DEState-AdministeredSWPPP Requirements in Delaware
Delaware operates one of the most protective construction stormwater programs on the East Coast, driven by its small size and the sensitivity of its two major watershed systems: the Delaware Inland Bays and the Chesapeake Bay tributaries in Sussex County. The state's 5,000 square foot disturbance threshold—far below the federal 1-acre standard—means virtually any meaningful grading or earthwork requires NPDES permit coverage and a certified inspector on every inspection. Delaware's flat coastal plain topography and proximity to tidal waters means that nearly every construction project discharges to a sensitive receiving body within a short drainage path. The Inland Bays (Rehoboth, Indian River, and Little Assawoman Bays) are designated Outstanding Resource Waters with strict nitrogen and phosphorus loading limits that directly affect allowable construction discharges. Contractors unfamiliar with Delaware's lower threshold frequently discover mid-project that they needed DNREC coverage for a project they assumed was too small to qualify.
Delaware SWPPP Key Facts
- ✓5,000 square foot disturbance threshold—significantly lower than the federal 1-acre standard
- ✓DNREC-certified Sediment and Stormwater Inspector required for all construction site inspections
- ✓Inland Bays (Rehoboth, Indian River) designated Outstanding Resource Waters with strict nutrient loading limits
- ✓Small state means almost every project is near tidal or sensitive freshwater resources
- ✓County-level sediment and stormwater plans required in addition to state NPDES coverage
Administering Agency
- Agency
- Delaware Department of Natural Resources and Environmental Control (DNREC)
- Phone
- 302-739-9946
- dnrec@delaware.gov
- Website
- DNREC Stormwater Program
Permit Details
- Permit Name
- NPDES General Permit for Stormwater Discharges from Construction Activities
- Permit Number
- DER11
- Effective Date
- 2019-03-01
- Permit Document
- View Current Permit
SWPPP Thresholds & Triggers
- Acreage Threshold
- 5,000 square feet or more of land disturbance (lower than the federal 1-acre threshold)
Delaware's 5,000 sq ft threshold is significantly more stringent than the federal standard. Inland Bays watershed protection areas and Chesapeake Bay tributary watersheds impose additional sediment and nutrient controls. Coastal construction near tidal waters requires coordination with Army Corps of Engineers Section 404/10 permits.
Inspection Requirements
- Inspection Frequency
- At least once every 7 calendar days and within 24 hours of a qualifying storm event
- Rain Event Threshold
- 0.5 inch in a 24-hour period
- Certified Inspector
- Required by state
- Accepted Certifications
- Delaware Sediment and Stormwater Inspector certification, CPESC, CESSWI
Delaware requires a DNREC-certified Sediment and Stormwater Inspector to perform construction site inspections. This is more stringent than many states and requires personnel to complete DNREC-approved training. The small state geography means most projects are within a short drive of tidal or sensitive freshwater resources.
Penalties & Enforcement
- Max Civil Penalty (Per Day)
- $10,000 per day per violation
- Criminal Penalties
- Criminal penalties under 7 Del. C. §6013 for willful or negligent violations
DNREC actively inspects construction sites and coordinates with county governments on sediment and stormwater enforcement. Violations near the Inland Bays or Chesapeake tributaries draw swift enforcement response.
Permit Fees
- NOI Filing Fee
- $0
- NOT Filing Fee
- $0
- Other Fees
- Sediment and Stormwater Plan review fees vary by county and project size.
How Delaware Differs from Federal Requirements
- ⚠5,000 sq ft threshold is dramatically more stringent than the federal 1-acre standard—this is the most important Delaware-specific difference.
- ⚠Certified inspector requirement (DNREC certification) goes beyond federal CGP qualified person standard.
- ⚠Inland Bays Outstanding Resource Waters designation imposes nutrient discharge restrictions with no direct federal CGP equivalent.
SWPPP Tips for Delaware
- ➤Apply the 5,000 sq ft threshold from day one of project planning—many Delaware contractors are surprised that small commercial pads and residential subdivisions trigger full NPDES coverage.
- ➤Hire or contract with a DNREC-certified Sediment and Stormwater Inspector before mobilizing—this is a permit requirement, not optional.
- ➤For Sussex County projects draining to the Inland Bays, review the Delaware Inland Bays TMDL and ensure your SWPPP addresses nutrient loading beyond basic sediment controls.
- ➤Army Corps coordination for any coastal or tidal work should begin 6+ months in advance—Section 404/10 permit timelines in Delaware can be lengthy.
Delaware SWPPP FAQs
Why does Delaware's threshold start at 5,000 square feet instead of 1 acre?+
Delaware adopted a more protective threshold due to the state's small size, coastal sensitivity, and dense network of tidal and freshwater resources. The 5,000 sq ft threshold has been state law for decades and applies to virtually all significant grading or earthwork activity.
What is a DNREC-certified Sediment and Stormwater Inspector?+
A person who has completed DNREC-approved training and certification to conduct construction site stormwater inspections in Delaware. Certification is required to perform the periodic site inspections mandated by the permit—general CPESC or CESSWI credentials alone may not satisfy this requirement without DNREC approval.
Do I need both a county sediment plan and a state NPDES permit?+
Yes in most cases. Delaware's three counties (New Castle, Kent, Sussex) each require county-level Sediment and Stormwater Management Plan approval before grading permits are issued. The state NPDES DER11 permit coverage is a separate, concurrent requirement.
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