A Site Design Adjustment after the first round of agency comments is so common that experienced developers plan for it before submission even happens. One specific change shows up more than any other. It’s a shift in how stormwater gets handled on site. This usually happens because the first design didn’t fully match a requirement the reviewing agency cares about most.
Knowing this ahead of time means you can avoid it. Or at least you won’t be surprised when it shows up.
The Comment That Shows Up Almost Every Time
Reviewing agencies see hundreds of site plans a year. They know exactly where developers tend to cut corners. Stormwater management sits near the top of that list.
The most common comment sounds something like this: the proposed detention or retention system doesn’t meet the required release rate. Or the drainage area used in the calculation doesn’t match what the agency’s own mapping shows for that parcel.
This single comment can force a redesign of pond size, pipe routing, and sometimes grading across a large section of the site.
Why This Keeps Happening on First Submittals
This comment repeats across projects for a simple reason. Many first-draft site plans size stormwater systems off the site’s own acreage. They don’t confirm the full watershed the agency actually uses in its review.
Agencies often keep their own mapping and drainage basin data. That data doesn’t always match a developer’s assumed drainage boundary. When the site plan and the agency’s data disagree, the agency wins that argument every time. The design has to change to match their numbers, not the other way around.
What Actually Changes When This Comment Comes Back
Once this comment lands, a few things typically happen at once.
- The detention or retention pond gets resized, usually larger than the original design
- Pipe routing changes to accommodate the new pond location or size
- Grading shifts to fit the larger stormwater footprint without losing parking or building area
- In some cases, the building footprint itself gets pulled in to make room
None of these changes happen alone. A bigger pond needs more land. That often means less land for something else on a site that was probably already tight on space.
The Faster Way Through This Comment
Developers who avoid this delay usually do one thing differently. They request the agency’s own watershed and drainage basin data before finalizing a design, not after.
Most agencies will share this information if asked directly. Sometimes it comes through a public GIS portal. Sometimes it takes a direct request to the review department. Comparing this data against your engineer’s assumptions before submittal catches the mismatch early. At that stage, it’s a design adjustment instead of a resubmittal.
A Second Comment That Often Travels With the First
Stormwater comments rarely show up alone. A second, related comment often follows close behind. The erosion control plan doesn’t match the revised grading, because the original erosion control plan was based on the first drainage layout.
This is a downstream effect. Fix the stormwater design, and the erosion control plan needs updating too. It depends on where grading actually directs water during construction. Missing this connection means submitting a stormwater fix that still gets flagged, just for a different reason.
Why This Isn’t Just an Engineering Problem
This comment cycle affects more than just the civil engineer’s drawings. A resized pond can shrink usable land for parking or building footprint. That affects the client’s program directly.
A shifted timeline affects financing draws. It affects contractor mobilization dates. Sometimes it affects lease commitments tied to a projected opening date. Developers who treat this as purely a technical issue for the engineering team to handle often miss how much it can ripple into the rest of the project schedule.
What This Looks Like on a Real Project
Picture a mixed-use site where the first stormwater design gets sized off the property boundary alone. The engineer submits the plan, confident the numbers work.
Three weeks later, the agency comes back. Their mapping shows an additional two acres of offsite land draining onto the parcel from a road improvement project built five years earlier. Nobody on the design team knew about it, because it wasn’t obvious from a site walk or an aerial photo.
Now the pond needs to grow to handle that extra flow. The grading plan shifts to make room. The erosion control plan gets updated to match. What could have been a five minute phone call to the agency before submittal turns into a six week delay after it.
What to Ask Before Your First Submittal Goes In
Before a site plan goes to the reviewing agency, confirm these details with your engineering team.
- Has the drainage area been checked against the agency’s own watershed mapping, not just the site’s own acreage?
- Does the stormwater release rate match what the jurisdiction actually requires, not an assumed standard rate?
- Has the erosion control plan been built around the current grading plan, not an earlier version?
Answering these before submittal is far faster than answering them in a resubmittal three months later.
Plan for the Comment, Don’t Just React to It
The stormwater and drainage comment is common enough that it shouldn’t come as a surprise. Developers who check their watershed assumptions against agency data before submittal often skip this delay entirely. Those who don’t usually end up making the same design adjustment anyway. They just make it later, with a schedule that’s already slipped.
Frequently Asked Questions
Why do stormwater comments frequently come up during permit review?
Many initial stormwater designs are based only on the property’s acreage instead of the full watershed used by the reviewing agency. This difference often results in requests for revisions.
What typically changes after a stormwater review comment is issued?
Revisions may include detention pond sizing, pipe alignments, grading plans, and, in some cases, the building footprint to meet stormwater management requirements.
How can developers reduce the likelihood of stormwater review comments?
Obtain the reviewing agency’s watershed and drainage basin information early, and compare it with the engineer’s design assumptions before submitting plans.
Why are erosion control plans often revised with stormwater plans?
Erosion control measures are based on the approved grading plan. When stormwater revisions change grading, the erosion control plan must also be updated to remain consistent.
Can stormwater review comments affect more than the engineering plans?
Yes. Changes to a stormwater system can reduce buildable area, affect parking layouts, alter building footprints, and impact project schedules, financing, and construction mobilization.