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HomeMy WebLinkAbout10036_South End Transit_Southline VI Risk Evaluation Rpt Final 03-04-13-OCR    March 4, Mr. Tony NC Divis Brownfi 1646 Ma Raleigh, RE: V T 14 C A B Dear Mr. ATC As vapor int informati evaluatio 1.0 Back The site i Brownfie apartmen with a va barrier w the vapo following Service o In Septem 100 feet (IHSB) V was cond dated Ap results o Building with spli slabs). , 2013 y Duque sion of Was elds Progra ail Service C North Carol Vapor Intrus Transit-Orien 40 Remount Charlotte, Me ATC Project Brownfields P . Duque: sociates of trusion risk ion, risk calc on. kground Inf is a portion o elds Program nt buildings apor mitigat with underlyi or barrier d g constructi of the Brown mber 2012, P of groundw Vapor Intrus ducted in ac pril 18, 201 f the sampl 17 Upper, B it foundation ste Managem am enter, Room lina 27699-1 sion Risk E nted, Multi-F t Road ecklenburg C No. 089.433 Project No. North Carol evaluation f culations, co formation of a larger 2 m due to a h were recent tion system ng piping fo during the b ion. The d nfields Progr PSI perform ater impacts sion Screeni ccordance w 2, filed with ling indicate Building 18 n slabs and ment m 3409-K 1646 valuation Family Resid County, Nort 337.1724 10036-06-60 lina, P.C. (A for the above onclusions, a 22.41 acre pa historical rel ly construct consisting o or passive ve building con design of th ram of DEN med sampling s exceeding ing Levels ( with a Post h and appro ed exceeden Upper, and the upper a dential Proje th Carolina 0 ATC), on be e referenced and recomme arcel of land ease of chlo ed on the pr of a sealed h enting. Sub- nstruction to e vapor mi R in Novem g of sub-slab the North C (VISLs) for Construction oved by the nces of IHSB Building 18 and lower de N.C ect, Southline ehalf of JLB d site. This endations ba d that was en orinated solv roperty. Th high density -slab sample o facilitate itigation sys mber 2011. b soil gas in Carolina Inac residential n Sub-slab e Brownfield B VISLs fo 8 Lower (the esignations r www C. Engineering e Apartment B Partners, submittal de ased on the r ntered into th vents. A ser he buildings polyethylen tubing was sub-slab so stem was ap each buildin ctive Hazard groundwater Vapor Samp ds Program or residentia ese building refer to the Tel: 919-871 Fax: 919-871 w.atcassociate g License No. C ts has comple etails backgr results of the he North Car ries of reside were constru ne (HDPE) v installed ben oil gas sam pproved by ng located w dous Sites Br r. The sam pling Work of DENR. al soil gas b gs are constru upper and l 1-0999 1-0335 es.com C-1598 eted a round e risk rolina ential ucted vapor neath mpling Will within ranch mpling Plan The below ucted lower Vapor Intrusion Risk Evaluation Page 2 Transit-Oriented, Multi-Family Residential Project, Southline Apartments March 4, 2013   Based on these exceedences, PSI returned to the site in December 2012 to collect additional samples at the locations showing exceedences. The results of the December 2012 sampling indicated exceedences only in the sample collected at the Building 18 Lower location. In the event of exceedences of IHSB VISLs for individual constituents, the Brownfields Program Vapor Intrusion Guidelines (March 2012) specify that additional risk calculations can be performed to further evaluate the data. ATC was contracted to perform additional risk calculations, as detailed in this submittal. The primary goal of the calculations was to determine whether the sub-slab soil gas data poses a sufficient risk to require active venting or additional sampling to confirm the vapor mitigation system performance. 