ARCHIVED REPORTS_XR0010339 - Laserfiche WebLink

Home Browse Search

18 November 1996 AGE-NC-Project No 95-0134 ' Page 6 of 8 initially run using the masses of toluene, ethylbenzene and xylenes for ground water at depths of 40 and 50 feet and using the mass of TPH-g with ground water at depths of 40 feet and 50 feet Benzene was not detected in any of the soil samples analyzed Therefore, benzene was not used in the modeling When all parameters were entered using the best available data, SESOIL predicted that no contaminants would impact ground water for the first four models A request was made to examine the potential impact to ground water, if ground water were to return to the 1986 seasonal high of 35 feet Approximately five feet of impacted soil would be in contact with ground water The volume of hydrocarbons was calculated for impacted soils below a depth of 35 feet The total volumes of toluene, ethylbenzene and xylenes were defined as a release to ground water over the area of impacted soils for the fifth model A degradation rate of zero was used for the fifth model The concentrations of contaminants in ground water at the down-gradient edge of the Irelease was predicted using the AT123D A sixth model was run using the degradation rates from an example model supplied in the SESOIL program For the fifth and sixth models, the predicted concentrations for ethylbenzene, toluene and xylenes would be below the state drinking water standards of 680, 100, and 1,750 ppb, respectively Using degradation rates, concentrations would decrease more rapidly Ethylbenzene, toluene and xylenes would decrease to below laboratory detection limits after 4 years, 3 years and 9 years, respectively for the sixth model The seventh model was run using the volume of TPH-g below a depth of 35 feet as a release to ground water with a receptor well at the down-gradient edge of the release The eighth model was run using the data from model seven and placing the receptor well 10 feet down-gradient The SESOIL modeling was described in the Quarterly Reports for May 1995, September 1995 and September 1995 Addendum, prepared by AGE SESOIL input data and output graphs are included as Appendix B 27 WELL SURVEY In accordance with requirements for site closure of underground tank sites, a survey was conducted to locate ground water receptors within two thousand feet of the subject site Lists identifying municipal wells in the Stockton area were obtained from the California Water Service Company ' (CalWater) and the City of Stockton Municipal Utilities Department One well was identified to be within the search radius Well No 28-01,maintained by CalWater, is located at the northwest corner of Fremont Street and Sierra Nevada Street, approximately 1,100 feet south of the subject site I CalWater Well No 53-01 is located approximately 2,200 feet southwest of the site No surface water features are located within the search radius Municipal well locations are shown on Figure 7