erosion&sedimentcontrol

Transcription

1 Auckland Reginal Cuncil i ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin March 1999 Auckland Reginal Cuncil Technical Publicatin N. 90 ISSN

2 Auckland Reginal Cuncil Acknwledgements ii ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin Auckland Reginal Cuncil acknwledges the assistance f many earthwrk cnsultants and cntractrs, specifically Babingtn and Assciates during the develpment and cmpilatin f these guidelines. Special thanks als ges t Shelley Trueman and Clare Feeney fr prviding valuable advice and guidance. Cpyright 1999 Auckland Reginal Cuncil N part f this publicatin may be reprduced, stred in a retrieval system r transmitted in any frm r by any means electrnic, mechanical, phtcpying, recrding r therwise, withut the prir permissin f the publisher. Printed n recycled paper.

3 Auckland Reginal Cuncil Executive Summary iii ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin These Guidelines replace Auckland Reginal Cuncil Technical Publicatin Number 2 and are t be knwn as Technical Publicatin Number 90 Ersin and Sediment Cntrl Guidelines fr Land Disturbing Activities in the Auckland Regin. The intent f these Guidelines is as fllws: T prvide a cmprehensive guideline fr ersin and sediment cntrl. T detail the rules f the Prpsed Reginal Plan: Sediment Cntrl. T minimise adverse envirnmental effects f sediment discharge thrugh apprpriate use and design f specific measures. These Guidelines utline the principles f ersin and sediment cntrl including detailing the Ten Cmmandments f Ersin and Sediment Cntrl in the Auckland Regin. The practices detailed in these Guidelines are divided int ersin cntrl, sediment cntrl, wrks within a watercurse, quarries and vegetatin remval. Fr each practice these Guidelines utline the fllwing: Definitin Purpse Applicatin Design/cnstructin specificatins Cmments Maintenance

4 Auckland Reginal Cuncil Respnse Frm iv ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin We will be regularly reviewing these Guidelines. Please help us keep them accurate and practical - let us knw abut any changes we need t make by using this frm. Please phtcpy this frm befre yu fill it ut, t keep this riginal fr future use. 1. Errrs Are there any errrs in the text r diagrams? If s, please tell us: which page and/r figure number it is n what the errr is and hw yu wuld crrect it 2. Omissins Have we left ut any measures/practices cmmnly used r which yu find useful? If s, please list them belw and if pssible, any design guidelines fr us t include: 3. Effectiveness Are these Guidelines helpful fr cmplying with ersin and sediment cntrl requirements. If nt, please tell us hw we can imprve these Guidelines:

5 Auckland Reginal Cuncil Respnse Frm v ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin 4. Other Cmments D yu have any ther cmments r questins? If s, please nte them belw: 5. Yur cntact details (Optinal) Please nte yur name and phne number belw in case we need t discuss yur suggestins in mre detail: Name: Phne: Thank yu fr taking the time t imprve ur Guidelines. Feel free t phne us abut yur views n (09) (ask fr the Sediment Management Team), r Freepst a cpy f this respnse frm t: The Sediment Management Team, Auckland Reginal Cuncil, Private Bag 92012, Auckland. Freepst N

6 Auckland Reginal Cuncil Table f Cntents vi ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin page Acknwledgements ii Executive Summary iii Respnse Frm iv Table f Cntents List f Plates List f Figures List f Tables v i viii ix x Part A Principles 1.0 Intrductin 1.1 Intent f these Guidelines Hw these Guidelines Wrk Ersin and Sediment Cntrl in the Auckland Regin Current Legislatin: When is a Resurce Cnsent Required? When is Ersin and Sediment Cntrl Required? Auckland s Clays: The Prime Imprtance f Ersin Cntrl Principles f Ersin and Sediment Cntrl 2.1 Types f Ersin Factrs Influencing the Ersin Prcess The Ten Cmmandments f Ersin and Sediment Cntrl 4.0 Types f Land Disturbing Activities Undertaken in the Auckland Regin Part B Practices 1.0 Ersin Cntrl 1.1 Runff Diversin Channel/Bund Cntur Drain Benched Slpe Rck Check Dam Tp Siling 9

7 Auckland Reginal Cuncil Table f Cntents vii ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin page Part B Practices (Cntinued) 1.6 Revegetatin Techniques Temprary and Permanent Seeding Hydrseeding Mulching Turfing Gesynthetic Ersin Cntrl Systems (GECS) Stabilised Cnstructin Entrance Pipe Drp Structure/Flume Level Spreader Surface Rughening Sediment Cntrl 2.1 Sediment Retentin Pnd Silt Fence Super Silt Fence Hay Bale Barrier Strmwater Inlet Prtectin Earth Bund Sump / Sediment Pit Wrks Within a Watercurse 3.1 Temprary Watercurse Crssings Temprary Watercurse Diversin Rck Outlet Prtectin Quarries 5.0 Vegetatin Remval Appendices Appendix A Rules frm Prpsed Reginal Plan: Sediment Cntrl 1 Appendix B Land Use Cnsent: Sediment Cntrl 4 Land Use Cnsent: Wrks Within a Watercurse 11 Appendix C Standard Symbls fr Ersin and Sediment Cntrls 18 Glssary/ Bibligraphy Glssary 1 Bibligraphy 8

