Stormwater Management 101
- JRH Engineering & Environmental Services, Inc.
- Oct 1
- 7 min read
New Developments in NC with SWPPP Requirements
JRH Engineering and Environmental Services stands as the premier provider of civil engineering, structural engineering, and environmental engineering services across North Carolina, Florida, and Texas. Effective stormwater management represents one of the most critical aspects of new development projects in North Carolina, requiring careful integration of regulatory compliance, environmental protection, and engineering excellence.
As urbanization continues to reshape the state's landscape, developers, planners, and engineers face increasingly complex challenges in managing stormwater runoff while protecting local waterways and meeting stringent regulatory requirements.
The North Carolina stormwater regulatory framework combines federal mandates under the National Pollutant Discharge Elimination System (NPDES) with state-specific rules administered by the Division of Energy, Mineral, and Land Resources (DEMLR) under the Department of Environmental Quality (DEQ). This comprehensive system addresses everything from Municipal Separate Storm Sewer System (MS4) permits to post-construction stormwater controls, creating a regulatory environment that demands both technical expertise and strategic planning.
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Understanding North Carolina's Stormwater Regulatory Framework
Federal and State Requirements
North Carolina's stormwater program operates under the authority of the Clean Water Act through the NPDES permit system. The state has been delegated authority to implement federal requirements while incorporating additional state-specific protections. This dual-layer approach means that new developments must comply with both federal baseline requirements and North Carolina's enhanced standards for water quality protection.
The regulatory framework encompasses several key programs, including Phase II MS4 permits for communities serving populations under 100,000, construction stormwater permits for sites disturbing one acre or more, and post-construction stormwater management requirements for ongoing pollution prevention. Each program contains specific technical requirements for stormwater control measures (SCMs) and best management practices (BMPs).
Municipal Separate Storm Sewer System (MS4) Requirements
MS4 permits require permittees to develop comprehensive Stormwater Management Programs (SWMPs) that address six minimum control measures: public education and outreach, public participation and involvement, illicit discharge detection and elimination, construction site runoff controls, post-construction site runoff controls, and pollution prevention and good housekeeping.
These programs must include enforceable BMPs with measurable goals and require routine inspections, structural control measure maintenance, and annual reporting. For new developments within MS4 areas, compliance with local stormwater ordinances becomes an additional layer of regulatory requirement that must be addressed during the planning and design phases.
Best Management Practices for New Developments
Structural Control Measures
Structural SCMs represent permanent devices designed, constructed, and maintained to remove pollutants from stormwater runoff. These engineered systems serve as the backbone of post-construction stormwater management, providing long-term water quality protection through various treatment mechanisms including sedimentation, filtration, infiltration, and biological uptake.
Wet Detention Ponds improve stormwater quality by detaining runoff for extended periods, allowing suspended pollutants to settle while providing some nutrient removal through biological processes. These systems require careful design consideration for permanent pool volumes, outlet structures, and emergency spillways to ensure both water quality treatment and flood control.
Bioretention Cells utilize specialized soil media and vegetation to filter stormwater runoff while providing infiltration capacity where soil conditions permit. These systems offer excellent pollutant removal efficiency for sediment, nutrients, and metals while providing aesthetic benefits and potential groundwater recharge.
Dry Detention Basins primarily manage peak flow rates from new development by reducing post-development runoff to pre-development levels for design storm events. While nutrient removal is limited compared to wet systems, dry detention provides essential flood control benefits and can be integrated with recreational facilities or green space amenities.
Low Impact Development Strategies
Low Impact Development (LID) represents an economical and effective strategy for protecting coastal water quality by preventing polluting stormwater runoff. LID seeks to mimic natural hydrology by maintaining the landscape's ability to capture and absorb rain before it becomes polluted runoff. This approach emphasizes preservation of natural drainage patterns, minimization of impervious surfaces, and distributed stormwater management throughout the development.
