4.1        Introduction

This chapter reviews the characteristics of key water resources that may be associated with the County’s wastewater management program – the Spokane Valley - Rathdrum Prairie Aquifer, and the Spokane and Little Spokane Rivers.  These water bodies comprise the major components of a large, hydraulically interconnected water system in the Spokane region.  As such, actions affecting one of the resources may have direct or indirect effects on the other resources as well.

The chapter also reviews regulations, water quality issues and other factors that will shape quality requirements for discharge of effluent to receiving waters, beneficial reuse of effluent and beneficial reuse of biosolids.

4.2        The Spokane Valley - Rathdrum Prairie Aquifer System

4.2.1        Location and Nature of the Aquifer

The Spokane Valley - Rathdrum Prairie Aquifer spans an area of about 320 square miles, with about 120 square miles in Spokane County.  It extends from the southern part of Lake Pende Oreille to the Little Spokane River, lying beneath a relatively flat plain bounded on the north and south by mountains (see Drawing 4-1.  Major Regional Water Resources).

The aquifer is mostly unconfined, having a water-table surface that is free to move up and down with seasonal variation in recharge and discharge.  This also means that water from the land surface (along with contaminants) is free to percolate to the groundwater table below.  The aquifer is recharged and replenished primarily through infiltrating rainfall and/or snowmelt, hillside runoff from surrounding watersheds, leakage from the Spokane River between Post Falls and Sullivan Road, and leakage from Lake Coeur d'Alene and numerous other large lakes around the periphery of the Rathdrum Prairie. 

The groundwater generally flows from east to west, from Idaho across the state line and into Washington. Beneath the City of Spokane, the Aquifer splits into two channels.  The major flow follows a northerly path through the Hillyard Trough.  Eventually, this north-flowing water exits the aquifer along the Little Spokane River, discharging through numerous springs and seeps.  Groundwater not following the Hillyard Trough continues westward, flowing through a narrow, gravel-filled channel in the bedrock just north of the Spokane River.  This leads to a stretch of the Spokane River below the falls, where the groundwater leaks back to the river through a number of springs and seeps.

The aquifer serves as the primary water source for dozens of communities (more than 400,000 people) in both Idaho and Washington.  More than 180 large wells pump and discharge water from this regional system.  In 1976, public interest in preserving aquifer quality prompted a coalition of environmental and public interest groups in the Spokane / Coeur d’Alene area to petition the United States Environmental Protection Agency (EPA) for designation of the Spokane Valley – Rathdrum Prairie Aquifer as a “sole source” aquifer.  Authorization for such designation was provided in the Safe Drinking Water Act Amendments of 1974.  EPA approved the petition in February of 1978. .

4.2.2        Hydrogeological Characteristics of the Aquifer

The Spokane aquifer is contained within a porous and permeable framework of unconsolidated sands and gravels that were deposited during the last Ice Age (about 12,000 years ago) as a result of a series of enormous and catastrophic outburst floods.  The sand and gravel deposits are bounded by more competent basalt and granite bedrock with considerably lower permeability.

Water infiltrating from the surface into this sedimentary deposit saturates the lower portion of the sandy material.  Recent seismic-reflection profiling studies show that the aquifer host material is more than 600-feet thick in the area around Opportunity, while thinning to a few feet in thickness along the valley walls.  Generally, the water table that defines the top of the zone-of-water-saturation is near the ground surface (less than 80 feet down in the center part of the Spokane Valley), but can reach depths of more than 300 feet deep in the northern Rathdrum Prairie.

The hydraulic gradient, or slope of the water table surface, is generally towards the west (thus influencing the direction of groundwater flow as described above).  At the state line, the water table lies at an elevation of about 1,980 feet above mean sea level (amsl) and lowers to about 1,600 feet amsl along the Little Spokane River.  During the course of a year, water levels in some locations will fluctuate as much as 15 feet while others will remain unchanged.  The water level variation is dependent on recharge and discharge rates, and changes in river stage.  Long-term declines in the elevation of the water table have not been documented.

Recent technical studies show that the average porosity of the Spokane Aquifer ranges between 10 and 20 percent.  Hydraulic conductivity (or permeability) ranges from 0.1 to more than 10,000 feet/day.  The average seepage velocity of the groundwater is about 30 feet per day.  At this rate, a molecule of groundwater would take about seven years to travel uninterrupted from the state line to the eastern city limits of Spokane near Havana Street.

4.2.3        Interaction Between the Aquifer and the Spokane and Little Spokane Rivers

The Spokane Aquifer is hydraulically connected to the Spokane and Little Spokane Rivers.   To the east of Sullivan Road, the Spokane River loses water to the aquifer; whereas to the west of Sullivan Road, there is a somewhat free exchange of water between the river and aquifer.  Current data suggest the Little Spokane River forms a drainage divide, where the Spokane Aquifer loses most of its flow to the river. 

Numerous gaining and losing reaches of the Spokane River exist between the Washington-Idaho state line and Long Lake.  In the Spokane Valley, the bed of the Spokane River lies at an elevation that is higher than the adjacent groundwater table surface.  Consequently, the river loses large quantities of water through its porous and permeable bed (see Drawing 4-2.  Subsurface Views of the Spokane Aquifer).  For example, based on recent measurements during the summer season, more than 140 cubic feet per second (cfs) of river flow is lost through the riverbed to the underlying aquifer between Post Falls Dam in Idaho and Barker Road in the Spokane Valley. 

In other locations, such as along the Little Spokane River, the water table surface in the aquifer lies at an elevation slightly higher than the water surface in the stream, and the aquifer discharges groundwater to the stream (see Drawing 4-2).  About one-third of the groundwater in the aquifer is discharged to the Little Spokane River in this manner, and another third to the Spokane River below Upriver Dam and the lower reach of the river below the falls.  Based on recent measurements, more than 250 cfs of river flow is added to the Little Spokane River between Dartford and its confluence with the Spokane River.

Drawing 4-3.  Gaining and Losing Reaches identifies the major gaining and losing reaches of the Spokane and Little Spokane Rivers, and Table 4‑1 presents estimates of the volume of water lost or gained during different river flow conditions.  Although knowledge of the system hydrology is improving, there remains considerable uncertainty as to the quantity of water exchanged along each stretch and the variation in the exchange rate that occurs with differing river stages and seasonal conditions.

Table 4‑1.  Gaining and Losing River Reaches

1.  Negative numbers represent a loss of flow

This prolific exchange of surface water and groundwater through the hydraulic connection between the rivers and the aquifer can have significant implications with regard to the quantity and quality of the surface and groundwater resources.

4.2.4        Water Resource Issues

Water Quantity

Recent studies have shown that the flow of groundwater across the state line is less than the original estimates made in the 1960s. The actual flow of water probably hasn't changed in this time; the estimates have gotten more accurate.  In 1968, a U.S. Geological Survey (USGS) study suggested that flow from Idaho to the Spokane Valley "averages about 1,000 cfs, or about 650 million gallons a day." Later USGS reports placed the total Idaho recharge to the aquifer system at about 800 cfs; and in their development of a finite-element model of the aquifer system, Bolke and Vaccaro [i] calculated the through flow across the state line at 457 cfs.  Painter [ii], also utilizing a mass-balance approach that accounted for all recharge points in Idaho, produced an estimate of 753 cfs crossing the state line.  The two most recent modeling efforts, conducted to delineate wellhead protection zones, calculated a flow rate of about 400 cfs at the state line [iii]^, [iv].

In addition to the subsurface flow, a portion of the “trans-state” water supply to the aquifer is carried in the Spokane River.  Much of this water subsequently leaks to the aquifer along “losing” stretches of the river (see earlier discussion).

Water Usage

Current estimates of the safe yield of the Spokane Aquifer lie in the range of 690 to 1,280 cfs [v].  At present, the average cumulative pumping rate of all the largest purveyors is about 331 cfs, with peak pumping rates approaching 500 cfs.  The purveyors’ permits provide for up to 1,009 cfs if all were fully exercised ^v. 