8 Auckland Reginal Cuncil List f Plates viii ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin page Part B Practices 1.0 Ersin Cntrl Plate 1.1 Runff Diversin Channel/Bund 1 Plate 1.2 Cntur Drain 3 Plate 1.3 Benched Slpe 5 Plate 1.4 Rck Check Dam 7 Plate Mulching 13 Plate Mulch Crimping 14 Plate Turfing 15 Plate 1.8 Stabilised Cnstructin Entrance 2 0 Plate 1.9 Pipe Drp Structure 2 2 Plate 1.11 Surface Rughening Sediment Cntrl Plate Sediment Retentin Pnd Shwing Decant Systems 1 Plate Sediment Retentin Pnd Shwing Baffle t Lengthen Flwpath and Create Crrect Length: Width Rati 5 Plate 2.2 Silt Fence 12 Plate 2.3 Super Silt Fence 15 Plate 2.4 Hay Bale Barrier 18 Plate 2.5 Strmwater Inlet Prtectin 2 0 Plate 2.6 Earth Bund 2 2 Plate 2.7 Sump / Sediment Pit Wrks Within a Watercurse Plate 3.1 Temprary Watercurse Crssing 1 Plate 3.2 Temprary Watercurse Diversin 3 Plate 3.3 Rck Outlet Prtectin 6

9 Auckland Reginal Cuncil List f Figures ix ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin page Part A Principles Part B Practices Figure 2.1 Types f Ersin Cmmn in the Auckland Regin Ersin Cntrl Figure Cleanwater Runff Diversin Bund 2 Figure Runff Diversin Channel 2 Figure 1.2 Cntur Drain 4 Figure 1.3 Benched Slpe 6 Figure 1.4 Rck Check Dam 8 Figure Getextile Laid n Slpe 18 Figure Getextile at Culvert Outlet 19 Figure 1.8 Stabilised Cnstructin Entrance 21 Figure 1.9 Pipe Drp Structure 2 4 Figure 1.10 Level Spreader 2 6 Figure 1.11 Tracking Sediment Cntrl Figure Sediment Retentin Pnd 2 Figure Sediment Retentin Pnd fr Catchments up t 1.5 ha 8 Figure Sediment Retentin Pnd fr Catchments Between 1.5 and 3 ha 9 Figure Sediment Retentin Pnd fr Catchments Between 3 and 5 ha 10 Figure Sediment Retentin Pnd - Decant Detail 11 Figure 2.2 Silt Fence 14 Figure 2.3 Super Silt Fence 17 Figure 2.4 Hay Bale Barrier 19 Figure 2.5 Strmwater Inlet Prtectin - Filter Media Design 21 Figure 2.6 Earth Bund 2 3 Figure 2.7 Sump / Sediment Pit Wrks Within a Watercurse Figure Temprary Watercurse Diversin Wrks Sequence 4 Figure Temprary Watercurse Diversin Dam Detail 5

10 Auckland Reginal Cuncil List f Tables x ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin page Part B Practices 1.0 Ersin Cntrl Table 1.2 Psitining f Cntur Drains 3 Table 1.3 Benched Slpe Design 5 Table 1.4 Rck Check Dam Design 8 Table 1.6 Grass Seed and Fertiliser Applicatin Rates 11 Table 1.8 Stabilised Cnstructin Entrance Aggregate Specificatins 2 0 Table 1.9 Design Criteria fr Pipe Drp Structure 2 2 Table 1.10 Level Spreader Design Criteria Sediment Cntrl Table 2.2 Silt Fence Design Criteria 13 Table 2.3 Super Silt Fence Design Criteria 16

