low impact development in puget sound · 2015-01-26 · innovative approach—low impact...

March 2003

Low Impact Developmentin Puget Sound

CREDITS

Bruce Wulkan, project lead

Steve Tilley, research and writing

Toni Droscher, layout, design and editing

Cover photosClockwise from top: High Point Natural Drainage Systems study, page 29; rain garden

installation, page 5 and pervious driveway, page 17.

Puget Sound Action TeamP.O. Box 40900

Olympia, WA 98504-0900

(360) 407-7300

(800) 54-SOUND

www.wa.gov/puget_sound

If you would like this document in an alternate format, call

(360) 407-7300, (800) 54-SOUND, or the TDD number: (800) 833-6388.

Low Impact Development in Puget Sound

March 2003

Table of contentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Amended soils & bioretentionAmended Soils at Redmond Ridge, King County . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Bog Garden, Shoreline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4Reining in the Rain: Parking Lot Rain Garden, Bellingham City Hall . . . . . . . . . . . . . . . . . . . . . . . .5Natural Drainage Systems, Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Stormwater Treatment on Highway Slope, Thurston County . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Tahoma Vista Ranch, Rainier, Thurston County . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Permeable pavementCountry Lanes, Vancouver, British Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11Pervious Paving Parking Lots Modification Project, Thurston County . . . . . . . . . . . . . . . . . . . .12Grass Parking Lot and Performance Area, Whidbey Island and Bellingham . . . . . . . . . . . . . . .14Pervious Concrete, Multiple Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Pervious Concrete Alley, Bellingham . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Pervious Driveway, Bellingham . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Rooftop rainwater harvestingKing Street Center, Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Residential Rainwater Collection and Use, San Juan Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Rainwater Harvesting Resolution, Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Innovative foundationsLow Impact Foundation Technology, Multiple Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Green roofsJustice Center Green Roof, Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

New and redevelopment projectsBayview Corner, Whidbey Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26The Evergreen State College Zero Impact Feasibility Study, Thurston County . . . . . . . . . . . . . .27High Point Natural Drainage Systems Study, Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Low Impact Development Program, Chilliwack, British Columbia . . . . . . . . . . . . . . . . . . . . . . .31Meadow on the Hylebos Residential Subdivision, Pierce County . . . . . . . . . . . . . . . . . . . . . . . . .32Salishan Public Housing Project Zero Impact Feasibility Study, Tacoma . . . . . . . . . . . . . . . . . . .35Vancouver Island Technology Park, Saanich, British Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Ordinances & regulationsIsland County Stormwater Code Low Impact Development Requirements . . . . . . . . . . . . . . . . .39Issaquah Stormwater Management Policy for Low Impact Development . . . . . . . . . . . . . . . . . .40Lacey Zero Effect Drainage Discharge Ordinance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Olympia Low Impact Development Strategy for Green Cove Basin . . . . . . . . . . . . . . . . . . . . . . .43Pierce County Low Impact Development Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Snohomish County Reduced Discharge Housing Demonstration Program . . . . . . . . . . . . . . . . .47Tumwater Zero Effect Development Ordinance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49Washington State Department of Transportation, Highway Runoff Manual . . . . . . . . . . . . . . . .50

Green building programsGreen Building: Built Green™ and Leadership in Energy and Environmental Design™ . . . . . .51

Glossary of Low Impact Development terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55

Natural Approaches to Stormwater Management:Low Impact Development in Puget Sound

Puget Sound Action Team staff could not have produced this bookwithout the cooperation of the landowners, developers, engineers andlocal government staff whose work and properties are featured inthese examples. The Action Team extends its gratitude to them fortheir assistance and willingness to be innovative and to take risks thatbenefit us all as our region works to transform development practicesin Puget Sound.

For more information on low impact development:http://www.wa.gov/puget_sound/Programs/LID.htm

ACKNOWLEDGEMENTS

1

Puget Sound planners, developers, engineersand others are in the early stages oftransitioning to an innovative approach to land

development and stormwater management. Theinnovative approach—low impact development(LID)—offers potential answers to the question:“How can we significantly reduce the harm fromdevelopment to Puget Sound while accommodatingthe inevitable growth that is occurring throughoutthe region?” The Puget Sound Action Teamproduced this book to showcase early examples ofthis transition.

KEEPING IT NATURAL—AND MORE EFFECTIVELID is a more natural approach to land developmentand stormwater management. Conventional landdevelopment typically involves clearing and gradinga site, resulting in the removal of all vegetation. Thenext development steps traditionally include pavingareas for roads and parking, building structures andlandscaping areas. Engineers then design stormwaterfacilities, such as ponds, to manage stormwater flow,remove pollutants, and infiltrate to recharge aquifers,streams and wetlands.

Research shows that these conventional techniqueshave not proven entirely effective at managingstormwater to prevent damage to water quality andnatural resources. Conventional practices areespecially inadequate at removing bacteria fromstormwater runoff. Pavement and other impervioussurfaces greatly limit or prevent infiltration. Highstormwater flows cause flooding, damage public andprivate property, and destroy habitat for salmon andother fish and wildlife.

In contrast, LID design uses a site’s natural featuresand specially designed best management practices tomanage stormwater. These principles include thefollowing design steps:• Assess and understand the site. Assess the site’s

topography, soils, vegetation and naturaldrainages, and divide the site into protected anddevelopable areas. Protected areas includestreams, wetlands and other critical areas. Applyadequate buffers to protect these areas.

• Protect native vegetation and soils. Set aside aportion of the site’s native vegetation and areaswith soils that have a high infiltration capacity.These natural areas are nature’s own excellentstormwater management systems and, if leftundisturbed, will continue to manage runoff quitewell. To protect native vegetation, clusterbuildings in the area to be developed.

• Minimize and manage stormwater at the source.Minimize areas of impervious surfaces such asroads, rooftops and parking areas by designingshorter, more narrow roads, using variouspermeable pavements, and installing green roofsor rainwater catchment systems. Manageremaining runoff by disconnecting the impervioussurfaces from one another, and directing runoff tobioretention areas (or rain gardens), amendedsoils, native vegetation or other types ofinfiltration areas. This can greatly reduce the needfor pipes and other conveyance infrastructure.

The home, business or development that includesLID design practices causes less harm to areastreams, wetlands and wildlife habitat. Rainwatercan better infiltrate into the ground to rechargedrinking water supplies, streams and wetlands. Thesite is greener and more attractive, with open spacesthat appeal to potential buyers. The developer ormunicipality may save money because the overallinfrastructure costs are often less.

A VARIETY OF APPROACHESLID practices are appropriate for individual homes,residential subdivisions or businesses. LID works fornew developments or as part of a retrofit project tofix existing drainage problems.

The examples highlighted in this publication reflect abroad range of LID applications—including localgovernment ordinances, individual practices, entireresidential subdivisions and new state highwaydesigns. To date, developers and local governmentshave designed most of the projects in moreurbanized areas. However, the projects are alsoapplicable to rural areas, which often have moreextensive stretches of undisturbed forest.

Introduction

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Specific practices highlighted in this publicationinclude a broad range of LID techniques, including:• Various types of permeable pavement.• Rooftop rainwater collection systems.• Bioretention areas.• Soil amendments.• Green roofs.• Open road sections with vegetated swales.• Innovative building foundations.• Homemade bog garden.

Municipalities and developers choose LID techniquesfor a variety of reasons: • To better protect streams, wildlife habitat,

wetlands and other natural resources.• To protect groundwater and drinking water

supplies.• To help communities grow more attractively.• To manage stormwater in a more efficient, cost-

effective manner.

Because LID is in the early stages in Puget Sound,many examples describe projects that use a singlepractice or technique rather than a complete LIDdesign. This publication also features several projectsfrom British Columbia, Canada to provide a broaderview of the level of activity in the PugetSound/Georgia Basin region.

A few examples feature practices that might be moreaccurately defined as “green building,” such as theuse of recycled building materials or increasedenergy efficiency. Several examples also include landuse elements of “smart growth,” such as mixed-usezoning and urban revitalization. LID-designeddevelopments sometimes incorporate elements ofeach of these approaches.

LID is compatible with the sustainable approach ofboth green building and smart growth. As “greeninfrastructure,” LID is best distinguished by itscentral focus on stormwater management. LID doesnot replace local land use planning; rather, it is a setof tools to better manage stormwater from areasappropriately designated for growth.

BRINGING LID TO PRIME TIMEDespite the promise of LID, the vast majority of newdevelopment projects each year still rely ontraditional stormwater management facilities withoutconsidering LID techniques. One reason is that mostlocal government development regulations do notallow for certain LID practices, such as narrowerroads or open road sections without curbs andgutters. Another reason is that many engineers anddevelopers aren’t familiar with LID techniques andcontinue to rely on better-known conventionalpractices.

To address these challenges, the 2000 Puget SoundWater Quality Management Plan calls on every cityand county in Puget Sound to revise existingordinances or pass new ordinances that allow for andencourage LID practices. Several local governmentshave passed LID ordinances (see pages 39-49).

The Puget Sound Action Team has educated morethan 800 planners, developers, engineers and othersat LID conferences and regional workshopsthroughout Puget Sound. The Action Team hasdeveloped an assortment of educational materials onthe subject, such as this publication. A number ofother organizations now also offer training on LID.The Action Team posts these training opportunitiesand links to other resources on its website.

The Action Team hopes you enjoy reading NaturalApproaches to Stormwater Management: Low ImpactDevelopment in Puget Sound. The goal of thispublication is to provide you with ideas andinspiration to learn about and use low impactdevelopment practices in your community.

Bruce WulkanStormwater Program LeadPuget Sound Action [email protected]

Introduction, continued

3

BACKGROUNDThe Quadrant Corporation is developingRedmond Ridge as a mixed-use, fullycontained community within the NoveltyHill Area of the Bear Creek Community inKing County. The 1,046-acre site willinclude a full range of residentialdensities, employment, retail and businessservices, parks and public utilities. Asmitigation for land clearing at the site,Quadrant is amending soils andrevegetating landscaped areas with nativeplants. This will reduce stormwater runoffvolumes and help maintain the waterquality of the receiving native wetlandsand forests.

DESCRIPTIONThe development permits for RedmondRidge describe a total water managementprogram, from site clearing to educatingresidents about water conservation.Conserving native soils and restoring soilsthrough amendment play an importantpart in the water management program.

After removing trees and strippingroadway corridors and developmentareas, the contractor will remove the toplayer of forest duff, stockpiling it for useas amended soil material or to refillborrow areas. Plans call for all landscapesoils to be amended to a depth of 12inches to improve retention of stormwater.King County required Quadrant to useone of two guidelines when amendingsoils:

• Washington State Department ofEcology’s On-Site ResidentialStormwater Management Alternatives,

November 1995 Edition. If Quadrantuses this guideline, the soil-to-compostmix will have a ratio of 1 part compostto 2 parts soils. The topsoil productmust be suitable for placement 12-inches deep in nonstructural fills andlandscaped areas.

• King County Executive Proposed SiteAlterations Code Ordinance (not yetadopted by the King County Council).This ordinance calls for adding nineinches depth of amended topsoilconsisting of nativesoils mixed withorganic matter (mixedat a content rate ofeight to thirteenpercent dry weight)over existing scarifiedtill soils. (Althoughthe ordinance calls fora depth of nine inchesof amended soils, ifQuadrant chooses touse this guideline theymust still amend soils to a depth of 12inches, using the content rate spelledout in the ordinance.)

A Water Conservation Plan will identifylandscaped areas and uses, classifylandscaped areas according to hydrozoneand discuss soil preparation techniques,including soil amendments. Quadrant willeducate all developers about soilamendment during the sale process. Alllot purchase and sale documents willrequire land purchasers to comply withthe soil amendment requirements.

To educate homeowners, Quadrant willprepare educational materials and

AAmmeennddeedd ssooiillss aanndd bbiioorreetteennttiioonn

October 2002.

Aerial Photo ofRedmond Ridgewhere landscapedareas will beamended to adepth of 12 inchesto improveretention ofstormwater.

Amended Soils at Redmond RidgeKing County

programs on landscape management forwater conservation, surface watermanagement, water conservation andgroundwater quality. Quadrant will alsoinstall a landscape plan for a singledetached model home and ademonstration garden.

Quadrant is monitoring the erosioncontrol measures related to siteconstruction and the quality of the

receiving wetland waters. King CountyWater and Land Recourses Division ismonitoring the function of the stormsystem and water quality of the nativewetlands.

CONTACTBob Kelley, King County(206) [email protected]: www.metrokc.gov/ddes/upd/

Redmond Ridge, continued

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Bog GardenCity of ShorelineBACKGROUND

A homeowner in the city ofShoreline installed a boggarden to direct stormwaterflows away from thefoundation of his house. Hisobjective was evapo-transpiration and infiltration ofrooftop drainage rather thandischarging it to the

stormwater system. The bog garden servesas a model for other residentialhomeowners.

DESCRIPTIONThe Bog Garden serves a 1/4-acre

residential propertyand collects roof runofffor infiltration andevapotranspiration withwetland vegetation. Thehomeowner backfilled alined retention pond(12-feet long by 8-feetwide by 3-feet deep)with three-way gardenmix, coconut husk fiberand peat moss. He then

planted more than 30 species of native andnon-native (to the Pacific Northwest)wetland facultative plants on the site. Asthe garden functions, there is no standingwater, but the soils are saturated much ofthe time. Unlike many similar systems, this

one promotes evaporation andtranspiration; the impermeable linerprevents infiltration. Excess water flowsinto a constructed dry streambed.

RESULTSThe Bog Garden is an aestheticallypleasing, affordable garden that providesan effective visual barrier to the street. Theinstallation reduced impermeable lawnsurface while directing water away fromthe house foundation. Very little excessflow discharges from the bog garden, andwhat does flow out quickly infiltrateswithin a few feet of its point of discharge.

