PFOA SURFICIAL MAPPING IN HOOSICK FALLS, NY

Existing data were inadequate to understand the sediments beneath the St. Gobain site & village wells. Taylor (1903) located an ice margin across the valley suggesting the St. Gobain factory was sited on ice contact sand & gravel. Randall (unpublished letter) suggested a recharge area for the aquifer in cemetery sand & gravel east of the wells. Previous work with students (Saffer & Madera, 1994, 1995) indicated a rapid change in the depositional environment of Glacial Lake Bascom as ice retreated through the village. The HFCSD funded my 1:12,000 mapping, geomorphic history study & stratigraphic interpretation of well logs to provide the needed context for remediation & prospecting for new village wells.

No ice contact sediment was found in the vicinity of the factory & village wells. The St. Gobain site & adjacent village area was located on stepped fluvial terraces that overlie rock, till or fine lacustrines. The cemetery was similarly sited on fluvial terraces overlying till & lacustrines. Thus, no discrete recharge zone for the village deep aquifer was mapped. Ice retreat from the 900ft Potter Hill Lake Bascom spillway nearly 4mi south of the village wells was accompanied by a transition from deep to shallow water as a series of lower spillways were rapidly uncovered; the lake dropped from 900ft to 700ft to 665ft to 625ft. Ice retreat north of the village wells quickly brought lowering of the lake to 520ft, 450ft & 410ft, effectively ending the lake. Subaqueous fan sand & gravel was deposited on the lake bottom & represents the village “confined” aquifer. However, the deep water silt-clay sediments that overlie & confine the aquifer generally become sandier & thinner northward from the high school 2mi south of St Gobain. This is also evident from well logs across the short distance from the factory to the well field. Consequently, the deep aquifer is no longer confined but can be considered a semi- confined aquifer. Recharge to the village wells likely comes from directly above through the lacustrine sediment aquitard from the overlying alluvial terraces & floodplain & possibly from the Hoosic River under pumping conditions. Independently, USGS analyses indicated the semi-confined nature of the village aquifer (Williams & Heisig, 2018).