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Runs all day Monday and Tuesday (8:00 am - 5:00 pm)

The City of Republic supplies water to approximately 400 services from three production wells (CW-1 through CW-3) that are approximately 80 to 100 feet in depth. The production wells are located within approximately 500 feet of each other and are completed in a shallow unconfined sand and gravel aquifer. The static water level in the unconfined aquifer is approximately 30 feet below ground surface in the vicinity of the wells. The City completed hydrogeologic and Wellhead Protection (WHP) studies for the wells because of concerns regarding the susceptibility of the shallow aquifer to contamination from nearby land use activities. Specifically, the City and the Department of Ecology were concerned about possible water quality impacts from the city sewage lagoons located in the Sanpoil River Valley. The intent of the WHP program prepared for the city was to utilize resource management plans with an emphasis on pollution prevention to protect their drinking water supply.

A detailed field reconnaissance, review of geologic literature and subsurface information presented on water well reports, and limited pump testing of the shallow aquifer indicated the following: (1) the shallow aquifer is generally contained within the valley floors of Granite Creek (a tributary of the Sanpoil River) and the Sanpoil River, (2) the aquifer is generally recharged by precipitation and vertical infiltration from the Sanpoil River and Granite Creek, (3) the hydraulic conductivity of the shallow aquifer ranges from 150 to 250 feet/day, (4) ground water in the relatively steep Granite Creek drainage generally flows from north to south at an average velocity ranging from 10 to 15 feet/day, and (5) ground water in the Sanpoil River Valley generally flows from north to south at an average velocity ranging from 5 to 8 feet/day. The ground water flow system was modeled using a steady-state, 2-dimensional, horizontal aquifer simulation model (FLOWPATH) to estimate the WHP boundaries and critical recharge area for the wells. The model indicated that the 10-year time-of-travel boundary for the aquifer extends approximately 1 mile up the Granite Creek drainage and approximately 3 miles up the Sanpoil River Valley to areas where the shallow aquifer diminishes in thickness.

A list of the potential sources of contamination located in the WHP area and a relative ranking of their potential risk to the aquifer was prepared. Potential contaminant sources identified within the WHP area included: (1) sewage lagoons, (2) petroleum storage tanks, (3) traffic accidents, (4) electrical transformers, (5) pesticide and/or herbicide use associated with agricultural practices, (6) surface water runoff and, (7) septic system effluent. The sewage lagoons were found to be a low risk to the city's water supply because of their location and construction. The greatest risk of aquifer contamination appears to be from petroleum storage tanks located within and immediately adjacent to the 1-year TOT area and from potential traffic accidents occurring within approximately 1,000 feet of the wellheads. The City is currently implementing a ground water monitoring plan that is designed to reduce the risk of potential ground water contamination affecting the city's water supply.

Fitzgerald, Jim, and Clifton, Caty, USDA Forest Service, Umatilla National Forest, 2517 SW Hailey Avenue, Pendleton, OR 97801; (541) 278-3706 or -3822

The Umatilla National Forest located in southeastern Washington and northeastern Oregon, experienced heavy rain in November 1995 and rapid snowmelt in February 1996, resulted in record flooding (i.e., 0.01 recurrence interval). The Umatilla National Forest is conducting a watershed assessment in order to interpret and synthesize the relationships between mass wasting processes, channel morphology, land use, ecosystem health, and flooding. Data collected during the assessment include: 1) mass wasting features; 2) channel morphology changes; 3) performance of culverts at stream-road crossings; and 4) performance of instream fish habitat structures.

A total of 67 debris slides and flows were mapped, each displacing greater than 100 cubic meters of material. Debris torrents were the dominate feature (i.e., 72% of the total). These commonly deposited material into an active stream channel. In the sampled area, 27% of the observed mass wasting features were caused by road failure, however, 63% had no direct association with US Forest Service land management activities.

The common channel responses to the flood events were scouring of substrate and banks, aggradation of sediment and woody debris, and channel migration. These processes appear to differ with elevation and land use intensity. For example, in low elevation heavily managed watersheds where roading, timber harvesting, and grazing occur there appears to be greater occurrence of channel perturbations.

In roaded watersheds, a sampling of 86 culverts at stream-road crossings found that 51% of the culverts failed during flooding. However, at the subwatershed scale, culvert failure varied from 95% to 23%. The high rate of culvert failure is associated with a high frequency of debris flow occurrence. For example, the lower segment of the Tucannon River had a high mass wasting frequency (i.e., 2.4 number of features/km2) and a high rate of culvert failure (74%), which may indicate a cause and effect relationship. Specifically, land use practices may be in part the cause of road failure but are also impacted by mass wasting processes.

