Spokane River Dissolved Metals 

Total Maximum Daily Load 

Submittal Report 

May 1999

Publication No. 99-49-WQ 
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 Spokane River Dissolved Metals 

Total Maximum Daily Load 

Submittal Report 

by 

Steve Butkus 

Ken Merrill 

Washington State Department of Ecology 

Water Quality Program 

Post Office Box 47600 

Olympia, Washington 98504-7600 

May 1999 

Publication No. 99-49-WQ 

Spokane River Metals TMDL Page i

Table of Contents 

List of Figures............................................................................................ii 

List of Tables.............................................................................................ii 

Introduction...............................................................................................1 

Background...............................................................................................3 

Applicable Criteria.......................................................................................4 

Water Quality Impairments.............................................................................6 

Seasonal Variation.......................................................................................6 

Modeling Approach.....................................................................................8 

Loading Capacity ........................................................................................8 

Load and Waste Load Allocations.....................................................................9 

Margin of Safety.........................................................................................10 

Summary Implementation Strategy...................................................................10 

References Cited.........................................................................................12 

Figures.....................................................................................................13 

Appendix A - Public Participation Materials 

Appendix B - Responses to Comments Recieved 

Appendix B - Quality Assurance Project Plan 

Appendix C - Technical Report: Pelletier, G. and K. Merrill. 1998. "Cadmium, Lead, and 

Zinc in the Spokane River - Recommendations for Total Maximum Daily Loads and Waste Load 

Allocations", Publication No. 98-329, Washington Department of Ecology, Olympia, WA. 
Spokane River Metals TMDL Page ii

List of Figures 

Figure 1. Spokane River Drainage System Map..................................................13 

List of Tables 

Table 1. Spokane River 1998 Section 303(d) Listed Segments...................................6 

Table 2. Seasonal Statistics of the Spokane River Total Recoverable Metals 

 at Washington-Idaho Border ...............................................................7 

Table 3. Seasonal Statistics of the Spokane River Hardness......................................7 

Spokane River Metals TMDL Page 1

Introduction 

Section 303(d) of the federal Clean Water Act mandates that the State establish Total Maximum 

Daily Loads (TMDLs) for surface waters that do not meet standards after application of 

technology-based pollution controls. The U.S. Environmental Protection Agency (EPA) has 

established regulations (40 CFR 130) and developed guidance (EPA, 1991) for establishing 

TMDLs. 

Under the Clean Water Act, every state has its own water quality standards designed to protect, 

restore, and preserve water quality. Water quality standards consist of designated uses, such as 

cold water biota and drinking water supply, and criteria, usually numeric criteria, to achieve 

those uses. When a lake, river or stream fails to meet water quality standards after application of 

required technology-based controls, the Clean Water Act requires that the state place the water 

body on a list of "impaired" water bodies and to prepare an analysis called a Total Maximum 

Daily Load (TMDL). 

The goal of a TMDL is to ensure the impaired water will attain water quality standards. A 

TMDL includes a written, quantitative assessment of water quality problems and of the pollutant 

sources that cause the problem. The TMDL determines the amount of a given pollutant which 

can be discharged to the water body and still meet standards, called the loading capacity, and 

allocates that load among the various sources. If the pollutant comes from a discrete source 

(referred to as a point source) such as an industrial facility’s discharge pipe, that facility’s share 

of the loading capacity is called a wasteload allocation. If it comes from a diffuse source 

(referred to as a nonpoint source) such as a farm, that facility’s share is called a load allocation. 

The TMDL must also consider seasonal variations and include a margin of safety that takes into 

account any lack of knowledge about the causes of the water quality problem or its loading 

capacity. The sum of the individual allocations and the margin of safety must be equal to or less 

than the loading capacity. 

The Washington State Department of Ecology (Ecology) is establishing a Total Maximum Daily 

Load (TMDL) for the Spokane River for dissolved cadmium, lead, and zinc. This TMDL will 

address impairments due to potential toxic effects on the five segments of the river listed in the 

1988 Section 303(d) list of impaired surface waters. 
Spokane River Metals TMDL Page 2

The five elements of the Spokane River Dissolved Metals TMDL as required by the Clean Water 

Act are : 

Loading Capacity 

In the case of dissolved metals in the Spokane River, a concentration measure is appropriate 

because the relationship between the effluent-based criterion and the receiving water quality 

holds for all effluent flow rates and critical conditions in the Spokane River. The proposed 

concentration-based allocations assure that the in-river concentration of the metals of concern 

will always be further below the aquatic toxicity criterion downstream of each discharge than 

was present upstream. 

