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Technical Journal

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Welcome to the ninth edition of the Atkins Technical Journalwhich features papers covering a wide range of technologies

but with many common themes. A great example of this comesfrom our asset management work where our Highways andTransportation business is leading the way in advising clients on

maintaining availability of highway networks, while the paper onSkynet 5 shows we are doing the same in our Defence, Aerospaceand Communications business for satellites.

Innovation and thought leadership is evident in all the papers; we have transferred

learning from our Aerospace teams to our Bridge teams to produce Fibre ReinforcedPolymer bridge prototypes and we have led the global sustainability debate in diverseareas such as the implementation of electric vehicles, environmentally acceptable

waste disposal techniques and biomass combined heat and power technologies. Weare constantly extending and improving current industry practices across all that wedo, informing the next generation of codes of practice. The papers here present

examples from such diverse areas as the treatment of water run-off from highways tothe fatigue of stranded cables under vibration.

I hope you enjoy the selection of technical papers included in this edition. This ninth

Journal, and all previous editions, are available on our external website. We haveintroduced an email subscription alert service and if you wish to find out more, pleasevisit: www.atkinsglobal.com/en/about-us/our-publications/technical-journals;

Chris HendyNetwork Chair for Bridge EngineeringChair of H&T Technical Leaders Group

Atkins


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Contents

Drainage

135 Adapting assessment of road drainage to the Water Framework Directive 136 Tram drainageEnvironment & Sustainability

137 Winter Haven Chain of Lakes: conservation and restoration targets for sustainable andinnovative watershed planning

138 Landfills vs. incinerators: identification and comparison of the hazards posed by thetoxic emissions associated with the disposal of municipal solid waste in Puerto Rico

139 Powering ahead: how to put electric vehicles on Scotlands roads 140 The feasibility of biomass CHP as an energy and CO

2source for commercial glasshouses

Highway Network Management

141 Performance management framework for managing agent contractors 142 The Area 6 MAC approach to planning & programme management

Structural Dynamics

143 Determination of minimum vessel wall thickness under design condition loadings 144 Innovative optical measurement technique for cable deformation analysis

Structures

145 Optimised design of an FRP bridge using aerospace technology for ultra-lightweight

solutions 146 Reconstruction of drystone retaining walls using composite reinforced soil structures 147 Vehicle-induced vibration of a concrete filled steel tube arch bridge

Systems Engineering

148 A SPAR modelling platform case study: Skynet 5 149 How can CBTC improve the service on a saturated railway system?

Technical Journal 9Papers 135 - 149

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Drainage

135

5

Introduction

The planning and construction ofnew and modified road schemeshave the potential to impact onsurface waters, groundwater andflood risk. In most cases there wouldbe a planning requirement for anassessment to be completed forhighway new build or improvementschemes. For water, this assessmenthas been guided by best practiceand transposed into methodologyin the Design Manual for Roadsand Bridges (DMRB) Europeanlegislation in the form of the WaterFramework Directive (WFD)1, adoptedin 2000, has been incorporated(November, 2009) into the DMRB asa new Standard HD 45/092. This has

changed the method of assessment,requirement for data collection andthe type of data collected to assessthe impact of road development onthe water environment.

Not only is there a requirement forthe Highways Agency not knowinglyto pollute the environment, but nowwith the WFD and associated RiverBasin Management Plans (RBMP)prevention of diffuse pollutionfrom highways may become a keycomponent of reducing impacts fromcatchment-wide activities on ourenvironment.

As long ago as May, 2004, theHighways Agency identified 5 keyissues relating to implementationof the WFD that affect the waterenvironment. These included:

The identification of keypollutants and concentration

levels in highway run-off;

The impact of known solublehighway run-off on the ecology ofreceiving waters;

Adapting assessment ofroad drainage to the WaterFramework Directive

Abstract

Atkins has accumulated a wealth of practical experience of investigating theimpacts to the water environment from highways and road run-off. Since2009 we have been applying the guidance for this area using part of theDesign Manual for Roads and Bridges (HD 45/09) and its associated waterquality model Highways Agency Water Risk Assessment Tool (HAWRAT). Thiswas developed by the Highways Agency (HA) with the Environment Agency(EA) to meet the European Water Framework Directive (WFD) requirementsfor discharges from highways. Using this WFD compliant approach toassessing the impacts of run-off on surface waters, Atkins has gained practicalexperience of refining field data for use in HAWRAT and prioritising possiblemitigation actions (or measures) on a scheme, catchment or even countryscale. However, there are still ambiguities with obtaining and applyingtreatment efficiencies for the potential mitigation measures. These areimportant as the selection of particular solutions (e.g. swales, balancing pondsand wetlands) has a financial impact on the scheme design and an absoluteimpact on water quality.

In this paper the changes in the DMRB approach to treatment of roaddrainage driven by the WFD are considered and the process to reduce theimpacts on the wider water environment is explored.


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The accumulation and dispersal ofsuspended sediments in waters;

The fate of pollutants found inthe unsaturated zone;

The performance efficacy ofdifferent pollution treatmentsystems.

The first three issues have now beenaddressed in part through researchleading to the new Standard andguidance contained in HD 45/09.

There is ongoing research by WaterResearch Council (WRc) into thefourth issue. As yet, it has not beenpossible to address the fifth issue.

Ian Barker, Head of Water at theEnvironment Agency has reportedRivers in England and Wales are attheir healthiest for over a century.But there are still big challenges.Pollution from fields and roads needsto be tackled and the EnvironmentAgency has plans to revitalise 9,500

miles of waterways between nowand 2015.3

This paper focuses solely on refiningAtkins method of assessment ofwater quality and surface water,although HD 45/09 covers the wideraspects of groundwater and floodrisk too. Consideration will be madeof:

The background to the WFD;

The key technical points of the

current assessment measure (HD45/09);

Issues relating to assessment ofmitigation.

Where appropriate, examplesare used giving experience of theapplication of the new guidance.This includes work that Atkins hasundertaken on the M25 DesignBuild Finance and Operate (DBFO)widening scheme, A21 planningapplications and Priority Outfallstudies in the East of England andacross Wales.

The background of theWFD

The WFD is European legislationthat was enacted to deliver a betterwater environment and a consistentapproach to water managementacross European Community memberstates. It requires planning on a longterm basis, outlining a process tobe implemented over three 6 yearplanning cycles up to 2027. As suchits national adoption is undertakenover a period of tens of years, longenough to plan large-scale changes.It is a single, but large and complexpiece of legislation from whichthe following key points can beextracted, relevant to implementationin the UK, with particular regard tohighways assessment.

1. There is a requirement toprevent any deterioration of

water quality;2. There is a requirement to meet

good ecological status;

3. There is a requirement forcatchment scale management.

These three points will be dealt withbelow.

No deterioration

Taking the recent M25 DBFOcontract4 as an example, it

is common to find there is arequirement, in contract, for noworsening of effect with regard tothe water environment. In real terms,at the time of planning there was ageneral trend for increasing trafficin the National Traffic Forecasts andconsequently the likelihood of higherpollution loading in the future. Ifthis holds true for future trafficforecasting and if contracts requireno worsening of effects, it couldbe argued that nearly every new

road scheme and most improvementschemes will be required to includemitigation, as without it therewould be deterioration in the qualityof road run-off (or worsening ofeffect). Implicitly this also suggests a

requirement for assessing the existingbaseline condition for comparison.If the existing condition is notaccurately assessed there could bean issue with over-compensation orunder-compensation with mitigation.Under-compensation couldhave a detrimental effect on theenvironment and over-compensationcould be questioned in terms of valuefor money.

Meeting good ecological

statusPrior to implementation of the WFD,the EA used River Ecosystem targetsand assessed compliance based onbiological and chemical monitoringresults. Through the WFD there hasbeen a requirement to consider moreparameters, particularly for biology,which contribute to an ecologicaland a chemical classification for eachbody of water. The EA currently hasmaps available on its website that

show the existing and proposed(2015) ecological objective of mainwatercourses in the UK. For mostrivers there will be a requirement tomeet good ecological status by2015.5

The immediate impact of arequirement to meet an objectiveof good ecological status on theassessment method provided in HD45/09, is that this objective should beused for the majority of watercourses

which within HD 45/09 wouldnow be assessed to have a highimportance.

Determining the importance ofa water feature is part of a threestep method used to determinethe significance of effects ofa road scheme on the waterenvironment. The other two stepsinclude determining the magnitudeof impact of a scheme and thenfinally combining steps 1 and 2 to

provide a significance of effect. Ahigher importance is likely to resultin greater significance of effects,most often adverse for a newdevelopment. Taking this a stepfurther, given that most watercourses


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135 Adapting assessment of road drainage to the WaterFramework Directive

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Drainage

will now have a high importance(previously many watercoursesmay have been medium or low), arelatively lower magnitude of impact(due to road design) will now lead toadverse significance of effects. If thedesigner were to submit the sameroad scheme plan post HD 45/09(that had been submitted before)it is likely there will be a greaterrequirement for mitigation overalland fewer watercourses that requireno mitigation.