A total of 217 instream fish habitat structures (ISS) were inventoried and evaluated with 73% in-place post flooding. Notable differences are apparent at the watershed scale where high order streams (i.e., greater than 4th order) have ISS 80% in-place and only 10% non-functional, whereas third order streams have ISS 60% in-place and 53% non-functional. The highest rate of ISS failure was found in low order streams with poor channel stability. A similar cause and effect relationship is inferred in that mass wasting processes, prevalent in low order streams, induce ISS failure, and these failures augment channel instability.

Preliminary results indicate some differences in watershed response to flooding which may, in part, be attributed to different land use intensity. Investigation of the Blue Mountain's climate, geomorphology, hydrology, and land use is on going and expected to result in a better understanding of processes influencing watershed response to record flood events.

Celto, Emily and Allen, Doug, Spokane County Conservation District, 222 N. Havana, Spokane WA 99202; ecelto@ior.on-ramp.com

The Spokane Watershed Information Committee (SWIC) was formed in October 1994, to help professionals in Spokane County prioritize watershed projects. The goal of SWIC is to share resources, improve efficiency, reduce duplication and provide an information clearinghouse for the Spokane River watershed. The committee determined the most effective way to achieve this goal was to establish a web page for agencies or individuals involved in water quality, watershed planning, or related water issues in the Spokane River watershed.

The web page contains: 1. A bibliography of pertinent published information of water resources and watershed planning. Items such as published water quality data, watershed plans, technical reports, etc., are listed. 2. Information about GIS databases in the Spokane River Watershed. 3. A resource directory with names and contact information of people involved in water resource projects in the watershed. 4. Continued updates of web information including a current calendar.

Participating agencies have included: Spokane County Conservation District, Washington Dept. of Fish and Wildlife, Washington Dept. of Natural Resource, Washington Dept. of Ecology, USDA Natural Resource Conservation Service, USDI Fish and Wildlife Service, Spokane County, Washington Water Power, Eastern Washington University, and Washington State University Cooperative Extension.

Christenson, Douglas H., Simpson Engineers, Inc., 909 N. Argonne Road, Spokane, WA 99212; DougnFern@aol.com

An investigation of surface runoff discharge rates and water quality was conducted for preparation of a stormwater management plan for Cheney, Washington. Four main factors were analyzed for this study: (1) inflow, as actual precipitation and as two-year and 25-year storm intensities; (2) discharge rates, both measured flows and calculated peak discharges; (3) water quality of runoff via the stormwater conveyance system; and (4) capacities of portions of the storm sewer pipe network.

Precipitation data for study year 1995 includes daily rainfall measured in Cheney. The 1995 total of 23.5 inches of precipitation in Cheney is approximately 40% above the average of 16.7 inches. Several months had short-duration precipitation intensities that approached the two-year peak intensity rate for this area, but rainfall was otherwise widely distributed throughout the year, with five months having precipitation 0.5 inch or more above the norm.

Soils with low resistance to erosion on the hills at the northwest edge of Cheney contribute sediments into runoff water, filling ditches and catch basins, while soils having low permeability restrict percolation near discharge sites on the southeast side of town, resulting in uncontrolled ponding.

The area served by Cheney's storm sewer system was divided into twelve basins, based on the area draining to each storm sewer outlet. Six of those basins were analyzed for water quality and discharge rates.

Stormwater runoff was monitored at the six basins' storm sewer discharge sites, usually during or immediately following a significant precipitation event. Flows were measured and discharge rates calculated for comparison of actual flows. Water quality analyses were performed for 16 parameters, with sporadic high values for pH, hardness, phosphorus, nickel and zinc.

Surface hydrology was calculated for the six analyzed basins. Each basin was divided into as many as 25 subbasins, based on the area flowing to selected storm sewer inlets that served as flow concentration points. Each subbasin was mapped, measured and described in terms of subareas, with various runoff coefficients, and time of concentration flow paths. A rational formula hydrology spreadsheet was developed, and both two-year and 25-year peak discharges were calculated for each of 111 subbasins. As future development occurs within any of these subbasins, its calculation sheet can be modified to determine the hydrologic impact.

Storm sewer capacity was computed for two of the basins. Two-year peak discharges were input to each existing pipe system, resulting in each system having pipe segments where the flow exceeded the pipe's capacity.

