Low Impact Development in Northern Nevada: An Introduction

Size: px

Start display at page:

Download "Low Impact Development in Northern Nevada: An Introduction"

Irma Gray
5 years ago
Views:

Nonpoint Eduction for Municipl Officils www.unce.unr.

open spce PROTECTS wterwys AIDS in groundwter rechrge REDUCES trditionl storm drin infrstructure Copyright 2009, University of Nevd Coopertive Extension. All rights reserved.

it rins or when snow melts, there is often enough wter to result in flow from rods, drivewys, sidewlks nd other impervious surfces into the storm drin system.

1 Nonpoint Eduction for Municipl Officils Protecting wter qulity through community plnning Fct Sheet FS Low Impct Development in Northern Nevd: An Introduction Benefits of LID REDUCES nd CLEANSES urbn runoff CONSERVES wter nd open spce PROTECTS wterwys AIDS in groundwter rechrge REDUCES trditionl storm drin infrstructure Copyright 2009, University of Nevd Coopertive Extension. All rights reserved. By Susn Donldson, Wter Qulity Eduction Specilist Melody Hefner, Wter Qulity Progrm Assistnt w UNIVERSITY OF NEVADA COOPERATIVE EXTENSION hile we don t get lot of precipittion in northern Nevd, when it rins or when snow melts, there is often enough wter to result in flow from rods, drivewys, sidewlks nd other impervious surfces into the storm drin system. In ddition, ctivities such s lndscpe irrigtion with sprinklers, wshing your cr in the drivewy or wshing off your sidewlk often produce runoff tht drins into the storm drin system. Trditionl storm drin systems re designed nd constructed to convey wter sfely off the rod to void flooding nd trffic problems. They typiclly consist of connected system of impervious concrete curbs nd gutters, ctch bsins nd underground pipes. Unfortuntely, they generlly re not designed to lso improve runoff wter qulity. The wter flowing off rods nd other impervious surfces picks up ny pollutnts, such s oil drips, trsh, rod snd nd slts, nd metls from utomobile brkes. These pollutnts re then crried with the stormwter nd delivered, without tretment, into nerby wter bodies such s the Truckee River. As our communities grow, the totl mount of impervious surfce increses. This mens tht there is less open lnd vilble to bsorb, store nd tret stormwter. At the sme time, we re incresingly chllenged to mintin or improve wter qulity in locl creeks nd rivers so tht we cn continue to enjoy high-qulity drinking wter nd opportunities to swim, fish nd enjoy our wterwys. A strtegy clled Low Impct Development (LID) ws developed to llow us to continue to grow while voiding dditionl problems from polluted runoff. LID prctices cn lso be used to tret runoff from existing developed res. Bre slopes nd impervious surfces cn result in muddy runoff tht cn dmge rivers nd strems being fed by stormwter. Susn Donldson Wht Is Low Impct Development? Low Impct Development, or LID, is sustinble pproch to stormwter mngement tht minimizes impcts on wterwys. LID cn be integrted into Green Design or Smrt Growth or similr pproches to community design. It is flexible, site-specific, customized pproch tht uses

Pge 2 Low Impct Development in Northern Nevd: An Introduction LID is used becuse it is: vriety of site-design nd pollution-prevention techniques used by vegettion, or infiltrte nd rechrge groundwter

