DRAFT REPORT
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SENSITIVITY
ANALYSIS FOR
REMEDIAL
RESPONSE AREAS
AND VOLUMES
Prepared for:Fields Brook PRP OrganizationAshtabula, OhioAugust 1995
Woodward-Clyde
30775 Bainbridge Road, Suite 200Solon, Ohio 44139
Project No: 86C3609S-10008
Woodward-ClydeEngineering & sciences applied to the earth & its environment
August 4, 199586C3609S
United States Environmental Protection AgencyRegion V (HSRM-6J)Ohio/Minnesota Remedial Branch77 West Jackson Blvd.Chicago, IL 60604-3590
Attention: Mr. Edward J. Hanlon
Subject: Sensitivity Analysis for Potential RemedialResponse Areas and VolumesFields Brook Floodplain/Wetland AreasAshtabula, Ohio
Dear Mr. Hanlon:
On behalf of Fields Brook PRP Organization (FBPRPO), Woodward-Clyde Consultants(WCC) has prepared a sensitivity analysis for the Fields Brook FWA. I have enclosed threecopies of this analysis. The intent of this submittal is to provide descriptions of potentialremedial response areas and volumes for various scenarios that have been discussed byUSEPA and the FBPRPO. The tables and figures respond to possible risk combinationdescribed in USEPA letter dated June 21, 1995. The information provided in this submittalwill be further described during the August 9, 1995, meeting with the USEPA.
If you have any questions, please do not hesitate to contact Mr. Joseph Heimbuch at(813) 365-8444 or me at (216) 349-2708.
Sincerely,
Martin L. Schmidt, Ph.D.Senior Consulting Professional
cc: L. Weyer (CH2M Hill)S. Golyeski (US ACE)R. Williams (OEPA)T. Wolfskill (WCC)J. Heimbuch (de maximis, inc.)C. McConnel, BechtelFBPRPO
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Woodward-Clyde
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SENSITIVITY ANALYSIS FORPOTENTIAL REMEDIAL RESPONSE AREAS AND VOLUMES
FLOODPLAIN/WETLANDS AREAFIELDS BROOK SITE, ASHTABULA, OHIO
Potential Cleanup Goals (CUGs) that have been developed to date for the Floodplain/WetlandAreas (FWAs) within the Fields Brook watershed vary depending on: the approach(deterministic vs. probabilistic); the exposure scenario (residential vs. occupational); and therisk target (10"5 vs. 10*6). Confidence Removal Goals (CRGs) have been developed for thecases in which the Upper Confidence Level (UCL) of the mean exceeds the CUG. TheCRGs can be compared to the existing data in order to estimate remedial response areas orvolumes. This sensitivity analysis, which has been prepared by Woodward-ClydeConsultants (WCC) on behalf of the Fields Brook PRP Organization (FBPRPO), includes adiscussion of the potential CRGs and a comparison of the estimated remedial response areasor volumes for various remedial alternatives within the Fields Brook FWA.
SUMMARY OF POTENTIAL CRGs
CRGs that have been developed for Floodplain Exposure Units (FEUs) 2, 3, 4, 6, and 8 areincluded in the attached Table 1. The CRGs were calculated by Gradient Corporation foreach FEU using both the Reasonable Maximum Exposure (RME) deterministic approach andthe Monte Carlo probabilistic approach. The CRGs were supplied to WCC by GradientCorporation in facsimile memoranda dated July 24 and July 27, 1995.
Potential CRGs for polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) havebeen developed for all five FEUs. Potentials CRGs for beryllium have also been developedfor FEUs 2, 4, and 6 using the deterministic approach under the residential exposurescenario at the 10^ risk target. The various CRG exposure scenarios and risk targetsincluded in Table 1 for the five FEUs are summarized as follows:
• Residential exposure scenario and 10"6 risk target for FEUs 2 and 3
• Occupational and residential exposure scenarios at both the 10~5 and 10^ risk
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targets for FEUs 4 and 6 (The various sets of CRGs calculated for FEUs 4and 6 are intended to address all potential combinations described by EdHanlon in USEPA's letter dated June 21, 1995)
• Occupational exposure scenario at the 10~5 and 10"6 risk targets for FEU 8
SUMMARY OF POTENTIAL REMEDIAL RESPONSE AREAS AND VOLUMES
Estimated remedial response areas and volumes that were calculated based on the variouspotential CRG values are included in Table 1. The estimated remedial response areas areshown in square feet. The response areas were established using isoconcentration contourlines, which were developed for each FEU based on existing FWA surface soil analyticaldata. The area estimates include an additional 10 percent to allow for straightening of thepotential response area boundaries. The estimated in-place volumes are listed in cubic yardsand assume a total excavation depth of 12 inches within the potential response areas.
