FIELD DOCUMENTS_FILE 2 - Laserfiche WebLink

Home Browse Search

`r FORMER AMERICAN FOREST PRODUCTS "4.0 SLI Conditions and Remediation Closure Summary Report July 2009 URS Project 17322736 Page 4-1 4.0 SOIL CONDITIONS AND REMEDIATION This section summarizes corrective actions taken for.contarhmated soils at the site. The corrective actions were proposed in a feasibility study prepared by Dames &Moore(Dames &Moore, 1988)and carried out in 1990 and 1991 (Dames&Moore, 1994). Residual soil conditions and hydrocarbon mass prior to and following remediation are also presented. r 4.1 SOIL CORRECTIVE ACTIONS- Following demolition of the former maintenance shop building approximately 2,000.cubic yards of soil were removed from t o xcavations. Soil was removed from the vicinity of the former.500-gallon waste �\poil UST at the east end of the maintenance shop and the former 10,000-gallon UST at the west end of the .t6 building. Soil was removed until confirmation sampling indicated that the remedial goal of 10,000 mg/kg 1[�C of TPH-diesel(TPHd)was achieved.This required an excavation to a depth of 26 feet below ground surface at the east end of the building, and 22 feet below ground surface at the west end. Excavated soils with concentrations exceeding 100 mg/kg of TPHd were treated in an on-site biotreatment cell. The excavated soil,which amounted to approximately 2 50 yards, was treated until concentrations had declined sufficiently to meet the requirements for off-site disposal in a Class H Landfill.The excavation pits were backfilled with approximately 2,000 cubic yards of imported clean fill and 150 cubic yards of excavated soils with TPHd concentrations of less than 100 mg/kg. The backfill was compacted in lifts and capped with four inches of asphaltic concrete. Seams with existing pavement were capped with a one-inch asphalt.overlay. In June 1991 ant857foot=long-product-line extending from a former pump island to the former 10,000-gallon diesel tank was removed. Soils along the route of the product line, which had been buried approximately 18 inches below ground surface,were excavated to a depth of 5 feet. Confirmation samples collected following the excavation were non-detect for TPHd and BTEX. The 150 cubic yards of excavated soil were treated off-site by thermal oxidation. The trench was backfilled with pea gravel and y AB aggregate,then paved with 6 inches of asphalt. 4.2 RESIDUAL SOIL CONTAMINATION The 2001 NFAR report prepared by URS(URS, 200 1)presented tables of soil analytical data, cross �� sections, and a map of soil sampling locations. Those data are presented in Appendix E.According to the 2001 NFAR report, review of soil analytical data indicated;TP-Hd concentrations are at depths o0 6,tox t30=feet bgs=in the vicinity of the former USTs. This is where TPHd has been reported at a maximum concentration of 23,000 mg/kg at a depth of 22 feet in the vicinity of the former waste oil UST at the east end of the former maintenance shop.That report* also observed that TPHdconcentrati s decreased by�"" gone-tto-two_ofd&§of.iH gnii d& etween 20 to-30 feet.bg,, and below36 feet-bgs•TPHd-was-ahnost----- ,entirely absent::His;F ncallYFgToundwater..levels have xemained-consisteritly-below the 30 foot bgs limit of .~3 5 significant soil contamination(Figure 5). Observations of decreasing soil concentrations with depth were supported by the data collected during the installation of monitoring wells DMW-10 through DMW-14 (URS, 2008). Sample data collected from the boring for DMW-14 indicated TPHd at a concentration to 1.4 mg/kg in a sample collected from 35 feet bgs, and below detection in a sample collected from 95 feet bgs (URS, 2008). No detection of 1,2-DCA or K:SW oc \227351Ame i=For tlCl wm-S�m PQ ary-Rcpon-RevOl.doc u }