11 Auckland Reginal Cuncil Intrductin: 1 1 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin 1.1 Intent f These Guidelines These Guidelines have three main bjectives: 1. T prvide users, ranging frm thse directly assciated with varius Land Disturbing Activities (Land Disturbing Activities) t interest grups, with a series f cmprehensive guidelines fr ersin and sediment cntrl fr land disturbing activities by: utlining the principles f ersin and sediment cntrl and the sediment transfer prcess; and prviding a range f ersin and sediment cntrl practices that can be implemented n varius Land Disturbing Activities. 2. T detail the rules in the Auckland Reginal Cuncil s Prpsed Reginal Plan: Sediment Cntrl (September 1995) which define when a Land Use Cnsent is required. 3. T minimise adverse envirnmental effects f Land Disturbing Activities thrugh apprpriate use and design f ersin and sediment cntrl techniques. 1.2 Hw These Guidelines Wrk These Guidelines replace Technical Publicatin N. 2 Ersin and Sediment Cntrl Guidelines fr Earthwrks, updated March They verview the ersin and sediment cntrls that can be used when undertaking varius Land Disturbing Activities and are knwn as Technical Publicatin N. 90 Ersin and Sediment Cntrl Guidelines fr Land Disturbing Activities in the Auckland Regin. These Guidelines fcus n the principles and practices f ersin and sediment cntrl recmmended fr varius Land Disturbing Activities. While nt prviding the full details f the Land Use Cnsent applicatin prcess, they refer t the prcess and it is anticipated that they will frm an integral part f the cnsent prcess. The Guidelines shuld be used during the develpment f an Ersin and Sediment Cntrl Plan fr a prject, and must als be used as part f perating under the cnditins f an apprved cnsent. These Guidelines are split int tw main sectins, Principles and Practices. The Principles sectin utlines ten critical elements that need t be cnsidered when develping an Ersin and Sediment Cntrl Plan fr any Land Disturbing Activity. These ten elements are referred t as the Ten Cmmandments f Ersin and Sediment Cntrl. The Practices sectin cvers n-site practices t be used when implementing the Ten Cmmandments. In mst circumstances, a range f practices will need t be used n any Land Disturbing Activity within the Auckland Regin. Standard symbls fr ersin and sediment cntrls are used in Part B. Auckland Reginal Cuncil staff are available fr further advice and can be cntacted at Auckland Reginal Cuncil, Private Bag , Auckland r by telephning (09) Ersin and Sediment Cntrl in the Auckland Regin Hundreds f hectares f land are stripped f vegetatin r laid bare each year arund Auckland fr the cnstructin f subdivisins, rads, landfills and ther develpments. Withut prtectin measures, the transfrmatin f this land can result in accelerated nsite ersin and greatly increased sedimentatin f waterways, estuaries and harburs. Significant quantities f sediment are discharged frm bare earth surfaces where apprpriate ersin and sediment cntrl measures are nt implemented. Varius studies in Auckland indicate there is a 10 t 100 times increase in sediment yield frm cnstructin sites cmpared with pastral land, while data frm the United States suggests that there may be up t 1000 times the sediment yield frm disturbed sites during cnstructin cmpared with permanent frest cver. In the earthwrks seasn, 1000 ha f bare land was wrked arund the Auckland regin. If left unprtected this culd have resulted in a discharge f up t 66,000 tnnes f sediment/year t aquatic receiving envirnments. The adverse eclgical effects caused by sediment in waterways include: Mdified r destryed instream values. Mdified estuarine and castal habitats. Smthering and abrading f fauna and flra.

12 Auckland Reginal Cuncil Intrductin: 1 2 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin Changes in fd surces and interruptin f life cycles. There is ften a ttal change t instream cmmunities. Recvery times frm the impacts f sediment depsitin are mre likely t be measured in years rather than mnths. In additin t eclgical changes, there may be damage t water pumps and ther structures; the quality f water supplies usually diminishes; lcalised flding can ccur and there is a lss f aesthetic appeal. The Resurce Management Act 1991 (RMA) establishes the Auckland Reginal Cuncil s statutry respnsibilities fr resurce management. The purpse f the RMA is t prmte the sustainable management f natural and physical resurces. Sustainable management is defined in Sectin 5 f the Act as: managing the use, develpment and prtectin f natural and physical resurces in a way r at a rate, which enables peple and cmmunities t prvide fr their scial, ecnmic, and cultural wellbeing and fr their health and safety while: (a) sustaining the ptential f natural and physical resurces (excluding minerals) t meet the reasnably freseeable needs f future generatins; and (b) safeguarding the life supprting capacity f air, water, sil and ecsystems; and (c) aviding, remedying r mitigating any adverse effects f activities n the envirnment. Histrically, earthwrks cntrls were based n vluntary cntrls initiated in the 1970s by the frmer Auckland Reginal Water Bard, which implemented guidelines and a cmplaints respnse rle. The 1980s saw the intrductin f Sectin 34 ntices under the Sil Cnservatin and River Cntrl Amendment Act 1959, requiring cnsents be btained frm the Reginal Water Bard prir t undertaking earthwrks. This remained in effect until 30 September 1993 as part f Auckland Reginal Cuncil s Transitinal Reginal Plan. A Sil Cnservatin Cnsent fr earthwrks was then required under the Auckland Reginal Cuncil s Ersin and Sediment Cntrl Prpsed Reginal Plan. As a result f further submissins and subsequent hearings this has been replaced by the current Prpsed Reginal Plan: Sediment Cntrl (September 1995), develped under the RMA, requiring a Land Use Cnsent: Sediment Cntrl t be btained prir t undertaking a range f Land Disturbing Activities. 1.4 Current Legislatin: When is a Resurce Cnsent Required? The legal basis fr requiring a Land Use Cnsent fr Land Disturbing Activities is the Prpsed Reginal Plan: Sediment Cntrl (September 1995). The Plan s rules apply t Land Disturbing Activities including earthwrks, vegetatin remval, rading, tracking, trenching and quarries. A cpy f these rules can be fund in Appendix A f these Guidelines. Cnsent applicatin frms are prvided in Appendix B. It is imprtant t nte that the rules are valid at the time f publishing these Guidelines but are subject t change. Cntact the Auckland Reginal Cuncil t cnfirm the status f the rules cntained within these Guidelines befre making a decisin based upn them. 1.5 When is Ersin and Sediment Cntrl Required? All prjects invlving Land Disturbing Activities in the Auckland Regin must incrprate ersin and sediment cntrls as an integral part f develpment. Prjects which d nt require a Land use Cnsent under the Prpsed Reginal Plan: Sediment Cntrl, and are classified as permitted activities, MUST still implement apprpriate ersin and sediment cntrls as detailed in these Guidelines. On all prjects, ersin and sediment cntrls shuld be in place befre earthwrks cmmence and shuld be remved nly after the site has been fully stabilised t prtect it frm ersin. The principles and practices within these Guidelines shuld be referred t, and the Ersin and Sediment Cntrl staff at the Auckland Reginal Cuncil cntacted fr further advice if required.