The builder estimates that the Bog Gardenwill handle 10,800 gallons per year (basedon 2,000 square feet of roof area dividedby 4, times 36 inches per year precipitation= 10,800 gallons per year).

COSTSThe project cost approximately $600. Thehomeowner could have used a traditionalFrench drain for a similar cost, but it wouldnot have been as aesthetically pleasing.

CONTACTMichael BroiliLiving Systems Design(206) 546-3119 [email protected]: www.lsdg.net

Bog garden before

Bog garden (after) handlesapproximately 10,800gallons of rooftoprunoff each year.

BACKGROUNDWhatcom Creek flows through the city ofBellingham (population 70,000) andeventually enters Bellingham Bay. Urbanstormwater runoff entered the creek,causing high flows and degrading waterquality. A catch basin in a parking lot

behind city hall was one of the sources ofstormwater. The city decided to constructa rain garden (bioretention cell) thatwould treat runoff from the parking lotand also demonstrate the rain gardentechnology to businesses and propertyowners. Project funding came in part fromthe Public Involvement and Education(PIE) program administered by the PugetSound Action Team.

DESCRIPTIONThe city hall parking lot lies betweenWhatcom Creek on the north and city hallon the south. In creating the rain garden,the city gave up three of the 60 parkingspaces in the rectangular lot.

Rain gardens involve layering differenttypes of gravel, soils and mulch—muchlike layers in a cake. The top layerincludes vegetation selected for filtration

of contaminants. The rain garden willclean the parking lot runoff by filteringsome of the pollutants (such as oil dripsfrom cars) and slowing down the rate atwhich it flows into the creek.

COSTSAsphalt . . . . . . . . .$1,056Concrete . . . . . . . . . . .800Gravel . . . . . . . . . . . . . .12Labor . . . . . . . . . . . .1,690Equipment . . . . . . . . 942 Total cost . . . . . . . $4,500

RESULTSCity staff report that thewater appears less turbidthan before the raingarden was built. Therain garden alsoperforms a publiceducation function as itis in a high profilelocation and includeseducational signageabout the water qualityand habitat benefits.

CHALLENGESCity staff were reluctant to give up theircoveted parking spaces behind city hall.

CONTACTRenée LaCroixCity of Bellingham(360) [email protected]

5

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Installing first layer.

Vegetation laid outwaiting to be planted.

Planting raingarden.

Reining in the Rain: Parking Lot Rain GardenBellingham City Hall

BACKGROUNDThe city of Seattle has a population of516,259 and covers an area of 84 squaremiles. As the city’s population grows,stormwater from impervious surfacessuch as streets and rooftops speedstoward area creeks, causing floods andscoured habitat in the winter months, andinadequate creek flows in the dry, summermonths. To address this, Seattle Public

Utilities (SPU) staffare developingprototype “NaturalDrainage System”projects to meetmultiple goalswithin street right-of-ways. Thesegoals includeinfiltrating andslowing stormwaterflow, filteringpollutants by soils

and plants, reducing impervious surface,increasing tree cover and improving thesafety of pedestrian paths. These projectsuse constructed features such as open,vegetated swales and stormwater cascadesto mimic the functions of natural forests.

SEA STREETS PROJECTSeattle’s Street Edge Alternative (SEA)Streets Project manages stormwater andimproves water quality drainage onindividual blocks of low-traffic streets.The project reconfigures the street andright-of-way and uses swales on bothsides of the street. SEA Streets began witha retrofit of an urban block in theBroadview section of Seattle in the PipersCreek watershed. The specific objectivesare to: • Decrease runoff peak flow and volume.• Minimize impervious area.• Improve water quality.• Document effects of alternative design.

• Minimize maintenance through designand stewardship.

• Design watershed and neighborhoodfriendly streets.

• Change the traditional view that curbs,gutters and sidewalks are necessary.

SPU staff selected the Broadviewneighborhood through a process thatconsidered community interest andtechnical feasibility. The site is on 2ndAve. NW, between N. 117th and N. 120thstreets. Key elements of the projectinclude street improvements, drainageimprovements, landscaping andneighborhood amenities. The new streetdesign has a curvilinear form to allowmore flexibility in designing the waterquality improvements. The block has asidewalk on just one side of the street. Inaddition to the water quality benefits, thedesign calms traffic and provides a moreinteresting streetscape. Neighbors wereinvolved in the design process, fromchoosing the number of parking spaces toselecting and planting the trees andshrubs.

The graded swales direct and slow theflow of stormwater and provide detentionduring larger storms. Newly planted treeswill eventually help to restore theevapotranspiration that was presentbefore development. Amended soils in thelandscaped areas have proved to beeffective in retaining stormwater. Thenative wetland plants in the drainageswales also help filter and slow the flowof stormwater.

RESULTSThe SEA Street design resulted in reducedtotal volume of stormwater within its two-block, 2.3-acre area by 97 percent for twoconsecutive years. The project met itsdesign goal of virtually eliminatingstormwater for the level of storms that can

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Seattle SEA StreetsProject. Gradedswales withamended soilsreducedstormwater volumeby 97 percent fortwo consecutiveyears.

Natural Drainage SystemsCity of Seattle

be expected to occur every two years.Residents of this neighborhood enjoywalking along SEA Streets because it is anatural, soft-edged environment, asopposed to the hard edges of traditionallinear streets. More tree cover helpsreduce summer heat while absorbing airpollutants and rainfall.

CHALLENGESThe street and sidewalk design requireddeviations from the city’s buildingstandards. The original design proposedto retain flows and allow infiltration intothe native soils throughout the length ofthe block. This was not possible becausepart of the site had an existing problemwith groundwater intrusion intobasements. To limit the potential forstormwater to exacerbate these problems,some swales included an impermeableclay liner to divert stormwater away fromproblem areas.

COSTSThe budget for the project was $800,000and was funded by drainage fees. Thisincluded a more extensive design andcommunications budget due to the out-of-the-box nature of the project and the needto work closely with residents. The cost offuture projects should compete favorablywith the cost of traditional streetimprovement projects. City staff estimatethe cost of future SEA Street prototypeprojects to be $710,000, while anequivalent conventional drainage andstreet improvement project would costapproximately $840,000. Staff are currentlyworking on an improved SEA Streetprototype design to lower constructioncosts.

CASCADE PROTOTYPESPU staff designed the Cascade Prototypeto be used on steep, residential streetswith high stormwater runoff from

watersheds of five to 50 acres in area. Thedesign includes large cascading swales,sediment trap chambers and intensivevegetative cover. Traditional drainageinfrastructure such as pipes, culverts andcatch basins work in conjunction withmore naturalelements to create abalanced approachto drainage design.

Construction of thefirst Cascade projectbegan in late 2002on N. 110th,between GreenwoodAve. N. and 3rd Ave.NW. This projectcovers four blocksand manages stormwater runoff from a21-acre catchment area. The primaryobjectives of the Cascade prototype are to:• Reduce the velocity of stormwater flow.• Improve water quality.• Decrease runoff peak flow and volume. • Provide additional tree and vegetative

cover.

SPU is moving forward with projects ofboth the SEA Street and Cascade type on15 city blocks in 2003. These new projectswill include a monitoring program forwater quality and stormwater quantityand flow.

CONTACTDenise Andrews, Seattle Public [email protected]

Natural Drainage Systems website: www.seattle.gov/util/naturalsystems

Seattle Public Utilities website:http://www.cityofseattle.net/util/

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The CascadePrototype projectat N. 110th St. aftermost of theconstruction hasbeen completedand beforeplanting.

BACKGROUNDInterstate 5 between Tumwater andMaytown in Thurston County originallyhad four lanes. By 1998, it was serving50,000 vehicles per day and needed to bewidened. Typically, such a project wouldrequire adding stormwater detention andtreatment ponds. However, this section ofI-5 runs through wetlands, and usingadditional wetland area for stormwatertreatment would be problematic.

The Washington State Department ofTransportation (WSDOT) and SCAConsulting Group solved this problem bydeveloping a new stormwatermanagement technique that treatsstormwater on the side slope of thehighway itself. The result is a low impactbest management practice (BMP) thatinfiltrates the majority of the runoff fromfrequent storm events. This is a keyprinciple of low impact development.

DESCRIPTIONThe roadway for I-5 south of Tumwaterruns through two miles of wetlands and isconstructed on fill averaging about 6 feet.The widening project expanded theroadway into the existing median so it didnot require additional right-of-way.However, the project still needed toprovide stormwater treatment, and theadjacent wetlands limited available space.

Conventional alternatives would haveinvolved expensive facilities such as pipevaults or centrifuge manholes. Thesesystems would require a lot of maintenanceand closure of highway lanes for access.Furthermore, the data indicated that thesedevices would only be effective in treatingrunoff during low flow storm events.

To solve the problem, WSDOT and SCAConsulting Group created a new BMPusing the highway side slope. The crewamended the soil on the slope with

8


Stormwater Treatment on Highway SlopeInterstate 5 Tumwater to Maytown,Thurston County

Originally designedfor water qualitytreatment, thissystem should alsoretain small stormevents, according toSCA ConsultingGroup and theWashington StateDepartment ofTransportation.

compost and planted grass to provide pre-treatment of water leaving the road.Lower down near the toe of the slope,they constructed a shallow trench andfilled it with a sand/gravel mix to providefinal filtering. The existing fill slopes wereabout 1:6 (vertical: horizontal), making itdifficult to keep the trench within thevertical limits of the fill, away from theshoulder and out of the wetlands. (Note:because steep saturated fill slopes can beunstable, the technique should not be usedon slopes steeper than 1:3.)

RESULTSWSDOT and SCA originally designed thenew BMP as a water quality treatmentsystem. However, the BMP has infiltratednearly all the runoff for frequent smallstorm events. Because of the success on thissite, WSDOT has adopted this BMP for usein future projects on state roadways thatpass through wetlands. While there is noformal monitoring plan, WSDOT mayperform monitoring in the future.

COSTSBoth the initial and maintenance costsshould be significantly lower than forconventional systems. The system’sdesigners hope that routine mowing willbe the only maintenance required for thesystem.

CONTACTSNeal CampbellWashington State Department ofTransportationPhone: (360) 570-6750 Fax: (360) 570-6751 [email protected]

Thomas W. HolzSCA Consulting Group(360) [email protected]

9


BACKGROUNDThe Rainier Development Corporation isdeveloping a large-lot residentialsubdivision called Tahoma Vista Ranchnear the town of Rainier in ThurstonCounty. Phase I of the project is underconstruction and contains nine 40-acrelots. Phase II will include 36 10-acre lots.Due to the large size of the lots, all runofffrom structures can easily be infiltratedon-site. The remaining challenge is todesign the access road for zero runoff.

DESCRIPTIONThe Tahoma Vista site sits on a flat bluffoverlooking the Deschutes River at 159thAve SE and Vail Road. Design of theaccess road was a challenge because thesite is very flat and mostly covered byshallow soils over hardpan (Class C, tillsoils). Several large wetlands on the siteare not appropriate for discharge ofstormwater. Traditional stormwaterconveyance systems and ponds in thistype of area with very flat gradientswould require deep cuts into the hardpan.

SCA Consulting Group developed a lowimpact design road for the site that willfeature bioretention swales on each side ofthe road. The treatment area of the swaleswill be 1.5 times the width of the roadtributary to it. At the bottom of the swales,soil will be restored to a depth of 2 to 4feet and planted with hydrophilicvegetation to treat stormwater runoff as itpasses through the soil. Water reachingthe till layer will infiltrate slowly throughpockets or fissures in the till.

RESULTSThis best management practice shouldinfiltrate 100 percent of all storm eventsup to the 100-year, 24-hour storm. Plansinclude beginning construction on theproject in late 2002.

CONTACTSDoug BloomRainier General Development(360) 446-2385


10


Tahoma Vista RanchRainier, Thurston County

SCA ConsultingGroup designed thissystem to infiltrateall storm events upto the 100-year,24-hour storm.

BACKGROUNDAlleys or back lanes in Vancouver, B.C.provide access to garages and are used forpublic services such as garbage pickup.Consequently, both passenger vehicles andheavy trucks frequently use these lanes.The city of Vancouver developed anenvironmentally sustainable “CountryLane” design that makes back lanesgreener and more attractive. Thisalternative to paving asphalt lanes to fullwidth is a response to the city’s goal toreduce environmental impacts and tocreate a more livable community. The cityalso hopes to increase public awareness ofstormwater issues.

DESCRIPTIONCountry Lanes feature two narrow stripsof concrete that provide a smooth drivingsurface. A plastic grid is placed betweenand beside these concrete strips andcovered with topsoil and grass. Thisstructural grass can support vehicles andprevents the grass roots from beingcompacted and creating ruts in the soil.The road base is a mixture of aggregate,which provides structural stability, and asand/soil mixture that allows for drainageand provides the soil componentsrequired for grass growth.

RESULTSCountry Lanes provide several benefits:• Controlling stormwater at the source

means less change to stream hydrology.• Surface water infiltration recharges

groundwater.• Topsoil filters pollutants naturally.• Adding green space improves air

quality.• Replacing asphalt with grass reduces

the “heat island effect,” where warmer

temperaturesoccur due topavement.

Vancouver isbuilding three ofthese lanes as ademonstrationproject. With thesuccess of thesedemonstrationprojects, this designwill becomeavailable as astandard localimprovement lane project.

COSTSThe costs areapproximately 50percent higherthan conventionallane paving.However, asbuilders andregulators gainmore experiencewith thisapproach, theywill be able torefine the designand construction process and costs shoulddrop.

CONTACTWally KonowalchukCity of Vancouver, B.C.(604) [email protected]

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Vancouver CountryLane completed.

Preparingstructural grass.

Country LanesVancouver, B. C.