Catchment Scale

The DMRB through HD 45/09continues the processes developedin its predecessor, HA 216/06, inapplying the WFD to assessmentof road drainage. These processescan be applied in a strategic way byinvestigating drainage from entireroad networks, thus considering thecatchment scale effects of road run-off.

During the time that the DMRBguidance was drafted, the WFDrequired the production of RiverBasin Management Plans (RBMP)to consider, among other things,catchment effects of development.Each of the 10 regions of Englandpublished RBMPs in December 2009.6As an annex to these plans thereis an Annex C entitled actions todeliver objectives. For most regions,within these actions or programme

of measures there is a requirementto improve discharge from highways.In a few areas it is likely thatparticular action will be taken onexisting road networks to improvepoor discharge quality. As there is adeadline of 2015 for watercoursesto meet good ecological status theHA and Welsh Government (WG)have been undertaking outfallprioritisation studies to considerwhich outfalls on the highway

network are the worst performingand which outfalls could be improvedto help meet these standards.

Atkins has had key involvement,leading the priority outfall assessmentscheme across Wales and within

HA Area 6 in the East of England.A typical method of approachingcatchment assessment is to usereadily available road geometry datacollected by local highways teams todetermine high and low catchmentpoints. Once these catchments aredetermined a high level assessmentcan be undertaken using theprinciples of HD 45/09 to determineif a catchment is likely to fail to meetcurrent water quality standards.

All catchments that pass can bescoped out. All catchments with thepotential to fail can then be furtherassessed using the HAWRAT toolto provide a prioritisation of mostpolluting outfalls in a catchment orregion. This information is shown asa layer within the Welsh AssemblyDrainage Data Management System(WADDMS) and the HighwaysAgency Drainage Data ManagementSystem (HADDMS) databases

available over the internet forhighways users to interrogate.

It is likely that this informationwill be used at a high level for theHighways Agency to agree with theEnvironment Agency on what is the

real impact of highway run-off ona local and catchment scale whichwill direct further mitigation.

Key developments ofHD 45/09

Key technical developments in thenew HD 45/09 assessment include:

A Memorandum ofUnderstanding (MoU) developedwith the EA;

The method becoming a Standard(requiring Departures fromStandard in some instances wheremandatory requirements cannotreasonably be met);

Development of the HighwaysAgency Water Risk AssessmentTool (HAWRAT).

One of the key benefits of HD45/09 is that great effort hasbeen made to undertake relevantresearch applicable to an assessmentmethodology alongside the EA whowere involved from the beginning.This process has culminated in arefreshed MoU between the HA

Figure 1. Review of completed road scheme outfall mitigation on Thorney Bypass A47.This would now be required to meet Good WFD standards. The reed lined ditchseen in the background (behind access track) is one example of a treatment type notcovered in HD 45/09


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and the EA.7

The MoU not onlycovers technical water information,but information exchange. Indeed,although there may be greaterrequirement for scrutiny on highwayschemes, in the long term, as theprocess for information exchangedisseminates around the EA andpractice comes into line as agreed,the MoU should aid consultants inmore efficient assessment (with lesscost in terms of data requests) ofenvironmental impact.

A key component of Atkins work onimprovements to the A21 wideningschemes has been consultation withthe Environment Agency and NaturalEngland. Most recently this has led toextended investigations of the impactof the scheme on groundwater viamonitoring highlighted in initialscoping studies. This additionalmonitoring is providing a solutionto the scheme that will not restrictthe groundwater supply to agroundwater dependant SSSI.

As HD 45/09 has been producedas a Standard (rather than anassessment or advice) there arenow sections of the document thathave to be met or would require aDeparture obtained through the HA,if the defined mandatory contents ofthe standard are not adhered to. Thekey standards include:

No new discharge will be allowed

to any area in Source ProtectionZone 1 (SPZ1) without provingthere would be no effect togroundwater and source ofabstraction (for example thereare numerous discharges to SPZ1around the M25 and wherepossible these were removedduring the recent wideningscheme);

Spillage risk from existing outfallsmust not be increased.

The development of HAWRAT is akey feature of HD 45/09. Prior to itsdevelopment the methods that hadbeen used to assess chronic pollutionfrom road discharge included simple

dilution calculations and the massbalance contribution of heavy metalsfrom routine road run-off. This wasassessed against an EnvironmentalQuality Standard (EQS) based uponlimits of concentration found inthe Freshwater Fish Directive8 fordissolved copper and total zinc(the two metals most commonlyassociated with road drainagepollution). Any breach of thestandards is deemed a failure.

The new assessment for chronicpollution in the DMRB uses AnnualAverage Concentrations (AACT)taken from the WFD, again forcopper and zinc. HAWRAT estimatesthe annual concentrations of run-off from the road surface based onexpected rainfall events and uses thisto estimate the impact on averageconcentrations in the watercourse.Although the levels of zinc anddissolved copper are more stringentin the new guidance, which maylead to a requirement for moremitigation, the use of annual averageconcentrations is less onerous forroad outfalls. As road discharges arenot continuous discharges any shortterm impact can be offset duringdrier periods at most locations withregard to AACT. In addition to theuse of AACT to determine chronic(or long term) pollution a newmeasure was developed to consideracute (short term) pollution. This

measure better reflects the natureof road pollution often being inflashy loads, which are thoughtmore generally to build up and bewashed off in a first flush effect.Consideration was made as to howthis short term pollution from roadsmight affect organisms throughempirical studies.9

Thresholds developed to considershort term pollution are knownas Run-off Specific Thresholds

(RSTs). The RSTs are based in partupon consideration of ProbableEffect Levels (PEL) on ecology fromsediment bound pollution. AlthoughRSTs consider other pollutants suchas cadmium, total PAH, pyrene and

fluoranthene, again copper and zincare taken as representative of thegroup of deposited pollutants and inthe majority of cases will be used asthe critical contaminant requiringmitigation. In some instances RSTswill be exceeded where AACT are notand in this case the HA still expectsprovision of mitigation.

Historically mitigation has includeda wide range of measures includingbypass separators, catch pits,

soakaways, planted ditches andponds. These mitigation measures,which are considered in HA103/06,could be considered to provide apollutant removal treatment efficacy.The efficacy of mitigation measuresfor routine run-off pollution isapplied to HAWRAT by means ofa percentage flow or pollutantreduction factor. The application ofmitigation with reference to spillagerisk has to be applied via a spillagereduction factor related to Table 8.1of HD 45/09, built into a separateworksheet within HAWRAT. Thisremoval efficacy is also dependant onthe proportion of catchment run-off the mitigation is treating. Thereare a number of measures that arenot considered (in terms of efficacy)within HA103/06. Within the recentM25 widening improvements Atkinsliaised with the Highways Agencyand Environment Agency to agree atreatment efficacy for a Downstream

Defender vortex separator forimproving removal rates of total zincand sediment.

The final component of HAWRATincludes a consideration for theecological effects of sediment inthe water environment. As earlyas 1998 the importance of theenvironmental effects of sedimentwere documented within guidance,10however until the new Standard, nodefinitive test had been produced

for highway assessment. Within theWFD there is an increased onus onnot only assessment of sediment andits effects on ecology, but also onits effects on morphology of bodiesof water. Within the DMRB a model


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Drainage

has been developed consideringsediment input from a highwaycatchment area and the receivingsurface water. However, this onlyconsiders the effect of sediment onecology by estimating sediment buildup, not the effect on morphology.The consideration of sediment withinHAWRAT is important enough thatfailure of this test alone would leadto minor adverse magnitudes ofimpact on the water environment.The model considers the extent ofsediment deposition and whetherthe watercourse into which thereis discharge could be consideredaccumulating (a model specificterm referring to the propensity ofsediment to gather at an outfall dueto, for example, low flows or gentlegradients).

There is little refined informationabout sediment loading and soat present the extent of sedimentaccumulation is estimated andcontrolled by an arbitrary level setby the HA. Through practice this islikely to be refined. With regard tothe sediment test, the current defaultparameters (post HD 45/09) for thetest are conservative and include:

A 1m wide watercourse;

A 1 in 1000 long slopewatercourse gradient;

A Roughness coefficient -Mannings n of 0.07 (veryweedy, heavy timber).