Wasteload Allocation 

The Spokane River dissolved metals waste load allocation is based on the most restrictive permit 

limits derived by either meeting aquatic life toxicity criteria at effluent hardness at the end-ofpipe, or based on maintaining existing concentrations of metals in effluent using performancebased limits with an added 10 percent compliance buffer. Whichever method results in the lower 

limit will be selected for the permit limit and established as the wasteload allocation. A 

minimum of ten representative low-level metals analyses will be required of dischargers where 

adequate metals data does not exist to develop performance-based limits.

Load Allocations 

The load allocation is the concentration required to meet the chronic criterion at the outlet of 

Lake Coeur d'Alene. However, the concentration-based wasteload allocation approach will 

assure compliance with Washington State water quality standards even if the Spokane River only 

meets the standards at the Washington-Idaho border. 

Margin of Safety

Numerous conservative assumptions were made in model development to provide an inherent 

margin of safety. Extreme values of either 90th or 10th percentile values were used to estimate 

critical variables in the model application. In the worst-case scenario, the highest allowable 

effluent concentration as derived from the end-of-pipe, aquatic life criteria method will assure 

that downstream metals concentrations will be further below the aquatic life criteria than present 

upstream of each discharge. It is anticipated that wasteload allocations using the performancebased method will, in many cases, be much less than allocations using the end-of-pipe, aquatic 

life criteria method, and therefore will provide a greater margin of safety. 

Seasonal Variation

Water quality data on metals and hardness collected in the Spokane River show seasonal 

variation at the Washington-Idaho border. The metals data show increasing trends as river flows 

increase. Significant variation in hardness also occurs during the lower river flows when 

groundwater inflow significantly affects river hardness moving progressively downstream in the 

Spokane Valley. The modeling approach used the conservative approach for critical conditions 

when river hardness is low. 
Spokane River Metals TMDL Page 3

Background 

Geographic Setting 

The source of the Spokane River is Lake Coeur d'Alene located in Idaho (Figure 1). The river 

flows in a westerly direction from the lake, across the state boundary line, to the city of Spokane. 

From Spokane, the river flows in a northwesterly direction to its confluence with the Columbia 

River. The Spokane River is approximately 111 miles long with a watershed covering 6,580 

square miles. Major tributaries to the Spokane River include the Little Spokane River and 

Hangman (Latah) Creek. There are six hydroelectric dams located on the Spokane River. 

Forested lands comprise a majority of the land use in Washington (55%), with agriculture (33%), 

urban (6%) and rangeland (3%) following in areas covered. Agricultural lands lie mainly in the 

Lower Spokane River, Little Spokane River, and Hangman Creek watersheds. Urban land use 

occurs mainly in the Middle Spokane River watershed, primarily due to the location of the City 

of Spokane. The population of the greater Spokane is 400,000. Other urban areas include 

Cheney (population 7,700), Medical Lake (population 3,700), Deer Park (population 2,300), and 

Airway Heights (population 2,000). The Spokane Indian Tribe's reservation is located in the 

lower river watershed, covering 155,000 acres of land (Knight, 1998). 

The Spokane River has a complex geological history (Crosby et al., 1971). The basin is 

composed of highly porous, poorly sorted glacial deposits. The upper and lower river substrate 

is composed of granitic rock cobble. From River mile 90 to 85 the substrate is composed of 

rocks and boulders. The river does not exhibit typical riffle-pool morphology (Bailey and Saltes, 

1982). Below the river lies the Spokane-Rathdrum Aquifer, which is the sole source of drinking 

water for the region. 

