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r J.� TECHNICAL APPROACH SUMMARY �- The objectives of the proposed scope of work are to further investigate the extent of impacted soil and groundwater, establish a groundwater monitoring capability at the site, and survey possible sensitive receptors in the site vicinity. To achieve these objectives, three on-site groundwater monitoring wells will be installed and monitored and sampled on a quarterly basis for at least one year, and a survey of possible sensitive receptors within 2,000 feet of the site will be conducted. One of the proposed monitoring well soil borings will be continuously cored to delineate the subsurface soil sequence and to evaluate the vertical extent of impacted soil. This well will be located at the south end of the former UST in the vicinity of the previous Geoprobe soil boring B-2. Given that the regional groundwater flow direction is expected to be toward the north, the other two proposed monitoring wells will be positioned northeast and northwest of the former UST. The wells will be installed in 8-inch diameter soil borings drilled with a hollow stem auger drilling rig. The wells will consist of approximately 15 feet of two-inch diameter well screen. The wells will be surged and purged by the driller, following the placement of the sand pack and prior to the installation of the well seals. A licensed land surveyor will survey each of the newly-installed wellheads to the nearest 0.01 foot, referenced to a benchmark. During the drilling, undisturbed soil samples will be collected at 5-foot intervals using a modified California split-spoon sampler lined with sample sleeves. The soil samples collected at the 15, 20 and 25 feet below the parking area subgrade (25, 30 and 35 feet below street surface grade) will be analyzed for TPH-as-gasoline, BTEX, MTBE, DIPE, ETBE, TAME, and TBA by EPA Method 8260B. Additional soil samples may be submitted for analysis, if required to adequately characterize the site. Field observations and sample selection will be reviewed with the PHS/EHD inspector, prior to sample submittal to the lab. '- After the monitoring well seals have set, and then on a quarterly basis thereafter, the wells will be monitored and sampled. The lab will analyze each groundwater sample for TPH-as-gasoline, BTEX, MTBE, DIPE, ETBE, TAME, and TBA by EPA Method 82608. All waste soil generated during drilling will be contained in 55-gallon drums and temporarily stored at the site, pending analytical results and proper disposition. Equipment rinsate and purged groundwater will be contained in separate 55-gallon drums for temporary on-site storage, pending accumulation and proper disposition. A sensitive receptor survey within 2,000-feet of the site will include a review of water well completion reports at the state of California Department of Water Resources, contact with local and private water purveyors, and a tour of the site vicinity. The results of the well installation and sensitive receptor surrey will be documented in an environmental site investigation report. Each of the subsequent quarterly groundwater monitoring and sampling events will be documented in quarterly groundwater monitoring reports. ;.► All reports will be prepared and stamped by a state of California Registered Geologist and submitted to PHS/EHD and RWQCB. Given standard scheduling assumptions, the final project report could be submitted by the end of December 2001. 3 V r.r