Kansas City Drainage & French Drain Installation

Just over 20 percent of Kansas City's 246,544 housing units were built in 1939 or earlier, and the median year built is 1969. That is not trivia here, because 1950 is also roughly the line for the combined sewer service area: the older part of the city, broadly from the Missouri River south to 85th Street and from State Line Road east to I-435, drains stormwater and sewage through the same pipe. Construction on those lines began in the 1850s in the River Market, in stone and brick.

About 58 of the city's roughly 420 square miles of sewer service area are combined. If your house is in that footprint, every gallon of roof and yard water you send into the system during a storm is competing with sewage for the same pipe, which is why basement backups in the core behave differently than they do in a 1990s subdivision out south.

The Pleistocene glaciers stopped just north of the Missouri River. That single fact splits the city into two drainage problems. North of the river you are working in glacial till and loess. South of it you are in loess over the Kansas City and Lansing Groups, alternating limestone beds separated by clayey to sandy shales.

The ledge that matters most is the Bethany Falls Limestone, a 20 to 24 foot unit quarried and mined widely beneath the city. Where that rock sits close to the surface, water moves along the top of it rather than down through it, and a trench that stops short of the right depth simply routes water along a new path instead of removing it. The Blue River, which drains about 272 square miles and runs 41 miles through the metro, is described by the Missouri Department of Conservation as flashy and prone to frequent flooding, with an estimated 2.6 miles already lost to channelization.

Kansas City is the only city in this metro that charges every property a monthly stormwater utility fee based on hard surface. City Code Sec. 61-4 sets it at 50 cents per month for each 500 square feet, or part of 500 square feet, of runoff surface. Two credits are available and both reward drainage work: a 50 percent ratio credit where total property area to runoff surface is at least 30 to 1, and a detention credit of 10 to 50 percent for a privately owned, properly maintained detention structure. Neither is automatic. You have to apply.

What you may not do is the thing homeowners try first. Ordinance No. 150452, adopted in 2015, prohibits connecting downspouts, sump pumps or other drainage directly to the sanitary sewer, and KC Water runs a free program to find and disconnect those. Contrast that with Johnson County across the line, where stormwater is funded by a countywide sales tax and no property-level fee exists, so there is no credit to earn and no meter to reduce.