The climate in the watershed is temperate. The region lies on the edge of a rain shadow created 

by the Cascade Mountain Range. Annual rainfall varies from 14 inches in the lower watershed 

to 35 inches in the upper watershed. The precipitation near the City of Spokane is 17 inches per 

year. The average temperature range is 21°F to 85°F, with extreme temperatures from below 

minus 30°F to over 100°F (Knight, 1998). 

The annual average flow in the Spokane River is approximately 6,300 cfs. The lowest 7-day 

average flow with a 10-year recurrence at the upstream end near Post Falls is approximately 187 

cubic feet per second (cfs). The highest 7-day average flow with a 10-year recurrence is 

approximately 36,000 cfs. Substantial inflows of groundwater enter the river beginning 

downstream from the Liberty Lake outfall. These groundwater inflows significantly increase the 

river flow rate, especially when surface water flows are low. The total net aquifer inflows range 

between 500 to 800 cfs. For comparison, the combined effluent flow from all permitted 

discharges is about 128 cfs (Pelletier and Merrill, 1998). 
Spokane River Metals TMDL Page 4

Description of Pollutant Sources 

Seven wastewater treatment facilities legally discharge to the river. In Idaho, EPA permits the 

following discharges (proceeding downstream from the river source): 

• City of Coeur d'Alene Advanced Wastewater Treatment Plant 

• Hayden Area Regional Sewer Board Publicly-owned Treatment Works 

• City of Post Falls Publicly-owned Treatment Works 

Continuing downstream, Ecology permits discharges from: 

• Liberty Lake Publicly-owned Treatment Works 

• Kaiser Aluminum Industrial Wastewater Treatment Plant 

• Inland Empire Paper Company Industrial Wastewater Treatment Plant 

• City of Spokane Advanced Wastewater Treatment Plant 

Applicable Criteria 

Description of the Applicable Water Quality Standards and 

Numeric Water Quality Target 

Within The State of Washington, water quality standards are published pursuant to Chapter 

90.48 of the Revised Code of Washington (RCW). Authority to adopt rules, regulations, and 

standards as are necessary to protect the environment is vested with the Department of Ecology. 

Under the federal Clean Water Act, the EPA Regional Administrator must approve the water 

quality standards adopted by the State (Section 303(c)(3)). Through adoption of these water 

quality standards, Washington has designated certain characteristic uses to be protected and the 

criteria necessary to protect these uses [Washington Administrative Code (WAC), Chapter 173-

201A). These standards were last adopted in November 1997. 
Spokane River Metals TMDL Page 5

This TMDL is designed to address impairments of characteristic uses caused by toxic effects of 

metals. The characteristic uses designated for protection in the Spokane River are as follows: 

"Characteristic uses. Characteristic uses shall include, but not be limited to, the following: 

(i) Water supply (domestic, industrial, agricultural). 

(ii) Stock watering. 

(iii) Fish and shellfish: 

Salmonid migration, rearing, spawning, and harvesting. 

Other fish migration, rearing, spawning, and harvesting. 

Clam and mussel rearing, spawning, and harvesting. 

Crayfish rearing, spawning, and harvesting. 

(iv) Wildlife habitat. 

(v) Recreation (primary contact recreation, sport fishing, boating, and aesthetic 

enjoyment). 

(vi) Commerce and navigation." 

 [WAC 173-201A-030(2)] 

The water quality standards describe criteria for metals for the protection of characteristic uses. 

The Spokane River TMDL establishes allocations for cadmium, lead, and zinc. The chronic and 

acute criteria of these metals apply to the dissolved form and are calculated using water hardness 

(in mg/L as CaCO3) based on the following equations: 

Dissolved Cadmium 

Chronic < (1.101672-((ln(hardness))*(0.041838)))*EXP(0.7852*(ln(hardness))-3.49) 

Acute < (1.136672-((ln(hardness))*(0.041838)))*EXP(1.128*(ln(hardness))-3.828)

Dissolved Lead 

Chronic < (1.46203-((ln(hardness))*(0.145712)))*EXP(1.273*(ln(hardness))-4.705) 

Acute < (1.46203-((ln(hardness))*(0.145712)))*EXP(1.273*(ln(hardness))-1.46)

Dissolved Zinc 

Chronic < 0.986*EXP(0.8473*(ln(hardness))+0.7614) 

Acute < 0.978*EXP(0.8473*(ln(hardness))+0.8604)

 [WAC 173-201A-040] 
Spokane River Metals TMDL Page 6

Water Quality Impairments 

As a result of measurements made that show criteria are exceeded, the Spokane River 

(representing 18 segments) is included on Washington's 1998 Section 303(d) list (Table 1). 

