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Home My WebLink About22074_Gathing Motor_ Sub-Slab Soil-Gas Sampling Rpt 20170801Correspondence: Amec Foster Wheeler Environment and Infrastructure, Inc. 2801 Yorkmont Road, Suite 100 Charlotte, North Carolina 28208 Tel 704-357-8600 Fax 704-357-8638 Licensure: NC Engineering F-1253 NC Geology C-247 www.amecfw.com August 1, 2017 Mr. Terry Finch,PresidentSpectrumContract Services,Inc. 4725 Stockholm CourtCharlotte, North Carolina 28273 Subject:Report of Sub-Slab Soil-Gas Sampling 1100 South Tryon StreetCharlotte, North CarolinaAmec Foster Wheeler Project 6228-17-0434 Dear Mr.Finch: Amec Foster Wheeler Environment & Infrastructure, Inc. (Amec Foster Wheeler) is pleased to submit this Report of Sub-Slab Soil-Gas Sampling at the above-referenced property.Included in this report is an outline of our understanding of the project information, description of the sampling activities, analytical results,and our conclusions. Project Information The site consists of 2.324 acres located in the western quadrant of the intersection of South Tryon Street and Carson Boulevard in a commercial area. The site is currently developed with a 64,284-square foot office building.Amec Foster Wheeler understands that Spectrum Properties intends to purchase the property. A Phase I Environmental Site Assessment (ESA)of the subject property performed by others revealed that a gasoline service station formerly occupied the property. The presence of the former service station was considered a recognized environmental condition (REC).In 2014, a Phase II ESA performed by others identified petroleum hydrocarbons in the soil and groundwater at the property. Several of the concentrations of petroleum hydrocarbons identified in the groundwater at the locations of temporary monitoring wells TW-1 and TW-2 (see Figure 1)exceeded the NC 2L standards. Due to the presence of these compounds in close proximity to the office building, an environmental consultant recommended that Spectrum Contract Services, Inc. (Spectrum) retain a firm to perform an indoor air vapor intrusion assessment including sub-slab soil gas testing within the footprint of the existing building. Spectrum retained Amec Foster Wheeler to perform the testing. Report of Sub-Slab Soil-Gas Sampling August 1,2017 1100 South Tryon Street, Charlotte, North CarolinaAmec Foster Wheeler Project: 6228-17-0434 2 Proposed Scope of Services Prior to commencing the sampling activities, Amec Foster Wheeler contacted the North Carolina underground utility location service (One-Call) to mark buried objects such as pipes, tanks or underground utility lines. The purpose of this effort was to minimize the potential for probing into underground utilities that may lie immediately beneath the floor slab at the subject property. On July 19, 2017, Amec Foster Wheeler personnel mobilized to the subject property to install four temporary sub-slab soil-gas sampling points (SG-1 to SG-4)through the concrete floor slab to a depth of about six inches beneath the base of the slab.The sampling locations are shown on Figure 1.The sub-slab soil-gas sampling methods were conducted in general accordance with the North Carolina Department of Environmental Quality (NCDEQ), Division of Waste Management (DWM) Vapor Intrusion Guidance (https://deq.nc.gov/about/divisions/waste- management/waste-management-permit-guidance/dwm-vapor-intrusion-guidance). The sampling points were installed in boreholes, which were advanced using a hand-held hammer drill.Prior to drilling, Spectrum property management personnel lifted the carpet square at each location to allow access to the concrete floor slab.The dedicated sampling points were connected to plastic tubing that extended to the ground surface, purged of stagnant air, and connected to 6-liter Summa®canisters. The soil-gas samples were collected into the Summa® canisters at an approximate flow rate of 200 milliliters per minute (mL/min),a roughly 30-min sample time. Prior to soil-gas sample collection, the Summa®canisters and sample tubing were surrounded by a helium-shroud for leak-check detection. The helium-shroud consisted of plastic sheeting placed over the Summa®canisters and sample tubing and then filled with helium. A leak test was performed at each soil-gas point. Amec Foster Wheeler personnel collected the leak test samples using a Tedlar®bag. The leak test samples were screened in the field for helium using a MGD-2002 Multi-Gas leak (di-electric) detector. Amec Foster Wheeler personnel also used the helium detector to monitor the concentration of helium inside the shrouds. A leak was considered to have occurred when the helium concentration inside the Tedlar®bag was greater than 10% of the helium concentration within the shroud.The helium concentrations within the shrouds ranged from 61,000 parts per million (ppm)to 4.5 percent. Following purging and prior to connecting the summa canister, a sample was drawn into the Tedlar®bag and measured for helium.No helium was detected within three of the four Tedlar®bags. The helium Report of Sub-Slab Soil-Gas Sampling August 1,2017 1100 South Tryon Street, Charlotte, North CarolinaAmec Foster