Clearly, the human use of the groundwater resource is approaching the natural supply of the aquifer.  Arguably, groundwater has been over-appropriated if one considers the maximum quantity that the purveyors are legally entitled to pump, as it may out-strip the aquifer’s ability to meet that demand.  If more groundwater is pumped than is available (essentially mining the aquifer), 1) flow in springs and seeps along the Little Spokane River will diminish or disappear; and 2) flow in the Spokane River may diminish further as it begins to lose more water underground and less groundwater is returned to the river.

Future Water Rights Appropriations

In recent years, focus has been placed on maintaining minimum instream flows for various purposes.  For the Spokane and Little Spokane Basins, this creates a situation in which little or no "new" water will be available for consumptive use.  This will create significant problems as purveyors try to reduce per capita water use to support new development.  Innovative ways of using the aquifer's vast storage capacity to augment river flow will be a key element in the future of water resource management.

Minimum streamflows for the Little Spokane River were established by state regulation in 1976 (Chapter 173-555 WAC).  As a result, the Little Spokane River and most of the tributary streams to the Little Spokane River were closed to further consumptive appropriation (except for domestic wells[1] and normal stock watering purposes) during the period of June 1 through October 31 of each year.

To protect fish habitat in the Spokane River, the Washington Department of Fish and Wildlife has recommended a minimum instream flow of 2000 cfs (as measured at the Spokane USGS Gage ‑ 12422500).  The historical record for this gage shows that, in most years, the summer low flow in the river falls below this requirement.  In fact the estimated 7Q10 flow (lowest 7-day average flow that occurs each 10 years) at this gage is 696 cfs.  Given this condition, the Washington Department of Ecology (Ecology) will condition any new surface water rights such that they will be interruptible whenever the flow drops below the 2000-cfs threshold at the Spokane gage.  The ability to grant new water rights for groundwater withdrawn from the Spokane aquifer also revolves around the summer low-flow issues in the Spokane River.  Given the high degree of hydraulic continuity between the river and the aquifer, it is likely that most applications for new water withdrawals from the aquifer will be conditioned by Ecology to prevent them from impairing flow in the river during the summer low-flow period.

Most of the Washington portion of the Spokane aquifer is included in an ongoing watershed planning process, using funds allocated in the "ESHB 2514" legislation, RCW 90.82 . Ultimately, this planning process will produce recommendations on water availability issues within the Water Resource Inventory Areas (WRIAs) for the Middle Spokane and the Little Spokane River watersheds (WRIAs 57 and 55).  One of the principle tasks is to evaluate the interconnectedness of the river/aquifer system, and develop a strategy to resolve issues surrounding the seasonal-low-flow in the river and growth-driven demands for new groundwater uses.

4.2.5        Water Quality Issues

Spokane County, in cooperation with the Spokane Regional Health District and several local water purveyors, conducts a groundwater-monitoring program. Detailed aquifer-wide, water-quality monitoring has been a part of the Water Quality Management Program since its inception over 20 years ago.  After an initial 18-month period of monthly sampling to establish a water-quality base line (1977-1979), an ongoing, quarterly monitoring program was initiated.  Over the years, a combination of public water supply wells, private drinking water wells and special monitoring wells have been part of the network.  During this time, a wide range of inorganic, trace element and organic compounds have been examined.  More than 100,000 individual water quality tests have been performed on more than 4,000 individual samples. 

During the study period, the general water quality of the aquifer has ranged from good to excellent.  From the large number of tests performed, fewer than 50 violations of drinking water standards have been observed.  Most of these observations have been in samples from monitoring wells that draw from near the aquifer surface (i.e., at or near the water table).  By contrast, typical domestic supply wells draw their water at least 30 feet below the water table.  The few water quality problems also tend to be seasonal; after a spring flush of runoff that carries contaminants accumulated in the soil over the winter, contaminant levels drop.  Finally, lower water quality is found predominantly along the edge of the aquifer where the thickness of the saturated zone is small, resulting in low contaminant dilution.  

Following the baseline water quality study in (1977-1979), the general water quality, in terms of inorganic indicators like nitrate-nitrogen and chloride, deteriorated slightly through the mid-1980's.  This resulted primarily from a proliferation of septic tanks and drain fields over the aquifer to serve new development. As the pace of sewer construction increased in the late 1980's and 1990's, the levels of these contaminants under areas served by new sewers began to drop.  That trend continues today.

Table 4‑2 summarizes the most recent water quality data (1999) for 15 monitoring wells and a subset of 13 purveyor wells, for a few basic parameters.  These data reflect aquifer water quality in general; however, considerable variability may be measured in any given well at various depths and during various sampling periods.

Table 4‑2.  Summary of Water Quality Data for Spokane Aquifer

A review of data compiled for the last 20 years allows the following generalizations to be drawn regarding overall water quality in the Spokane aquifer:

§         Average-annual water-quality parameter values vary widely from well to well, and in some cases, from one year to the next in a given well.  Groundwater quality also varies seasonally.

§         Water quality is poorest along the edge of the aquifer and towards the west end of the aquifer flow system, much as was the condition originally measured in 1978.

§         Overall, water quality in the aquifer is good to excellent; water quality standards are rarely violated in wells drawing from the aquifer.

§         Groundwater quality is poorer in samples taken at or near the water table when compared with those taken at greater depth in the zone of saturation.

§         In unsewered areas with residential and commercial development, clear trends exist toward increasing contaminant concentration in some wells.  Conversely, in areas where sewer construction has occurred and/or development has slowed or stopped, contamination levels have fallen.

§         Stormwater injection through drywells in the gravelly soils comprising the aquifer leads to degradation of groundwater quality.

Potential Contamination Sources

Most of the population in the Spokane and Coeur d’Alene area lives and works on top of the aquifer surface.  These activities serve as potential sources of groundwater contamination, now and into the future.  Since the aquifer is mostly unconfined, it is vulnerable to contamination from surface activities. 

Whereas septic tank abatement programs by the City and County of Spokane, and other communities, have substantially reduced contamination potential from this source, drainfields in unsewered areas remain contributors to localized water quality deterioration.  In addition, hundreds of other potential sources of groundwater contamination have been identified in recent wellhead protection investigations.  These include:

§         Stormwater injection through dry wells

§         Chemical storage, transport and accidental spills

§         Improperly abandoned wells

§         Leakage from underground pipelines and sewers

§         Over-application and spillage of fertilizers

§         Application of road de-icing compounds

§         Leakage from above-ground or underground fuel storage tanks and pipelines

§         Improper waste disposal in excavations

§         Sanitary landfills

§         Gravel pit mining

Although these sources have been identified in concept, they do not always threaten groundwater quality.  Nonetheless, unless managed properly, they have the potential to cause significant degradation of water quality in the underlying aquifer system.  As part of the wellhead protection process, the City of Spokane and the Spokane Aquifer Joint Board have compiled a contaminant-source inventory for those areas falling within the Aquifer Sensitive Area.

With the proliferation of sewer construction to abate septic tanks, a major contamination threat is coming under control.  Also, pending changes in stormwater management – caused by new Underground Injection Control and stormwater NPDES permits (discussed below) – will provide increased protection from this significant non-point source.   Given these trends, the most important water quality problem will now be the potential for chemical contamination from spills and leaks.

4.2.6        Aquifer Protection Programs

There are many facets to protection of the Spokane aquifer.  While there are significant programs administered by federal and state agencies, special protection levels for the "sole source" aquifer generally are administered at the local level.  Some of the key programmatic elements are described below.

Water Quality Management Program

Spokane's Water Quality Management Program was set up as a joint County-City effort to direct the implementation of the Water Quality Management Plan (WQMP).  The WQMP was approved as the guidance document for Spokane Valley Aquifer Protection by the Spokane City Council and the Spokane County Board of County Commissioners in the spring of 1979.  During the past 20 years, the WQMP has provided a wide variety of services and administered a number of "regulation adoption" efforts. 

The WQMP includes an extensive public education program and supports a wide range of technical investigations of the region’s water resources.  This work has complimented the plan’s primary charges of groundwater monitoring and promoting the incorporation of aquifer protection into the governmental culture of the region.  Unless local funding is used to replace the EPA money that has funded this education program for the last 12 years, there will be a significant reduction in this work.