Table 1. Spokane River 1998 Section 303(d) Listed Segments 

Listed Parameter Segment Location 

(Township-Range-Section) 

Cadmium 25N-46E-06 

Lead 25N-42E-14, 26N-42E-20, 25N-46E-06 

Zinc 25N-42E-14, 26N-42E-20, 26N-42E-33, 25N-44E-03, 25N-46E-06 

PCBs* 27N-40E-22, 26N-42E-05, 26N-42E-07, 28N-37E-33 

Chromium* 25N-42E-04 

Arsenic* 25N-46E-06 

Sediment Bioassay* 28N-37E-33, 25N-43E-01 

Dissolved Oxygen* 25N-44E-06, 25N-46E-06 

pH* 28N-36E-20 

Temperature* 28N-36E-20 

Total Phosphorus* 26N-42E-07 

• not addressed in this TMDL 

Seasonal Variation 

Data on total recoverable cadmium, lead, zinc, and hardness collected by Ecology at the 

Washington-Idaho border between 1991 and 1998 were compiled and descriptive statistics 

generated (Table 2). Sufficient dissolved metals data of which the TMDL is based were not 

available to compute similar statistics. However, similar patterns are observed with total 

recoverable metals and are used here only for presentation. Additional information regarding the 

relationship of dissolved metals with flows is presented in Pelletier and Merrill (1998). The 

dissolved metals vary with the seasonal flows. 

Water quality data on total recoverable metals collected in the Spokane River show seasonal 

variation at the Washington-Idaho border. The total recoverable metals data show increasing 

trends as river flows increase in the spring. Water quality data on hardness collected in the 

Spokane River do not show significant seasonal variation at the Washington-Idaho border. 

However, hardness in the river does exhibit a large summer variation in the lower reaches 

downstream of where significant groundwater contributions to the river are observed (Table 3). 
Spokane River Metals TMDL Page 7

Table 2. Seasonal Statistics of the Spokane River Total Recoverable Metals 

 at Washington-Idaho Border 

Cadmium 

(μg/L) 

Lead 

(μg/L) 

Zinc 

Time Period (μg/L) 

Median Standard 

Deviation 

Median Standard 

Deviation 

Median Standard 

Deviation 

Winter 

(December-February) 

0.3 0.8 1.5 6.2 86.5 12.3 

Spring 

(March-May) 

0.4 0.0 3.1 6.4 89.6 10.3 

Summer 

(June-August) 

0.3 0.1 1.6 3.1 47.0 18.0 

Fall 

(September-November) 

0.2 0.1 1.2 0.7 49.0 23.7 

Annual 

(January-December) 

0.3 0.5 1.5 4.6 79.5 23.0 

Table 3. Seasonal Statistics of the Spokane River Hardness (in mg/L as CaCO3)

River Mile 

100.7

River Mile 

96.0

River Mile 

85.3

River Mile 

Time Period 66.0

Median Standard 

Deviation

Median Standard 

Deviation

Median Standard 

Deviation 

Median Standard 

Deviation

Winter 

(December-February) 

22.0 1.7 23.0 1.1 27.0 3.1 37.0 6.3 

Spring 

(March-May) 

23.0 2.2 23.0 0.6 26.0 1.6 36.0 2.3 

Summer 

(June-August) 

20.0 2.6 20.0 1.7 59.5 29.9 72.0 26.3 

Fall 

(September-November) 

21.0 2.0 20.5 0.7 37.0 3.4 58.0 6.3 

Annual 

(January-December) 

22.0 2.3 22.0 1.4 32.5 20.4 48.5 20.7 
Spokane River Metals TMDL Page 8

Modeling Approach 

Linking Water Quality and Pollutant Sources 

A mass-balance model of the Spokane River was developed to evaluate the effect of different 

effluent loading on metals and hardness (Pelletier and Merrill, 1998). The model includes a flow 

balance that accounts for inflow of water from the outlet of Lake Coeur d'Alene, inflow from 

permitted discharges, and flow exchanges from the aquifer and Hangman Creek. The model 

application assumed that Lake Coeur d'Alene outflow met Washington State water quality 

standards with a hardness of 20 mg/L as CaCO3 and wastewater discharges met aquatic life 

toxicity criteria end-of-pipe ate effluent hardness. The model divides the river into 14 reaches 

from Lake Coeur d'Alene to near the headwaters of Long Lake (RM 64.6). 