Initial evidence is that manydischarges fail the sediment testsand, if so, HD 45/09 directs the userto undertake a field survey to obtaindata that can be substituted for thedefault settings. Initial indications,from Atkins fieldwork on theA21 project and in Wales are thatreceiving watercourses generally havebetter sediment accumulating

conditions than proposed byHAWRAT, as the default settings arevery conservative. As an examplerecent measurements undertakenin a watercourse in Wales, seeFigure 2, returned a gradient

of 1 in 17, significantly reducingsediment loading predictions. Onepossible solution to assessment ofwatercourse gradient could be toconsider the use of topographicalsurvey data and site photographsto estimate gradient. On a numberof sites investigated by Atkins,interpolation of topographical datahas compared favourably with fieldinvestigations.

Within HAWRAT there is alsoa consideration to account forsensitivity of designated sites (i.e.

such as Sites of Special ScientificInterest, Special Protection Areaor Special Area of Conservation).The threshold levels for failingRSTs are halved (internally withinthe model) if there is a designatedsite within close proximity, makingthe test more onerous. Of course,relevant information provided toexperienced practitioners for theenvironmental assessment couldshow that there would either be no

effect or no connectivity with such adesignated site, potentially reducingthe requirement for mitigation.Conversely, in the example ofdischarge from the A21 proposedhighway widening project, where

Figure 2. Measurement of river bedprofile near Port Talbot, Wales leadingto refinement of gradient effectingsediment deposition in HAWRAT

the highway widening may physicallyrestrict groundwater supply to anearby designated conservation site,highlights that there are still potentialimpacts on the water environmentnot directly covered by HAWRATand other associated tests within HD45/09.

As with its predecessor guidance, HD45/09 considers the impact of routinerun-off from outfalls not necessarilyjust as an individual outfall but within

a watercourse reach which respectsthe whole catchment managementdriver of the WFD. It also guides theuser to consider cumulative sedimentimpacts. The rules for aggregatingdischarges differ slightly betweenroutine run-off and sediment. Forboth assessments considerationneeds to be made for each outfallindividually as well as their combinedeffect. A combined assessmentshould occur for discharges withina 1km section of a watercourse forsoluble run-off and within 100mfor sediment. Preference is givento consideration of higher quality,more ecologically diverse (and usuallylarger) watercourses downstreamrather than the immediate receptorof highway drainage which in manycases is often a small roadside oragricultural ditch.

To reduce the need to repeatenvironmental baseline assessments

the HA is beginning to recordprevious assessments for stretchesof road subject to new developmentschemes on the Highways AgencyDrainage Data Management System(HADDMS).11It is now a requirementof all schemes to submit electronicversions of tests undertaken for thewater environment assessment to theHA.


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existing HA treatment datasets15documented in the DMRB assummarised in Table 1.

However, among practitioners theuse of the data provided by the EAand HA studies is regarded as nottruly representative of actual efficacyrates. For example, considerationof 7% removal efficacy for filterdrains as shown in Table 3.2 of HA103/06, compared against 80-90%removal efficacy for filter drains as

noted in CIRIA c60916shows thewidespread difference and thatthere is clear evidence that reportingof treatment efficiencies could berefined. Unfortunately neither HD45/09 nor the Sustainable DrainageSystem Manual17published in 2007improved or updated understandingof treatment efficiencies.

The draft National Standards forSUDS were released in December201118and are applicable to local

authority roads, although not directlyapplicable to highways. Thesestandards do not provide improvedtreatment efficacy estimates.However, there is a requirement forthe number of treatment methods

Road Site/Treatment Devies

%Reduction: Inlet to Outlet

Intialform oftreatment

Secondform oftreatment

Totalsystemtreatment

A34Bypass oil separator/surface flow wetland/wetbalancing pond

Metals 15 11 24

PAHs -1 99 99

TSS 37 73 83

A34 Filter Drain

Metals 7 7

PAHs 52 52

TSS 38 38

M4

Oil trap manhole/

sedimentation tank

Metals -7 41 30

PAHs -30 -26TSS -19 43 33

M40Full retention oil separator/wet balancing pond

Metals 19 35 48

PAHs 13 50 57

TSS -9 62 58

A417Bypass oil separator/drybalancing pond

Metals 27 39 56

PAHs 4 16 22

TSS 56 -37 40

Planning formitigation to meet therequirements of theWFD

The final key point of discussionregarding meeting the moreambitious standards of the WFDwithin the highway assessmentmethod is consideration ofmitigation.

There has been advancement in theguidance of the DMRB with respectto identifying various treatmentefficacies (i.e. percentage removal)for soluble pollutants for differenttreatment methods in routine run-offbetween 2000-2012. These haveincluded empirical studies undertakenby the HA and EA, published in2003.12 13 Further research was thenundertaken between 2002 and 2009(with the HA and EA partneringwith WRc) that considered typicalpollutant loading within road run-offalongside toxicity of substances toecology. This research has led towardthe consideration of a treatmenttrain approach to mitigation ofhighway run-off, which involves morethan one type of treatment in seriesto provide better mitigation. Thistype of approach is described furtherin the SUDS Manual.14

As part of the process of winningthe tender for the M25 wideningin 2006 a treatment train wasproposed linking greater treatmentwith greater areas of pollution andmore sensitive water receptors.This included a combination ofbypass interceptors, downstreamdefenders and treatment pondsto protect the most sensitive waterreceptors.

The application of suggested

pollutant removal efficacy rates forparticular mitigation methods frommore recent best practice manualssuch as CIRIA c609 were investigatedbut were found to be very variablederived from very small datasets. Thisled to the dependence on already

to be applied to each road. Roadswill be required to include twoor (if discharging to a sensitivewatercourse) even three levels oftreatment as normal. Discharge toground will be a preference. Onething is clear; the use of SUDS orvegetative treatment systems is likelyto become more prominent withindevelopment schemes associatedwith the progression of the Flood andWater Management Act (FWMA).18

Without clear guidance on theefficacy of vegetative treatmentsystems one way of improvingaccuracy of assessment of thepotential of treatment measures isthrough a written departure to theHA. Bespoke mitigation such as strawbales provided in agricultural areas(and shown in Figure 3) will providelevels of mitigation not addressed inHD 45/09. So far the approach of theHighways Agency via the DMRB has

been to consider mitigation throughvegetative treatment systems tosome extent, but there is also thepotential for proprietary systemsto replicate natural drainage andprovide treatment.

Table 1. Source Table 3.2 HA 103/06 that summarises water treatment information tobe used in assessment of highway impact on the water environment


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use of telemetry was incorporatedinto the M25 design providingremote alarms for oil in bypassseparators and CCTV to monitoroutfalls. This ensures maintenancewhen required and a quick responseto serious spillage risk. There is alsoguidance given within the DMRB thatstipulates that mitigation be appliedshould serious spillage risk endangera protected site or protectedspecies. Here, consultation with theappropriate people in environmentalprotection agencies is important.

Through experience of workingwith a planning authority on A40improvements in Wales the proximityof particularly sensitive water, theCleddau River, (the type that isrecognised by the ethos of the WFD)with evidence of otter holts, wasenough to convince the authoritiesto provide spillage risk mitigationeven though the risk of occurrencewas very small and well outside theimmediate requirements of the HD45/09. Given the clear direction ofthe WFD to protect ecology in waterand using expert advice, our designsshould practically consider the typesof ecology we are trying to protectand whether mitigation measuresin addition to those required bythe DMRB could best satisfy clientrequirements.

HD 45/09, as influenced by the WFD,

requires more emphasis on mitigationand there may be more cases wheremore than one stage of treatmentwill be required. Previously, under HA216/0620the designer could use areferenced method in HA 103/06 todetermine a required area of plantingin a balancing/hybrid pond that wasdesigned to completely treat (givenenough planting area) any pollutingsituation.

Until HA 103/06 is updated and

the HA provide further guidanceon treatment efficiencies, there willbe a need for designers to workalongside manufacturers and applybest practice guidance to show thebenefits and efficiencies of treatmentmeasures to meet WFD standards.

supplier tests are required to ensureAtkins provides the best solutionto our clients. This will ensure themost appropriate treatment typeon Atkins future commissions for arange of different types of treatment.In turn this will help Atkins improveits design beyond the guidancecurrently existing in the DMRB.

As part of the HD 45/09 assessmentprocess there is also consideration ofreduction of serious spillage risk. See

Table 2.