Wheeler Project: 6228-17-0434 3 concentration in the bag for sample SG-1 was well below 10%of the helium concentration within the shroud. Therefore, no leaks were identified. The Summa canisters were delivered to Con-test Analytical Laboratory (Con-test) in East Longmeadow, Massachusetts for analysis of VOCs by EPA Compendium Method TO-15. The soil-gas samples were maintained under a chain-of-custody protocol.The soil-gas sampling points were removed after the samples were collected and then the boreholes were patched with concrete. Results The laboratory analysis of the four sub-slab soil-gas samples identified several VOC concentrations which exceeded their respective laboratory reporting limits. However, the concentrations measured did not exceed their respective NCDEQ DWM Non-Residential Soil- Gas Screening Levels (SGSLs), dated October 2016. The results of the laboratory analysis are summarized in Table 1. The laboratory analytical report and chain-of-custody form are included in Attachment A. Conclusions and Recommendations The laboratory analysis did not identify VOC concentrations in the four sub-slab soil-gas samples which exceeded their respective NCDEQ DWM Non-Residential SGSLs. Based on the results of the sub-slab soil-gas analysis, Amec Foster Wheeler does not recommend additional assessment at this time. Closing Amec Foster Wheeler appreciates this opportunity to assist you on this project. If you have questions, please contact us. Sincerely, Amec Foster Wheeler Andrew J. Frantz, REM Robert C. Foster, LG Senior Scientist Associate Geologist Attachments Report of Sub-Slab Soil-Gas Sampling August 1,2017 1100 South Tryon Street, Charlotte, North CarolinaAmec Foster Wheeler Project: 6228-17-0434 FIGURE !< !< !< !< !A !A ! ! SB-5 SB-4 SB-1/TW-1 SB-2/TW-2Winnifred StW Carson Bv S Tryon StE Palmer St Wilcox St SAMPLE LOCATION MAP1100 South Tryon StreetCharlotte, North Carolina PREPARED BY: CHECKED BY: DATE:DATE: PROJECT NUMBER: 6228-17-0434 FIGURE NO: 1 LM RF 8/1/2017 8/1/2017010020050Feet ¯ ASPHALT BUILDING GRASS PAVED WALKWAY Approximate location of former gasoline station buildings/features (reported by others) !A Locations of soil borings and temporary wells installed by others in 2014 !<Approximate location and number of sub-slab soil-gas samples Site Boundary !Soil Boring Potential former dispenser island (reported by others) Potential former UST basin (reported by others) SG-1 SG-2 SG-3 Report of Sub-Slab Soil-Gas Sampling August 1,2017 1100 South Tryon Street, Charlotte, North CarolinaAmec Foster Wheeler Project: 6228-17-0434 TABLE Constituent SG-1 SG-2 SG-3 SG-4 Sample Date 7/19/2017 7/19/2017 7/19/2017 7/19/2017 Acetone 91 160 140 110 2,720,000 Benzene 0.47 0.91 1.0 1.1 1,570 Benzyl Chloride 0.28 J <0.52 <0.52 <0.52 88 Bromodichloromethane <0.67 <0.67 1.3 0.66 J 331 2-Butanone (MEK)3.8 J 5.4 J 3.8 J 6.6 J 438,000 Carbon Disulfide 2.9 J 1.9 J 0.76 J 3.4 61,300 Chloroform 2.1 1.3 4.4 2.1 533 1,3-Dichlorobenzene 1.1 1.8 1.7 1.6 NSL 1,4-Dichlorobenzene 2.5 2.1 1.7 1.1 1110 Dichlorodifluoromethane (Freon 12)660 64 280 64 8,760 Ethanol 130 110 94 52 NSL Ethylbenzene 11 20 22 20 4,910 4-Ethyltoluene 6.4 9.6 9.1 9.9 NSL Heptane 0.61 1.4 1.7 1.8 NSL Hexane 0.77 J 1.5 J 1.7 J 1.7 J 61,300 2-Hexanone (MBK)<0.41 0.80 0.79 0.91 2,630 Isopropanol 240 180 150 40 17,500 m&p-Xylene 62 100 110 100 8,760o-Xylene 16 27 28 27 8,760Methylene Chloride <3.5 0.6 J <3.5 <3.5 52,600 4-Methyl-2-pentanone (MIBK)0.43 1.7 0.57 0.52 263,000 Naphthalene 4.0 4.1 4.0 4.1 263 Propene <6.9 <6.9 <6.9 2.0 J 263,000 Styrene <0.43 0.32 J 0.40 J 0.36 J 87,600 Tetrachloroethylene 0.85 0.49 J 0.57 J 1.6 3,500 Toluene 9.3 17 20 19 438,000 Trichloroethylene 0.46 J 0.93 0.83 0.54 175 Trichlorofluoromethane (Freon 11)1.4 J 1.4 J 1.4 J 1.4 J NSL 1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113)<3.1 <3.1 0.54 J <3.1 2,630,000 1,2,4-Trimethylbenzene 21 30 32 31 613 1,3,5-Trimethylbenzene 4.4 6.7 7.6 6.8 NSL Notes: 1. VOC concentrations shown in µg/m3 2. DWM Non-Residential SGSLs = Division of Waste Management Non-Residential Soil-Gas Screening Levels, dated October 2016 3. NSL = No screening level established 4. N/A = Not Applicable 5. J = Value estimated 6. Samples analyzed for VOCs via EPA Method TO-15 7. Helium used as leak-check and was added to shroud surrounding the sample train prior to collection the sample. Helium was analyzed in the field using a MGD-2002 Multi-Gas leak (di-electric) detector. RPD 7/31/17 RCF 7/31/17 Table 1: Summary of Sub-Slab Soil-Gas Analytical Results DWM Non-Residential SGSLs Amec Foster Wheeler Project: 6228-17-0434 Charlotte, North Carolina Spectrum Contract Services, Inc. 1100 South Tryon Street Report of Sub-Slab Soil-Gas Sampling August 1,2017 1100 South Tryon Street, Charlotte, North CarolinaAmec Foster Wheeler Project: 6228-17-0434 ATTACHMENT A LABORATORY ANALYTICAL REPORT AND CHAIN-OF-CUSTODY FORM Page 1 of 23 Page 2 of 23 Page 3 of 23 Page 4 of 23 Page 5 of 23 Page 6 of 23 Page 7 of 23 Page 8 of 23 Page 9 of 23 Page 10 of 23 Page 11 of 23 Page 12 of 23 Page 13 of 23 Page 14 of 23 Page 15 of 23 Page 16 of 23 Page 17 of 23 Page 18 of 23 Page 19 of 23 Page 20 of 23 Page 21 of 23 Page 22 of 23 Page 23 of 23