Stonnwater and Sediment 



Section 320.2 D. 



1. Discharging runoff directly into the (Narrow River) and its tributaries, or enlarging 

 the volume, rate, or further degrading the quality of existing discharges is 

 prohibited. Instead, runoff shall be routed through vegetated swales and other 

 structural and nonstructural systems designed to increase time of concentration, 

 decrease velocity, increase infiltration, allow suspended solids to settie, and remove 

 pollutants; such systems will utilize overland flow and re-infiltration as priority 

 techniques for the treatment of runoff; 



2. Retention and detention ponds, and methods of overland flow may be used to 

 retain, detain, and treat the increased and accelerated runoff which the development 

 generates; 



3. Water shall be released from detention ponds at a rate and in a manner 

 approximating the natural flow which would have occurred before development, 

 incorporating the following standards; 



a) Peakflow discharges from 1 year, 2 year, and 100 year storms will not be 

 increased by the development or activity; 



b) Ponds shall not be placed where their use poses concerns of groundwater 

 contamination through the recharging of pollutants from surface runoff; 



c) Detentidn ponds shall have a minimum containment time of 36 hours, a 

 mi nimum sump depth of 3 feet, and whenever possible utilize permeable sides 

 and/or bottoms so as to minimize outflow; 



d) Outflow from structural devices shall have flow proceed to natural vegetated 

 areas or vegetated swales when discharging in proximity to watercourses, 

 wetlands, and the estuary; such areas utilized for sheet flow should have 

 hydrologic and vegetative characteristics adequate to insure that stormwater 

 reaching the watercourse, weUand, or estuary does so in a manner approximating 

 predevelopment or existing conditions. 



4. Natural watercourses shall not be dredged, cleared of vegetation, deepened, 

 widened, straightened, stabilized, or otherwise altered. Water shall be retained or 

 detained before it enters any natural watercourse in order to preserve the natural 

 hydrodynamics of the watercourse and to prevent siltation or other pollution; 



5. Intermittent watercourses such as swales, should be vegetated; 



6. The first 1 inch of runoff from impervious surfaces, such as rooftops and paved 

 surfaces shall be treated and reinfiltrated on the site of the development; 



7. Runoff from parking lots and roads shall be treated to remove oil and sediment; 



CRMC requires that the basic design criteria, methodologies, and construction 

 specifications be those of the U.S. Soil Conservation Service, as described in specifically 

 cited publications. (See Section 320.2 E.) 



153 



