NYSDEC letter re: Con-Edison release report at 7 WTC substation,

NYC 9/11 Public Portal Document

NOV y lyyj 1^5 .-1^

P.5 bW 21 '01 06:02PM R & D

southwestern boundary delineator. No access is available beyond the southern border of the 7WTC footprint due to the on-going demolition activities to the south of Vesey Street.

The Con Edison uansfbnneTS at the site were situated in aboveground concrete vaults, the walls of which extend below grade. MW-6 and MW-7 will be installed in order to detennine whether there has been any pooling of product within the coacnete vaults. If product is identified, the wells will serve as product recovery points as well as delineate the northern and northeastern boundaries, respectively.

UTILITY CLEARANCE

Jacques Whitford Company, Inc. (JWC), Con Edison’s consultant, has called in and started the Code 53 Utility Mark-Out process. Utilities clearance is expected by Monday, November 19, 2001. Con Edison will verify utility clearance for 7WTC building footprint and surrounding area. Due to unmarked Verizon, utilities at the intersoction of Vesey Street and Washington, Verizon personal will bo available on-site to give utility clearance at the MW-5 location.

MONITORING WELL INSTALLATION & COLLECTION OF SAMPLES

The soil borings for the installation of the monitoring wells will be advanced using a drill rig equipped with hollow stem auger (HSA) and air rotary capabilities. Where feasible, spilt spoon samplers will be advanced at five-foot intervals until the final depth of the boring, which will be at approximately 10 feet below the observed water table. Groundwater is anticipated to be encountered at 15 feet below grade, with the expected total depth of each boring being 25 feet below grade.

A geologist or engineer firom JWC will supervise the drilling activities. Drilling will be conducted by Aquifer Drilling & Testing, under subcontract to JWC. The lithology of the soil and any physical evidence of contamination in the soil samples will be documented. Soil boring and well construction logs will be completed for each attempted location.

At each drilling location, split spoon samples will be collected continuously. Soil samples will be examined for visual and olfactory evidence of contamination and screened for the presence of volatile organic compounds with a Photo Ionization Detector (PID). The soil sample showing the most evidence of contamination will be set aside for possible laboratory analysis. If no evidence of contaminatioc is observed in the soil samples, the sample directly above the water table will be set aside for possible laboratory analysis.

A decontamination pad will be constructed on-site to clean the split spoons prior to the commenccoieat of drilling and after each use. Decontamination will consist of scrubbing with a noc-phojphatc detergent and potable water solution and rinsing with potable water, at a minimum. All decontamination water will be contained until disposal.

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