13 Auckland Reginal Cuncil Intrductin: 1 3 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin Wrks Within a Watercurse Any wrks within a watercurse must be carefully planned because cntrlling sediment generatin frm these activities is difficult.. These Guidelines include a number f ersin and sediment cntrl measures that can used fr realignment, piping, culverting and stabilisatin wrks. Shuld nn-cleanfill material be dispsed t a cleanfill site the site may be required t btain authrisatin fr any discharge f cntaminants (ther than sediment) under sectin 15 f the Resurce Management Act 1991, r remve nncleanfill material frm the site, whether r nt this material is part f the existing fill matrix. The tw mst critical factrs in minimising the impact f wrks f this nature are timing and duratin f wrks. Techniques fr minimising sediment generatin and discharge when undertaking wrks within a watercurse are utlined in Part B, Sectin 3 f these Guidelines. It shuld be nted that further cnsents may be required when undertaking such wrks, and cntact shuld be made with Auckland Reginal Cuncil staff t discuss the specific details f the prpsed activity. Cleanfills Cleanfills are anther Land Disturbing Activity that, while nt directly referenced within the Prpsed Reginal Plan: Sediment Cntrl, d generate sediment. These Guidelines d nt include a specific sectin n cleanfill peratins, but standard earthwrks ersin and sediment cntrl practices are apprpriate fr cleanfill peratins. The ARC s definitin f cleanfill (belw) shuld be nted whenever cleanfill peratins are t be undertaken: That cleanfill material is defined as a filling peratin dispsing f sil (ther than cntaminated sil) rck, asphalt, fibrlite, plaster/ clay prducts, and glass, and cncrete with a maximum f 5% by vlume per 10 trucklads f attached structural building materials (wd and structural steel excluding crrugated irn). Cleanfilling peratins are permitted t accept nly thse materials utlined abve. These peratins are nt fr the dispsal f rganic material, vegetatin, cntaminated sils r ther waste materials. Additinally cleanfilling peratins are nt fr the dispsal f unattached structural building materials. 1.6 Auckland s Clays: The Prime Imprtance f Ersin Cntrl The small size f sil particles typical f Auckland s gelgy reduces the effectiveness f ersin and sediment cntrls. The fine clays, nce mbilised, take a much lnger time t settle than the carser sand and silt material. Bigger, better r mre numerus sediment cntrl measures may therefre nt be very effective in limiting ff-site transfer f sediments. Mst effrt shuld be put int preventing sediment generatin in the first instance. That is, int ersin cntrl rather than sediment cntrl. Ersin cntrl techniques include the fllwing: Revegetatin Minimisatin f earthwrks Timing Staging f earthwrks peratins Other measures such as the use f chemical treatment f runff may als be necessary in sme circumstances.

14 Auckland Reginal Cuncil Principles f Ersin and Sediment Cntrl: 2 1 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin 2.1 Types f Ersin Ersin is the prcess whereby the land surface is wrn away by the actin f water, wind, ice r ther gelgical prcesses. The resultant displaced material is knwn as sediment. Sedimentatin is the depsitin f this erded material. Accelerated ersin, caused primarily by human develpment activities, is generally much mre rapid than natural ersin. The basic ersin prcess is detachment, transprt and depsitin (sedimentatin). In Auckland, water is the usual erding agent and transprt medium, thrugh raindrp impact and verland flw energy. Water disldges expsed sil particles and transprts them dwnslpe. Runff and streamflw transprt the erded sil particles t the final receiving envirnment where sedimentatin ccurs. There are seven main types f ersin assciated with land disturbing activities. Splash ersin Sheet ersin Rill ersin Gully ersin Tunnel ersin Channel ersin Mass mvement These are utlined belw. Splash Ersin Sil ersin is a mechanical prcess that requires energy. Much f this energy is supplied by falling rain drps. The impact f a single raindrp n a sil surface r n a thin film f water may break up the sil aggregates and cause individual particles t be thrwn int the air. If this ccurs n a slpe then sme particles will mve up-slpe, but the net effect due t gravity will cause splashed particles t mve dwnslpe. Splash ersin is directly related t the size, distributin, shape, velcity and directin f the raindrp. In Auckland, the ersive ability f splash ersin is enhanced by the typically intense cyclnic strms that can ccur during the earthwrks seasn. Sheet Ersin When rainfall intensity exceeds the infiltratin rate f a sil and the capacity f the available surface detentin, excess water mves dwnslpe, transprting sil particles detached by splash ersin. Sheet ersin r wash ersin is the unifrm remval f sil in thin layers by the frces f raindrps and verland flw. It can be a very significant ersive prcess because it can cver large areas f slping land and may g unnticed fr sme time. Sheet ersin can be recgnised by sil depsitin at the bttm f a slpe, r by the appearance f light clured subsil material n the surface. If left unattended, sheet ersin f tpsils will gradually remve the nutrients and rganic matter imprtant t revegetatin, and will eventually result in lss f sil prductivity n cntributing slpes and elevated sediment cncentratins in receiving waters. Rill Ersin Rill ersin is the remval f sil by runff mving in cncentrated flws. As the flw changes frm sheet flw t deeper flw in these channels, r rills, the velcity and turbulence f the flw increases, and the energy f this flw is able t bth detach and transprt sil particles. Rill ersin has been estimated t be the dminant cntributr t ersin n hill slpes. Gully Ersin Gully ersin is the remval f sil by running water resulting in the frmatin f channels greater than 300 mm deep. Gullies can be distinguished frm rills when nrmal agricultural tillage peratins cannt bliterate them. The fllwing are the prcesses which act in the frmatin f gullies in Auckland. Waterfall ersin at the head f the gully Channel ersin Raindrp splash Diffuse flw frm the side f the gully r frm seepage Slides r mass mvement f sil within the gully.

