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Home My WebLink About25022_SouthBank Bldg_AWP Addendum_20220217Mid Atlantic Engineering & Environmental Solutions February 17, 2022 Ms. Stephanie Graham NC Department of Environmental Quality Division of Waste Management 610 East Center Avenue, Suite 301 Mooresville, North Carolina 28115 Subject: DATA GAP ASSESSMENT WORK PLAN ADDENDUM SOUTHBANK BUILDING 400 WEST MAIN STREET DURHAM, DURHAM COUNTY, NORTH CAROLINA BROWNFIELDS PROJECT NO.: 25022-21-032 MID -ATLANTIC PROJECT NUMBER: R3710.00 Dear Ms. Graham: 409 Rogers View Court Raleigh, NC 27610 office 919.250.9918 facsimile 919.250.9950 MAAONLINE.COM On February 3, 2022, Mid -Atlantic Associates submitted a Data Gap Assessment Report for the SouthBank Building Brownfields Site located at 400 West Main Street in Durham, North Carolina (the subject site). The North Carolina Brownfields Program (NCBP) reviewed the report and provided comments in an email dated February 11, 2022 that requested additional assessment at the subject site consisting of the following: Re -sampling the deep portions of Blocks D, G, and H, and resampling the shallow portion of Block H for hexavalent chromium, and Collection of additional exterior soil gas samples in the vicinity of the southeastern corner of the proposed building and along the midpoint of the eastern edge of the building footprint. The soil gas samples should be collected at depths consistent with the base of the final grade of the foundation. The requirements were re -iterated in a conference call on February 16, 2022. To address these comments, Mid -Atlantic will oversee the installation of two exterior soil gas samples (ESG-7 and ESG-8) and collection of four soil composite samples from the deep portions of Blocks D, G, and H (sample IDs D2(d), G2(d), and 112(d) respectively) and shallow portion of Block H (sample ID (112(s)). Soil samples will be collected using a GeoProbe macrocore sampler and direct push technology drilling techniques in accordance with Section 3.2 of the October 12, 2021 Data Gap Assessment Work Plan (Work Plan). Three to four equal -sized aliquots will be collected from each block at the depths indicated in Table 1 and shown in Drawing 1 and composited in and placed into laboratory -supplied sample jars accordance with the Work Plan. The samples will be provided to the Waypoint Analytical in Charlotte, North Carolina for analysis EXPERIENCED CUSTOMER FOCUSED INNOVATIVE Data Gap Assessment Work Plan Addendum February 17, 2021 SouthBank Building Page 2 400 West Main Street, Durham, NC of hexavalent chromium by EPA Method 7199. One duplicate soil sample will be collected for analysis of hexavalent chromium. Two exterior soil gas samples will be collected as shown in Drawing 1. The location of these points were selected to assess soil gas in the southeastern corner and along the eastern edge of the proposed building. Based on information provided by the Prospective Developer, the depth of the ground floor will be near current elevation. As such, soil gas sample locations will be installed from 5-5.5 ft BLS (which may be adjusted based on site lithology). Soil gas sample points will be installed, purged, leak checked, and sampled in accordance with the Work Plan. Summa canisters will be provided to Enthalpy Analytical laboratory for analysis of VOCs by method TO-15. One duplicate soil gas sample will be collected and analyzed in accordance with the Work Plan. Investigation derived waste (IDW) generated during this assessment will consist of soil cuttings from borings advanced for soil sample collection and installation of exterior soil gas points. Based on prior assessment, IDW will be spread onsite or used to backfill soil borings. Following completion of assessment field activities and receipt of laboratory analytical data, Mid -Atlantic will prepare a Supplemental Data Gap Assessment Report to document field activities and provide analysis of the data collected. Soil analytical data will be compared to the preliminary soil remedial goals (PSRG). Soil gas data will be compared to the soil gas screening levels (SGSL). As appropriate, the analytical data will be evaluated using the NCDEQ risk calculator for cumulative risk evaluation(s). The Supplemental Data Gap Assessment Report will contain relevant items as noted in Sections 7 and 8 of the Work Plan. MID -ATLANTIC ASSOCIATEA- W SE Kevin R. Clay, PG 2700 �- Daniel H. Nielsen, PE Project Geologist �,� c� Principal Engineer L4 � �,. ' V Attachments: Drawing 1: Proposed Sample Location Map Table 1: Sampling Summary DRAWINGS f � FQ Us Hwy 70 Bus ' D-2 D-3 , A D-4 aw �v,�a��sf E�SzG-8 t v , ! 4 •'� e of -3 H - - �� H-2 ESG-7 g .. Legend Proposed Exterior Soil Gas Sample Location r' � Proposed Soil Sample Location 1 inch -, feet Basement Area 0 50 100 200 300 Ground Floor Area Feet t DRAWN BY: KRC DATE: DECEMBER 2021 PROPOSED SAMPLE LOCATION MAP DRAFTCHECK M id Atlantic SOUTHBANK BUILDING JOB NO.: R3710.00 •! ENGINEER CHECK i 400 WEST MAIN STREET BY: DHN GIS NO.: 3G-R3710.00-RS1 Engineering &Environmental Solutions DURHAM, NORTH CAROLINA APPROVED BY DHN DRAWING NO.: RS1 REFERENCE: DATA FROM NC ONEMAP. BASEMENT AND GROUND FLOOR BLUEPRINTS FROM LS3P ASSOCIATES LTD. TABLE TABLE 1 Areas of Environmental Concern Sampling Summary SouthBank, 400 West Main Street Durham, North Carolina Data Gap Parcel ID Sampling Objective/Location Sample Name Type Sample Default Sample Depth* Analytical Program Soil Deep Portion of Block D D2(d) 9 feet Deep Portion of Block G G2(d) 9 feet Soil, Composite EPA 7199 Deep Portion of Block H H2(d) 2 feet 0821-08-88-2084 Shallow Portion of Block H 1-12(s) 6 feet Exterior Soil Gas Southeastern Corner of Proposed Building ESG-7 Exterior Soil Gas 5 feet TO-15 Eastern Edge of Retail Space ESG-8 Duplicate Samples** DUP-SS-2 Soil 9 feet EPA 7199 DUP-ESG-2 Exterior Soil Gas 5 feet TO-15 Notes: *Depth Below Land Surface. **Duplicates to be collected from samples that appear contaminated, if identifiable in the Feld. Default sample depth used if field evidence does not suggest and alternative sample depth.