Guide to Erosion Control & Storm w ate r Manage m e nt for H om e ow ne rs & Contractors

Me sse r Pond, Ne w LondonApril 2008

Pre pare d by

CLD Consulting Engine e rs Inc.16 H e m lock Ridge Drive , Suite 103

Th e Village of W ilde rW h ite Rive r Junction, VT 05001

April 2008

Funding for th is proje ct w as provide d in part by a grant from th e NH De partm e nt of Environm e ntal Se rvice s w ith funding from th e US Environm e ntal Prote ction Age ncy

unde r Se ction 319 of th e Clean W ate r Act.

Table of Conte nts

Introduction

Be st Manage m e nt Practice s for Controlling Erosion

Non-Structural BMPs

Prote ct Se nsitive Environm e nts & Lim it Disturbance

Cluste ring & Minim izing Im pact

Re duce Im pe rvious Cove r

Disconne ct & Distribute Te m porary Erosion Control Me th ods

Silt Fe nce

Straw W attle s & H ay Bale s

Stone Ch e ck Dam s

Erosion Mat

Pe rm anant Erosion Control Me th ods

Rain Garde n

Ve ge tate d Sw ale

Stone Drip Edge

Le ve l Spre ade r

Bio-Re te ntion Are a

Mainte nance Sch e dule

A s im ple and be autiful m e th od of us ing s tone s and cre e ping ve ge tation to s tabiliz e a drainage ditch .

Introduction

Th e inte nt of th is guide is to h e lp both h om e ow ne rs and contractors to unde rs tand various Low Im pact De ve lopm e nt approach e s to s torm w ate r m anage m e nt and h e lp th e m inte grate th e s e approach e s into th e ir ow n s ite s in a s im ple m anne r.

Th is m anual lis ts and e xplains in de tail s e ve ral Be s t Manage m e nt Practice s (BMPs ) th at, w ith prope r im ple m e ntation and s im ple m ainte nance , w ill prote ct and m aintain th e vitality of Ne w H am ps h ire 's m ars h e s , s tre am s and lak e s .

Non-Structural BMPsTh is s e ction de s cribe s s ite planning and de s ign te ch niq ue s th at re duce th e im pact of

s torm w ate r and is cons ide re d th e firs t s te p in s torm w ate r m anage m e nt.

Te m porary BMPsTh is s e ction de s cribe s th e s e cond s te p in s torm w ate r m anage m e nt. Th e s e te m porary

s tructural BMPs are us ually utiliz e d during cons truction to re duce th e am ount of e ros ion th at occurs w ith dis turbe d or e xpos e d s and and s oil.

Structural BMPsTh is th ird s e ction de s cribe s th e actual fe ature s th at are cons tructe d on-s ite to

pre ve nt e ros ion and re tain and tre at s torm w ate r.

Th e re are th re e m ain se ctions in th is m anual th at cove r m e th ods of controlling e rosion and storm w ate r:

Purpose of th is Manual

Eros ion is th e m ove m e nt of s oil, s tone s and oth e r s e dim e nt due to th e e ffe cts of w ate r, w ind or ice .

Proble m s m os t ofte n occur w h e n land is de ve lope d.

Eros ion occurs naturally, but can be com e a proble m if your land s tarts w as h ing aw ay!

Eros ion and s torm w ate r pollution can not only affe ct your ow n pe rs onal prope rty, but oth e r prope rtie s dow ns tre am of your land. Rainw ate r lade n w ith s e dim e nt from an e rode d ditch can clog pond, s tre am , and lak e e cos ys te m s , m ak ing th e s e are as uninh abitable for fis h , frogs and oth e r w ildlife .

By controlling e ros ion and tre ating s torm w ate r, you are doing your part to prote ct and pre s e rve th e s e h abitats !

By s trate gically placing natural s tone s and ve ge tation, th e pos s ibility of e ros ion in th is drainage s w ale w as ne arly e lim inate d!

H ow doe s th is affe ct m e ?

An e ros ion gully cre ate d by a rains torm .

Storm w ate r is s urface w ate r produce d from a rain e ve nt th at can contain s e dim e nt and ce rtain pollutants . Storm w ate r m anage m e nt is th e practice of controlling and tre ating th e pollute d rain runoff.

Eros ion Control is th e m e th od for pre ve nting e ros ion, or th e m ove m e nt of s e dim e nt.

H ow about e rosion control and storm w ate r m anage m e nt?

W h at is e rosion?

Land de ve lopm e nt and ne w cons truction are th e large s t contribute rs to pollute d lak e s and s tre am s due to th e e ros ion of dis turbe d and uns tabiliz e d s oil. Eve n digging a large h ole in your yard for your ne w pool m ay caus e e ros ion if th e s oil is not s tabiliz e d corre ctly.

Re ad on for h ow to s tabiliz e dis turbe d s oil...

H ow to ide ntify land at risk for e rosion?

Be st Manage m e nt Practice s for Controlling Erosion

W h at is a Be st Manage m e nt Practice ?

A Be s t Manage m e nt Practice , als o k now n as a BMP, is a fe ature , cons tructe d on-s ite , th at controls e ros ion and s torm w ate r runoff.

