Experiences and Adoption of Low Impact Development in City of Fort Worth Ranjan S. Muttiah Stormwater Management City of Fort Worth ranjan.muttiah@fortworthtexas.gov
Factoid The most common man made material in the world is concrete
Runoff Treatment Performance Standard RETENTION DETENTION PERCENTILE STORM EVENT TSS + PSD CRITERION OTHER POLLUTANTS
iswm Site Development Controls Table 1.2
iswm in CFW City has no adverse impact and adequate outfall requirements for stormwater. City uses iswm process and design storms: Flood mitigation 100-year/24-hour Conveyance 25-year/24-hour Stream bank protection 1-year/24-hour Water quality treatment with performance standard is not a requirement. WQ treatment is encouraged and incentivized through utility fee credits.
.(%) 0.009 0.05 12.) (.) 1.5( ). ( Ip R ac DA R in ft ac Q v v wv ) ( ). ( ) / / ( ). ( (min),,.) ( 2 2 2 inch Qwv mi DA inch mi cfs q q mi DA T CN q CN T in Q CN u wq c u c wv iswm Water Quality Volume iswm Peak Water Quality Discharge (cfs)
Credit Categories Industrial Permit Compliance, 10% Detention Maintenance, 5% Zero Discharge, 40% Channel Protection Detention, 10% Water Quality Treatment, 25% Inlet Trash Collection, 10% Parking Lot Sweeping, 5% Student Education, 10% Adopt-A-Creek, 10%
WQ Initiatives iswm Performance standard: Treat 85 th percentile 24-hour storm to 80% TSS Award of SW utility fee credits Demonstration sites: Handley neighborhood, Northside service center, Public Safety Training Center, use of native grasses LID & WQ performance standard requirement in public-private development agreements
Jean McClung Middle School Q Wv = 0.71 ac-ft, q wq = 4.6 cfs
Charles Baxter Junior High School Q wv = 1.12 ac-ft Permanent pool/q wv = 29.4 50% permanent pool credit in Q wv calc.
NJ BMP Manual
Northside Service Center (3 phases)
NSC Phase I 66% Q wv treatment in Phase I
Bio-retention details
Fire & Police Training Center Bio-retention in parking lot median
Mounted Police Facility
Native Grasses at Valley Ranch channel
Detention Pond at Luella Merrett Elementary
Stream Restoration at Mary Meadow
Handley Neighborhood Street Bio-swale
LID at Forest Park Medical Center
Prairie Crossing, IL $1.375M savings from: Green stormwater management Narrower streets Fewer sidewalks Fewer curb & gutter
Developers Perspective: Land May not see value of LID in sub-divisions Interested in maximizing profit from land When land is premium (e.g., downtown areas), land surface set aside solely for WQ practice is less attractive May see large tracts with higher end homes as more amenable to LID More incentive in master planned neighborhood
Developers Perspective: Cost Unfamiliarity with LID approach Added A&E costs Low barriers to market entry Uncertainties which may complicate financing Uncertainty in review & permitting ( time is money )
Developers Perspective: Permitting Predictable review process LID that can meet as many other City requirements as practically possible (flood control, forestry, landscaping) Pre-defined standards & specs.
City Perspective: Integration Integrate LID into practices that are required by City ordinances: Stormwater management Zoning & overlay requirements Urban Forestry Landscape requirements Etc.
Examples in Landscaping Parking may project into the landscape area reducing parking lot size from 9 x 18 to 9 x 16. Buffer yard set backs between non-residential and residential uses Minimum 25 points for buffer yards with wood or masonry wall fencing and trees (30-ft grass buffer can be substituted for fencing) For Commercial & Industrial uses: Minimum 10% of landscaped area with native plants. Minimum of 75% front yard landscaping reduced to 50% if native plants are used in SW facility
Mixed Use Urban Villages with open space and densities that encourage transit and pedestrian activity
Join the Movement Blue Zones Project
A&E Practitioner Perspective Higher insurance premiums Lack of local experience & craftsmanship May not have all expertise in-house Concerns about final appearance & acceptance Sub-contracting requires more flexibility (proper timing) Having to make clear cost implication (including maintenance) Demonstrate costs savings & benefits to client Drive competition that will attract sustainable development
Future Plans 1). Consider a policy to implement iswm WQ treatment standard on City projects to the maximum extent practicable. 2). Include WQ as part of City iswm project reviews (> 1 ac. disturbance). 3). Additional WQ review support and technical help by SWM WQ specialist. 4). Document implementation experience. 5). Determine whether City experience of implementing WQ standards for capital projects makes sense for private development.
Summary Importance of predictability in LID (costs not only consideration) Multiple target points of entry for LID practices in development Integration of WQ/LID practices as part of storm water management Importance of community interest, acceptance & momentum