4/8/2011

1

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

4/8/2011

2

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 

4/8/2011

3

Surrounding Context  Watershed Location

7.2 acres

4 acres

7.2 acresRemediation of Brownfield

Design Development Goals

4/8/2011

4

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

4/8/2011

5

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

4/8/2011

6

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

4/8/2011

7

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

4/8/2011

8

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

4/8/2011

9

ECM Rain garden

Preliminary Design Approach and Process

Add 

4/8/2011

10

Add  Add 

4/8/2011

11

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

4/8/2011

12

4/8/2011

13

4/8/2011

14

•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 

4/8/2011

15

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.

4/8/2011

16

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

4/8/2011

17

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