15 Auckland Reginal Cuncil Principles f Ersin and Sediment Cntrl: 2 2 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin A gully may develp and grw rapidly and their frmatin may generate a cnsiderable amunt f ersin. Therefre, their preventin and remediatin is vital fr ersin cntrl. Tunnel Ersin Tunnel ersin, r piping, is the remval f subsurface sil by subsurface water while the surface sil remains relatively intact. This prduces lng cavities beneath the grund surface, which may enlarge until the sil surface is n lnger supprted, at which pint the surface may cllapse frming a circular hle, smetimes referred t as a tm. Such ersin tunnels may range in size frm a few centimetres t several metres in diameter and typically frm a series alng the surface abve a tunnel. Channel Ersin The ersin f ephemeral r perennial channels results frm direct actin f cncentrated flw when the velcity r vlume f flw in a stream increases. Natural channels adjust ver time t the vlume and velcity f runff that nrmally ccurs in the catchment. Channel ersin ccurs by scuring r undercutting f the stream bank belw the water surface and generally happens during medium t high flws. Channel ersin is a majr cntributr t sedimentatin in the Auckland metrplitan area. High flws in stream channels ccur mre frequently nce a catchment has been urbanised, erding stream banks and enlarging the channel. Fr example, an Auckland study shwed a threefld channel widening after 85% f the catchment had been urbanised (Herald, 1989). Mass Mvement Mass mvement is the ersin f sil r rck by gravityinduced cllapse. It is usually triggered by grundwater pressure after heavy rain, but can als have ther causes, ntably streams undercutting the base f a slpe r earthwrks. Mvement can be either rapid and near instantaneus (landslides, avalanches, debris flws), r slw and intermittent (earthflws and slumps). Earth and sil slip mvement are als ften nted after the remval f vegetatin frm critical slpes assciated with Land Disturbing Activities. These slpes need t be identified befre develpment starts and shuld be avided wherever practicable. Mass mvement can cause majr prblems n earthwrks sites and getechnical investigatins shuld be undertaken where pssible t avid critical slpes r allw fr the preventin f such ersin. Earthslip Ersin Splash Ersin Rtatinal Slump Sheet Ersin Debris Flw Rill and Gully Ersin Channel Ersin Stream Flw Figure 2.1 Types f Ersin Cmmn in the Auckland Regin

16 Auckland Reginal Cuncil Principles f Ersin and Sediment Cntrl: 2 3 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin 2.2 Factrs Influencing the Ersin Prcess The main factrs influencing sil ersin are climate, sil characteristics, tpgraphy, grund cver and evaptranspiratin. Climate Climate affects ersin ptential bth directly and indirectly. The direct relatinship arises frm the actin f rain - a driving frce f ersin - where raindrps disldge sil particles and runff carries them away. The annual pattern f rainfall and temperature change, by and large, determines the extent and grwth rate f vegetatin. This is critical, because vegetatin is currently the mst imprtant frm f ersin cntrl used n Land Disturbing Activities in Auckland. The Auckland Regin receives abut 1200 mm f rainfall annually, with average mnthly rainfalls being greatest thrughut the winter perid. Summer has the greatest rainfall variability, sme summers being very dry, thers wet. Intense cyclnic strms during summer als create many ersin prblems, with a large amunt f rain falling within a shrt time perid. Ersin and sediment cntrl fr all Land Disturbing Activities must be planned accrdingly. Sil Characteristics Fur sil characteristics are imprtant in determining sil erdibility: Sil texture refers t the particle sizes making up a particular sil and their relative prprtins. Sand, silt and clay are the three majr sil particle classes. Auckland sils tend t have a high cntent f fine sands and silts, which are the mre erdible fractins f the sil. The clay cntent als creates difficulty as nce mbilised, it is very difficult t settle ut. This is due t the small nature f individual particles and the tendency fr clay particles t repel each ther, thus keeping them in suspensin. Organic matter imprves sil structure and increases permeability, water hlding capacity and sil fertility. Sil permeability refers t the ability f the sil t allw air and water t mve thrugh the sil. Sils with a higher permeability prduce less runff at a lwer rate than sils with lw permeability. Engineered fills have a very lw permeability, resulting in increased levels f ptentially ersive runff. Sil structure is the degree that sil particles are arranged int aggregates. A granular structure is the mst desirable in bth agricultural and ersin cntrl terms. When the sil surface is cmpacted r crusted, water tends t run ff rather than infiltrate. Ersin ptential increases with increased runff. Tpgraphy Slpe length and slpe angle are critical factrs in ersin ptential because they play a large part in determining the velcity f runff. Lng cntinuus slpes allw runff t build up velcity and t cncentrate flw. This prduces rill and gully ersin. The shape f a slpe als has a majr bearing n ersin ptential. The base f a slpe is mre susceptible t ersin than the tp because runff arriving there is mving faster and is mre cncentrated. Hwever, depsitin may ccur at the base f cncave slpes where slpe angle diminishes. Grund Cver Grund cver includes vegetatin and surface treatment such as mulches and getextiles. Vegetatin is withut questin the mst effective lng term frm f ersin cntrl fr prtecting surfaces that have been disturbed. Vegetatin shields the sil surface frm the impact f falling rain, slws the velcity f runff, hlds sil particles in place and maintains the sil s capacity t absrb water. Evaptranspiratin The Auckland Regin has a fairly frequent rainfall during the winter, but due t high evaptranspiratin and a minimum f rainfall in the summer perid, sil misture levels are ften s lw that irrigatin r watering is needed t achieve the misture levels needed fr plant grwth. Evaptranspiratin rates and the number f days f sil misture deficit vary acrss the regin. Careful cnsideratin needs t be given t evaptranspiratin when attempting t establish a vegetative cver and prevent ersin.

