Olathe Drainage & French Drain Installation

Olathe has the newest housing stock of any city we serve, median year built 1997. Its largest single cohort is the 2000s at 14,310 units, a quarter of everything in the city, with the 1990s adding another 10,179. Combined, 43.7 percent of Olathe's housing was built between 1990 and 2009. Barely 3 percent predates 1950.

New housing is not the same as no drainage problems. It means the problems are uniform: whole subdivisions built to the same grading plan in the same few years, with the same buried corrugated downspout lines and the same swale design, all reaching 20 to 30 years old at once. When one house on a street has water at the foundation, the neighbors usually do too, and they usually have the same cause.

Olathe drains to Cedar Creek, Kill Creek and Mill Creek, all north-flowing tributaries of the Kansas River. The Kansas Geological Survey notes that these north-flowing streams have steeper gradients and greater local relief than the east and south-flowing streams elsewhere in Johnson County. The city straddles two basins, the Lower Kansas River and the Lower Missouri-Crooked.

Underneath it is the same Sharpsburg and Grundy loess as Overland Park, with Woodson in the flatter spots, which KGS rates as very slow in permeability. KGS also records that Grundy and Woodson hold apparent water tables less than 30 inches deep for under a month in most years, dropping below six feet in the dry season. That short, shallow, seasonal perch is what produces a yard that is a swamp in April and concrete in August, and it is why a drain sized on a summer site visit disappoints in spring.

Olathe Public Works works from Title 17 of the municipal code, devoted entirely to stormwater management, and it writes numbers into the code that neighboring cities leave to engineering judgment. OMC 17.10.020 requires detention facilities be designed for the 1-year and 10-year design storms, and permits the City Engineer to require up to the 100-year storm where downstream flooding is known.

The provision that separates Olathe from Overland Park next door is OMC 17.12.050: a land disturbance permit is required for any grading or land disturbance activity, with no acreage floor written into the trigger. Kansas City, by contrast, requires nothing below one acre. Olathe also protects Stream Corridors on any stream draining 40 acres or more, at 15 feet from the ordinary high water mark each side under 25 acres and 30 feet between 25 and 40 acres. If there is a creek behind your house, that setback governs what can be built near it.