Final Fact Sheet – May 5, 2010 Final

R. Koch/Eastern Regional Office



### FACT SHEET FOR NPDES PERMIT WA-004496-2 CITY OF PASCO WASTEWATER TREATMENT WORKS

PURPOSE of this Fact Sheet

This fact sheet explains and documents the decision s Ecology made in drafting the proposed National Pollutant Discharge Elimination System (NP DES) Permit for the City of Pasco Treatment Works.

This fact sheet complies with Section 173-220-060 o f the Washington Administrative Code (WAC), which requires Ecology to prepare a draft pe rmit and accompanying fact sheet for public evaluation before issuing an NPDES permit.

Ecology makes the draft permit and fact sheet avail able for public review and comment at least 30 days before issuing the final permit. Copies of the fact sheet and draft permit for the City of Pasco Wastewater Treatment Works, NPDES Permit WA-0044962, are available for public review and comment from May 12, 2010 until June 11, 2010. For more details on preparing and filing comments about these documents, please see Appendix A - Public Involvement

. The City of Pasco’s wastewater utility staff reviewed the draft permit and fact sheet for factua l accuracy. Ecology corrected any errors or omission s regarding the facility’s location, history, discharges, or receiving water.

After the public comment period closes, Ecology wil l summarize substantive comments and provide responses to them. Ecology will include th e summary and responses to comments in this Fact Sheet as Appendix D - Response to Comments , and publish it when issuing the final NPDES permit. Ecology will not revise the rest of the fact sheet, but the full document will become part of the legal history contained in the f acility’s permit file.

SUMMARY

The City of Pasco Wastewater Treatment Works discha rges to the Columbia River. The treatment facilities generally produce an excellent quality effluent. Past exceptions were usually related to illegal discharges into the sewer collec tion system resulting in minor inhibitory or toxic impacts on the biological community in the aeration basin. The wastewater treatment plant staff has been optimizing solids handling to better mitig ate impacts from recycled solids. The facility has added a solids thickening drum and improvements to the digesters have been made. Changes in the proposed permit from the previous permit are primarily a compliance schedule requiring submission of an engineering report suitable for ap proval. The engineering report must evaluate the hydraulic and organic loading capacity of the C ity of Pasco’s wastewater facilities as they currently exist and if necessary recommend upgrades appropriate for the wastewater facilities to provide twenty years of additional service to the c ommunity.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Final R. Koch/Eastern Regional Office TABLE OF CONTENTS

I

. INTRODUCTION ......................................

................................................... ......................1

II. BACKGROUND INFORMATION ............................

................................................... .....2 A. Facility Description ..............................

................................................... .................3 History............................................

................................................... .......................3 Collection System Status ..........................

................................................... ............3 Treatment Processes................................

................................................... ..............3 Discharge Outfall .................................

................................................... .................4 Solid Wastes.......................................

................................................... ...................4 B. Permit Status .....................................

................................................... ....................5 C. Summary of Compliance with Previous Permit Issued . ..........................................5 D. Wastewater Characterization .......................

................................................... .........5 E. Description of the Receiving Water ................

................................................... ......5 F. SEPA Compliance ...................................

................................................... .............6

III. PROPOSED PERMIT Limits ............................

................................................... ...............7 G. Design Criteria ...................................

................................................... ...................7 H. Technology-Based Effluent Limits ..................

................................................... .....8 I. Surface Water Quality-Based Effluent Limits ....... ..................................................9 Numerical Criteria for the Protection of Aquatic Li fe and Recreation ....................9 Numerical Criteria for the Protection of Human Heal th ..........................................9 Narrative Criteria ................................

................................................... ................10 Antidegradation....................................

................................................... ...............10 Mixing Zones ......................................

................................................... ................11 J. Designated Uses and Surface Water Quality Criteria ............................................16 K. Evaluation of Surface Water Quality-Based Effluent Limits for Numeric Criteria ..........................................

................................................... ......................17 L. Whole Effluent Toxicity ...........................

................................................... ..........21 M. Human Health ......................................

................................................... ...............21 N. Sediment Quality ..................................

................................................... ..............22 O. Ground Water Quality Limits .......................

................................................... ......22 P. Comparison of Effluent Limits with the Previous Per mit Issued on July 7, 2004...............................................

................................................... ......................22

IV. MONITORING REQUIREMENTS ...........................

................................................... ....22 Q. Lab Accreditation..................................

................................................... ..............23

V. OTHER PERMIT CONDITIONS ...........................

................................................... .......24 R. Reporting and Record Keeping ......................

................................................... .....24 S. Prevention of Facility Overloading ................

................................................... .....24 T. Operation and Maintenance (O&M) ...................

................................................... 24 U. Pretreatment ......................................

................................................... ..................25 Duty to Enforce Discharge Prohibitions ............

................................................... .25 Federal and State Pretreatment Program Requirements ........................................25 Routine Identification and Reporting of Industrial Users ......................................26Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Final R. Koch/Eastern Regional Office

Requirements for Performing an Industrial User Surv ey ......................................26 V. Solid Waste Control ...............................

................................................... .............26 W. General Conditions ................................

................................................... .............26

VI. PERMIT ISSUANCE PROCEDURES ........................

................................................... ..27 X. Permit Modifications ..............................

................................................... ............27 Y. Proposed Permit Issuance ..........................

................................................... .........27

VII. REFERENCES FOR TEXT AND APPENDICES ................ ...........................................28

APPENDIX A—PUBLIC INVOLVEMENT INFORMATION ......... .........................................29

APPENDIX B—GLOSSARY ...............................

................................................... .....................30

APPENDIX C—TECHNICAL CALCULATIONS .................

................................................... ..34

APPENDIX D—RESPONSE TO COMMENTS ...................

................................................... ....35Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 1 R. Koch/Eastern Regional Office I

. INTRODUCTION The Federal Clean Water Act (FCWA, 1972, and later amendments in 1977, 1981, and 1987) established water quality goals for the navigable ( surface) waters of the United States. One mechanism for achieving the goals of the Clean Wate r Act is the National Pollutant Discharge Elimination System (NPDES), administered by the fed eral Environmental Protection Agency (EPA). The EPA authorized the State of Washington to manage the NPDES permit program in our state. Our state legislature accepted the dele gation and assigned the power and duty for conducting NPDES permitting and enforcement to Ecol ogy. The legislature defined Ecology's authority and obligations for the wastewater discha rge permit program in 90.48 RCW (Revised Code of Washington).

The following regulations apply to municipal NPDES permits:

• Procedures Ecology follows for issuing NPDES permit s (chapter 173-220 WAC)

• Technical criteria for discharges from municipal wa stewater treatment facilities (chapter 173-221 WAC)

• Water quality criteria for surface waters (chapter 173-201A WAC) and for ground waters (chapter 173-200 WAC)

• Sediment management standards (chapter 173-204 WAC)

• Submission of Plans and Reports for Construction of Wastewater Facilities (Chapter 173- 240 WAC)

These rules require any treatment facility operator to obtain an NPDES permit before discharging wastewater to state waters. They also help define the basis for limits on each discharge and for requirements imposed by the permi t.
Under the NPDES permit program and in response to a complete and accepted permit application, Ecology must prepare a draft permit an d accompanying fact sheet, and make them available for public review before final issuance. Ecology must also publish an announcement (public notice) telling people where they can read the draft permit, and where to send their comments, during a period of thirty days (WAC 173-2 20-050). (See Appendix A - Public Involvement

for more detail about the public notice and commen t procedures). After the public comment period ends, Ecology may make changes to th e draft NPDES permit. Ecology will summarize the responses to comments and any changes to the permit in Appendix D.

# Copyrighted page(s) removed. Copyrighted material is not available in Regulations.gov since it may not be reproduced without consent of the copyright holder.

Removed pages can be viewed at the USEPA Docket Center, Public Reading Room.

Address: 1301 Constitution Ave, NW Room 3334 Washington, DC 20004

Telephone: 202-566-1744

Email: docket-customerservice@epa.govFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 3 R. Koch/Eastern Regional Office A. Facility Description

The City of Pasco owns and operates an activated sl udge process domestic wastewater treatment plant designed to oxidize, nitrify and di sinfect wastewater with ultraviolet light radiation. Ecology provided financial assistance w ith the expectation that the treatment plant would remove ammonia and chlorine from the receivin g environment and eliminate noncompliance issues. The facility is classified as a n EPA major discharger and discharges to the Lake Wallula reach of the Columbia River.

History Pasco originally built the wastewater treatment pla nt in 1954 as a primary treatment facility. In 1970, it constructed a trickling filter so that the plant could meet secondary treatment requirements. The 1970 addition of a secondary tre atment process increased the plant's design population equivalent to 30,000. The most r ecent upgrade (1998) increased the design population equivalent to 43,500. During the last permit cycle, the City upgraded the solids handling facilities, digestion and solids th ickening. These improvements likely increased the overall treatment works capacity.

