Install a French drain only after the water path is mapped.

O’Fallon Quality Drainage plans French drain installation for O’Fallon and St. Charles County clay lots. A French drain here is a pitched collector in washed gravel with a named legal outlet, not a pipe in random dirt. Photograph the wet zone after rain, then compare yard grading and downspout drainage before a drainage review.

Why St. Charles clay holds water after original grade

Perched water versus a missing outlet

A trench that ends in the same clay bowl is a longer pond. Name the daylight, pop-up, or approved storm connection in the same paragraph that names the pipe.

Confirm the map unit in the USDA Web Soil Survey instead of guessing the soil name. Many west-metro plats perch water because fines fill pore space after a storm. Original subdivision grade can settle into a backyard basin years later. Roof leaders that splash at the foundation add a second source. A useful installation file separates those sources before anyone opens a trench.

A collector cannot fix a lot that still dumps thousands of gallons at the wall. If the wet zone is a roof-water problem first, start with leaders. If the lawn is a bowl, regrade may belong in the same proposal. If water sits below the surface along a path toward a legal release, a French drain can be the right tool.

How a collector trench is placed relative to the wet zone

Place the run where water actually sits or travels, not where a catalog drawing looks tidy

Place the run where water actually sits or travels, not where a catalog drawing looks tidy. On an occupied O’Fallon lot that often means the downhill edge of the pond, a line parallel to a wet foundation, or a collector that intercepts flow before it reaches a patio. Mark utilities through Missouri 811 before any excavation talk becomes a schedule.

Depth follows the wet horizon and the outlet elevation, not a slogan number. If the only legal release is barely below the lawn, a deep trench cannot create fall that physics does not allow. Ask the proposal to show inlet elevation, outlet elevation, and the percent of fall between them.

A useful sketch also distinguishes the collection zone from the conveyance zone. The perforated portion belongs where water must enter. A solid carrier may make more sense after collection, where the job is simply to move captured water to the approved release. Treating every foot as the same pipe can make inspection and later repair harder.

Pipe, sock, and washed-gravel choices that change flow

Perforated pipe, washed gravel, and a fabric or sock each do a different job

Perforated pipe, washed gravel, and a fabric or sock each do a different job. Fines in St. Charles clay can clog a wrapped pipe if the envelope is wrong. Round washed stone creates void space; mixed dirt backfill does not. The written scope should name pipe diameter, perforation pattern, gravel size, fabric location, and whether a sock is used instead of a full wrap.

Cleanouts turn a buried collector into something that can be flushed later. A run without a cleanout is harder to diagnose when flow slows. Ask where cleanouts sit, how they are capped, and who is responsible for first-year checking.

Pitch, cleanouts, and a planned daylight or pop-up outlet

Pitch is the difference between a drain and a buried trough

Pitch is the difference between a drain and a buried trough. A French drain that cannot daylight or legally connect is unfinished. See the outlet field note before accepting a pop-up in a low corner as the entire release plan.

City materials from O’Fallon Engineering belong in the file when grading or storm connections are involved. Neighbor lawns, streets, and shoreline lots are not default dumps.

What excavation should protect on an occupied lot

Irrigation, walks, and roots share the French drain trench

Irrigation, walks, fences, play sets, and tree roots all sit in the same yard as the wet zone.

A complete proposal names protection, spoils handling, and restoration. It also names who restores sod versus seed and who returns after the first heavy rain.

DIY work versus a site-specific installation scope

Utility locates and inspectable French drain decisions

A homeowner can observe the water path, keep photographs, and compare proposals. Installation choices become less forgiving when the trench must cross utilities, run beside a foundation, pass beneath hardscape, or reach an outlet whose legality and elevation are uncertain. Missouri 811 marks public utilities, while private lines may still need a separate locate.

A professional scope should make the decisions inspectable: collection location, pipe type, gravel and fabric approach, elevations, cleanouts, discharge, protection of existing features, restoration, and the first-storm check. A generic material list is not the same thing as a plan for a particular yard.

Reading linear-foot quotes as layers, not a single number

HomeGuide exterior bands are not an O’Fallon bid

HomeGuide’s 2026 exterior guide lists $10 to $35 per linear foot and $500 to $8,800 average installed for a yard or curtain drain (fetched 2026-09-23). Those bands mix national labor markets and do not price one O’Fallon clay lot, restoration, or a legal outlet.

Interior basement drain figures in the same family of national guides are a different trade and are not used as an O’Fallon bid. Ask each bid to price or exclude locate marks, excavation, pipe, stone, fabric, cleanouts, discharge, and surface repair. A cheap linear-foot number that omits restoration is not cheaper. It is incomplete.

First-storm checks that prove the trench is working

After backfill, watch the next heavy rain

After backfill, watch the next heavy rain. Water should move along the planned path, not reappear in the old bowl. Photographs of the outlet, the former pond, and any cleanout help later maintenance. If the pond returns, separate clogging, lost pitch, and a still-illegal or missing release before naming a repair. Compare French drain repair only after that diagnosis.

The closeout packet should identify the route, cleanout locations, restoration limits, and the person responsible for the first-storm check. That does not guarantee performance. It gives the owner and a later provider enough information to compare the observed water path with the intended one before adding more excavation.

Census QuickFacts for O’Fallon city and the eight nearby town guides under areas we serve keep the lot in its metro context. This website routes information. A local provider must inspect and write the actual scope.