Guadalupe Saldana Subdivision - Texas LID.org Manderson_LID Case Study.pdf · Guadalupe Saldana...
Transcript of Guadalupe Saldana Subdivision - Texas LID.org Manderson_LID Case Study.pdf · Guadalupe Saldana...
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Guadalupe Saldana SubdivisionNet Zero Affordable Subdivision:
LID Design and the City of Austin ECM as a cost saving practice
Reduce Green House Gases : Sequester Carbon : Clean Air : Clean Water : Reduce Soil Erosion : Create Pollinator Habitat : Recycle Waste : Support Human Well‐Being
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Net Zero Affordable Housing PartnershipsGuadalupe Neighborhood Development Corporation (GNDC)
Saldana HomesSaldana Homes
Austin Community Design and Development Center (ACDDC)
Funding sources Kregse Foundation $100,000Enterprise Communities$105,000Austin Energy gy$750,000Austin Brownfield Redevelopment $131,991 City of Austin Bonds$1,650,000
Location within Austin
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Surrounding Context Watershed Location
7.2 acres
4 acres
7.2 acresRemediation of Brownfield
Design Development Goals
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7.2 acresMultifamily housing 60-65 homes
65% home ownership (80% MFI or less)
Design Development Goals
35% rental (60% MFI or less)
Ranging from one to five bedroom units
Community Center 11th Avenue Townhouses North County Housing Foundation Escondido, CA
Design Development Goals4 acre trackSingle family housing30 + homes
100% home 100% home ownership (80% MFI or less)
Three and two bedroom units
Site GoalsHome orientation and footprint
Stormwatermanagement
W i l dWater wise landscape
Drainage easement as an amenity
Low cost
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Water conservation and quality
Landscape as an amenity
Site Goals
Construction savingsOM savings
Improve site performance and ecosystem services
Site Assessment
Downstream Site Conditions Boggy Creek Tributary
Critical Water Quality Zone (CWQZ)Boundaries same as 100 year flood plain between 50-400 feet from the centerline of the waterway. Detention waiver similar to ACC campus. The tributary needed to contain the fully developed 100 year peak discharge to supplement development.Critical Environmental Feature: Wetland species
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HsD Houston black soils and urban land
Existing Soil Type
Bh Bergstrom soils and urban land
Soils: InfiltrationHabitat Survey
Environmental Criteria Manual (ECM)http://www.amlegal.com Min volume is one‐half (0.5”) of runoff plus an
additional one‐tenth (0.1”) for each 10% increase of gross impervious cover over 20% within the drainage area
=1.3”
1.6.2 Water Quality Volume
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1.6.7‐ Innovative Water Quality Controls (ECM)
A. Retention/Irrigation SystemsB. Vegetative Filter StripsC. BiofiltrationD. Rainwater HarvestinggE. Porous Pavement for Pedestrian UseF. Vegetative Filter Strip- Disconnection of
Impervious CoverG. Non-Required VegetationH. Rain Garden
Biofiltration
City of Austin lamar @cesar chavez
ECM BiofiltrationPonding depth 4’ Draw down time 48 hoursFull sedimentation filtration system
WQV stored in sedimentation portion. Sed should be at least 2” higher
Partial sedimentation filtration system ycombines WQV in sed and filtrationsedimentation min 20% of WQV
Primarily filtration with underdrain systemECM provides other regulations on Biofiltration media, plant types, plant amounts, plant locations, and maintenance
ECM Biofiltration
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ECM Rain Garden ECM Rain Garden
Drainage area not to exceed 1 acre Ponding depth of 6”Limited to Commercial and Multi‐family developments pDrawdown time 48 hoursFollows biofiltration regulations for media, plant, and maintenance specs
ECM Rain garden ECM Rain garden
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ECM Rain garden
Preliminary Design Approach and Process
Add
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Add Add
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Preliminary Design: Code Obstacles
•Public right of way: public or private street•Service stubs, electrical transformer, and driveways•Who owns it and responsible•Who owns it and responsible•Single Family vs. townhome•Easements and setbacks from buildings
Preliminary Design: Footprint Versions
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•Phase I infrastructure construction funds were approved by City Council at the end of 2010.
•Infrastructure construction should start in the next few months of everything east of drainage easement
Current Status
easement
•Build 11 homes 9 will be on the multifamily site
•Much interest and activity regarding non profit partners for the community center
Cost Comparisons of other LID projects
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Conservation Research Institute 2005 Changing Cost Perceptions: An Analysis of Conservation Development
The largest cost savings across all built sites were mainly derived from site preparation, storm water management, site paving and sidewalks. At a municipal scale the city of Bellevue WA augmented their natural drainage system to handle urban stormwater . It cost the city 75% less for the system.
Conservation landscaping implies the preservation of natural existing areas and installing native lawns. Can save corporate landowners between $270‐640 per acre.