Historically, the program has benefited from federal funds; however, the EPA funding source ceased in the fall of 2000.  Program funding will then revert to local sources.  To reduce the cost of the program to County taxpayers, two initiatives are underway:  1) reducing the program to focus on core protection programs, and 2) developing cooperative efforts for both funding and implementing program elements.  An example of the latter initiative is joint county/purveyor support for monitoring and maintaining a Contaminant Source Inventory.

Wellhead Protection

With the completion of the Technical Assessment and Wellhead Protection Area Delineation, the Wellhead Protection Program is moving into an Implementation Phase.  For this phase, the City of Spokane and the Spokane Aquifer Joint Board (the 19 largest water purveyors serving more than 110,000 people in North Spokane and in the Spokane Valley) have merged their efforts.  The expanded group has developed an Implementation Plan that focuses on education.  New "regulations" will be developed for chemical sources near wells and storm water injection wells near water supply wells.  An Implementation Coordinator has been hired to focus on the education efforts and to begin working with city and county staff to develop the needed controls for chemical and injection wells.  

County Utilities Sewer Service Area Expansion

Spokane County continues sewer interceptor construction within the designated Sewer Program Area.  To date, about half of the residents within that area have been connected to the system.  The current construction schedule will result in completion of the sewers within the Sewer Program Area by 2015.  At that time, it is expected that at least 95 percent of the homes and businesses within the County’s wastewater service area will be connected to the system.  By 2020, the County plans to have all homes and businesses connected.

Stormwater Management / Underground Injection

Increased emphasis on Underground Injection Control (UIC) and compliance with Total Maximum Daily Load (TMDL) requirements by EPA and Ecology are having a significant impact on the city and county stormwater management programs.  The UIC program is forcing both the city and county to justify not eliminating more than 10,000 stormwater injection wells that were installed prior to the passage of pretreatment requirements in 1980.  The UIC program should also reduce the risk of groundwater contamination due to chemical spills as injection wells are phased out as a “stormwater management” option on private commercial and industrial areas.  Coupled with likely restrictions on new surface water discharges resulting from evolving TMDLs, the UIC position may require higher levels of stormwater treatment than currently considered in planning.  Both the water quality standards for discharge and the amount of water subject to treatment will increase.

Spokane Regional Health District

The Health District has received funding support from the Aquifer Protection Area (APA) program since 1986.  This support has helped implement the on-site renewable permit program, develop a database of on-site wastewater drainage system locations, and collect purveyor samples for the monitoring program.  As the septic tank abatement program reduces the number of on-site systems that need to be tracked, and purveyor participation in the monitoring program replaces that element of the Health District program, funding from APA will be reduced. 

4.2.7        Technical Information Development

With the end of federal support for the WQMP, support for studies to increase the general understanding of the regions water resources will be effectively eliminated.  Continued "research" will be done using grant funds focused on specific information needs or utility funds to develop information for stormwater and wastewater management.  Currently, there are several programs collecting technical information. Of these, only the Coordinated Monitoring Program will continue when current funding runs out. 

Spokane Aquifer Coordinated Monitoring Program

This program 1) collects and interprets regional aquifer quality data from quarterly sampling, 2) incorporate purveyor drinking-water-compliance monitoring data into the data interpretations, and 3) prepares annual Consumer Confidence Reports required by the Safe Drinking Water Act.

USGS Northern Rocky Mountain Water Quality Assessment

This USGS assessment is a general study of water quality in the Rocky Mountain region.  In 1999, USGS conducted a region-wide evaluation of groundwater quality in the Spokane aquifer.  During the summer and fall of 2000, a study of the interaction between the Spokane aquifer and the Spokane River in the valley is being conducted.  Both water quality and water level data are being evaluated.

Washington Department of Natural Resources (DNR) Geologic Mapping

During the last 10 years, several projects to improve the geologic mapping of the 14 USGS Quads that encompass the Spokane metro area have been conducted.  The first of these was a major effort to remap the Quaternary geology of the Spokane Flood deposits.  This was followed by a series of projects to refine the “hard rock” geology of adjacent areas to provide a better match to the 1:24,000 scale of the quaternary mapping.  The latest effort, being done in connection with the Soil Survey update, involves a final reconciliation of the hard rock and Quaternary geology.

Soil Survey Update

The Natural Resources Conservation Service, with support from the Spokane County Conservation District and Spokane County, is collecting data to update the 1968 Soil Survey for Spokane County.  The project, expected to take a total of five years to complete, was started in 1998.

WRIA Assessments

Spokane County will continue the “assessment” phase for the Middle Spokane and Little Spokane Basins this summer.  The Planning Unit and County staff will finalize water use information for inclusion into the water balance.  A consultant has been selected and will likely begin formal work on the project in August.  Areas of focus will be establishing a water budget for the basins using one of several models and assessing the need for habitat studies for in-stream flow evaluation.

Currently, the County intends to apply for “implementation” funds in June of 2001.  Some of this funding may be directed toward technical studies.  Any technical work is likely to consider the effect of various pumping schemes on river recharge and the potential for using artificial recharge to augment domestic supply availability.

Stormwater Basin Planning

Spokane County's Stormwater Utility has completed the Draft Chester Creek Basin Plan, is currently wrapping up the Glenrose-Moran Prairie Basin Plan, and has initiated work on the West Plains and North Spokane Plans.  Work on one or two more basins could start this year.  A key basin is the Spokane Valley that is scheduled to begin later this year.  All of these plans include information on the quantity of stormwater flowing out of the basin to the aquifer under various development scenarios.  Some water quality information is also available.

The City of Spokane has completed an assessment of stormwater problems on the “south hill”, the Moran Prairie Area in which there was an attempt to tie into the County Glenrose-Moran Prairie Basin Plan.

The Spokane County Engineers Office is beginning a two-year study of stormwater quality and the capability of several treatment options.  

4.2.8        Summary of Key Regulatory/Public Health Measures     

The federal Safe Drinking Water Act contains mandated programs to protect groundwater that contributes to public drinking water supplies.  Locally, the Washington State Department of Health has the authority and responsibility to adopt rules necessary to ensure a safe and reliable public drinking water supply.  This authority includes rulings that establish requirements for water quality, reliability, management, planning, emergency response requirements and reporting requirements as outlined in Chapter 246-290 WAC.  In addition, groundwater quality standards are outlined in Chapter 173-201 WAC.

While there are numerical standards codified in the regulations cited above, a non-degradational policy serves as the basis for aquifer protection planning in Spokane County.  While anti-degradation is also part of the state statute, a Citizen Representatives Core Committee and a Technical Advisory Committee both endorsed non-degradation as being superior to the use of numerical standards as a goal for protecting the Spokane aquifer.  These groups did not feel that the general public would accept water quality levels significantly lower than was available in 1979 to Spokane consumers.  Since then, a groundwater-monitoring program has been used as the primary tool available for assessing compliance with the non-degradation goal.

Non-degradation is defined as a management policy that seeks to prevent the occurrence of aquifer contamination that would cause water quality conditions to deteriorate beyond benchmark levels.  Those benchmark levels are generally accepted as the highest measured values for all water quality parameters included in the original “208” program study (1977-1978).  These benchmarks are location-specific; that is, for each measurement point, the maximum levels recorded in the 208 study should serve as the water quality objectives for the aquifer at that location.

4.3        Surface Waters

4.3.1        Basin Characteristics

Spokane River

The Spokane River is approximately 111 miles long with a watershed covering 6,580 square miles, including the area draining into Lake Coeur d’Alene.  Its source is Lake Coeur d’Alene located in Idaho.  The river flows in a westerly direction from the lake, across the state boundary line, to the city of Spokane.  From there, the river flows in a northwesterly direction to its confluence with the Columbia River.  Major tributaries include the Little Spokane River and Latah (Hangman) Creek.  No significant tributaries enter the Spokane River between the Washington-Idaho state line (River Mile 96.5) and the confluence with Latah Creek (River Mile 72.4).  

