The Corner Service Station Clinic
A health system holds a purchase option on a 0.6-acre (26,100 sf) corner parcel occupied until 1998 by a service station. The Phase I identified a 10,000-gallon gasoline UST and two dispenser islands. Phase II borings found petroleum hydrocarbons and lead above the state's residential standard in a 6-ft fill layer across the southwest third of the lot, with groundwater at 12 ft and a dissolved plume migrating south-southwest off site. A 20-ft-wide water main easement crosses the south 20 ft of the parcel. The program is a 22,000 sf two-story community health clinic, and the system's facilities standard asks for 50 surface stalls. The board wants to break ground in eight months. The architect has been told to just avoid the dirty dirt.
1. Test the program and the parking against the lot before anything else. What has to give?
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The site cannot hold the stated program and the stated parking.
- Building footprint (2 stories): 11,000 sf
- 50 stalls at ~300 sf including aisles: 15,000 sf
- Total: 26,000 sf on a 26,100 sf lot - that leaves 100 sf for setbacks, landscaping, stormwater, and drive aisles.
Realistic yield: after setbacks, the water main easement (20 x 26,100... i.e., about 2,000 sf of unbuildable strip along the south), landscaping, and stormwater, you have room for roughly 32 to 36 stalls.
Options:
- Drop to ~34 stalls and add a shared-parking agreement with an adjacent parcel - cheapest, and consistent with a clinic whose peak is weekday daytime.
- Go to three stories (about 7,300 sf footprint) to free up surface area for parking.
- Do not propose structured or below-grade parking. Excavating in a contaminated fill layer converts a manageable soil issue into a disposal and dewatering project with a five-figure-per-day cost profile.
Tell the board the parking standard and the two-story massing are mutually exclusive before the option is exercised.
2. Given the plume, the UST, and the easement, where does the building go and what protective measures are required?
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Siting logic:
- Keep occupied space off the plume where possible - the clean portion is the north and northeast, pending confirmation borings.
- Keep the building out of the water main easement entirely; no footings, no slab, no landscaping that requires excavation in that 20-ft strip.
- Put the parking over the plume in the southwest. That is the correct use of contaminated ground: it is not occupied, it caps the soil, and it needs no excavation.
Conflict to resolve: many jurisdictions now require on-site infiltration of roof runoff. Infiltrating clean water through contaminated soil is exactly what the regulator will prohibit. Request a waiver for a contamination-management area and route roof water to the clean northeast corner or to a cistern.
Protective measures:
- Vapor intrusion is the real design driver. Assume a sub-slab depressurization system and a vapor barrier under the entire occupied footprint, with vertical risers and a vented outlet above the roof - even if the current modeling says it is not required. Retrofitting it later is prohibitively expensive.
- Use low-permeability cap over the parking, not permeable pavement.
- Locate the air intakes on the clean facade and above grade, not at a loading area.
3. The board wants to break ground in eight months. Sequence the environmental work against the design phases and name the decision points.
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Eight months is possible only if the environmental work runs ahead of design, not beside it.
Sequence:
- Weeks 0-4: engage a state-licensed environmental professional; submit the remediation work plan. The UST must be removed or formally abandoned with a closure report - if it sits under the proposed footprint it must be removed, which is a 60-90 day activity on its own.
- Weeks 4-16: confirmatory sampling and regulator review. Expect at least one comment cycle; assume it.
- Design constraint, not a design task: the outcome is likely an environmental covenant or activity-and-use limitation that runs with the deed. It will fix the boundary of no-residential-use and no-groundwater-use areas, prohibit infiltration, and require the vapor barrier.
The critical decision point: the covenant boundary must be agreed before the site plan and foundation package are finalized. If it moves, the building moves.
Actions:
- Structure the UST removal, vapor barrier, and sub-slab system as a separate early bid package so construction can start on the clean portion.
- Loop in the lender and the title insurer now - an unrecorded covenant will stall the closing, not the construction.
- Budget a schedule contingency of 6-10 weeks and tell the board where it comes from.