Does my dewatering discharge need turbidity monitoring?
Part 3.3 applies when dewatering water is discharged to a sensitive water — one listed as impaired for sediment or a sediment-related parameter, designated Tier 2, 2.5 or 3, or within Lands of Exclusive Federal Jurisdiction — and the benchmark is 50 NTU compared against a weekly average.
The comparison is weekly, not per sample
Part 3.3.3 compares the weekly average of the turbidity results against the 50 NTU benchmark. A single high reading is not by itself an exceedance, and a run of moderate ones can be — which is the opposite of how most people assume it works.
Where it applies, Part 7.2.8 requires the monitoring procedures to be written into the SWPPP, and the sampling points to be marked on the site map (Part 7.2.4).
If it applies, read the clause in full
Sampling method, meter calibration, quarterly reporting deadlines and the corrective action that follows an exceedance (Part 5.2.2, logged under Part 5.4) are all specified. This page is a pointer, not a substitute.
Questions people ask
- What if I add dewatering after the plan is written?
- The plan has seven days to catch up (Part 7.4.1). Start with the monitoring section.
- Does SwpppDraft do the monitoring maths?
- No. It writes the procedure and the thresholds into the plan with their clause numbers; the sampling, the averaging and the reporting are yours.
The states this question turns on
- Washington SWPPP requirements — Washington requires the permittee to prepare the SWPPP; the Certified Erosion and Sediment Control Lead requirement applies to site inspections.
- Oregon SWPPP requirements — Oregon small sites can self-prepare by default; a stamp by a CPESC, CPSWQ, PE, RLA or CEG is required only when the site disturbs 20 acres or more, when a non-standard buffer compliance option is used because water is within 50 feet, or when an engineered sediment basin or erosion management plan is built.
- Florida SWPPP requirements — Florida asks only that the SWPPP follow standard industry practices; it names no preparer qualification.
The documents this affects
Other questions
- Who can prepare a SWPPP?
- Which states require a licensed professional to prepare a SWPPP?
- Which states make you take a course before writing a SWPPP?
- Does my site need a licensed professional even though my state allows self-preparation?
- What acreage thresholds change SWPPP requirements?
Check your state and build a draft
The questionnaire and the generator run in your browser. Checkout is not open, so nothing can be charged.
Source: EPA 2022 Construction General Permit (as modified), Part 3.3, read 2026-08-04. County and city rules are not covered.
What we are, and what stays your responsibility
- SwpppDraft is a document generation tool. It does not provide engineering services, legal services, or compliance consulting, and no engineer or attorney reviews what it produces.
- Everything in the document is built from the site facts you enter. Checking that those facts are right, and that the resulting plan fits your project, is yours to do.
- We do not file anything on your behalf, we do not certify or endorse your compliance, and we accept no liability for what happens when you use the document.
- State-level requirements carry the date we verified them. County and city rules are not covered — some local jurisdictions require a licensed preparer even where the state does not, and you have to check that yourself.
- When the product opens, our total liability will be capped at the amount you paid us. Today that amount is zero, because nothing is for sale.