Smarter Stormwater Management Kelly Schmitt Rose Stenglein An example of Low Impact Design

The Problem Conventional Stormwater Management: –Expensive Infrastructure –Pollution Accumulation –Expensive Treatment –Combined Systems –Depleting Groundwater

A Solution - LID/BMP Managing stormwater by allowing and encouraging rainfall to soak into the ground where it falls. Benefits: –Reducing volume of run-off –Removing pollution via natural processes –Recharging groundwater

Additional Benefits Reduce overall costs Maximize vegetative and community areas Increase property values

Design Goals Incorporate pre-development hydrology and terrain. –Flow paths, drainage Minimize impervious surfaces –Narrow roads, reduce road length Conserve natural spaces –Smaller and densely-spaced lots, preserve existing trees Manage runoff locally with a variety of techniques…

Techniques Rainwater barrels and cisterns Dry wells Bioretention areas Vegetated swales Permeable pavers Filter strips Adding compost to soils Ponds Wetlands

The Challenge Come up with a design for a housing development in Eagan

Our Constraints Maintain same geographic boundaries, topography, basic soil composition, climate etc. Create same number of living units of similar size as real design Disregard regulations concerning road width

Design

Maintain Natural Drainage Preserve trees Retain existing drainage paths Reduce grade of steepest slopes Move as much run- off as possible toward sandiest soil

Reduce Impervious Surfaces Smaller footprint of houses Shared driveways

Reduce Impervious Surfaces Narrow Roads

Reduce Impervious Surfaces Narrow Roads

Reduce Impervious Surfaces Green Roofs –Intensive vs extensive –Higher initial & maintenance costs –Potential for leaks

Reduce Impervious Surfaces Green Roof Layers –Vegetation –Growth medium –Drainage –Root Barrier –Insulation –Membrane Protection –Roof Membrane

Mimic Natural Drainage Bioretention “shallow vegetative depression” Runnoff gentely directed towards Stormwater slowly infiltrates the soil Mimic Natural Drainage Bioretention “shallow vegetative depression” Runnoff gentely directed towards Stormwater slowly infiltrates the soil Mimic Natural Drainage Bioretention –Infiltration –Groundwater recharge –Filtration Physical, chemical, biological processes of plants, soil and microbes

Mimic Natural Drainage Bioretention –Infiltration –Groundwater recharge –Filtration Physical, chemical, biological processes of plants, soil and microbes

Mimic Natural Drainage Bioretention in our design

Mimic Natural Drainage Pond –Backup

Mimic Natural Drainage Dry Well Cisterns

Safety Analysis Hazard Description Causal Factors Potential Effects Hazard Risk Index Hazard Control Recommendation DrowningStanding Water Death1-DFence Mosquitoes Breeding Standing Water Transmission of disease 2-CSpray for mosquito control FallingSteep Slopes Injury, broken bones, bruises 3-DCreate gently sloped paths through steep areas

Economic Analysis Conventional Stormwater System vs. LID System

Economic Analysis Present Worth Calculation for 30 year life at 5 and 10% $17,485 (P/A, 5%, 30) = $268,800 $17,485 (P/A, 10%, 30) = $164,800

Summary Reduce pollution, recharge groundwater, enhance neighborhood aesthetics and relationships… All for less money!

Questions?