech, Inc.). 2012. Biosolid Management System Alternatives Study - Wastewater Documentation Updates. http://media.ktoo.org/2013/09/Biosolids_Report.pdf?msclkid=79256c83b12b11ec85c40a6c2fcbe5e0. 
WesTech (WesTech Engineering). 2016. Personal communication with Jon Farrell and Lindsay Horsley. For pricing of Ion Exchange and RO systems
--------------------------------------------------------------------------------
Pollutant Impacts
Exhibit D-1 identifies the parameters with potential human health impairments in Indian reservation waters, the number of water bodies with potential impairment (as identified in Section 6.2), and a description of the contaminants' human health impacts and the cancer classification according to the Agency for Toxic Substances and Disease Registry (ATSDR).
Exhibit D-1 Parameters with Potential Human Health Criteria Impairments and Adverse Health Impacts[a]
Parameter
Potentially Impaired Waterbodies
Affected Organ Systems
Antimony
                                       1
Cardiovascular, respiratory
Barium
                                       1
Cardiovascular, gastrointestinal, 
Copper
                                       1
Gastrointestinal, hematological, hepatic, respiratory, endocrine, ocular, neurological, reproductive
Dieldrin
                                       1
Developmental, endocrine, hepatic, immunological, neurological, cardiovascular, reproductive
E. coli
                                      68
Gastrointestinal
Enterococci
                                       3
Gastrointestinal
Manganese
                                      56
Cardiovascular, neurological, respiratory, hematological, reproductive
Methylmercury
                                       1
Developmental, neurological, renal
Nickel
                                       1
cardiovascular, dermal, immunological, respiratory, renal, reproductive, developmental, gastrointestinal, hepatic, renal
Nitrates
                                      18
Gastrointestinal, hematological, endocrine, dermal
pH
                                      54
Acidic conditions may cause other pollutants to dissolve, increasing exposure to and toxicity of metals, for example
Zinc
                                       1
Gastrointestinal, hematological, respiratory, ocular, homeostatic, immunological
Notes:
[a] Source: based on Agency for Toxic Substances and Disease Registry (ATSDR). Toxic Substances Portal.
Exhibit D-2 describes the potential environmental concerns associated with potential impairments, specifically related to aquatic species. 
Exhibit D-2 Parameters with Potential Aquatic Life Impairments and Adverse Impacts to Aquatic Species[a]
Parameter
Potentially Impaired Waterbodies
Environmental Concern
Alkalinity
                                      114
Important for fish and other aquatic life in freshwater systems because it is a measure of the buffering capacity of the water, and since pH has a direct effect on organisms as well as an indirect effect on the toxicity of certain other pollutants in the water, this buffering capacity is important to water quality
Aluminum
                                      15
Elevated levels of aluminum can affect some species ability to regulate ions, like salts, and inhibit respiratory functions, like breathing. Aluminum can accumulate on the surface of a fish's gill, leading to respiratory dysfunction, and possibly death.
Ammonia
                                       2
Impairment of gill ionoregulation and/or respiratory dysfunction or polymerization of aluminum hydroxides on the gill surface during alkalinization of water passing over the gills
Arsenic
                                       2
Causes poisoning of the liver and kidney in fish
Cadmium
                                       3
Accumulates majorly in stomach, liver and gills in fish; at sub-lethal levels it can produce toxic effects on the hepatic, immunological and hematological functions of fish
Chloride
                                       1
Elevated levels observed in fish with liver and blood abnormalities
Chlorine
                                       3
Elevated concentrations are toxic to fish; at lower concentrations, it stresses fish by damaging their gills
Chromium (III)
                                       1
Destabilizes the ecosystem due to their toxic impact on biota and bioaccumulation in certain organisms. Also produces cytotoxicity and detrimental impact on behavior of fish such as hypertrophy and paraplegia at gill epithelium, uneven swimming and suspended feeding. 