2 Pge 2 Low Impct Development in Northern Nevd: An Introduction LID is used becuse it is: vriety of site-design nd pollution-prevention techniques used by vegettion, or infiltrte nd rechrge groundwter the wter evportes. This results in less runoff nd fewer to compenste for the impcts in res where fvorble site pollutnts in stormwter, s EFFECTIVE in reducing nd of lnd development on site conditions exist. These effects compred with trditionl treting urbn runoff; hydrology nd wter qulity. re mximized where the site site-development prctices. is underlin by sndy soils. ECONOMICAL, when How does LID work? There re number of Minimize disturbnce less infrstructure is LID ttempts to mimic the wy bsic prctices ssocited with to the site required for LID prctices rinfll, snowmelt nd stormwter LID, from better site design to Nevd s soils re esily thn for trditionl runoff soked into the ground incorporting open spce nd erodible nd rely on ground cover, stormwter fetures; before site ws developed. cluster development, to specific lef cnopy nd plnt roots to Insted of conveying stormwter technologies. All the prctices retrd erosion. The effects of soil SIMPLE! directly into underground ttempt to chieve the following: disturbnce nd loss of ntive Most LID fetures re pipes, it is diverted onto open- vegettion from grding ctivities not highly engineered, spce res, into depressed Mimic predevelopment during construction cn lst for expensive or elborte; lndscping, or into other LID site hydrology long time, unless revegettion is fetures, where it infiltrtes. LID ttempts to reduce runoff successful. Erosion of the ground FLEXIBLE nd customized Pollutnts re broken down in by finding wys to infiltrte surfce contributes sediment for ech site; the soil by bcteri or tken up stormwter onsite, much s it to stormwter runoff. Sediment in plnts, providing system of did prior to development. The cn be source of excess USEFUL in chieving nturl pollutnt processing. hrvested wter soks into nutrients nd my lso contin multiple objectives: Runoff decreses when wter the ground, helping to irrigte toxic chemicls nd pthogens stormwter mngement, is stored in the soil pores. Some lndscping nd replenish deposited from site ctivities. lndscpe beutifiction, of the wter will evporte, be groundwter supplies. Some of Minimizing site disturbnce cn hbitt improvement, minimize new inputs of these open spce connectivity, nonpoint sources of pollution. etc.; nd Reduce impervious cover DESIRABLE, becuse it Impervious cover, s noted dds vlue when the previously, is ny surfce tht lndscpe fetures used prevents or limits the mount of to chieve LID gols wter tht soks into underlying re lso estheticlly soils. Impervious surfces plesing. This cn increse include rods, drivewys, property vlues. sidewlks, prking lots, roofs nd compcted soils. Reducing the mount of impervious surfces when possible llows Source: Puget Sound Action Tem more re for onsite stormwter infiltrtion. There re mny wys to reduce impervious cover. Insted of trditionl concrete, consider permeble sphlt or concrete pvement, pvers or grvel. Minimize street

Low Impct Development in Northern Nevd: An Introduction Pge 3 Wht re common LID prctices? Alge blooms cn result from inputs of runoff contminted with nutrients.

3 Low Impct Development in Northern Nevd: An Introduction Pge 3 Wht re common LID prctices? Alge blooms cn result from inputs of runoff contminted with nutrients. widths where pproprite, This my be s simple s directing llowing for emergency ccess. flow from drivewys onto lwns, Consider instlling sidewlks where the runoff will slow down on one side of the rod, nd some will infiltrte. Pollutnts rther thn on both sides. will be deposited nd processed nturlly. Stormwter cn lso Minimize connected be cptured in rin brrels or impervious cover cisterns or directed vi roof gutter This LID prctice seeks to downspouts to the vegetted interrupt the flow of stormwter res of the yrd, where the runoff by disconnecting the lndscping will benefit from ssocited impervious surfces. the dded wter. On lrger Susn Donldson scle, impervious cover cn be disconnected by using turf res, ntive lndscping or swles. Control stormwter s close to the source s possible By decresing flow cross impervious surfces, fewer pollutnts re trnsported into the storm drin system. Smllscle LID prctices cpture, store nd tret stormwter onsite. A wide suite of different LID prctices re vilble tht cn be customized to ech site. Some focus on improved site design, such s open spce nd cluster development designs. Others re specific fetures tht reduce nd tret runoff, including bioretention fetures such s rin grdens nd filter boxes or permeble pvements. The benefits of ech prctice vry, in terms of both the mount of pollutnt reduction tht cn be expected, nd the effects on pek flow volumes, volume reduction nd wter conservtion. The tble on pge 6 summrizes the generl benefits of vrious LID prctices. Literture-Reported Percent Removl Efficiency For Vrious Pollutnts LID Prctice Totl Suspended Solids Totl Phosphorous Totl Nitrogen Bioretention 75-90% 70-80% 65-80% Porous Pvement 70-90% 40-55% 10-20% Vegetted Buffers 10-74% 0-10% 0-15% Vegetted Swles 60-95% 5-45% 15-65% The tble bove presents summry of the literture-reported rnge of pollutnt removl efficiencies for vrious LID prctices. The rnge of removl efficiencies reflects differences in designs, vrible stormwter pollutnt concentrtions nd underlying soil properties. Source: Truckee Medows Structurl Controls Design Mnul, April 2007 updte.