Collection System Status The City of Pasco submitted a Comprehensive Sewer P lan to Ecology in December 1992 and updated it in 1999. The City submitted a facility plan with supplements in 1993, which was approved in February 1994. The plan proposed impro vements to the City's collection system, wastewater treatment facility and pumping s tations. The City has replaced the pumping stations at the intersection of 9 th and Washington and at the intersection of 5 th and Ainsworth with a single pump station at 9 th and Washington resulting in the elimination of an overflow. It also replaced the old “Navy” pump sta tion in the industrial area east of the airport. Areas in West Pasco and East Pasco have b een added to the sewerage system. The Port of Pasco abandoned the wastewater stabilizatio n lagoons serving its facilities on Ainsworth and the City now serves the area by a tru nk sewer connected to its sewerage system. The City’s collection system consists of g ravity sewers from 8 inches to 36 inches in diameter, pump stations and pressure piping.

Treatment Processes The current wastewater treatment facility includes:

• A headworks building with grit removal.

• Screening equipment and inlet piping.

• An operations building and laboratory.

• A renovated primary clarifier and trickling filter (new distributor).

• Secondary process elements designed to provide nitr ification - aeration basins.

• Secondary clarifiers with lime addition for alkali nity and pH control.

• Ultraviolet disinfection.

• Anaerobic digesters.

• Renovated and expanded sludge digestion processes w ith the addition of a solids drum thickener and a sludge drying bed.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 4 R. Koch/Eastern Regional Office The City’s rate of growth is reflected in the incre ase in flows. The wastewater treatment works design is based on the presumed need to nitri fy and avoid toxic effects from ammonia in the Columbia River. At the time the City’s outf all was an end of pipe in the river. While the wastewater treatment plant was built to nitrify , consideration was also given to extend the outfall further into the river and add a multi- port diffuser. The installation of the outfall negated the need to nitrify in terms of water quali ty based effluent limitations. In August 2005, the City commissioned an engineering evaluat ion of the wastewater treatment facilities capacity. Until recently, the wastewate r treatment works was being operated in a nitrifying mode in order to minimize the generation of biosolids.

The treatment facilities generally produce an excel lent quality effluent. Past exceptions were usually related to illegal discharges into the sewe r collection system resulting in minor inhibitory or toxic impacts on the biological commu nity in the aeration basin. Some violations were related to how recycle of solids wa s handled. The wastewater treatment plant staff has been optimizing solids handling to better mitigate impacts from recycled solids. The facility has added a solids thickening drum and improvements to the digesters have been made. The 2005 assessment of the wastewater treatm ent facilities capacity pointed that solids handling was a critical capacity limiting fa ctor. With the new digester it is time to reassess the capacity of the facility and its abili ty to serve the community.

The WWTP is an activated sludge treatment plant wit h a flow between 1 MGD and 10 MGD. As such, it is a class III facility according to

1 WAC 173-230-140; Classification of Wastewater Treatment Plants

. Discharge Outfall The effluent is discharged from the facility via a 24-inch steel multiport diffuser outfall into the Columbia River. The outfall has three 8” diame ter diffuser ports. At this location the river flows west to east south east. Leaving the p lant site, the outfall follows a southerly line defined by Gray Street continuing approximately 900 feet offshore from the north bank and at a depth of approximately 30 feet.

Solid Wastes The treatment facilities remove solids during the t reatment of the wastewater at the headworks (grit and screenings), and at the primary and secondary clarifiers (biosolids). In addition to incidental solids (rags, scum, and othe r debris) removed as part of the routine maintenance of the equipment, Scum is routed to the anaerobic digester for biological oxidation.

Biosolids removed from the clarifiers are thickened (dissolved air floatation), anaerobically digested, dried in the drying beds and land applied under a permit issued by Ecology’s Waste 2 Resources Program. The biosolids produced at the treatment works are of exceptional quality and beneficial use options are available. Grit, rags, and screenings are drained and disposed of as solid waste at the local landfill. The proposed permit includes a condition requiring the City to properly handle residual soli ds so that no leachate enters ground or surface water.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 5 R. Koch/Eastern Regional Office B. Permit Status

Ecology issued the previous permit for this facilit y on July 7, 2004. The previous permit placed effluent limitations on 5-day Biochemical Ox ygen Demand (BOD 5 ), Total Suspended Solids (TSS), pH, and Fecal Coliform Bacteria.
The City of Pasco submitted an application for perm it renewal on January 5, 2009. Ecology accepted it as complete on January 30, 2009.

C. Summary of Compliance with Previous Permit Issued

Ecology staff last conducted a non-sampling complia nce inspection on June 12, 2008. The City of Pasco WWTP has complied with the effluent l imits and permit conditions throughout the duration of the permit issued on Jul y 7, 2004

. Ecology assessed compliance based on its review of the facility’s discharge mon itoring reports (DMRs) and on inspections conducted by Ecology.

D. Wastewater Characterization
The concentration of pollutants in the discharge wa s reported in the NPDES application and in discharge monitoring reports (DMRs). The tabula ted data represents the quality of the effluent discharged from the Pasco WWTP using DMR d ata from January 2005 through March 2009. The effluent is characterized as follo ws:

Table 2: Wastewater Characterization

Parameter Average

Concentration Maximum

Concentration Minimum

Concentration

Flow, MGD 3.23 3.62 3.01 Influent BOD 5

, mg/L 237.3 313 191 Influent TSS, mg/L 246 327 203 Effluent BOD 5

, mg/L 12.5 57 4 Effluent TSS, mg/L 15.7 100 6 Effluent NH 3

, mg/L 13.6 35.1 0.41 Effluent Temperature, January, deg F 59 60 58

Effluent Temperature, August, deg F 78 79 77

E. Description of the Receiving Water
The City of Pasco WWTP discharges to the Columbia R iver. Other nearby point source outfalls include the City of Kennewick WWTP and the City of Richland WWTP.
The ambient background data used for this permit in cludes the following from environmental Assessment Program monitoring station 36A070 on the Columbia River near Vernita:Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 6 R. Koch/Eastern Regional Office Table 3: Ambient Background Data

Parameter Value used Temperature (highest annual 1-DADMax) 21 o C Temperature (**some waterbodies have specific temperature criteria as assigned in Table 602) See Footnote 1

pH (Maximum / Minimum) 8.45/8.03 Dissolved Oxygen (Maximum / Minimum) 14.08/9.38 mg/ L
Total Ammonia-N 0.01 mg/L Fecal Coliform (Maximum) 11/100 mL Turbidity 1.2 NTU
Hardness 65 mg/L as CaCO3
Lead 0.1 μg/L Copper 0.67 μg/L
Zinc 5 μg/L

Footnote:

1. From Washington-Oregon border (river mile 309.3) to Priest Rapids Dam (river mile 397.1). Temperature shall not exceed a 1-DMax of 2 0.0°C due to human activities. When natural conditions exceed a 1-DMax of 20.0°C, no temperature increase will be allowed which will raise the receiving water temper ature by greater than 0.3°C; nor shall such temperature increases, at any time, exceed t = 34/(T + 9)

F. SEPA Compliance
Regulation exempts reissuance or modification of an y wastewater discharge permit from the SEPA process as long as the permit contains conditi ons that are no less stringent than state rules and regulations. The exemption applies only to existing discharges, not to new discharges. The City prepared SEPA and State Environmental Revi ew Process (SERP) documents during the planning phase of the wastewater treatme nt works upgrade completed in July 1998. The City prepared SERP documents to comply w ith Washington Water Pollution Control Revolving Fund requirements.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 7 R. Koch/Eastern Regional Office 

### III. PROPOSED PERMIT LIMITS
Federal and state regulations require that effluent limits in an NPDES permit must be either technology- or water quality-based.

• Technology-based limits are based upon the treatmen t methods available to treat specific pollutants. Technology-based limits are set by the EPA and published as a regulation, or Ecology develops the limit on a case-by-case basis (40 CFR 125.3, and chapter 173-220 WAC).

• Water quality-based limits are calculated so that t he effluent will comply with the Surface Water Quality Standards (chapter 173-201A WAC), Gro und Water Standards (chapter 173- 200 WAC), Sediment Quality Standards (chapter 173-2 04 WAC) or the National Toxics Rule (40 CFR 131.36).

• Ecology must apply the most stringent of these limi ts to each parameter of concern. These limits are described below.
The limits in this permit reflect information recei ved in the application and from supporting reports (engineering, hydrogeology, etc.). Ecology evaluated the permit application and determined the limits needed to comply with the rul es adopted by the state of Washington. Ecology does not develop effluent limits for all re ported pollutants

. Some pollutants are not treatable at the concentrations reported, are not c ontrollable at the source, are not listed in regulation, and do not have a reasonable potential to cause a water quality violation.
Nor does Ecology usually develop limits for polluta nts that were not reported in the permit application but that may be present in the discharg e. The permit does not authorize discharge of the non-reported pollutants. If significant change s occur in any constituent of the effluent discharge, the City of Pasco is required to notify Ecology (40 CFR 122.42(a)). The City of Pasco may be in violation of the permit until Ecolo gy modifies the permit to reflect additional discharge of pollutants.

G. Design Criteria

In accordance with WAC 173-220-150 (1)(g), flows or waste loadings must not exceed approved design criteria. However Ecology-is requiring an u pdate of the design criteria to reflect recent upgrades of the solids handling treatment train whi ch limiting hydraulic capacity and organic loading capacity.

