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t 7.0 PHASE II SITE INVESTIGATION ..� As previously discussed, during the Phase I were used to evaluate the distribution of activities, four RECs were identified. The RECs impacted soil. Soil samples were collected at consisted of the presence of one former AST, two minimum 5-foot intervals and at lithologic �•+ existing ASTs, two former USTs, and three boundaries for lithologic description, volatile agricultural chemical mixing areas adjacent to organic compound (VOC) screening, and concrete "water boxes" at the site. Teichert potential laboratory (chemical) analysis. The requested that HLA perform a limited Phase II samples were collected using a 2.0-inch(inside site investigation to collect preliminary analytical diameter)California Modified split spoon sampler soil data to assess whether the four RECs had lined with three clean 6-inch long brass tubes. impacted site conditions. This first portion of the The sampler was driven with a 140-pound Phase II investigation consisted of a soil boring hammer. The number of blows required to drive adjacent to the former and existing ASTs, another the sampler each six-inch interval was recorded boring adjacent to the former USTs location, and and used as a qualitative measure of soil density. collection of a composite sample of the surficial soil at the three agricultural chemical mixing The lowermost tube from each sample interval areas. During sampling of the soil boring was removed from the sampler and immediately advanced at the former UST location on October capped with Teflon-lined plastic end caps, 21, 1996, evidence of impacted soil was labeled, and placed in an ice-chilled cooler for encountered(soil discoloration,petroleum transport to a State-certified analytical laboratory. hydrocarbon odors, and elevated PID readings). Samples were recorded on a standard HLA HLA communicated these preliminary findings to chain-of-custody form to document sample Teichert on October 24, 1996. On October 25, identification and handling. The remaining soil 1996,Teichert requested that HLA perform sample from each interval was checked for additional investigation of soil conditions at the hydrocarbon stains and monitored for VOC former UST to assess the lateral and vertical vapors using a photoionization detector(PID). extent of impacted soil, and estimate of the The PID was equipped with a 10.2 electron-volt volume of impacted soil. On November 4 and 5, lamp and calibrated on a daily basis to a 100 part 1996, the second portion of the Phase II per million(ppm) isobutylene standard. investigation consisted of advancing five additional soil borings and collection of The borings were logged by a California- additional soil samples. Work was conducted in registered geologist. The soils were visually accordance with the September 24, 1996 work classified using the Unified Soil Classification plan and the October 30, 1996 work plan System (USCS); soil classifications and other field addendum submitted to the SJCEHD. observations are recorded on standard HLA field logging forms. The soil borings were advanced 7.1 Field Investigation With conventional hollow stem augers by a CME 75 drill rig operated by Mitchell Drilling Environmental Corporation, a C-57 licensed y 7.1.1 Soil Borings and Soil Sampling driller, from Rancho Cordova, California. Drilling equipment was steam cleaned prior to each use. On October 21, 1996, one soil boring, Soil sampling equipment was washed in a immediately adjacent to the ASTs location and residue-free detergent (Alconox) and rinsed in tap one boring at the former USTs location, were water and deionized water prior to each use. advanced to a depth of 40 feet bgs. On November After drilling was completed, the borings were 4 and 5, 1996 five additional soil borings were be grouted with neat cement in accordance with advanced to variable depths of approximately 40 SJCEHD requirements. Soil cuttings generated feet bgs to assess the lateral and vertical during drilling activities were stockpiled on distribution of potentially impacted soil in the visqueen. The cuttings were retained on site 6W area proximal to the former UST location. The pending analytical results. boring locations were placed at variable distances from the former USTs, and the analytical data G:\WP\GDH\GH38371Z.151 Harding Lawson Associates 13 r