2.0 Risk Calculation Procedures ATC performed calculations to evaluate the cumulative risk for the combined constituents of concern for each sample showing exceedences of IHSB VISLs for residential soil gas for individual constituents. The samples included Building 17 Upper, Building 18 Upper, and Building 18 Lower collected in September 2012, as well as Building 18 Lower collected in December 2012. Per the process specified in the Brownfields Program Vapor Intrusion Guidelines (March 2012), ATC initially calculated the predicted indoor air concentration by multiplying the sub-slab concentrations by a sub-slab to indoor air attenuation factor of 0.1 (1/10). ATC then calculated the cumulative carcinogenic risk and hazard index based on the predicted indoor air concentrations. Chloroform was removed from the cumulative risk calculation since the Brownfields Program previously concurred that detection of this constituent was associated with city water rather than vapor intrusion. Note that ATC considers it likely that additional detected constituents are also associated with sources other than vapor intrusion. However, inclusion of these constituents does not significantly impact the cumulative risk results. Therefore, all detected constituents except for chloroform were included in the cumulative risk evaluation. 3.0 Risk Evaluation Results The Brownfields Program requires mitigation for sites showing repeated exceedences of a carcinogenic risk limit of 10-4 and hazard index limit of 1. The results of the risk calculations for the subject site indicated no exceedences of carcinogenic risk limit of 10-4. Calculated hazard index values were below the limit of 1 for all samples except the Building 18 Lower sample collected in September 2012, which indicated a hazard index of 1.06. The risk calculations are included in Attachment 1. ATC does not consider the hazard index value for the Building 18 Lower sample to represent a significant risk based on several lines of evidence. First, the risk calculations performed by ATC were based on an extremely conservative sub-slab to indoor air attenuation factor of 0.1 (1/10). If an attenuation factor of 0.094 (1/10.6) is applied, the calculated risk for the September 2012 Building 18 Lower sample would drop below the hazard index limit of 1. ATC considers it likely that the actual attenuation factor at the subject site is substantially less than 0.094 based on both published references and the building construction, as further discussed below. Vapor Intrusion Risk Evaluation Page 3 Transit-Oriented, Multi-Family Residential Project, Southline Apartments March 4, 2013   The Environmental Protection Agency (EPA) originally recommended an attenuation factor of 0.1 (1/10) in their 2002 OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils. However, additional data collected over the past 10 years suggest that a lower attenuation factor is appropriate for even the most conservative assessment (note that a lower attenuation factor represents less vapor intrusion through the slab). The EPA released a report entitled EPA’s Vapor Intrusion Database: Evaluation and Characterization of Attenuation Factors for Chlorinated Volatile Organic Compounds and Residential Buildings on March 16, 2012. Based on an EPA database of over 400 samples, this