SystemOptimum riskReduction FactorR

F(%)

Passive systems

Filter Drain 0.6 (40%)

Grassed Ditch/Swale 0.6 (40%)

Pond 0.5 (50%)

wetland 0.5 (50%)

Infiltration basin 0.6 (40%)

Sediment Trap 0.6 (40%)

Vegetated Ditch 0.7 (30%)

Active Systems

Penstock/valve 0.4 (60%)

Notched Weir 0.6 (40%)

Other Systems

Oil Separator 0.5 (50%)

Within the M25 widening schemea departure was submittedand approved by the HA touse a Downstream Defenderhydrodynamic19separator, operatingto remove sediment loading andsediment bound pollutants aspart of the treatment system.Understanding of the processesoperating for this treatmentmechanism, combined withlaboratory testing presented bythe manufacturer (which had beenundertaken prior to the projectstarting), allowed the drainageand environment teams to adopta suggested 15% removal efficacyrate for sediment bound metals. Ourjudgement was required to consideroperational flow rates that wereoutside of the test data providedby the supplier. Our understandingof the processes operating withinthis particular system led us topropose that no removal of dissolved

metals could be expected from thismitigation method which betterreflected the true benefits of themitigation on the type of pollutantsrequiring assessment.

Table 2. Spillage risk reduction factorstaken from HD 45/09 Table 8.1

An understanding of the keypollutants that may impact the waterenvironment combined with thephysical treatment processes involvedand greater information from

Figure 3. Use of a straw bale (in rearof channel) to filter water quality. Noguidance on treatment efficacy existsfor similar methods of water quality

treatment

The method in HD 45/09 to assessspillage risk uses measures from

the road design and data on trafficdensity and make up to determinethe likelihood of a serious spillageevent happening. This is measured inthe number of years, or return periodof an event. Again professionaljudgement needs to be applied todetermine the value and effect ofmitigation. Using the methodologyin HD 45/09, a reduction in spillagerisk of 70% could be achieved byproposing the design of a vegetated

ditch. However, the performance ofthis system for some pollutants suchas milk could be questioned. There isalso scope for using methods outsidethe guidance of HD 45/09 to improvemitigation of serious spillage risk. The


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Where vegetative treatment systemsare considered in scheme design,in addition to guidance within theDMRB (HA103/06), there will alsobe a need to obtain and applycross sector research informationon mitigation efficacy rates andbest practice for operation. Therequirement for this informationwill be likely to increase with thegreater requirements for use ofSUDS following the FWMA, beingapplicable to both local authoritiesand the Highways Agency.

In addition to the planning formitigation a method to respond topollution incidents and to maintainpollution treatment features shouldbe a standard provision with Atkinsdesigned road schemes. At presentthere is no requirement within HD45/09 to provide either a methodfor maintenance or a method forresponse to a pollution incident.However, within the design ofthe M25 drainage scheme theincorporation of alarms (withinbypass separators), CCTV and acentral management system formaintenance all added value toproviding a quick response topollution incidents should they occur.

An important consideration foreffective application of treatmentsystems includes provision ofadequate maintenance plans and

consideration of maintenance withinthe design and consultation process.Historically drainage systems havesuffered a lack of maintenancein some regions and resources toimprove maintenance will continueto be stretched in the near future.Continued negotiation with theEnvironment Agency, InternalDrainage Boards, local authoritiesand other interested parties willensure access to mitigation featureswill not hinder the effectiveness of

treatment measures.

Summary

The application of the WFDthrough relevant guidance hasrequired highway engineers andenvironmental teams to considercatchment wide, ecological effects ofhighway run-off including sedimentdischarge and compliance with abroader range of new water qualitystandards that reflect the currentlegal framework.

Although the current DMRB goes along way to address the requirementsof the WFD, there are still areasthat can be improved in futureiterations. A better understandingof the influence of sediments andthe need to study the physicalchanges to watercourses along witheffectiveness of mitigation are allareas that will need to be addressedin the near future.

In considering how to meet thestandards, Atkins will be lookingfor opportunities to provide bettertreatment solutions for highwaysdischarges which will allow newdevelopment to enhance our waterenvironment rather than impactupon it. At present the existingdriver for improvement of thewater environment has been ledby the Highways Agency, highwaysauthorities, HD 45/09 and the PriorityOutfall Assessment programme.

However, where urban run-offfrom roads may be shown to becontributing to failure of WFD samplepoints, there may be a driver throughRiver Basin Management Plans forfurther improvement of dischargefrom our road network.


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References

1. Water Framework Directive 2000/60/EC.

2. HD 45/09 Road Drainage and the Water Environment DMRB, Volume 11 Section 3 Part 10.

3. BBC 31/12/2010 http://www.bbc.co.uk/news/uk-england-12098028.

4. Schedule 23 2.1 (3) b M25 contract.

5. Environment Agency WFD River Classification maps http://maps.environment-agency.gov.uk/wiyby/wiybyController?topic=wfd_rivers&layerGroups=default&lang=_e&ep=map&scale=3&x=456769.4583333337&y=302349.6249999998#x=527956&y=386044&lg=1,7,8,9,5,6,&scale=1.

6. Final RBMP http://www.environment-agency.gov.uk/research/planning/33106.aspx.

7. Memorandum of Understanding between the Environment Agency and the Highways Agencyhttp://www.ha-partnernet.org.uk/portal/server.pt/community/memorandum_of_understanding/717.

8. The EC Freshwater Fish Directive (2006/44/EC).

9. Johnson, I and Crabtree RW, 2007, Effects of soluble pollutants on the Ecology of receiving waters, WRc Plc,Report No. UC 7486/1, UK Highways Agency.

10. DMRB Vol 11 Section 3 Part 10 3.14-3.16.

11. HADDMS http://www.haddms.co.uk/.

12. HA 103/06 Table 3.2 DMRB Volume 4 Section 2 Part1.

13. The Long term monitoring of pollution from Highway Run off: Final Report R&D technical report, P2-038/TR1 Moy,F, Crabtree RW and Simms, T.

14. The SUDS manual c697, CIRIA, 2007, London.

15. Sustainable Drainage Systems. Hydraulic, Structural and water quality advice, C609, London, 2004 CIRIA

16. The Flood and Water Management Act (c29) April 2010.

17. The SUDS manual c697, CIRIA, 2007, London.

18. The Flood and Water Management Act (c29) April 2010.

19. Downstream Defender http://mx1.hydro-intl.com/stormwater/downstream.php.

20. HA216/06 Road drainage and the water environment, 2006, DMRB superseded November 2009.


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Drainage

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15

Introduction

Atkins was appointed to work on thedrainage designs for improvementsto the Manchester Metrolink Phase1 & 2 works and has been part ofthe Engineering Support ServicesTeam for the GMPTE (now Transportfor Greater Manchester referredto as TfGM from here on). Thiscommission was let to draw upon thedrainage experience of the author,who had also worked on NottinghamExpress Transit (NET Line 1) and wasthe principal drainage designer forthe latest upgrade to the Blackpool& Fleetwood Tramway. Thesesecond generation tram systemshad the same drainage problems

to solve as their forerunners hadovercome. Some of the tracks willbe on former railway lines, so similardrainage techniques to Network Railstandards for ballasted track can beused and are not discussed furtherin this paper. Interesting drainagetechniques to relearn relate to theurban realm, when groove rails areusually to be found, either on asegregated section of highway or inpedestrian areas, sometimes referred

to as a trambahn, or on carriagewaysfully integrated with vehicular traffic,with the tram given priority at trafficlights and junctions. There are nonew drainage techniques to belearned; only reapplication of thoseknown to earlier drainage engineers.

Tram drainageAbstract

Trams have been in use in the UK for more than a century, 2010 being the125th anniversary of Blackpools famous electric trams - one of the very firstin the world and the first in the UK. Many other cities followed Blackpoolsexample, but from the middle of the 20th century, most of these were closeddown and the tracks ripped up for scrap or buried under tarmac. However, inApril 1992, Greater Manchesters Metrolink opened to passengers. The Buryand Altrincham lines were the first to open, followed by the Eccles line in July

2000. Many other cities in the UK now have, or are planning, tram systems,including Nottingham, Edinburgh, plus Dublin LUAS in the Republic of Ireland.This paper sets down the drainage requirements for this second generationof UK trams, based on the authors experiences on a number of these tramsystems.

Figure 1shows an extract from anEdgar Allen catalogue c.1920, whichclearly shows the two main elementsof point drains and transverse drains.

Drain Box inposition

Truck Drain Box

Figure 1.

Modern products of a similar styleare being used and good practiceis being developed on the secondgeneration of UK tram systems andin the recent multi-million poundrefurbishment and upgrade of theBlackpool Tramway. Some examples

of drainage products used recentlyare shown below, at Fleetwood(Figure 2), Metrolink City Centrerenewals (Figure 3) and Dublin LUAS(Figure 4).


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outlet to cross drains under the track,similar to the pipework in the righthand image.

