COMPLIANCE INFO_PRE 2019 - Laserfiche WebLink

Home Browse Search

Aqua Terra TechfioEogies INTRODUCTION Aqua Terra Technologies was retained by Cal-Trans.. in accordance with the conditions of our proposal dated May 19, 1986, to determine potential contamination of subsurface soil and groundwater from a site where a leaking underground gasoline storage tank was excavated. The former tank site is located near the intersection of the Crosstown Freeway and the Southern Pacific Railroad in Stockton, California. FIELD INVESTIGATION Construction and Soil Sampling The test boring was drilled on May 20, 1986, using 11-inch diameter, hollow stem auger, truck mounted drilling equipment. The boring was drilled to a depth of 55 feet below grade. our field geologist observed drilling operations and prepared a detailed log of materials encountered. The boring log is presented in Appendix 1. Soil samples dere collected for chemical analysis at approximately five foot intervals beginning at five feet below grade and continuing to a depth of 29 feet. Soil samples were collected using 2 .5-inch diameter brass liners in a modified California drive sampler. Teflon sheeting was placed between the liner caps and the soil samples; the caps were sealed with PVC tape, and the tubes were labeled. The soil samples were immediately placed on ice. The soil sampler, soil sample tubes, and drill rods and augers were steam cleaned prior to their initial use. The soil sampler was steam cleaned between each subsequent use to j_ reduce the likelihood of cross contamination between samples. The boring was completed as a groundwater monitoring well in accordance with the requirements specified in the California Administrative Code, Title 23 , Chapter 3 , Subchapter 16 . Prior to installation, a well permit was obtained and filed with the San Joaquin Health Department. c, The well consisted of four-inch diameter, Schedule 40 PVC pipe extending 53 feet below the ground surface. The lower one foot of the well consisted of unslotted pipe. The slotted section of the well extended 25 feet above the unslotted pipe, and was situated about six feet above the local groundwater level measured at the time of drilling. Pipe slots were machine slotted with 0. 02-inch openings. The upper portion of the well consisted of unslotted pipe. Pipe sections were joined by flush threads; no PVC glue was used. The annular space around the screened section was backfilled 1