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Mr. Don O. Culbertson _ roject 2560-203.01 August 14, 1995 Page 2 Geoprobe sampling should be performed using a four-foot sampling tube inside the rod in order to obtain continuous cores for logging purposes. All geoprobe borings will be continuously cored. A deep Geoprobe boring should be installed in Area 4 to evaluate the extent of petroleum hydrocarbons in the soil below the water table. The work plan states: "One boring completed next to Area 4 will be advanced to a sufficient depth to define the vertical extent of petroleum-hydrocarbon impacted soils as identified by examination with field instrumentation and visual inspection, or to the extent of the rig's capability." Where petroleum hydrocarbons are indicated. all geoprobe samples should be analyzed for total purgeable petroleum hydrocarbons (TPPH) by EPA Method 8015 modified, and total recoverable petroleum hydrocarbons (TRPH) by EPA Method 418.1. in addition to the tests proposed. The sampling protocol should also be revised to include EPA Method 8270 for analyzing for PNAs where it appears that EPA Method 8310 may not be giving accurate results. In general, EMCON feels that the analyses proposed in the work plan (EPA 8015m, EPA 8310, and BTEX) will characterize the nature and extent of impacted soils and groundwater. High concentrations of petroleum hydrocarbons can influence results for both EPA 8270 and 8310 methods, although method 8270 is less affected. EMCON proposes that either EPA method 8270 (PNA specific) or EPA method 8310 be chosen during field activities based on visual inspection and examination with a flame ionization detector. If highly-impacted soils are encountered during field activities, EPA method 8270 (PNA specific)will be selected for analysis of these samples. Analysis of the soils and water for total extractable petroleum hydrocarbons as crude by EPA method 8015m will both identify and quantify the petroleum hydrocarbons present in a sample. EPA method 418.1, on the other hand, is a non-specific, qualitative analysis. Therefore, EMCON feels that EPA method 418.1 would be redundant and would provide less accurate results than those obtained from EPA method 8015m. The soil boring to be converted to a monitoring well closest to Area 4 should be continuously cored. Coring and sampling should extend below the water table to the bottom of the boring as with the deep Geoprobe boring in Area 4. During monitoring well installation, EMCON will continuously core the boring completed next to Area 4. The boring will be continuously cored from approximately 5 feet below grade to the bottom of the boring. BOK A21 SADDN.DOC-94\gtf:1