Table 4: Design Criteria for the City of Pasco WWT P

Influent Loadings in the Design Criteria Year Population To be determined (TBD) Average Annual Flow (MGD) TBD Maximum Month Flow (MGD) TBDFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 8 R. Koch/Eastern Regional Office Influent Loadings in the Design Criteria Year Maximum Day Flow (MGD) TBD
Maximum Hour Flow (MGD) TBD
BOD 5 Loading– Average Annual (lbs/day) TBD
BOD 5 Loading – Maximum Month (lbs/day) TBD TSS Loading – Average Annual (lbs/day) TBD TSS Loading– Maximum Month (lbs/day) TBD Ammonia Loading – Average Annual (lbs/day) TBD

Ammonia Loading – Maximum Month (1,000 lbs/day) TBD

H. Technology-Based Effluent Limits
Federal and state regulations define technology-bas ed effluent limits for municipal wastewater treatment plants. These effluent limits are given in 40 CFR Part 133 (federal) and in chapter 173-221 WAC (state). These regulati ons are performance standards that constitute all known, available, and reasonable met hods of prevention, control, and treatment (AKART) for municipal wastewater.
Chapter 173-221 WAC lists the following technology- based limits for pH, fecal coliform, BOD 5 , and TSS:

Table 5: Technology-based Limits

Parameter Limit pH The pH must measure within the range of 6.0 to 9 .0 standard units.

Fecal Coliform Bacteria Monthly Geometric Mean = 200 organisms/100 mL Weekly Geometric Mean = 400 organisms/100 mL

BOD 5 (concentration) Average Monthly Limit is the most stringent of the following: - 30 mg/L - may not exceed fifteen percent (15%) of the aver age influent concentration Average Weekly Limit = 45 mg/L

TSS (concentration) Average Monthly Limit is the most stringent of the following: - 30 mg/L - may not exceed fifteen percent (15%) of the ave rage influent concentration Average Weekly Limit = 45 mg/LFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 9 R. Koch/Eastern Regional Office The technology-based mass limits are based on WAC 1 73-220-130(3)(b) and 173-221-030(11)(b). From the previous permit the effluent mass was as follows and will be used temporarily until the required engineering rep ort is approved.
The maximum month effluent mass (lbs/day) was calcu lated as the maximum monthly design flow (4.52 MGD) x Concentration limit (30 mg/L) x 8 .34 (conversion factor) = mass limitation of 1131 lb./day of BOD 5 or TSS.
Monthly effluent mass loadings (lbs/day) = maximum monthly influent design loading (10,690 lbs./day) x 0.15 = 1603.5 lbs./day, BOD5 o r . (8,720 lbs./day) x 0.15 = 1308 lbs./day TSS
The weekly average effluent mass loading = 1.5 x mo nthly loading. 1.5 x 1603.5 lbs./day =2405 lbs/day BOD5 or 1.5 x 1308 lbs/day = 1962 lbs/day TSS

The calculation of mass based on flow x concentrati on x conversion faction above generates the more restrictive effluent mass limit.

I. Surface Water Quality-Based Effluent Limits
The Washington State Surface Water Quality Standard s (chapter 173-201A WAC) are designed to protect existing water quality and pres erve the beneficial uses of Washington's surface waters. Waste discharge permits must inclu de conditions that ensure the discharge will meet the surface water quality standards (WAC 173-201A-510). Water quality-based effluent limits may be based on an individual waste load allocation or on a waste load allocation developed during a basin wide total maxi mum daily load study (TMDL).

Numerical Criteria for the Protection of Aquatic Li fe and Recreation Numerical water quality criteria are listed in the water quality standards for surface waters (chapter 173-201A WAC). They specify the maximum l evels of pollutants allowed in receiving water to protect aquatic life and recreat ion in and on the water. Ecology uses numerical criteria along with chemical and physical data for the wastewater and receiving water to derive the effluent limits in the discharg e permit. When surface water quality based limits are more stringent or potentially more strin gent than technology based limits, the discharge must meet the water quality based limits.

Numerical Criteria for the Protection of Human Heal th
The U.S. EPA has published 91 numeric water quality criteria for the protection of human health that are applicable to dischargers in Washin gton State (EPA 1992). These criteria are designed to protect humans from exposure to polluta nts linked to cancer and other disease, based on consuming fish and shellfish and drinking contaminated surface waters. The water quality standards also include radionuclide criteri a to protect humans from the effects of radioactive substances.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 10 R. Koch/Eastern Regional Office Narrative Criteria
Narrative water quality criteria (e.g., WAC 173-201 A-240(1); 2006) limit the toxic, radioactive, or other deleterious material concentr ations that the facility may discharge to levels below those which have the potential to:

• Adversely affect designated water uses.

• Cause acute or chronic toxicity to biota.

• Impair aesthetic values.

• Adversely affect human health.
Narrative criteria protect the specific designated uses of all fresh waters (WAC 173-201A200, 2006) and of all marine waters (WAC 173-201A-2 10,; 2006) in the State of Washington.

Antidegradation The purpose of Washington's Antidegradation Policy (WAC 173-201A-300-330; 2006) is
to:

• Restore and maintain the highest possible quality o f the surface waters of Washington.

• Describe situations under which water quality may b e lowered from its current condition.

• Apply to human activities that are likely to have a n impact on the water quality of surface water.

• Ensure that all human activities likely to contribu te to a lowering of water quality, at a minimum, apply all known, available, and reaso nable methods of prevention, control, and treatment (AKART).

• Apply three tiers of protection (described below) f or surface waters of the state.

Tier I ensures existing and designated uses are mai ntained and protected and applies to all waters and all sources of pollutions. Tier II ensures tha t waters of a higher quality than the criteria assigned are not degraded unless such lowering of w ater quality is necessary and in the overriding public interest. Tier II applies only t o a specific list of polluting activities. Tier II I prevents the degradation of waters formally listed as "outstanding resource waters," and applies to all sources of pollution.

A facility must prepare a Tier II analysis when all three of the following conditions are met:

• The facility is planning a new or expanded action.

• Ecology regulates or authorizes the action.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 11 R. Koch/Eastern Regional Office • The action has the potential to cause measurable de gradation to existing water quality at the edge of a chronic mixing zone.

This facility must meet Tier I requirements.

• Dischargers must maintain and protect existing and designated uses. Ecology must not allow any degradation that will interfere with, or become injurious to, existing or designated uses, except as provided for in chapter 173-201A WAC.

• The facility must include a Tier II analysis in the engineering report demonstrating that accommodating an additional 20 years of capacity wi ll not cause measurable degradation to existing water quality at the edge o f a chronic mixing zone.

Mixing Zones
A mixing zone is the defined area in the receiving water surrounding the discharge port(s), where wastewater mixes with receiving water. Withi n mixing zones the pollutant concentrations may exceed water quality numeric sta ndards, so long as the discharge does not interfere with designated uses of the receiving water body (for example, recreation, water supply, and aquatic life and wildlife habitat , etc.) The pollutant concentrations outside of the mixing zones must meet water quality numeric standards. State and federal rules allow mixing zones because the concentrations and effects of most pollutants diminish rapidly after discharge, due to dilution. Ecology defines mixing zone sizes to limit the amount of time any exposure to t he end-of-pipe discharge could harm water quality, plants, or fish.
The state’s water quality standards allow Ecology t o authorize mixing zones for the facility’s permitted wastewater discharges only if those discharges already receive all known, available, and reasonable methods of prevent ion, control, and treatment (AKART). Mixing zones typically require compliance with wate r quality criteria within a specified distance from the point of discharge and use no mor e than 25% of the available width of the water body for dilution. Ecology uses modeling to estimate the amount of mixing within the mixing zone. Through modeling, Ecology determines the potential for violating the water quality standards at the edge of the mixing zone an d derive any necessary effluent limits. Steady state models are the most frequently used to ols for conducting mixing zone analyses. Ecology chooses values for each effluent and for re ceiving water variables that correspond to the time period when the most critical condition is likely to occur (see Ecology’s Permit Writer’s Manual ). Each critical condition parameter, by itself, h as a low probability of occurrence and the resulting dilution factor is con servative. The term “reasonable worst-case” applies to these values.
The mixing zone analysis produces a numerical value called a dilution factor (DF). A dilution factor represents the amount of mixing of effluent and receiving water that occurs at the boundary of the mixing zone. For example, a di lution factor of 10 means the effluent is 10% and the receiving water is 90% of the total vol ume of water at the boundary of the mixing zone. Ecology uses dilution factors with th e water quality criteria to calculate reasonable potentials and effluent limits.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 12 R. Koch/Eastern Regional Office Water quality standards include both aquatic life-b ased criteria and human health-based criteria. The former are applied at both the acute and chronic mixing zone boundaries; the latter are applied only at the chronic boundary. T he concentration of pollutants at the boundaries of any of these mixing zones may not exc eed the numerical criteria for that zone.
Each aquatic life acute criterion is based on the assumption that organism s are not exposed to that concentration for more than one hour and mo re often than one exposure in three
years. Each aquatic life chronic criterion is based on the assumption that organism s are not exposed to that concentration for more than four co nsecutive days and more often than once in three years.
The two types of human health-based water quality c riteria distinguish between those pollutants linked to non-cancer effects (non-carcin ogenic) and those linked to cancer effects (carcinogenic). The human health-based water quali ty criteria incorporate several exposure and risk assumptions. These assumptions include:

• A 70-year lifetime of daily exposures.

• An ingestion rate for fish or shellfish measured in kg/day.