Rain Gardens and bioswales capture and treat runoff close to its source while providing landscape amenities. These features can be integrated into parking areas, roadway medians, and residential landscaping to provide both functional stormwater treatment and aesthetic value.
Permeable Pavement Systems allow water infiltration through specially designed surfaces, reducing runoff volumes while maintaining structural integrity for vehicular and pedestrian traffic. These systems work particularly well in North Carolina's sandy coastal soils where infiltration rates support effective groundwater recharge.
Green Stormwater Infrastructure
Implementation Strategies
Green Stormwater Infrastructure (GSI) preserves, restores, or mimics natural water cycles through the integration of vegetation, soils, and natural processes. GSI combines elements of the natural environment with traditional drainage systems to improve water quality and restore ecosystem functions while providing multiple community benefits.
The City of Raleigh has emerged as a leader in GSI implementation, requiring evaluation of GSI on City-led projects and promoting installation to reduce stormwater runoff, improve water quality, and provide ecological benefits. This municipal leadership demonstrates the growing recognition of GSI as a cost-effective approach to comprehensive stormwater management.
Bioretention Areas along roadways manage flow and remove pollution before reaching storm drains and streams. These systems can be integrated into streetscape design to provide both functional stormwater treatment and urban amenities including improved air quality, urban heat island reduction, and enhanced property values.
Economic Benefits
LID and GSI approaches often provide significant cost savings compared to conventional stormwater management approaches. Case studies demonstrate that eliminating traditional curbs, gutters, and stormwater ponds while implementing distributed LID practices can reduce infrastructure costs by hundreds of thousands of dollars per project while providing superior environmental performance.
The economic benefits extend beyond initial construction savings to include reduced long-term maintenance costs, improved property values, and potential regulatory compliance advantages. These systems also provide co-benefits including enhanced community aesthetics, recreational opportunities, and ecosystem services that add value beyond their stormwater management function.
Construction Stormwater Management and SWPPP Development
NPDES Construction Permits
The NPDES Construction Stormwater Program applies to construction activities disturbing one acre or more, or activities that are part of a common plan of development exceeding one acre. These permits require comprehensive pollution prevention planning and implementation throughout the construction phase to prevent sediment and other pollutants from entering surface waters.
Stormwater Pollution Prevention Plans (SWPPPs) serve as the cornerstone of construction stormwater management, documenting site-specific conditions, potential pollutant sources, and control measures to minimize water quality impacts. Professional engineers experienced in SWPPP development ensure that these plans meet all regulatory requirements while providing practical, implementable pollution prevention strategies tailored to site-specific conditions.
Erosion and Sediment Control
Effective erosion and sediment control during construction phases requires integration of temporary and permanent control measures designed to minimize soil disturbance and capture sediment before it reaches surface waters. This includes proper sequencing of construction activities, installation and maintenance of sediment barriers, and stabilization of disturbed areas according to regulatory timelines.
Temporary Control Measures including silt fences, sediment basins, and construction entrances must be properly designed, installed, and maintained throughout the construction period. Regular inspections and maintenance of these systems ensure continued effectiveness and regulatory compliance during all weather conditions.
Civil and Structural Engineering Considerations
Design Standards and Specifications
Professional civil engineers play a crucial role in stormwater management system design, ensuring that proposed systems meet all applicable performance standards while integrating effectively with other site infrastructure. This includes hydrologic and hydraulic modeling, structural design of control measures, and preparation of construction documents that communicate design intent to contractors and regulatory reviewers.
Hydrologic Analysis using accepted methodologies such as the Rational Method and NRCS Curve Number approach provides the foundation for proper system sizing and performance verification. These analyses must account for both current conditions and future development scenarios to ensure long-term system adequacy.
Structural Design of stormwater control measures requires consideration of soil conditions, groundwater levels, structural loads, and construction access requirements. Professional structural engineers ensure that proposed systems can withstand design loads while maintaining structural integrity throughout their design life.
