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DE PAXIMIS l a 1 3 ' 9 5 No. 015 P. 0 MEMORANDUM TO: Jack McBurney (He maximis) C: Paul Ryan (Texaco) FROM: Thomas V. Danahy, Daniel Nachman DATE; January 12, 1995 SUBJECT: Selection of Soil Standards or Background Values for Metals, Tutu Wells Site, St. Thomas, U.S. Virgin Islands As discussed in our telephone conversation today, Geraghty & Miller, Inc. would like to have concurrence from Tutu Environmental Investigation Committee (TEIC) and the U.S. Environmental Protection Agency (USEPA) on the selection of metal soil standards for the Final Remedial Investigation (RI) Report. As you know, in the draft RI we used 10 times the maximum background metal concentration to screen soil values. In USEPA's comments (dated December 28,1994) on the Draft RI, General Comment 2 stated that New York State Technical and Administrative Guidance Memorandum (NYS TAGM) should be used as TBCs to determine soil impact. Piewe have the USEPA define the abbreviation "IbCs". The NYS ?AGM levels provided by USBPA provide a soil value for only one inorganic (metal) parameter (arsenic - 7,500 ug/kg or site background). The NYS TAGM metal levels are derived from background values for soils in the eastern United States or New York State. These values are not useful as background soil values in St. Thomas. According to the NYS TAGM, site-specific background values are to be used if available. On Page 9 of USEPA's comments, a specific comment for Page 5-3 states the "two times rule" Should be used to identify chemicals of concern. The USEPA comments explained "if the mean of the site data exceeds two times the mean of the background data, then the element should be included as a chemical of concern." As a reminder, the soil levels provided by USEPA were intended to address the potential impact to groundwater pathways (which was not evaluated by the baseline risk assessment). TM USEPA comments also provided soil risk-based preliminary remedial goals (PRGs) for ingestion and inhalation pathways for manganese in residential (1,360 mg/kg) and commercial/industrial (9,500 mg/kg) areas. TUT 006 0490 *64608* 64608 DE MR^IMIS ———— , Jan io,y5 11 :io No .015 F.03 im, Geraghty & Miller believes it is Important to Clarify the metals soil standards with the USEPA to avoid revision and re-submittal of the Final Rl report. We believe the soil standards requested by the USEPA (2x the average background value) listed in Table 1 are inappropriate as indicated by the exceedence of these values at several properties, including non-source and likely non-impacted areas, (i.e., churches and parking lots). It should be noted that 2x the average value often is approximately equal to the maximum background concentration. The use of the 2x the average value results in identifying many metals, most or all of which are naturally occurring, as chemicals of concern. It is our opinion that all of the meial concentrations detected are due to natural variations in metal concentrations in soil. The NYS TAOM values were designated by USEPA to be used as soil standards for organic contaminants that may potentially impact groundwater above drinking water standards. Because metals adsorb onto soils and very little migration to groundwater occurs (as evidenced by low groundwater metal concentrations), the evaluation of the impact to groundwater pathway from metals in soils is not necessary. The more likely exposure pathway for metals in soil is through ingestion and inhalation of airborne soil (dust). These pathways were evaluated on a site-specific basis by the USEPA in the Draft Endangerment Assessment. Geraghty & Miller believes metal soil concentrations identified as a concern based on risk assessment should be discussed in the Rl. Section 7.0 of the Final Rl Report was intended to be a summary of USEPA's risk assessment. If the final risk assessment (or at least the final risk assessment standards) are not provided by the USEPA by January 18th, we recommend the deletion of Section 7.0. (This would not allow for discussion of chemicals of concern based on the risk assessment). TUT O06 049.1 DL Jan 13,95 11 :1S N o . 0 1 5 P .04 OJ u nii.i.i-i\ Using theUSEPA recommended standards (2x above average background) the following properties exceed these values. Property Metals Present Greater than 2x Avg. Background Lead, zinc, arsenic Arsenic, lead, zinc, copper, chromium, silver, potassium Lead, potassium, zinc, barium, sodium Arsenic and potassium . barium, copper, potassium, silver, zinc, VIHA Curriculum Center Ramsay Texaco Illicit Four Winds Plaza Western Auto Vitclco Esso Tutu God of Holiness Assembly of God Lutheran Church O'Henry The metals underlined above are present at concentrations above 5 times the maximum background value. These standards (5x maximum background) provide a more realistic comparison and several of the non-suspect properties are eliminated. lead Arsenic, barium, lead, manganese, potassium Lead, sodium, arsenic, zinc, barium, potassium Potassium Arsenic Potassium Sodium Barium, copper, potassium, sodium Bariumr manganese, potassium, zinc, I'VifXCjtciVtui'^piOOtS .094\eorre»pU>10995 . TUT OOfc 0492 I & ••a 5I E 5 i. 8 w £ * 3! 8 .- § C w - * 0 *h A p <», £J . •—• ^ • ov ~2 3 15 3p f> f{ /QqnRnfiin? 'nw M'PITIU 9 T 0 ' ON 6 T : T T S6 ' 2 T UP f DE UtKHliHIY & niLLtK JNU Jan 13,95 11 :i9 NO .015 F . O t NU. ^ujyuyubb/ r, UD Table 4-12. Maximum Natural Concentrations of MeUls and Cyanide in Background Soil Sample*. Tutu Service Sution Investigation, St Thomas, U.S. Virgin Component Na.tne AJumijiu • Antimony Amaic Barium Calcium Chrorgiuo) Cobalt Copper Cyanide, Tout Iron UMU) Magnesium Manganese Nickel Potassluol Silver Sodium Vanadium Zinc Sample ID B-7 (2 to 4 feet) SS-8 B-7 (2 to 4 feet) SS-1 SS-8 B-7 (2 to 4 feet) SS-1 B-7 (2 to 4 feel) SS-1 B-7(2to4feet) B-7 (2 to 4 feet) B-7(2to4fot) SS-8 SS-1 SS-2 SS-2 B-7 (2 to 4 feet) SS-1 B-7 a to 4 fed) Results (tng/kg) 2*400 14.7 1 41.9 144000 28.6 23.7 73.1 1.2 35400 19.8 21500 888 18.9 568 0.99 561 109 62.4 SX" Klfoo *3vS £ >c^. £ •fa.0,000 v*\i vt6.$ ^*.5 ^ j (CAk£ex> H*\Ao *^-5 *6*to U 6 C %fto5 54S 111. Background ssotplas weio collected from four locations SS-1, SS-2, S3 8, and tt-v ^ m * ID Id«iUfic«Uoci. Milligram* per kilogram (p»rte per mJUion [ppm]). TUT (")O6 O494