Little design advice is currentlyavailable as to what can beconsidered good practice. Themost authoritative guidance isgiven by the Office of the RailRegulator (ORR) document RailwaySafety Publication 2, Guidance ontramways, November 2006. Clause119 states, Grooved rails should

have suitable drainage provided atappropriate intervals and locations(e.g. areas of ponding, bottom ofgradients), and when laid in thehighway, connected to surfacewater drainage systems. The drainsshould be capable of being easilycleaned to allow removal of sandand other debris. The provision ofdrainage slots should not render therail incapable of providing sufficientsupport or guidance for trams. Note:The effect of the presence of railgrooves on highway drainage may besignificant.

Thus the two aspects to be dealt withare spacing, what is appropriate,and maintenance, how should afeature be easily cleaned?

During 2009, as part of the MetrolinkPhase 3 implementation, a reviewof these issues was undertaken byAtkins on behalf of GMPTE. Theelements of good design that

were thought to be important aresummarised below, from the threepoints of view of a tramway drainagedesigner, the Asset Managerfor GMPTE and for StagecoachMetrolink, which has operated thetram service and maintained thenetwork since July 2007.

At Fleetwood, the existing trackwas drained using the Edgar Allenproducts from the 1920s or earlier.A replacement product for the pointdrain was recommended by Atkinsto the contractor and this wasadopted and can be seen on theleft of the three images above. Thechoice was based on two of the keyelements developed as good practice,described in more detail below. Inparticular, this product allowed for a150mm groove length and a vertical

Figure 2.

Figure 3.

Figure 4.

Elements considered goodpractice

The key points from a designersperspective are:

Maximum spacing of groovedrains 60m for roads flatterthan 2%

Exceptionally increase to100m

For roads steeper than 2%,review the above criteria andperhaps allow greater spacing

Outlet orientation verticalleaving the drainage unit,with minimum diameter75mm

Point drainage units onshared running

Point or transverse drainageunits if segregated

Slot at least 20mm wide by150mm long

Slot smooth edged andchamfered

An appropriately sizedsilt trap (perhaps a roadgully) should be sited at ordownstream of the groove

drains, to allow easy andregular maintenance

Owners and operators shouldagree funding of adequatemaintenance of drainagefeatures.

These key lessons werereinforced by a tramway AssetManager to emphasise:

The the geometry of,and relations between,

the various road andtrack surfaces need to beunderstood to define therequirement for transversedrainage as opposed to apoint drain on its own

Drainage is needed at thebottom of a valley

Drainage is needed to protectany set of points at thebottom of a gradient

Intermediate drainage isneeded on a gradient tocatch detritus and prevent abuild up further downhill

Careful specification of the


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136 Tram drainage

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Drainage

Figure 5.

Figure 6.

Figure 7.

It is clear that good practice is beingdeveloped, though guidelines are notdefinitive. Products are still beingtrialled and the effectiveness of theseassessed. Manufacturers producingwell used products include ACO,Hauraton, Riecken, Hanning & Kahland Birco. An area currently beingaddressed by work in Fleetwood andDublin relates to the better cuttingof the slots within the groovedrail. Over the last 20 years, this wasimproved from small, poorly cutgrooves (Figure 5); to longer slotsdrilled and cut, though still withunintended irregularities to catchdebris (Figure 6); to a slot milled inthe rail, producing an even slot withno irregularities (Figure 7).

Problems associated with tramdrainage insufficiency are illustratedby two Case Studies, The effects ofpoor drainage on a tramway andDifficulty of maintenance affectingthe performance of tramwayoperation. These illustrate howelements of the developing conceptsof good practice in UK tramwayswere put in place to improvethe future maintainability of theManchester Metrolink system, usingexisting maintenance operations tobring about necessary changes.

Case Study 1 - Theeffects of poor drainageon a tramway

Introduction

A major interchange between bus,Park & Ride and Metrolink wasconstructed at Shudehill in 2002,

just a 5 minute walk from theArndale Centre and located next toThe Printworks, a state of the artentertainment complex located in theheart of Manchester City Centre witha range of restaurants, bars and clubsalongside a cinema and gym. Thisvaluable additional asset to GMPTEwas a retrofit to the existing CityCentre tram link joining Victoria andPiccadilly Main Line stations, whichhad opened ten years previously in1992.

The problem

Three issues combined to make thetrackslab beneath the rails subside.First, the track was level; secondly,a significant catchment of tramand highway drainage fell towardsthis flat area; and thirdly, the blockpaving between the platforms provednot robust enough to shed all thiswater to the drainage channels andprevent water percolating through

to the trackslab formation. Plate 1-1(Figure 8) shows severe degradationof the track and the surroundingsurfaces. The trackslab had sunkin places, giving rise to uneven ridequality through the tramstop. This

four foot, shoulder, six footand cess profiles to avoidponding.

The key points from an operator/maintainer perspective are:

Groove slot machined andlarge/wide enough to copewith the odd leaf or otherdetritus. Narrow short slotsno good

Good drainage in front of all

facing points

No boxes on curves risk ofrail fracture

Drainage solution shouldhave the necessary volume/capacity within the pointor transverse drain suchthat anything greater thana shower does not cause itto back up or require it tobe cleaned out every week

because of sludge build upwithin. Ideally a good cleanat start of autumn and againin the spring with perhapsattention during winteras required should be thefrequency that should beaimed for

Access to the drainage boxis easy i.e. easy removal ofthe lid, and large enoughsuch that it can be cleaned,

ideally by mechanised means(gully sucker) to speed up themaintenance process

One size/type does not fitall; the appropriate drainagesolution must be put inplace dependant on thelocation and the objective,be it groove or switch tipdrainage, point or transversedrainage, segregated or non-segregated, trafficked or non-

trafficked locations

The ideal spacing depends oncircumstances at each groovedrain location.


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failure had occurred in less than 8years use of the new tramstop. TheCity Centre track had already beenscheduled for entire renewal in 2009,so the opportunity was taken toinvestigate the problem thoroughlyand propose a more robust solution.

Plates 1-2 (Figure 9) and 1-3 (Figure10) show how cores were taken ofthe existing trackslab. These led tothe conclusion that the trackslabhad failed to the extent that this

would require total replacement. Inaddition, surveys were made of thecatchments contributing surfacewater to the tramstop area.

Drainage survey

This was a simple visual survey ofthe area, assessing the position ofexisting road gullies, falls on thehighways and tramway towards thetramstop and consideration of thehighway drainage as it would havebeen prior to construction of thetramway. It was determined thatShudehill itself, several hundredmetres of tramway and the tramstopitself all contributed surface waterrunoff, which congregated onthe flat track area between theplatforms. The tram movementsand water led to failure of the blockpaving and generated sand and silt atground level that blocked the lineardrainage channels at the foot of theplatform walls. This led to more

water being retained in the tramstoparea and the cycle of degradationcontinued. A study of As Builtrecords demonstrated that adequateoutfalls had been provided for thetramstop drainage, connectingto public combined sewers, buthighway drainage on Shudehill hadnot been installed upstream of thetramway. The tramway created anew pathway for the highway runoff,rather than the water continuing on

to gullies downstream of the routeof the tramway, which would havehappened pre Metrolink.

Maintenance

Regular maintenance of the drainagesystems at the tramstop was notconsidered a priority, leading to totalfailure of the linear drainage system.Highway drainage maintenance waseffective, but only of gullies alreadyinstalled.

Improvements

Drainage to the formation wasinstalled, the complete trackslabwas replaced and drainage of thegrooved rail was introduced. Theexisting outfalls from the tramstopdrainage were utilised, but additionalchambers and rodding points wereincluded on the formation drainage,

Figure 8. Plate 1-1: Shudehill tramstop in Manchester, showing distressed tracks andsurfacing

Figure 9. Plate 1-2: Ground investigation set up


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136 Tram drainage

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Drainage

Figure 10. Plate 1-3: Recovery of cores Figure 12. Plate 1-5: and at tramstop

Figure 11. Plate 1-4: Groove drainage upstream of Shudehill

to allow better maintenance facilitiesfor the future. As well as improvingthe foundations for the trackslab, the

formation drains provided outfalls forother drainage features introducedat the tramstop. This includedtransverse drains as shown in plates1-4 (Figure 11) and 1-5 (Figure 12),a replacement of the linear drainage

channels at the foot of the platformwalls and rodding accesses. Thoughit would have been preferable to

increase the size of the channels,this proved impossible due to othertramway infrastructure, namelycommunication and power ducting,being located immediately belowthe channels. Thus like for like

replacement took place. The finalimprovement, not driven by the

drainage needs, was the changeof finished surface between andaround the new grooved rails, fromconventionally laid block paving ona sand bed to exposed aggregateconcrete. This choice, driven byexperience of the failure of thesurfacing at Shudehill and otherlocations also reduced substantiallythe likelihood of further drainagefailures. The work was completedbetween April and November

2009, when the cross city tramwaywas closed for renewal, and it isanticipated that such a renewalwill not be necessary again forperhaps another 20 years. It wasalso recommended that ManchesterCity Council should install additionalgullies on Shudehill to catch more ofthe highway runoff before it reachedthe tramway.

