Laserfiche WebLink
V41pe -mW <br /> Mr . Ted Knowles <br /> 202/799-5027 <br /> February 17 , 1988 <br /> Page 2 <br /> than the ones previously reported from the initial sampling dated <br /> October 1 , 1987 . Even though these values have decreased , the <br /> benzene concentrations in groundwater are still above the state <br /> of California, Department of Health Services action levels of . 7 <br /> ppb . As a result of this , GTI recommends that additional work be <br /> performed on site in order to determine the source of groundwater <br /> contamination. This would include the following : <br /> 1 . The drilling of one deep soil boring in the middle of <br /> the old tank pit . <br /> 2 . Multiple shallow hand auger borings in the vicinity of <br /> the old product lines and pump islands . <br /> 3 . Survey well head elevations to an arbitrary datum in <br /> order to help determine the local groundwater gradient . <br /> 4 . Implementation of a monthly groundwater monitoring and <br /> quarterly sampling program . <br /> Drilling of one deep soil boring in the middle of the old tank <br /> pit is to determine the presence or absence of any soil <br /> contamination. Soil samples from this boring will be taken at 5- <br /> foot intervals with selected samples submitted for laboratory <br /> analysis . <br /> The multiple shallow hand auger borings in the vicinity of the <br /> old product lines and pump islands are to determine the possible <br /> source areas of contamination. Soil samples from the appropriate <br /> borings will , in addition, be submitted for laboratory analysis . <br /> Surveying the elevations of the 3 existing monitoring wells would <br /> allow for the determination the direction of the local <br /> groundwater gradient . This would allow GTI to better determine a <br /> possible source area and the estimated direction of the <br /> contamination migration . <br /> The implementation of a monthly groundwater monitoring and <br /> quarterly sampling program is in order to observe how hydrocarbon <br /> concentrations are affected by the fluctuation of groundwater <br /> levels through time . <br /> The proposed soil boring and hand auger borings should reveal <br /> valuable information w:.th regard to defining the presence or <br /> absence of on-site so.ii. contamination . It is GTI ' s opinion that <br />