349-24 PROPOSAL- Lindsley Ave Proposal - additional sampling -Dec 2024.pdf

November 25, 2024 Proposal for Professional Services –Groundwater Monitoring and Reporting Re: Lindsley Avenue Bus Garage; 6 Lindsley Avenue Page 2 of 6 in the previous proposal), therefore four (4) additional rounds are required by the NJDEP Regulations. BACKGROUND Based on the review of the history of the Site, impacted soil and groundwater with benzene, toluene, ethylbenzene, xylenes (BTEX) above the NJDEP SRS and GWQS were detected at three separate areas of concern associated with discharges from former 2,000-gallon gasoline Underground Storage Tank (UST), former 550-gallon waste oil UST, former 3,000-gallon gasoline UST, and former 2,000-gallon gasoline UST. Free-phase product was detected at different wells. A recovery program, which consisted of pumping free-phase product from these wells, was subsequently implemented. Localized free-phase product within the overburden water unit has been observed in monitoring well MW-5. The free -phase product observed within MW-5 may have originated from either of the former 2,000-gallon USTs and appears to have migrated downgradient along the general groundwater flow directions within the overburden water-bearing unit. It is postulated that historical product discharges from the former USTs combined with the discontinuation or breach of the natural low permeability barrier (organic clay and silt layer) may have created preferential pathways for the free-phase product and dissolved phase to move downward and impact the deeper overburden water-bearing unit at the Site. A remedial action was implemented using High Vacuum Extraction (HVE) treatment system at MW-5. HVE was utilized to remove accumulated product in MW-5 for few years and reduce residual product in soil. During the most recent sampling event at Lindsley Avenue, approximately half a foot of free product was identified in MW-5. Monitoring the recovery of the product in the well and the measurements of product thickness in MW-5 showed that the product is frequently being accumulated after the HVE applications. In August 2022, a product and impacted soil delineation investigation was completed at the area around MW-5. The conducted investigation included soil borings, soil sampling, temporary wells and groundwater sampling to identify the limits of product impacts in the vicinity of MW-5. The results of the investigation/delineation identified the

ded soil borings, soil sampling, temporary wells and groundwater sampling to identify the limits of product impacts in the vicinity of MW-5. The results of the investigation/delineation identified the approximate limits of impacted soil in the vicinity of MW-5 and the source area in the vicinity of former fuel oil/gasoline USTs. Therefore, CME completed the removal of contaminated soil within this area to eliminate the source of the product at this location and avoid the migration of the contaminated groundwater