BACKGROUNDNew building construction at TheEvergreen State College requires additionalparking capacity. The philosophy ofEvergreen is to reduce the impact of thecampus on the environment with everymaintenance or redevelopment project,wherever practical. In addition to reducingthe environmental impact, “soft” drainagesystems will provide monitoring andteaching opportunities for students in thecollege’s environmental studies program.Based on a Zero Impact* Feasibility Study(see page 27), the college decided tointensify its use of existing parking areasrather than clearing more forest.

DESCRIPTIONThe Parking Lots Modification Project willprovide additional parking in lots B and Con either side of the main entrance to thecampus. Runoff from the parking lots

currently discharges to the East Fork ofHouston Creek without treatment ordetention. The innovative design adds newparking by removing and reshapingplanting islands and reorganizing lanes.Pervious paving systems will replaceapproximately 34,000 square feet ofexisting landscaping for new parking stalls.The combination of adding new perviouspaving and converting existing paving topervious surfaces will result in a netreduction of runoff to Houston Creek.

The paving bid package includes threealternative paving systems, includingEcoStone® by UniGroup, Gravel Pave 2™,and a system of crushed rock with cellularconfinement. The design for the pavementincludes infiltration to the subgrade andstorage in rock ballast under thepavement. The objective is to infiltrate the100-year, 24-hour storm without surface

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Approximately9,000 square feet ofimpervious parkingarea at TheEvergreen StateCollege will beconverted tobioretention areas(numbered in planat right).

Pervious Paving Parking Lots Modification ProjectThe Evergreen State College, Olympia

*Zero Impact is aproject that adheresto the 65/0 (65percent forest coverpreserved/zeroeffective impervioussurface)developmentstandard and isconstrained bycharacteristics of ahealthy watershedas described in theSalmon in the CityConferenceAbstracts.

runoff. A sand filter providing waterquality treatment is located directly belowthe paving system.

Approximately 9,000 square feet ofparking lot access lanes will be convertedto bioretention facilities. The designprovides for soil restoration to a depth oftwo feet. The objective is to providebioretention areas with sufficient surfaceand subsurface storage volume toinfiltrate runoff from all events up to the100-year, 24-hour storm.

Evergreen may also build a motorcycleparking structure with a vegetated roofthat will be a study focus for students inthe environmental studies program. Themotorcycle port will have approximately 6inches of soil on the roof with plantsselected for their tolerance to extreme wetand dry conditions.

CHALLENGESOne complication of the project was oldfill material found under the existingpavement. Because it is unsuitable forpavers or bioretention facilities,contractors had to remove and dispose ofit. This cost would not have occurred withthe asphalt paving alternative.

COSTSThe cost of the zero discharge parkingretrofits is the same as, or lower than,traditional alternatives using newtreatment and detention systems. Costsfor green roofing will be higher, but theincreased life of the roof will help offsetthese costs. An important factor inchoosing the pervious paving systems isthat this approach negates the need toclear and grade surrounding forest areasfor detention ponds.

CONTACTSMichel GeorgeThe Evergreen State College (360) 866-6000 extension 6115 [email protected]

Website: www.evergreen.edu/facilitiesFollow the link to “Projects and Reports.”

Thomas W. HolzSCA Consulting Group(360) 493-6002 [email protected]

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Pervious pavingmaterials varyaccording to theintensity of use inparking lots. In theabove diagram, acellular confine-ment systemstabilizes a parkingsurface of crushedrock.

BACKGROUNDA farmers’ market and community hall atBayview Corner on Whidbey Islandneeded weekend parking. 2020Engineering designed a reinforced grasspavement system that makes the area looklike open space when not used forparking.

In Bellingham, the owner of the BoundaryBay Brewery wanted to expand the winterparking area and to provide a summerbeer garden and performance area.

DESCRIPTIONThe grass parking lots use an interlockingplastic grid (GeoBlock™ at BayviewCorner and Grassy Pavers™ at BoundaryBay Brewery). The grid was filled with amixture of sand and chicken compost andplanted with grass.

RESULTSThe parking lot designs meet standardsfor traditional traffic loading. The grassparking replicates natural conditions forslowing and infiltrating stormwater runoffand eliminates the need for conventionaldetention/treatment systems.

COSTSThe cost for both lots was $3 to $4 persquare foot, installed.

CONTACT2020 Engineering, Inc. (360) 671-2020Website: www.2020engineering.com

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Grass parking lotdesign meetsstandards fortraditional trafficloads and resemblesopen space whennot used forparking.

Grass Parking Lot and Performance AreaWhidbey Island and City of Bellingham

Bayview corner,Whidbey Island.Top photo: afterconstruction.Lower photo:duringconstruction.

Boundary BayBrewery,Bellingham.Top photo:duringconstruction.Lower photo:after cons-truction.

BACKGROUNDBuilders have used pervious concretenationally for more than 20 years. In the1980s, several projects used perviousconcrete in the Puget Sound basin,including at Husky Stadium and at a parkin Redmond. In recent years, buildershave used pervious concrete in severalnew projects and more are planned.

DESCRIPTIONPervious concrete is a special structuralconcrete with the fine particles removed.This creates 15 to 20 percent voids so theconcrete looks like a giant rice cake. Thepavement will support traffic and allowwater to pass through to a gravel layerunderneath. The strength of perviousconcrete is about 85 percent ofconventional concrete, making it suitablefor sidewalks, driveways, alleys, parkinglots and residential streets. Designers andinstallers need special training to ensurestructural integrity and porosity. Post-placement testing is important.

Pervious concrete is much more porousthan underlying soils. Typical infiltrationrates are 250 to 300 inches per hour;typical installations require soils withpercolation rates of more than 1/2-inch perhour. A gravel bed placed underneath theconcrete stores water before it moves intothe soil or can provide a channel formovement of water to stormwaterchannels. A 4-inch bed of rock oraggregate 3/4 inches or larger with 30percent voids will store 1.2 inches ofwater. In addition to its water quantitybenefits, pervious paving can removesome pollutants through absorption,straining and microbial decomposition.

Following are some of the locations ofrecent pervious concrete installationsaround Puget Sound:• Four blocks of sidewalks on N. 145th

Street, Seattle.• 400 feet of sidewalks at 100th Ave.,

Marysville.• Six parking lots at Fort Lewis.• Sidewalk on North Street in

Olympia.• Plaza at Greenwood Park, Seattle.• Alley in Bellingham.• Parking lot for the Washington

Aggregates & Concrete Associationoffice, Des Moines.

• Nine parking spaces at BayviewCorner, Whidbey Island.

Planning is currently underway for aresidential subdivision to demonstratethe usefulness of permeable concretefor residential streets, driveways andsidewalks.

COSTSThe cost for pervious concrete is typically$6 to 9 per square foot. This is comparableto conventional concrete.

CONTACTSBruce ChattinWashington Aggregates & ConcreteAssociation(206) [email protected]

Greg McKinnon Stoneway ConcreteOffice Phone: (425) 226-1000 ext. 3313Mobile Phone: (206) [email protected]

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Pervious ConcreteMultiple Locations

(Photo courtesy ofGreg McKinnon)

Pervious concreteinfiltrates waterextremely well—typically 250 to300 inches perhour.

BACKGROUNDA residential homebuilder was interestedin sustainable construction and decided totry pervious paving in an alley thatprovides access to homes. This was thefirst application of a pervious concreteroadway in a Whatcom County right-of-way.

DESCRIPTIONThe alley provides access to tworesidential properties while minimizingenvironmental impacts. Porous concreteallows for the infiltration of stormwaterrunoff while providing the samestructural capacity as conventionalconcrete. Engineers determined the depthof the crushed rock base material—usedto support the concrete—based upon the

type of underlying soil conditions andamount of water storage area needed toaccommodate storm events. No finematerials were used.

Since this project was the first of its kind,the city of Bellingham wanted to knowabout durability, load, treatment andmaintenance requirements.

RESULTSStormwater treatment occurs as waterflows through the pervious concrete roadsection and underlying soils. Othercharacteristics, such as maintenanceissues, are comparable to conventionalpavement systems. The engineer used theDepartment of Ecology’s StormwaterManagement Manual for WesternWashington as one of the guides todocument the stormwater infiltrationbenefits of the project.

COSTSMaterials cost approximately $1.50 persquare foot. Installation costs were similarto conventional paving.


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Pervious concretealley, Bellingham.

Pervious Concrete AlleyCity of Bellingham

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Pervious DrivewayCity of BellinghamBACKGROUNDStormwater runoff causes pollution in theLake Whatcom watershed in Bellingham,as it does in many other developed areas.Because Lake Whatcom is the sole sourceof drinking water for the city ofBellingham, this can have seriousconsequences for the city’s drinking watersupply. A homeowner in the watershedwanted to demonstrate alternativesustainable building practices and decidedto replace the existing impervious asphaltdriveway with a pervious one.

DESCRIPTIONThe homeowner installed a perviouspaving system composed of individualinterlocking paving blocks placed on a bedof fine gravel. The configuration of thepavement blocks provides a series of voidsto allow stormwater to infiltrate.

RESULTSThe new driveway has better structuralproperties than the replaced asphaltsurfaced driveway. The pervious paversystem replicates natural conditions forstormwater infiltration, providestreatment, and eliminates the need forconventional detention/treatment systems.The homeowner reports a significantreduction in the volume of stormwaterflowing down the driveway and into thelake.

COSTSThe cost was approximately $5 per squarefoot installed.


The pervious paversystem replicatesnatural stormwaterinfiltration, providestreatment andeliminates the needfor conventionaldetention/treatment systems.

Pervious driveway,Bellingham.

BACKGROUNDKing Street Center, at 201 S. JacksonStreet, began as a typical office buildingproject in downtown Seattle. However,the King County Department of Natural

Resources andParks, a majortenant, asked thatthe building includeenvironmentallyfriendly andsustainableapproaches in itsdesign, constructionand operation.

Completed andoccupied in

September 1999, the 327,000-square-footbuilding houses 1,600 employees of thecounty’s Department of Natural Resourcesand Parks and Department ofTransportation. The center serves as amodel and testing ground for sustainable

practices andmaterials, includinga system thatcollects stormwaterand uses it withinthe building.

DESCRIPTIONIn a first for acommercialbuilding in Seattle,the King StreetCenter collects

rainwater to flush its 105 toiletsthroughout the year. The unique andinnovative system is designed to collect

rainwater from the building’s roof to filleach of three 5,400 gallon tanks. The waterfills and passes through all three tanksand then small cylinders filter the water asit is pumped to toilets in the buildingthrough separate piping. If there is notenough rain to meet the building’sflushing needs, the system automaticallyadds domestic water to the tanks. Inaddition, water diverted from thereclamation system fills much of thebuilding’s landscaping needs.

RESULTSSince rainwater is dumped into the citysewer system, King County is capturingwater that would otherwise be wasted andavoids significant loadings to the sewersystem. The building uses approximately2.2 million gallons of flushing water peryear. The new system saves an estimated1.4 million gallons of water per year,meeting over 60 percent of the building’sestimated annual water needs.

CONTACTDeborah BrockwayKing County Department of NaturalResources and Parks(206) [email protected]

Take a virtual tour on King County’swebsite: dnr.metrokc.gov/dnrp/ksc_tour/

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Rainwater collectionsystem saves anestimated 1.4million gallons ofwater each year.

Collected rainwaterirrigateslandscaping andalso flushes thebuilding’s toilets.

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King Street CenterCity of Seattle

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Residential Rainwater Collection and UseSan Juan IslandBACKGROUNDOne method of reducing stormwaterrunoff and minimizing the strain onaquifers is collection and use of rooftoprainwater. Several major building projectsin Puget Sound incorporate rainwaterharvesting and use systems. (See KingStreet Center, opposite page, and SeattleJustice Center, page 24.) Somehomeowners are also installing rainwatercollection systems in residential homes,including using rainwater as a potablewater supply, primarily in San JuanCounty where water shortages are a majorconcern.

DESCRIPTIONIn the past four years, Northwest WaterSource has installed 60 rainwatercollection and use systems. Forty-eight ofthese provide drinking water and twoserve homes that had access tocommunity water supplies but chose notto connect to them. Northwest WaterSource is also installing pilot systems inSeattle.

Depending on the design of a rainwatercollection system, a variety of issues needto be resolved. These include: design ofthe collection and storage systems,disinfection, pumping, filtration,stormwater infiltration and groundwaterrecharge. Aboveground tanks can bemade of polyethylene or galvanized steelwith a polypropylene liner. Undergroundstorage tanks can be made frompolyethylene, fiberglass, or cement.Installers should choose roofing materialbased on how the rainwater will be used.Rainwater collected only for non-potableuse such as irrigation, requires installersto avoid materials that can leach zinc orcopper, which can damage landscapeplants. Rainwater used for drinkingpurposes requires choosing roofing

material carefully. Vendors of catchmentsystems have information on the bestmaterials to use for specific collectionpurposes.

One house on San Juan Island provides atypical example. The house sits on a smalllot, and seawater has contaminated thesite’s water supply well. Withdesalinization, delivered water, andrainwater collection as the only available

Steel roof withdrain to storagetanks under deck.

Storage tanksinstalled.

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alternatives, the homeowner choserainwater collection. Northwest WaterSource designed the system to provide forthe water needs of two people at 60gallons/day/person, with storage for the90-day dry summer period. (NorthwestWater Source has a spreadsheet availableon request for calculating a home’s waterbudget.) The system will produce excesswater during the wet season.

Storage tanks with a total capacity of10,000 gallons collect rainwater from a1,300 square foot standing-steam,enameled steel roof. The water passesthrough a filtration system before enteringthe storage tanks. Water pumped out ofthe tanks flows through a final sedimentfilter and a carbon block filter beforetreatment by a NSF-approved ultravioletdisinfection system.