Th is m anual addre s s e s BMPs us e d to control and m anage s torm w ate r. It is im portant to prote ct your building s ite from e ros ion and to pre ve nt th e pollution of ne arby s tre am s , rive rs , ponds , and lak e s .

Storm w ate r BMPs provide s im ple m e th ods inte nde d to accom plis h th e s e goals th rough Te m porary and Pe rm ane nt Eros ion Controls .

A s e dim e nt lade n rive r e m tpie s into a lak e . Th e re s ult on h abitats in and around th e lak e can be dis as trous .

Be s t Manage m e nt Practice s us e d on your prope rty w ill prote ct be autiful natural re s ource s in your are a.

Te m porary vs. Pe rm ane nt Stabilization

Te m porary s tabilization m e th ods are inte nde d for us e during and im m e diate ly afte r cons truction. Th e s e fe ature s h e lp h old dis turbe d s oil in place to pre ve nt e ros ion and th e m ove m e nt of s e dim e nt off-s ite .

Pe rm ane nt e ros ion control and s torm w ate r m anage m e nt fe ature s are de s igne d to re m ain in place long afte r s ite grading and cons truction is com ple te . Th e s e fe ature s control s torm w ate r runoff from roofs , roads and de ve lope d are as by s low ing th e ve locity and re m oving any s e dim e nt th at is be ing carrie d in th e s torm w ate r.

Non-Structural BMPs are not typically ph ys ical fe ature s th at are de s igne d into th e s ite but m ore lik e ide as or cons ide rations th at th e h om e ow ne r, e ngine e r or contractor us e in s ite planning and building.

Pe rh aps th e m os t de fining dis tinction for Non-Structural BMPs is th e ir ability to pre ve nt s torm w ate r ge ne ration in w ays oth e r th an th rough us e of conve ntional de ve lopm e nt practice s w h e re as Structural BMPs alle viate th e inte ns ity of th os e s torm w ate r im pacts th at cannot be pre ve nte d and/or avoide d. (Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual, April 2006)

Re ad on for m ore inform ation...

Exce s s ive land cle aring and im pe rvious are a as w e ll as a large am ount of unprote cte d e xpos e d s oil .. th is s ite is s ure to h ave proble m s in th e ne ar future .

W h at are Non-Structural BMPs?

Non-Structural BMPs

Alth ough th is particular h ous e is a fe w ye ars old, th is s ite is w e ll prote cte d, re taining as m uch natural ve ge tation as pos s ible and cre ating a m inim al am ount of dis turbance to th e s ite .

In orde r to m inim iz e s torm w ate r im pacts , land de ve lopm e nt s h ould avoid im pacting and e ncroach ing upon are as w ith im portant natural s torm w ate r functional value s s uch as floodplains , m ars h e s , s tre am s , lak e s , and ponds w h e re e ve n s m all ch ange s in w ate r q uality can h ave a de vas tating e ffe ct on th e local e cos ys te m . Th is is typically e as ily accom plis h e d s ince m os t tow n re gulations h ave s tre am and lak e building s e tback s in place for th is re as on.(Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual, April 2006)

Prote ct Se nsitive Environm e nts and Lim it Disturbance

A re ce nt tw o-lot s ubdivis ion de ve lopm e nt de fine s th e buildable are a to re tain a ve ge tate d buffe r be tw e e n dis turbe d are as and w e tlands .

Acce s s to th e lots is provide d by a s h are d drive w ay, re ducing th e am ount of im pe rvious and dis turbe d are as .

Clus te r de ve lopm e nts us ually re fe r to large s ubdivis ion com ple xe s w h e re a tow n’s zoning ordinance allow s for s m alle r, m ore conde ns e d de ve lopm e nt and th e re fore m ore ope n s pace , but th e conce pt of clus te ring can be us e d e ve n on th e s m alle s t h om e s ite . By cons olidating h ous e and garage , m ak ing th e park ing are a large e nough for only w h at is ne e de d and cle aring only w h at is ne ce s s ary, th e h om e ow ne r can re tain a s ubs tantial am ount of natural ve ge tation. Undis turbe d ve ge tation ge ne rate s far le s s s torm w ate r th an a gras s e d law n are a.

By tak ing th e s pe cific lot ch aracte ris tics into cons ide ration in th e de s ign proce s s , a h ous e can be cons tructe d to “fit” th e lands cape ins te ad of re q uiring a large am ount of dis turbance to fit th e lands cape to th e h ous e . Anoth e r m e th od is to cle ar out only w h at tre e s are abs olute ly ne ce s s ary to build, th is w ill e lim inate th e ne e d for an e xce s s ive am ount of s e e ding and lands caping afte r cons truction is com ple te .

Th e e lim ination of traditional law ns can be an e xtre m e ly difficult BMP to im ple m e nt, s ince th e traditional law n is an e s s e ntial lands cape de s ign fe ature th at is e m be dde d in th e curre nt national culture . H ow e ve r, a s im ple and be autifully lands cape d are a can be m uch e as ie r to m aintain as w e ll as m uch be tte r for th e e nvironm e nt.(Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual, April 2006)

Cluste ring and Minim izing Im pact

Conve ntional Lot De ve lopm e nt Minim um Im pact Lot De ve lopm e nt

Sim ply m inim iz ing th e am ount of im pe rvious s urface s , s uch as roofs , drive w ays or patios , can dras tically re duce th e am ount of s torm w ate r ge ne rate d on s ite . Th is s traigh tforw ard m e th od e lim inate s th e ne e d for re -ve ge tating an are a w ith tre e s , s h rubs or lands caping.

