Basement Waterproofing in Grand Island, NY

An island of lake clay in a river

Grand Island is part of the flat Erie-Ontario lake plain that the Erie County soil survey describes as the abandoned bed of glacial lakes, and it shares the plain's soils: silty and clayey lake-laid deposits with seasonal high water tables in the upper subsoil from December through May, with sandy mantles in places over the clay. What makes the island different is the river on every side. The Niagara River sets the base level for groundwater across the whole island, and there is nowhere for water to drain to except down to the river at the island's slow, flat gradient.

The survey notes that Grand Island draws its water supply from the Niagara River and Lake Erie rather than from wells, which is a comment on the ground as much as on the utilities: the clay is not an aquifer anyone wanted to tap. Shoreline neighborhoods on the east and west river roads have water tables within a few feet of the surface for much of the year. Interior neighborhoods are drier at the surface but sit on the same clay.

Post-war houses on a clay island

The ACS 2024 five-year estimate puts Grand Island at about 8,900 housing units, only about 4 percent of them built before 1940. The rest is spread across every decade since: roughly 13 percent from the 1950s, 17 percent from the 1960s, 16 percent from the 1970s, 13 percent from the 1980s, 10 percent from the 1990s and 11 percent from the 2010s. That means block foundations in the older subdivisions and poured concrete in the newer ones, most with footing drains, many with sumps already, and a fair number on lots that were graded flat and left that way.

The island's characteristic problem is a sump that runs nearly all winter and spring and a floor edge that stays damp anyway, because the original drain and pit were sized for a normal water table and the island does not have one. The second is a poured wall with a leaking shrinkage crack that has been wet for so long the backfill never dries.

Designing for an island water table

On Grand Island the sump system is the heart of the job. The pit is set deep enough below the slab to actually draw the water table down, the liner is large enough to keep the pump from short-cycling, the pump is chosen for continuous duty, and a battery backup is not optional, because the river-side neighborhoods lose power in the same storms that raise the water. An interior perimeter drain feeds the pit; block cores are weeped and poured-wall cracks are injected.

Discharge has to be thought through on a flat island. The town has separate storm and sanitary sewers, and sump water goes to the storm system or the yard. On lots with no fall we grade the discharge to drain empty and add a freeze-relief fitting; we do not propose dry wells in Grand Island clay, because there is nowhere for them to drain.