Conclusions

Detailing of drainage features atinitial design can have implicationson the life of transport infrastructure.In the case of a tramway, it iswell known that rails wear out,particularly when sharp radii are


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necessary to negotiate an existingcity street layout. A need to renewthe rails after a seventeen year lifewas not considered by Metrolink asunreasonable, but for the trackslabto have needed replacement as wellcan be considered an avoidableexpense. Drainage failures were notthe whole cause of the problem,but were certainly a contributingfactor. Drainage improvementswere introduced throughout the CityCentre as part of the latest trackrenewals at locations identified asproblematic. Surface finishes alsochanged, to improve the Manchesterstreetscape. A combination of thesefeatures is shown in Plate 1-6 (Figure13), on Mosley Street, outside theCity Art Gallery. The general area isshown as Plate 1-7 (Figure 14).

Case Study 2 - Difficultyof maintenance

affecting theperformance oftramway operation

Introduction

Metrolink carries nearly 20 millionpassengers every year, on three linesfrom Altrincham, Bury and Eccles intoManchester city centre. The Buryand Altrincham lines opened in 1992and the Eccles line in 2000, creating

a network of 37 stops covering 37km (23 miles), served by a fleet of 32trams. By 2012 four new lines willnearly double the size of the tramnetwork with 20 miles of new trackand 27 new stops. The new lineswill go to Oldham and Rochdale,Chorlton, Droylsden and MediaCity. At Media City, an existing trackcrossover on the Eccles line needs tobe brought into continuous use toallow the trams to access the new

stop.The problem

Though drainage of the groovedrail had been introduced for theEccles extension of Metrolink, the

Figure 13. Plate 1-6: Groove drainage at Mosley Street

Figure 14. Plate 1-7: by the City Art Gallery

drainage feature used could not bereadily maintained. This allowedwater from the road to the northof the Broadway tramstop to flowdown the rail grooves. Water thatfalls on the four foot (between the

rails) and the six foot (between thetracks) flows along the groove untilthe groove is full before it overflowsto the roadway surface and flowsto the kerbline to be collected bythe highway drains. So, a relatively

light shower of rain produces asignificant flow of water in thegrooves, which flows through thetramstop, collecting grit all thetime, then discharges close to thepoints mechanism which forms the

crossover. The build up of grit anddebris makes the operation of thepoints unreliable.

Plates 2-1 (Figure 15) to 2-4 (Figure16) illustrate the elements of the


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136 Tram drainage

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Drainage

Figure 15. Plate 2-1: New Media Cityextension

Figure 19. Plate 2-5: A light summerstorm

Figure 16. Plate 2-2: Broadway stop, no

groove drainage

Figure 20. Plate 2-6: The effect!Figure 18. Plate 2-3: The crossover

Figure 17. Plate 2-4: The pointsmechanism

Figure 21. Plate 2-7: Groove drainageupstream of Broadway

Figure 22. Plate 2-8: extending for akilometre

problem; the new track to MediaCity under construction; the existingBroadway tramstop, some 200mlong with no groove drainage; thecrossover to be brought into constantservice; and the points mechanismadjacent to the grooved rail end. Alight summer storm of about fifteenminutes duration filled the grooveand brought silt down to the pointsmechanism. The build up of debris

can be seen adjacent to the rail.This is illustrated above in Plates 2-5(Figure 19) & 2-6 (Figure 20).

Maintenance

The road leading to Broadwaytramstop (South Langworthy Road)has a wide six foot (the spacebetween the two tram tracks)marked as a ghost island withpedestrian refuges. It is a busy urbanroad, as can be seen in Plates 2-7

(Figure 21) and 2-8 (Figure 22).The groove rail point drains can beseen within the four foot (the spacebetween the two rails of a singletram track). The tops of these aresecured by two Allen screws andthere is a 50mm horizontal outlet.

To clean these, traffic managementwould be needed to run trafficon the six foot. This can only beachieved during a night time closureof the lane. On a site inspectionto review the problem described, itwas observed that most of the slotsand the boxes below appeared tobe silted up, which suggested thatmaintenance is problematic. Thisis clearly not an easily maintained

feature.

Asset management

GMPTE has appointed an assetmanager to assist the processes asnecessary. Day to day operation andmaintenance are the responsibility ofthe Operating Company, at the timeof writing Stagecoach Metrolink. Themaintainer used its term contractorto inspect one of these features in

detail. First the sewer was surveyedand a 150mm connection waslocated, this being constructed aspart of the sewer diversion works forthe tram. Then, using an endoscopeit was shown that the track drainagebox has a 50mm corrugated pipe on


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its outlet. This pipe is approx 400mmin length and then connects into the150mm plastic drainage pipe whichthen runs into the 525mm mainsewer. The box lifted was on the cessrail (nearer the kerbline) and thus itcan reasonably be assumed that the150mm pipe spans the four foot.

Improvements

An improvement to the drainage wasproposed. The style of groove drainbox used for the Metrolink Ecclesextension is no longer favoured, withan irregular cut in the groove andonly a 50mm horizontal outlet forwater and silt. A point drain product,shown in Plate 2-10 (Figure 24), hadrecently been installed in Fleetwood,as part of the Blackpool andFleetwood Tramway Improvements,with a well machined slot anda 100mm vertical outlet. It wasrecommended that one or more ofthe existing groove drains on South

Langworthy Road should be changedfor a more easily maintained feature.Other improvements recommendedwere for a variety of transverse trackcrossings by several manufacturers,to give the opportunity to trialproducts, regularly used in Europe,for the first time in the UK.

Within the tramstop area and inother areas of segregated tramwaysrunning on grooved rails, it is moreusual to use a transverse drain.

Two manufacturers productswere recommended for trial atthe Broadway tramstop. One ofthese is heavy duty and is claimedby the manufacturer as suitablefor use in shared carriageway aswell as on segregated areas. Thismanufacturer also offers a lighterduty hinged product that is moreeasily opened. Examples of theseare shown in Plates 2-11 (Figure 25)& 2-12 (Figure 26), both of which

have vertical 100mm outlets throughthe trackslab to a bend and outfallpipe below. An alternative, with ahorizontal pipe beneath the track,was also considered for trial (Plates2-13 (Figure 27) & 2-14 (Figure 28)).

Figure 23. Plate 2-9: Groove drainageupstream of Broadway

Figure 27. Plate 2-13: Transverse drain

Figure 24. Plate 2-10: and at

Fleetwood

Figure 25. Plate 2-11: Transverse drain ina trafficked area

Figure 28. Plate 2-14: details ofundertrack drain

Figure 26. Plate 2-12: and asegregated track

These recommendations wereleft with TfGM, who would haveto determine an appropriateprocurement strategy for the worksand assess the timing so that theworks would complement thefirst of the new Metrolink Phase 3extensions opened, to Media City inSeptember 2010. TfGM determinedthat it would be impractical toreplace any of the defective pointdrains on South Langworthy Road,but two transverse installations werecompleted, a narrower one at theinbound end and a wider one atthe outbound end of the Broadwaytramstop area. These were bothsupplied by the first of the twomanufacturers suggested by Atkins.


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Drainage

Figure 29. Plate 2-15: Wide transversedrain Outbound

Figure 31. Plate 2-17: The points able tofunction well

Figure 32. with clean trackbeddownstream of drains

Figure 30. Plate 2-16: and narrowInbound

These were photographed in August2012 after they had been operatingfor twelve months and wereobserved to be successful. The tramservice to Media City service operatesas a shuttle during the daytime; everyother tram terminating at MediaCity, the others travelling to Eccles,but in the evenings and at weekendsall trams run via Media City. Thus,the formerly unreliable points arenow operating on a daily basis andare no longer a maintenance issue.The completed installations areillustrated below in Plates 2-15 to2-18 (Figures 29-32). Atkins offeredthe client an understanding of thenature of the problem, a range ofoptions to provide a solution andsupport for TfGM to procure thisbased on knowledge of the variousmanufacturers products and contactdetails for pricing and supply.

Stakeholder engagement

Tramways are being delivered usingDesign & Build forms of contract.Extensions or improvements toexisting systems in the UK and thecomplete creation of a new systemhave been commonplace for the last20 years. The owners of the assetscreated will generally be a localauthority or a Passenger TransportExecutive. This body will have a longterm responsibility for maintenance,such as the 125 years that BlackpoolBorough Council and its precedingbodies have been successfullyrunning a tram system in Blackpooland Fleetwood. The operatormay change, perhaps as furtherextensions are added. TfGM isworking with its third operator sinceit opened in 1992. Designers forthe drainage of trams can work forany of the above stakeholders. Theparameters for the design cannot betoo prescriptive and each stakeholder

can have a slightly different emphasison the outcome of the design. Allparties need to engage in theseissues from preliminary designthrough to construction.