Anoth e r m e th od of re ducing im pe rvious cove r is th e ins tallation of pe rm e able pave m e nt or pe rm e able pave rs . Pe rm e able pave rs are lik e concre te block s th at allow for s torm w ate r to s e e p into th e ground th rough th e crack s or h ole s in th e paving block s , as oppos e d to rus h ing dow n a pave d drive w ay, carrying s e dim e nt and caus ing e ros ion. Pe rm e able pave m e nt is s im ilar to re gular pave m e nt e xce pt th at th e as ph alt binde r cours e allow s for s torm w ate r to infiltrate th rough th e pave m e nt and into a cours e grave l be d be low . For m ore inform ation, s e e th e Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual online at h ttp://w w w .de p.s tate .pa.us /de p/s ubje ct/advcoun/s torm w ate r/Manual_ DraftJan05/Se ction06-StructuralBMPs -part1.pdf(Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual, April 2006)

Re duce Im pe rvious Cove r

W h e n re -ve ge tating dis turbe d are as , be s ure to us e native s pe cie s of tre e s , s h rubs , and lands caping plants . Th is w ill e lim inate or re duce th e ne e d for fe rtiliz e rs and pe s ticide s .

By dis conne cting s torm w ate r from a m unicipal drainage s ys te m , h om e ow ne rs can ins te ad dire ct rooftop or drive w ay runoff aw ay from th e ir h ous e and dis tribute it to ve ge tate d are as th at allow for tre atm e nt and/or infiltration. Th is m e th od re duce s th e ris k of e ros ion due to large am ounts of s torm w ate r trave lling at a h igh ve locity. Managing s torm w ate r on s ite re duce s th e ne e d for cons tructing m unicipal facilitie s , w h ich w ould cre ate m ore dis turbe d are a.(Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual, April 2006)

Disconne ct and Distribute

Rain Barre ls are a s tructural BMP th at contain roof runoff and s tore it for us e as irrigation.

A re s ide ntial drive w ay us ing pe rm e able pave rs .

Silt Fe nce

Silt Fe nce is a te m porary barrie r of filte r cloth attach e d to s upporting pos ts . Th e bottom of th e Silt Fe nce is e ntre nch e d into th e s oil and it is us e d to inte rce pt s e dim e nt lade n runoff from dis turbe d are as .("Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook ”, 7-161)

W h at is Silt Fe nce ?

Silt Fe nce is to be us e d during cons truction to pre ve nt s e dim e nt and oth e r pollutants from le aving th e s ite . It s h ould be place d on th e dow nh ill s ide at th e e dge of dis turbe d s oils and s h ould be long e nough s o th at s torm w ate r cannot bypas s th e fe nce around th e e nds . ("Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook ”, 7-161)

H ow can I incorporate Silt Fe nce into m y site de sign?

H ow do I install Silt Fe nce ?You s h ould be able to purch as e Silt Fe nce w ith pos ts from your local cons truction s upply s tore . Start by digging a 6" de e p by 6" w ide tre nch along th e line w h e re th e Silt Fe nce w ill be ins talle d. Lay out th e Silt Fe nce along th e tre nch and drive th e pos ts into th e ground, s tre tch ing th e fabric tigh t be tw e e n e ach pos t. Once th e tre nch is back fille d, th e bottom of th e Silt Fe nce s h ould be burie d at le as t 6 inch e s de e p to proh ibit s torm w ate r from trave lling unde r th e fe nce .

Te m porary Stabilization

Silt fe nce h as be e n ins talle d along th e lim it of dis turbance (th e e dge of ne w ly grade d s oil) to pre ve nt s e dim e nt trave l.

Structural BMPs - Te m porary

Erosion Mat

Eros ion Mat is com pos e d of tw o flat ne ts th at h old s traw m ulch in be tw e e n th e m , w h ich acts lik e a blank e t to prote ct your ne w ly grade d, s loping yard from los ing it's pre cious s e e d and s oil. Som e Eros ion Mats are m ade w ith plas tic ne tting th at is ph otode gradable (bre ak s dow n in th e s unligh t) w h ile oth e rs are m ade from a s tring type ne tting th at is biode gradable (bre ak s dow n in th e s oil).

W h at is Erosion Mat?

Eros ion Mat is m os t ofte n us e d on re ce ntly grade d s lope s s uch as le ach fie lds , ve ge tate d s w ale s and road and drive w ay s ide s lope s . It is to be us e d w ith tops oil and gras s s e e d to e s tablis h a pe rm ane nt ve ge tative cove r as th e m at w ill h old th e ne w s e e d in place w h e n w ind or w ate r w ould te nd to dis rupt grow th by m oving th e s e e d and its s oil. Th e Eros ion Mat w ill als o re tain m ois ture to prom ote good s e e d grow th . Eros ion Mat is a te m porary s tabilization m e th od, but is actually m ore of a pe rm ane nt fixture on your s ite as th e ne tting is e ve ntually brok e n dow n and de grade d as th e gras s grow s up th rough it.