San Juan County required the developerto get a water availability permit toacquire a building permit. The designersubmitted a design for the rainwatercollection system to the county healthdepartment, which signed off on thesystem as meeting the guidelines for analternative water system. However, thecounty doesn’t want legal responsibilityfor ensuring that systems are operatedproperly so they don’t inspect theinstallations. The county does require thata restrictive covenant be recorded on theproperty deed along with a system

diagram, water budget, maintenance andoperations sheet, and list of materials usedin construction. This ensures that potentialbuyers are fully informed about thesystem and know how to take care of it.Homeowners are solely responsible ifsystems are not maintained according tothe guidelines and recorded documents.

COSTSThe cost of this system was $10,000 andoperating costs will be around $500 peryear for new filter cartridges andultraviolet bulbs. Electricity costs will bethe same as for a well pump. NorthwestWater Source estimates the cost of anaverage-depth well in San Juan County tobe 75 to 90 percent of the cost of acomparable catchment system, if the wellwater is not very hard or contaminated.

CONTACTTim PopeNorthwest Water SourcePhone: (360) 378-8788Fax: (360) [email protected]

Website: www.rainfallcatchment.com

Residential Rainwater Collection, continued

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Seattle Rainwater ResolutionSeattleDESCRIPTIONIn April 2002, the city of Seattle adoptedResolution 30454 on wastewater reuse andrainwater reclamation. While the majorpurpose for the resolution is to deal withwater supplies, it provides additionalbenefits for reducing stormwater runoff.The resolution calls for addressing anumber of issues relating to reuse ofwastewater and rainwater, such asconsidering the full cost of reclaimedwater, cost recovery, emerging state andnational policy, and the effects on publichealth and the environment. Theresolution also directs Seattle PublicUtilities (SPU) to recommend changes tothe city’s land use and building codes thatwould encourage these programs andtechnologies.

City officials are considering severaldemonstration projects to test how toeducate the public about water reuse andreclamation. City staff will survey near-term water reuse/reclamationopportunities and identify at least onerainwater reclamation demonstrationproject.

Several projects under considerationinclude a pilot program involvinginstalling cisterns in up to 24 householdsto capture rooftop rainfall and slow its

release into the stormwater system duringthe winter. In late spring and earlysummer the cisterns would retain waterfor garden irrigation during the dryseason. As many as half of thesehouseholds may test toilet-flushingsystems using the captured rainwater.SPU is also looking at larger-scalerainwater capture at Sand PointMagnuson Park where the water would beused for a community garden, and theutility is looking at possible rainwaterharvesting for irrigation around multi-family projects.

CONTACTSSteve ModdemeyerSeattle Public Utilities(206) [email protected]

Dick LillySeattle Public Utilities (206) 615-0706 [email protected]

To view the entire text of the resolution,visit the city’s web page at:www.seattle.gov. Under the “City Council” section on theright, select “Legislative Search.” Thenselect “Resolutions” and enter theresolution number, 30454.

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Homeowners inOlympia install aLow ImpactFoundationTechnology (L.I.F.T.)system as analternative to aconventionalfoundation.

Low Impact Foundation TechnologyMultiple Locations

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BACKGROUNDIn 1992, Pin Foundations, Inc. built aboardwalk for the Hood Canal WetlandsPreserve that was supported on piersinstalled without digging or heavyequipment. Since that time, PinFoundations has been developing andtesting a residential construction system

based on the same low impact technology.Pierce County gave broad approval to thesystem in 2001. Builders are using thistechnology to install additions anddetached single-family homes at FoxIsland, Bainbridge Island, Olympia,Tacoma, Key Peninsula and Gig Harbor.

BuildingGreen, Inc., publisher of theGreenSpec© Directory and EnvironmentalBuilding News, recently named LowImpact Foundation Technology (L.I.F.T.) asone of the top ten new green buildingproducts.

DESCRIPTIONL.I.F.T. requires little or no excavation.Sections of foundation wall are poured atgrade and “pinned” into the ground usingheavy-duty steel pins that extend deepenough to support the structure andprevent uplift. Grading is left to smallerequipment that simply “feathers” theexisting surface soils without having tostrip them all away. Lot-by-lot compactionis all but eliminated.

The advantage of the L.I.F.T. system forstormwater management is that the nativesoil structure continues to absorb andprocess rainwater. Runoff from roofs canbe directed back into perimeter soils.Depending on the characteristics of thesite, detention ponds, drywells and pipingcan be reduced in size. Less digging alsoreduces the size and impact of spoils pilesand their contributions to erosion. Leavinghealthy upper soil layers allows for betterplant or sod growth that can also reducethe erosion potential of developed soils.Pin Foundations has created amathematical model for civil engineers touse in calculating the volume of flowsrestrained in surface soils that are notcompacted, and has conducted a casestudy to verify the values.

Homes built on L.I.F.T. foundations haveconventional framing, floor plans andexterior styles. The framer works from atypical level concrete sill with familiaranchor bolting and earthquake strapping.Crawl spaces with standard plastic vaporbarriers are vented in the typical manner,

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and garage slabs are compacted andpoured in the conventional way. Thesystem is applicable for lot slopes up to 10percent grade, and can be used in almostany penetrable soil.

Each building site has different conditions,so the specific configurations vary: • Gig Harbor: A two-story home did not

require grading or site manipulation,and builders poured the foundation tofollow the grade of the site.

• Key Peninsula: Builders used afeathering approach where they bladedoff surface sod. Soils shaped in benchesand differing in height by just 4 incheswere stepped down a 4-percent grade.Here the underlying soils were silts,which tend to be poor for conventionalfootings, especially when they becomewet and soft.

• Fox Island: The goal on this low-bankbeach was to avoid digging aconventional foundation pit that wouldtrap water during flood tides.

• Olympia: Builders put in an addition toa home designed to minimize thedisturbance to existing lawn, gardensand patio.

COSTSL.I.F.T. is comparable in cost toconventional systems. L.I.F.T. systems use20 to 30 percent less concrete, reduce theamount of site materials such as drain

pipe and imported gravels, and reducetrucking, excavator and bulldozer time. Inone of the houses mentioned above, theL.I.F.T. system cost 5 percent more thanthe conventional system. Housing projectswith 10 or more homes will realize themost substantial savings of the L.I.F.T.system.

CONTACTRick GaglianoPin Foundations, Inc.Phone: (253) 858-8809Fax: (253) 858-8607

Website: www.pinfoundations.com

L.I.F.T. foundationinstallation atHabitat forHumanity on theKey Peninsula.

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BACKGROUNDThe city of Seattle needed to replace theold Public Safety Building, which wasseismically deficient and near the end ofits useful life. Its replacement, the JusticeCenter, is one of the first city projects built

to conform to the city’sSustainable Building Policy.To provide stormwatercontrol and other benefits, agreen roof—or living roof—was included in the design.

DESCRIPTIONThe Justice Center greenroof consists of amultilayered waterproofingmembrane integrated with asoil support system. Thefirst layer in the system isthe waterproofingcomponent. Installed over aprepared roof surface, it is a

flexible monolithic membrane composedof refined asphalts and synthetic rubbers.An extra layer of fabric reinforcement isincluded between two membraneapplications. Additional layers over thewaterproofing form the integrated soilsupport system, which comprises the rootbarrier, insulation, water-retention liner,filter fabric and a lightweight plantingsoil.

The egg-carton-shaped water-retentionliner helps to retain moisture betweenrainfalls. Shallow cups hold water andalleviate some of the harsh conditions ofthe rooftop environment that can quickly

dry because of the shallow soil profile.Rainwater not retained by the soil orwater-retention liner flows through holesin the peaks of the liner cups, eventuallymaking its way into subsoil runnels. Thewater then combines with runoff from thenon-landscaped roof area and flows to awater-storage facility at street level.Captured rainwater irrigates landscapingat the base of the building.

The roof system plants will require littleor no maintenance. The plants are droughtresistant and do not require additionalwatering, fertilizing, mowing or pruning.With sustainability a top design criterion,designers rejected the idea of an irrigationsystem for the green roof. Hose bibslocated nearby aid in establishing theplants for the first few years.

Green roof systems are generally dividedinto two categories: extensive andintensive. The Justice Center uses anextensive system, which is characterizedby shallow soils typically 3- to 6-inchesdeep. The weight of an extensive systemwith saturated soils is not much heavierthan that of conventional rooftop ballastapplications, making additional structuralsupport systems unnecessary.

An intensive green roof differs from anextensive green roof primarily in soildepth. Intensive green roof soils aredeeper than 6 inches, allowing for largerplants. The additional soil produces aheavier roof load, which often requiresadditional structural support.

GGrreeeenn rrooooffss

Graphic Courtesy ofAmerican Hydrotech

The green roof ismade up of amultilayeredwaterproofingmembrane that’sintegrated with asoil support system.The egg carton-shaped waterretention liner helpsretain moisture inthe shallow soilbetween rainfalls.

Justice Center Green RoofCity of Seattle

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BENEFITSThe green roof’s soil layer has a sponge-like quality. It will hold a significantquantity of water, as well as releasingwater that it can’t hold more slowly than aconventional roof. The slower releasesmoothes out or attenuates peakstormwater rates. Evaporation from thesoil surface and transpiration by the plantswill further reduce the total volume ofwater that flows from the roof. In the caseof the Justice Center, water that does flowfrom the roof will be stored for irrigationat street level, reducing the total load tothe city stormwater/sewer system.

The green roof also provides benefit inenergy savings. Thermal insulationprovided by the soil layer slows heattransfer to the structure in the summerand reduces heat loss in the winter.

Life-cycle analysis suggests that thewaterproofing for a green roof will lastlonger than that of a conventional roof. Byprotecting the waterproofing fromultraviolet degradation, mechanicalpuncture and temperature extremes, greenroofs are less susceptible to heat damageand cracking.

The green roof also provides potential fly-over habitat for birds, and reduceslocalized heat gain caused by dark, heat-absorbing roof surfaces. The green spacewill be a welcome environment for staff,visitors, and jurors, turning a formerstormwater problem into a buildingamenity.

CONTACTSThor Peterson Sustainable Building Program, SeattlePublic Utilities Phone: (206) 615-0731 Fax: (206) [email protected].

More information on the City of Seattle’sSustainable Building Program:www.cityofseattle.net/sustainablebuilding

Tom von SchraderSvR Design CompanyPhone: (206) 223-0326 Fax: (206) 223-0125 [email protected]

Website: www.svrdesign.com

Photo Courtesy ofSvR DesignCompany

The Justice Center’s12th-floor plazatransforms whatwould have been aconventional flatroof into a livingsystem that willabsorb rain andprovide a rooftopoasis.

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BACKGROUNDGoosefoot Community Fund is dedicatedto preserving rural character and historicfeatures and promoting sustainabledevelopment on Whidbey Island. Todemonstrate non-traditional andsustainable development strategies, thefund developed a rural office and retailhub and learning center at BayviewCorner, on the southern part of the island.

DESCRIPTIONThe fund constructed a public restroomfacility from reclaimed and recycledmaterials to demonstrate cutting-edgesustainable building design. The buildingfeatures solar panels, a 90-gallon rooftopwater collection system, compostingtoilets, waterless urinals and gray waterprocessing. Fund managers estimate that

these practices save 10,000 to 15,000gallons of water each year.

A renovated 1914 Sears Kit Housedemonstrates innovative techniques suchas a Rastra® foundation, which usesinsulated concrete forms made fromrecycled Styrofoam; old-growth redwoodwainscoting milled from a salvaged watertower; and pervious concrete parking fornine parking spaces. For the permeableparking lot, they used a mix similar toregular concrete, but without the sand.This leaves air spaces in the slab, allowingwater to pass through to the soil below.

CHALLENGESPart of the challenge in building thesedemonstration projects has been satisfyinggovernment permit requirements. Quiteoften, systems such as a septic system forthe composting toilet building have beenoverbuilt to meet current building codesand have incorporated devices to monitorany usage. As a result, it is difficult tomake any cost comparisons to traditionalprojects. As trust and relationshipsdevelops with regulators, projects willmove more quickly and costs shoulddecrease.

CONTACTStinger AndersonGoosefoot Community Fund, Langley Phone: (360) 321-4128Fax: (360) [email protected]

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The public restroomat Bayview Cornernear Langley onWhidbey Island usesa number of cutting-edge sustainabledesign features.

Bayview CornerWhidbey Island

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BACKGROUNDThe Evergreen State College on theoutskirts of Olympia has 4,500 students ona 1,000-acre campus. The campus’s stormdrainage system—built before currentstandards—has no treatment or detentionsystems. In 1998, the college adopted astormwater goal in the master plan: “Forplanning purposes the college should tryto limit runoff on campus by minimizinghardened surfaces and maximizingundisturbed forest.”

Evergreen then obtained a grant from U.S.EPA Region 10 to study the feasibility ofdisconnecting the college’s storm drainsfrom the streams around the campus. Thecampus seemed a good candidate for thisstudy because the campus has 70 percentforest cover area, which is greater than therecommended minimum for “zeroimpact”* projects.

Prior to the study, there was no visibledamage to streams in the area, in spite ofthe lack of stormwater treatment ordetention. However, part of the campusdischarges to Green Cove Creek, whichthe city of Olympia and Thurston Countyhave singled out for special protection.Part of the campus also discharges toHouston Creek, a productive salmonstream. College officials also wanted to dothe study to foster sustainability, toprovide an example for the community,and to provide a teaching opportunity.

DESCRIPTIONThe college hired consultants to inventorystream conditions and review existingstudies on fisheries and water quality.Consultants also reviewed the college’scomprehensive plan and capitalimprovement program and engineeringstudies of campus soils, groundwater,

geology and infrastructure. Theyproduced two kinds of analyses: • How to introduce zero impact

development design to new structures.• How to retrofit existing development

during the course of majorredevelopment projects.

The study identified five areas for the useof low impact techniques: roofs, parking,roads, walkways and landscaping.