4 Pge 4 Low Impct Development in Northern Nevd: An Introduction How much does LID cost? LID cn be very costeffective when compred to trditionl development prctices, prticulrly where soils re pproprite for infiltrtion. When incorported t the plnning stge, LID cn reduce the cost of grding nd stormwter mngement fcilities. Additionl svings cn occur if rod widths re minimized, lterntives to curb nd gutter designs re used nd other innovtive design techniques re pplied. In some cses, when lrge-scle detention bsins cn be eliminted, dditionl lots re freed for development. Lot vlues hve incresed in number of developments tht incorported LID, due to the esthetic vlue of dditionl open spce. Low Impct Development prctices help protect the clrity nd ecologicl helth of our wterwys. Preserve nd restore nturl lndscpe fetures Preserving nturl fetures, such s trees, vegetted strem buffers, ntive plnts nd nturl dringe chnnels, helps to reduce the potentil for erosion nd nonpoint pollution. Where nturl fetures cnnot be preserved, recreting or incorporting lndscpe nd dringe fetures tht mimic nturl fetures cn help reduce runoff nd process nonpoint source pollutnts. Fcilitte detention nd infiltrtion of stormwter Detining stormwter runoff to llow infiltrtion to occur cn be ccomplished using rin grdens nd other bioretention fetures, vegetted swles, lwn buffers or infiltrtion bsins. Ech of these lndscping fetures hs different benefits nd design requirements, but if designed correctly, ll will reduce nonpoint source pollution nd erosion nd improve infiltrtion. Distribute smll-scle prctices throughout the lndscpe Rther thn creting one lrge detention bsin within development, which tkes gret del of spce nd is often estheticlly undesirble, smll-scle prctices such s rin grdens or other bioretention fetures cn be incorported into the lndscping of ech dwelling. These multifunctionl lndscpes will improve wter qulity without loss of developble lnd. Terri Svetich Why do we need LID? Wterwys in northern Nevd wtersheds re subject to regultory limits on certin nonpoint source pollutnts, including nitrogen, phosphorus, totl dissolved solids nd other substnces. LID is one strtegy tht helps to decrese the mounts of these pollutnts delivered to locl wterwys by retining stormwter onsite, where pollutnt processing cn occur. The ddition of lrge res of mnmde impervious surfces nd the use of trditionl stormwter mngement systems hve lso resulted in mjor chnges in the volume nd rte of stormwter runoff. The trditionl storm drin system concentrtes flows nd delivers them quickly to djcent wterwys. Becuse the opportunity to infiltrte stormwter nd store it onsite is reduced, not only do storm flows rech wterwys erlier, but the volume of flow is lso incresed. This cn result in incresed erosion nd flooding in res tht previously were outside the nturl floodplin. Detention nd retention bsins cn be used to help decrese pek flows, but they typiclly do not infiltrte stormwter or process pollutnts.