H ow can I incorporate Erosion Mat into m y site de sign?

H ow do I install Erosion Mat?You s h ould be able to purch as e Eros ion Mat from your local cons truction s upply s tore . Once th e s ite h as be e n grade d and s pre ad w ith tops oil, pe re nnial gras s s e e d s h ould be s pre ad e ve nly ove r all dis turbe d are as . Th e Eros ion Mat can th e n be rolle d out on th e s te e p, s loping s e ctions of your s ite or along th e bottom of any cons tructe d s w ale s w h e re e ros ion is lik e ly to occur. Se cure th e Eros ion Mat by us ing 'U' s h ape d s tak e s th at act as s taple s , and can be purch as e d w ith th e Eros ion Mat.

Te m porary Stabilization

Eros ion Mat prote cting a ne w ly s e e de d s lope .

Straw W attle & H ay Bale

Straw W attle s are rolls of h ay us e d for controlling e ros ion and s e dim e ntation caus e d by s torm w ate r runoff. A typical Straw W attle is 8 to 9 inch e s in diam e te r, 25 fe e t long, and w e igh s about 40 pounds . Straw W attle s can be m ade w ith UV de gradable plas tic ne tting for longe vity, or w ith 100% biode gradable burlap for s e ns itive s ite s . W attle s m ade w ith th e plas tic ne tting w ill las t approxim ate ly 3 to 5 ye ars , w ith th e s traw bio-de grading and th e ne tting bre ak ing dow n to s m all pie ce s from s unligh t. H ow e ve r, th e biode gradable W attle s w ill las t le s s th an a ye ar due to th e fairly rapid bre ak -dow n of th e burlap cove ring.(“Straw W attle s – Straw Rolls for Eros ion, Se dim e nt and Storm w ate r Runoff Control”)

W h at are Straw W attle s?

Straw W attle s , or H ay Bale s line d up in a row , can be us e d dow n-s lope along th e outs ide of dis turbe d are as to trap s e dim e nt and re duce th e ve locity of s torm w ate r. Straw w attle s w ork w e ll to trap s e dim e nt th at m ay flow in s torm w ate r runoff into a s tre e t or drive w ay or into a roads ide ditch . H ay Bale s m ay prove be tte r to prote ct catch bas in or culve rt inle ts be caus e th e y are m ore com pact and e as ie r to m anage . Straw W attle s and H ay Bale s are s m all and biode grade able and can be le ft in place afte r cons truction is com ple te to prom ote a s table s ite .

H ow can I incorporate Straw W attle s or H ay Bale s into m y site de sign?

Straw W attle s : Straw W attle s are to be ins talle d h orizontally along a s lope , but w ith a s ligh t dow nw ard angle at th e e nd of th e row in orde r to pre ve nt ponding at th e m id-s e ction. Straw W attle s s h ould alw ays be ins talle d in 3 to 6 inch de e p tre nch e s w ith s e parate s e ctions butte d firm ly toge th e r at th e e nds to e ns ure no le ak age at th e conne ctions . Th e Straw W attle s are to be pinne d s e cure ly to th e ground us ing w ood s tak e s .

H ay Bale s : H ay Bale s are to be ins talle d us ing a s im ilar m e th od to th at of th e Straw W attle s . Bale s are to be s tak e d tigh tly toge th e r in a s h allow tre nch .

H ow do I install Straw W attle s or H ay Bale s?

Straw W attle s us e d for s e dim e nt control on a re s ide ntial cons truction s ite .

Erosion Mat Te m porary Stabilization

Stone Ch e ck Dam

Stone ch e ck dam s are s m all, te m porary dam s ins talle d in s w ale s or ditch e s . Th e y are com pris e d of 3/4" to 1 1/2" s tone w ith a low point in th e m iddle of th e s w ale or ditch . Storm w ate r is allow e d to trick le th rough th e s tone s , but s e dim e nt is trappe d and not allow e d to pas s . During h igh flow s ituations , s uch as a s trong rain s torm , w ate r is allow e d to ove rtop th e Stone Ch e ck Dam .

W h at are Stone Ch e ck Dam s?

Stone Ch e ck Dam s can be us e d to contain s e dim e nt and re duce flow ve locity of s torm w ate r in s w ale s or ditch e s . If s torm w ate r from dis turbe d are as on your s ite is allow e d to flow into an e xis ting road ditch , a Stone Ch e ck Dam s h ould be ins talle d in th e ditch at th e e dge of your prope rty. If you h ave s m all ditch e s ne xt to your drive w ay or anyw h e re on th e prope rty, you could us e Stone Ch e ck Dam s to s low s torm w ate r flow and trap s e dim e nt be fore th e w ate r le ave s your s ite .

H ow can I incorporate Stone Ch e ck Dam s into m y site de sign?