For this facilities plan, the area of focus extends from the Stateline Bridge at approximate river mile (RM) 96 to Long Lake Dam at RM 33.9 (see Drawing 4-1).  Within this stretch of the river, there are five hydroelectric dams:  Upriver Dam (RM 79.9), Division Street Diversion Dam (RM 74.4) Monroe Street Dam (RM 73.9), Nine-Mile Dam (RM 57.6) and Long Lake Dam (RM 33.9).  There also is a dam at Post Falls, Idaho (RM 100.8) that influences the hydrodynamics of the river in the area of study.  All of the Washington dams are run-of-the-river types except Long Lake Dam, which creates Long Lake (Lake Spokane), a 24-mile-long reservoir. Avista Utilities operates Long Lake Dam, Nine Mile Dam, Division Street Diversion Dam (Upper Falls Powerhouse) and Monroe Street Dam. Avista also operates the Post Falls Dam in Idaho, which controls the level of Lake Coeur d’Alene.  The City of Spokane operates Upriver Dam.

Little Spokane River

The Little Spokane Watershed (WRIA 55) encompasses approximately 700 square miles along the eastern border of Washington.  The 48.6-mile long river discharges to the Spokane River approximately 5 miles north of the Spokane city limits.  In 1991, the State Legislature designated the lower eight-mile reach of the Little Spokane River a State Scenic River corridor.  A river management plan is being developed to preserve the unique qualities of this portion of the river, which includes a diverse and biologically rich riparian wetland zone.

4.3.2        Hydrology and Water Resource Issues

Spokane River

Due to seasonal rainfall and snowmelt patterns, flow in the Spokane River varies widely during the course of the year.  Historical 30-day average flow rates at the Spokane gage (meter station 12422500) are shown in Figure 4‑1 for the full period of record (1941-1999) and an abbreviated period of record (1968-1999).  The latter period reflects flow records following a change in hydraulic conditions that occurred about 1967-68.  These data indicate that typical river flows range from less than 1000 cfs in August to 5000 - 6000 cfs in January.  Peak flows of upwards of 20,000 cfs usually occur in May or June.

Figure 4‑1.  Historical 30-Day Average Streamflow at the Spokane Gage (Meter Station 12422500)

More extreme flow conditions are shown in Figure 4‑2, which presents the maximum, average and minimum monthly-average stream flows for each calendar month.  During extreme wet weather periods, peak daily streamflow can reach 46,000 cfs.

Figure 4‑2.  Extreme 30-Day Average Streamflow at Spokane Gage 1941-1999 (Meter Station 12422500)

As a result of the interaction between the river and aquifer, flow in the river can vary substantially from location to location, depending on whether the measurement location is in a gaining or losing reach.  This phenomenon is most significant during the low-flow summer period, when flow in the river may be predominantly groundwater discharge.  For example, when the streamflow at the Spokane gage is approximately 800 cfs, it is estimated that 80 percent of the water at this location is aquifer discharge.  By contrast, when the streamflow is 2000 cfs at the same location, it is estimated that only 20 percent of the flow is aquifer discharge, with most streamflow consisting of surface water from Lake Coeur d’Alene that has not entered and left the aquifer.  This phenomena not only influences streamflow, but also water quality since the groundwater discharge has a higher hardness concentration than the surface water and may have different concentrations of dissolved oxygen.

For most water quality characteristics, the critical period occurs in late summer when streamflows are lowest.  Because of this, Ecology typically establishes seasonal permit limits for wastewater discharges, with more stringent requirements in the summer season.  For water-quality based, seasonal effluent limitations, Ecology typically determines allowable loadings using the lowest 7-day average flow that occurs every 20 years (7Q20).  A statistical analysis of historical flow data at the Spokane gage (1941-1999) results in a 7Q20 of 618 cfs; however, a review of the flow data from 1968-1999 (following an apparent change in the river’s hydraulic condition) yields an estimated flow of 530 cfs.  During the recent development of NPDES permit conditions for the Spokane Regional Wastewater Treatment Plant (SAWTP), Ecology used a 7Q20 flow of 604 cfs at the Spokane gage.  For the winter permit period (November – April), the estimated 7Q20 flow at the Spokane gage is 1,532 cfs.

For locations upstream or downstream of the Spokane gage, adjustments must be made to reflect contributions from tributaries and the inflow/outflow of groundwater.  For example, in a recent water-quality modeling effort, Ecology subtracted 246 cfs from the 7Q20 at the Spokane gage to estimate flow near Upriver Dam.  Similarly, the 7Q20 for the Spokane Advanced Wastewater Treatment Plant (806 cfs) is calculated based on the flow at the Spokane gage plus the flow in Latah (Hangman) Creek (meter station 1242400) plus 200 cfs of groundwater inflow.  It should be noted that these values are estimates, and there are no reliable gauging data to validate the assumptions used to adjust flows.

Under low flow conditions, flow in the Spokane River is regulated by operation of the Post Falls dam, which controls water level in Lake Coeur d’Alene.  Avista currently has a management agreement with the State of Idaho to maintain the summer lake level at 2,128 ft amsl.  Between Memorial Day and Labor Day, the Post Falls Dam is allowed to pass the combined flow of the Coeur d’Alene and St. Joe Rivers or 300 cfs, whichever is greater.  Flows below 300 cfs occur when the flow at the dam is restricted for maintenance purposes.  Ecology has calculated the 7Q20 at Post Falls to be 256 cfs based on data from 1968-1999.  EPA and Idaho DEQ used different values during preparation of recent discharge permits for Idaho wastewater discharges to the Spokane River.

Whereas the inflow and outflow of groundwater complicate the hydrology of the mainstream of the Spokane River, the hydrology of Long Lake corresponds almost singularly to surface water inflows and outflows.  In 1991, monthly retention time varied from 7 days in May (during the highest inflows) to 56 days in August (during the lowest inflows).  The annual hydraulic retention time is estimated to be 0.4 years, corresponding to a flushing rate of approximately 25 lake volumes per year.

Little Spokane River

The availability of water in the Little Spokane River Basin has been a concern for a number of years because of declining flows during the summer.  Both groundwater and surface water withdrawals and diversions have impacted the base flows of the Little Spokane River Basin. 

In 1975, water availability was of such concern that the major tributaries of the Little Spokane River were closed to further water appropriation, and water rights issued were conditioned to specific “base” flows.  In August of that year, a “Water Resources Management Program in the Little Spokane River Basin” was completed which formed the basis for a regulation (Chapter 173-555 WAC).  This regulation established a base flow at the Dartford gage of 115 cfs from July 1 through September 15 of each year.  As a result, most of the tributary streams to the Little Spokane River were closed to further consumptive appropriation (except for domestic and normal stock watering purposes) during the period of June 1 through October 31 of each year.

A study of river hydrology prepared by Ecology reviewed trends in 7-day low flows at the Dartford station from 1947 through 1995 [vi]. This study found a 44 cfs decline for the period 1950 through 1995.  From 1975 to 1995, the summer base flow at Dartford dropped below the established base flow (115 cfs) 13 times in 21 years.  Between 1947 and 1974 (27 years), the summer low flow only dropped below 115 cfs four times.

The Dartford gage (meter station 12431000) is located approximately four miles upstream of the confluence with the Spokane River.   Based on data from 1947 to 1995, the calculated 7Q20 flow at Dartford is 91 cfs. 

Upstream of Dartford, it is believed that the summer base flow of the Little Spokane River is supplied by groundwater discharging to the river system along the course of the main stem and tributaries.  During typical summer low flow periods, groundwater inflow (discharge to the Little Spokane River) represents nearly the entire discharge in the main stem of the river (65 to 100 cfs) with the remaining flow originating from the headwaters of the Little Spokane River [vii].  Continued development of exempt wells will detrimentally impact water availability in the basin.  Finding adequate water for future growth in the watershed will be increasingly difficult.

Downstream of Dartford, streamflow increase substantially due to groundwater inflow. It is believed that most of this baseflow is the result of discharge of the Spokane Valley-Rathdrum Aquifer into the river along this stretch.  However, up to one quarter of the flow may result from discharge from groundwater originating in the upper portion of the Little Spokane River Watershed.   The USGS estimates flow in the Little Spokane River at its confluent with the Spokane River by multiplying the flow at Dartford by 1.09 and adding a constant of 252 cfs (USGS Spokane Field office, personal communication, 1995).  This formula estimates the flow to within 10 percent. Recently, additional flow data was collected along this stretch of the river was over a 3-year period, which may allow improved predictions of groundwater discharge rates. Groundwater inflow along this lower section of the river maintains wetlands and rich riparian vegetation.