Permit Coordination and Regulatory Compliance
Successful stormwater management projects require careful coordination with multiple regulatory agencies and permit programs. This includes local development review processes, state stormwater permits, federal wetlands permits where applicable, and ongoing compliance with post-construction maintenance and reporting requirements.
Professional Engineering Certification provides assurance that proposed systems meet all applicable design standards and regulatory requirements. Licensed professional engineers take responsibility for design adequacy and regulatory compliance, providing developers with confidence in their stormwater management investments.
Maintenance and Long-Term Performance
Operation and Maintenance Requirements
Stormwater control measures require ongoing inspection and maintenance to ensure continued performance throughout their design life. Property owners must develop and implement comprehensive maintenance programs that address both routine maintenance activities and major rehabilitation needs over the system's operational period.
Annual Inspections by qualified professionals ensure that systems continue to function as designed while identifying maintenance needs before they become major problems. These inspections must be documented and reported to regulatory agencies as required by permit conditions.
Maintenance Planning should address both short-term operational needs and long-term capital replacement requirements. Professional engineering services can provide lifecycle cost analysis and maintenance scheduling to optimize system performance while minimizing ownership costs.
Performance Monitoring
Effective stormwater management programs include provisions for monitoring system performance and making adaptive management decisions based on observed conditions. This may include water quality monitoring, flow measurements, and vegetation assessments to verify that systems continue to meet their design objectives.
Conclusion
Effective stormwater management for new developments in North Carolina requires comprehensive understanding of regulatory requirements, technical design principles, and long-term maintenance considerations. The integration of traditional structural controls with innovative LID and GSI approaches provides opportunities to achieve superior environmental performance while potentially reducing project costs and enhancing community amenities.
JRH Engineering and Environmental Services, as the premier provider of civil engineering, structural engineering, and environmental engineering services in North Carolina, Florida, and Texas, brings the expertise and experience necessary to navigate these complex requirements successfully.
Our comprehensive approach ensures that stormwater management systems not only meet current regulatory requirements but also provide long-term value through superior design, construction oversight, and maintenance planning. By working with experienced professionals who understand both the technical and regulatory aspects of stormwater management, developers can transform their vision into reality while protecting North Carolina's valuable water resources for future generations.
References:
Freese & Nichols. “Stormwater Regulation in North Carolina: A Guide to MS4 Permits.” Freese.com, published September 28, 2025.
North Carolina Department of Environmental Quality. “Permittees & Permit Requirements.” NC DEQ Stormwater Program.
City of High Point, NC. “Phase II Stormwater Program.” HighPointNC.gov.
North Carolina Geological & Topographic Survey. “Stormwater Management Plan.” stormwater-management-plan.pdf.
U.S. Environmental Protection Agency. “Stormwater Discharges from Construction Activities.” EPA.gov, updated June 12, 2025.
North Carolina Department of Environmental Quality. “NPDES Construction Program.” DEMLR Stormwater Program.
City of Durham, NC. “Green Infrastructure.” DurhamNC.gov, published January 31, 2025.
North Carolina Coastal Federation. “Low-Impact Development.” NCCoast.org, updated January 4, 2024.
North Carolina Coastal Federation. “Low-Impact Development: A Guidebook for North Carolina.” nccoast.org/uploads/documents/guides/LIDNC.pdf.
Wake County, NC. “Stormwater Control Measures.” Wake.gov, updated June 3, 2025.
City of Greensboro, NC. “Stormwater Control Measures (SCMs).” Greensboro-NC.gov.
North Carolina Department of Environmental Quality. “3. Stormwater Calculations.” DEQ NC Surface Water Protection Unit.
North Carolina Department of Transportation. “Stormwater Control Inspection and Maintenance Manual.” NCDOT.
City of Durham, NC. “Owner’s Maintenance Guide for Stormwater BMPs.” DurhamNC.gov.
High Point, NC. “Stormwater BMP Maintenance General Guidelines.” City of HighPointNC.gov.
City of Raleigh, NC. “City of Raleigh Stormwater Management Design Manual.” RaleighNC.gov.
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