SU0006799_SSCRPT - Laserfiche WebLink

Home Browse Search

i r values for 4 , 4•-L)DL-; and 4 ,4-DDT. The sample from the 3 ' depth contained only 4 , 4-DDT in excess of the DL. F-H samples coI lis t.ed from borehole BG exhibited concentrations of both 4 , 4-ODD arid 4 , 4-DDT in excess of the comparison standards �- while only the 31 depth sample from borehole BH exhibited a 4 , 4-DDT level in excess of the DL. Inter retarir)n of Water Sample Results Ar. summarized on 'fable 2 , only water samples collected from monitoring well T VJ 31 contained detectable concentrations of compounds. "Well_ MW4" was the blind duplicate of MW3 submitted to the laboratory as a Iual.it.y control sample. Agreement between they primary and duplicate analyses was excellent. The monitor well sample results indicate there has been only a minor impact on the groundwater beneaththe site by a. agricultur- al chemicals used at the site. No concentrations .found exceed currently adopted Primary or Secondary Drinking Water Standards. h ., o Summary The site invest.i.gat ion 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, cons.isting primarily of organochlorine pesticides, 4 , 4--DDT, 4 , 4-DU)E and 4 , 4-DUD, appear to be primarily isolated to the tapper most 3 ` of the site soils. Pegarding groundwater quality, several of the compounds detected _ within the sukjst.irl:ace so'_is were also detected within the shallow gr_oi3ndwater, iioweve.r, 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 . ct Re�somToextc;ia _ictrt Since the soils at the site are predominantly fine textured and :Laterally continuous and that groundwater yield. is very limited, it appears that the site soils have low permeability and t.r.ansmissivity . These hydrogeologic conditions, coupled with the j{!)own very low mobi-lity of the organochlorine pesticide compounds �- found in the soil , suggest that migration of the compounds through the soils is unlikely. .. Since the pesrlicide 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 -