Recommendations include: • Roofs. Use of infiltration, collection and

green roof systems. • Parking. Alternatives include adding

stormwater storage under parking areasand in landscape strips, and reducingimpervious surfaces through use ofpervious paving.

The Evergreen State College Zero Impact Feasibility StudyCity of Olympia

*Zero Impact meansa project that adheresto the 65/0 (65percent forest coverpreserved/zeroeffective impervioussurface) developmentstandard and isconstrained bycharacteristics of ahealthy watershed asdescribed in Salmon in the CityConference Abstracts.

Road designconcept thatrequires noexcavation.

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• Roads. Use of pervious pavement,directing drainage to adjacent forests,amending the soils of side slopes, anddisconnecting drainage from streams.Recommendations included new roaddesign concepts, some of which did notrequire excavation of existing soils fortheir construction.

• Walkways. Many campus walkwaysserve more as architectural statementsthan transportation. Alternativesinclude removal, replacement withpervious walks, placing perviousbuffers around catch basins, expandingplanters, and adding grass-roofedcovered walkways.

• Landscaping. While there iscomparatively little formal landscapingon campus, the study recommendedthat some landscaped areas could beconverted back to natural forest, withamendment of soils to repair compactedareas.

RESULTSThe college has begun to implement thestudy by including a garden roof on itsnew Seminar 2 building (construction

began in 2002). Soon, the college willrebuild portions of its parking lot usingpervious pavement systems and maybuild a motorcycle parking structure witha vegetated roof. This would be a studyfocus for students in the environmentalstudies program.

COSTSThe study estimated that the costs of zeroimpact roads and stormwater systemswould be as much as 60 percent lowerthan traditional high impact systems.Conversion of car parking to perviouspavers would be the same as or lowerthan traditional alternatives, whichrequire expensive new treatment anddetention systems. Green roofing wouldbe more expensive, but the life-cycle costmight be lower.

An important factor in choosing thepervious paving systems is that thisapproach negates the need to clear andgrade surrounding forest areas fordetention ponds. Implementing the study’srecommendations has an additional benefitto the public because the drainage system

Evergreen State Feasibility Study, continued

New road designconcept for arterialroads featuresnarrow roads andpermeableshoulders.

THICKENED EDGEASPHALT CRUSHED

ROCK

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BACKGROUNDStarting in 2003, the Seattle HousingAuthority (SHA) will begin constructionof a 120-acre mixed-income housingdevelopment in West Seattle. Thedevelopment will include a new streetgrid complete with new utilities,sidewalks, and trees. Plans call for anatural drainage system to be integratedinto the new street layout, creating anetwork of connected, vegetated andgrass-lined swales. The site comprisesone-tenth of the Longfellow Creekwatershed, and this project is a once-in-a-lifetime opportunity to provideneighborhood enhancements and improvethe health of the creek.

DESCRIPTIONLongfellow Creek watershed startedfeeling the effects of development in theearly 1900s. Physical barriers, piping ofsections of the creek and pollutionreduced the return of chum, coho andchinook salmon. In recent years, theremoval of barriers and development ofthe Legacy Trail along the creek corridorincreased fish and wildlife populationsand promoted community stewardship ofthe creek.

Now SHA and Seattle Public Utilities(SPU) are going to the source of theproblem by completely changing howthey manage stormwater in the HighPoint neighborhood of West Seattle.Currently, a series of underground pipescollect stormwater and discharge itdirectly to Longfellow Creek, polluting itswaters. SHA and SPU will redevelop theexisting drainage system in thisneighborhood with a new naturalisticapproach. The approach to redevelopingthe High Point neighborhood will provideguidelines for future construction of

A naturalisticapproach to planningfeatures a network of grass-lined andvegetated swales.

High Point Natural Drainage Systems StudyCity of Seattle

could eventually be disconnected from thelocal stream system.

CONTACTSMichel GeorgeThe Evergreen State College(360) 866-6000 extension 6115 [email protected]

Website: www.evergreen.edu/facilitiesFollow the link to “Projects and Reports.”

Thomas W. HolzSCA Consulting Group(360) 493-6002 [email protected]

30


publicly and privately funded homes.High Point will feature 1,600 primarilylow-rise rentals and owner-occupiedhomes on 120 acres.

Throughout 2002, SvR Design Companyworked with the city, SHA, SPU, theSeattle Department of Transportation, andthe community to develop a menu ofnatural drainage system options tailoredto the needs of each neighborhood block.These options balance “people space”(playable space and garden walks) withstormwater management (infiltration,filtering and flow control). A network ofgrass-lined and vegetated swales will filterand moderate water flows entering thecreek. This will reduce discharge ofpollutants, decrease erosion, stabilize thecreek water temperature, and ultimatelyimprove the habitat for salmon and otherwildlife in Longfellow Creek.

EXPECTED RESULTSThis new drainage approach will functionas a natural system by increasinginfiltration, improving water quality, anddecreasing the volume and rate of runofffrom the development. Rain falling onpavement will flow into the swales wherevegetation will slow the water. Soils,amended with organic material to mimic a

natural forest duff layer, will increase therate of infiltration and water-holdingcapacity. Pollutants, pesticides and animalwaste will be absorbed into vegetation andonto soil particles. Gravel under themodified soils will improve infiltrationand increase water retention capacity.During smaller storms, rainwater willslowly infiltrate into the soils andeventually into the groundwater. Duringlarger storms, water flow will be slowedbefore entering the creeks, thus reducingflooding and erosion of stream banks.SHA and SPU will also provide designguidance for amending the soils onhomesites to reduce runoff from roofs andlots into the swale system.

CONTACTSMiranda MaupinSeattle Public [email protected](206) 386-9133

Peg StaeheliSvR Design Company [email protected]

Tom PhillipsSeattle Housing [email protected]

High Point Study, continued

Bioretention swales(circled) will treat,reduce and slowstormwater runofffrom impervioussurfaces andfunction as anatural system.

31


BACKGROUNDThe city of Chilliwack, east of Vancouver,British Columbia, has a population of70,000 and covers 281 square kilometers(108.5 square miles) and nine watershedsthat drain primarily to the Fraser River.Most of Chilliwack sits on the valley floor,but there is pressure to develop on thesteep hillsides. The city decided topromote low impact development toaddress growing problems with flooding,and to protect habitat and water quality,enhance salmon streams, and rechargeground water.

DESCRIPTIONCity officials adopted an integratedmaster drainage plan that incorporates adevelopment philosophy and designstandards based on LID technologies. Oneobjective of the plan is to “managedevelopment to maintain stormwatercharacteristics that mimic the peak flows,duration of flows and water quality in thepre-development watershed.”

City staff are working with developers toincorporate several low impact designprinciples, such as smaller lot sizes,narrower roads, and elimination of curbs,gutters, storm drains and sidewalks.Many developers are reluctant to use theprinciples for fear of not being able tomarket the lots. However, severaldevelopers have agreed to incorporateLID, and this experience will beinstructive.

The developer built the Peach RoadSubdivision with small lots, a narrowroad and no storm drain for the street.Roof runoff goes into the yards and thendrains to a surface swale for infiltration.The road has no storm drain; water runsdown the road to an infiltration gallery. Amajor rainfall in January 2002

overwhelmed thecapacity of theinfiltrationgallery, leading tosome floodingand damage to afew houses.Although thedeveloperremainscommitted to lowimpactdevelopment, heis building a detention pond on anadjacent subdivision to handle the largeststorm events.

Suncor Developments is anotherresidential development following LIDprinciples. Twenty-two lots, built as ofDecember 2002, feature narrow roads, nosidewalks, and no curb or gutter. Roadrunoff flows to an infiltration gallery.

The Russel Heights Townhouse Project islocated on a challenging site with steepslopes. Runoff from the lots will bedirected to a large green area forinfiltration. Road runoff will be directedto an infiltration gallery that will providedetention for medium storms. Largestorms will bypass the infiltration gallery.

The city plans to install monitoringstations at each of these residentialhousing projects to monitor both runoffvolume and water quality chemistry.Chemical parameters will includetemperature, turbidity, dissolved oxygen,and pH.

Monitoring for two other LID projects willalso begin in the coming year. StreamInternational has an existing 800-stallparking lot that discharges into anadjacent stream. After negotiations withthe city, Stream agreed to help build an

The Peach Roadsubdivision inChilliwack, B.C.features small lots, anarrow road and nostorm drains in thestreet.

Low Impact Development ProgramCity of Chilliwack, British Columbia

32


BACKGROUNDPierce County is working with adeveloper and AHBL Engineering to bringlow impact development technologies tothe Meadow on the Hylebos—a sensitiveresidential development site in northPierce County.

The site is located on an important streamsystem—the Hylebos Waterway. Theintent of the project is to use a variety ofLID technologies to demonstrate thepotential benefits to managing runoffvolume and protecting water quality. Dueto the proximity to the Hylebos Waterway,the technologies also offer the potential toenhance wildlife values by preserving andreintroducing native vegetation.

Another project objective is to deliver ahousing product that is attractive andaffordable. The Meadow on the Hylebosestablishes a design process and forumthrough which the developer and PierceCounty can cooperate, understand

challenges, and develop a design thatmeets the objectives of environmentalprotection and affordable housing.

DESCRIPTIONThe Meadow on the Hylebos is an 8.9-acresite located between Milton and Fife inunincorporated Pierce County. The site islocated at the intersection of SR 99 and70th Street, at the geographic center of anurban growth area. It is well served byfreeways and arterials. The site is highlyvisible, located on the hillside above thePuyallup Valley floor. With its relativelysteep slopes, it offers panoramic views ofthe valley and Mt. Rainier. Soils on thesite are primarily glacial till, offering achallenge for low impact design.

Construction on the project is due tobegin in Spring 2004. The developer plansto build 35 residential units on theproperty. The drainage plan for thesubdivision calls for the use of a variety ofLID techniques, including narrower, open

Meadow on the Hylebos Residential SubdivisionPierce County

infiltration gallery on adjacent cityproperty that will serve Stream as well assome other properties. At Village at SardisPark a major green space will serve as aninfiltration system and detention facilityfor road runoff.

COSTSDevelopment costs for the LID residentialprojects are approximately $800(Canadian) higher per lot than for

conventional systems. The higher costs aredue to requirements for redundantstormwater facilities in case the LIDfacilities don’t perform as expected.

CONTACTDipak BasuCity of Chilliwack, British Columbia(604) [email protected]

Low Impact Development Program, continued

33


road sections with swales; bioretentionareas; pervious pavement; and low impactfoundation technologies to reducebuilding excavation. The homes willincorporate a number of green buildingtechniques as well.

Once completed, the Meadow on theHylebos will be an importantdemonstration project for the applicationof LID technologies in an integrated sitedesign. The project will be the first inPierce County to fully illustrate the rangeof LID technologies in a typical residentialsubdivision.

A consortium of public and private sectororganizations is monitoring the site for pre-and post-development runoff volume toevaluate the effectiveness of the LIDpractices. Depending on available funding,the group will monitor water quality aswell. Washington State UniversityCooperative Extension is leading the effort,and is partnering with Pierce County,AHBL, the University ofWashington, Pacific Rim Soiland Water, and the Puget SoundAction Team.

COSTSAHBL prepared a costevaluation for the site for boththe conventional design andLID preliminary plat design.The evaluation indicates apotential savings inconstruction costs ofapproximately 9 percent.

Kensington EstatesFor another project in thecounty, AHBL analyzed arecently completed subdivision,Kensington Estates, todocument the potential benefitsthat might have occurred if the

subdivision had incorporated LIDtechnologies rather than conventionaltechniques. AHBL applied the newdrainage model in the Department ofEcology’s Stormwater Management Manualfor Western Washington, then outlined theLID process, chose appropriate controltechniques, and conducted comparativecost analyses between LID andconventional stormwater managementtechniques. The resulting redesign of theproject protected sensitive areas, providedadditional green space, accommodatedaccess for emergency vehicles, andmaintained the same number ofdevelopment lots. The results of theexercise showed an approximately 20percent reduction in development costs.

EXPECTED RESULTSThe Meadow on the Hylebos project willdemonstrate the benefits of using LIDtechnologies in a residential subdivision.It will demonstrate individual techniquesand show that the application of LID

The Meadow on theHylebos designretains forests,clusters homes, usesbioretention swalesand includespervious parking.

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Meadow on the Hylebos, continued

technologies in a residential setting resultsin attractive housing and greenneighborhoods.

The Meadow on the Hylebos will providethe development community and PierceCounty with a forum in which to explorethe design and permitting process for anLID project. The project is a jointapplication between Pierce County andthe developer. The project will improveprotection of an important fish-bearingstream, deliver a housing product that isaffordable, and establish a design processand forum through which the developerand jurisdiction can cooperate, understandchallenges, and develop a design thatmeets the objectives of environmentalprotection and affordable housing.

In addition to potential construction costsavings, AHBL has found that applicationof LID technologies can help maintainproject densities. Ecology’s new drainagemodel can result in much larger detentionponds for conventional developments,reducing the number of buildable lots ifdevelopers don’t incorporate LIDpractices. AHBL’s design work indicatesthat projects could lose approximately 10percent of their proposed net density ifLID practices are not incorporated intonew developments. The application of LIDtechnologies thus gives communities away to not only preserve the environment,

but also maintain densities as mandated inthe Growth Management Act.

CHALLENGESThe first major challenge was to identify apotential piece of property and a willingdeveloper to accomplish thedemonstration project. The site’s locationon the Hylebos, within the geographiccenter of the urban growth area, and theinterest of the developer to protect theenvironmental quality of the site all lentthemselves to an LID project at thislocation.

The chief obstacle faced during projectdesign was reconciling the manyjurisdictional requirements while stillmaintaining the objectives ofdemonstrating LID technologies. Forexample, the Tacoma Fire Departmentinsisted on a wider street profile tomaneuver their emergency vehicles. AHBLmodified the site plan to accommodatethese concerns and still achieved theprimary objectives of low impact design.

