WORK PLANS - Laserfiche WebLink

Home Browse Search

Central Valley Regional Water Quality Control Board 6375.4.002.01 Yosemite Avenue Properties February 11, 2005 RESPONSE TO CONDITIONAL WORK PLAN APPROVAL Page 2 FOR GROUNDWATER STUDIES with 8-inch diameter augers. This will allow for an annular seal of three inches between the well casing and the edge of the borehole. The proposed screened interval for the monitoring wells has been modified to extend from ten to twenty feet bgs. The proposed screen interval has been set lower in the ground to maximize the annular seal constructed in each well. We propose to install the bentonite annular seal from seven to eight feet bgs. The annular seal will be constructed of neat cement grout that extends from ground surface to seven feet bgs. The exact depth of the final well screen may vary depending on site conditions during drilling. A typical well construction diagram is attached. Comment 92: "If a slip cap is used on the bottom of the well casing, it must be secured using stainless steel screws." A two-inch bottom well cap will be threaded on the bottom of each well screen section. Comment #3: "Staff recommends that the sand pack be surged prior to installation of the bentonite transition seal to consolidate the filter pack." Each well will be surged, following placement of the filter pack and prior to installation of the bentonite seal to obtain optimal filling of the annual space. Comment #4: "At least 24-hours time should be allowed between placement of the annular seal and development of the well to allow the cement enough time to cure." At least 48 hours after completion of the well installations, each monitoring well will be developed through the use of purging and surge blocks to maximize the hydraulic connection between the well and the surrounding aquifer material. Wells will be purged of a minimum of three casing volumes using a using a 12-volt pump while monitoring stabilization of groundwater parameters (temperature, pH and electrical conductivity). Purging will continue during well development until sediments are minimized. Purge water will be discharged to land onsite. Comment 95: "The discussion of groundwater sampling procedures is inadequate because it doesn't include a table that identifies the analytes, sample containers, preservatives, holding times, detections limits, or analytical methods. A formal Sampling and Analysis Plan (SAP) is recommended to ensure data quality is maintained throughout the project." Sampling procedures and analytical test methods are summarized in the Groundwater Sampling and Analysis Plan attached to this document.