4.3.3        Stream Classification and Water Quality Criteria

Stream Classes and Characteristic Uses

Definitions of stream classifications and their associated “characteristic uses” are addressed in Chapter 173-201A WAC – Water Quality Standards for Surface Waters of the State of Washington.  Revisions to water quality standards are being considered by the State.

Middle Spokane River.  From River Mile 58.0 (Nine Mile Bridge) to the Idaho State line, the Spokane River is designated as a Class A (excellent) stream.  This designation has the following “characteristic uses”:

§         Water supply (domestic, industrial, agricultural)

§         Stock watering

§         Fish and shellfish

§         Salmonid migration, rearing, spawning, and harvesting

§         Other fish migration, rearing, spawning, and harvesting

§         Clam, oyster and mussel rearing, spawning and harvesting

§         Crustaceans and other shellfish (crabs, shrimp, crayfish, scallops, etc.) rearing, spawning and harvesting

§         Wildlife habitat

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

§         Commerce and navigation

Long Lake. From Long Lake Dam to Nine Mile Bridge, the Spokane River has a “Lake Class” designation, which has essentially the same characteristic uses as the Middle Spokane River.

Little Spokane River.  The Little Spokane River is classified as a Class A stream, despite its designation as a State-listed wild and scenic river.  It has the same characteristic uses as the Middle Spokane River.

Water Quality Standards

To preserve the designated characteristic uses, instream quality must comply with the Washington State Surface Water Quality Standards (Chapter 173-201A WAC).  These standards contain both numerical and narrative criteria.  Numerical water quality criteria specify the levels of pollutants allowed in a receiving water while remaining protective of aquatic life.  Washington’s water quality standards now include 91 numeric health-based criteria that must be considered in NPDES permits. EPA in its National Toxics Rule promulgated these criteria for the state.  Narrative water quality criteria limit toxic, radioactive or deleterious material concentrations below levels that have the potential to adversely affect characteristic water uses, impair aesthetic values or adversely affect human health.  The following discussion summarizes the water quality standards for the Spokane and Little Spokane River systems.

Fecal Coliform.  The allowable levels for fecal coliform are expressed in Table 4‑3 in terms of the number of colonies per 100 mL.

Table 4‑3.  Fecal Coliform Water Quality Standards

Dissolved Oxygen. 

§         Class A Stream – Dissolved oxygen shall exceed 8.0 mg/L.

§         Lake Class – No measurable decrease from natural conditions.

Total Dissolved Gas.  For both Class A and Lake Class designations, total dissolved gas shall not exceed 110 percent of saturation at any point of sample collection.

Temperature.  In Chapter 173-201A-130 WAC, the following special conditions are established for temperature criteria for Long Lake and the Middle Spokane River:

Temperature shall not exceed 20.0^oC due to human activities.  When natural conditions exceed 20.0^oC, no temperature increase will be allowed which will raise the receiving water temperature by greater than 0.3^oC; nor shall such temperature increases, at any time, exceed t = 34/(T + 9).[2] 

No special conditions are designated for the Little Spokane River.  Consequently, the standard criterion for Class A streams applies:

     Temperature shall not exceed 18.0^oC due to human activities.  When natural conditions exceed 18.0^oC, no temperature increase will be allowed which will raise the receiving water temperature by greater than 0.3^oC; nor shall such temperature increases, at any time, exceed t = 28/(T + 7).

pH.  For both Class A and Lake Class designations, pH shall be within a range of 6.5 to 8.5 with a human-caused variation within the above ranges of less than 0.5 units.

Turbidity. 

§         Class A Stream – Turbidity shall not exceed 5 NTU over background turbidity when the background turbidity is 50 TU or less, or have more than a 10 percent increase in turbidity when the background turbidity is more than 50 NTU.

§         Lake Class - Turbidity shall not exceed 5 NTU over background conditions.

Toxic Material.  The State of Washington has established water quality criteria for the toxic substances listed in Table 4‑4.  Specific limits, and their method of calculation, may be found in Chapter 173-201A-040 WAC.

Table 4‑4. Toxic Substances Regulated in Water Quality Standards

Radioactive Material.  For all stream classes, concentrations of radioactive material shall be the lowest practicable concentration attainable and in no case shall exceed:

§         1/12.5 of the values listed in Chapter 246-221-290 WAC

§         USEPA Drinking Water Regulations for radionuclides

Aesthetics.  For both Class A and Lake Class, aesthetic values shall not be impaired by the presence of materials or their effects, excluding those of natural origin, which offend the senses of sight, smell, touch or taste,

Nutrients.  Nutrient limits are not included in the general water quality criteria for Class A and Lake Class designations; however, the following special conditions were established in Chapter 173-201A-130 WAC for Long Lake:

The average eutrophic zone concentration of total phosphorus shall not exceed 25 mg/L during the period of June 1 to October 31.

Critical Condition

Surface water quality criteria are derived for the waterbody’s critical condition, which represents the receiving water and waste discharge condition that has the highest potential for adverse impact on the aquatic biota, human health, and existing or characteristic water body uses.  Typically, the critical condition occurs during summer low flows when dilution is lowest.  For some metals, the critical condition occurs in winter because of the flushing of upstream deposits during high flow events, and the low hardness of the river water, which increases toxicity.

Antidegradation

The State of Washington Antidegradation Policy (WAC 173-201A-070) requires that discharges into a receiving water shall not further degrade the existing water quality of the water body.  The provisions of this policy are outlined below.

§         Existing beneficial uses shall be maintained and protected and no further degradation that would interfere with or become injurious to existing beneficial uses shall be allowed.

§         Whenever the natural conditions of said waters are of a lower quality that the criteria assigned, the natural conditions shall constitute the water quality criteria.

§         Water quality shall be maintained and protected in waters designated as outstanding resource waters.

§         Whenever waters are of a higher quality than the criteria assigned for said waters, the existing water quality shall be protected and pollution of said waters which will reduce the existing quality shall not be allowed, except in those instances where:

§         It is clear, after satisfactory public participation and intergovernmental coordination, that overriding considerations of public interest will be served;

§         All wastes and materials and substances discharged into said waters shall be provided with all known, available and reasonable methods of prevention, control, and treatment by new and existing point sources before discharge.  All activities which result in the pollution of waters from nonpoint sources shall be provided with all known, available, and reasonable best management practices; and

§         When the lowering of water quality in high quality waters is authorized, the lower water quality shall still be of high enough quality to fully support all existing beneficial uses.

§         Short-term modification of water quality may be permitted as conditioned under Chapter 173-201A-110 WAC.

Mixing Zones

Ecology may authorize mixing zones around a point of discharge in establishing surface water-quality-based effluent limits.  Both “acute” and “chronic” mixing zones may be authorized for pollutants that can have a toxic effect on the aquatic environment near the point of discharge.  The concentration of pollutants at the boundary of the mixing zones may not exceed the numerical criteria for that type of zone.

The State’s mixing zone policy is established in Chapter 173-201A-100 WAC.  The allowable size and location of a mixing zone and the associated effluent limits shall be established as part of the discharge permits.  In defining a mixing zone, the State considers the following principles:

§         The discharger shall apply all known and reasonable technology (AKART).

§         Mixing zone determinations shall consider critical discharge conditions.

§         No mixing zone shall be granted unless the supporting information clearly indicates the mixing zone would not have a reasonable potential to cause a loss of sensitive or important habitat, substantially interfere with the existing characteristic uses of the water body, result in damage to the ecosystem, or adversely affect public health.

§         Water quality criteria shall not be violated outside of the boundary of the mixing zone as a result of the discharge for which the mixing zone was authorized.

§         The size of the mixing zone and the concentrations of pollutants present shall be minimized.

In rivers and streams, the maximum size of the mixing zone shall comply with the most restrictive combination of the following:

§         Not extend in a downstream direction for a distance from the discharge port(s) greater than three hundred feet plus the depth of water over the discharge port(s), or extend upstream more than one hundred feet;

§         Not utilize more than twenty-five percent of the flow; and

§         Not occupy more than twenty-five percent of the width of the water body.

The dilution factor will be derived based on the maximum fraction of the river flow authorized for acute (2.5%) and chronic (25%) mixing zones at the established critical conditions (seasonal 7Q20).