Copper
                                      14
Invertebrates with elevated levels require more energy to support their metabolism and therefore exhibit diminished growth. Several species of fish exposed to copper have exhibited damage to liver and muscle function, reproductive, developmental and metabolic functions
Iron
                                      22
Biota with elevated levels have exhibited sublethal effects including metabolic changes and abnormalities of the liver and kidneys, as well as disrupted reproductive and developmental functions
Lead
                                      11
Respiratory asphyxiation under extreme concentrations and the disruption of ionoregulatory homeostasis under more environmentally relevant concentrations
Methylmercury
                                       1
Biota with elevated levels have exhibited effects including metabolic changes and abnormalities of the liver and kidneys
Nickel
                                       1
Toxicity is associated with branchial lesions that cumulatively increase the diffusive distance across the gill epithelium, leading to impaired respiratory function
Oxygen, Dissolved
                                      60
Dissolved oxygen is used by almost all aquatic organisms for respiration, and, thus, is necessary for their survival. When insufficient amounts of dissolved oxygen available, fish and other aquatic organism cannot survive.
pH
                                      74
Acidic conditions may cause other pollutants to dissolve, increasing their fate and transport and increasing the potential for bioaccumulation in aquatic organisms.
Selenium
                                      24
Readily bioaccumulates; elevated concentrations have caused fish kills and numerous sublethal effects (e.g., increased metabolic rates, decreased growth rates, reproductive failure) to aquatic and terrestrial organisms. Short term exposure at high levels can cause damage to the peripheral nervous system. Long term exposure can result in damage to the kidney, liver, and nervous and circulatory systems.
Silver
                                       2
Two key enzymes of ion transport in the gills (Na+/K+-ATPase and carbonic anhydrase), and death results from ionoregulatory failure. Silver appears to be taken up by sodium and copper transport pathways in the gills, as well as by diffusion of neutral complexes. Silver accumulates preferentially in the liver, which serves as a scavenging organ. 
Zinc
                                       2
Biota with elevated levels have exhibited sublethal effects such as requiring more energy to support their metabolism and therefore exhibiting diminished growth, and abnormalities of the liver and kidneys; accumulates in the gills of fish and disrupts developmental and hematological functions
Note:
[a] See Kumari et al. (2016); Elbeshti et al. (2018); Gautam et al. (2014); Aslam and Yousaf (2017); Ip et. al (2001); Mager (2011); Pyle and Couture (2011); Wilson (2011); Wood (2011)

 References
Aslam, S., and A. M. Yousafzai. 2017. Chromium toxicity in fish: A review article. Journal of Entomology and Zoology Studies 5(3):1483 - 1488.
Elbeshti R.T., N.M. Elderwish, K.M. Abdelali, and Y. Tastan. 2018. Effects of heavy metals on fish. Menba Journal of Fisheries Faculty 4(1):36 - 47.
Gautam, R.K., K.S. Sanjay, M. Suresh, and C.C. Mahesh. 2014. Contamination of Heavy Metals in Aquatic Media: Transport, Toxicity and Technologies for Remediation. Chapter 1 in Heavy Metals In Water: Presence, Removal and Safety, pp. 1 - 24. doi:10.1039/9781782620174-00001.
Ip, Y.K., S.F. Chew, and D.J. Randall. 2001. Ammonia toxicity, tolerance, and excretion. Fish Physiology 20:109 - 148. 
Kumari, B., V. Kumar, A. Sinha, J. Ahsan, A. Ghosh, H. Wang, and G. De Boeck. 2016. Toxicology of arsenic in fish and aquatic systems. Environmental Chemistry Letters 14:1-22. doi:10.1007/s10311-016-0588-9.
Mager, E. 2011. Lead. Fish Physiology 31(B):185 - 236. 
Pyle, G., and P. Couture. 2011. Nickel. Fish Physiology 31(A):253 - 289.
Wilson, R. 2011. Aluminum. Fish Physiology 31(B):67 - 123.
Wood, C. 2011. Silver. Fish Physiology 31(B):1 - 65.