A parking lot is a watershed with business hours.

O’Fallon Quality Drainage covers light commercial yards and parking fields as occupied sites, not as bigger backyards. Compare catch basin installation, channel drain installation, and yard drainage.

Parking-lot and loading-area sheet flow

Asphalt ponds at birdbaths

Asphalt ponds at birdbaths. Loading docks reverse fall after settlement. A hose test after hours is still a test. Record where water sits when the lot is empty enough to see paint stripes through the pond.

Map the routes people and vehicles actually use while the water is present. Note door thresholds, accessible paths, loading bays, catch basins, curbs, and striped parking areas. A commercial drainage plan starts with the operating impact of a specific pond, not with a generic promise to improve the entire property.

Catch basins, trench drains, and private storm lines

Commercial inlets are larger, deeper, and dirtier

Commercial inlets are larger, deeper, and dirtier. Private storm pipe may already exist and may be crushed. Camera the existing system before adding a new basin that dumps into a dead main.

Identify which features are visible and which runs are assumed from an old plan. A basin lid, manhole, curb opening, and roof drain can belong to different systems. Before a new inlet is connected, document the proposed receiving line, available access point, and method for confirming that water can reach the intended release.

Access, overnight work, and occupied sites

Customer ice

A pond that freezes at the front door is a liability conversation for the property, not a slogan on this website.

A medical office, church, or shop cannot lose its only drive without a plan. Write phasing, cones, and overnight windows. Drainage that ignores operations will be delayed into a worse storm season.

The work sequence should identify temporary pedestrian routes, fire access questions, delivery windows, parking impacts, and how open cuts are protected at the end of each shift. These are operational controls to discuss with the owner and provider, not claims that every site can remain fully open while construction proceeds.

Municipal stormwater review

Commercial drainage can involve a different stormwater review path than a small residential pop-up

Commercial drainage can involve a different stormwater review path than a small residential pop-up. Confirm the current requirements for the parcel with O’Fallon Engineering. This page is not a permit determination.

Bring the parcel address, existing drawings if available, a sketch of the proposed release, and the observed ponding locations to that conversation. Public-system connections, grading, and site-plan changes can raise different questions. The written scope should show whether city confirmation is a precondition or whether the work remains entirely on the lot.

Maintenance agreements after install

Who jets the private line?

Who jets the private line? Who vacuums basins twice a year? If the answer is nobody, the new map will silt. Put maintenance in the closeout packet.

A useful closeout packet identifies every accessible inlet, cleanout, grate, and outlet, along with the observation that triggers service. For example, standing water at an inlet, debris at a grate, or a roof drain that spills should lead to an inspection rather than an assumption about the buried line. Ownership of the maintenance task needs to be clear before the site changes hands.

When an engineer of record is required

Some sites need stamped drainage calculations

Some sites need stamped drainage calculations. This website does not stamp plans. If an engineer is required, the provider or owner retains one. Do not treat a rank-and-rent planning page as a construction document.

Do not infer engineering requirements from the size of a visible puddle. The owner, authority, lender, insurer, or provider may require plans based on the project scope. If an engineer is involved, keep the field observations, contractor scope, and stamped design as separate documents so one is not mistaken for another.

Comparing a site plan to field ponding

As-built conditions diverge from old site plans

As-built conditions diverge from old site plans. Trust the pond you can photograph. Then see whether the plan’s outlet still exists. Chesterfield levee-district edges and Wentzville new commercial pads are different constraint sets.

Use old plans as a question list, not proof of current pipe condition or grade. Compare marked inlets and pipe routes to the visible site, then note what cannot be confirmed without testing. A scope that says it is repairing an existing system should explain what evidence supports that conclusion and what remains an assumption.

For each affected area, pair a current photograph with a field note: source, direction of travel, occupied use, visible inlet or outlet, and the next question to resolve. This makes it possible to phase a project without pretending the first repair addresses the entire site. The owner can then compare scopes by the operational risk they reduce, not by the number of linear feet offered.

After the first material storm, walk the same route with the owner or site representative and compare the observations to the agreed work area. Look for ponding, blocked grates, restricted access, or runoff moving into an unplanned area. This is a maintenance and verification conversation, not a promise that every weather event produces the same result.

Keep service routes and emergency access visible in the packet. A basin, trench drain, or repair that works hydraulically but blocks an occupied entry or loading route has not solved the site problem. Field conditions and operating conditions both belong in the acceptance discussion.

Document the final access plan alongside the drainage sketch so the site can be maintained without reopening a route through active operations.

Send after-hours photos and a parcel address through contact. Census QuickFacts explain nearby rooftops, not commercial bid items.