Whole Effluent Toxicity

The Water Quality Standards for Surface Waters require that the effluent not cause toxic effects in the receiving waters.  Many toxic pollutants cannot be detected by commonly available detection methods.  However, toxicity can be measured directly by exposing living organisms to the wastewater in laboratory tests and measuring the response of the organisms.  Toxicity tests measure the aggregate toxicity of the whole effluent under standardized conditions, and therefore this approach is called whole effluent toxicity (WET) testing.  Some WET tests measure acute toxicity and other WET tests measure chronic toxicity.

4.3.4        Current Wastewater Discharges

Spokane River

Between Coeur d’Alene Lake and Long Lake, there are seven permitted wastewater discharges to the Spokane River – five publicly owned treatment works (POTW) and two industrial.  Drawing 4-4.  Municipal, Industrial, and Landfill Discharge Locations shows the locations of the discharges, and Table 4‑5 presents the permitted effluent flow rate for each facility along with the average effluent flow in 1999.

Table 4‑5.  Current Wastewater Dischargers

Little Spokane River

Point source discharges within the Little Spokane River watershed include an industrial discharge form the Kaiser-Mead facility and discharge of treated water from a contaminated aquifer underlying the former Colbert landfill (see Drawing 4-4).  The City of Deer Park’s 0.3 mgd treatment plant provides secondary treatment and disperses effluent by land application.

4.3.5        Impaired Water Quality

The Federal Clean Water Act (Section 303{d}) and federal regulations (40 CFR Part 130.7) require Washington State to develop a 303(d) list every two years.  The list is compiled and submitted by Ecology to EPA for approval.  The list describes the health of Washington’s rivers, coastal waters, estuaries and lakes.  The listing of “troubled waters” is used by the state to set environmental priorities for action and to chart water-quality trends.  Water bodies must meet two criteria to be placed on the list: (1) water quality does not meet state water quality standards, and (2) technology-based controls are not sufficient to achieve water quality standards.  The list helps Ecology determine if there are human health concerns, dangers to fish and wildlife, and what kinds of uses the waterbody will support or impair.

In 1998, the State of Washington submitted to EPA a candidate list of impaired or threatened waterbodies – the 303(d) list.  EPA approved this list and added 116 new waterbody/parameter combinations in a final response dated January 28, 2000.  The revised document is referred to as the Ecology’s Final 1998 303(d) List [viii].

Water quality impairment is listed by Water Resource Inventory Area (WRIA) and by township, range and section number, not by river mile.  The following WRIAs are relevant to the study area:  WRIA 54 – Long Lake; WRIA 55 – Little Spokane River; and WRIA 57 – Middle Spokane River.  Table 4‑6 summarizes the water quality constituents on the 303(d) list for these water bodies.

Table 4‑6.  Constituents Listed in Ecology’s Final 1998 303(d) List

¹Elevated concentrations above criterion in fish tissue from the rivers and Long Lake.

²Elevated water concentrations above criteria during various samplings due primarily to upstream sources in Idaho.

³Toxic effects in a single composite sediment sample using Microtox and Chironomus.

⁴Listed due to elevated water concentrations above criterion in two samples from 1989 and 1991.  Later sampling conducted in the river at Riverside State Park in 1995-7 (seven samples) showed no exceedances of the criterion, but wasn’t considered in the decision for listing.

The Spokane River was not listed for certain parameters due to Ecology’s listing policy (10 percent rule) and/or omission of certain databases, but repeated exceedances of criterion have occurred as follows:

§         Cadmium – Elevated water concentrations are often above criterion during highest flows due primarily to upstream sources in Idaho.

§         Fecal Coliform – Nine percent of Ecology’s ambient monitoring samples exceeded the criterion during 9/91 – 9/96.  A CSO impact study conducted for the City of Spokane showed consistent significant violations of the criterion during CSO events. 

§         pH – Repeated exceedances of maximum pH criterion occurred in 1998 as the river dropped below 1000 cfs (Spokane River at Spokane).  There also appears to be an increasing trend in pH during summer low flows as measured at the ambient monitoring station at Riverside Park.

§         Temperature – The Spokane River had repeated exceedances of the special temperature criteria (20^oC) in 1998 when the river dropped below 1000 cfs (Spokane River at Spokane).

In evaluating NPDES permit requirements for the SAWTP, Ecology determined that the discharge had a reasonable potential to cause a violation of human-health-based water quality standards for arsenic.  However, there is considerable uncertainty as to the appropriateness of the human-health-based arsenic criteria and the chemical availability of arsenic in the effluent.  Due to the uncertainties of the criteria, limitations associated with available analytical methods for arsenic, and the presence of natural sources of arsenic in the environment, Ecology decided not to include human-health-based limits for arsenic in permits.  Instead, monitoring of the effluent will be required so that the necessary data will be available to assess the need for a permit limit when the criteria issues are resolved (ref).

The prior NPDES permit for the SAWTP had limits for silver and mercury.  Ecology indicated that there was no reasonable potential to exceed, so these parameters were dropped from the latest permit.  Ecology also said there was no reasonable potential to exceed for copper.

4.3.6        Current or Pending Total Maximum Daily Load Programs

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.  Thus far, TMDLs have been established for the Spokane River for phosphorus and metals (cadmium, lead and zinc).  Currently, the State is conducting a study to determine whether a TMDL is needed to address dissolved oxygen levels in Long Lake and the Spokane River [ix].

Long Lake Phosphorus Management Agreement

Long Lake has a history of water quality problems associated with eutrophication.  These include very low hypolimnetic dissolved oxygen levels and excessive algal growth.  The limiting nutrient for algal growth as determined to be phosphorus.  Consequently, to reduce nutrient loadings to the reservoir and improve the trophic condition, phosphorus removal was implemented at the SAWTP in late 1977.

In 1979, the Spokane River Wasteload Allocation process was initiated in response to a court order.  A phosphorus TMDL was subsequently established by Ecology to protect Long Lake.  Subsequent research and modeling through the 1980’s resulted in the establishment of a seasonal water-quality standard for phosphorus.  This standard set a mean concentration of 25 mg/L for total phosphorus, to be applied to the seasonal median river flow condition.  This results in a total allowable phosphorus loading of 259 kg/day (571 lbs/day) [x].

To implement the phosphorous TMDL, a cooperative agreement was developed in 1989 between wastewater dischargers to the Spokane River and Ecology, U.S. EPA and the Idaho Division of Environmental Quality [xi].  This management plan served as an alternative to the immediate allocation of maximum allowable daily loadings to the individual dischargers. Municipalities participating in the plan include Spokane, Liberty Lake, Post Falls/Rathdrum, Coeur d’Alene and the Hayden Area Regional Sewer Board (HARSB).  Industries include Inland Empire Paper Co., Kaiser Aluminum and the Spokane Industrial Park[3].

Key components of the agreement are summarized below:

§         Municipal Discharges.  To maintain the cumulative phosphorus loading below the target value of 259 kg/day, the management plan outlines a phased implementation program for phosphorus removal.  Starting with the SAWTP, a prioritized sequence was established for the municipalities to implement 85 percent phosphorus removal.  At the time of the agreement, the anticipated sequence for initiating phosphorus treatment was:  1) Coeur d’Alene, 2) Post Falls/Rathdrum, 3) Liberty Lake, and 4) HARSB.  Since that time, Coeur d’Alene and Post Falls/Rathdrum have implemented seasonal phosphorus removal and HARSB has stopped discharging to the river during summer, implementing seasonal land application.  Liberty Lake is planning to implement phosphorus removal as part of plant expansion scheduled within the next 5 years.  Once all municipal dischargers have implemented phosphorus removal, phased implementation of higher removal efficiencies will be needed to accommodate growth while meeting the cumulative mass limit for phosphorus discharge.

§         Industrial Discharges.  The total industrial discharge of phosphorus is limited to a “bubble allocation” of 25 kg/day.  While the individual permits for the three industrial sources specify a maximum loading for each industry, no penalties are assessed for exceedance of these individual loadings as long as the total bubble is not exceeded.  Any unused discharge allowance within the bubble is available for consideration in the overall management plan until actually used by the industries.  The bubble allocation will not be altered until such time as all of the municipalities have been required to implement 85 percent phosphorus removal.  Apparently, when the Spokane Industrial Park ceased direct discharge, the bubble allocation for the remaining industrial dischargers was not adjusted.