Conclusions

From this case study, specific totram drainage but of interest toall drainage construction, theelements of the need for designingwith maintenance in mind are wellillustrated. It is not easy to predicthow the future needs of a transportsystem will change. In this case, anoperational feature (the crossover)will change from occasional to hourly

use. The cost of failure of the asset(the points) will be on the operationalefficiency of the tram system.Inbound trams would be unable tocall at the highly prestigious MediaCity tramstop. As this will be theheart of the BBC, the ensuing poorpublicity could, literally, be broadcastfar and wide! Thus the failure of asimple drainage feature, or the poorchoice of a product for reasons ofeconomy, expedience or availability,

has far reaching conclusions.


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Acknowledgements

Thanks to my colleague, Chris Potter, for providing his constructive review of the script. Constructive comments fromMatthew Hack, the Asset Manager for Transport for Greater Manchester (TfGM) on a draft of this paper are gratefullyacknowledged, as is the permission of TfGM to publish the two case studies. These were initially prepared as part ofthe CIRIA RP941 draft report published in 2012 Transport infrastructure drainage: condition appraisal and remedialtreatment and CIRIAs inspiration for this paper is recognised.


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Environment&Sustainability

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25

Introduction

The Winter Haven City Commissionapproved the Sustainable WaterResource Management Plan in2010, establishing a new directionfor managing water resourcesin Winter Haven and the PeaceCreek Watershed (Atkins 20102).The Sustainability Plan outlines anapproach for managing watershedresources that relies on existingnatural infrastructure, therebyreducing costs to the public andproviding multiple benefits with

respect to water quality, watersupply, flood protection, and naturalsystems.

Impervious urban land uses andconversion of wetlands to developedland uses degrade watershed

Winter Haven Chain of Lakes:conservation and restorationtargets for sustainable andinnovative watershed planning

Abstract

A model for identifying conservation and restoration targets in the PeaceCreek watershed was developed in response to the Sustainable Water

Resource Management Plan completed for the City of Winter Haven,Florida (Singleton 20111) and is presented here. A GIS button tool wasdeveloped to automate scenarios of various combinations and rankings ofwater resource functions (e.g. surface and ground water) and subsequentlyidentify conservation and restoration targets in the watershed. These targetsprovide a mechanism for selecting locations for conceptual design projectsand feasibility studies, identifying opportunities for trade-offs betweendevelopment and resource benefits, quantifying loss of ecosystem services,and mitigating for that loss. The resource targets provide a context to guideland use ordinances, development regulations, and develop incentives forprotecting water resources.

Identifying areas for future restoration and conservation is critical to planning

efforts in the Peace Creek watershed. Conservation and restoration targetsare based on available watershed-level data so that potential projects may beranked relative to each other and displayed as maps. Once targets becomepart of the planning process, specific projects can be selected based on site-specific feasibility criteria and development can be directed consistent with therestoration and conservation targets.

Animated and pdf versions of the Plan can be obtained at:http://northamerica.atkinsglobal.com/WHSP

functions, which in turn contributeto flooding, soil erosion, water(and water supply) pollution,and loss of recreational uses ofwaters. Integrating ecosystembenefits or services into land useplanning has only recently becomepart of a sustainable planningapproach (Collins et al. 20073). TheDevelopment of Conservation andRestoration Targets for SustainableWater Resource Management(or Resource Targets) further

develops the concepts presentedin the Sustainable Water ResourceManagement Plan by presenting amodel for identifying conservationand restoration target areas for thewatershed.


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A GIS button was developed

that allowed the user to evaluatechanges in resource functions invarious combinations (e.g. withand without habitat data)

Data were integrated to providecomposite water resource datalayers

Locally-specific data were addedto the watershed-scale datato refine areas for which morespecific data were available.

Ninety-six available data sourceswere reviewed for data relevant toresource functions and benefits.Available data that were insufficientin areal extent to cover thewatershed, characterized by limitedor no relationship to evaluating theresource benefit, or unquantifiable,were excluded from further analyses.Fifteen individual data layers weresubsequently retained to characterizethe resource function layers.

Data were first evaluated forrelevance to particular resourcefunction, such as surface water,groundwater, or habitat (surfaceand groundwater were furthersegregated into surface water quality

recharge is a water resource function

and a measureable attribute (i.e.recharge potential), that translatesto resource benefits, including watersupply, water quality, fish and wildlifehabitat, etc. The approach relied onfour primary components (outlinedbelow).

Conservation and restorationtargets were developed at a scaleconsistent with that of available,relevant data. For example, landcover data are available for the

entire watershed and illustratedifferences between the moredeveloped northern and lessdeveloped southern watershed

Data were acquired for theseanalyses and, in later steps, wereranked as a means of evaluatingthe landscape, both temporally(historic vs. existing) and spatially(across the watershed). Thisprecludes the use of data thatare not available for the entire

watershed Data were ranked as a means of

scoring and comparing data thathave different units of measure

The purpose of the project was todevelop conservation and restorationtargets that can be used to supportfuture land use decisions in the Cityof Winter Haven and surroundingPeace Creek watershed. Toaccomplish this, available data werescreened for relevance and scaleappropriateness and a GeographicInformation System (GIS) platformwas used to create GIS layersthat represent five water resourcefunctions: surface water quantity,surface water quality, groundwaterquantity, groundwater quality, andhabitat. Data intercepts representingthe links between resource functions(e.g. surface water quantity) andbenefits (e.g. water supply) wereused to develop the resourcefunction layers (Figure 1). Analysisof pre-developed (or un-impacted)conditions of resources provided thebasis for target areas: those with theleast (or no) difference with respect

to undeveloped (e.g. circa 1940s)conditions are referred to here asconservation targets, while areas thatexhibit greater changes are referredto as restoration targets.

The product is a map of waterresource management targetareas, represented by waterresource data layers, in thewatershed. In addition to spatialextent of targets, this studydocumented an estimated loss of

20,815 acre-feet of surface waterstorage loss since the 1940s as aresult of the loss of wetlands andreduced lake levels.

Methods

Five resource functions were definedto characterize the hydrologic andecological character of the PeaceCreek watershed: groundwaterquantity, groundwater quality,

surface water quantity, surface waterquality, and habitat. A resourcebenefits matrix (Table 1) summarizesthe links between the resourcefunctions (GIS layers) and resourcebenefits. For example, groundwater

Figure 1. Example of integration of data layers used to evaluate resources and developresource conservation and restoration targets


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137 Winter Haven Chain of Lakes: conservation and restoration targets forsustainable and innovative watershed planning

27


Table 1. Resource benefit function matrix: indicates relationships between resourcefunctions and benefits (x indicates relationship)

*Data layers included under a previous resource function. FLUCFCS = Florida Land Use Cover andForms Classification System, used in combination with other resource function data layers as ameasure of urbanization impacts. NA=not

Water ResourceFunctions

Data Attribute(defined belowtable)

Water Resource Benefits (Targets)

WaterSupply

WaterQuality

FloodProtection

Fish andWildlife

Recreation/CulturalResources

Groundwater

StoragePotentiometricsurface

x x x

Discharge (tosurface water)

NA x x x x

Recharge Recharge x x x x

Hydraulicconductivity

Soils x x x

Quality RCRA, SWAASurface Water

Nutrienttransport/mediation

Impairment x x

Sedimentstabilization

NA x x x

StorageWater levels(naturalwetlands

x x x x x

Discharge (tosurface andground water)

Recharge* x x x x x

Water transport Connectivity* x x x x

Quality Impairment

Habitat

Climateregulation

NA x x

Nutrientassimilation

NA x x x

Groundwatermediation

Groundwater* x x x x

Surface watermediation

Surface water* x x x

Soil formation Soils* x x x x

Connectivity SHCA x x x x x

Effect onother resourcefunctions**

FLUCFCS x x x x x

and quantity and groundwaterquality and quantity). Some datawere then combined with a seconddata layer to produce the appropriatedata field for analysis. For example,land use was used in combinationwith recharge data to identify highvs. low recharge areas. Integrated(or composite) data layers for aresource function were developedfrom the individual data layers bysumming and averaging data foreach location across the watershed,thereby integrating GIS data layersinto a composite resource function(e.g. surface water quality) datalayer. The composite layer is theequivalent of the resource functionlayer (Figure 1). For example, thehabitat function is a composite oflisted species data, habitat type,land use, and adjacent land use, andalso addresses connectivity amonghabitats that typically reflect streamsand wetlands. The process of data

compilation, evaluation integrationinto GIS, and ranking and evaluationthroughout the watershed issummarized in Figure 2. The moredetailed data and ranking process areoutlined in Table 2.

