Delaware Stormwater & Erosion Control

The short version

• DNREC runs the program. The Delaware Department of Natural Resources and Environmental Control administers sediment and stormwater regulation through its Sediment and Stormwater Program.
• Land disturbance above the threshold triggers the rules. Construction and grading work that disturbs land above Delaware's statutory threshold requires an approved Sediment and Stormwater Plan before work begins.
• NPDES coverage for stormwater discharges. Construction activities that discharge stormwater are covered under Delaware's NPDES program, administered by DNREC under authority of the federal Clean Water Act.
• Notice of Intent (NOI) must be filed for covered construction stormwater discharges.
• Design standards live in the Delaware Erosion and Sediment Control Handbook and the Post-Construction Stormwater BMP Standards and Specifications.
• Certification courses are available for contractors, site managers, and inspectors working on covered projects.

Where to go — primary sources

• DNREC Drainage and Stormwater hub — the authoritative landing page for DE sediment and stormwater regulation.
• Sediment and Stormwater Program — program-specific resources, forms, plan-review contacts.
• Delaware Erosion and Sediment Control Handbook — the technical design manual. Accessed from the DNREC hub.
• Post-Construction Stormwater BMP Standards and Specifications — permanent BMP design standards. Accessed from the DNREC hub.
• Notice of Intent (NOI) for construction stormwater discharges — the NPDES filing; form linked from the DNREC hub.
• 7 Del. Code, Chapter 40 — the governing statute for Delaware's sediment and stormwater program.

When do the rules trigger?

Delaware's sediment and stormwater requirements generally apply to construction and grading activities that disturb land above the statutory threshold and to certain categories of post-construction site alteration. The exact current threshold, the list of exempt activities, and the definition of "land disturbance" should be verified directly against the current regulations and the DNREC program page. Thresholds have been adjusted over time, and specific project categories (agricultural, forestry, certain linear utilities) may be handled separately.

What a typical covered project has to do

1. Prepare a Sediment and Stormwater Plan meeting the Erosion and Sediment Control Handbook and BMP Standards.
2. Submit the plan for DNREC review (or, where delegated, the appropriate delegated agency — some plans are reviewed by delegated county or conservation-district staff).
3. File a Notice of Intent (NOI) under NPDES for stormwater discharges associated with construction activity.
4. Install the perimeter controls and temporary BMPs before beginning land disturbance.
5. Maintain and inspect BMPs throughout construction, per the approved plan and the regulations.
6. Install permanent post-construction BMPs per the BMP Standards for long-term stormwater management.
7. File a Notice of Termination (NOT) at project closeout to end NPDES coverage.

Who reviews the plan

Delaware uses a delegated review system. DNREC's Sediment and Stormwater Program retains direct review for certain project categories, but much of the review capacity is delegated to county conservation districts and some municipal programs. Which entity reviews your plan depends on location, project type, and current delegation agreements. The DNREC program page is the best starting point for identifying the correct reviewing agency.

Certification courses

DNREC publishes a list of approved certification courses for construction site managers, responsible personnel, and inspectors. For projects above certain thresholds, having certified personnel on site is required. Course listings and approved providers are published on the DNREC hub.

How Delaware differs from neighboring states

• Delegated review. DE uses conservation districts and delegated agencies for much of plan review. Other states centralize more heavily at the state level (MDE in Maryland is notably more centralized).
• Integrated program. Delaware's sediment-and-stormwater program is unified; some states separate sediment/erosion rules from post-construction stormwater rules, which can create coordination gaps.
• NPDES construction general permit. Delaware runs its NPDES program under delegation from EPA, similar to neighboring states but with Delaware-specific forms, fees, and timelines.

Common pitfalls

• Starting land disturbance before plan approval. Do not begin earthwork on the expectation that approval is coming — DNREC and delegated agencies take enforcement action on premature grading.
• Underestimating the review timeline. Plan submission, review comments, revisions, and resubmission can take weeks. Build this into the project schedule upstream.
• Missing NOI filing. The construction general permit is not automatic; the NOI is the contractor's affirmative filing and it must be done before ground disturbance.
• Inadequate BMP maintenance during construction. Failed silt fence or clogged sediment basins invite stop-work orders; BMP maintenance is not optional.
• Treating post-construction BMPs as a design afterthought. Permanent BMPs have design standards that drive site layout — plan for them during civil design, not at closeout.

The practical workflow

1. Determine coverage: does the project disturb more than the statutory threshold?
2. Identify the reviewing agency (DNREC or delegated county/conservation district).
3. Design sediment/erosion and post-construction BMPs per the Handbook and BMP Standards.
4. Submit the Sediment and Stormwater Plan for review; revise per comments.
5. File NOI for NPDES construction general permit coverage.
6. Install perimeter controls and temporary BMPs before any earthwork.
7. Maintain and inspect throughout construction; document inspections.
8. Install permanent BMPs per the approved plan.
9. File NOT at project closeout.

When to get direct help

For coverage questions or plan-review questions, DNREC's Sediment and Stormwater Program is the right first call. For delegated-review jurisdictions, the relevant county conservation district handles day-to-day plan review. Contact details are on the DNREC hub page linked above.

Why we built this

Delaware contractors working across counties (and cross-state contractors from PA / NJ / MD) routinely miss which agency reviews their plan or underestimate the review timeline. This page surfaces the primary sources and the actual workflow so contractors can plan properly — especially for projects near county boundaries where the reviewing agency can be non-obvious.

Missing something? Email us.