CONTACTLen ZicklerAHBL, Inc.(253) 383-2422 [email protected]: www.ahbl.com

35


BACKGROUNDThe Tacoma Housing Authority plans toredevelop the 150-acre Salishan PublicHousing Project. This will involve razingexisting World War II vintage housing andreplacing it with 1,200 new units forapproximately 3,000 people.

In addition to the housing benefits,Tacoma Housing Authority’s goal is toreduce or eliminate Salishan’s impact ontributaries to the Puyallup River.Historically, Swan Creek supportedchinook salmon and other fish species. Asa first step, Tacoma Housing Authoritycommissioned a feasibility study todetermine if the project could beredeveloped using zero impactdevelopment* (ZID) standards and remainwithin the guidelines and cost constraintsfrom the U.S. Housing and UrbanDevelopment funding requirements.

DESCRIPTIONA team of consultants led by Torti Gallasand Partners performed the feasibilitystudy. Washington Department of Ecologyprovided grant funding for the study. SCAConsulting Group wrote the grantproposal, and served as project

hydrologists, stormwater engineers, androad designers for the Torti Gallas studyteam. Consultants compiled ZIDstandards and design guidelines andcompared these standards with existingcity of Tacoma standards. This helpedidentify variances to existing developmentcodes that would be needed to constructthe project. One of the goals of the projectwas to retain 65 percent of the site inforest cover. The team considered everysquare foot of the project for retention,restoration and reforestation to meet theforest cover target.

The Salishan property straddles SwanCreek and T-Street Gulch canyons onTacoma’s Portland Avenue between 38thand 56th streets. These canyons provide asignificant amount of forested area thatcould be preserved and counted towardthe goal of 65 percent forest cover for theproject.

Approximately 3.5 miles of new andexisting streets will provide access to theproject. Therefore, a major focus of thestudy was street design using pervioussystems and roadside bioretentionfacilities. The consultants counted thebioretention facilities toward the forest

The Salishan designcalls for wideplanter strips and abioretention area ina center greenspace.

Salishan Public Housing Project Zero Impact Development Feasibility StudyCity of Tacoma

* Zero ImpactDevelopmentmeans a projectthat adheres to the65/0 developmentstandard and isconstrained bycharacteristics of ahealthy watershedas described in theSalmon in the CityConferenceAbstracts.“65/0”means 65% forestcover preserved /zero effectiveimpervious surface.

cover goal. They also investigated thebenefits and costs of pervious pavingsystems for parking lots, rooftoprainwater collection systems, green roofs,wastewater recycling and reforestation ofopen spaces.

RESULTSThe study found that the cost of newstreet construction was lower than orcomparable to conventional practices.However, soil restoration for the portionsof the project that would be restored to

forest added considerable cost to theproject. This may put low impactredevelopment for this site at a cost-disadvantage compared to traditionalhigh impact development practices. Thedraft study, including cost comparisons, isnow available.

CONTACTSCleo Everett Tacoma Housing Authority Hope VI ProgramPhone: (253) 207-4467Fax: (253) [email protected]

Paul MortensenTorti Gallas and PartnersPhone: (301) 588-4800Fax: (301) 650-2255


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Salishan Public Housing Project, continued

The feasibility studyrecommendedCalifornia strips, suchas those picturedabove, for use inalleys at Salishan.

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BACKGROUNDThe British Columbia BuildingsCorporation is redeveloping the formerGlendale Lodge Hospital in theMunicipality of Saanich. The goal is toconvert the 165,000 square-foot hospitalinto the Vancouver Island TechnologyPark to provide space for high-technologyresearch and development businesses.

Saanich has a bylaw requiring all newdevelopments to provide a stormwatermanagement facility to handle the changein post-development stormwater runoff.The Vancouver Island Technology Parkproposal presented an opportunity tosimultaneously restore stream andwetland function to many previouslydegraded freshwater systems. The designincorporated LID stormwatermanagement practices to prevent waterquality degradation during and afterdevelopment and to protect and restoreriparian function. Aquatic and terrestrialwildlife habitat have both improved as aside benefit of these activities.

The Vancouver Island Technology Parkproject received the LEED Goldcertification (version 2.0) from the U.S.Green Building Council. This was the firstproject outside the U.S. and the firstretrofit anywhere to get Gold certification.

DESCRIPTIONThe project consultant, Aqua-Tex, designsand builds ecologically functionalstormwater treatment facilities. Aqua-Texlooks for opportunities to work with thedevelopment community to find cost-effective stormwater solutions that notonly deal with on-site stormwater, butalso address stormwater problems fromneighboring sites (stormwater run-on).Aqua-Tex also seeks to regenerate orrebuild riparian areas.

Project designs most closely resembleconstructed wetlands, and are based onthe Properly Functioning Conditioncriteria for streams and wetlandsdeveloped by the U.S. Department ofAgriculture’s Forest Service/Bureau ofLand Management. The firm has adaptedthese criteria for urban use. Using thesecriteria in the design assures that the finalproject will function effectively over thelong term without expensive maintenance.The criteria also serve as a checklist foraddressing all critical aspects and avoidfocusing on a single value such as fishhabitat.

Aqua-Tex designed the stormwatermanagement plan to deal with immediateredevelopment needs and a significantamount of run-on from adjacentproperties. They created stormwaterponds and channels on two sides of theproperty to provide maximum detentionand infiltration, and to capture runofffrom adjacent parking areas at CamosunCollege and Layritz Park. Grassy swalesand open channels, rather than piping,lengthened flow paths. Other practices

A newlyconstructedstormwater pond.Designs areintended tomanage stormwaterand protect andrestore riparianhabitat function.

Vancouver Island Technology ParkSaanich Municipality

included splitting stormwater flows sothey were not concentrated in onelocation, reconfiguring and vegetatingexisting drainage ditches to slow flowsand trap sediment, and amending soilsaround stormwater ponds to betterestablish new plantings, improveinfiltration, and reduce surface runoff. Inaddition, the design included shallowstormwater ponds within the forestedarea to avoid tree root damage and soilcompaction.

Other design features also minimizedstormwater runoff and improvedecosystem function. GrassPave™ andGravelPave™ provided parking surfacefor approximately 170 cars. The parkinglot will handle the stormwater volumefrom a 10-year storm event. Usingrainwater on site wherever possibleminimized runoff; for example, dual

plumbing allows collected rooftoprainwater to be used to flush thebuilding’s toilets. Though not currently inuse, rainwater may in the future be usedto flush toilets. Collaboration with theHorticulture Centre of the Pacific andSaanich Parks helped determine thelocation of walking trails outside thefloodplain. The use of more naturalmaterials in the stormwater facilities, suchas large logs rather than concrete, helpedrestore Viaduct Creek.

CHALLENGESCoordinating this “green” projectrequired extra effort for all parties.Communicating the requirements of thestormwater bioswales, wetlands andponds to the design team, particularly theengineers, was problematic as they wereunfamiliar with this approach.

COSTSIncorporating LID features into VancouverIsland Technology Park providedconsiderable cost savings. The LIDapproach cost $150,000 while aconventional stormwater treatmentsystem would have cost $680,000. Thesavings are due to the pipes andexcavation that are not needed in the LIDapproach.

CONTACTCori L. Barraclough Aqua-Tex Scientific Consulting Ltd. Phone: (250) 427-0260Fax: (250) 427-0280

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Vancouver Island Technology Park, continued

Site design of theVancouver IslandTechnology Parkincludes extensiveopen space.

39

BACKGROUNDIn December 1998, Island County adopteda stormwater ordinance that providesdevelopers with the option of using lowimpact development practices. The designstandards are based on Low ImpactDevelopment Design Strategies—AnIntegrated Design Approach, prepared byPrince Georges County, Maryland, January2000.

DESCRIPTIONThe Island County Stormwater andSurface Water Ordinance provides specialperformance requirements that developersmust meet for their developmentproposals to qualify as LID. The code

states:

A.Runoff Volume Control. The pre-

development volume is maintained by a

combination of minimizing the site

disturbance from the pre-development to

the post development condition and then

providing distributed retention BMPs.

Retention BMPs are structures that retain

the runoff for the design storm event. A

“customized” or detailed runoff curve

number (CN) evaluation is required to

determine the required runoff volume.

The storage required to maintain the pre-

development volume may also be

sufficient to maintain the pre-

development peak rate.

B.Peak Runoff Rate Control. Low-impact

development is designed to maintain the

pre-development peak runoff discharge

rate for the selected design storm events.

This is done by maintaining the pre-

development time of concentration and

then using retention and/or detention

BMPs (e.g., rain gardens, open drainage

systems, etc.) that are distributed

throughout the site. The goal is to use

retention practices to control runoff

volume and, if these retention practices

are not sufficient to control the peak

runoff rate, to use additional detention

practices to control the peak runoff rate.

C.Flow Frequency Duration Control.Since low-impact development is designed

to emulate the pre-development

hydrologic regime through both volume

and peak runoff rate controls, the flow

frequency and duration for the post

development conditions will be almost

identical to those for the pre-development

conditions. The impacts on the sediment

and erosion and stream habitat potential

at downstream reaches can then be

minimized.

D.Water Quality Control. Low-impact

development is designed to provide water

quality treatment control for the duration

storm runoff from impervious areas using

retention practices. The storage required

for water quality control is compared to

the storage required to control the

increased runoff volume. The greater of

the two volumes is the required retention

storage. Low-impact development also

provides pollution prevention by

modifying human activities to reduce the

introduction of pollutants into the

environment. (Title 11.03)

The ordinance allows applicants whopropose to use LID practices fordevelopment approvals a choice.Applicants of small development projectsmay accept permit conditions that fulfill

Island County Stormwater CodeLow Impact Development Requirements

OOrrddiinnaanncceess aanndd rreegguullaattiioonnss

the best management practices for LIDsurface water rate control in lieu ofsubmitting a drainage narrative. For majordevelopment activities and engineeredgrading projects, applicants who proposeto use LID drainage controls may submita drainage narrative instead of apreliminary drainage plan. The ordinancedoes not require a downstream analysiswhen the project design includes and isapproved for using LID standards.

To date, LID practices have been partiallyapplied in developments such as BayviewCorner (see page 26), but no majordevelopments have used LID technologiesin Island County.

CONTACTPhil CohenSurface Water Management Division Island County Public Works Phone: (360) 679-7331 extension 7440FAX: (360) [email protected]

40


BACKGROUNDThe city of Issaquah is growing rapidly.With annexations, the population couldincrease from 13,790 today to 47,000 by2020. Two urban villages alone—IssaquahHighlands and Talus—could add morethan 5,000 residential units, 3.5 millionsquare feet of commercial and office spaceand 500,000 square feet of retail space.This growth will place heavy demands onalready limited groundwater supplies, acongested road system and degradedstream ecosystems. Issaquah Creek is aregionally significant stream that provideshabitat for the threatened Puget Soundchinook salmon. In 2000, the city ofIssaquah adopted an update to thestormwater code (Title 13.28.055) thatprovides a process and criteria forevaluating low impact developmentproposals.

DESCRIPTIONThe municipal code authorizes theDirector of Public Works to authorizedeviations from stormwater designstandards to achieve “low impervioussurface development.” The director alsohas the option of requiring evaluation andmonitoring of project elements. The codelanguage is on the Municipal ResearchServices Center website (www.mrsc.org).Go to “Legal Resources,” then “City andCounty Codes,” then “City Codes” toIssaquah City Code Title 13.28.055.

Authorizations for deviation from designstandards are to be based on the followingcriteria. The policy states:

1. The deviations will produce a

compensating or comparable result in

stormwater flow control and treatment

that is in the public interest;

2. The deviations contribute to and are

consistent with the goal of achieving low

Stormwater Management Policyfor Low Impact DevelopmentCity of Issaquah

Island County Stormwater Code, continued

effective impervious surface area within a

development;

3. The proposed development project offers

reasonable assurances that low

impervious surfaces will be achieved and

maintained;

4. The deviations do not threaten public

health or safety;

5. The deviations are consistent with

generally accepted engineering and design

practices;

6, The deviations promote one or more of

the following:

a. Innovative site or housing design;

b. Increased on-site stormwater retention

using native vegetation;

c. Retention of at least 60 percent of

natural vegetation conditions over the

site;

d. Improved on-site water quality beyond

that required by current applicable

regulations;

e. Retention or re-creation of pre-

development and/or natural hydrologic

conditions to the maximum extent

possible;

f. The reduction of effective impervious

surfaces to the maximum extent

practicable;

7. The deviations do not allow density

greater than what would otherwise be

allowed under city regulations then in

effect;

8. The deviations do not present

significantly greater maintenance

requirements at facilities that will be

eventually transferred to public

ownership;

9. There shall be submitted in conjunction

with each such project, covenants,

conditions and restrictions which will be

binding upon the property all necessary

native growth protection easements,

impervious surface restrictions and such

other critical features as the Director may

require.

The Issaquah Municipal Code (Title 13.30)also provides an incentive for projects thatinfiltrate stormwater. Projects thatinfiltrate 100 percent of the stormwatercan receive up to a 50 percent reduction inthe stormwater utility fee.

On other fronts, the city is considering amore comprehensive sustainabledevelopment program, includingincentives. Some of these provisions relatedirectly to LID, such as green streets,green roofs, and pervious pavers.

CONTACTKerry RitlandCity of Issaquah(425) [email protected]

41

OOrrddiinnaanncceess aanndd RReegguullaattiioonnss

42


BACKGROUNDIn 1999, the Lacey city council enacted a“Zero Effect* Drainage Discharge”ordinance. Lacey, in Thurston County, hasa population of 31,000 and an urbangrowth area of 31 square miles. Cityofficials, understanding that even smallincreases in runoff can damage areastreams, chose to encourage developers toachieve zero discharge of stormwaterrunoff. This could well be one of the veryfirst ordinances of this kind passed in thenation.

