WORK PLANS - Laserfiche WebLink

Home Browse Search

KLEINFELDER The well borings will be advanced to approximately 25 feet below the ground surface. Based upon available information, we anticipate groundwater in the vicinity of the project site to be present at a depth of approximately 15 feet below the ground surface, with a groundwater flow direction to the west. The soil borings will be advanced approximately 10 feet into groundwater. Following completion of the drilling, a 2-inch diameter PVC monitoring well will be installed in the borings. The monitoring wells will be constructed with schedule 40 PVC, a 15 foot long .010 or.020 inch screened section. The bottom cap on the screened section shall be fitted with a threaded end cap or secured with stainless steel screws in the event that a slip cap is used. The screened section will be placed approximately 10-feet below and 5-feet above first encountered groundwater. The screened section will be surrounded by and covered by clean sand filter pack (#2/12 or#2/16) installed via tremmie. The sand filter pack shall be surged to aid in settling the sand filter pack and replenished prior to installation of the bentonite transition seal. A 3 to 5 foot bentonite transition seal will be installed above the filter pack via tremmie. The actual choice of screen and sand size for the filter pack will be determined after field observations of the soils present has been conducted. See Plate 3 for a typical monitoring well construction diagram. 4.3. MONITORING WELL DEVELOPMENT AND SAMPLING A minimum of 48 hours after installation, the monitoring wells will be developed to remove fine silt from the well bore and to effectively increase the hydraulic radius of each monitoring well. Surging along the screened interval of the well will be performed to draw the sediment from the formation into the filter pack and the well and to set the sand pack. The monitoring wells will be developed as described in Appendix A.3.2. In addition to developing the monitoring wells until the discharge runs relatively clear of fines, the discharge will be periodically monitored for pH, temperature, and specific conductance to record stable groundwater parameters during the development task. Sampling of the new wells will be conducted at least 24 hours after well development. Water level measurements will be conducted prior to purging and sampling the wells. The depth to groundwater will then be measured in each well according to the protocol described in Appendix A-4.1. Approximately three to five well volumes will be purged and samples will be collected as described in Appendix A-4.2. Each of the water samples collected for quantitative analyses will be submitted under chain-of-custody control to a State of California-certified laboratory for the requested analyses. The monitoring wells will be surveyed for elevation and location by a State licensed surveyor. This survey is necessary to establish the groundwater gradient using either mean sea level (msl) or a common datum as a reference point. 50890.E01/ST05R358/1DZ:Iv Page 5 of 12 ®2005,Kleinfelder,Inc. April 29,2005