Sunnyoaks Pond1 Soil and Groundwater Investigation

Sunnyoaks Pond1 Soil and Groundwater Investigation

The project is needed to characterize physical and chemical heterogeneity of soil and groundwater beneath Valley Water’s Sunnyoaks Groundwater Percolation Pond 1. The project would improve Valley Water’s understanding of site-specific recharge conditions at the Sunnyoaks Groundwater Percolation Ponds and would inform the sustainable management and protection of the Santa Clara Groundwater Subbasin. Valley Water's Sunnyoaks Groundwater Percolation Ponds are important assets in Valley Water’s managed groundwater recharge portfolio. The project would help to ensure optimal recharge operations continue into the future by conducting a soil and shallow groundwater investigation to characterize the physical and chemical heterogeneity of soil and groundwater beneath Sunnyoaks Pond 1. The results of the investigation would inform Valley Water’s understanding of site-specific recharge infiltration processes, as well as soil and groundwater quality beneath the site. The project would help Valley Water in its mission to sustainably manage and protect Santa Clara County’s groundwater resources. The scope of work proposed for this investigation consists of drilling up to five deep (~50 ft) and ten shallow (~3 ft) soil borings within Pond 1, which has been dry for over a year. The borings would be advanced using a Geoprobe 7822 DT drill rig—a compact. limited-access, track-mounted rig that would ingress/egress the pond via a northern boat ramp. The borings would be drilled using 2-inch diameter core barrels and would vertically profile soils down to and just below the water table (groundwater). When water is encountered at depth (between ~20-50 ft), the driller would install a temporary PVC well casing through which groundwater would be pumped into sample containers using a portable peristaltic pump or equivalent. Continuous soil cores would be simultaneously extracted, and soil samples would be collected for physical and chemical characterization along vertical increments. Once the groundwater and soil samples are collected, each borehole would be backfilled to the ground surface with neat cement grout. Staging would occur immediately north of Pond 1, between the pond and fire training tower. Valley Water staff would oversee all on-site work and would collect soil and groundwater samples retrieved from depths within each boring. These samples would be shipped to a third-party laboratory for analyses. All other soil and groundwater generated by the project would be contained and stored in 55-gallon drums onsite, and subsequently disposed of by a licensed waste hauler. After completion of sampling, the drilling contractor would backfill each boring with neat cement grout to the surface. Project duration is expected to be 3-4 days.

Campbell

Santa Clara

San Francisco Bay Area

Santa Clara