• An ingestion rate of two liters/day for drinking wa ter

• A one-in-one-million cancer risk for carcinogenic c hemicals. This permit authorizes a small acute mixing zone, s urrounded by a chronic mixing zone around the point of discharge (WAC 173-201A-400). The water quality standards impose certain conditions before allowing the discharger a mixing zone:
1. Ecology must specify both the allowed size and l ocation in a permit.

The mixing zones will accommodate the geometric con figuration and flow restriction for mixing zones in Chapter 173-201A WAC and are define d as follows:

The chronic mixing zone shall extend no more than 3 30 feet downstream from the point of discharge and the acute mixing zone shall extend no more than 33 feet downstream.

Ecology used the mixing zone dilution using as-buil t record drawing information for the new outfall, the defined mixing zone geometry and t he CORMIX model to verify that the outfall provides adequate dilution to ensure that t he discharge meets water quality standards. Ecology determined the following dilution factors u sing CORMIX in preparation for issuing the 1999 NPDES permit.

Temperature scenario Acute mixing zone dilution Ch ronic mixing zone dilution Summer 1:150 1:182 effluent:river Winter 1:139 1:173 effluent:riverFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 13 R. Koch/Eastern Regional Office Ecology used the following critical conditions to m odel the discharge:

• The seven-day-average low river flow with a recurre nce interval of ten years (7Q10); was 38,000 cfs when the outfall was designe d and modeled.

Parameter Value Value Velocity 0.17 m/s 0.17 m/s Depth 9.1 m 9.1 m Width 915 m 915 m Roughness (Manning) 0.025 0.025 Temperature 4 C 21 C Copper (August 2002 result) 35 ug/L in effluent 35 ug/L in effluent

Before reissuing the NPDES permit in 2004 Ecology r echecked dilution using Visual Plumes and modeled the discharge from each diffuser ports separately. The plumes are separate and distinct within the allowed mixing zon e, particularly in winter. In summer, when the effluent is slightly more buoyant than the receiving water, the plumes begin to merge at the edge of the chronic mixing zone. Howe ver, the dilution at the edge of the chronic mixing zone as calculated by Visual Plumes is 649.8. Using Visual Plumes the dilution at the edge of the acute mixing zone is 27 .9.

No changes have occurred generating new input param eters. Therefore, Ecology has used the mixing analysis completed for the 2004 permit f or this proposed permit.

2. The facility must fully apply “all known, availa ble, and reasonable methods of prevention, control and treatment” (AKART) to its d ischarge.
Ecology has determined that the treatment provided at the Pasco WWTP meets the requirements of AKART (see “Technology based Limits ”).

3. Ecology must consider critical discharge conditi ons.
Surface water quality-based limits are derived for the waterbody’s critical condition (the receiving water and waste discharge condition with the highest potential for adverse impact on the aquatic biota, human health, and existing or designated waterbody uses). The critical discharge condition is often pollutant-specific or waterbody-specific.

Critical discharge conditions are those conditions that result in reduced dilution or increased effect of the pollutant. Factors affecti ng dilution include the depth of water, the density stratification in the water column, the currents, and the rate of discharge. Density stratification is determined by the salinit y and temperature of the receiving water. Temperatures are warmer in the surface wate rs in summer. Therefore, density stratification is generally greatest during the sum mer months. Density stratification affects how far up in the water column a freshwater plume may rise.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 14 R. Koch/Eastern Regional Office The rate of mixing is greatest when an effluent is rising. The effluent stops rising when the mixed effluent is the same density as the surro unding water. After the effluent stops rising, the rate of mixing is much more gradu al. Water depth can affect dilution when a plume might rise to the surface when there i s little or no stratification. Ecology’s Permit Writer’s Manual describes additional guidance on criteria/design conditions for determining dilution factors. The m anual can be obtained from Ecology’s website at http://www.ecy.wa.gov/biblio/92109.html

. 4. Supporting information must clearly indicate the mixing zone would not:

• Have a reasonable potential to cause the loss of se nsitive or important habitat.

• Substantially interfere with the existing or charac teristic uses.

• Result in damage to the ecosystem.

• Adversely affect public health.

Ecology established Washington State water quality criteria for toxic chemicals using EPA criteria. EPA developed the criteria using tox icity tests with numerous organisms and set the criteria to generally protect the speci es tested and to fully protect all commercially and recreationally important species.

EPA sets acute criteria for toxic chemicals assumin g organisms are exposed to the pollutant at the criteria concentration for one hou r. They set chronic standards assuming organisms are exposed to the pollutant at the crite ria concentration for four days. Dilution modeling under critical conditions general ly shows that both acute and chronic criteria concentrations are reached within minutes of being discharged.
The discharge plume does not impact drifting and no n-strong swimming organisms because they cannot stay in the plume close to the outfall long enough to be affected. Strong swimming fish could maintain a position with in the plume, but they can also avoid the discharge by swimming away. Mixing zones generally do not affect benthic organisms (bottom dwellers) because the buoyant plu me rises in the water column. Ecology has additionally determined that the efflue nt will not exceed 33 degrees C for more than two seconds after discharge; and that the temperature of the water will not create lethal conditions or blockages to fish migra tion.

Ecology evaluates the cumulative toxicity of an eff luent by testing the discharge with whole effluent toxicity (WET) testing.

Ecology reviewed the above information, the specifi c information on the characteristics of the discharge, the receiving water characteristi cs and the discharge location. Based on this review, Ecology concluded that the discharg e does not have a reasonable potential to cause the loss of sensitive or importa nt habitat, substantially interfere with existing or characteristics uses, result in damage to the ecosystem, or adversely affect public health if the permit limits are met.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 15 R. Koch/Eastern Regional Office 5. The discharge/receiving water mixture must not e xceed water quality criteria outside the boundary of a mixing zone.
Ecology conducted a reasonable potential analysis u sing procedures established by the EPA and by Ecology for each pollutant and concluded that the discharge/receiving water mixture will not violate water quality criter ia outside the boundary of the mixing zone if permit limits are met.

6. The size of the mixing zone and the concentratio ns of the pollutants must be minimized.
At any given time, the effluent plume uses only a p ortion of the acute and chronic mixing zone, which minimizes the volume of water in volved in mixing. The plume may rise through the water column as it mixes depen ding on the temperature, therefore much of the receiving water volume at lower depths in the mixing zone may not be mixed with discharge. Similarly, because the disch arge may stop rising at some depth due to density stratification, waters above that de pth will not mix with the discharge. Ecology determined it is impractical to specify in the permit the actual, much more limited volume in which the dilution occurs as the plume rises and moves with the
current.
Ecology minimizes the size of mixing zones by requi ring dischargers to install diffusers when they are appropriate to the discharge and the specific receiving waterbody. Pasco has a multi-port diffuser, 3 ports. When a diffuse r is installed, the discharge is more completely mixed with the receiving water in a shor ter time. Ecology also minimizes the size of the mixing zone (in the form of the dilution factor) using design criteria with a low probability of occ urrence. For example, Ecology uses the expected 95 th percentile pollutant concentration, the 90 th percentile background concentration, the centerline dilution factor, and the lowest flow occurring once in every ten years to perform the reasonable potential analysis.
Because of the above reasons, Ecology has effective ly minimized the size of the mixing zone authorized in the proposed permit.

7. Maximum size of mixing zone.
The authorized mixing zone does not exceed the max imum size restriction.

8. Acute mixing zone.

• The discharge/receiving water mixture must comply w ith acute criteria as near to the point of discharge as practicably attai nable. Ecology determined that the acute criteria will be met at 10% of the distance or of the chronic mixing zone at the ten year low flow.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 16 R. Koch/Eastern Regional Office • The pollutant concentration, duration, and frequenc y of exposure to the discharge will not create a barrier to migration or translocation of indigenous organisms to a degree that has the potential to cau se damage to the ecosystem. As described above, the toxicity of any pollutant d epends upon the exposure, the pollutant concentration, and the time the organism is exposed to that concentration. Authorizing a limited acute mixing zone for this di scharge assures that it will not create a barrier to migration. The effluent from t his discharge will rise as it enters the receiving water, assuring that the rising efflu ent will not cause translocation of indigenous organisms near the point of discharge (b elow the rising effluent).

• Comply with size restrictions. The mixing zone authorized for this discharge compl ies with the size restrictions published in chapter 173-201A WAC. 9. Overlap of Mixing Zones.

This mixing zone does not overlap another mixing zo ne.

J. Designated Uses and Surface Water Quality Criteria
Applicable designated uses and surface water qualit y criteria are defined in chapter 173-201A WAC. In addition, the U.S. EPA set human health criteria for toxic pollutants (EPA 1992). Criteria applicable to this facility’s discharge are summarized below in Table 6.