A Stone Ch e ck Dam is e s s e ntially a pile of 3/4" s tone place d pe rpe ndicular to s torm w ate r flow in a ditch or s w ale . Th e s tone s h ould go to th e top of th e ditch on e ach s ide and s h ould h ave a low point in th e m iddle of th e ditch for ove rflow . Th e Stone Ch e ck Dam s h ould be at le as t 1' tall at th e low point. Once th e s ite is com ple te ly s tabiliz e d and undis turbe d, th e Stone Ch e ck Dam s h ould be re m ove d. If th e re m oval caus e s a dis turbance in th e e xis ting gras s cove r in th e ditch , you m ay ne e d to re s e e d th e are a w ith pe re nnial gras s s e e d.

H ow do I install a Stone Ch e ck Dam ?

Tem porary Stabilization

Rain Garde ns can s low th e ve locity of s urface flow s from drive w ays , s ide w alk s and roof runoff.

Rain Garde nRain Garde ns are e s s e ntially infiltration are as th at allow s torm w ate r to s e e p into th e ground. Rain Garde ns colle ct and s low s torm w ate r runoff and incre as e its infiltration into th e s oil th rough th e planting of flow e ring plants and gras s e s (pre fe rably native s pe cie s of both ) th at can s urvive in s oil th at ge ts s oak e d from tim e to tim e .

Th e s e attractive garde ns h e lp re duce th e rapid flow of s torm w ate r from h om e s and yards and th us prote ct s tre am s and lak e s from s e dim e nt and oth e r pollutants th at are w as h e d from h ous e roofs , pave d and grave l are as . (“Tools for Storm w ate r Manage m e nt”)

W h at are Rain Garde ns?

Rain Garde ns s h ould be built in a location dow n th e s lope from your h ous e or drive . A Rain Garde n m ay be us e d to s tore and dis card runoff colle cte d by a Stone Drip Edge or a Ve ge tate d Sw ale or to colle ct s torm w ate r run off from your law n. As s torm w ate r flow s into a Rain Garde n, th e w ate r is abs orbe d by th e s oil and plants . Th e garde n is s ligh tly low e r in th e m iddle th an it is along th e e dge s , w h ich cre ate s a bow l lik e s h ape . Th is s h ape allow s e xtra s torm w ate r to be s tore d above ground until th e s oil and plants can abs orb w ate r. (“Tools for Storm w ate r Manage m e nt”)

H ow can I incorporate Rain Garde ns into m y site de sign?

Pe rm ane nt Stabilization

Th e s iz e of your Rain Garde n is de pe nde nt on h ow m uch are a drains to it from your roof, drive w ay, or law n as w e ll as th e type of s oil on your prope rty. To calculate th is are a, firs t de te rm ine th e approxim ate are a th at w ill e ith e r drain to or be dire cte d to your Rain Garde n.

H ow do I build a Rain Garde n?

Bas e d on th e type of s oil on your prope rty, s e le ct a s iz e factor from th e ch art be low .Sandy Soil 0.03Silty Soil 0.06Clay Soil 0.10

Se cond, m ultiply th e approxim ate drainage are a by th e s oil factor to obtain th e appropriate s iz e for your Rain Garde n. H e re ’s a s am ple calculation:

Approx. Drainage Are a = 25’ x 40’ (roof are a) + 60’ x 40’ (law n are a) = 3,400 s q . ft.Prope rty h as s andy s oil, s o Rain Garde n Are a = 3,400 s f x 0.03 = 102 s q . ft.

Once th e location and s iz e h ave be e n de te rm ine d, you can build your Rain Garde n by digging on th e ups lope s ide of th e garde n location and placing th e s oil on th e dow ns lope s ide to cre ate a be rm . A be rm is a s m all w all com pris e d of s oil th at w ill s urround your Rain Garde n on th re e s ide s to h old th e s torm w ate r in place until it s e e ps into th e ground. Your rain garde n de pth s h ould be at le as t 6 to 8 inch e s de e p of planting s oil. Se le ct native pe re nnial plants th at th rive in w e t s oil and s pace th e m about a foot apart th rough out th e Rain Garde n, th e n m ulch around th e m .

Th e re are th re e bas ic s oil type s : Sandy, Silty and Clay - Sandy s oil is ve ry gritty - Silty s oil is a s m ooth , fine s oil th at cannot be rolle d into a ball - Clay type s oil is th e fine s t type of s oil and can be rolle d into a ball

A Rain Garde n w ith plants and groundcove rs not only tre ats and infiltrate s s torm w ate r, but is be autiful too!

Ve ge tate d Sw ale

A Ve ge tate d Sw ale is a broad drainage ch anne l w ith de ns e ve ge tation th at is de s igne d to tre at runoff be fore dis ch arging it into th e natural drainage s ys te m .(Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook ”, 7-233)

W h at is a Ve ge tate d Sw ale ?

Ve ge tate d s w ale s can be us e d to colle ct s torm w ate r runoff from your drive w ay or law n and s h ould typically outle t into anoth e r pe rm ane nt drainage fe ature s uch as a Rain Garde n or a Le ve l Spre ade r. Ve ge tate d s w ale s can be us e d along th e pe rim e te r of your yard to colle ct s torm w ate r be fore it trave ls into th e w oods or oth e r undis turbe d are a.

H ow can I incorporate a Ve ge tate d Sw ale into m y site de sign?

