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McBillin Real Estate Investment -4 - 19 January 2022 system expansion of MPE, in the RAP Apex proposes to use stingers which will remove vapor and groundwater in a single combined extraction stream (DPE), though they have not made conclusions as to whether they believe the system will be able to properly dewater the Site in order to remediate significant petroleum impact present between 20-30 feet bgs. Recent average depth to groundwater is approximately 20 feet bgs. During the 2021 DPE pilot test, Apex extracted from one DPE well at a time and reported a groundwater removal rate of 1.08 gallons per minute (gpm) over the course of the 96-hour test. In the RAP, Apex states that full-scale DPE remediation will extract from 10 DPE wells utilizing the same remediation system as the pilot test, with an anticipated maximum water flow of 3 gpm. With a combined extraction stream DPE setup, high volumes of water may overload the system's extraction capacity and limit the system's ability to extract vapor, which is the primary purpose of the system. Apex has not provided sufficient evidence that the proposed system will provide much dewatering capability, or be able to effectively extract vapor-phase hydrocarbon mass from the subsurface. 5. Connecting each DPE well to its own valve on the manifold would allow for extraction to be turned on/off in each well individually, which would allow for the targeting of extraction in specific areas as mass is removed. In the RAP, Apex does not specify the manner in which the wellhead piping will be connected to the system manifold, and thus the targeting flexibility of the proposed system is unclear. Additionally, while Apex states that the manifold construction will allow for system expansion, they do not specify the intended expansion capacity. 6. Apex does not propose any system monitoring except influent and effluent monitoring and sampling. During routine operation and maintenance, wellhead vacuum pressure should be monitored at each DPE well. Assuming Apex proposes new dedicated DPE wells, vacuum pressure in surrounding monitoring wells should also be monitored to evaluate radius of influence. 7. By 25 March 2022, please submit a Revised RAP that includes the following: a. A proposal for additional dedicated DPE wells (Comment 1). b. Clarification as to which wells will be utilized as DPE wells (Comment 2). c. A revised proposal of DPE well screen intervals (Comment 3). d. Clarification of the dewatering capability of the system, as well as the capability of the system to remove vapor in the presence of large volumes of water (Comment 4). e. A system well/manifold piping construction and connection design plan with the possible expansion capacity (Comment 5). f. A plan for operating and monitoring the system for efficiency and efficacy (Comment 6).