Cost Comparisons Between Conventional and LID Approaches
Project
Conventional Development Cost LID Cost
Cost Difference
Percent Difference
2nd Avenue SEA Street $868,803.00 $651,548.00 $217,225.00 25%
Auburn Hills $2,360,385.00 $1,598,989.00 $761,396.00 32%
Bellingham City Hall $27,600.00 $5,600.00 $22,000.00 80%
Bellingham Bloedel Donovan Park $52,800.00 $12,800.00 $40,000.00 76%
Gap Creek $4,620,600.00 $3,942,100.00 $678,500.00 15%
Garden Valley $324,400.00 $260,700.00 $63,700.00 20%
Kensington Estates $765,700.00 $1,502,900.00 ‐$737,200.00 ‐96%
Laurel Springs $1,654,021.00 $1,149,552.00 $504,469.00 30%
Mill Creek $12,510.00 $9,099.00 $3,411.00 27%
Prairie Glen $1,004,848.00 $599,536.00 $405,312.00 40%
Somerset $2,456,843.00 $1,671,461.00 $785,382.00 32%
Tellabs Corporate Campus $3,162,160.00 $2,700,650.00 $461,510.00 15%
The average percent savings as determined by the EPA across these 12 projects is 25%
EPA Case Study 2007Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices2nd Ave SEA (Street Edge Alternative) Seattle Public Utilities
The design:Added 100 evergreen trees and 1,100 shrubs
Reduced imperviousness
Included retrofits of bioswales
Conventional curbs and gutters were replaced with bioswales in the rights‐of‐way on both sides of the street, and the street width was reduced from 25 feet to 14 feet.
The final constructed design: •Reduced imperviousness by more than 18
percent
EPA Case Study 2007Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices
•Stormwater managed with LID techniques
resulted in a cost savings of 29 percent.
•Reduction in street width and sidewalks
reduced paving costs by 49 percent.
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TYPICAL STREET CONSTRUCTION COSTSCost per 100 Feet of Street
24 Feet 36 Feet 5-Inch Asphalt Paving/6-Inch Base $6,800 $10,880
6-Inch Curb and Gutter $1,265 $1,265
4-Inch Sidewalk $1,400 $1,400
Total Construction Costs $9,465 $13,545
Land (at $300,000 per acre) $16,800 $25,200
Total Cost $26,265 $38,745
July 2003 U.S. Department of Housing and Urban Development Office of Policy Development and Research The Practice of Low Impact Development
Case StudySeattle Public Utilities Seattle, WashingtonThe renovation of 2nd Avenue in Seattle used alternative street edge treatments. Street width was reduced from 25 feet to 14 feet. Bioswales replaced curb and gutter to reduce stormwater runoff. (ICF, 2005). The project area was based on a 660 foot block and resulted in a 25% cost savings.
Capital Costs Item Conventional LID
Temporary Erosion Sedimentation Control (TESC) Measure
$20,621 $27,273
Removals and Adjustments $44,463 $60,900
Drainage $372,988 $264,212
Paving $287,646 $147,368
Landscaping $78,729 $113,034
Misc. (mobilization, traffic control) $64,356 $38,761
Total Capital Costs $868,802 $651,549
Case StudyPrairie Crossing Grayslake, Illinois 362 home community on 678 acres which included 470 acres of open space, 73 acres commercial space, a community center, schools, a lake and beach, bike trails and two commuter train stations. Street widths were minimized to reduce runoff. Wetland areas were created to manage stormwater (ICF, 2005).
Description Conventional Cost
LID Cost Cost Savings %
Site preparation $277,043 $188,785 32%
Stormwater management $215,158 $114,364 47%
Sanitary Sewer $189 402 $166 827 12%Sanitary Sewer $189,402 $166,827 12%
Water distribution $166,260 $146,868 12%
Utilities $64,790 $39,680 39%
Site paving and sidewalks $463,547 $242,707 48%
Landscaping $50,100 $53,680 -7%
Construction cost subtotal $1,426300 $952,911 33%
Case StudyTellabs Corporate Campus Naperville, Illinois 332,500 square foot of office space. Site preparation included earthwork, grading, tree removal/relocation and constructing retaining walls. Stormwater infiltration techniques were used such as level spreaders, parking lot bioswales and overland bioswales. Additional savings were attained using native landscaping, wetland restoration and parking lot islands functioning as bioswale stormwater features, this resulted in approximately 12% cost savings. (ICF, 2005).
Description Conventional Cost
LID Cost
Site preparation $2,178,500 $1,966,000
Stormwater management $480,910 $418,000
Sanitary Sewer $71,750 $71,750
Water distribution $155,900 $55,900
Landscape development $502,750 $316,650
Construction contingency $847,453 $732,075
Design contingency $338,981 $351,396
Total Capital Costs $4,576,244 $4,011,771
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AUBURN HILLS SUBDIVISION, SOUTHWESTERN WISCONSIN
Auburn Hills in southwestern Wisconsin is a residential subdivision developed with conservation design principles. The clustered design used in the development protected open space and reduced clearing and grading costs. Costs for paving and sidewalks were also decreased because the cluster design reduced street length and width. Stormwater savings were realized primarily through the use of vegetated swales and bioswales.
Conventional Development Cost: $2,360,385Auburn Hills Development Cost: $1,598,989 Total Saved : $761,396$761,396
EPA 2007Reducing Stormwater Costs through Low ImpactDevelopment (LID) Strategies and Practices