5 Low Impct Development in Northern Nevd: An Introduction Pge 5 Detention, Retention or Infiltrtion: Wht s the Difference? Mster Plns, Low Impct Development prctices nd Stormwter Mngement Mnuls encourge incresing the detention, retention nd infiltrtion of stormwter runoff. While ll three terms re often used interchngebly, they re distinct prctices tht re used for different purposes. Detention is the temporry storge nd controlled relese of stormwter to reduce pek flows from developed sites. Stormwter is detined. Most commonly, detention bsin is constructed within development or t n offsite loction. They re generlly lrge nd serve severl homes or entire developments. Wter flows into the bsin through lrge opening such s storm drin pipe. Wter exits the bsin through smller opening, which slows the flow nd reduces pek flows from the site. The pek flow rtes leving the site should be comprble to those tht occurred Detention bsins collect nd slowly relese stormwter. during storm events before development took plce. While not generlly design feture, some infiltrtion my occur through the bsin floor. Some settling of suspended prticles nd debris will lso occur. Most often, detention bsins re designed so tht they will empty within 24 to 48 hours fter storm hs occurred. They re not prcticl or estheticlly plesing on individul sites or within the home lndscpe. Also, detention bsins typiclly do not reduce the incresed volume of stormwter produced by mnmde impervious surfces. Chris Conwy Retention is the permnent storge of portion of the stormwter produced by developed site to llow infiltrtion, evportion nd/or uptke of the wter by surrounding vegettion. Stormwter is retined. Retention generlly occurs in closed bsin or depression of some kind. While there is no outlet from the retention bsin for routine flows, n overflow structure must be designed to sfely bypss stormwter flows from lrge storm events. To llow infiltrtion nd prevent the long-term ponding of wter, retention bsins generlly must be engineered to provide sufficient dringe. This my involve removl of the existing soil nd subsoil nd replcement with grvel, snd nd/or mulch. Cre must be tken not to compct the imported engineered soils. Most municiplities hve limits on the length of time tht wter cn remin in retention bsin fter single event. These requirements re intended to reduce or prevent the breeding of mosquitoes or other vermin. Retention bsins cn be constructed on very smll scle nd re well-suited for individul home lndscpes. They cn lso be retrofit into existing lndscpes. Smllscle retention fetures tht incorporte plnt mterils re lso considered to be LID bioretention res. Rin grdens re one common type of bioretention re. Infiltrtion is the entry of stormwter into the soil profile. Stormwter is infiltrted. Under norml predevelopment conditions, infiltrtion occurs t vrying rtes depending on the type of soil nd vegettion present t the site. Some infiltrtion of stormwter my occur in trditionl erthen detention nd retention bsins. However, infiltrtion is often limited in these bsins due to compction of the soil during construction. Lrge infiltrtion fetures, such s infiltrtion trenches or infiltrtion bsins, re generlly engineered to improve the nturl infiltrtion. If they become clogged with silt nd debris, the infiltrtion rte will decline. The plnt roots in bioretention res provide pthwys for wter to infiltrte, which helps decrese the rte of clogging.

6 Pge 6 Low Impct Development in Northern Nevd: An Introduction For dditionl detiled plnning nd design informtion, refer to the ltest versions of the Truckee Medows Low Impct Development Hndbook nd the Truckee Medows Structurl Controls Design Mnul vilble t For description of vrious Low Impct Development prctices, consult the following Fct Sheets in the Low Impct Development in Northern Nevd series: LID: An Introduction, FS Soil Considertions, FS Rinwter Hrvesting, FS Bioretention, FS Vegetted Swles nd Buffers, FS Green Roofs, FS Plnt Mterils, FS Porous Pvement, FS Rodwy nd Prking Lot Design, FS Mintennce, FS For more informtion bout LID, see: Low Impct Development Center, Inc., Ntionl Institute of Building Sciences Whole Building Design Guide, Low Impct Development Technologies, Urbn Design Tools, Low Impct Development, U.S. Environmentl Protection Agency Polluted Runoff (Nonpoint Source Pollution), Low Impct Development (LID), Technicl review provided by Chris Conwy, Certified Professionl in Sediment nd Erosion Control. Type of LID prctice Benefits of LID Prctices Pek flow control Volume reduction Wter qulity improvement For more informtion Bioretention Rin grden FS Tree box filter FS Stormwter plnter FS Vegetted swle FS Vegetted buffer FS Green roof FS Porous pvement Porous concrete, sphlt FS Permeble pvers FS Rinwter hrvesting Rin brrels, cisterns FS Site design Nrrow rod design FS Downspout routed 1 FS Tree plnting FS-09-25, FS When downspout is routed to lndscping Copyright 2009, University of Nevd Coopertive Extension. All rights reserved. No prt of this publiction my be reproduced, modified, published, trnsmitted, used, displyed, stored in retrievl system, or trnsmitted in ny form or by ny mens electronic, mechnicl, photocopy, recording or otherwise without the prior written permission of the publisher nd uthoring gency. The University of Nevd, Reno is n Equl Employment Opportunity/Affirmtive Action employer nd does not discriminte on the bsis of rce, color, religion, sex, ge, creed, ntionl origin, vetern sttus, physicl or mentl disbility, or sexul orienttion in ny progrm or ctivity it opertes. The University of Nevd employs only United Sttes citizens nd liens lwfully uthorized to work in the United Sttes.

GREEN INFRASTRUCTURE FEASIBILITY STUDY NORTH BERGEN

GREEN INFRASTRUCTURE FEASIBILITY STUDY NORTH BERGEN ACKNOWLEDGEMENTS Designed to highlight green infrstructure opportunities within the Township of North Bergen, this document hs been prepred by the Rutgers