Drilling and Construction of Monitoring Wells – Mound Basin

Drilling and Construction of Monitoring Wells – Mound Basin

The Department of Water Resources Technical Support Services Program proposes to install three clustered monitoring wells at the location described above. The Mound Basin Groundwater Sustainability Agency (MBGSA) and its stakeholders require groundwater monitoring data, collected from the proposed wells. The project will correlate existing geophysical survey data with the subsurface conditions at the proposed Project site to increase subsurface knowledge of the groundwater basin. To accomplish this objective, an exploratory borehole would be drilled to approximately 1,500’ below ground surface (bgs) using a mud rotary drill rig. After conducting a geophysical survey in the borehole, one monitoring well would be constructed. Based on the data collected from the exploratory borehole, two additional shallow monitoring wells would be drilled and completed immediately adjacent to the exploratory borehole. The depths of the completed monitoring wells would be dependent on drilling conditions, encountered lithology, and data from the geophysical survey; the estimated total depths of the proposed monitoring wells would be approximately 100' to 200' bgs, 400' to 500’ bgs, and 1,150’ to 1,250’ bgs. The proposed wells would be constructed within an area of about 1250 ft2 on a dirt lot located in the Ventura Sewer and Wastewater Services Facility property. Construction would consist of three phases. The initial phase would last about one week and be mobilization and transporting of equipment and supplies from Signal Hill, CA to the proposed Project site I-405, and CA-101. Phase 2 would be to drill and construct the monitoring wells. Phase 3 would entail development (cleaning) of each well. Overall, phases 2 and 3 would last approximately one month. Demobilization would take approximately one week to transport equipment and supplies back to Signal Hill, CA via I-405, and CA-101. During drilling and well construction, the borehole water and drilling fluid would be contained within plastic lined 20-yard roll off bins to allow settling of the heavy particles (i.e. sand, silt, clay, gravel) from the lighter materials (water, and fluids). The fluid fraction would be pumped into the wastewater treatment facility on-site to be treated and used by the Ventura Sewer and Wastewater Services Facility. The heavier particles would then be transported off-site to the Caglia Environmental waste disposal facility in Fresno, CA. Native drill cuttings would be stored nearby on an unused dirt lot on Ventura Sewer and Wastewater Services Facility property. Should water and soil testing reveal contaminants of special concern above threshold levels, the water and cuttings would be disposed at Caglia Environmental, located in Fresno. Fluids and drill cuttings would be expected to be clean and nonhazardous. After the completion of the well construction phase, each well would be developed using industry standard methods, including bailing, surging-and-swabbing, and pumping. Initially, the development fluids from each well would be turbid, i.e. contain clay, silt, and sand particles. The turbidity of these fluids would progressively and rapidly decrease through continued development. Upon completion of the wells’ development, each of the clustered wells would be enclosed within a 3’x3’ square galvanized vault with a flush-mount, hinged, traffic-rated well cover set in a 4’x4’x4’ concrete vault box.

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