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Rick Dinicola,
Associate Director, WA Water Science Center,
934 Broadway,
Suite 300
Tacoma, WA 98402

(253) 552-1603
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King County Ground Water

Project Summaries

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WA352 - Ground-Water Resources in the Eastern King County Area, Washington - Completed FY1992

Problem - The eastern King County area is comprised of the Snoqualmie River valley lowlands and adjacent plateaus. This area of about 225 square miles is located east of metropolitan Seattle, and pressure for land development is increasing. The last comprehensive study of ground-water resources in the area was made in 1963. An investigation is needed to assess and document the potential for ground-water development in time for appropriate planning and zoning to be accomplished. The shallow alluvial aquifers, where they exist, are also subject to contamination by septic tanks and other surficial sources of pollutants. There is a need to determine what additional data and analyses are needed to quantify the ground-water availability in the area.

Objectives - The objectives are to (1) describe the ground-water system using existing or readily collectable data, (2) determine the general water chemistry of the significant aquifers and describe regional patterns of pollution, if any, (3) evaluate the general potential for ground-water development in terms of aquifer characteristics, interaction with surface-water bodies, and recharge, and (4) determine what additional data and analyses are needed to quantify the ground-water availability in the area.

Approach - About 600-800 wells will be inventoried to provide data for hydrogeologic cross sections, head distribution maps, and hydraulic-conductivity maps. About 150 wells will be sampled and analyzed for common constituents, Fe, Mn, NO3, and fecal-coliform bacteria. Some samples will be analyzed for specific organic compounds and trace metals. Data from existing rainfall-runoff models for several small drainages west of the study area will be used to estimate recharge for the part of the study area west of the Snoqualmie River. Seepage runs will be made on selected streams to evaluate ground-water/surface-water relationships.

WA318 - Preliminary Quantification of Ground-Water in Southwest King County - Completed FY1992

Problem - Since 1969 population growth and ground-water use in King County have increased considerably. Many domestic and municipal wells are being drilled to supply normal needs and peak load water supplies during summer. These are pumping from near-surface sands and gravels; sooner or later the cones of depression will intercept baseflow and withdraw storage from streams and lakes closed to further appropriation. Large capacity wells have been drilled within one mile of Puget Sound to depths below sea level--these may be impacted by salt-water intrusion. A need exists to more precisely define the geometry and flow systems within these strata and the ground/surface-water relationship. In addition serious ground-water quality problems have been identified; one Environmental Protection Agency (EPA) superfund site and several less severe hazardous waste disposal sites are located in the area. A need exists to better define the native ground-water quality and evaluate serious quality-water hazards.

Objectives -

  1. Define and quantify the ground-water system to the extent available or readily collectable data allow;
  2. Determine what additional data, if any, are required to sufficiently characterize the ground-water system in order to allow management decisions for developing further supplies;
  3. Determine the general water chemistry for the major aquifers from which water is being withdrawn; and
  4. Evaluate a select number of sites to determine if water-quality problems exist as a result of land use and/or waste disposal practices.

Approach -

  1. Map the Pleistocene and Holocene sediments;
  2. Inventory and measure water levels for 800-1,000 wells;
  3. Construct closed-loop correlations of drillers' and geophysical logs to define aquifer and aquitard units and draw structure and isopach maps;
  4. Make mass water-level measurement of 300-500 wells to map the flow system within each aquifer;
  5. Estimate recharge to the ground-water system;
  6. Estimate discharge from the ground-water system;
  7. Develop an annual water-budget estimate for the basin within the study area;
  8. Estimate the major pumpage and domestic well use;
  9. Determine water chemistry of the major aquifers and within five select areas determine if water-quality problems exist as a result of land-use practice;
  10. Design an observation well network for use in monitoring temporal water-level and ground-water changes;
  11. Describe additional data and analyses needed to determine GW availability and ground-surface water interaction.

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