DESCRIPTIONThe goal of Lacey’s ordinance is to retainthe critical functions of a forest includingevapotranspiration and infiltration aftersite development such that near zeroeffective impervious surface is achieved.The purposes of the ordinance show thatcity planners saw this as a new conceptthat would go through trial and evolution.

The ordinance states:

A.Provide those developing land the

opportunity to demonstrate zero effective

impervious surfaces.

B. Improve the conditions of habitat and

ground and surface waters within a

watershed with innovative urban

residential design and development

techniques.

C. Foster broad community acceptance of

the use of significantly less impervious

surface and greater natural habitat

conservation on sites.

D.Provide the opportunity to identify and

evaluate potential substantive changes to

land use development regulations which

support and improve natural functions of

watersheds.

The ordinance is flexible and establishesperformance standards for developmentrather than specific design criteria. A

committee of Lacey staff has the authorityto grant administrative variances fromtraditional standards to achieve theordinance’s goal.

Projects must preserve 60 percent naturalhabitat area and achieve “near zeroeffective impervious surface.” A variety ofpractices can contribute to meeting theprovisions of the ordinance, such as:• Constructing narrower roads without

curb and gutter.• Using pervious paving systems.• Using native forest as the stormwater

management system.• Avoiding discharges from impervious

surfaces to surface streams.

EXPECTED RESULTSThe intent of the ordinance is that projectsconstructed under this ordinance willeliminate overland flow discharges andhave no measurable impact on receivingwaters and aquatic life. Such projects willbe more aesthetically pleasing, requirelittle or no erosion control duringconstruction, and add value to the city.

CONTACTSEric HielemaCity of Lacey(360) [email protected]

Website: www.wa.gov/lacey/main_menu/main_set.html

Website for Chapter 14.31 Zero EffectOrdinance: www.wa.gov/lacey/lmc/lmc_main_page.html


* Zero Effect (orImpact)Development (ZID)means a projectthat adheres to the60/0 developmentstandard and isconstrained bycharacteristics of ahealthy watershedas described in theSalmon in the CityConferenceAbstracts.“60/0”means 60 percentforest coverpreserved /zeroeffectiveimpervious surface.

Zero Effect Drainage Discharge OrdinanceCity of Lacey

43


BACKGROUNDOlympia, with a population of 41,000, is arapidly growing city in Thurston County.Despite a variety of measures enacted inthe 1980s and 1990s to increase densityand protect environmental quality, thequality and diversity of aquatic habitat inthe city continued to decline.

In 1998, Olympia undertook a process to“define the balance between humanactivities and protecting habitat” in itsstreams and watersheds. After reviewingall city watersheds, the city councildecided to focus on the 2,600-acre GreenCove Creek watershed in west Olympia.In October 2001 the Olympia City Counciladopted a unique set of mandatory lowimpact development regulations toprevent further damage to aquatic habitatfrom urban development in the GreenCove Basin.

DESCRIPTIONOlympia elected officials and staff wentthrough a three-year process of research,analysis and peer review in designing theprogram for Green Cove Basin. Followingis a summary of the major steps: • Consultants developed criteria for

evaluating the viability of aquatichabitat in Olympia’s eight watershedsand recommended goals for growthand habitat based on the habitatpotential of each basin.

• A team of scientists, includinghydrologists and biologists, reviewedand concurred with the consultant’srecommendations.

• The city council agreed to use therecommended approach in the GreenCove Basin as a pilot project andadopted interim standards for zoning

density, stormwater management,timing of clearing and grading, and treeremoval.

• Consultants developed alternate siteplans for two proposed developmentsin the basin to determine whether theycould achieve low impact objectives.The city also consulted with realtors,development engineers, bankers, anddevelopers on the site plans.

• The science team reviewed thestandards and proposed designs andconfirmed that the proposedsubdivision designs were generallyconsistent with scientific findings andthat implementation would have thepotential to maintain habitat conditionsequivalent to the present.

Based on the above process, the OlympiaCity Council completed a comprehensivepolicy revision covering developmentdensity, impervious surface coverage, lotsize, open space/tree retention, streetdesign, street width, block sizes, parking,sidewalks, and stormwater managementrequirements. The following is an outlineof key policy changes for the Green CoveBasin.

Comprehensive Plan Amendments• Designate Green Cove Creek as a

sensitive drainage basin.• Avoid high-density development where

new development would have asignificant adverse impact upon thehabitat within designated sensitivedrainage basins.

• Administer development regulationsthat protect critical areas anddesignated sensitive drainage basins.

• Adopt low impact developmentregulations within designated sensitivedrainage basins that may include

Low Impact Development Strategy for Green Cove BasinCity Of Olympia

44


stormwater standards, critical arearegulations, zoning designations andother development standards.

• Establish street designs that minimizeimpacts to the natural environmentespecially within a designated sensitivedrainage basin.

Olympia Municipal Code• Establish a new zoning district with

increased tree protection andreplacement requirements.

• Establish residential densities of two tofour units per acre; allow duplexes,townhouses, and multifamily uses.

• Reduce lot widths and rear setbacksand increase maximum building heightscompared to other residential districts.

• Limit maximum impervious surfacecoverage per lot to 2,500 square feet.

• Allow several land uses, includingduplexes and parking lots that are nottypically permitted in single-familyresidential developments.

• Require a minimum tree density of 220trees per acre (approximately 55 percenttree cover in any given development).

Development Guidelines and PublicWorks Standards• Residential block perimeters cannot

exceed 1,700 feet.• Driveways and sidewalks can be

constructed of pervious surfaces withcity approval.

• Sidewalks are required on one side oflocal access streets.

• Sidewalk planter widths can beincreased from the required eight feet toan optional 25 feet.

• Additional parking within low impactdevelopments can be provided by theconstruction of pervious surface lotssubject to city approval.

• A rock infiltration gallery/conveyancesystem is to be constructed when streetslopes are 5 percent or less.

• Neighborhood collector streets are to be25 feet wide, with parking provided onalternating sides of the street.

• Local access streets are to be 18 feetwide, with similar parkingarrangements.

Drainage Design and Erosion ControlManual• Stormwater discharge must be

controlled by matching developeddischarge durations to pre-developeddurations, for the range of pre-developed discharge rates from 50percent of the two-year peak flow to the50-year peak flow.

• The city will allow clearing and gradingwithin the basin only between May 1and October 1 of any given year.

Since part of the Green Cove Basin is inThurston County, the county adoptedpolicy and regulatory changes tocomplement Olympia’s program. Thisincluded changes to the county’scomprehensive plan, zoning, and openspace program.

Unlike LID ordinances in Lacey andTumwater that are voluntary, Olympia’sGreen Cove regulations are mandatory. Asof October 2002, the city has received twosubdivision projects for developmentunder the new policies.

CHALLENGESSeveral questions remain unresolved inthe Green Cove basin process. The extracosts of non-standard developmenttechniques have not been defined. Onequestion is whether home buyers will buyhomes in a “low impact” neighborhoodwith narrower streets, less parking,smaller home footprints, and regulatorylimits to additions that would increaseimpervious surfaces. Finally, there are stillquestions about the environmental

LID Strategy—Green Cove Basin, continued

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benefits of the development restrictions,given the overall pattern of developmentand previous disruption of the naturalhydrology.

CONTACTAndy HaubCity of Olympia Public Works (360) [email protected]

For a more detailed case study and a CD-ROM containing project reports andordinances, contact the City of Olympia.

Low Impact Development RegulationsPierce CountyBACKGROUNDUnincorporated Pierce County has apopulation of 330,000 and a land area of1,790 square miles. The county isexploring the use of low impactdevelopment techniques as a method tomaintain natural hydrologic functionsduring the land development process andreduce impacts associated withconventional stormwater managementmethods. County staff is evaluatingvarious LID methods for quality ofperformance and applicability.Development of an LID chapter within thecounty’s Stormwater and SiteDevelopment Regulations will clarifywhat LID techniques are acceptable andwill establish a performance goal andobjectives. This chapter will also providecertainty to land developers and federaland state agencies in terms ofperformance measures and compliancewith National Pollutant DischargeElimination System requirements.

DESCRIPTIONPierce County, in cooperation withWashington State University Cooperative

Extension, is currently developing an LIDchapter for the Stormwater Managementand Site Development Regulations. Acommittee review of the proposal wasunderway at the time of this writing inlate 2002.

The following draft chapter establishes aperformance goal and objectives andprescriptive standards for LID.

The goal of Low Impact Development is to

manage stormwater generated from new

development and redevelopment so there

will be no negative impacts to adjacent

and/or downstream property owners and no

degradation to groundwater or surface

waters such as but not limited to streams,

ravines, wetlands, potholes, and rivers.

The Low Impact Development goal shall be

achieved through adherence to the following

objectives:

• Maintain and/or restore the pre-

developed, undisturbed stormwater flow

volumes, flow frequencies and durations,

and water quality from a developed site.

In the Puget Sound lowlands, the

predeveloped hydrologic condition is near

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zero overland flow runoff. (Note: To

provide a quantifiable and measurable

standard for flow control, minimum

requirement #7 Flow Control of the

Department of Ecology Stormwater

Management Manual for Western

Washington, will be adhered to in

addition to meeting the other objectives

listed below. It states that stormwater

discharges shall match developed

discharge durations to predeveloped

durations for the range of predeveloped

discharge rates from 50% of the 2-year

peak flow up to the full 50 year peak

flow.)

• Establish the pre-developed condition of

a site used for hydrologic modeling as

the native vegetation and soils that

existed on the site prior to 1800 A.D.,

which shall be a forested land cover

unless reasonable, historic information

indicates the site was prairie prior to

settlement (modeled as “pasture” in the

Western Washington Hydrology Model.)

• Retain or restore native soils and

vegetation on 65% of the site area.

Where 65% is not achieved the applicant

will demonstrate how the combined use

of other LID techniques will achieve the

overall goal.

• Limit the effective impervious area of the

site to no more than 10%.

• Retain and incorporate natural site

features that promote infiltration of

stormwater on a developed site.

• The use of traditional conveyance and

pond technologies to manage stormwater

quality and quantity should only be

considered after all other LID techniques

have been considered and used to the

greatest extent possible.

• Use bioretention, pervious surfaces, open

space surface water dispersion, soil

restoration, and other dispersed facilities

to control stormwater as close to the

origin as possible.

To meet the goal and objectives, the draftchapter discusses how LID can beconsidered at each phase of developmentincluding: site planning; vegetationretention and reforestation; site clearingand grading; roads, parking andsidewalks; and building design. It alsoprovides best management practices andmonitoring requirements. In addition, thechapter will address ongoingmanagement and maintenance needs, andeducation of homeowners.

Pierce County, in cooperation withWashington State Cooperative Extension,has entered into a partnership with aprivate developer to develop an LID pilotproject. For more information on thisproject, see Meadow on the Hylebos, page32, or call Len Zickler, AHBL, at (253) 383-2422.

LID Regulations—Pierce County, continued

Example of a sitedesign using LIDtechniques.

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Reduced Discharge HousingDemonstration ProgramSnohomish CountyBACKGROUNDIn the 1990s, Snohomish County, with apopulation of 628,000, established aprogram to introduce differentdevelopment schemes, such as mixed use,affordable housing and innovativedesigns. As part of this effort, the countyadopted the Reduced Discharge HousingDemonstration Program (Ordinance 00-004) in April 2000. This program providesa three-year trial period for selecting andoverseeing demonstration low impactdevelopment projects.

DESCRIPTIONThe reduced discharge ordinance has fivepurposes: 1. Demonstrate the benefits of alternative

development practices that reduceoffsite discharge.

2. Improve the conditions of habitat,ground and surface waters.

3. Foster community acceptance ofhousing that conserves habitat and usesless impervious surface.

4. Allow flexibility in the developmentstandards.

5. Identify and evaluate desirable changesto the land use code.

Requirements and guidelines in theordinance provide for a variety of LIDconcepts, such as infiltration, treeretention, density bonuses, smallerfootprints/taller house designs, permeablepavements, grass pavers, and minimizinggrading and site disturbance.

The county established a specialcommittee to oversee the program, selectdemonstration sites and recommendchanges to the land use code. Thecommittee includes representatives ofcounty departments, environmentalorganizations, university faculty, and thedevelopment community. The committeebegan its work with a tour of low andreduced impact development sites inSnohomish and King counties. SnohomishCounty sites included the Canyon ParkBusiness Center (which uses bioswales forwater quality treatment and groundwaterrecharge) and the Harbor Point MasterPlanned Community (which rechargesgroundwater through a wetland).

CONTACTSKatherine BrooksPierce County, Planning & Land Services(253) [email protected]

Hans HungerPierce County Public Works and UtilitiesWater Programs(253) [email protected]

Website:www.co.pierce.wa.us/pc/services/home/property/pals/landuse/esa.htm (see Title 17A amendments)

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To guide submittal of developmentproposals, the committee developed anoutline of minimum requirements and aproject review checklist (available from thecounty on request). By the end of 2002,developers had proposed six projectdesign concepts. The county accepted threeof these projects into the system. Theproject rating system evaluates treeretention (minimum 60 percent of the site);impervious surfaces; infiltration (minimum70 percent); visual impact; innovation; andthe reputation of the developer.

One project proposal is for higher-endfourplex condominiums. The site is heavilyforested with steep slopes and outwashsoils. A vertical design with undergroundparking and narrower roads will save treecover and reduce runoff. Permeablepavement will reduce impervious coverand soils will be amended with compost.The county will need to modify the zoningcode from the current single-familyclassification to allow for this type ofdevelopment in this area.