H ow do I build a Ve ge tate d Sw ale ?A s m all Ve ge tate d Sw ale can be cons tructe d by h and us ing a h oe or a s h ove l. For large r applications , a s m all pie ce of m ach ine ry m ay be re q uire d. Th e s w ale s h ould be built acros s th e natural s lope of th e land, s o th at it w ill inte rce pt s torm w ate r runoff and w ill s low ly m ove th e conce ntrate d flow . Once th e Ve ge tate d Sw ale is dug and grade d, you s h ould s tabiliz e th e dis turbe d are a w ith a 3” – 6” laye r of tops oil and pe re nnial gras s s e e d.

Pe rm ane nt Stabilization

Stone Drip EdgeA Stone Drip Edge is a s m all drain tre nch th at is dug around th e e dge of your h ous e w h e re s torm w ate r flow s from your roof. Th e tre nch h as a fle xible 4" diam e te r pe rforate d pipe ne ar th e bottom and is fille d w ith 3/4" w as h e d s tone . A s tone drip e dge is us e d to colle ct s torm w ate r th at flow s from your roof and carry it to a dis ch arge point. A dis ch arge point is th e place th at th e colle cte d s torm w ate r w ill be re le as e d s uch as a Rain Garde n, a Ve ge tate d Sw ale or a Le ve l Spre ade r.

W h at is a Stone Drip Edge ?

Tak e a look at your roof to de te rm ine w h e re w ate r w ill flow from it during a s torm . If your h ous e w ill be e q uippe d w ith a gutte r s ys te m , a Stone Drip Edge is not ne ce s s ary. Your Stone Drip Edge s h ould be place d along th e e xte rior w alls of your h ous e and garage w h e re s torm w ate r w ill fall. You s h ould plan to dig th e tre nch for th e Stone Drip Edge s o th at it flow s tow ards anoth e r drainage fe ature th at w ill dis pos e of th e colle cte d s torm w ate r. A Stone Drip Edge can flow to a Ve ge tate d Sw ale , Rain Garde n, Le ve l Spre ade r, or a naturally ve ge tate d are a.

H ow can I incorporate a Stone Drip Edge into m y site de sign?

Start by digging a tre nch th at is 12" w ide and 12" - 36" de e p. Mak e s ure th at once th e pipe is ins talle d in th e tre nch th at it w ill flow to your de s igne d dis ch arge point. Th e s e ction of tre nch th at is locate d dire ctly unde r your roof line and w ill colle ct s torm w ate r from th e roof w ill be cons tructe d w ith s tone and pe rforate d pipe . For th is s e ction you s h ould lay a 3" laye r of 3/4" w as h e d s tone in th e bottom of th e tre nch . Th e n place th e fle xible 4" pe rforate d pipe on top of th e th in s tone laye r and cove r th e pipe w ith m ore s tone , filling th e tre nch to th e top. Th e tre nch s e ctions th at w ill be conve ying th e s torm w ate r from th e Stone Drip Edge s e ctions w ill be com pris e d of unpe rforate d pipe and th e s oil you h ave from th e tre nch e s you dug. Attach th e fle xible 4" unpe rforate d pipe to th e pe rforate d pipe , place th e pipe in th e tre nch to th e dis ch arge point and cove r th e pipe w ith s oil. Place pe re nnial gras s s e e d on all dis turbe d are as .

H ow do I install a Stone Drip Edge ?

A Stone Drip Edge is s h ow n h e re agains t th e w all of th e building.

An outle t diffus e r lik e th e one s h ow n h e re could be us e d at th e dis ch arge point of your Stone Drip Edge to s pre ad out th e conce ntrate d flow . Th e diffus e r s h ould be s urrounde d by s tone .

Pe rm ane nt Stabilization

Stone Drip Edge Le ve l Spre ade r

A Le ve l Spre ade r is a pe rm ane nt drainage fe ature th at dis pe rs e s conce ntrate d s torm w ate r to re duce th e flow ve locity and e ncourage infiltration. Storm w ate r is typically colle cte d by a Ve ge tate d Sw ale or a Stone Drip Edge and th e n flow s into th e le ve l s pre ade r. Th e le ve l s pre ade r colle cts th e flow, s pre ads th e s torm w ate r out, and re le as e s it gradually dow n a ve ge tate d s lope .(“Tools for Storm w ate r Manage m e nt”)

W h at is a Le ve l Spre ade r?

A Le ve l Spre ade r functions be s t w h e n cons tructe d on a gradual s lope ne ar th e e dge of undis turbe d w oods or fie ld. Storm w ate r can be colle cte d and dire cte d to a Le ve l Spre ade r as de s cribe d above . Th e Le ve l Spre ade r w ill dis pe rs e th e s torm w ate r into th e undis turbe d are a w h e re it w ill s low ly be abs orbe d by th e ve ge tation and s oil.("Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook ", 7-109 )

H ow can I incorporate a Le ve l Spre ade r into m y site de sign?

A Le ve l Spre ade r s h ould be cons tructe d on a s lope d s e ction of land and th e outle t lip of th e s tructure m us t be com ple te ly le ve l to e ns ure s h e e t flow . Th e Le ve l Spre ade r s h ould be a m inim um of 6 fe e t w ide and 10 fe e t long. Ple as e s e e th e de tail for cons truction s pe cifics .("Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook ", 7-109 )

H ow do I build a Le ve l Spre ade r?

