French Drain Installation in Frankfort, KY

A city in a river valley

FEMA's high-water-mark project for Frankfort records that the flood of December 1978 was the worst in the city's history, with the Kentucky River cresting at a record 48.47 feet and more than half of downtown under water. Frankfort has a floodwall now, but lots on the valley floor in downtown and South Frankfort still sit on river-deposited soil with a high water table whenever the river runs high, and a basement there can take water from below regardless of what the roof and yard are doing.

The valley-floor problem is solved with sumps and interior drains that lift water to a discharge point above the flood, not with French drains that have no outlet lower than the water. The hillside problem is different: the neighborhoods on the bluffs above downtown, along the East-West Connector and out US 60 and US 127, have real slope, shallow soil and water moving fast across the surface and along rock contacts.

Hillside lots and seep lines

Franklin County is on the western edge of the Inner Bluegrass, where the limestone begins to give way to shale-rich Outer Bluegrass rock. The Kentucky Geological Survey's regional land-use notes describe seepage at the contact between permeable and impermeable layers as a cause of wet basements and foundation trouble, and on Frankfort's hillsides that is exactly what a wet spot on a slope or a basement wall that weeps only on the uphill side turns out to be.

The answer is an interceptor: a curtain drain cut across the slope above the house, deep enough to catch the water moving along the contact, carried around the house to daylight downhill. Combined with downspouts routed underground and off the slab, it dries out most hillside foundations. Armored swales and dry creek beds handle the surface water that a steep lot sends toward the house in a storm.

Sump discharge in a city with a river to respect

Frankfort's valley-floor neighborhoods rely on pumps more than anywhere else in the service area, because a gravity outlet lower than the basement floor often does not exist and, when the river is up, the ground itself is saturated from below. A sump system there has to be built for the long haul: a sealed basin, a pump sized for sustained inflow rather than an occasional storm, a battery backup because the storm that raises the river is also the one that drops the power, and a discharge line that carries water to the street or a swale well clear of the foundation.

The discharge is where valley-floor systems fail. A pump that pushes water out a wall onto the lawn three feet from the house is refilling its own basin. In Frankfort's hillside neighborhoods the discharge can daylight downhill and gravity finishes the job; on the flats it has to reach a curb or a storm inlet with the city's approval, in solid pipe on steady fall, with a freeze-resistant outlet so a January cold snap does not lock the line. NWS normals for the region show about 14 inches of snow and hard freezes every winter; a frozen discharge line in Frankfort means a flooded basement on the next thaw.

Frankfort's housing stock

Frankfort has an unusually large stock of nineteenth-century houses for its size, and their cellars, stone foundations and century-old downspout arrangements make up a good share of the drainage work in town. The mid-century neighborhoods on the plateaus east and west of the river are ranches and split-levels with settled backfill and downspouts at the wall. Both start the same way: roof water away, positive grade at the foundation, then whatever the remaining water calls for.

The assessment is free and on site, and in Frankfort it starts with one question: are you on the valley floor or on the hill?