The second proposal, Wandering Creek, isfor lower cost single-family housing. Thesite is bounded by wetlands on threesides. The upland area is on outwash soilsand will drain to a wetland buffer. LIDfeatures include preserving overstoryvegetation, working with topography,narrowing the road section, usingpermeable pavers, and reducing buildingfootprints to 1,000 square feet.

A third proposal is in an existing platwhere the developer proposes torevegetate a pasture area with trees.

County staff and the developers willjointly monitor each of the developmentprojects for stormwater flows. Results willbe available to the public onceconstruction begins.

CHALLENGESThe county’s demonstration program hasfaced several challenges inimplementation. Developers andengineers have proven reluctant to trynew approaches and techniques. They alsostate that the Department of Ecology’sStormwater Management Manual for WesternWashington limits the use of wetlands forinfiltration.

COSTSCost estimates for these LID projects arehighly variable and site-dependent. Thefourplex project on a steep slope will beexpensive due to the vertical design andunderground parking, but the site wouldbe difficult to develop without theflexibility provided under the LIDprogram. The single-family housingproject is expected to be less expensivethan a traditional development because ofreduced road width and sidewalks on oneside of roads. The developer is alsoreceiving a density bonus, which allowshim to add several housing units on thesite.

CONTACTRandy SleightSnohomish County Planning andDevelopment Services(425) 388-3424 extension [email protected]

Reduced Discharge Housing, continued

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BACKGROUNDThe city of Tumwater in Thurston Countyhas a population of 12,730 and an area of10.7 square miles. Several years ago, cityofficials and staff recognized therelationship between traditionaldevelopment practices and streamdegradation, and established alternativedevelopment standards to protect aquaticlife in receiving waters.

DESCRIPTIONIn 2000, Tumwater enacted the Zero EffectDrainage Ordinance (Title 13, Chapter13.22). The city found that typical sitedevelopment hinders stormwaterretention, that stormwater dischargesoffsite adversely affect stream habitat, andthat retaining forest canopy aidsevapotranspiration and infiltration ofstormwater runoff. The ordinanceprovides developers with the option ofusing zero impact development* practicesin residential and commercial projects. Aset of performance guidelines indicatesthe characteristics of an acceptable project.

While the ordinance contains designguidance it also allows design creativity. Acommittee reviews project proposals andcan approve variances to the city’sdevelopment code to accommodatenontraditional construction techniques.Projects approved under the ordinancemust preserve 65 percent of forest area onthe development site. Runoff must not becollected or discharged to surface water(thus achieving zero effective impervious

area). The guidelines encourage loopedone-way streets; narrow perviousdriveways; small, pervious garage aprons;and small home footprints. Roof runoffmust be infiltrated or mitigated. Tocompensate for narrower roads andreduced access for emergency vehicles,structures are required to meet morerigorous fire standards.

COSTSThere is the potential for substantial costsavings for projects that might beapproved under this ordinance, howeverno cost analysis was performed.

CONTACTSMichael MatlockCity of Tumwater (360) 754-4210

Website: www.ci.tumwater.wa.us/ Follow the link to City Departments, then Planning and Facilities.


Zero Effect Development OrdinanceCity of Tumwater

*Zero ImpactDevelopmentmeans a projectthat adheres tothe 65/0 (65percent forestcover preserved /zero effectiveimpervioussurface)developmentstandard and isconstrained bycharacteristics of ahealthy watershedas described in theSalmon in the CityConferenceAbstracts.

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DESCRIPTIONThe Washington State Department ofTransportation is currently revising its1995 Highway Runoff Manual. As part ofthis revision, the department will developand reference three low impactdevelopment elements in therevised manual:1. Permeable paving at park and rides,

pedestrian paths, and lower speedroadways.

2. Bioretention along roadways.3. Constructed wetlands for stormwater

treatment.

The LID portion of the revised manualshould be available for use by the endof September 2003 and will include plans,specifications, methodology for estimatingcosts, and a hydraulic design process.

CONTACTSRick JohnsonWashington State Department ofTransportation(260) [email protected]

Larry SchaffnerWashington State Department ofTransportation(360) [email protected]

Website:www.wsdot.wa.gov/fasc/Follow the links to:>Engineering Publications>On-Line Technical Manual Library>Highway Runoff Manual

Low Impact Development in theHighway Runoff ManualWashington State Department of Transportation

Workers install Eco-Stone® permeablepavers at amunicipal park andride in Marysville.The WashingtonState Department ofTransportation isconsidering usingpermeablepavement, such asEco-Stone®, at itspark and rides andon pedestrian paths.

Eco-stone detail.

51

BACKGROUNDGreen building refers to a series ofpractices and use of materials that resultin a construction process and finishedproduct that causes less harm to theenvironment, is more resource and energyefficient, and provides a healthierenvironment for its occupants. One waythat the building industry and localgovernments are promoting greenbuilding is through green rating systems.In the Puget Sound Basin, two greenrating systems are most prevalent: • BUILT GREEN™ for residential

developments, multifamily, and singlefamily new construction andremodeling

• Leadership in Energy andEnvironmental Design (LEED™) forcommercial projects.

Both programs are included here becauseeach contains site design elements of lowimpact development.

BUILT GREEN™BUILT GREEN™ programs are market-based (what the consumer will pay)approaches to promoting green buildingpractices. Architects, builders, developers,subcontractors, suppliers, lenders, andreal estate agents use a rating system ofenvironmentally friendly practices tocertify that their homes offer reducedimpact on the environment and humanhealth. Because each program sponsordevelops checklists, considerablevariability can occur between certificationrequirements.

BUILT GREEN™ programs are located inDenver and in King, Snohomish,Kitsap and Clark counties in Washington.Denver’s program began in 1995 andincludes more than 4,000 environmentallyfriendly homes. The Master BuildersAssociation (MBA) of King andSnohomish Counties launched theirprogram in 2000, and it already includes1,753 new and remodeled homes. Theassociation expanded its program toinclude multi-family residences and hascertified more than 247 to date. KitsapCounty’s program, BUILT GREEN™/Builda Better Kitsap, started in 1997 andfeatures 100 homes. Clark County beganits Build a Better Clark program in 1998and has certified more than 60 homes.

The Master Builders Association of Kingand Snohomish Counties launched itsBUILT GREEN™ program in partnershipwith King County, Snohomish Countyand other government agencies.

Building projects are qualified using aBUILT GREEN™ checklist organized intosix categories of regionally appropriate,environmentally friendly action items.One of the categories—“Site and Water”—includes elements of low impactdevelopment: • Limiting heavy equipment to avoid

compaction of soils.• Preserving trees and existing

vegetation.• Protecting wetlands and other critical

areas.• Setting aside a portion of the site to be

left undisturbed.

GGrreeeenn bbuuiillddiinngg pprrooggrraammss

Green Building: Built Green™ and LEED™

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• Amending soils with compost to adepth of 8 to 10 inches.

• Managing water so that groundwaterwill be recharged.

• Limiting effective impervious surfacearea to 0 percent for projects of fiveacres or more and less than 10 percentfor projects less than five acres.

• Using pervious materials for at leastone-third of all driveways, walkwaysand patios.

• Using green roofs.• Avoiding impervious surfaces outside

the building footprint.

Builders use this checklist prior toconstruction to determine which featuresto include in the home. When a buildercompletes construction, he or she sends asigned copy of the checklist to the MBA,certifying that the home contains theidentified features. Based upon thatbuilder certification and after reviewingthe application, MBA will award theappropriate Certificate of Merit indicatingthat the home has received a 1-, 2-, or 3-star rating.

The city of Seattle and King Countypromote the use of the BUILT GREEN™rating system by sponsoring exhibits andpromoting the program through print,radio and TV media. In addition, SeattleCity Light and Seattle Public Utilitiessponsor a BUILT GREEN™ IncentiveProgram for multifamily projects. Theprogram provides financial assistance tobuilding owners and developers thatincorporate sustainable building goalsearly in building, programming, anddesign decisions. Incentive funding islimited to covering incremental designcosts, such as rating systemdocumentation or hiring professionals fordesign input or process facilitation, andmay not be used to cover constructioncosts. As part of this program, the city

helps identify sustainable buildingservices to offer to the private sector. BUILT GREEN™/Build A Better Kitsapgrew out of a partnership between theHome Builders Association of KitsapCounty and Kitsap County Public Works.Kitsap County Public Works and theWashington Department of Ecologyprovided financial support. BUILTGREEN™/Build A Better Kitsap addressesenergy efficiency, indoor air quality, healthand sustainable construction practices.There are separate checklists forhomebuilders, remodelers, developers andlight commercial. Each checklist hassections that relate to stormwater andinclude some low impact developmentpractices, such as:• Limiting impervious surfaces to 3,000

feet.• Protecting 20 percent of the site from

clearing and grading.• Using permeable pavement for

driveways, walkways and patios.• Providing infiltration for rooftop runoff.• Preserving existing native vegetation.

BUILT GREEN™/Build a Better Kitsapalso produced brochures for homeownerson “How to Shop for a Fish FriendlyHome” and “How to Maintain a FishFriendly Home.” The items listed in thesebrochures are different from thoseincluded on the BUILT GREEN™/Build ABetter Kitsap certification checklist.

BUILT GREEN™ CONTACTS:King/Snohomish Counties

General BUILT GREEN™ information:www.builtgreen.net

Master Builders Association of King and Snohomish CountiesRobin Rogers(425) 451-7920 or (800) [email protected]

Built Green™ and LEED™, continued

53

GGrreeeenn BBuuiillddiinngg PPrrooggrraammss

Website: www.mba-ks.com

Home Builders Association of Kitsap CountyArt Castle(360) 479-5778 [email protected]

Website: www.kitsaphba.com/bbk.html

Leadership in Energy and Environmental Design(LEED™)LEED™ is a national rating system forcommercial building projects sponsoredby the U.S. Green Building Council.Projects achieve LEED™ Certified Silver,Gold or Platinum rating levels based onthe number of points achieved in fivedifferent areas: • Sustainable sites.• Water efficiency.• Energy and atmosphere.• Materials and resources.• Indoor environmental quality.

Version 2.1 (November 2002) containselements of low impact developmentunder the sustainable sites and waterefficiency categories and includes:protecting open space, reducing thedevelopment footprint, exteriorlandscaping to reduce heat islands (suchas a green roof), and use of water efficientlandscaping (native plants). However,unlike many elements in other categories,the program does not require performancetargets (such as protecting 50 percent ofopen space, or limiting impervious surfaceto by 10 percent) for these practices.

Certification is currently available forcommercial projects, but the U.S. GreenBuilding Council is developing ratingsystems for residential, commercialinterior redesigns, and operationsapplications.

King County recently adopted the LEED™Rating System as a standard for allbuildings that the county constructs,remodels, and renovates. The city ofSeattle’s Sustainable Building Policy statesthat all new city-financed buildings andmajor remodels with more than 5,000square feet of occupied space shall achievethe Silver Level using the LEED™ RatingSystem. Seattle City Light and SeattlePublic Utilities also operate a LEED™Incentive Program to encourage use ofLEED™ in the private sector. Incentivefunding is limited to covering incrementaldesign costs, such as rating systemdocumentation or hiring professionals fordesign input or process facilitation, andmay not be used to cover constructioncosts. Buildings within City Light’s serviceterritory are eligible to apply.

LEED™ CONTACTS:U.S. Green Building Council Website:www.usgbc.org Select the link to “LEED”

Peter DobrovolnyCity of [email protected]

Website: www.cityofseattle.net/sustainablebuilding

Karen PriceBusiness and Industry Resource Venture(within Seattle)[email protected]

website: www.resourceventure.org

King County website:dnr.metrokc.gov/swd/bizprog/Follow the link under ConstructionRecycling/Green Building to “GreenBuilding Techniques.”

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amended soil Soil with compost tilled in to restore natural capacities to treat, store andinfiltrate water. Amending soil reduces runoff, promotes plant health andreduces needs for watering and application of fertilizers and herbicides.The Stormwater Management Manual for Western Washington (BestManagement Practice T5.13) recommends tilling in 10 percent dry weight ofcompost into the top 8 inches of topsoil and breaking up at least 4 inches ofsubsoil below this.

bioretention A vegetated depression located on the site that is designed to collect, storeand infiltrate runoff. Typically includes a mix of amended soils andvegetation.

curvilinear A curving street design that provides room for bioretention areas or othertreatment systems, slows traffic and creates a more attractive street.

detention system Temporary storage of stormwater to control the rate of release, allow forinfiltration and provide treatment.

evapotranspiration A process where vegetation absorbs, uses and releases water.

facultative plants Plants capable of adapting to varying environments.

filtration A process in which filtering, or treatment, takes place.

hydrology Scientific study of the properties, distribution and effects of water on theEarth's surface, in the soil and underlying rocks, and in the atmosphere.

hydrophilic plants Vegetation adapted to wet conditions.

impervious surfaces Hard surfaces, such as rooftops, roads and parking areas, that prevent orslow infiltration of water. Lawns with underlying soils compacted by heavymachinery are considered impervious.

infiltration Downward movement of water from land surfaces into the soil.

pervious or permeable surfaces Soil or other material that allows infiltration or passage of water or otherliquids.

Salmon in the City Conference Conference sponsored by the American Public Works Association,Washington Chapter, in 1998 that featured presentations addressing theintersections of salmon, salmon habitat and urban development. Abstractsfrom this conference are available at:http://depts.washington.edu/cwws/Research/Reports/salmoninthecity.pdf.

Smart Growth Collection of land use planning techniques that features compact, mixed-use, transit-oriented development with the objective of creating moreattractive, livable, economically strong communities while protectingnatural resources.

swales Open, vegetated drainage channel designed to detain, treat and/or infiltratestormwater.

turbid or turbidity Sediment, organic matter or other particles that reduce the clarity of water.Excessive turbidity in streams and other surface waters can directly impairthe growth of aquatic vegetation, and indirectly lead to degraded fish andwildlife habitat and decreased oxygen in waters.

Glossary

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