17 Auckland Reginal Cuncil The Ten Cmmandments f Ersin and Sediment Cntrl: 3 1 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin These Ten Cmmandments, summarise the ten principles t fllw when preparing an Ersin and Sediment Cntrl Plan. 1. Minimise Disturbance Fit land develpment t land sensitivity. Sme parts f a site shuld never be wrked and thers need very careful wrking. Watch ut fr and avid areas that are wet (streams, wetlands, springs), have steep r fragile sils r are cnservatin sites r features. Bear in mind the minimum earthwrks strategy (lw impact design) ideally, nly clear areas required fr structures r access. Shw all Limits f Disturbance n the Ersin and Sediment Cntrl Plan (E&SCP). On site, clearly shw Limits f Disturbance using fences, signs and flags. 2. Stage Cnstructin Carrying ut bulk earthwrks ver the whle site maximises the time and area that sil is expsed and prne t ersin. Cnstructin staging, where the site has earthwrks undertaken in small units ver time with prgressive revegetatin, limits ersin. Careful planning is needed. Temprary stckpiles, access and utility service installatin all need t be planned. Cnstructin staging differs frm sequencing. Sequencing sets ut the rder f cnstructin t cntractrs. Detail bth cnstructin staging and sequencing in the E&SCP. 3. Prtect Steep Slpes Existing steep slpes shuld be avided. If clearing is abslutely necessary, runff frm abve the site can be diverted away frm the expsed slpe t minimise ersin. If steep slpes are wrked and need stabilisatin, traditinal vegetative cvers like tpsiling and seeding may nt be enugh special prtectin is ften needed. 4. Prtect Watercurses Existing streams, watercurses and prpsed drainage patterns need t be mapped. Clearing is nt permitted adjacent t a watercurse unless the wrks have been apprved by the Auckland Reginal Cuncil. Where undertaken, wrk that crsses r disturbs the watercurse Map all watercurses and shw Limits f Disturbance and prtectin measures; shw all practices t be used t prtect new drainage channels; and indicate crssings r disturbances and assciated cnstructin methds in the E&SCP. 5. Stabilise Expsed Areas Rapidly The ultimate bjective is t fully stabilise disturbed sils with vegetatin after each stage and at specific milestnes within stages. Methds are site specific and can range frm cnventinal swing thrugh t straw mulching. Mulching is the mst effective instant prtectin. Clearly define time limits fr grass r mulch cvers, utline grass rates and species and define cnditins fr temprary cver in the case f severe ersin r pr germinatin in the E&SCP. 6. Install Perimeter Cntrls Perimeter cntrls abve the site keep clean runff ut f the wrked area a critical factr fr effective ersin cntrl. Perimeter cntrls can als retain r direct sediment laden runff within the site. Cmmn perimeter cntrls are diversin drains, silt fences and earth bunds. Detail the type and extent f perimeter cntrls in the E&SCP alng with design parameters. Highlight steep areas n the E&SCP shwing Limits f Disturbance and any wrks and areas fr special prtectin.

