ARCHIVED REPORTS XR0000055 - Laserfiche WebLink

Home Browse Search

1l Mr Martin Harris April 27, 2004 Page 3 of 7 utilizing a combination 25-ton CPT/hollow stem auger drill rig to collect discrete groundwater samples from potential water bearing zones (sandy soil) observed on the CPT log Groundwater samples were collected from boring SB4 within strata identified from CPT data using a Hydropunch° type groundwater-sampling tool To significantly decrease the chance for cross contamination from overlying impacted groundwater to occur, a temporary conductor casing was seated into a predominately clay confining bed identified from approximately 18 feet bgs to 21 feet bgs Groundwater samples were collected into 40-mL glass vials containing dilute hydrochloric acid preservative The containers were sealed, labeled, and immediately placed in an ice chest refrigerated to a temperature of approximately 4' Centigrade and transported to Argon under chain of custody protocol Analysis consisted of TPHg, BTEX, and oxygenated gasoline additives, including 1,2-DCA and EDB 2.5 Monitoring Well Installation On January 13, 2004, a combination 25-ton CPT/hollow stem auger drilling rig was used to advance borings MW5 and MW6 for the purpose of installing groundwater monitoring wells in the shallow water-bearing zone Due to surface obstructions, well MW7 was drilled and installed using a compact direct push rig on January 14, 2004 Based upon the lithology and depth to first groundwater (8-10 feet bgs) observed during drilling, wells MW5, MW6, and MW7 were completed to a depth of approximately 19 feet bgs, with the well screen from approximately 4 feet bgs to 19 feet bgs Wells MW5 and MW6 were constructed of 2-inch diameter, Schedule 40 PVC casing and 0 010-inch slotted screen Well MW7 was constructed of 3/4-inch diameter Schedule 40 PVC pre-packed screen with 0 010-inch slots The filter pack consisted of 16 5 feet of#3 silica sand The annular seal contained 2 feet of bentonite overlain by concrete, which was approved on site by Lori Duncan of EHD The wells were completed at the ground surface with traffic-rated, flush-mount well boxes Bonng/well construction logs are included in Attachment A Soil and wastewater generated during drilling activities was placed into DOT approved 55-gallon drums Both waste streams are currently stored on site pending disposal 2.6 Monitoring Well Survey As required by AB 2886, the wellhead elevations of the newly installed monitoring wells were surveyed by a Registered Surveyor to a horizontal accuracy of less than one meter and a vertical accuracy of 0 01 feet On January 21, 2004, Morrow Surveying surveyed the latitude and longitude of the site wells relative to the North American Datum (NAD83), and surveyed the wellhead elevations relative to San Joaquin County Benchmark No T1124 A site map showing monitoring well locations, latitude and longitude coordinates and wellhead elevations is included in Attachment B • Groondze/souza/reports/WELLRPTZb dae