This voluntary program enables local governments to adopt and administer a model stormwater program within their jurisdictions that is simpler to understand and administer while also providing an enhanced level of protection from stormwater runoff from development. Under the USMP, a local government can meet the mandates for a wide variety of different stormwater programs with just a single set of requirements.
The Universal Stormwater Management Program is unique for a number of reasons.
First, it is intended to replace a number of existing stormwater control programs, all of which have differing and, sometimes, confusing requirements, with a single, simplified set of stormwater control measures. For more information about how the USMP will simplify stormwater control requirements check out the 'Examples' tab above for before and after maps.
Secondly, the USMP will be more protective of North Carolina’s natural environment than the existing stormwater programs it will replace. So, not only will the USMP be simpler to understand and to implement, but it will also better protect North Carolina’s lakes, rivers, streams, sounds, estuaries, and coast for future generations.
Finally, the USMP is truly unique because it is optional. North Carolina’s local governments (cities and counties) that currently administer stormwater control programs within their jurisdiction will have the option of retaining their existing programs or implementing the USMP. Because the USMP is optional it will only be successful if it is able to gain support at the local level. The optional nature of this program represents a significant departure from DWQ’s normal method for implementing new environmental quality programs and provides the local communities with a greater voice in determining the environmental future of their local area.
Why Do We Need the USMP?
USMP Advantages To:
The Universal Stormwater Management Plan requirements will consist of two major components: a design standard for stormwater control and a setback requirement. These are the two minimal components that are needed for any effective stormwater control strategy.
Design Standard for Stormwater Control:
This is the element of the USMP that will mandate some form of control and treatment of stormwater run-off. This requirement will differ slightly depending upon whether the covered activity is located in one of the 20 Coastal Counties.
Design Standard for Non-Coastal Counties:
If the covered activity is located in one of the 80 non-Coastal Counties all residential development disturbing one acre or more and all commercial development disturbing ½ acre or more will require the control and treatment of the stormwater run-off generated by a 1” (one inch) rain event. At a minimum, these stormwater control and treatment measures must be capable of removing 85% of the Total Suspended Solids (TSS) and must have a volume drawdown of at least 48 hours, but not more than 120 hours. *In addition, the storage volume of the stormwater control device must be discharged at a rate equal or less than the pre-development discharge rate for the 1-year, 24-hour storm. *Furthermore, new development within the critical areas of water supply watersheds is limited to an impervious surface density of no more than 36 percent.
Design Standard for Coastal Counties:
Development activities located in one of the 20 Coastal Counties that disturb more than 10,000 square feet will require the control and treatment of the stormwater run-off generated by a 1.5” (one and one half inch) rain event. As required for the non-Coastal Counties, these stormwater control and treatment measures must be capable of removing 85% of the Total Suspended Solids (TSS) and must have a volume drawdown of at least 48 hours, but not more than 120 hours. *In addition, the storage volume of the stormwater control device must be discharged at a rate equal or less than the pre-development discharge rate for the 1-year, 24-hour storm. *Furthermore, new development within 575 feet of shell fishing waters is limited to an impervious surface density of no more than 36 percent.
Map of Design Standard Requirement:
All effective stormwater control strategies must include some form of mandatory “setback” for impervious surfaces from the closest receiving waters. Accordingly, the USMP will include two setback requirements: one for the Coastal Counties and one for the non-Coastal Counties.
Setback for Non-Coastal Counties:
For those areas covered under the USMP in the 80 non-Coastal Counties no new impervious surfaces will be allowed within the 100 year floodplain (as delineated by the NC Division of Emergency Management), except for roads, paths and water dependent structures. For those perennial and intermittent streams in the non-Coastal Counties that do not have a NC DEM delineated floodplain, no new impervious surfaces (except for roads and water dependent structures) shall be allowed within 30 feet.
What is the 100 Year Floodplain? The 100 year floodplain is also termed the 1% annual chance floodplain. This area is delineated as the Special Flood Hazard Area on the Flood Insurance Rate Maps (FIRM) maintained by the NC Floodplain Mapping Program in the Division of Emergency Management. FIRM maps exist for all of North Carolina and can be viewed online. For further information on the 100 year flood plain, or to view the delineated floodplain for a specific area visit www.ncfloodmaps.com.
Why use the 100 Year Floodplain? The 100 Year Floodplain was chosen as the setback for the non-Coastal Counties for a variety of compelling reasons. The National Flood Insurance Program (NFIP) already mandates a number of restrictions on development in the floodplain and these restrictions have already been adopted by 98 counties and 367 municipalities in NC. Additionally, a large infrastructure already exists within DEM to maintain and update the floodplain maps on a regular basis. Perhaps one of the most important reasons is that restricting new impervious surfaces within the 100 year floodplain might help to alleviate the significant flooding issues that are occurring statewide with greater and greater frequency. Furthermore, restricting development in the floodplain protects water quality, protects lives and property, and would also address a number of other significant economic and insurance issues. In short, restricting development in the 100 year Floodplain appears to be sound public policy.
Setback for Coastal Counties:
For those areas where local governments adopt the USMP in the 20 Coastal Counties there will be a mandatory 30 foot setback for impervious surfaces from all surface waters of the State, except for roads, paths and water dependent structures.
Why not use the 100 Year Floodplain for the Coastal Counties? The coastal floodplain is expansive and often covers a mile or more in many areas in the Coastal Counties. This makes it impractical and unreasonable for use as a setback.
Map of Setback Requirement:
Examples of Before & After Implementing the USMP
Durham County could be considered a “poster county” for the adoption of the Universal Stormwater Management Program. With the advent of the Phase 2 program, 100% of Durham County is presently covered by some form of stormwater control plan. Unfortunately, as depicted in the map, there are 8 different programs in place within the county. Every one of the colors on the map represents a different set of requirements (density requirements and setbacks) that must be implemented in that area. By studying the map below, it is easy to understand how this current situation creates great difficulties and confusion for local government officials, builders, developers, and private citizens. Under the USMP, Durham County would have just one program and a single set of requirements for the entire county. Furthermore, the USMP would be more protective of Durham’s natural environment than all these existing programs.
In the case below, Montgomery County does not have 100% coverage of stormwater control programs, but it does have 6 different programs within its boundaries, all with differing requirements. As with Durham County, if the USMP were implemented throughout all of Montgomery County there would be only one set of stormwater requirements, as depicted in the “after USMP” slide. Note that those areas in the county that were not covered by a stormwater program “before” the USMP implementation, remain without coverage “after” USMP adoption. Adoption of the Universal Program will not establish stormwater controls where none currently exist. Furthermore, not only would the USMP simplify stormwater requirements in the county, but it would also be more protective of Montgomery County’s natural environment.
Rule & Model Ordinance
USMP Requirements Summary