UVM-AWRA CHARRETTE: designing an alternative stormwater treatment technique W h a t I s a C h a r r e t t e? A Charrette is a cross-disciplinary workshop to create designs for complicated problems in a brief time window.

THE PROBLEM: Stormwater  Runoff from impervious surfaces  17 streams and rivers in VT impaired by stormwater  UVM’s 5 new treatment ponds  Centralized treatment – undersized? over-worked?

Centralized Stormwater Treatment Centralized Stormwater Treatment  Reduces rate of runoff for selected design storms  Fails to control volume of runoff  Water quality treatment???  Commonly no recharge to groundwater

Decentralized Approaches  Small-scale approach  Treat close to source  Encourage infiltration, evapotranspiration  Examples: Filter/buffer strips Filter/buffer strips Bioswales Bioswales Infiltration trenches Infiltration trenches Permeable pavement Permeable pavement Roofgardens Roofgardens

THE PROJECT  Design for demonstration project  Votey parking lot, 4820 m 2 drainage area, 85% TIA  Stormwater monitoring data Lead and trace metals Lead and trace metals 2 Fall storm events 2 Fall storm events

Mission & Goals  Minimize the ecological footprint  Increase environmental consciousness  “Greening the campus”  Promote excellence in environmental academics

Decentralized Practices  Bioretention  Dry Wells  Filter Strips  Swales  Rain Barrels  Cisterns  Infiltration Trenches  Tree Box Filter

Bioretention  Landscaped areas  Conditioned soil  Detains and infiltrates  Components: Pretreatment area Pretreatment area Ponding area Ponding area Ground cover Ground cover Planting soil Planting soil Plants Plants Inlet and outlet controls Inlet and outlet controls

Dry Wells & Infiltration Trenches  Excavated trenches  Backfill with stone or gravel  Detains and infiltrates  Components: Pretreatment - filtering Backfill material Filter fabric lining Inflow and outflow controls Observation well

Filter Strips  Grassy vegetation between runoff source and receiving waterbody  Level spreader for sheet flow  Components: Flow distribution Flow distribution Planting material Planting material Berm Berm Outlet Controls Outlet Controls

Swales  Dry or wet swales to slow runoff and promote infiltration  Typical along roadways  Components Pretreatment Pretreatment Check dams Check dams Underdrain Underdrain Planting material Planting material Conditioned soil Conditioned soil

Rain Barrels & Cisterns  Small-scale, low-cost devices  Detention and re-use  Above or below ground  Components: Screen or filter Container Sighting gauge Inlet, outlet, overflow

Tree Box Filters  In-ground containers with street trees  Detains, infiltrates, evapotranspirates  Components: Open-bottom vault Porous soil media Underdrain Salt- and water- tolerant trees

CONSTRAINTS  Physical Characteristics of Site  Cost  Maintenance Requirements    