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- 11,11 1 1 M 11 112 -_ April 24,1989 File No. 1705-2 As discussed above, the soil and water sampling techniques are based upon the guide. lines set forth by the California regional Water Quality Control Board (CRWQCB). These samples are later forwarded to a state approved analytical laboratory for total petro,eum hydrocarbons analyses and/or other laboratory analysis. A chain-of-custody record is maintained during travel to the lab and a copy of this record is attached in the evaluation study reports. Also, laboratory test results are included in the report with attachments of the analytical laboratory analysis. Groundwater Monitoring Well Installation All groundwater monitoring wells are installed according the CRWQCB. As stated earli- er, our office has simplified these guidelines into a flow chart for installing monitoring wells. The "Monitoring Well Flow Chart" is attached to this letter. This flow chart was designed to be used by personnel of this office only and should not be recommended for others to use. } The wells are drilled to at least 15 feet into the saturated layer or below the elevation of d encountered groundwater. If a day or impervious layer is encountered in the saturated zone, and if it is greater than 5 feet in thickness, drilling would stop and the well would 1 be backfilled grout to the top of the clay or impervious layer. The monitoring well is then constructed above the backfilled layer. Our monitoring wells are constructed with 2 inch I.D. PVC pipes with 0.02 inch slot perforated sections. The well screen is placed such that the screen length will accom- modate seasonal groundwater fluctuations and extended at least 5 feet above the Batu- rated zone. The annular space between the pipe and the wall of the boring is backfilled with #3 clean Monterey sand to about one foot above the top of the perforated section. A two to three foot bentonite plug is then placed over the sand pack to provide a.seal l against surface water infiltration. The remaining space is then backfilled with concrete. Screw-on or friction caps are usod to seal the bottom of wells. Currently, all well heads are secured with screw-on or locking caps, surrounded by a christy box. Monitoring well construction diagrams accompany the report in Appendix B. All wells are recorded with the Department o:Water Resources- "Water Well Drillers Report". These reports state the current owners name, location of well including a well location sketch,well construction,well tests, and subsurface soil descriptions. A copy of - _-- - ---------this reporris includedinour-office and field files, andwiththe drilling company. _... �. All monitoring wells are thoroughly developed to stabilize the sand pack surrounding the screen section of the well and to free the well of silt, sand and turbidity. The devel- opment of these wells are accomplished by using a teflon hand pump. Approximately, l._ A-2 I L