§         Technical Advisory Committee.  A Technical Advisory Committee (TAC), established with representation by each discharger and regulatory agency, monitors the regional management plan.

§         Equitable Cost/Benefit Distribution.  Those municipal dischargers that temporally avoid removal costs as a result of the “management-as-needed” approach contribute proportionately to the operating costs of phosphorus removal facilities at the dischargers that initiate removal as a result of the management plan or enhance removal following adoption of the management plan.

§         New Discharges of Phosphorus. Under the agreement, no new point sources of phosphorus to the Spokane River (other than participants to the plan) will be permitted, unless an existing discharger agrees to remove an additional amount of phosphorus sufficient to offset the new source.  The TAC is responsible for reviewing any such agreement and making its recommendation to the appropriate regulatory agency.  This raises an interesting issue since Spokane County flows are now discharged at the SAWTP, and recent facility planning for the SAWTP anticipated increased flows from Spokane County in the future.  In a May 2000 meeting with the County, Ecology interpreted the “no new discharge language” to mean no new loads outside the anticipated growth in the urban area.  Since the County’s growth is anticipated as part of the Greater-Spokane service area, a new discharge can likely be attained, provided the loadings to Long Lake are kept below the action-level threshold.

§         Phosphorus Detergent Ban. In 1990, the Spokane County Health District implemented a phosphate detergent ban in Spokane County to give Coeur d’Alene time to install phosphorus removal technology.  Today, Post Falls, Coeur d’Alene and Spokane ban phosphate detergents.

The current phosphorus TMDL includes allowances for attenuation of phosphorus loadings upstream of Long Lake due to in-river processes and hydraulic attenuation (irrigation withdrawals or seepage to the aquifer).  In fact, about 38 percent of the phosphorus loading to the river is assumed to be attenuated upstream of Nine Mile Dam.  The initial modeling effort concluded that about two-thirds of the phosphorus attenuation was due to in-river processes and the remainder due to hydraulic attenuation. This phosphorus attenuation model will be evaluated and possibly updated as part of the TMDL assessment for dissolved oxygen (see later discussion).

Currently, the total phosphorus loadings to the river are about 200 kg/day.  Earlier predictive modeling performed by the Spokane River TAC indicated that more stringent treatment than 85 percent removal would need to be implemented by 2005; however, performance improvements by the dischargers have resulted in relatively stable phosphorus loadings over the past 7 years.

Metals TMDL

Because of historical mining activities in the upper reaches of the watershed, the Spokane River has elevated concentrations of cadmium, lead and zinc.  At the state line, the instream concentrations of these metals often exceed water quality standards.  Concentrations of dissolved zinc almost continually violate EPA and state water-quality standards (both acute and chronic).  Dissolved lead concentrations are higher than the chronic standard during the high season flow.  The zinc and lead violations occur through most of the river.  Cadmium violates the chronic criteria during high flow, but only in the upper river.  The highest concentrations of all three of these metals occur during the highest flows.  Violations occur every year [xii]. 

These conditions have led to the development of TMDLs in Idaho and Washington [xiii].  The Washington TMDL is based on the assumption that the Idaho work will eventually control pollution sources to the point where Washington’s water quality standards for metals are met at the Washington-Idaho border.  The TMDL is designed to ensure that compliance is maintained in the Spokane River downstream of the state line.

The Washington TMDL regulates effluent metals by requiring that they do not increase the current effluent concentrations of these metals by more than 10 percent, with no limit on mass.  These limits were included in the new NPDES permit for the SAWTP.  The performance-based limits for SAWTP were developed from low-level analytical data for dissolved metals obtained in effluent sampling conducted by the City from July 1996 through May 1999, with an additional 10 percent added as a compliance buffer.  Since the permit must be based on total recoverable metals, these values were calculated by dividing the final dissolved metal limits by dissolved/total recoverable conversion factors.  These factors were determined from effluent data from the period of January 1998 through May 1999.

For other direct discharge to the Spokane River, effluent limits will be placed in NPDES permits once adequate low-level effluent data are developed.  All Spokane River dischargers will have the TMDL-based limits placed in their permits within 2 ½ years from the initiation of monthly low-level monitoring.

The toxicity of the three regulated metals is dependent on the hardness of the water, with increasing toxicity associated with lower hardness values.  Water quality data on hardness collected in the Spokane River show that instream hardness concentrations increase as the flow moves downstream as low hardness water is “lost” to the aquifer and higher hardness water is “gained” from the aquifer.  This trend, shown in Table 4‑7, is particularly significant during summer months when aquifer discharge makes ups a larger portion of the river flow.  Another significant factor is that the hardness of wastewater effluent is significantly higher than the hardness of the Spokane River. This is due primarily to the use of groundwater as the source of domestic supply. Consequently, as the Spokane River flows downstream, its loading capacity for metals increases due to inflow of harder water.  These considerations are significant when assessing alternative locations for potential new discharges to the river.

Table 4‑7.  Median Values of Hardness in Spokane River

Dissolved Oxygen TMDL

Ecology is conducting a study of dissolved oxygen in the Spokane River.  This effort was identified as a high priority during the water quality scoping process for the Spokane Water Quality Management Area [xiv].  The driving force is low dissolved oxygen levels in the Spokane River and Long Lake, which do not meet water quality standards (ref):

§         Monitoring data from Ecology’s ambient monitoring station 57A150 at the Stateline Bridge (period of record - December 1993 to April 1999) indicate that dissolved oxygen violations can occur during the summer period.

§         Dissolved oxygen levels downstream of the Inland Empire Paper (IEP) Company (RM 83.5 to 72.8) were found to be less than 8.0 mg/L for critical conditions (Pelletier 1994, 1997).  This condition was attributed to groundwater inflows with dissolved oxygen less than 8.0 mg/L and high summer river temperatures.  Therefore, the wasteload allocation for IEP was derived based on the BOD load that caused no more than a 0.2 mg/L depletion of dissolved oxygen (considered to be a de minimus impact).

§         Limited sampling data (September 1998) on the Spokane River downstream of the SAWTP suggest that dissolved oxygen violations may occur during the nighttime.

§         Ecology has indicated that low dissolved oxygen levels have been observed in Long Lake; however, Long Lake is not listed for dissolved oxygen in the State’s 303(d) list.

The initial effort is focused on whether a TMDL is needed.  If the results support this action, Ecology will define and implement wasteload allocations for point sources and load allocations for nonpoint sources.

One of the major goals of the project will be to assess the assimilative capacity of the Spokane River system (including Long Lake) with respect to CBOD and ammonia from point and nonpoint loading sources. Nutrient loading also will be incorporated because of its indirect impact on dissolved oxygen through increased primary productivity and resultant plant respiration and decay processes.  These latter impacts can be exacerbated during periods of low river flow and warm temperatures, especially in deep slow-moving segments of the river system like Long Lake.

Ecology is collaborating with the USGS to develop a dynamic water quality model for the study area.  This modeling work is projected to be completed by July 2001.  Once calibrated, this model can be used to evaluate the potential impacts (and required effluent quality) for new or expanded discharges to the Spokane River.

4.3.7        Anticipated Effluent Quality Requirements for a New Surface Water Discharge

To provide a basis for developing potential wastewater management alternatives, a preliminary assessment has been made of likely effluent quality requirements for discharge of wastewater to the Spokane or Little Spokane Rivers.  These potential requirements are summarized in Table 4‑8.  In most cases, the values are presented as a range to reflect the impacts of such factors as location of the discharge along the rivers, effluent flow rate, results of mixing zone studies, effluent concentrations of metals, results of the dissolved oxygen TMDL study, and negotiations with the Phosphorus TAC.  Actual values for a new discharge will be determined by Ecology through the NPDES permitting process.  In this process, the County must demonstrate that the effluent discharge will allow the receiving water to meet water quality standards.  Consequently, the values shown in Table 4‑8 must be regarded as speculative at this time.