18 Auckland Reginal Cuncil The Ten Cmmandments f Ersin and Sediment Cntrl: 3 2 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin 7. Emply Detentin Devices Even with the best ersin and sediment practices, earthwrks will discharge sediment laden runff during strms. Alng with ersin cntrl measures, sediment retentin structures are needed t capture runff s sediment generated can settle ut. The fine grained nature f Auckland sils means sediment retentin pnds are ften nt highly effective. Ensure the ther cntrl measures used are apprpriate fr the prject and adequately prtect the receiving envirnment. Include sediment retentin structure design specificatins; detailed inspectin and maintenance schedules f structures and cnversin plans fr permanent structures, in the E&SCP. 8. Get Registered A trained and experienced cntractr is an imprtant element f an E&SCP. These peple are respnsible fr installing and maintaining ersin and sediment cntrl practices. On-site staff certified thrugh the Auckland Reginal Cuncil Industry Educatin Prgramme can save prject time and mney, by identifying threatened areas early n and putting int place crrect practices. Cntact Auckland Reginal Cuncil abut registratin. Include arrangements fr a precnstructin meeting, regular inspectin visits (including a pre-wintering meeting), and final inspectin. 9. Make Sure the Plan Evlves An effective E&SCP is mdified as the prject prgresses frm bulk earthwrks t develped individual lts. Factrs such as weather, changes t grade and altered drainage can all mean changes t planned ersin and sediment cntrl practices. Update the E&SCP t suit site adjustments in time fr the pre-cnstructin meeting and initial inspectin f installed ersin and sediment cntrls, and make sure it is regularly referred t and available n site. 10. Assess and Adjust Inspect, Mnitr and Maintain Cntrl Measures Assessment f cntrls is especially imprtant fllwing a strm. A large r intense strm will leave ersin and sediment cntrls in need f repair, reinfrcement r cleaning ut. Repairing withut delay reduces further sil lss and envirnmental damage. Assessment and adjustment is an imprtant ersin and sediment cntrl practice make sure it figures prminently in the E&SCP. Assign respnsibility fr implementing the E&SCP and mnitring cntrl measures as the prject prgresses.

19 Auckland Reginal Cuncil Types f Land Disturbing Activities Undertaken: 4 1 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin The fllwing are the main types f Land Disturbing Activities undertaken in the Auckland Regin and these are discussed in these Guidelines. Trenching Watercurse wrks Cleanfills Small sites and permitted activities Earthwrks Rading Quarries and vegetatin remval The fllwing is a brief summary f key cnsideratins fr minimising adverse envirnmental effects f these activities that are nt fund in the detailed descriptin f ersin and sediment cntrl measures in Part B. Trenching Trenching, usually fr installing utility services, ften happens twards the end f the bulk earthwrks phase f a prject. The fllwing pints need t be cnsidered when trenching. The prject needs t be undertaken in apprpriately sized stages such that the area expsed can be fully stabilised within an acceptable time frame. If trenching impacts n existing ersin and sediment cntrl measures that are part f the verall develpment, thse measures shuld be reinstated as sn as pssible. Cntingency measures shuld be put in place until the riginal measures are reinstated r replaced. All trenching peratrs wrking within a larger site must be familiar with the verall Ersin and Sediment Cntrl Plan fr the site and must cmply with this apprved plan. Independent ersin and sediment cntrl measures detailed in these Guidelines shuld be emplyed fr the trenching peratin. Tpsil and subsils shuld be stckpiled separately adjacent t the trench s that at the cmpletin f the peratin, these sils can be replaced in the apprpriate rder and vegetatin established. When trenching thrugh verland flw paths, give special cnsideratin t the diversin f any flws, which may ccur during trenching, as well as reinstating and stabilising the verland flw path. Wrks Within a Watercurse Wrks within a watercurse shuld be avided wherever pssible, with all alternatives cnsidered befrehand. Where watercurse wrks are unavidable, they will create sedimentatin dwnstream, s the fllwing pints shuld be carefully cnsidered when undertaking these wrks. Have all alternatives been cnsidered? Install a stabilised diversin s that wrks can be undertaken in the dry and reinstate the streamflw nly after these areas have been apprpriately stabilised. If a diversin is nt a viable ptin, then ensure the alternative ptins are fully cnsidered. Carry ut wrks during a dry time f the year when stream flws are lw and the likelihd f a strm is lw. Keep the duratin f wrks shrt. Identify instream values s as t avid critical perids such as fish spawning perids. Cnsider the direct shrt and lng term impacts f culverts r instream structures and install apprpriately designed fish-pass prvisins. Be sure t infrm all dwnstream users, fr example water-users, f ptential dwnstream sediment discharges. Cleanfills Cleanfills dispse f unwanted fill material which may cntain sme ther material as in the definitin f cleanfill prvided in Part A f these Guidelines. Land Disturbing Activities assciated with cleanfills range frm haul rads and access areas t tip faces and dumping areas. Several cntrls are needed fr adequate ersin and sediment cntrl n such sites and the fllwing pints shuld be carefully cnsidered when undertaking such peratins: The cleanfill peratr needs t ensure that material being accepted fr the cleanfill fits within the ARC s definitin. In cases where it desn t, the peratr must reject such lads, which will then need t be transprted t an apprved landfill. Ersin and sediment cntrls shuld be installed

