Why a storm survey is not a sewer survey
A storm drain camera inspection is not a sewer survey under a different name. A sanitary line is small, consistent in diameter, laid to a design and reachable through cleanouts that exist for the purpose. A private storm system is none of those things. It collects from roof leaders, area drains, trench drains, parking lot inlets and catch basins, it changes diameter as it collects, it is built of whatever material was current when each phase went in, and it runs to a discharge point that may be a public line, a detention basin or a swale. Access is through structures rather than cleanouts, and half the pipe was installed by people who left no record.
Getting the water out first
The single practical difference between storm and sanitary inspection is standing water. A sanitary line drains between uses. A storm line frequently holds water permanently, in sumps at the bottom of catch basins, in low spots, and behind partial blockages. A camera cannot see through it. So the sequence starts with dewatering: pumping the structures down, vacuuming sumps, and where a line holds water along its length, either pumping from a downstream structure or accepting that a section will be surveyed with a submersible camera that reports far less.
The same logic sets the timing. Storm inspection is dry-weather work. Surveying during or immediately after rain produces a recording of moving water, and a system that cannot be inspected during a dry spell has told you something about its condition already.
Book the survey against the forecast, not the calendar. A storm inspection scheduled for a fixed date frequently gets done in poor conditions because the crew traveled. Agreeing in advance that the work moves for weather, and what that costs, is better than paying for a survey of a full pipe and repeating it later.
Equipment that suits the diameter
- Push cameras. Fine for roof leaders, yard drains and small laterals, and useless beyond a modest distance in large pipe where the head wanders.
- Tractor or crawler cameras. The working tool in anything from moderate to large diameter, with a pan and tilt head that can look at the crown and at each connection rather than only straight ahead.
- Floating rafts. Used in large pipe that still carries flow, where the camera rides the surface and the operator inspects what is above the waterline.
- Pole cameras. For a quick look into a structure and down the first length of each pipe leaving it, which is often enough to triage a whole site cheaply.
- Locators and sondes. Essential rather than optional here, because the point is frequently to find out where the pipe goes.
Mapping while surveying
The deliverable from a first storm inspection should be a drawing as well as a recording. Every structure gets an identifier and a location. Every pipe gets its two end structures, its diameter, its material and its direction of flow. Depths at each structure and the invert elevations, where they can be taken, turn the sketch into something an engineer can use. Once that exists the system can be inspected in sections over years rather than surveyed from scratch each time, and any later proposal to line a run can be read against a known layout. Planning storm drain inspection in Denver without that map is guesswork, and producing it is usually the most valuable part of the first visit.
The defects that matter most on a storm line
Storm pipe fails in ways sanitary pipe does not. Corrugated metal loses its invert to corrosion while the crown stays sound, so the camera is looking down at soil rather than at pipe. Concrete pipe loses joint gaskets and takes in soil at every joint, leaving voids outside and sinkholes above. Corrugated plastic deflects under load and separates at couplings. Across all of them the defect that matters most is the one that admits soil, because the hole in the pipe is usually a smaller problem than the cavity forming around it. Understanding how storm lines are lined without excavation makes those distinctions visible on the recording rather than abstract.
Structures count as much as pipe
Catch basins, area drain boxes, manholes and junction structures fail independently of the pipe between them. Frames work loose, brickwork and mortar joints deteriorate, benches and channels erode, and the pipe connections into a structure open up and let soil in. A storm inspection that reports only on pipe has left out the most accessible and most frequently failing part of the system, and photographs of the inside of every structure cost almost nothing to take while the crew is already there. Asking verified inspection crews serving Denver to include structure condition in the scope makes the report complete.
What to do with the report
A first survey typically produces a long list, and almost none of it is urgent. The useful next step is sorting it: defects admitting soil and undermining a surface first, defects restricting capacity ahead of the next wet season second, and everything else on a schedule. A system that has been mapped and graded once can then be managed rather than reacted to, which on a large property is the difference between planned rehabilitation and a sinkhole in a parking lot.
Common questions in Denver
Why does a storm drain have to be dewatered before inspection?
A camera cannot see through standing water, and storm lines routinely hold it permanently in sumps and low spots. Structures are pumped down and sumps vacuumed first, otherwise the survey records a water surface rather than the condition of the pipe.
When is the right time of year to inspect a storm system?
During dry weather, and scheduled against the forecast rather than a fixed date. Surveying during or just after rain produces a recording of moving water. Agreeing in advance that the visit moves for weather avoids paying for an unusable survey.
What camera is used in large diameter storm pipe?
Usually a tractor or crawler camera with a pan and tilt head, which can examine the crown and each connection rather than only looking ahead. Where large pipe still carries flow, a floating raft inspects what sits above the waterline.
Should the inspection produce a map?
Yes, and on a first survey it is often the most valuable part. Every structure identified and located, every pipe recorded with its end structures, diameter, material and flow direction, with depths where they can be taken.
Do catch basins and structures get inspected too?
They should. Frames, mortar joints, benching and the pipe connections into a structure fail independently of the pipe and are the most accessible part of the system. Photographs of every structure interior cost little while a crew is already on site.