Pe rm ane nt Stabilization

Bio-Re te ntion Are a

A Bio-Re te ntion Are a is s im ply a type of unde rground s torage are a, fille d w ith s tone , th at allow s s urface s torm w ate r and w ate r th at is colle cte d in unde rdrain pipe s from your roof to s e e p into your law n or garde n and th e n infiltrate back into th e groundw ate r. Th e s e Bio-Re te ntion Are as are e as y to ins tall and m aintain and w ork w e ll to control s torm w ate r runoff volum e s by containing s urface w ate r for th e duration of th e s torm .

W h at is a Bio-Re te ntion Are a

Bio-Re te ntion Are as can be cons tructe d in th e m iddle of your law n or be h ind a re taining w all, am ong oth e r locations . Cre ating a Bio-Re te ntion Are a be h ind a re taining w all, as s h ow n in th e im age be low , allow s for roof runoff, caugh t by your Stone Drip Edge , to flow into th e Bio-Re te ntion are a. Th is m e th od als o allow s ove rflow ing w ate r to s e e p righ t th rough th e w all, e lim inating th e ne e d for unde rdrain outle t prote ction s uch as a Le ve l Spre ade r. A Bio-Re te ntion are a cons tructe d in th e yard is s e e n only as a ve ry s h allow de pre s s ion in your law n. Th is de pre s s ion colle cts s urface runoff and allow s s torm w ate r to infiltrate into th e grave l be low , re m oving s e dim e nt and s low ing th e ve locity of s torm w ate r.

H ow can I incorporate a Bio-Re te ntion Are a into m y site de sign?

H ow do I build a Bio-Re te ntion Are a?

Pe rm ane nt Stabilization

Th e s iz e of your Bio-Re te ntion Are a w ill de pe nd on th e am ount of runoff you anticipate flow ing into it. In a ve ry ge ne ral cas e , your s torage are a w ill ne e d to be about h alf th e s q uare footage of th e are a th at w ill be draining into th e Bio-Re te ntion Are a. Exam ple : 1200s q . ft. of roof runoff produce s about 400cf of w ate r for a 25-ye ar s torm in Ne w H am ps h ire , grave l h as a 40% void capacity, incre as ing th e volum e re q uire d for your are a to 1000cf. If th e de pth of grave l s torage is 2 fe e t, th e s q uare footage re q uire d is 500s q . ft.:

400cf * 40% = 1000cf1000cf / 2ft = 500s q .ft. re q uire d are aDig a h ole , bas e d on your calculations , in w h ate ve r dim e ns ions fit your lands cape , about 3 to 4 fe e t de e p, and line it w ith filte r fabric to pre ve nt s oil from clogging th e s tone s torage s pace . Fill th e h ole w ith 2 to 2 1/2 fe e t of 3/4 inch s tone and cove r it w ith m ore filte r fabric. Finis h w ith 1 - 1 1/2 fe e t of tops oil in w h ich to plant gras s or a garde n. If you are building your s torage are a be h ind a re taining w all, ins tall a fe w 2 inch diam e te r outle t pipe s a fe w inch e s be low th e top of th e s tone and be low your unde rdrain inle t pipe , as s h ow n in th e im age above , to allow w ate r to flow out w h e n large rain e ve nts occur.

Unde rdrain Inle t

Th is Bio-Re te ntion Are a is built be h ind a re taining w all w ith Stone Drip Edge unde rdrain flow ing into it. A garde n h as be e n plante d on top s o th e h om e ow ne r doe s n't e ve n k now it's th e re !

Outle t Pipe s re ce s s e d in w all

Garde n or law n plante d at s urface

Mainte nance Sch e duleTh is s e ction e xplains th e ve ry s im ple th ings th at ne e d to be done to m aintain th e Low Im pact De ve lopm e nt BMPs th at you h ave on your s ite . Th is is th e final and pe rh aps th e m os t im portant s te p in controlling and m anaging s torm w ate r.

Maintaining a BMP is not difficult and can be done in only a fe w m inute s ! A q uick ins pe ction of your BMPs w e e k ly or afte r a rain e ve nt can h e lp pre ve nt failure of th e fe ature and/or e ros ion on your s ite . Follow th e guide line s be low to e ns ure th at your BMPs are w ork ing prope rly.

Te m porary BMP's: Silt Fe nce - If built up s e dim e nt is gre ate r th an 1/3 th e h e igh t of th e fe nce , re m ove and dis pos e of prope rly to pre ve nt s e dim e nt from ove rtopping or

pus h ing ove r fe nce . If s torm w ate r h as trave lle d unde rne ath th e fe nce , fill in th eh ole and bury th e fe nce again.

Stone Ch e ck Dam - If large am ounts of s e dim e nt h ave be e n trappe d, s h ove l out asm uch as pos s ible to pre ve nt ove rtopping.

Straw W attle s and H ay Bale Barrie rs - If large am ounts of s e dim e nt h ave gath e re dbe h ind th e fe ature , s h ove l out as m uch as pos s ible to pre ve nt ove rtopping and failure .Re place any w attle or h ay bale if th e y appe ar to be failing or clogge d w ith s e dim e nt.

