ARCHIVED REPORTS_XR0003145 - Laserfiche WebLink

Home Browse Search

Project No 034-97252 Page No 4 and recent years It is unlikely, therefore, that groundwater will rise to intercept the zone of higher concentration petroleum hydrocarbons in soil at depths of 10-20 feet bgs • We understand that no groundwater wells (domestic, municipal, or monitoring) are on the subject site Our scope did not include comprehensive identification of receptors in the area, however, it is unlikely that there are groundwater wells being used for domestic purposes in the near vicinity because public water supply is provided to the area • The former UST area is located approximately 100 feet from the nearest property boundary • The concentration ratio of benzene to xylenes in the groundwater sample ten years after UST removal suggests the following 1) biodegradation is not occurring at an optimal rate (due to possibly tight, oxygen poor soil), 2) the groundwater sample collected does not represent the core of the groundwater plume, but instead, it's periphery, or 3) a combination of not yet understood physical and biogeochemical conditions is controlling contaminant ratios Based on the above information and the presence of elevated concentrations of benzene and TPH-G, it is our opinion that regulatory site closure is not possible at this site until characterization of the lateral extent of soil and groundwater contamination is conducted This task could be completed by advancing approximately six Geoprobe soil borings at the site - four to collect groundwater samples near the property boundary (>80 feet from the former UST area), and two north and south of the UST area to complete characterization of the soil If the above scope of work proves that soil contamination is limited to the immediate vicinity of the former USTs and is comparable to concentrations previously noted, and if groundwater contamination does not extend beyond the property boundaries, it may be possible to get site closure as a low risk soil and groundwater case This possibility, and any scope of future work, should be discussed with the appropriate regulatory agency LIMITATIONS The conclusions presented above are based upon the agreed upon scope of work outlined in the above report Consultant makes no guarantees as to the accuracy of completeness of information obtained from others It is possible that information exists beyond the scope of this investigation Additional information which was not available to Consultant at the time of writing the Report may . result in a modification of the conclusions and presented The Services performed by Consultant have KRAZAN& ASSOCIATES, INC Offices Serving the Western United States 3497252 GWl