• Aquatic Life Uses are designated based on the prese nce of, or the intent to provide protection for, the key uses. All indigenous fish and non-fish aquatic species must be protected in waters of the state in addition to the key species. The Aquatic Life Uses for this receiving water are identified below. Table 6: Aquatic Life Uses & Associated Criteria Salmonid Rearing and Migration Only Temperature Criteria – Highest 7DAD MAX From the Washington-Oregon border (river mile 309.3) to Priest Rapids Dam (river mile 397.1) temperature shall not exceed a 1- DMax of 20.0°C due to human activities. When natural conditions exceed a 1-DMax of 20.0°C, no temperature increase will be allowed which will raise the receiving water temperature by greater than 0.3°C; nor shall such temperature increases, at any time, exceed t = 34/(T + 9). Dissolved Oxygen Criteria – Lowest 1-Day Minimum 6.5 mg/L

Turbidity Criteria • 10 NTU over background when th e background is 50 NTU or less; or • A 20 percent increase in turbidity when theFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 17 R. Koch/Eastern Regional Office background turbidity is more than 50 NTU Total Dissolved Gas Criteria Total dissolved gas sh all not exceed 110 percent of saturation at any point of sample collection pH Criteria pH shall be within the range of 6.5 to 8.5 with a human-caused variation within the above range of less than 0.5 units

• The recreational uses are extraordinary primary con tact recreation, primary contact recreation, and secondary contact recreation. The recreational uses for this receiving water are identified below.

Table 7: Recreational Uses and Associated Criteria

Recreational Use Criteria Primary Contact Recreation Fecal coliform organism levels must not exceed a ge ometric mean value

of 100 colonies/100 mL, with not more than 10 perce nt of all samples (or any single sample when less than ten sample points exist) obtained for calculating the geometric mean value exceeding 200 colonies/100 mL

• The water supply uses are domestic, agricultural, industrial, and stock watering.

• The miscellaneous freshwater use s are wildlife habitat, harvesting, commerce and navigation, boating, and aesthetics.

K. Evaluation of Surface Water Quality-Based Effluent Limits for Numeric Criteria
Pollutants in an effluent may affect the aquatic en vironment near the point of discharge (near-field) or at a considerable distance from the point of discharge (far-field). Toxic pollutants, for example, are near-field pollutants— their adverse effects diminish rapidly with mixing in the receiving water. Conversely, a pollutant such as biological oxygen demand (BOD) is a far-field pollutant whose adverse effect occurs away from the discharge even after dilution has occurred. Thus, the method of calculating surface water quality-based effluent limits varies with the point at which the pollutant has its maximum effect.
With technology-based controls (AKART), predicted p ollutant concentrations in the discharge exceed water quality criteria. Ecology t herefore authorizes a mixing zone in accordance with the geometric configuration, flow r estriction, and other restrictions imposed on mixing zones by chapter 173-201A WAC.
Chronic Mixing Zone
WAC 173-201A-400(7)(a) specifies that mixing zones must not extend in a downstream direction from the discharge ports for a distance g reater than 300 feet plus the depth of water over the discharge ports or extend upstream for a d istance of over 100 feet, not utilize greater than 25% of the flow, and not occupy greater than 25% of the width of the water body.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 18 R. Koch/Eastern Regional Office The maximum boundaries of the mixing zones are defi ned as follows: The chronic mixing zone shall extend no more than 330 feet downstream from the point of discharge. The acute mixing zone shall extend no more than 33 feet downs tream of the point of discharge.
Acute Mixing Zone
WAC 173-201A-400(8)(a) specifies that in rivers and streams a zone where acute toxics criteria may be exceeded must not extend beyond 10% of the distance towards the upstream and downstream boundaries of the chronic zone, not use greater than 2.5% of the flow and not occupy greater than 25% of the width of the water body.
Ecology determined the dilution factors that occur within these zones at the critical condition using the reasonable potential spreadshee t. The dilution factors are listed in Table 7. The dilution factors below use a 7Q10 from the most recent recorded data from USGS; the current 7Q10 flow is 61,200 cfs.

Table 8: Dilution Factors (DF)

Criteria Acute Chronic Aquatic Life 1:181 1:2198 Human Health, Carcinogen 1:8477 Human Health, Non-carcinogen 1:3077

Ecology determined the impacts of temperature, pH, ammonia, and copper as described below, using the dilution factors in the above tabl e. The derivation of surface water qualitybased limits also takes into account the variabilit y of pollutant concentrations in both the effluent and the receiving water.

BOD 5 --With technology-based limits, this discharge resu lts in a small amount of BOD loading relative to the large amount of dilution in the receiving water at critical conditions. Technology-based limits will ensure that dissolved oxygen criteria are met in the receiving
water.
Temperature --The state temperature standards (WAC 173-201A-200 -210 and 600-612) include multiple elements:

• Annual summer maximum threshold criteria (June 15 t o September 15)

• Supplemental spawning and rearing season criteria ( September 15 to June 15)

• Incremental warming restrictions

• Protections against acute effects

Ecology evaluates each criterion independently to d etermine reasonable potential and derive permit limits.

• Annual summer maximum and supplementary spawning/re aring criteriaFact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 19 R. Koch/Eastern Regional Office

Each water body has an annual maximum temperature c riterion [WAC 173-201A200(1)(c), 210(1)(c), and Table 602]. These thresh old criteria (e.g., 12, 16, 17.5, 20°C) protect specific categories of aquatic life b y controlling the effect of human actions on summer temperatures.

Some waters have an additional threshold criterion to protect the spawning and incubation of salmonids (9°C for char and 13°C for salmon and trout) [WAC 173- 201A-602, Table 602]. These criteria apply during specific date-windows.
The threshold criteria apply at the edge of the chr onic mixing zone. Criteria for most fresh waters are expressed as the highest 7-Da y average of daily maximum temperature (7-DADMax).
The 7-DADMax temperature is the arithmetic average of seven consecutive measures of daily maximum temperatures. Criteria f or marine waters and some fresh waters are expressed as the highest 1-Day ann ual maximum temperature (1- DMax).

• Incremental warming criteria
The water quality standards limit the amount of war ming human sources can cause under specific situations [WAC 173-201A-200(1)(c)(i )-(ii), 210(1)(c)(i)-(ii)]. The incremental warming criteria apply at the edge of t he chronic mixing zone.
At locations and times when background temperatures are cooler than the assigned threshold criterion, point sources are permitted to warm the water by only a defined increment.
These increments are permitted only to the extent d oing so does not cause temperatures to exceed either the annual maximum or supplemental spawning criteria.

At locations and times when a threshold criterion i s being exceeded due to natural conditions , all human sources, considered cumulatively, must not warm the water more than 0.3°C above the naturally warm condition.
When Ecology has not yet completed a TMDL, our poli cy allows each point source to warm water at the edge of the chronic mixing zon e by 0.3°C. This is true regardless of the background temperature and even i f doing so would cause the temperature at the edge of a standard mixing zone t o exceed the numeric threshold criteria. Allowing a 0.3°C warming for each point source is reasonable and protective where the dilution factor is based on 25 % or less of the critical flow. This is because the fully mixed effect on temperatu re will only be a fraction of the 0.3°C cumulative allowance (0.075°C or less) for al l human sources combined.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 20 R. Koch/Eastern Regional Office • Temperature Acute Effects
Instantaneous lethality to passing fish: The upper 99th percentile daily maximum effluent temperature must not exceed 33°C; unless a dilution analysis indicates ambient temperatures will not exceed 33°C 2-seconds after discharge.
General lethality and migration blockage: Measurable (0.3°C) increases in temperature at the edge of a chronic mixing zone ar e not allowed when the receiving water temperature exceeds either a 1DMax of 23°C or a 7DADMax of 22°C.
Lethality to incubating fish: Human actions must not cause a measurable (0.3°C) warming above 17.5°C at locations where eggs are in cubating.
Annual summer maximum, supplementary spawning crite rion, and incremental warming criteria: Ecology calculated the reasonable potential for t he discharge to exceed the annual summer maximum, the supplementary spawni ng criterion, and the incremental warming criteria at the edge of the chronic mixing zone during critical condition(s). Reasonable potential for temperature was checked fo r early summer when a higher difference between effluent temperature and river t emperature was noted. The incremental increase was marginally greater in June and both Ju ne and August (critical condition) had incremental increase much less than the criteria. The incremental increase (0.04 C) for this discharge is within the allowable amount. Therefor e, the proposed permit does not include a temperature limit.
The proposed permit will require monitoring of effl uent and influent temperatures. USGS data supplies the ambient temperature.

pH --Ecology predicts no violation of the pH criteria under critical conditions. Therefore, the proposed permit includes technology-based efflu ent limits for pH.

Fecal Coliform --Under critical conditions, modeling predicts no v iolation of the water quality criterion for fecal coliform. Therefore, the propo sed permit includes the technology-based effluent limit for fecal coliform bacteria.

Toxic Pollutants --Federal regulations (40 CFR 122.44) require Ecolo gy to place limits in NPDES permits on toxic chemicals in an effluent whe never there is a reasonable potential for those chemicals to exceed the surface water qua lity criteria. Ecology does not exempt facilities with technology-based effluent limits fr om meeting the surface water quality standards.
The following toxic pollutants are present in the d ischarge: ammonia, and heavy metals.
Valid ambient background data was available for amm onia and copper. Ecology used all applicable data to evaluate reasonable potential fo r this discharge to cause a violation of water quality standards.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 21 R. Koch/Eastern Regional Office Ecology determined that ammonia and copper pose no reasonable potential to exceed the water quality criteria at the critical condition us ing procedures given in EPA, 1991 and as described above. Ecology’s determination assumes t hat this facility meets the other effluent limits of this permit.

