Post on 26-Jun-2020
LID Case Studies
“Complete restoration efforts for an additional 20 percent of the County's impervious, urban surfaces not currently restored to the maximum extent practicable”
4,300 acres
Montgomery County MS4 Program Management – Massive investments, accelerated schedule • $320 million CIP
• 4 years to implement
• Low Impact Development
• Stormwater infrastructure retrofits
• Stream restoration
• Dashboard – BI/DV to track
progress
2
Seattle’s Integrated Plan Jeff Herr, PE, D.WRE, Brown and Caldwell
Puget Sound, Duwamish Waterway, Lake Washington, Lake Union, Ship Canal, creeks
Stormwater
from MS4
Outfalls
Stormwater from
combined system
and POTW
Combined
Sewer
Overflows
Sewage from
combined system
and POTW
584,000 Kg TSS/Year
174,000 Kg TSS/Year
514,000 Kg TSS/Year
Annual Total Suspended Solids (TSS) to Receiving Waters
Stormwater is major source of pollutant
loading to local water bodies
5,560,000 Kg TSS/Year
• Extended detention basin
• Drain inlet inserts (2 types)
• Infiltration basin and trench
• Oil / Water separator
• Media filters (3 types)
• MCTT
• Vegetated controls
• Wet Extended Detention Basin
• CDS
CalTrans BMP Retrofit Pilot Program
Brown and Caldwell 5
The study evaluated 37 BMPs at 33 sites with 12 types of technology.
Approved Treatment BMPs
Brown and Caldwell 6
1. Biofiltration: Strips/ Swales
2. Infiltration Devices
3. Detention Devices
4. Traction Sand Traps
5. Dry Weather Flow Diversion
6. Media Filters
7. Multi-Chambered Treatment Trains
8. Wet Basins
9. Gross Solids Removal Devices (GSRDs)
Brown and Caldwell 7
Biofiltration Strips and Swales
Infiltration Basins and Trenches
Brown and Caldwell 9
Brown and Caldwell 11
Brown and Caldwell 13
Pilot Studies
Brown and Caldwell 15
BMP Consideration – in ROW
Brown and Caldwell 17
City of Portland Green Streets GI Design and Construction
Brown and Caldwell 18
• Large-scale application of GI/Low Impact Development (LID)
Partnered to achieve their goal to be a top-tier sustainable city:
• Opportunistic
• Aesthetic improvement/ economic revitalization
• Flooding relief
• Standard GI details
• Partnering and outreach
• Data tracking and technical analysis
• Development on-site volume reduction required
City of Atlanta
Metro Atlanta (Roswell, GA)
Developed lessons learned from program to reduce impervious area:
• Permeable paver installations on public streets
• Working with mature trees close to the roadway, utilities, soft soil conditions
• Supporting with Public Outreach
21
Stormwater Credits in Roswell How do the Credits Work?
Brown and Caldwell 22
Property owners and developers may purchase stormwater credits to meet some or all of their stormwater treatment requirements. Aesthetic improvement/revitalization
• A credit is a unit of stormwater treatment that can purchased to partially or fully meet the WQ treatment required for site development
• Credit units are sold by impervious acre treated
• Credit costs are determined by fair market value of similar on-site treatments or by the full project cost borne by City
• Credit costs will vary by location and stormwater facility
• Credits are available on a first come/first serve basis
• The City tracks available credits per facility, what has sold, and what is available
Permeable Paver Transition Critical
Brown and Caldwell 23
Paver aggregate specifications (strength and durability) also critical.
Underground utilities and existing soils and groundwater.
Worked on their Green Streets Program, our focus included:
• Flexibility in Standard Details
• Site Specific Designs to Match Surface Features
City of Portland
Brown and Caldwell 24
Oregon City
Developed their BMP Design Standards, which included:
• O&M Plan
• What to look for
• What to do
• Implementation schedule
Helped city address BMP implementation challenges by developing:
• 3rd Party Property Management Model
• One-stop shopping for large regional sites
• Vegetative and non-vegetative
• Inspection and testing
• Community engagement
• Approx. $1/sq. ft of surface area
City of Cleveland
Develop with the City a BMP design to eliminate SSOs and remove storm drainage from sanitary laterals • Create linear bioswale in sidewalk median
• Capture roof and area drainage in bioswale
• Enhance neighborhoods and improve ROW drainage
City of Columbus, OH
City of Boston
Developed a screening process including non-cost factors to: • Achieve 65% of TP reduction in Charles River
• Cost effective, large–scale urban retrofits
• Maximize TBL
Columbus, OH
Issue
• Eliminate SSOs
• Remove storm drainage from
sanitary laterals
Opportunity
• Create linear bioswale in
sidewalk median
• Capture roof and area
drainage in bioswale
• Enhance neighborhoods and
improve ROW drainage
Boston, MA
Issue
• TMDL - 65% TP reduction in Charles River
• Cost effective, large–scale urban retrofits
• Maximize TBL
Opportunity
• Screen alternatives
• Non-Cost factors such as O&M requirements
Improve Treatment Through BMP Maintenance and Expansion - Lake Claiborne Restoration
Removed 40,000 cy sediment;
restored original volumes.
Increased flood storage/WQ benefit.
Stream restoration.
Constructed 2 off-line treatment
ponds for future sediment capture.
31
DWR Main Facility
• County Property
• Public Access/Education Opportunity
• Training for Developers
• Long Term Monitoring
Gwinnett County Opportunities Demonstration Projects
33
Stream Restoration and GSI Stormwater Retrofit
Pre and Post Comparison
Brown and Caldwell 34
Pre-project
Pre-project
Post-project
Post-project
Brown and Caldwell 35
Design and Construction – Bankston Creek • In-stream structures • J-hook
• Compound cross-vane
• Root wad
• Wetland and stormwater outfall channel
• Bank grading
• Low-flow benches
• Seating area and path
AWRA | November 3, 2010
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