- July 18, 2020
- Posted by: pesenvironmental
Development and Implementation of Hydrologic Design Plan – PES successfully completed the design and implementation of a Hydrogeologic Design Plan and aquifer testing program to assist the North Marin Water District (NMWD) in planning future development of water supply operations at the Gallagher Wells site. The Gallagher Wells site is located along the eastern floodplain terrace of Lagunitas Creek at the privately-owned Gallagher Ranch property. Lagunitas Creek is classified as a Flow-Regulated Mainstream in accordance with the SWRCB Policy for Maintaining Instream Flows in Northern California Coastal Streams for the protection of fishery resources. The Gallagher Wells and Pipeline Project includes the operation of groundwater supply wells at the Gallagher Wells site and delivery of water via a newly constructed one-mile pipeline to the existing NMWD Point Reyes Water Treatment Plant. In response to a Mitigated Negative Declaration for the Gallagher Wells and Pipeline Project, NMWD was required to develop and implement a hydrologic design plan to monitor and maintain stream flow in Lagunitas Creek downstream of the Gallagher Wells site. Our services included:
- To address Mitigation Measure BR-2 of the Mitigated Negative Declaration, PES coordinated with NMWD, U.S. Geological Survey, and the California Department of Fish and Wildlife, to develop and implement the approved design plan to evaluate and monitor potential influences to stream flow in Lagunitas Creek, as a result of municipal well pumping operations at the Gallagher Wells site;
- Design and performance of an aquifer testing program to further characterize hydraulic properties of the alluvial aquifer, and potential surface water-groundwater interaction; and
- Preparation of the Hydrologic Design Plan Report to present the results of the above activities and to comply with requirements of Mitigation Measure BR-2. The results from the aquifer testing program also serve to facilitate NMWD’s future planning for water supply operations at the Gallagher Wells site.
Notification of Potential Streambed Alteration Agreement – As part of our continued services to NMWD, PES prepared the approved Notification of Potential Streambed Alteration report that was submitted to the State of California Department of Fish and Wildlife. The report includes a Monitoring and Reporting Plan for activities to monitor potential changes in stream flow and the wetted profile of Lagunitas Creek in association with future water supply development for the Gallagher Wells and Pipeline Project.
Hydrogeologic Investigation for Siting of Municipal Water Supply Well – PES designed and implemented a hydrogeologic investigation to evaluate the suitability of potential locations for further development of NMWD’s water supply operations at the Gallagher Wells site. The completed scope of work included: (1) initial site reconnaissance of two properties along the floodplain terrace adjacent to Lagunitas Creek; (2) compliance with requirements of the California Coastal Commission for work activities in designated riparian protection and stream buffer areas; (3) drilling six soil test borings to depths ranging from 35 to 67 feet ft bgs; (4) constructing temporary piezometers (i.e., for short-term groundwater level monitoring) at two of the soil test boring locations; (5) development and implementation of a groundwater level monitoring program to evaluate groundwater conditions in response to municipal pumping operations at the Gallagher Wells site; and (6) preparation of a technical report which presents the evaluation of hydrogeologic data, and recommendation for location of a test well with the goal to further develop water resources at the Gallagher Ranch property under amended water rights issued to NMWD by the SWRCB. Construction of the test/water supply well is currently pending arrangements for easement-grant access with a private property owner.