Sediment Basin Volume
Storage for a construction sediment basin under the Texas Construction General Permit: 2-year, 24-hour runoff from each disturbed acre, with Atlas 14 rainfall.
Results
Enter your values; the answer appears here as you type.
- The permit
- TXR150000 (effective March 5, 2023), Part III.F.2(c): storage for a calculated volume of runoff from a 2-year, 24-hour storm from each disturbed acre drained, at a common drainage location serving ten or more acres disturbed at one time.
- The calculation
- The permit names no method. This page uses the NRCS curve number equation with the 24-hour NOAA Atlas 14 depth at the site, or a depth you enter: volume = Q × area.
- 3,600 cubic feet per acre
- The permit’s figure where rainfall data is not available or a calculation cannot be performed. It is not a free choice: the page asks which reason applies and prints it on the sheet.
The calculator is tested against the cases below every time its code changes.
| Case | What | Reference | Values compared | Largest difference | Result |
|---|---|---|---|---|---|
| The table loads with the calculator. The same results are in verification.json. | |||||
A hand calculation of the curve number equation and the NRCS TR-55 example. The permit prints no worked example.
- Volume only: no basin shape, outlet, dewatering time or sediment storage. The permit asks for outlets that withdraw from the surface unless infeasible, and for the calculations in the SWP3.
- Offsite and stabilized flows may be left out only if they are diverted around the disturbed area and the basin. Flows that are not diverted are not computed here.
- The permit’s calculated rule says each disturbed acre drained, and its 3,600 rule says each acre drained. Read the permit for your site; TCEQ began renewing it in 2026, and the current one runs to March 5, 2028.
- Whether a basin is feasible, and equivalent controls when it is not, are yours to document under the permit. This page does not address them.
- Which curve number do I use?
- One for the disturbed site. TR-55 lists newly graded areas, in the Curve numbers tab of the NRCS Runoff calculator.
- Under ten acres?
- The permit makes a basin one option there, with the same volume rule (Part III.F.2(c)ii). The page still gives the volume and notes it.
- Can I attach the calculation sheet to my SWP3?
- You can print it and include it as a supporting calculation that you have checked. It is a calculation aid, not a sealed engineering document.
| Topic | Reference |
|---|---|
| Permit | Texas Commission on Environmental Quality, Construction General Permit TXR150000, effective March 5, 2023, Part III.F.2(c) and Part IV.F. |
| Runoff | USDA NRCS (1986). TR-55, 2nd ed., Chapter 2. |
| Rainfall | NOAA Atlas 14 Volume 11, Texas. |
Need an engineer’s review of this calculation?
HERO E&C prepares drainage and floodplain studies, channel and culvert design, HEC-HMS / HEC-RAS models, and development permit applications across Texas.
A free calculation aid using the published methods above. Not a sealed engineering document; the engineer of record is responsible for design. HERO E&C · TBPELS Firm F-27793.
Full disclaimer
A free calculation aid. This calculator applies the published methods named on this page to the inputs you enter. It is not a sealed engineering document, has not been reviewed by a licensed professional for your project, and no warranty is expressed or implied. Check the results independently before using them for design, bidding or permitting.
The criteria of the reviewing agency decide which methods and values apply to a design. The engineer of record is responsible for the design.
Using this calculator does not create an engineer–client relationship. Calculations run in your browser; your inputs are not sent to or stored by HERO E&C. HERO E&C · TBPELS Firm F-27793.