Logan Gilbertsen, EI, CFM lgilbertsen@hrgreen.com Phil Stuepfert, Sr. Project Manager pstuepfert@hrgreen.com
Project Overview Design Approach Water Modeling Landscape Approach Built Photos Questions
September 2008 Drainage Study Reconstruct roadways with curb and gutter Traditional storm sewer conveyance Large storm sewers with underground detention were required Design provided collection and conveyance of 100-year, 24-hour duration storm 2008 Cost estimate for drainage improvements - $24.4 Million December 2009 Feasibility Study Focused on green initiatives Combination of rain gardens, permeable pavers, and underground storage was utilized to model 100-year, 24-hour duration storm Projected costs for drainage improvements - $15.0 Million
The neighborhood was experiencing nuisance flooding Green Initiatives were explored and determined to be a viable method Phase 1 Constructed in June 2013 Phase 2 Under construction Phase 3 in the near future
Objective: Address flooding utilizing green initiatives
Identify flooding locations Review overall watershed extents Delineate watersheds to 1-2 acre areas Identify existing flow paths Develop watershed characteristics (RCN, TC, Area) Place BMPs Run model DONE!, right? Not that simple
Key elements? Tree Impacts Neighborhood characteristics Competing priorities Perception of what BMP s are and appearance Residents Staff Elected officials Must do s: Coordinate early and often! Clearly discuss the project objectives and priorities with everyone
Delineate Propose Build the BMP Model Sub-Watersheds Locations
Underground storage were perforated to promote infiltration into the native soils to the greatest extent possible
Some rain gardens were placed over the underground storage units
Measurement Point Event Peak Flow Without BMPs Peak Flow With BMPs % Reduction 50-year 2-hour 69.85 cfs 23.45 cfs 66% 10-year 2-hour 35.25 cfs 15.87 cfs 55% Without Storage With Storage
Measurement Point Event Peak Flow Without BMPs Peak Flow With BMPs % Reduction 50-year 2-hour 44.04 cfs 15.67 cfs 65% 10-year 2-hour 22.98 cfs 9.47 cfs 58% Without Storage With Storage
EXISTING CONDITION EXISTING CONDITION EXISTING CONDITION DESIGN GOAL The Rain Gardens and landscape plants needed to compliment the neighborhood character as much as possible
Many people think native plants look weedy but the deep root systems have many benefits in rain gardens Turf grass Non-native shrubs 2-4 deep roots 1-3 deep roots Native Plants 3-12 +
Mix of Non-Native Plants. and Illinois Native Plants DESIGN INTENT Create defined and organized edges with nonnative plants and the bottom with native plants
KEY ELEMENTS OF THE RAIN GARDENS AT THE WOODLANDS SOIL MIXTURE 30% sand, 30% compost and 40% topsoil NATIVE PLANT MIX (Plugs planted in the bottom of all rain gardens) COMMON NAME BOTANICAL PERCENTAGE Nodding Wild Onion (Allium cernum) 25% Blue Flag Iris (Iris virginica) 25% Common Fox Sedge (Carex stipata) 25% Foxglove (Penstemon digitalis) 25% 1.5 max depth
Under construction Under construction Under drains may be needed with poor sub-surface soils (i.e. clay) but should only be used if necessary
Under construction Oversight through construction is critical and have detailed specs! Under construction
Emergent native plants were massed in the bottom of the deeper rain gardens
Check dams were installed in areas with steeper slope to slow runoff and promote infiltration
Short term and long term maintenance is critical for long term success (utilize qualified professionals )
- Use lower profile plants in the front yards of homes - If possible in your project, use smaller inlet structures
- Minimize potential erosion issues at curb inlet - Clean and defined edges clearly identify the rain garden
The Woodlands project has received awards from the following organizations: APWA - (American Public Works Association) ACEC - (American Council of Engineering Companies) Before