SITE INFORMATION AND CORRESPONDENCE

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GEOMATRIX the sand filter pack, the remaining annular space was filled to about 1 foot bgs with a cement- bentonite grout mixture. The wells were completed above grade, capped with a locking waterproof expansion cap, and covered with locking "stovepipe"well covers. Monitoring well construction was implemented by Radian in accordance with SJC-EHD well standards and permit requirements. An SJC-EHD representative visited the site on July 21, 1998, and approved monitoring well construction. Boring logs and monitoring well construction details. as prepared by Radian, are provided in Appendix B. Each monitoring well was developed by Radian on July 27, 1998, using surging and bailing techniques to remove the fine-grained materials inside the filter pack and well casing,to consolidate the filter pack around the well screen, and to enhance hydraulic communication between the formation and the well. Three to five casing volumes of water were removed during development. Well development continued until the field water quality parameters and the clarity of the water stabilized. Well development logs as completed by Radian are presented in Appendix C. 3.3 SOIL BORING AND MONITORING WELL SURVEYING Soil boring and monitoring well locations were surveyed for horizontal and vertical control by, a licensed surveyor. Vertical control was based on the National Geodetic Vertical Datum of 1929, (NGVD29) and horizontal control surveyed relative to the North American Datum of 1983 (NAD83). 3.4 GROUNDWATER LEVEL MEASUREMENTS Groundwater levels were measured in all wells to identify the groundwater depth and elevation. Groundwater levels were measured prior to purging and sampling each well with an electronic water level sounder to the nearest 0.01 foot. In each well,the sounder was inspected for the presence of separate-phase petroleum. Table 2 presents the results of the groundwater level measurements. 3,5 GROUNDWATER SAMPLING Groundwater sampling was by Radian personnel on July 28, 1998, and by Geomatrix personnel on November 5, 1998. Groundwater samples were collected using disposable bailers and were transferred into laboratory-prepared containers, immediately placed in an ice chest for temporary storage, and transported to the laboratory via courier under chain-of-custody procedures. Quality assurance/quality control (QAJQC) samples, including blind duplicates and equipment blanks,were obtained during groundwater sampling. Ms131depWataUW_Safe\W00s 011451 HRA Rpt.doc 5