L. Whole Effluent Toxicity
The water quality standards for surface waters forb id discharge of effluent that causes toxic effects in the receiving waters. Many toxic pollut ants cannot be measured by commonly available detection methods. However, laboratory t ests can measure toxicity directly by exposing living organisms to the wastewater and mea suring their responses. These tests measure the aggregate toxicity of the whole effluen t, so this approach is called whole effluent toxicity (WET) testing. Some WET tests me asure acute toxicity and other WET tests measure chronic toxicity.
WET testing conducted during effluent characterizat ion showed no reasonable potential for effluent discharges to cause receiving water acute toxicity. The proposed permit will not impose an acute WET limit.
If this facility makes process or material changes which, in Ecology's opinion, increase the potential for effluent toxicity, then Ecology may ( in a regulatory order, by permit modification, or in the permit renewal) require the facility to conduct additional effluent characterization.
WET testing conducted during effluent characterizat ion showed no reasonable potential for the effluent to cause receiving water chronic toxicity. The proposed permit will not impose a chronic WET limit.

• If this facility makes process or material changes which, in Ecology's opinion, increase the potential for effluent toxicity, then Ecology m ay (in a regulatory order, by permit modification, or in the permit renewal) require the facility to conduct additional effluent characterization.

M. Human Health
Washington’s water quality standards include 91 num eric human health-based criteria that Ecology must consider when writing NPDES permits. These criteria were established in 1992 by the U.S. EPA in its National Toxics Rule (4 0 CFR 131.36). The National Toxics Rule allows states to use mixing zones to evaluate whether discharges comply with human health criteria.
Ecology determined the applicant's discharge does n ot contain chemicals of concern based on existing effluent data or knowledge of discharge s to their system. Ecology will reevaluate this discharge for impacts to human heal th at the next permit reissuance.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 22 R. Koch/Eastern Regional Office N. Sediment Quality
The aquatic sediment standards (chapter 173-204 WAC ) protect aquatic biota and human health. Under these standards Ecology may require a facility to evaluate the potential for its discharge to cause a violation of sediment standard s (WAC 173-204-400). You can obtain additional information about sediments at the Aquat ic Lands Cleanup Unit website at http://www.ecy.wa.gov/programs/tcp/smu/sediment.htm l

. Through a review of the discharger characteristics and of the effluent characteristics, Ecology determined that this discharge has no reaso nable potential to violate the sediment management standards.

O. Ground Water Quality Limits
The ground water quality standards (chapter 173-200 WAC) protect beneficial uses of ground water. Permits issued by Ecology must not a llow violations of those standards (WAC 173-200-100).
The City of Pasco Wastewater Treatment Plant does n ot discharge wastewater to the ground. No permit limits are required to protect ground wat er.

P. Comparison of Effluent Limits with the Previous Per mit Issued on July 7, 2004 Table 9: Comparison of Effluent Limits

Basis of Limit Previous Effluent Limits:

Outfall # 001 Proposed Effluent Limits: Outfall # 001 Average Monthly Average

Weekly Average

Monthly Average

Weekly Biochemical Oxygen Demand (5-day) Technology 30 mg/L 45 mg/L 30 mg/L 45 mg/L
Total Suspended Solids Technology 30 mg/L 45 mg/L 30 mg/L 45 mg/L

Fecal Coliform Bacteria Technology 200/100 mL 400/100 mL 200/100 mL 400/100 mL pH Technology 6.0 to 9.0 6.0 to 9.0

Parameter Average Monthly Maximum

Daily Average

Monthly Maximum

Daily pH Technology 9.0 9.0



### IV. MONITORING REQUIREMENTS

Ecology requires monitoring, recording, and reporti ng (WAC 173-220-210 and 40 CFR 122.41) to verify that the treatment process is functioning correctly and that the discharge complies with the permit’s effluent limits.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 23 R. Koch/Eastern Regional Office The monitoring schedule is detailed in the proposed permit under Condition S.2. Specified monitoring frequencies take into account the quanti ty and variability of the discharge, the treatment method, past compliance, significance of pollutants, and cost of monitoring. The required monitoring frequency is consistent with ag ency guidance given in the current version of Ecology’s Permit Writer's Manual (Publication Number 92-09) for a municipal wastewa ter treatment plant using the activated sludge process and having an annual average flow of between 2 and 5 MGD. Ecology’s Permit Writer's Manual also recommends that WWTP with flow over 1.0 MGD or having a pretreatment program monitor fo r phenols, cyanide, volatile organic compounds, base-neutral compounds and acid-extracta ble compounds.
Monitoring of sludge quantity and quality is necess ary to determine the appropriate uses of the sludge. Biosolids monitoring is required by the cu rrent state and local solid waste management program and also by EPA under 40 CFR 503.
As a pretreatment publicly owned treatment works (P OTW), the City of Pasco is required to sample influent, primary clarifier effluent, final effluent, and sludge for toxic pollutants in order to characterize the industrial input. Sampling is also done to determine if pollutants interfere with the treatment process or pass-through the plan t to the sludge or the receiving water. The City of Pasco will use the monitoring data to devel op local limits which commercial and industrial users must meet.

Q. Lab Accreditation Ecology requires that facilities must use a laborat ory registered or accredited under the provisions of chapter 173-50 WAC, Accreditation of Environmental Laboratories to prepare all monitoring data (with the exception of certain parameters)

. Ecology accredited the laboratory at this facility for the following param eters:

General Chemistry

parameter name method reference matrix *
Alkalinity, Total 2320 B SM N

Ammonia 4500-NH3 D SM 19/20 N Biochemical Oxygen Demand, BOD/CBOD 5210 B SM N
Chlorine Residual, Total 4500-Cl G SM N Dissolved Oxygen 4500-O G SM N

Nitrate 10020 Hach N
pH 4500-H SM N Solids, Total Suspended 2540 D SM N Specific Conductance 2510 B SM N

MicrobiologyFact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 24 R. Koch/Eastern Regional Office

parameter name method reference matrix *

Fecal Coliform - count 9222 D SM N

* Matrix key: D = drinking water; N = non-potable wa ter; S = solids/chem materials; A = air



### V. OTHER PERMIT CONDITIONS

R. Reporting and Record Keeping

Ecology based permit condition S3 on our authority to specify any appropriate reporting and record keeping requirements to prevent and control waste discharges (WAC 173-220-210).

S. Prevention of Facility Overloading
Overloading of the treatment plant is a violation o f the terms and conditions of the permit. To prevent this from occurring, RCW 90.48.110 and W AC 173-220-150 require the City of Pasco to take the actions detailed in proposed perm it requirement S.4 to plan expansions or modifications before existing capacity is reached a nd to report and correct conditions that could result in new or increased discharges of poll utants. Condition S.4 restricts the amount of flow.
The City of Pasco did exceed 85% of the design maxi mum month in October, November and December 2008. This likely is due to infiltrat ion. Historically the highest flows of the year are in the fall of the year. In August 2005, the City requested a capacity analysis of the various components. The trickling filter is the li miting unit process. However, the trickling filter is used as a roughing filter and is not a li miting critical unit. The next limiting process unit at the time of the report was the anaerobic di gester. The solids portion of the plant was upgraded last year and the solids portion of the pl ant is now unlikely to be the limiting factor. It is not clear what the current capacity and design criteria is.
The proposed permit will require an evaluation of t he hydraulic and organic loading capacity of the City of Pasco’s wastewater faciliti es as they currently exist and if necessary make recommendations appropriate for the City’s was tewater facilities to provide twenty years of additional service to the community.

T. Operation and Maintenance (O&M)
The proposed permit contains Condition S.5 as autho rized under RCW 90.48.110, WAC 173-220-150, chapter 173-230 WAC, and WAC 173-240-0 80. Ecology included it to ensure proper operation and regular maintenance of equipment, and to ensure that the City of Pasco Wastewater Treatment Plant takes adequate safeguards so that it uses the constructed facilities to their optimum potential i n terms of pollutant capture and treatment.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 25 R. Koch/Eastern Regional Office U. Pretreatment

Duty to Enforce Discharge Prohibitions
This provision prohibits the publicly owned treatme nt works (POTW) from authorizing or permitting an industrial discharger to discharge ce rtain types of waste into the sanitary

sewer.

• The first section of the pretreatment requirements prohibits the POTW from accepting pollutants which causes “Pass-through” or “Interfer ence”. This general prohibition is from 40 CFR §403.5(a). Appendix B of this fact she et defines these terms.

• The second section reinforces a number of specific State and Federal pretreatment prohibitions found in WAC 173-216-060 and 40 CFR §4 03.5(b). These reinforce that the POTW may not accept certain wastes, which:

• Are prohibited due to dangerous waste rules.

• Are explosive or flammable.

• Have too high or low of a pH (too corrosive, acidic or basic).

• May cause a blockage such as grease, sand, rocks, o r viscous materials.

• Are hot enough to cause a problem.

• Are of sufficient strength or volume to interfere w ith treatment.

• Contain too much petroleum-based oils, mineral oil, or cutting fluid.

• Create noxious or toxic gases at any point.
40 CFR Part 403 contains the regulatory basis for t hese prohibitions, with the exception of the pH provisions which are based on WAC 173-216 -060.

• The third section of pretreatment conditions reflec ts state prohibitions on the POTW accepting certain types of discharges unless the di scharge has received prior written authorization from Ecology. These discharges inclu de:

• Cooling water in significant volumes.