report calculated a median sub-slab soil gas attenuation factor of 0.003 (1/333), and the 95th percentile was found to be 0.03 (1/33). The EPA is currently preparing an updated vapor intrusion guidance document which has not yet been released. However, the draft guidance reportedly recommends an attenuation factor of 0.03 (1/33). Other regulatory programs and states are using even lower attenuation factors on the order of 0.01 (1/100). These data clearly show that the calculated passing attenuation factor of 0.094 (1/10.6) for the subject site is very conservative. Furthermore, the building at the subject site is constructed with a vapor barrier and passive venting system, as well as a newly installed concrete slab. A building with this construction is expected to have a slab attenuation factor which is many orders of magnitude higher than the most conservative EPA recommendations. Based on the building construction, ATC considers it extremely unlikely that indoor air concentrations exceed applicable risk levels due to vapor intrusion. Lastly, the Brownfields Vapor Intrusion Guidelines specifically state that mitigation is required if sampling shows “repeated” exceedences of the hazard index limit of 1. At the Building 18 Lower location, samples were collected on two occasions in September 2012 and December 2012. The September 2012 sample indicated a hazard index of 1.06, which only slightly exceeds the limit of 1. The December 2012 sample indicated a hazard index of 0.524, which is significantly below the limit of 1. The data do not show “repeated” exceedences, and therefore mitigation does not appear to be required. 4.0 Conclusions and Recommendations ATC has completed a vapor intrusion risk evaluation for the Southline Apartments site in Charlotte, North Carolina. Previous sub-slab soil gas sampling indicated exceedences of IHSB VISLs for residential soil gas at three locations (Building 17 Upper, Building 18 Upper, and Building 18 Lower). ATC calculated predicted indoor air concentrations based on a conservative slab attenuation factor of 0.1 (1/10), then calculated the cumulative risk for the combined constituents of concern based on the predicted indoor air concentrations. The results of the calculations indicated an exceedence of the hazard index limit of 1 in only one sample (September 2012 Building 18 Lower). However, based on an evaluation of the data, ATC concludes that this sample does not indicate a significant vapor intrusion risk because (1) the calculated risk was based on an overly conservative slab attenuation factor, and (2) later sampling at the same location indicated no exceedences of acceptable risk levels. Based on the results of this risk evaluation, ATC recommends no further vapor intrusion investigation or Vapor Intru Transit-Or   mitigatio place, bu appear w If you ha Olson at Sincerely ATC Ass Justin C. Project G cc: Scot Caro Attachme usion Risk Eva iented, Multi-F on for the si ut active ve warranted. ave question (919) 871-0 y, sociates of N Ballard, P.G Geologist tt Schlosser, ol Van Buren ents: Risk C aluation Family Residen te. The ins enting or sam ns or require 0999. North Caro G. JLB Partner n – Van Bur Calculations ntial Project, S stalled vapor mpling to c additional i lina, P.C. rs, ren Law, PLL outhline Apart r barrier and confirm the information,   LC tments d passive ve mitigation , please do n Genna K Senior P enting system system perf not hesitate K. Olson, P.G Project Mana P March 4 m will