Conservation commission raises questions, sends 'no objection' letter for proposed Hooksett car wash; requests filtration and chemical data

At its Aug. 11 meeting, the Hooksett Conservation Commission voted to send a letter to the Zoning Board and Planning Board saying it had no objection to a proposed tunnel car wash redevelopment on the former auto-dealership site, while requesting additional technical information about filtration and chemical handling.

The project team from GPI (Greenman-Pedersen, Inc.) described plans to demolish an existing auto dealership, reduce roughly an acre of impervious surface and construct a new tunnel car wash with associated vacuum stations and stormwater best-management practices. Pat McLaughlin, project manager with GPI, said the filing now estimates 965 square feet of wetland disturbance for a short culverted section at a rear “pinch point.”

The commission’s request to the applicant and the town asks for: (1) Material Safety Data Sheets (MSDS) or product data for chemicals and waxes used on-site; (2) specifications for the central vacuum filtration and any exhaust filtration; and (3) clarification of how the operator disposes of the roughly 32% of water the presenters said would not be recycled on-site.

Why it matters: The site sits adjacent to a channelized wetland that the applicants say was altered historicall,y and the commission’s letter asks the Zoning Board and Planning Board to consider water-quality and air-filtration controls alongside the minor wetland impact. The state Department of Environmental Services (NHDES) must still review and approve a shoreland/wetland application and culvert design sized to the 50-year storm, the presenters said.

Key details from the presentation and discussion

- Project team and roles: Pat McLaughlin (project manager, GPI) and Jason Bolduc (certified wetland scientist, GPI) presented the wetland assessment and grading plan. Crystal Robbins, construction manager for Washwell Car Wash, attended on behalf of the operator and answered operations questions about the vacuum system.

- Wetland impact and stormwater: McLaughlin said the team proposes routing the existing flow through an embedded culvert sized to meet NHDES requirements for the 50-year storm event (the team estimated a 36-inch culvert) while removing approximately one acre of existing pavement and adding above-ground stormwater treatment BMPs.

- Extent of disturbance: The project team reported 965 square feet of wetland disturbance (project estimate filed with staff). McLaughlin confirmed that figure when asked by a commission member: “Yes. Thank you.”

- Water recycling and disposal: Presenters said the car wash would recycle about 68% of the wash water; the remaining 32% would be discharged to the municipal sewer system. When the commission pressed for detail, the construction manager, Crystal Robbins, said the car-wash vacuums are filtered: “The vacs are filtered,” she said, and offered to obtain the specific filtration specifications from operations staff.

- Air and solids from central vacuum system: Commissioners raised concern about airborne contaminants and PFAS in vacuum debris. The project team said the central-vac system is interconnected and filtered, but did not have product-level filtration data at the meeting.

- Alternatives and siting constraints: Commissioners asked whether moving the tunnel building slightly could avoid wetland impact. The team said shifting the building would create steeper grades, more earthwork and greater overall disturbance and would interfere with required circulation for fire apparatus. The team also noted the site benefits from reduced impervious area and added stormwater treatment compared with existing conditions.

Commission action and next steps

The commission voted to send a letter to the Zoning Board and Planning Board stating there are no objections from the conservation commission and requesting the additional documentation listed above (MSDS, vacuum-filtration specifications, and clarification of sludge/wastewater handling). The motion included a request that a copy of the letter be sent to GPI. The NHDES application and state review remain required, including culvert sizing and a natural-bottom design consistent with DES rules.

The presenters agreed to provide the requested information to the commission and to the town as the project proceeds through Planning Board, Zoning Board and NHDES review.

Ending

Commission members noted the project reduces impervious area on a heavily paved lot and adds stormwater treatment, but several members emphasized they wanted the requested filtration and chemical-contents information documented in the record before final local approvals. The commission’s letter will accompany the application materials to the Zoning Board and Planning Board and a copy will be sent to GPI.