Mount Clemens Clinton Place Vapor Mitigation System

ASTI completed methane testing, sub-slab Pressure Field Extension (PFE) testing, and the design of a Sub-Slab Depressurization (SSD) vapor mitigation system for the Subject Property. Methane monitors were in use in 94 first-floor residential units to confirm that methane gas from the former Mt. Clemens Landfill was not migrating into the buildings. In accordance with EGLE requirements, Clinton Place Housing LDHA LP was required to randomly test 25 percent of the in-use monitors within 90 days of ownership. ASTI conducted this testing using a landfill gas analyzer (LGA) to screen real-time methane concentrations and evaluated the breathing zone within 24 residential units selected by the client. Screening results were compared to the status and performance of the installed methane monitors.

ASTI also conducted PFE testing at 26 locations across 13 two-level multifamily residential buildings and one high-rise residential building. Testing involved installing a temporary fan at a six-inch diameter core in the concrete slab and placing vacuum monitoring pins at varying distances to measure vacuum pressure throughout the slab. These readings were used to determine the radius of influence for each test location. EGLE requires a minimum vacuum of -0.02 inches of water column beneath the entire slab, and the PFE results were used to determine the appropriate spacing of vapor extraction points.

Following the field investigations, ASTI prepared detailed plans and specifications for the SSD system for the storage building and revised existing plans for the high-rise and townhouse buildings to incorporate EGLE comments. Work included preparing design details for pipe connections and sleeves needed to route extraction piping through foundation walls, as well as developing specifications for piping, granular fill, and the venting system. ASTI coordinated closely with the project architect to determine riser pipe locations on exterior walls, design the horizontal collection system installed beneath hollow-core concrete floor panels, revise specifications, and update SSD installation plans.

The project presented several challenges, including conducting PFE testing in occupied residential units and the absence of architectural plans due to the age of the development. ASTI addressed these challenges by scheduling testing during periods of unit vacancy and performing field verification to accurately locate existing SSD system piping.