City of Folsom Groundwater Resources Study

City of Folsom Groundwater Resources Study

An electrical resistivity survey of ten transect lines within the Willow Creek/Humbug Creek was previously conducted to help locate potential drilling locations. Of the ten transects, four transects offered localized areas with the most potential for groundwater. The City of Folsom agreed to pick two sites with the most potential to encounter groundwater, had favorable access, and were located on either end of the study area. The proposed field investigation program will evaluate the geologic and groundwater conditions by installing two deep groundwater monitoring wells and conducting aquifer tests at each location. The two borings will be drilled using air rotary casing hammer (ARCH) drilling techniques. Soil samples will be collected during the drilling from the cyclone. Lithology changes will be noted on the logs during the drilling, as well as, an estimate of the amount of water that the formation is producing at specific depths. The monitoring wells will be constructed inside the borehole using 4-inch diameter, schedule 80 PVC. The depth of the wells and the screen interval will be determined in the field based on the lithology, the depth to static water, and the depth to refusal. The monitoring wells are expected to be completed to about 250 feet bgs with about 100 feet of screen. The wells will be developed by surging, bailing, and pumping at least 24 hours after installation. The new groundwater monitoring wells will be sampled at least 24-hours after development for general minerals and other appropriate water quality constituents. Drill cuttings are not expected to be contaminated and will be spread out in adjacent open areas. Aquifer tests will be conducted in the two new monitoring wells after the wells are properly developed and the groundwater levels have stabilized. The aquifer tests will consist of a constant-rate pumping test in each well. The constant-rate pumping tests will be used to assess the hydraulic conductivity of the aquifer material. Well water produced during drilling and aquifer testing is not expected to be contaminated and will be discharged to nearby open fields, storm drains or ditches. There will be one to two additional vehicles along with the drilling equipment. Field investigations of the boring locations have determined that no significant disturbance to existing environmental resources is expected. Groundwater monitoring will occur on a quarterly basis.

Folsom

Sacramento