ARCHIVED REPORTS XR0010482 - Laserfiche WebLink

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depth of 40 feet in an attempt to define the extent of the remaining contamination. On October 4 & 5, 1990, 5 bore holes were drilled to 40 ' bgl under the direction of W. J. Hunter , R. G. , using Spectrum Exploration equipment - the locations of those boring are shown on Exhibit H. Split--spoon samples were taken at 1 ' , 5 ' , and every 5 ' to 40 feet , and were analyzed for BTEX & TPH-G. The results of those tests , shown on Table III , revealed that detectable amounts of Benzene, Toluene, & Ethylbenzene were present in Boreholes #1 , 2, & 5; Xylene was present only in #2. TPH-G was below detection levels in all borings. Utilizing the Environmental Fate worl-sheets from the LUFT Manual revealed that the levels of Benzene present exceeded the limits allowed to left in place - the other constituents present were below those limits. An analysis of the stratigraphy & lithology of the sediments penetrated by the borings showed that the chemicals are contained in a very sticky, plastic blue clay layer of extremely low permeability, and had not migrated into the underlying sands. For that reason, the geologist concluded that further work was not warranted, since it was extremely unlikely that the contaminants would be leached out of the clay into the water table. The staff of the County EHD did not concur with the report s analysis & conclusions. They stated that regardless of geological conditions, the level of contamination exceeded allowable limits as calculated by the LOFT manual worksheets , and a closure letter would not be issued. The staff did , however , state that no further remediation of the removed spoil was required. defer to Echibit l for a copy of that letter , dated March 2'e, 1991 . On June 13, 1991 , a meeting was held with staff members of the EHD to clarify the County 's position concerning site closure. The results of that meeting are summarized in correspondence from that office dated August 2, 1991 ; refer to E;,hibit J for details. As a result of that meeting , and a review of possible options for further investigative work , it appears that additional borings are the best method for determining the horizontal extent of the contamination - vertical limits have been established by prior work. A workplan to accomplish this required work is attached. PROPOSED WORKPLAN I . Move in Spectrum Exploration portable drilling rig equipped with 3 1l4" ID, (6" OD, ) flights & 1B" split--spoon sampler.