Calibration of the model to actual conditions in the river involved estimation of aquifer hardness 

and metals to match observed concentrations in the river. All other inputs in the flow and mass 

balance equations were directly estimated from available data. Relationships between hardness, 

metals, and flow are known at various locations in the river based on long-term ambient 

monitoring data. The model was calibrated for hardness by starting with the known upstream 

hardness and adjusting the groundwater hardness to equate predictions with observed values. 

After the hardness was calibrated, the same approach was used to estimate the dissolved 

cadmium, lead, and zinc of the inflows. 

The calibrated mass-balance model was used to estimate concentrations of metals in the river for 

a variety of river flows and effluent flows. The model was used to evaluate whether water 

quality standards would be violated in the river assuming the river met Washington State water 

quality standards when it leaves Lake Coeur d'Alene and the effluent met aquatic life criteriabased limits at the point of discharge based on effluent hardness. The model results show that 

standards would be met for cadmium and zinc. The standards for lead would be met if the 

maximum concentration of total recoverable lead in the effluent does not exceed the value 

predicted from the extrapolated tangent line of the chronic criterion equation. 

Loading Capacity 

Identification of the loading capacity is an important step in developing TMDLs. The loading 

capacity is the amount of pollutant a water body can receive and still meet water quality 

standards. By definition, a TMDL is the sum of the allocations. An allocation is defined as the 

portion of a receiving water's loading capacity that is assigned to a particular source. EPA 

defines the loading capacity as "the greatest amount of loading that a water can receive without 

violating water quality standards." 
Spokane River Metals TMDL Page 9

The hardness of the wastewater effluent from the various discharges is significantly higher than 

the hardness of the Spokane River. The metals criteria for protection of aquatic life are based on 

hardness, because the toxicity of metals decreases as hardness increases. Thus, as the Spokane 

River flows downstream, its loading capacity for metals increases due to inflow of harder water. 

The Spokane River Metals TMDL utilizes a different measure than “daily loads” to fulfill 

requirements of Section 303(d). Instead, the TMDL is expressed in terms of concentration as 

allowed under EPA regulations [defined as “other appropriate measures” in 40 CFR §130.2(i)]. 

In this case, a concentration measure is appropriate because the relationship between the effluent 

hardness-based criterion and the receiving water quality holds for all river and effluent flow 

rates. The use of effluent flow to establish a loading limit would not only be unnecessary, but 

also could be misconstrued to represent a restriction on effluent flow. Also, a loading limit could 

require unnecessary TMDL and permit modifications to change loading limits as communities 

grow and flows increase. 

Load and Waste Load Allocations 

Cadmium, lead, and zinc concentrations in the Spokane River at the state line often exceed water 

quality standards. EPA and Idaho Department of Environmental Quality are developing a 

TMDL to control pollution sources in Idaho. One of the necessary objectives of the work is to 

meet Washington's water quality standards in the Spokane River. The load allocation is the 

concentration required to meet the chronic criterion at the outlet of Lake Coeur d'Alene. The 

wasteload allocations in Washington assure compliance with Washington State water quality 

standards if the criteria are met only at the Washington-Idaho border 

The waste load allocation is based on the most restrictive permit limits based on the comparison 

of: 

• Potential limits based on meeting aquatic life criteria at effluent hardness, or 

• Potential limits, plus 10%, based on maintaining existing concentrations of metals in effluent, 

where adequate data exist. 

