Remedial Investigation/Feasibility Study (RI/FS) at Former Fort Custer FUDS, MI

HGL performed a FUDS RI/FSy to delineate the nature/extent of munitions at four Munitions Response Sites covering terrestrial and underwater areas. Underwater operations included DGM, SSS, ROV, and UXO diver intrusive investigations. The main body of Eagle Lake (84 acres) was surveyed using tightly spaced DGM transects (4-meter-wide transects on 6-meter spacing). SSS and bathymetry surveys preceded the underwater DGM survey to identify obstacles/obstructions. A dive team conducted the underwater reacquisition/intrusive investigation of a selection of the other DGM anomalies to determine the nature/extent of potential disposal or target areas. Over 2,000 anomalies were identified and 110 anomalies were intrusively investigated by divers.

A Phase II diving effort was conducted to address HTRW concerns with drums buried on the floor of Eagle Lake. The dive team removed 15 intact 55-gallon drums.

Phase II hard hat diving was conducted to address HTRW concerns with buried drums on the floor of Eagle Lake.

Land-based characterization included DGM density transects with advanced geophysical classification (AGC) cueing/intrusive investigation followed by DGM grids with AGC cueing/intrusive investigation. Surrounding areas were investigated using transects spaced according to historical munitions used, and AGC grids were placed in high-anomaly density areas. Cued data was collected using man-portable vector (MPV) technology along transects and a MetalMapper 2×2 in high-use-area grids. All cued data collected were analyzed, and anomalies were classified as targets of interest (TOIs), non-TOIs, or inconclusive. Intrusive results from transects/excavated grid anomalies were used to determine the effectiveness of the AGC sensors. Transect anomaly density distribution was used to delineate the extent of high-density areas, then intrusive investigation along transects/within grids determined the nature of the anomalies, leading to high/low-use area determinations.