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1 Introduction
The City of Sequim is located on the Sequim-Dungeness Peninsula, which extends off the Olympic Peninsula in Clallam County, Washington (Figure 1). The City obtains its drinking water from three groundwater sources located east of the Dungeness River, and has undertaken several large-scale water projects since the mid-1990's. These projects include:
- Development of a new wellfield at Port Williams Road;
- Installation of a Class "A" treatment system at the wastewater treatment plant;
- Construction of a pipeline to transmit the reclaimed water to points of use; and,
- Reuse of reclaimed water for irrigation and Bell Creek flow augmentation.
Based on its dedication to responsible water-resource management, environmental protection, and data sharing with interested parties, the City has established a monitoring program designed to document pumping withdrawals, groundwater level trends, precipitation trends, and water quality in both groundwater and Bell Creek. The monitoring program adds to the growing body of hydrologic data and supports evaluation of how observed hydrologic changes relate to changes in groundwater pumping and septic densities (i.e. population based changes) as well as changes in irrigation practices, and climatic variation. The monitoring is also designed to provide "early warnings" of hydrologic trends of potential concern to water-resource stakeholders. While some of the monitoring data have been discussed in prior reports (e.g. PGG, 1996 and PGG, 1998), this is the first report that provides all the data in one place as well as a more comprehensive interpretation. In addition, this report incorporates monitoring data collected on the Sequim-Dungeness Peninsula by other agencies and organizations.
In this report, groundwater level trends are interpreted in light of changes in pumping withdrawals (by the City and other water users), changes in recharge from irrigation, and variation in recharge from precipitation. Water quality analyses from the City's drinking water sources are evaluated relative to State Drinking Water Quality Standards, and water quality analyses from Bell Creek are evaluated relative to State Surface-Water Quality Standards. The analyses presented herein provide an overview of how the hydrologic system is responding to the City's water-resource management activities.
Pacific Groundwater Group (PGG) has assisted the City in developing its monitoring program since the mid-1990's. Our role in preparing this report was to: compile existing monitoring data from the City and other sources, present the data in readily understandable graphical formats, interpret the data with respect to water resource management and the "health" of the hydrologic system, and provide recommendations for future monitoring activities. City staff were instrumental in explaining system operations and compiling data available in hardcopy. PGG's work was performed, and this report prepared using generally accepted hydrogeologic practices used at this time and in this vicinity, for the exclusive use of the City of Sequim and for exclusive application to City's monitoring program. This is in lieu of other warranties, express or implied.
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