Karst Initiatives/Storm Water Management in Berkeley County Brian Hopkins, Ph.D., P.E. Berkeley County Engineering Department

Issues for stormwater management The Water Balance Water Quantity Control Water Quality Control Karst  Maintaining water balance as impervious covers the Karst features and other recharge receptors  Good quality recharge  Structural issues Nuisances Issues

Measures and Ordinance based on WV DEP/US EPA/Center For Watershed Protection Guidelines Water Quality Volume( WQv) (0.9” in. Precipitation)  Capture and TREAT 90% of average rainfall (0.9” rainfall) Recharge Volume (Rev)  Maintain dry weather hydrology  Based upon the USDA hydrologic soil groups Channel Protection Volume (Cpv)  Protection from erosive events caused by bankful flows due to urbanization Overbank Flood Protection (Qp25)  Protect infrastructure from flooding from increased PEAK flows  zero discharge of 10 yr event in flood hazard areas Extreme Flood Protection (Qf)  Protect infrastructure from flooding during extreme flood events  Restrict development in flood plains

Water Quantity Control Channel Protection Volume – detention of 1 yr event over 24 hours – lower peak discharges and provides a buffering effect Over Bank Protection Volume - Manage the 25 yr storm peak flow rates to pre-existing peak discharge conditions – not volume Extreme Flood Event – Safely pass the 100 yr event Flood prone areas – additional storage required – zero discharge of the 10 yr event Down stream analysis required

Quality Goal is to protect surface and sub surface aquatic systems. Reduction of pollutants. TREATMENT through BMP’s – (Water Quality Volume)  Filtering  Chemical processes (oxidation) and adsorption  Biological processing – microbes, plants, etc.  Plants – filter, uptake, and provide substrate.  Residence time for treatment.

Effective SWM Practices Ponds  Micro-pool ED pond  Wet Pond  Wet ED pond  Pocket pond Wetlands  Shallow Marsh  ED wetland  Pond/marsh system  Pocket Wetland Commercial  Contech Storm Filter  Aquaswirl Filtering  Sand filter Underground Surface Perimeter  Organic Filter/Bioretention Infiltration  Infiltration trench  Infiltration basin Open Channels  Dry/Wet Swales

Recharge Discrete vs. Diffuse Recharge:  Treatment required for pure groundwater Maintain a Water Balance Exfiltration or Recharge Augmentation:  More impervious and more abstraction means less ground water in general thus methodology to make up for what is lost is required. Understanding the dynamics of recharge:  Studies, field investigations, and modeling required to understand total implications

Nuisances Ponded Water SWM and Mosquito abatement  Pretreatment – remove nutrient and organics loadings  Small, Deep pools – “micro pools” promote mixing, reduce stagnation, provide habitat for predators and inhibit invasive emergent vegetation  Predators in properly designed facility Mosquito fish, dragon flies, aquatic beetles, and amphibians.  Fluctuating water surface elevation  Vegetation - Some types of vegetation help with mosquito control, while others exacerbate mosquito problems Spatterdock, Arrowhead, etc. recommended  Chemical - Mosquito dunk and other treatments in maintenance schedules Flexibility - Other filtering options (bioretention, sand filters, channels, etc. do not include standing water (designed for 48 hour drain down time)

Initiatives More geotechnical testing requirements. Requirements of “Geotechnical methods for Karst feasibility testing” specifically added to SWM Ordinance  Karst study, borings, geophysical investigations  Monitoring systems, Maintenance and repair of sinkholes Recommendations for providing Phase I environmental assessments and phase II where required prior to site plan approval Increased field inspections at review time and coordination with WV DEP on Karst areas and features

Initiatives Continued Comprehensive plan for county and zoning to proposed to preserve recharge zones and limit development in more sensitive areas County wide comprehensive topographic data Potential for Master SWM Plan – Storm Water Utility being planned LID options - 2 acre lots, 18’ pavement open street sections

Future/Goals Continued Identification and Studies of Karst Features within the county Computer and GIS based stormwater quantity and/or quality models Water quality testing

References WVDEP Storm Water Management – Ground Water Protection Plan Guidance Document 2000 MD SWM Design Manual Vol. I&II– MD DEP, Center for Watershed Protection, et.al. USDA Natural Resources Conservation Service Maryland Conservation Practice Standard Pond Code 378 (January 2000) “Managing Mosquitoes in Stormwater Treatment Devices” 2004, University of California, Department of agriculture and natural resources. HydroGIS ’96: Application of Geographic Information Systems in Hydrology and Water Resources Management. Brown, W. and T. Schueler, National Pollutant Removal Performance Database for Stormwater BMPs. Center for Watershed Protection. Chesapeake Research Consortium. Meyer, S.P., Salem, T.H., and Labadie, J.W. (1993) Geographic Information Systems in Urban Storm-Water Management, Journal of Water Resources Planning and Management, 119 (2): Chesapeake Bay Program Recommendations for Refinement of a Spatially Representative Non-tidal Water Quality Monitoring Network for the Chesapeake Bay Watershed August 2005, Report of the Task Force on Non-tidal Water Quality Monitoring Network Design Scientific and Technical Advisory Committee, STAC Publication