Use of Regional Detention Basins for Stormwater Quality Management Las Vegas Valley Municipal Separate Storm Sewer System (MS4) Permit Andrew Trelease, PE, CFM Clark County Regional Flood Control District Angela MacKinnon, PE, MBA, PMP, CPSWQ MWH September 4, 2014
MS4 Permit Unique Environment of LVV Detention Basin Program Development Outline Watershed Approach for Achieving Required Water Quality Capture Volume (WQCV) Construction of Stormwater Quality BMP Summary
Managed regionally by the Stormwater Quality Management Committee (SQMC) Stormwater Quality Management In the Las Vegas Valley SQMC comprised of representatives from local governmental agencies: Clark County Regional Flood Control District Clark County City of Las Vegas City of North Las Vegas City of Henderson 3
Las Vegas Valley NPDES Stormwater Program Elements 1. Stormwater Management Plan (SWMP) 2. Stormwater Monitoring 3. Public Outreach and Education 4. Source Control & MS4 Maintenance Program 5. Post-Construction Program for New Development and Significant Redevelopment (NDSR) 6. Illicit Discharge Detection Programs 7. Industrial Facility Program 8. Construction Site Program 9. Watershed 10. Legal Authority 11. Water Quality Standards
NDSR Permit Requirements Detention Basin Program Assess regional flood control facilities to determine if design of future or retrofit of existing facilities to provide additional pollutant removal is feasible and appropriate
OUR UNIQUE ENVIRONMENT Annual rainfall of 4.2, 6-11 runoff events/yr Streets can be swept 10 times between events Drought regulations benefit water quality LV Wash wastewater dominated 90% highly treated effluent 5% dry weather flow Landscape irrigation resurfacing ground water 5% Storm water flow Salty shallow aquifer; Selenium Availability of regional system
Infiltration Suitability
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A watershed-based approach is recommended to efficiently implement water quality treatment at select existing Recommended Detention Basin Program Approach and new regional detention basins within the Las Vegas Valley MS4.
Detention Basin Program Development
Developable Area Estimates Evaluation of potential land area for new development in the Las Vegas Valley by watershed shown in table. Water Quality Capture Volume (WQCV) The WQCV totaling 1,440 acre-feet, could be considered the water quality volume needed to address the MS4 permit requirements for new development.
Three existing regional detention basins are in design for capacity upgrades: 1. Pioneer Detention Basin (MWH) 2. Equestrian Detention Basin (LBG) 3. Angel Park Detention Basin (GCW) Pilot Retrofit Program
Extended Detention Basin (EDB) within Flood Control Detention Basin The figure is an example of how an EDB can be implemented below flood control storage in a detention basin. Options for Water Quality BMPs
Options for Water Quality BMPs
Water Quality Design Feature: Water Quality Outlet
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Water Quality Design Feature: Angel Park Detention Basin
Las Vegas Valley MS4 and NDSR requirements Water quality and design of Detention Basins Pilot Program is in Place Full Scale Rollout Strategy is effective November 2013 Summary Contact Information Andrew Trelease, PE, CFM Angela MacKinnon, PE, MBA PMP, CPSWQ atrelease@regionalflood.org angela.i.mackinnon@mwhglobal.com 702-685-0000 702-821-4344