Whichever method results in the lower limit is established as the waste load allocation. 
Spokane River Metals TMDL Page 10

Margin of Safety 

The statute requires that a margin of safety be identified to account for uncertainty when 

establishing a TMDL. The margin of safety can be explicit in the form of an allocation, or 

implicit in the use of conservative assumptions in the analysis. Several assumptions and critical 

conditions used in the modeling analysis of the Spokane River TMDL provide an inherent 

margin of safety as required by the statute. These conservative assumptions and critical 

conditions are listed below: 

• Effluent hardness was assumed to be the 10th percentile hardness as measured at the 

Spokane Advanced Wastewater Treatment Plant 

• Effluent hardness was assumed to be a lower value based on a mixture of river and 

groundwater used for production proposes at the Kaiser Industrial Wastewater Treatment 

Plant. 

• Effluent total recoverable metal concentrations were assumed to be approximate 

maximum values reported. 

• The hardness for the outflow for Lake Coeur d'Alene was assumed to be the seasonal 10th

percentile for the low flow and high flow periods, and the 5th percentile from all seasons. 

• The hardness in the river was assumed to equal the 10% prediction limits from the 

regression equations with flow. 

• The dissolved metals were assumed to equal the 90% prediction limits from the 

regressions with flow. 

Summary Implementation Strategy 

The success of the TMDL largely relies on controlling the upstream sources in Idaho so 

that the toxicity criteria of Washington's Water Quality Standards for Surface Water 

(WAC 173-201 A) are met at the Washington/Idaho border. Effluent limits will be 

placed in all NPDES permits for direct discharge to the Spokane River where adequate 

low-level effluent data exist. 
Spokane River Metals TMDL Page 11

Monitoring Plan for TMDLs Developed Under the Phased 

Approach 

EPA (1991) guidance calls for a monitoring plan for TMDLs where implementation will be 

phased in over time. The monitoring is conducted to provide assurance that the control measures 

achieve the expected load reductions. All Spokane River NPDES discharge permits in 

Washington, which do not currently have adequate metals monitoring, will be opened and 

monthly monitoring will be added by the end of 1999, which will follow appropriate 

clean sampling protocols and EPA 1600-series analytical methods for total recoverable. 

Quarterly dissolved metals monitoring should also be included if source-specific effluent 

dissolved/total recoverable metals ratios are to be determined. 

Reasonable Assurances 

All Spokane River dischargers will have the TMDL-based limits placed in their permits 

within 21⁄2 years from the initiation of monthly low level monitoring. Monitoring 

requirements have already been placed in the Liberty Lake Sewer District permit and 

effluent metals limits will be put into City of Spokane's permit which is now targeted to 

be issued in June 1999. 
Spokane River Metals TMDL Page 12

References Cited 

Bailey, G.C and J. Saltes. Fishery Assessment of the Upper Spokane River. Report 46. State of 

Washington Water Research Center, Pullman, WA. 

Crosby, J.W., et al. 1971. Investigation of techniques to provide advance warning of 

groundwater pollution hazards with special reference to aquifers in glacial outwash. 

Final Report to OWRR, Project No. B-005-WASH. State of Washington Water Research 

Center, Pullman, WA. 

Knight, D.T. 1998. Watershed Approach to Water Quality Management Needs Assessment for 

the Spokane Water Quality Management Area (WRIA 54-57). Publication No. WQ-98-

21. Washington State Department of Ecology, Spokane, WA 

Pelletier, G. and K. Merrill. 1998. Cadmium, Lead, and Zinc in the Spokane River - 

Recommendations for Total Maximum Daily Loads and Waste Load Allocations. Publ. 

No. 98-329. Washington State Department of Ecology, Olympia, WA. 

SASSI, 1993. 1992 Washington State Salmon and Steelhead Stock Inventory. Washington 

Department of Fisheries, Washington Department of Wildlife and Western Washington 

Treaty Indian Tribes. Olympia, WA. 

U.S. Environmental Protection Agency. 1991. Guidance for Water Quality-based Decisions: 

The TMDL Process. EPA 440/4-91-001. Washington, DC. 
Spokane River Metals TMDL Page 13

Figures 

Appendix A 

Public Participation Materials
Appendix B 

Responses to Comments Received
Appendix C 

Quality Assurance Project Plan
Appendix D 

Technical Report

Bound Separately as Ecology Publication No. 98-329