Once a stormwater system gets built, most of it disappears from sight. Pipes go underground. Ponds get graded and planted over. Inlets sit flush with the ground, easy to walk right past. As built surveys are how you get a real record of what’s actually down there. That record gets measured after the work is done, not guessed from old plans.

What an As-Built Survey Records for a Completed Stormwater System

Once construction wraps up, a survey crew goes back out to measure exactly what got built. That includes stormwater ponds, drainage pipes, catch basins, manholes, headwalls and drainage inlets.

This step is different from the ground study done before construction started. That earlier work looked at raw land and figured out how water would move across it. This step looks at the finished system itself. The pipes that are now in the ground. The structures that now sit where the plans said they should go. It’s a record of what actually exists, not a study of what the land looked like before anyone touched it.

Getting this record right matters for years to come. Most of these parts become impossible to see once the site is finished and planted.

Checking Pipe Inverts, Inlet Elevations, and Outlet Structures

A pipe isn’t just a pipe. Its exact height matters a lot, especially where it meets other parts of the system. Survey crews measure key points, like pipe inverts, inlet rims, outlet points and other related parts.

A pipe invert is the lowest inside point of the pipe, and crews measure it with care. Get that height wrong on paper, even by a little, and water might not flow the way it’s supposed to. Inlet rim heights matter too, since they show exactly where water enters the system at the surface. Outlet points get measured the same way, so there’s a clear record of where water finally leaves the system.

This step stays narrow on purpose. It’s about capturing exact heights at these key points, not about flood heights or general height mapping, which are different topics covered elsewhere.

Verifying Stormwater Pond Dimensions and Constructed Storage Features

A stormwater pond has to hold a certain amount of water to do its job. That means its shape and size matter just as much as the pipes feeding into it.

An as built survey can record the pond’s real shape once it’s built, along with its bottom heights, berms and control structures. This checks what was actually built on site, not just what the design called for on paper. A pond that was supposed to be a certain depth might have come out a little different once the dirt was actually moved. This step catches that.

This part is strictly about checking what got built. It’s not about drainage design choices, LiDAR data or flood risk, which get covered in other places.

Comparing Installed Drainage Improvements With Approved Plans

Once the field measurements are collected, they get compared against the plans that were approved before the project started. That check shows exactly where pipes, structures or pond parts ended up, compared to where the plans said they should be.

Sometimes everything lines up closely. Other times, a pipe run shifted a few feet, or a structure ended up a little higher or lower than planned. Either way, this check creates a clear, true record of the final locations. That matters a lot more than people think once the ground gets covered back up.

This step focuses on the drainage system alone. It’s a different topic from construction staking, which happens earlier, before anything gets built.

Preparing Final As-Built Records for Stormwater Project Closeout

The last step is putting all this measured information together into final records. These records help the reviewing engineer, the property owner and whatever closeout rules a city or agency has for the project.

Buried pipes and finished drainage structures are hard, if not impossible, to see once building wraps up and the site gets landscaped. That’s exactly why these records matter so much later on. If a pipe ever needs repair, or a pond needs work years down the road, this as built record tells crews where everything actually sits. Nobody has to dig around and guess.

Good records now save a lot of trouble later, especially on a system where most of the parts stay buried out of sight.

Frequently Asked Questions

What information is usually included in an as-built survey for a stormwater system? 

It usually includes the built locations and heights of relevant ponds, pipes, drainage structures, inlets, outlets and other listed stormwater parts that were part of the finished project.

When should stormwater pipes and drainage inlets be surveyed for as-built records? 

Field measurements need to happen at the right building stages, especially for parts that will soon get buried, covered or hard to reach. Waiting too long can mean losing the chance to measure something correctly.

Can an as-built survey show whether a stormwater system matches the approved plans? 

Yes, in the sense that measured field numbers give the true, built information, which can then be checked against the design papers. Rule and code decisions, though, usually rest with the engineer or reviewing authority.