A superintendent gets a call from the owner’s representative: heavy rain moved through overnight, and the owner wants to know how the perimeter controls held up. The inspection report in the file is from last week. The crew can walk the site, but on a large disturbed area, walking does not show how the whole site drains, and a text-only report does not show it either.
Stormwater records are one of those items nobody thinks about until someone asks for them. This article looks at what Colorado construction teams are expected to document, and where dated aerial imagery can support that file without pretending to be something it is not.
Why the paper trail matters
The federal rule is the starting point. EPA states that a Clean Water Act permit is required for stormwater discharges from construction activity that disturbs at least one acre, and smaller sites are covered when they are part of a larger common plan of development that will ultimately disturb one acre or more. The federal construction and development rule, 40 CFR 450.21, requires effective erosion and sediment controls, and it calls for stabilizing disturbed areas promptly once work stops, if work will not resume within 14 days.
In Colorado, the permitting program is run by the Colorado Department of Public Health and Environment (CDPHE), which publishes its own guidance for the construction stormwater permit and a stormwater management plan (SWMP). Requirements depend on the specific permit and site, so the permit language controls over anything summarized here.
What CDPHE guidance says about inspections
CDPHE’s stormwater management plan guidance describes an inspection schedule in practical terms. The first inspection happens within seven calendar days of the start of construction activities. After that, the permittee can inspect at least every seven calendar days, or at least every 14 days plus a post-storm inspection within 24 hours after the end of any precipitation or snowmelt event that causes surface erosion. Sites that discharge to a water body designated as an Outstanding Water follow the seven-day schedule. The guidance also describes reduced-frequency situations, such as areas awaiting vegetation and winter conditions, with their own documentation conditions.
The guidance is specific about what an inspection report contains: the inspection date, the names and titles of inspectors, weather conditions, construction phase, estimated disturbed acreage, locations of discharges, control measures that need maintenance, inadequate controls, additional controls needed, and the inspection frequency in use. A qualified stormwater manager signs the report once corrective actions are complete. The reports become part of the plan, and a copy of the plan is kept on site while construction activities are occurring.
One caution: the copy of this guidance we reviewed is a 2019 document hosted by Boulder County, and it notes that permit language and regulations control if they conflict. Confirm current requirements with CDPHE and your stormwater manager before building a records routine around any summary.
Where aerial imagery helps
None of that makes a drone flight an inspection. What aerial imagery adds is a dated, whole-site view that is hard to get on foot. In practical terms:
- Context for the report. A single flight shows the perimeter controls, stockpile locations, haul routes, and the line between disturbed and stabilized ground in one record, so the written report has a visual reference behind it.
- Comparison over time. Flights from the same vantage points month to month show how disturbance and stabilization changed. A before-and-after pair around a storm makes drainage patterns visible.
- Hard-to-walk areas. Steep slopes, large sites, and areas with active equipment can be viewed from above without sending someone into them.
- A shared reference for the team. When the owner, the general contractor, and the stormwater manager are looking at the same dated image, conversations about where a control sits or where flow concentrates get shorter.
A mapped orthomosaic can also give the team a reference for where the disturbance boundary sat on a given day. Measured quantities are a separate deliverable, and any legally required determination belongs to the licensed professionals responsible for it.
What aerial imagery does not do
It does not replace the inspection by a qualified stormwater manager, and it does not certify that a site is in compliance. It cannot show whether silt fence is properly trenched in, or whether an inlet protection device is clogged, the way someone standing next to it can. Flights also depend on weather: wind and precipitation limit when a drone can safely operate, so the window immediately after a storm is not always flyable.
Delivery timing matters too. Dragonfly Aerials delivers within 2–3 business days, so aerial records serve the documentation file and the weekly progress review. They are not a substitute for the same-day field response after a storm.
Setting up a practical routine
Most teams do not need a complicated system. A few habits make aerial imagery useful to the stormwater file:
- Agree with the person who owns the SWMP on how often flights should happen and what views they want, such as the perimeter, the stockpile area, and the outfalls.
- Keep the same flight lines from one visit to the next so images compare directly.
- Name and store files by date, and keep them with the inspection reports rather than in a separate progress-photo folder.
- Add a flight after a major storm when conditions allow, and plan on the delivery window above.
- Tie the monthly flight to the project calendar. Many projects assemble pay draws on or around the 20th, with completed work projected or prorated through month-end. That is common, but not universal, and individual project requirements vary. Where it applies, one set of current, dated flights can serve the draw package and the stormwater file together.
How Dragonfly Aerials approaches it
Dragonfly Aerials is based in Arvada and serves projects across the Colorado Front Range. Founder Mike Brown is a former construction superintendent, so flights are planned around how a site actually runs. Our construction progress documentation service provides recurring flights with consistent angles and time-stamped imagery, and the How It Works page explains planning, capture, and delivery. The services overview shows how documentation connects to mapping and inspection work.
The takeaway
Stormwater compliance rests on inspections and records produced by qualified people. A dated aerial record does not replace either one, but it gives those records a visual backbone. If you want a flight schedule that fits your site and your permit routine, you can request a quote.
Sources
- Colorado Department of Public Health and Environment (CDPHE) — Construction Stormwater Management Plan Guidance (2019 copy hosted by Boulder County)
- CDPHE — Water Quality Construction Compliance Assistance and Guidance
- U.S. EPA — Stormwater Discharges from Construction Activities