Env 247 Overview of Stormwater Management March 1, 2011

Sources of Stormwater Runoff 1.Sheet flow over impervious surfaces or other structures 2.Runoff including agriculture, urban areas, construction, and forestry 3.Municipal Stormwater Management Systems  Large, small, and urban municipal separate storm sewer systems (MS4s) 4.Industrial Facilities/Activities 5.Construction Activities

Managing Stormwater Discharges through the National Pollutant Discharge Elimination System (NPDES) Permit 1.Point Sources that discharge into waterways are subject to permitting requirements – Municipal Stormwater Collections Systems including MS4s Certain industrial discharges Other outfalls that directly discharges into waterways 2.Non-point Sources are subject to “general permits” Stormwater runoff due to construction activites

Typical Stormwater Outfall –Point Source

A Case Study – Managing Stormwater Runoff from a Constructon Site Pollutants Commonly Discharged from Construction Sites 1.Sediment 2.Solid and sanitary wastes 3.Phosphorous (fertilizer) 4.Nitrogen (fertilizer) 5.Pesticides 6.Oil & grease 7.Concrete truck washout 8.Construction chemicals 9.Construction debris

A Case Study – Managing Stormwater Runoff from a Constructon Site – Permitting System US EPA has issued a “general permit” that authorizes the discharge of pollutants in stormwater discharges associated with construction activity that disturbs one acre or more of land. Site owners must submit a Notice of Intent (NOI) to operate under the “general permit” In NC, site owners can submit a “land disturbance permit” application in lieu of an NOI that contains methods to comply with the general permit requirements.

Content of Land Disturbance Permits Land disturbance permits contain administrative requirements consistent with the requirements outlined in the General Permit, including: 1. Equipment operation & maintenance practices to avoid the release of fuels, lubricants, etc. onto the ground; 2. Material handling practices regarding the use of pesticides, herbicides and fertilizers; 3. Building material waste handling; 4. Litter & sanitary waste handling; 5. Monitoring & reporting requirements; and, 6. Site inspection requirements.

Best Management Practices (BMPs) to Prevent Erosion and Sediment Runoff Erosion controls designed to either: (1)prevent erosion through protection and preservation of soil or (2)prevent sediment runoff before the runoff is discharged from the site include: Stabilization Practices Structural Practices

Example of sedimentation entering a storm drain

Best Management Practices - Stabilization Stabilization reduces erosion potential by (1) intercepting water so that it infiltrates into the ground instead of running off the surface and (2) slowing the velocity of runoff, thereby promoting deposition of sediment and includes such practices as: 1. Temporary seeding 2. Permanent seeding 3. Mulching 4. Sod stabilization 5. Vegetative buffer strips 6. Contouring and protection sensitive areas

Best Management Practices - Structural Practices Structural Practices involve the installation of devices to divert, store, or limit runoff to prevent water from flowing on disturbed areas where erosion may occur, and include: 1. Earth dikes 2. Silt fences 3. Drainage swales 4. Check dams 5. Pipe slope drains, 6. Temporary stormwater diversions

Stormwater Management Stormwater management measures are measures applied to reduce pollutants in stormwaster discharged from the site after completing construction activities, and include: 1.Onsite infiltration of runoff 2.Flow attenuation by vegetation or natural depressions 3.Outfall velocity dissipation devices 4.Stormwater retention basins 5.Artificial wetlands 6.Stromwater detention structures.