The estimated remedial response areas are shown graphically in Figures 1 through 6 for thefollowing approaches, exposure scenarios, and risk targets:
• FEU 2 - deterministic and probabilistic; residential; 10"6
• FEU 3 - deterministic and probabilistic; residential; 10"6
• FEU 4 - deterministic; occupational; 10"6
• FEU 6 - deterministic; occupational; 10"6
• FEU 8 - deterministic; occupational; 10"6
POTENTIAL REMEDIAL RESPONSE AREAS AND VOLUMES BY ALTERNATIVE
The Draft Alternatives Array Memorandum provided to USEPA by WCC with a letter datedMay 15, 1995 included a discussion of six potential remedial alternatives for the FWAswithin the Fields Brook watershed. The six remedial alternatives, which were originallysummarized in an April 28, 1995 letter provided to the USEPA by Joseph Heimbuch of demaximis, inc., are as follows:
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• No Action• Containment #1 (Cover)• Cover, Excavation, Backfilling, and Ex-Situ Disposal• Containment #2 (Cover)• Excavation, Backfilling, and Ex-Situ Disposal• Excavation, Backfilling, Treatment, and Ex-Situ Disposal
An up-to-date summary of the six remedial alternatives that are considered for the FWA ispresented in Table 2. Potential remedial response areas and volumes that are associated witheach alternative are presented in Table 3 and summarized in the following subsections.
Alternative I - No Action
No remedial action is being considered in the no action alternative. Thus, the potentialremedial response areas and volumes would be zero for all cases.
Alternative II - Containment #1 (Cover)
The Containment #1 alternative generally involves constructing a soil cover in the designatedremedial response areas for all five FEUs. A risk target of 10"6 would be used for FEU 2and 3 and a risk target of 10"5 would be used for FEU 4, 6, and 8. The potential remedialresponse areas vary from 338,140 to 660,850 square feet.
Alternative HI * Cover, Excavation, Backfilling, and Ex-Situ Disposal
This alternative involves the use of a revegetated soil cover in FEUs 3, 4, 6, and 8, withexcavation, backfilling, and ex-situ disposal for FEU 2. The excavated soil would bedisposed of in an off-site landfill. A risk target of 10^ would be used for FEU 2 and 3 anda risk target of 10'5 would be used for FEU 4, 6, and 8. The potential remedial responseareas vary from 113,520 to 427,870 square feet. The potential in-place volumes to beexcavated range from 8,320 to 8,630 cubic yards.
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Alternative IV - Containment #2 (Cover)
Components of the Containment #2 alternative are the same as those for Containment #1.However, Containment #2 considers a 10"6 risk target for all five FEUs. The potentialremedial response areas vary from 551,500 to 943,690 square feet. This alternative doesnot consider soil excavation.
Alternative V - Excavation, Backfilling, and Ex-Situ Disposal
This alternative involves excavation of soil with chemical concentrations that exceed theCRGs to a depth of 12 inches, backfilling, and placement of a revegetated cover to originalgrade. The excavated soil would be disposed in an off-site landfill. A risk target of 10"6
would be used for all five FEUs. The potential in-place volumes to be excavated range from18,940 to 34,950 cubic yards.
Alternative VI - Excavation, Backfilling, Treatment, and Ex-Situ Disposal
This alternative also involves excavation of soil with chemical concentrations that exceed theCRGs to a depth of 12 inches, backfilling, and placement of a revegetated cover to originalgrade. However, the excavated soil exceeding 500 parts per million (ppm) would bethermally treated prior to off-site landfilling. A risk target of 10"6 would be used for all fiveFEUs. The potential in-place volumes to be excavated are the same as those listed for theprevious alternative and range from 18,940 to 34,950 cubic yards.
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tPA OCTERMNtSTIC. RESIDENTIAL. IE-06RCUEMAI RESPONSE AREA = 233.000 SO FT.
FBPRPO PRO8AMUSTIC. RESIDENTIAL. IE-O6RCUCDUL RESPONSE AREA = 225,000 SO FT.
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