rema formance do to contact G G. ager Page 4 4, 2013 ain in o not Genna ATTACHMENT 1 VAPOR INTRUSION RISK CALCULATIONS RISK CALCULATIONS Southline Apartments Project 140 Remount Road Charlotte, Mecklenburg County, NC Brownfields Project No. 10036-06-60 ATC Project No. 089.43337.1724 Page 1 of 5 Risk Equations Step 1 - Calculation of predicted indoor air concentration. Predicted Indoor Air Concentration = Sub-slab Soil Gas Concentration x Default Sub-slab to Indoor Air Attenuation Factor of 0.1 Step 2 - Calculation of cumulative risk based on predicted indoor air concentrations. Carcinogenic Risk = [ concentration(x)/screening level(x) + concentration(y)/screening level(y) + concentration(z)/screening level (z) ] * 10-6 Hazard Index = [ concentration(x)/screening level(x) + concentration(y)/screening level(y) + concentration(z)/screening level (z) ] References Summary of Risk Calculation Results Carcinogenic Risk Hazard Index Exceedences of Target Risk Levels? Building 17 Upper BLDG-17-UPPER 9/28/2012 4.39E-06 4.71E-01 No Building 18 Upper BLDG-18-UPPER 9/13/2012 1.38E-06 2.76E-01 No Building 18 Lower BLDG-18-LOWER 9/28/2012 1.08E-05 1.06E+00 Yes* Building 18 Lower BLDG-18-LOWER 12/14/2012 2.56E-06 5.24E-01 No * - See discussion in report text. ATC recommends that this exceedence be disregarded based on more detailed data evaluation. Risk Evaluation Results Per the Brownfields Program Vapor Intrusion Guidance1, a default sub-slab soil gas to indoor air attenuation factor of 0.1 was used to calculate the predicted indoor air concentration via the equation shown below. The attached spreadsheets show cumulative risk calculations for each sample showing exceedences of IHSB VISLs for soil gas. Refer to Table 1 of the Sub-Slab Vapor Sampling Results report prepared by PSI and dated January 24, 2013, for a comparison of analytical data for individual constituents to VISLs. Chloroform was removed from the cumulative risk evaluation since the Brownfields Program has already concurred that this constituent is indicative of city water. It should be noted that additional constituents are also likely indicative of sources other than vapor intrusion. However, removal of these constituents from the calculations does not substantially affect the cumulative risk results. As such, all detected constituents except chloroform were included in the cumulative risk calculations. 1. NC Division of Waste Management. Draft Vapor Intrusion Guidelines of the Brownfields Program. March 2012. 2. Environmental Protection Agency, Mid-Atlantic Risk Assessment. Regional Screening Table - User's Guide. November 2012. http://www.epa.gov/reg3hscd/risk/human/rb- concentration_table/usersguide.htm. 3. Environmental Protection Agency, Mid-Atlantic Risk Assessment. Regional Screening Level Resident Air Supporting Table. November 2012. http://www.epa.gov/reg3hscd/risk/human/rb- concentration_table/Generic_Tables/pdf/resair_sl_table_run_NOV2012.pdf. 4. The DWM IHSB VISLs for indoor air are the lower of the EPA Carcinogenic RSL for a target risk of 10-6 or the EPA Noncarcinogenic RSL adjusted for a hazard quotient of 0.2. (The EPA website reports Noncarcinogenic RSLs based on a hazard quotient of 1; the value is divided by 5 to adjust for a hazard quotient of 0.2.) Per EPA protocol2, cumulative carcinogenic risk and non-cancer hazard index for multiple chemicals of concern (x, y, and z in the example below) in indoor air were calculated via the equations shown below. The screening