Eros ion Matting - Ins pe ct th e m atting for s igns of e ros ion unde r th e m at. If w ate r is e roding th e s oil unde r th e Eros ion Mat, s taple th e m atting m ore fre q ue ntly and ifne ce s s ary, re place s oil, com pact and re -s e e d, re placing th e e ros ion m atting andins talling according to m anufacture r's s pe cifications , providing additional s tak ing w h e ree ros ion w as occuring.

Pe rm ane nt BMP's: Ve ge tate d Sw ale - Look for s m all tre nch e s of e rode d s oil calle d rivule ts , and s e dim e nt th at

m ay be track e d dow ns tre am . If e ros ion rivule ts appe ar, re place s oil and m ulch and s e e dth e are a. Us e e ros ion m atting if ne ce s s ary to h old s e e d and s oil in place .

Rain Garde n - Ins pe ct th e garde n pe riodically to m ak e s ure th at th e s oil and m ulch are notbe ing w as h e d out of th e garde n, as th is w ould s h ow th at th e garde n is not prope rlyre taining s urface w ate r. Mak e s ure th e garde n is s till de pre s s e d to catch

s torm w ate r. You m ay ne e d to dig out th e s oil a bit to allow th e w ate r to colle ct. Tom aintain your rain garde n, w e e d and m ulch as you w ould any oth e r garde n.

Le ve l Spre ade r - Ins pe ct th e BMP for e ros ion around or ove r th e le ve l s pre ade r. If e ros ionrivule ts appe ar, re pair and re place s oil, s e e d and m ulch . If w ate r appe ars to be goingaround th e le ve l lip, rath e r th an ove r it, cre ate a be rm th at is h igh e r th an th e lip of th es pre ade r, s e e d and m ulch to s tabiliz e th e dis turbe d s oil.

Bio-Re te ntion Are a - Th is BMP doe s not re q uire m uch m ainte nance at all. Sim ply\ins pe ct afte r large rain e ve nts to m ak e s ure th at noth ing look s out of place . Ifs e dim e nt accum ulate s on th e s urface , re m ove as be s t you can by s h ove l or rak e .If w ate r pools on th e s urface and doe s not infiltrate into th e ground, th e s tonem ay h ave be com e clogge d w ith s oil and m ay ne e d to be re place d.

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Citation Inform ation

“Se dim e nt and Eros ion Control for Ne w H om e ow ne rs .” h ttp://w w w .h e alth .s tate .nd.us . 06 Nove m be r 2007.<h ttp://w w w .h e alth .s tate .nd.us /W Q/Storm /Cons truction/H om e ow ne r_ broch ure .pdf>

“H om e ow ne r’s Guide for Flood, De bris , and Eros ion Control.” h ttp://dpw .lacounty.gov. 06 Nove m be r 2007. <h ttp://dpw .lacounty.gov/w m d/H om e Ow ne rs /e nte r.cfm >

“Ne w H om e ow ne r’s Guide to Soil Eros ion Control.” h ttp://w w w .oak gov.com . 06 Nove m be r 2007. <h ttp://w w w .oak gov.com /drain/as s e ts /docs /Soil% 20Eros ion% 20Re s ide ntal% 20Broch ure % 20nov2003.pdf>

Carr, W e s le y. “An Innovative Approach to Re ducing Eros ion and Se dim e ntation During and Afte r Cons truction.” Eros ion Control. March /April 2002. 06 Nove m be r 2007.<h ttp://w w w .fore s te r.ne t/e cm _ 0203_ innovation.h tm l>

“Tools for Storm w ate r Manage m e nt.” h ttp://w w w .lak e s upe riors tre am s .org. 06 Nove m be r 2007. <h ttp://w w w .lak e s upe riors tre am s .org/s torm w ate r/toolk it/tools .h tm l>

“Sm all Site Eros ion Control Manual.” h ttp://co.je ffe rs on.co.us . 06 Nove m be r 2007.<h ttp://co.je ffe rs on.co.us /je ffco/planning_ uploads /guide s /s m all_ s ite _ e ros ion.pdf>

“H om e ow ne r’s Manual for Back yard Cons e rvation.” h ttp://w w w .s m rw a.org. 06 Nove m be r 2007. <h ttp://w w w .s m rw a.org/pdfdocs /pub_ Back yardCons e rvation.pdf> Storm w ate r Manage m e nt and Eros ion and Se dim e nt Control H andbook for Urban and De ve loping Are as in Ne w H am ps h ire . Bre ntw ood, NH : Rock ingh am County Cons e rvation Dis trict, 19 9 2.

“Straw W attle s – Straw Rolls for Eros ion, Se dim e nt and Storm w ate r Runoff Control.” h ttp://w w w .s traw w attle s .com . 13 Nove m be r 2007.

“Pe nns ylvania Storm w ate r Be s t Manage m e nt Practice s Manual.” h ttp://w w w .de p.s tate .pa.us . De ce m be r 2007<h ttp://w w w .de p.s tate .pa.us /de p/de putate /w ate rm gt/w c/s ubje cts /s torm w ate rm anage m e nt/BMP% 20Manual/BMP% 20Manual.h tm >