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values for 4 , 4--I:)DF, and 4 ,4-DDT. The sample from the 3 ' depth contained only 4 , 4-DDT in excess of the DL. All samples col-lected from borehole BG exhibited concentrations of both 4 , 4-DDD and 4 ,4-DDT in excess of the comparison standards while only the 3 ' depth sample from borehole BH exhibited a 4 , 4-DDT level in excess of the DL. 5 . 2 Interpretation of Water Sample Results As summarized on Table 2, only water samples collected from monitoring well TILti3 contained detectable concentrations of compounds. "Well MW4" was the blind duplicate of MW3 submitted to the laboratory as a quality control sample. Agreement between the primary and duplicate analyses was excellent. The monitor well sample results indicate there has been only a minor impact on the groundwater beneath the site by a agricultur- al chemicals used -at the site. No concentrations found exceed currently adopted. Primary or Secondary Drinking Water Standards. 6 . 0 Summary Th.e site investigation activities conducted at the Trinkle and Boys facility in Tracy, California indicates that limited pesti- cide residues are present above regulatory standards in the shallow subsurface soils but not in the groundwater. These residues, consisting primarily of organochlorine pesticides, 4 , 4- DDT, 4 , 4-DDE and 4 , 4-DDD, appear to be primarily isolated to the upper. most '; of the- site soils. Regarding groundwater quality, several of the compounds detected within the subsurface soils were also detected within the shallow groundwater. However, these compounds were observed only in trace concentrations. There are no Primary or Secondary Drinking Water Standards for a majority of these compounds. For those -compounds for which Primary and Secondary Drinking Water Stan- dards do exist , these standards were not exceeded. 7 . 0 Recommendations Since -the soils at the site are predominantly fine textured and laterally continuous and that groundwater yield is very limited, i it appears that the site soils have low permeability and transmissivity. These hydrogeologic conditions, coupled with the known very low mobility of the organochlorine pesticide compounds found in the soil , suggest that migration of the compounds through the soils is unlikely. Since the pesticide presence in excess of the TTLC within the soils appears to be limited in nature, and, in consideration of the site geology and hydrogeology, it is recommended that Trinkle and Boys initiate an annual sampling program at the three 9 -