20 Auckland Reginal Cuncil Types f Land Disturbing Activities Undertaken: 4 2 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin in accrdance with these Guidelines and apprpriate maintenance undertaken. As a cleanfill peratin is cnsidered t be a land disturbing activity, each peratin shuld be assessed fr any necessary cnsents within the Prpsed Reginal Plan: Sediment Cntrl. Staging f cleanfill peratins is critical and a prgramme f prgressive stabilisatin f all cleanfill sites shuld be part f each peratin. Small Sites and Permitted Activities After the bulk earthwrk phase f an earthwrks peratin, individual develpers start huse cnstructin. This is the phase f small site develpments which is cnsidered permitted activities under the Prpsed Reginal Plan: Sediment Cntrl. The cumulative impact frm small sites is cnsidered t be cnsiderable and in sme areas may cumulatively discharge as much sediment as the initial develpment itself. Often at this stage f the prpsal, strmwater systems are in place and there are n, r minimal, ersin and sediment cntrls n the site. This results in sediment discharging thrugh an efficient cnveyance system (the strmwater system) directly t the receiving envirnment. The fllwing pints need t be cnsidered when undertaking small site develpment: The develper shuld be fully aware f the permitted activity threshlds within the Prpsed Reginal Plan: Sediment Cntrl and the cnditins it specifies. Ersin and sediment cntrls shuld be installed either n an individual site-by-site basis r a cmbinatin f the sites, in accrdance with these Guidelines r the Small Site Guidelines fr Earthwrks in the Auckland Regin. Strmwater runff frm small sites needs careful planning in terms f the lcatin f rf dwnpipes s that runff acrss bare sites des nt scur sils. Areas f expsed sils shuld be stabilised upn cmpletin f earthwrks, including tpsil and subsil stckpiles, lawn areas and accessways. The site shuld be islated frm the subdivisin s rad system using silt fences t intercept flw frm the site, with a Stabilised Cnstructin Entrance (see Part B, Sectin 1.8) f t prvide site entry and exit. Earthwrks Earthwrks include a wide range f activities frm cleanfilling peratins (defined abve) thrugh t earthwrks assciated with industrial, cmmercial and residential develpments. The Prpsed Reginal Plan: Sediment Cntrl defines the threshlds fr resurce cnsent requirements fr earthwrking activities. Earthwrks have a majr ptential t generate large amunts f sediment, and if nt cntrlled apprpriately, can lead t large sediment discharges. Planning f these develpments is critical t ensure that the activity is undertaken apprpriately, and in a cntrlled manner t avid unnecessary impacts n receiving envirnments. The Ten Cmmandments utline the critical features f an earthwrks peratin. The fllwing are further key pints cntractrs need t be aware f when undertaking earthwrks peratins. It is imprtant t cmply with the specific requirements f the resurce cnsent when undertaking earthwrks peratins. Emphasis shuld be placed n ersin cntrl, rather than sediment cntrl, because preventing sediment generatin is the best means f preventing sediment discharge frm earthwrks sites. Always prduce an Ersin and Sediment Cntrl Plan (E&SCP) fr an earthwrks peratin. Be sure that all parties invlved with the peratin, including subcntractrs, are familiar with and have access t a current cpy f this Plan. Always update the E&SCP with majr variatins n the site and be sure these variatins have the apprpriate apprvals. Keep this up-t-date versin in the site ffice at all times. Plan ahead and undertake cnsultatin with necessary parties as required. Get apprvals and start the peratin early t avid last minute delays and the need t keep wrking int the undesirable wetter mnths. Install apprpriate cntrls in accrdance with the apprved E&SCP and be sure that the design specificatins are apprpriate fr the peratin.

21 Auckland Reginal Cuncil Types f Land Disturbing Activities Undertaken: 4 3 ersin&sedimentcntrl Guidelines fr Land Disturbing Activities in the Auckland Regin Install subsurface drainage as required (t an agreed methdlgy) t divert subsurface cleanwater past cntrl structures and areas f disturbance as apprpriate. Rading Like trenching, the linear nature f rading pses challenges fr ersin and sediment cntrl. Measures need t be carefully planned t ensure cntrls are successful. Often the peratin can be undertaken sequentially, stabilising wrked areas as they are cmpleted. This minimises the ttal sediment generating area f the prpsal and helps prevent unnecessary rad maintenance. The fllwing are sme key pints t cnsider when wrking thrugh a rading prpsal. Prvide enugh rm fr effective ersin and sediment cntrl measures. Often the rad crridr itself can invlve the whle designatin area and n rm remains fr such cntrls. Where space is a cnstraint, make sure that the ersin and sediment cntrls are apprved and will give the necessary prtectin t dwnstream receiving envirnments. Incrprate strmwater design int the E&SCP. This remves the need t revisit the area t install strmwater systems and the unnecessary extra earthwrks that their cnstructin wuld require. Keep the areas f rad crridr expsed at any ne time t a limit that can be practically stabilised with hardfill r by vegetative means, t minimise the expsed area at risk. When crssing watercurses, lk fr alternative rutes and alternative designs and implement the ptin which prvides the best envirnmental alternative. Cntrl all upslpe catchment runff, diverting clean water arund r safely thrugh the area f disturbance. Quarries and Vegetatin Remval Measures in these Guidelines are suitable fr quarry and vegetatin remval peratins. Hwever, the lng term nature f many quarries and the clearfelling f whle catchments during vegetatin remval peratins mean that sme special ersin and sediment cntrl measures need t be implemented. Careful planning f such peratins is thus critical. The key areas where attentin is required are discussed in detail in Part B f these Guidelines and shuld be read in cnjunctin with the ther ersin and sediment cntrls als detailed.