• Stormwater and other direct inflow sources.

• Wastewaters significantly affecting system hydrauli c loading, which do not require treatment.

Federal and State Pretreatment Program Requirements
Ecology administers the Pretreatment Program under the terms of the addendum to the “Memorandum of Understanding between Washington Dep artment of Ecology and the United States Environmental Protection Agency, Regi on 10” (1986) and 40 CFR, part 403. Under this delegation of authority, Ecology issues wastewater discharge permits for significant industrial users (SIUs) discharging to POTWs which have not been delegated authority to issue wastewater discharge permits. E cology must approve, condition, or deny new discharges or a significant increase in the dis charge for existing significant industrial users (SIUs) (40 CFR 403.8 (f)(1)(i) and(iii)).Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 26 R. Koch/Eastern Regional Office Industrial dischargers must obtain a permit from Ec ology before discharging waste to the City of Pasco Wastewater Treatment Plant (WAC 173-2 16-110(5)). Industries discharging wastewater that is similar in character to domestic wastewater do not require a permit.

Routine Identification and Reporting of Industrial Users
The permit requires non-delegated POTWs to take “co ntinuous, routine measures to identify all existing, new, and proposed significant industr ial users (SIUs) and potential significant industrial users (PSIUs)” discharging to their sewe r system. Examples of such routine measures include regular review of water and sewer billing records, business license and building permit applications, advertisements, and p ersonal reconnaissance. System maintenance personnel should be trained on what to look for so they can identify and report new industrial dischargers in the course of perform ing their jobs. The POTW may not allow SIUs to discharge prior to receiving a permit, and must notify all industrial dischargers (significant or not) in writing of their responsibi lity to apply for a State Waste Discharge Permit. The POTW must send a copy of this notifica tion to Ecology.

Requirements for Performing an Industrial User Surv ey The proposed permit is to be issued for 1 year. Th e requirement for an Industrial User Survey has been deleted from the proposed permit. It will be in the following permit.

V. Solid Waste Control
To prevent water quality problems the facility is r equired in permit Condition S7 to store and handle all residual solids (grit, screenings, s cum, sludge, and other solid waste) in accordance with the requirements of RCW 90.48.080 a nd state water quality standards.
The final use and disposal of sewage sludge from th is facility is regulated by U.S. EPA under 40 CFR 503, and by Ecology under chapter 70.9 5J RCW, chapter 173-308 WAC “Biosolids Management,” and chapter 173-350 WAC “So lid Waste Handling Standards.” The disposal of other solid waste is under the juri sdiction of the Benton Franklin County Health District.
Requirements for monitoring sewage sludge and recor d keeping are included in this permit. This information will be used by Ecology to develop or update local limits and is also required under 40 CFR 503.

W. General Conditions
Ecology bases the standardized General Conditions o n state and federal law and regulations. They are included in all individual municipal NPDES permits issued by Ecology.Fact Sheet for NPDES Permit WA-004496-2

Pasco Wastewater Treatment Works

Final Fact Sheet – May 5, 2010 Page 27 R. Koch/Eastern Regional Office



### VI. PERMIT ISSUANCE PROCEDURES

X. Permit Modifications
Ecology may modify this permit to impose numerical limits, if necessary to comply with water quality standards for surface waters, with se diment quality standards, or with water quality standards for ground waters, based on new i nformation from sources such as inspections, effluent monitoring, outfall studies, and effluent mixing studies.
Ecology may also modify this permit to comply with new or amended state or federal regulations.

Y. Proposed Permit Issuance
This proposed permit meets all statutory requiremen ts for Ecology to authorize a wastewater discharge. The permit includes limits and conditio ns to protect human health and aquatic life, and the beneficial uses of waters of the stat e of Washington. Ecology proposes to issue this permit for a term of 1 year with a compliance schedule requiring submission of an engineering report suitable for approval. The engi neering report must evaluate the hydraulic and organic loading capacity of the City of Pasco’s wastewater facilities as they currently exist and if necessary recommend appropriate upgrad e to the wastewater facilities enabling it to provide twenty years of additional service to the community. The report must also include a Tier II antidegradation analysis as descr ibed earlier in the fact sheet.Fact Sheet for NPDES Permit WA-004496-2

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### VII. REFERENCES FOR TEXT AND APPENDICES
Environmental Protection Agency (EPA)

1992. National Toxics Rule. Federal Register, V. 57, No. 246, Tuesday, Decembe r 22, 1992.

1991. Technical Support Document for Water Quality-based Toxics Control . EPA/505/2-90-001.

1988. Technical Guidance on Supplementary Stream Design C onditions for Steady State Modeling. USEPA Office of Water, Washington, D.C.

1985. Water Quality Assessment: A Screening Procedure for Toxic and Conventional Pollutants in Surface and Ground Water . EPA/600/6-85/002a.

1983. Water Quality Standards Handbook. USEPA Office of Water, Washington, D.C.
Tsivoglou, E.C., and J.R. Wallace.

1972. Characterization of Stream Reaeration Capacity . EPA-R3-72-012. (Cited in EPA 1985 op.cit.)

Washington State Department of Ecology.

2006. Permit Writer’s Manual. Publication Number 92-109 ( http://www.ecy.wa.gov/biblio/92109.html )
Laws and Regulations ( http://www.ecy.wa.gov/laws-rules/index.html )

Permit and Wastewater Related Information ( http://www.ecy.wa.gov/programs/wq/wastewater/index. html )

Water Pollution Control Federation.

1976. Chlorination of Wastewater.
Wright, R.M., and A.J. McDonnell.

1979. In-stream Deoxygenation Rate Prediction. Journal Environmental Engineering Division, ASCE. 105(EE2). (Cited in EPA 1985 op.ci t.)Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 29 R. Koch/Eastern Regional Office



### APPENDIX A—PUBLIC INVOLVEMENT INFORMATION
Ecology proposes to reissue a permit to the City of Pasco Wastewater Treatment Plant. The permit includes wastewater discharge limits and oth er conditions. This fact sheet describes the facility and Ecology’s reasons for requiring permit conditions.
Ecology will place a Public Notice of Draft on May 12, 2010 in the Tri-City Herald to inform the public and to invite comment on the proposed draft National Pollutant Discharge Elimination System permit and fact sheet.

The notice –

• Tells where copies of the draft permit and fact she et are available for public evaluation.

• Offers to provide the documents in an alternate for mat to accommodate special needs.

• Asks people to tell us how well the proposed permit would protect the receiving water.

• Invites people to suggest fairer conditions, limits , and requirements for the permit.

• Invites comments on Ecology’s determination of comp liance with antidegradation rules.

• Urges people to submit their comments, in writing, before the end of the comment period.

• Tells how to request a public hearing about the pro posed NPDES permit.

• Explains the next step(s) in the permitting process

. Ecology has published a document entitled Frequently Asked Questions about Effective Public Commenting which is available on our website at http://www.ecy.wa.gov/biblio/0307023.html

. You may obtain further information from Ecology by telephone at (509) 329-3455 or by writing to the address listed below. Water Quality Permit Coordinator Department of Ecology Eastern Regional Office 4601 North Monroe Street Spokane, WA 99205-1295
The primary author of this permit and fact sheet is Richard A. Koch, P.E.Fact Sheet for NPDES Permit WA-004496-2

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### APPENDIX B—GLOSSARY

1-DMax or 1-day maximum temperature - The highest water temperature reached on any given day. This measure can be obtained using calib rated maximum/minimum thermometers or continuous monitoring probes having sampling int ervals of thirty minutes or less.

7-DADMax or 7-day average of the daily maximum temperatures - The arithmetic average of seven consecutive measures of daily maximum tempera tures. The 7-DADMax for any individual day is calculated by averaging that day' s daily maximum temperature with the daily maximum temperatures of the three days prior and the three days after that date. Acute Toxicity - The lethal effect of a compound on an organism that occurs in a short period of time, usually 48 to 96 hours.

AKART - The acronym for “all known, available, and reasonab le methods of prevention, control and treatment.” AKART is a technology-based approa ch to limiting pollutants from wastewater discharges which requires an engineering judgment and an economic judgment. AKART must be applied to all wastes and contaminant s prior to entry into waters of the state in accordance with RCW 90.48.010 and 520, WAC 173-2 00-030(2)(c)(ii), and WAC 173- 216-110(1)(a). Ambient Water Quality - The existing environmental condition of the water i n a receiving water body.