The City's primary stormwater problem is uncontrolled flows at and below the storm sewer discharge sites. At least one discharge (the site with the highest measured flows) could be piped to an abandoned wastewater treatment cell, which could be converted to a constructed wetland for water quality enhancement and storage needs.

The Cheney Stormwater Management Plan recommends five areas of emphasis: (1) public awareness, (2) local regulations, (3) conveyance system maintenance, (4) continued monitoring, and (5) flow control at discharge points.

Blyler, Karen M., WSU Cooperative Extension, 7612 Pioneer Way East, Puyallup, WA 98371-4998; (206) 840-4556; blyler@coopext.cahe.wsu. edu

The Home and Farm Environmental Assessment System (Home*A*Syst) is a voluntary pollution risk assessment program that helps protect drinking water wells and ground water from contamination. Designed as a unique self-assessment tool, it translates complex environmental, geophysical, and technical information into a useable format that allows individuals to evaluate a wide range of potential contaminants located in and around the rural home or farm.

Using a series of worksheets, the farm operator or home owner evaluates possible sources of toxics, microorganisms, and nitrates on their property. Specifically, activities and structures involving pesticide storage and handling, fertilizer storage and handling, animal waste management, household hazardous waste management, household wastewater, and petroleum storage and handling are analyzed. Worksheet information is further evaluated in terms of the geologic and hydrologic features unique to the site. The individual risks are ranked and an action plan is developed to reduce any high risk situations.

Nitrate, a contaminant usually associated with farm activities, has been found to be the most prevalent and most frequently documented groundwater contaminant in Washington. Home*A* Syst materials focus on activities that help to reduce the potential for nitrate contamination in and around an individual's property. Both farm and non-farm sources of nitrogen are addressed.

The assessments materials incorporate current state and federal regulations. The follow-up action plan includes information on improved management practices, current technologies, and recommended facilities and structures. It is both a home and farm-centered, systematic approach that provides individuals with an opportunity to take their own corrective actions to reduce drinking water contamination risks.

Breckenridge, R. M., Othberg, K. L., Welhan, J. H., Knowles, C. R., Idaho Geological Survey, and McDaniel, P. A., Soils Division, University of Idaho, Moscow, ID 83844

Proper management of the Rathdrum-Spokane valley aquifer necessitates sound geologic understanding of this sole-source aquifer. In spite of numerous water studies, the geologic characteristics of the aquifer remain largely unknown. Historically, the abundance of high-quality water has resulted in little incentive for geologic characterization. In addition, subsurface data from unconsolidated sections has been insufficient for accurate stratigraphic interpretation.

We are studying the surficial geology of the Rathdrum Prairie to better understand the stratigraphy and facies of the valley-fill deposits that compose the aquifer. Principally composed of fine to coarse gravel, the valley-fill units are mainly of glaciofluvial origin and are mantled with thin loess. Bouldery gravels deposited by catastrophic outburst floods from Pleistocene glacial lake Missoula dominate the section. The latest periods of lake emptying cycles occurred in the period from 12,000 to 17,000 years ago. Most of the clasts were derived from glacial outwash of the Purcell Trench Lobe reworked by the flood events. Gravel lithologies are derived from local terranes including the Precambrian Belt Series, the Tertiary and Cretaceous plutons and associated rocks, the lower Paleozoic sediments, and the Miocene basalts.

We recognize four gravel units in the vicinity of the state line based on their grain size, texture, bedding, and depositional environment. The surface of the Rathdrum Prairie is dominated by high-energy fluvial landforms. The thalweg of the valley is occupied by giant current bars; eddy and pendant bars are common at valley margins. The stratigraphy and facies of these units reflect the sequence of catastrophic flood events as well as winnowing and dissection after flood surges.

In addition to defining gravel facies, field investigations in the area also reveal the persistent occurrence of cemented gravel, an important characteristic previously unreported. Cement is prevalent in the proximal flood deposits in the Rathdrum Prairie as well as in the flood deposits within the Lake Missoula basin. X-ray diffraction indicates the composition of the cement is predominantly calcium carbonate. Scanning electron microscope analysis shows fine angular silica is incorporated in the layers of calcium-carbonate coatings. A likely source of the silica is volcanic ash carried downward by infiltrating solutions. While the coatings must have originally formed within a zone of fluctuating ground-water levels, they are now in the aerated zone far above the static water level. The diagenesis of the cement rinds may provide a refined understanding of the history of the aquifer and its variations in hydraulic conductivity. These new data and interpretations are crucial inputs to any hydrologic modeling of the Rathdrum aquifer.