levels referenced in the equations are the EPA Carcinogenic and Noncarcinogenic Regional Screening Levels (RSLs)3. For the subject site evaluation, the EPA RSLs for residential land use were used. Note that the EPA RSLs are the basis for the NC Division of Waste Management (DWM) Inactive Hazardous Sites Program (IHSB) Vapor Intrusion Screening Levels (VISLs)4. As such, use of these screening levels is in accordance with NC DWM protocol. Building Location Sample ID Date Collected RISK CALCULATIONS Southline Apartments Project 140 Remount Road Charlotte, Mecklenburg County, NC Brownfields Project No. 10036-06-60 ATC Project No. 089.43337.1724 Page 2 of 5 Risk Calculations for Individual Samples Sample ID: Date: Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Carcinogenic RSL3 Carcinogenic Risk Benzyl Chloride 1.2 0.1 0.12 5.0E-02 2.40E-06 Carbon Tetrachloride 0.36 0.1 0.04 4.1E-01 8.78E-08 Chloroethane 0.34 0.1 0.03 NE NA Chloromethane 0.91 0.1 0.09 NE NA Dibromochloromethane 0.29 0.1 0.03 9.0E-02 3.22E-07 Dichlorodifluoromethane (Freon 12) 34 0.1 3.40 NE NA 1,1-Dichloroethane 0.71 0.1 0.07 1.5E+00 4.73E-08 Methylene Chloride 1.5 0.1 0.15 9.6E+01 1.56E-09 Tetrachloroethylene (PCE) 4.2 0.1 0.42 9.4E+00 4.47E-08 1,1,1-Trichloroethane 4.9 0.1 0.49 NE NA Trichloroethylene (TCE) 6.4 0.1 0.64 4.3E-01 1.49E-06 Trichlorofluoromethane (Freon 11) 6.2 0.1 0.62 NE NA 1,1,2-Trichloro-1,2,2-trifluoroethane 0.69 0.1 0.07 NE NA 4.39E-06 NO Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Noncarcinogenic RSL3 Hazard Index Benzyl Chloride 1.2 0.1 0.12 1.0E+00 1.20E-01 Carbon Tetrachloride 0.36 0.1 0.04 1.0E+02 3.60E-04 Chloroethane 0.34 0.1 0.03 1.0E+04 3.40E-06 Chloromethane 0.91 0.1 0.09 9.4E+01 9.68E-04 Dibromochloromethane 0.29 0.1 0.03 NE NA Dichlorodifluoromethane (Freon 12) 34 0.1 3.40 1.0E+02 3.40E-02 1,1-Dichloroethane 0.71 0.1 0.07 NE NA Methylene Chloride 1.5 0.1 0.15 6.3E+02 2.38E-04 Tetrachloroethylene (PCE) 4.2 0.1 0.42 4.2E+01 1.00E-02 1,1,1-Trichloroethane 4.9 0.1 0.49 5.2E+03 9.42E-05 Trichloroethylene (TCE) 6.4 0.1 0.64 2.1E+00 3.05E-01 Trichlorofluoromethane (Freon 11) 6.2 0.1 0.62 7.3E+02 8.49E-04 1,1,2-Trichloro-1,2,2-trifluoroethane 0.69 0.1 0.07 3.1E+04 2.23E-06 4.71E-01 NO Notes: NE = No established RSL. NA = Not applicable. Exceeds Carcinogenic Risk Limit of 10-4? Noncarcinogenic Hazard Index Calculations Cumulative Hazard Index Exceeds Hazard Index of 1? Carcinogenic Risk Calculations Cumulative Carcinogenic Risk BLDG-17-Upper 9/28/2012 RISK CALCULATIONS Southline Apartments Project 140 Remount Road Charlotte, Mecklenburg County, NC Brownfields Project No. 10036-06-60 ATC Project No. 089.43337.1724 Page 3 of 5 Risk Calculations for Individual Samples Sample ID: Date: Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Carcinogenic RSL3 Carcinogenic Risk Carbon Tetrachloride 0.31 0.1 0.03 4.1E-01 7.56E-08 Chloroethane 0.29 0.1 0.03 NE NA Chloromethane 0.70 0.1 0.07 NE NA Dichlorodifluoromethane (Freon 12) 8.4 0.1 0.84 NE NA 1,1-Dichloroethane 0.24 0.1 0.02 1.5E+00 1.60E-08 Methylene Chloride 1.5 0.1 0.15 9.6E+01 1.56E-09 Tetrachloroethylene (PCE) 3.2 0.1 0.32 9.4E+00 3.40E-08 1,1,1-Trichloroethane 2.7 0.1 0.27 NE NA Trichloroethylene (TCE) 5.4 0.1 0.54 4.3E-01 1.26E-06 Trichlorofluoromethane (Freon 11) 7.3 0.1 0.73 NE NA 1,1,2-Trichloro-1,2,2-trifluoroethane 0.58 0.1 0.06 NE NA 1.38E-06 NO Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Noncarcinogenic RSL3 Hazard Index Carbon Tetrachloride 0.31 0.1 0.03 1.0E+02 3.10E-04 