Table 4‑8.  Anticipated Effluent Quality Requirements for New
Surface Water Discharges
(Monthly Average Values Unless Noted Otherwise)

1.        Required value will be defined by dissolved oxygen TMDL process.

2.        Required value will be defined by mixing zone study for toxicity.

3.        Required value will be defined through negotiation with Phosphorus TAC. A minimum phosphorus removal rate of 85 percent is required.

4.        Instantaneous value

5.        Required value will be defined based on monitoring of actual effluent metals concentration.

The following discussion explains the basis for the values in Table 4‑8.

§         BOD.  The starting point for BOD is the technology-based standard of 30 mg/L; however, it is likely that the dissolved oxygen TMDL study will lead to substantially more stringent requirements for this parameter during critical low-flow periods in the Spokane River.  Consequently, a seasonal limit in the range of 5 to 10 mg/L is anticipated.  The water quality model being developed by USGS will be used to refine this value.

In the Little Spokane River, a similar seasonal limit of 5-10 mg/L has been assumed.  Although this steam has a lower assimilative capacity than the Spokane River, effluent discharge rates to this receiving water should be low.

Both of these evaluations need to account for groundwater dissolved oxygen as part of the model. 

§         Suspended Solids.  Again, the starting point is the technology-based standard of 30 mg/L.  At this time, there is not a clear water-quality basis for lowering the effluent limits for either receiving water.  However, when developing permit conditions, the State often sets suspended solids limits equal to those for BOD.  For this reason, similar, seasonal limits have been.

§         Ammonia-Nitrogen.  Effluent limits for this parameter will be driven by both near-field impacts associated with toxicity and far-field impacts associated with dissolved oxygen depletion.  Considering these issues, along with the limits established in the recent NPDES permit for the SAWTP, it seems reasonable to anticipate an ammonia-nitrogen limit in the range of 1 to 2 mg/L.

§         Total-Nitrogen.  Since phosphorus has been determined to be the limiting nutrient for algal growth in the Spokane River/Long Lake system, no limits are anticipated for total nitrogen for surface water discharge.

§         Phosphorus.  The allowable effluent concentration for total phosphorus will be determined through negotiations with the Phosphorus TAC, and through the results of the dissolved oxygen TMDL.  At a minimum, a seasonal removal performance of 85 percent will be required, which equates to an effluent phosphorus concentration of about 1 mg/L.  More likely, a higher removal performance will be required since the cumulative phosphorus loading to the river is approaching the TMDL target of 259 kg/day. 

A complicating factor may be an increase in phosphorus loadings from groundwater.  The County’s monitoring data suggests there has been a significant increase in groundwater phosphorus in the Spokane Valley over the last 20 years. 

§         Dissolved Oxygen.  A potential outcome of the dissolved oxygen TMDL is the requirement for a minimum dissolved oxygen concentration in the plant effluent.  If required, this would likely be implemented as a seasonal limit, similar to that for Coeur d’Alene.

§         Pathogen Indicators.  It is anticipated that the water quality standard for Class A streams will serve as the effluent requirement for discharge to the Spokane or Little Spokane Rivers.

§         Chlorine.  The actual residual chlorine limit will be determined through a site-specific mixing zone study.  The value shown in Table 4‑8 approximates the limit in the recent NPDES permit for the SAWTP.

§         pH.  As a starting point, an allowable pH range identical to that established in the SAWTP has been assumed.

§         Metals.  Required effluent concentrations for cadmium, lead and zinc will be based on the results of effluent monitoring once the treatment system is in place.  The values shown in Table 4‑8 are similar to those listed in the SAWTP NPDES permit and reflect the likely order of magnitude of allowable concentrations for a new discharge.

4.4        Effluent Reuse

With appropriate levels of treatment and system management, reclaimed water has been used successfully for applications ranging from agricultural irrigation to industrial process water to indirect potable consumption.  Effective use of this water supply can help ensure that the region’s water resources are put to their highest and best use.

4.4.1        Status of Regulations

Reuse applications in the State of Washington are addressed in the Water Reclamation and Reuse Standards, which were established in 1997 under RCW 90.46 (Reclaimed Water).  These reuse standards are not rules, but are used as guidance for best management practices and development of reclaimed water permit conditions.

Reuse programs must also be protective of groundwater quality.  In this respect, reuse programs must comply with the antidegradation policy set forth in Chapter 173-200 WAC and with the non-degradation policy that serves as the basis for aquifer protection in Spokane County (see earlier discussion in Section 4.2.8). 

Consistent with the region’s focus on protection of the Spokane-Rathdrum Prairie Aquifer, the Idaho Division of Environmental Quality has developed special supplemental guidelines for irrigation with municipal wastewater receiving secondary treatment over the aquifer [xv].  While these guidelines do not apply to reuse applications in Washington State, they establish a precedent for the management of certain types of reuse programs in the area, and should be considered when developing reuse alternatives for Spokane County.  Note that even though total application of water under these guidelines is based on hydraulic uptake, the guidelines were developed to manage nitrate.

4.4.2        Classes of Reclaimed Water

The Water Reclamation and Reuse Standards establish requirements for four classes of reclaimed water with respect to both treatment technique and effluent quality (see Table 4‑9).  The standards then define which classes of reclaimed water can be used for the different reuse applications and define the control measures that must be implemented to protect public health.  Class A water, which has the most stringent treatment requirements, can be used for all reuse applications with minimal restrictions.  By contrast, Class D water may be used for only selected reuse applications where strict controls are in place to minimize human contact with the reclaimed water.

Table 4‑9.  Summary of Treatment and Effluent Quality Requirements for Reclaimed Water Classes

The requirements in Table 4‑9 focus primarily on pathogen control.  For irrigation practices, impoundments, or other applications that result in significant quantities of reclaimed water reaching the underlying aquifer, additional levels of treatment may be needed to protect groundwater quality.  In fact, Ecology has informally indicated that partial reduction of total nitrogen may be needed for irrigation programs located over the aquifer to prevent nitrate contamination.  Otherwise, very restrictive controls may be placed on allowable irrigation rates, which would increase the cost and decrease the feasibility of the irrigation program.

For some reuse applications such as wetlands creation or groundwater recharge, Washington reuse standards establish additional water quality requirements.  The specific water quality limits are addressed later in this section during discussion of these applications. 

The Washington reuse standards also include requirements for treatment reliability to prevent the distribution of any reclaimed water that may not be adequately treated because of a process upset, power outage, or equipment failure.  Reliability requirements include provisions for alarms, standby power supplies, multiple or standby unit treatment processes, emergency storage or disposal provisions, and standby replacement equipment.  The Washington standards outline operations, sampling and analysis, engineering report, and use area requirements, as well as general design criteria for selected unit processes.

4.4.3        Irrigation

For irrigation applications, water quality requirements are generally impacted by several considerations:  the opportunity for humans to contact the reclaimed water as it is being applied, the opportunity for the reclaimed water to contact food for human consumption, and the level of sterilization the food crop will receive before reaching the consumer.  Table 4‑10 summarizes the Classes of reclaimed water that are allowed for various irrigation practices.

Table 4‑10.  Water Quality Requirements for Irrigation Applications

In addition to water quality standards, the reuse rules outline a range of management practices to ensure human health and the environment are protected.  These include Ecology and DOH approval of hydraulic loading rates, prohibition of irrigation when the ground is saturated or frozen and the potential use of groundwater monitoring wells (at the discretion of Ecology and DOH).

4.4.4        Impoundments

Water quality requirements for storage of reclaimed water are presented in Table 4‑11.  If Class A water used, virtually unrestricted recreational uses such as wading and swimming are allowed.

Table 4‑11.  Water Quality Requirements for Impoundments

4.4.5        Setback Requirements

For irrigation and impoundment applications, the Washington reuse rules establish setback requirements to protect the public from aerosols caused by spray irrigation and to separate potable water wells from areas of reclaimed water may seep into the ground.  These requirements are summarized in Table 4‑12.

Table 4‑12.  Setback Requirements

4.4.6        Industrial and Commercial Applications

Table 4‑13 summarizes allowable reclaimed water quality for a wide variety of industrial and commercial applications.  For industrial boiler, cooling and process water applications, additional water quality requirements will be driven by the specific needs of the end user.

Table 4‑13.  Water Quality Requirements for Industrial and Commercial Applications