Ammonia - Ammonia is produced by the breakdown of nitrogenous materials in wastewater. Ammonia is toxic to aquatic organisms, exerts an ox ygen demand, and contributes to eutrophication. It also increases the amount of ch lorine needed to disinfect wastewater. Annual Average Design Flow (AADF) - The average of the daily flow volumes anticipated t o occur over a calendar year. Average Monthly Discharge Limit - The average of the measured values obtained over a calendar month's time. Best Management Practices (BMPs) - Schedules of activities, prohibitions of practices, maintenance procedures, and other physical, structu ral and/or managerial practices to prevent or reduce the pollution of waters of the state. BM Ps include treatment systems, operating procedures, and practices to control: plant site r unoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage. B MPs may be further categorized as operational, source control, erosion and sediment c ontrol, and treatment BMPs.
BOD 5 - Determining the Biochemical Oxygen Demand of an effluent is an indirect way of measuring the quantity of organic material present in an effluent that is utilized by bacteria. The BOD 5 is used in modeling to measure the reduction of di ssolved oxygen in receiving waters after effluent is discharged. Stress caused by reduced dissolved oxygen levels makes organisms less competitive and less able to sustain their species in the aquatic environment. Although BOD is not a specific compound, it is defi ned as a conventional pollutant under the federal Clean Water Act. Bypass - The intentional diversion of waste streams from any portion of a treatment facility.
Chlorine - Chlorine is used to disinfect wastewaters of pathog ens harmful to human health. It is also extremely toxic to aquatic life.Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 31 R. Koch/Eastern Regional Office Chronic Toxicity - The effect of a compound on an organism over a rela tively long time, often 1/10 of an organism's lifespan or more. Chronic to xicity can measure survival, reproduction or growth rates, or other parameters to measure the toxic effects of a compound or combination of compounds. Clean Water Act (CWA) - The Federal Water Pollution Control Act enacted by Public Law 92-500, as amended by Public Laws 95-217, 95-576, 9 6-483, 97-117; USC 1251 et seq. Compliance Inspection - Without Sampling - A site visit for the purpose of determining the compliance of a facility with the terms and conditi ons of its permit or with applicable statutes and regulations. Compliance Inspection - With Sampling - A site visit for the purpose of determining the compliance of a facility with the terms and conditi ons of its permit or with applicable statutes and regulations. In addition it includes as a mini mum, sampling and analysis for all parameters with limits in the permit to ascertain c ompliance with those limits; and, for municipal facilities, sampling of influent to ascer tain compliance with the 85 percent removal requirement. Ecology may conduct additional sampli ng. Composite Sample - A mixture of grab samples collected at the same sam pling point at different times, formed either by continuous sampling or by m ixing discrete samples. May be "timecomposite" (collected at constant time intervals) o r "flow-proportional" (collected either as a constant sample volume at time intervals proportion al to stream flow, or collected by increasing the volume of each aliquot as the flow i ncreased while maintaining a constant time interval between the aliquots). Construction Activity - Clearing, grading, excavation, and any other activi ty which disturbs the surface of the land. Such activities may include r oad building; construction of residential houses, office buildings, or industrial buildings; and demolition activity.
Continuous Monitoring - Uninterrupted, unless otherwise noted in the permit

. Critical Condition - The time during which the combination of receiving water and waste discharge conditions have the highest potential for causing toxicity in the receiving water environment. This situation usually occurs when th e flow within a water body is low, thus, its ability to dilute effluent is reduced. Dilution Factor (DF) - A measure of the amount of mixing of effluent and r eceiving water that occurs at the boundary of the mixing zone. Express ed as the inverse of the percent effluent fraction, for example, a dilution factor of 10 mean s the effluent comprises 10% by volume and the receiving water 90%. Engineering Report - A document which thoroughly examines the engineerin g and administrative aspects of a particular domestic or industrial wastewater facility. The report must contain the appropriate information required i n WAC 173-240-060 or 173-240-130.
Fecal Coliform Bacteria - Fecal coliform bacteria are used as indicators of p athogenic bacteria in the effluent that are harmful to humans. Pathog enic bacteria in wastewater discharges are controlled by disinfecting the wastewater. The pre sence of high numbers of fecal coliform bacteria in a water body can indicate the recent re lease of untreated wastewater and/or the presence of animal feces.Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 32 R. Koch/Eastern Regional Office Grab Sample - A single sample or measurement taken at a specific time or over as short a period of time as is feasible.

Industrial Wastewater - Water or liquid-carried waste from industrial or co mmercial processes, as distinct from domestic wastewater. These wastes may result from any process or activity of industry, manufacture, trade or business; from t he development of any natural resource; or from animal operations such as feed lots, poultry h ouses, or dairies. The term includes contaminated storm water and, also, leachate from s olid waste facilities. Major Facility - A facility discharging to surface water with an EPA rating score of > 80 points based on such factors as flow volume, toxic polluta nt potential, and public health impact. Maximum Daily Discharge Limit - The highest allowable daily discharge of a pollutan t measured during a calendar day or any 24-hour perio d that reasonably represents the calendar day for purposes of sampling. The daily discharge is calculated as the average measurement of the pollutant over the day. Maximum Day Design Flow (MDDF) - The largest volume of flow anticipated to occur dur ing a one-day period, expressed as a daily average. Maximum Month Design Flow (MMDF) - The largest volume of flow anticipated to occur during a continuous 30-day period, expressed as a d aily average. Maximum Week Design Flow (MWDF) - The largest volume of flow anticipated to occur during a continuous 7-day period, expressed as a da ily average. Method Detection Level (MDL) - The minimum concentration of a substance that can b e measured and reported with 99 percent confidence th at the pollutant concentration is above zero and is determined from analysis of a sample in a given matrix containing the pollutant. Minor Facility - A facility discharging to surface water with an EPA rating score of < 80 points based on such factors as flow volume, toxic polluta nt potential, and public health impact. Mixing Zone - An area that surrounds an effluent discharge within which water quality criteria may be exceeded. The area of the authorized mixing zone is specified in a facility's permit and follows procedures outlined in state regulation s (chapter 173-201A WAC). National Pollutant Discharge Elimination System (NP DES) - The NPDES (Section 402 of the Clean Water Act) is the federal wastewater permitti ng system for discharges to navigable waters of the United States. Many states, includin g the state of Washington, have been delegated the authority to issue these permits. NP DES permits issued by Washington State permit writers are joint NPDES/State permits issued under both state and federal laws. pH - The pH of a liquid measures its acidity or alkalini ty. It is the negative logarithm of the hydrogen ion concentration. A pH of 7 is defined as neutral, and large variations above or below this value are considered harmful to most aqu atic life. Peak Hour Design Flow (PHDF) - The largest volume of flow anticipated to occur dur ing a one-hour period, expressed as a daily or hourly ave rage. Peak Instantaneous Design Flow (PIDF) - The maximum anticipated instantaneous flow.Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 33 R. Koch/Eastern Regional Office Quantitation Level (QL) - The smallest detectable concentration of analyte g reater than the Method Detection Limit (MDL) where the accuracy (pr ecision &bias) achieves the objectives of the intended purpose.

Reasonable Potential - A reasonable potential to cause a water quality vio lation, or loss of sensitive and/or important habitat. Responsible Corporate Officer - A president, secretary, treasurer, or vice-presiden t of the corporation in charge of a principal business funct ion, or any other person who performs similar policy- or decision-making functions for th e corporation, or the manager of one or more manufacturing, production, or operating facili ties employing more than 250 persons or have gross annual sales or expenditures exceeding $ 25 million (in second quarter 1980 dollars), if authority to sign documents has been a ssigned or delegated to the manager in accordance with corporate procedures (40 CFR 122.22 ). Technology-based Effluent Limit - A permit limit that is based on the ability of a tr eatment method to reduce the pollutant. Total Suspended Solids (TSS) - Total suspended solids is the particulate material in an effluent. Large quantities of TSS discharged to receiving wat ers may result in solids accumulation. Apart from any toxic effects attributable to substa nces leached out by water, suspended solids may kill fish, shellfish, and other aquatic organis ms by causing abrasive injuries and by clogging the gills and respiratory passages of vari ous aquatic fauna. Indirectly, suspended solids can screen out light and can promote and mai ntain the development of noxious conditions through oxygen depletion.
Solid waste - All putrescible and non-putrescible solid and semis olid wastes including, but not limited to, garbage, rubbish, ashes, industrial was tes, swill, sewage sludge, demolition and construction wastes, abandoned vehicles or parts th ereof, contaminated soils and contaminated dredged material, and recyclable mater ials.
State Waters - Lakes, rivers, ponds, streams, inland waters, under ground waters, salt waters, and all other surface waters and watercourses within th e jurisdiction of the state of Washington.
Stormwater - That portion of precipitation that does not natural ly percolate into the ground or evaporate, but flows via overland flow, interflow, pipes, and other features of a storm water drainage system into a defined surface water body, or a constructed infiltration facility. Upset - An exceptional incident in which there is unintenti onal and temporary noncompliance with technology-based permit effluent limits becaus e of factors beyond the reasonable control of the Permittee. An upset does not includ e noncompliance to the extent caused by operational error, improperly designed treatment fa cilities, lack of preventative maintenance, or careless or improper operation. Water Quality-based Effluent Limit - A limit on the concentration of an effluent paramet er that is intended to prevent the concentration of th at parameter from exceeding its water quality criterion after it is discharged into recei ving waters.Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 34 R. Koch/Eastern Regional Office



### APPENDIX C—TECHNICAL CALCULATIONS

Several of the Excel ® spreadsheet tools used to evaluate a discharger’s ability to meet Washington State water quality standards can be fou nd on Ecology’s homepage at http://www.ecy.wa.gov/programs/eap/pwspread/pwsprea d.html

.Fact Sheet for NPDES Permit WA-004496-2

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Final Fact Sheet – May 5, 2010 Page 35 R. Koch/Eastern Regional Office



### APPENDIX D—RESPONSE TO COMMENTS

The public notice that informed the public that a d raft permit was available for review was published in the Tri-City Herald on May 12, 2010. E cology did not receive any comments on the draft permit following the 30-day public comment pe riod.