Chloroethane 0.29 0.1 0.03 1.0E+04 2.90E-06 Chloromethane 0.70 0.1 0.07 9.4E+01 7.45E-04 Dichlorodifluoromethane (Freon 12) 8.4 0.1 0.84 1.0E+02 8.40E-03 1,1-Dichloroethane 0.24 0.1 0.02 NE NA Methylene Chloride 1.5 0.1 0.15 6.3E+02 2.38E-04 Tetrachloroethylene (PCE) 3.2 0.1 0.32 4.2E+01 7.62E-03 1,1,1-Trichloroethane 2.7 0.1 0.27 5.2E+03 5.19E-05 Trichloroethylene (TCE) 5.4 0.1 0.54 2.1E+00 2.57E-01 Trichlorofluoromethane (Freon 11) 7.3 0.1 0.73 7.3E+02 1.00E-03 1,1,2-Trichloro-1,2,2-trifluoroethane 0.58 0.1 0.06 3.1E+04 1.87E-06 2.76E-01 NO Notes: NE = No established RSL. NA = Not applicable. Exceeds Carcinogenic Risk Limit of 10-4? BLDG-18-Upper 9/13/2012 Carcinogenic Risk Calculations Cumulative Carcinogenic Risk Noncarcinogenic Hazard Index Calculations Cumulative Hazard Index Exceeds Hazard Index of 1? RISK CALCULATIONS Southline Apartments Project 140 Remount Road Charlotte, Mecklenburg County, NC Brownfields Project No. 10036-06-60 ATC Project No. 089.43337.1724 Page 4 of 5 Risk Calculations for Individual Samples Sample ID: Date: Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Carcinogenic RSL3 Carcinogenic Risk Carbon Tetrachloride 0.38 0.1 0.04 4.1E-01 9.27E-08 Chloroethane 0.75 0.1 0.08 NE NA Chloromethane 0.49 0.1 0.05 NE NA Dibromochloromethane 4.9 0.1 0.49 9.0E-02 5.44E-06 Dichlorodifluoromethane (Freon 12) 3.0 0.1 0.30 NE NA Tetrachloroethylene (PCE) 0.99 0.1 0.10 9.4E+00 1.05E-08 1,1,1-Trichloroethane 0.33 0.1 0.03 NE NA Trichloroethylene (TCE) 22 0.1 2.20 4.3E-01 5.12E-06 Trichlorofluoromethane (Freon 11) 46 0.1 4.60 NE NA 1,1,2-Trichloro-1,2,2-trifluoroethane 0.63 0.1 0.06 NE NA Vinyl Chloride 0.18 0.1 0.02 1.6E-01 1.13E-07 1.08E-05 NO Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Noncarcinogenic RSL3 Hazard Index Carbon Tetrachloride 0.38 0.1 0.04 1.0E+02 3.80E-04 Chloroethane 0.75 0.1 0.08 1.0E+04 7.50E-06 Chloromethane 0.49 0.1 0.05 9.4E+01 5.21E-04 Dibromochloromethane 4.9 0.1 0.49 NE NA Dichlorodifluoromethane (Freon 12) 3.0 0.1 0.30 1.0E+02 3.00E-03 Tetrachloroethylene (PCE) 0.99 0.1 0.10 4.2E+01 2.36E-03 1,1,1-Trichloroethane 0.33 0.1 0.03 5.2E+03 6.35E-06 Trichloroethylene (TCE) 22 0.1 2.20 2.1E+00 1.05E+00 Trichlorofluoromethane (Freon 11) 46 0.1 4.60 7.3E+02 6.30E-03 1,1,2-Trichloro-1,2,2-trifluoroethane 0.63 0.1 0.06 3.1E+04 2.03E-06 Vinyl Chloride 0.18 0.1 0.02 1.0E+02 1.80E-04 1.06E+00 YES Notes: NE = No established RSL. NA = Not applicable. Exceeds Carcinogenic Risk Limit of 10-4? Cumulative Carcinogenic Risk Noncarcinogenic Hazard Index Calculations Cumulative Hazard Index Exceeds Hazard Index of 1? BLDG-18-Lower 9/28/2012 Carcinogenic Risk Calculations RISK CALCULATIONS Southline Apartments Project 140 Remount Road Charlotte, Mecklenburg County, NC Brownfields Project No. 10036-06-60 ATC Project No. 089.43337.1724 Page 5 of 5 Risk Calculations for Individual Samples Sample ID: Date: Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Carcinogenic RSL3 Carcinogenic Risk Trichloroethylene (TCE) 11 0.1 1.10 4.3E-01 2.56E-06 2.56E-06 NO Constituent Concentration (µg/m3) Slab Attenuation Factor Predicted Indoor Air Concentration Residential Noncarcinogenic RSL3 Hazard Index Trichloroethylene (TCE) 11 0.1 1.10 2.1E+00 5.24E-01 5.24E-01 NO Notes: NE = No established RSL. NA = Not applicable. Exceeds Hazard Index of 1? Noncarcinogenic Hazard Index Calculations Cumulative Hazard Index BLDG-18-Lower 12/14/2012 Exceeds Carcinogenic Risk Limit of 10-4? Carcinogenic Risk Calculations Cumulative Carcinogenic Risk