In the same way that non-parametricstatistics rely on ranked data whenconventional parametric analysesare inappropriate, data wereranked as a means of allowingcomparisons across resources with

different characteristics and units ofmeasure. Altered conditions wereassigned a value = -5 (representingrestoration), while relatively pristineconditions were assigned a value =+5 (representing conservation)with respect to a particular resourcefunction (e.g. surface water storage).Values of 0 were assigned todata if a restoration or conservationcondition could not be established.Therefore, areas in which the

potentiometric surface has declinedwere ranked -5 while areas whereit has not declined were ranked+5. Similarly, undeveloped highand moderate infiltration soils wouldbe considered conservation potential,while developed high and moderate

infiltration soils were identified forrestoration.

Final composite water resourcedata layers and the water resourcemanagement target areas werebased on scenarios in which variousresource function layers wereassigned different priorities (e.g. 1

for surface water quantity and 2 forgroundwater quantity). A locationfor which averaged ranks among thefive resource function layers indicatedrelatively pristine water qualityconditions, unaltered groundwaterand surface water conditions, andnatural fish and wildlife habitatalso represented a location with


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a high conservation potential. Incontrast, a location in which allthese resources are altered would be

assigned a high value for potentialrestoration.

Although the process described herewas carried out for all five waterresource functions, a single example(surface water quantity) is presentedto illustrate the development of apotential water resource target.

Surface water quantity

The surface water quantity resource

function represents the changein surface water storage betweenhistoric (1940s) and currentconditions. Restoration is a measureof lost water storage, but not theoverall quality of, for example, a

Figure 2. General approach to developing conceptual conservation and restoration resource targets

wetland that still has storage buthas been impacted by agriculturalpractices for decades. Therefore,

this resource function representspotentially recoverable waterstorage in the case of restorationtargets and opportunities for waterstorage management in the case ofconservation targets. Connectivityis difficult to measure, but isimportant when considering thehistoric surface water connections.While connectivity is not measuredfor surface water, it can besuperimposed on the targets map toexamine its influence. Connectivity isa measure of habitat, however, andis typically consistent with surfacewater connections.

The areal extent of the surfacewater quantity data layer includes

historical and current wetlands andlakes, including wetlands associatedwith water conveyances such as

streams and creeks, floodplainwetlands, isolated wetlands, andNational Wetlands Inventory (NWI)wetlands (which include seasonallyinundated wetlands). FederalEmergency Management Agency(FEMA) floodplains are designatedfor flood risk and insurance purposes(based on the one percent annualflood occurrence or 100-yearfloodplain) and are not, therefore,included in the analysis. In the PeaceCreek watershed, however, historicwetlands closely follow the FEMA100 year floodplain.

Data layers used to develop thesurface water quantity resourcefunction layer are listed and


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29


1.PROMPT:Choosedatalayersforeachwaterre

sourcefunction

Data LayersResourceFunction

2.PROMPT:Choosedatalayertocom

bine

Data Additions/Combinations

3.PRO

MPT:Choosedatafieldtobeusedforrankin

gforeachdataset

Data Fields

4.PROMPT:Rankparametersinchosend

atafield

Rank Value

5.PROMPT:WeighResourcefunction

layer

Product:Conservation/RestorationTargetScenario

2009LandUse

2008

Potentiometric

Surface

Watershed

Delineation

-5 0 5

Floridan recharge

GroundwaterQuantity

x RechargeDeveloped/Recharge> 10

Undeveloped/Recharge 1to 10

Undeveloped/Recharge > 10

Pre-developmentpotentiometricsurface

x Change Change = 0 NA Change 0

Soils x Infiltration

Developed/

A, B C, D, B/D

Undeveloped/

A, B

Source WaterAssessmentAreas (SWA)

GroundwaterQuality

500-ft BufferInside500-ft buffer

Outside500-ft buffer

NA

ResourceConservationand RecoveryAct Facilities

GroundwaterQuality

500-ft BufferInside500-ft buffer

Outside500-ft buffer

NA

Historical landuse (wetlands) Surface Water

Quantity

x PRE_FLUCFCSLoss ofStorage

Gain /NoChange inStorage

2009 land use FLUCFCSCODE

Ridge/valleylakes

Surface WaterQuantity

x x ImpactedDeveloped/Impacted

Insufficientdata

Undeveloped/Not Impacted

Significantsurface water

Priority NA 0 Priority 1 - 7

Water qualitystatus

x Impaired ImpairedInsufficientdata

Not Impaired

Strategic HabitatConservationAreas (SHCA)

Habitat

Priority NA NA Priority 1 - 5

Historical landuse

PRE_FLUCFCS NA NACypress, SandPine

2009 land use FLUCFCSCODEResidential,Tree Crops

NACypress,Pine Flatwoods

Table 2. Data layer compilation, ranking, and mapping for conservation and restoration targets development (left to right)

Table 3. Data representing surface water quantity resource functions

Table 4. Ranking scale used to assign priority for the surface water quantity resourcefunction

described in Table 3and rankings arelisted in Table 4. The process of dataselection, ranking, and application issummarized in Table 5. For example,the change in surface water storagewas calculated from a comparison ofhydrologic conditions (hydroperiods- see below) under historic andcurrent land use/land use usingGIS and follows the approach usedfor the Natural Systems Model theSouth Florida Water ManagementDistrict uses to model pre-drainage

conditions in the Everglades (SFWMD20104) and refined as presentedfor the Collier County WatershedManagement Plan (Atkins 20105).

Data Layer Description Source, Date

Historic Land UseHistoric land use against which tomeasure changes in land use

Atkins, as developed for Peace RiverCumulative Impacts Study

Current Land UseCurrent land use for comparisonwith historic land use

SWFWMD 20096

Hydrology

Depth and duration of naturalcommunities to evaluate changesin surface water storage betweencurrent and historic land use.

Duever et al. 19867

Attribute Used in Ranking Rank

Change in surface water storage

Loss/gain in hydroperiod -5

No change in hydroperiod 5


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Hydrology scoring is the functionalvalue of a land parcel based on thepersistence of historical hydrologicreference conditions. Hydroperiodsare estimated based on the typicalrange of depth (inches) and duration(days) of inundation of the vegetationcommunity. No change from historicconditions would result in a score of+5, while total loss of hydrology(e.g. a cell dominated by a historiccondition wetland or open waterbody but which now experiences noinundation) would result in a scoreof -5. The hydrology score wasapplied on a 750 feet x 750 feet cellbasis.

The hydrology score for a cell/parcelis based on the ratio of the existingdepth and duration in comparison tothe historic condition, adjusted to ascale of -5 to +5. For instance,a site that historically had an averagehydroperiod of six months and anaverage inundation of 12 inches, butwhich currently is inundated for onlytwo months at an average depthof four inches (i.e. the site currentlyexperiences one-third of the depthand duration of the historic conditionfor that site), would have a hydrologyscore of -1.67. More simply, acypress swamp that was convertedto an urban land use would berepresented by a loss of storage andhave a rank of -5, while a cypressswamp that retained its hydrology

would have a rank of +5.

Surface water quantity restorationand conservation targets are mappedin Figure 3(the footprint of alocally proposed road, the CentralPolk Parkway, is displayed in mapsthroughout this document as forreference). The most conspicuousfeature is the pattern of ridge lakes(along the Winter Haven Ridge)designated as predominantlyrestoration (brown) lakes and the

valley lakes (on the adjacent,lower, Polk Upland) designated aspredominantly conservation (green)lakes. This is consistent with theresult of previous studies of theWinter Haven Lakes that point to

CurrentLandUse/LandCover

Historic Wetland and Lakes Land Cover

Land CoverClass

CypressSwamp

FreshwaterMarsh

MesicHammock

SwampForest

Lakes Total

Agriculture -90 -91 0 -344 -101 -626

Cypress 0 0 0 -39 -2 -41

FreshwaterMarsh

555 0 0 -936 -4,156 -4,537

Golf Course -60 -37 0 -258 -62 -417

Mesic Flatwood -136 -128 0 -108 -20 -392

MesicHammock

-331 -37 0 -517 -77 -962

Pasture & BareGround -2,742 -1,189 0 -5,811 -319 -10,061

Swamp Forest 936 39 0 0 -187 788

Urban -618 -421 0 -1,915 -1,460 -4,414

Lakes 859 839 0 930 0 2,628

Wet Prairie -497 -291 0 -1,782 -211 -2,781

Total -2,124 -1,315 0 -10,780 -6,596 -20,815

Table 5. Calculated changes in surface water storage from historic to current land use/land cover conditions (acre-feet)

the groundwater dependence ofthe ridge lakes and the changes

in these lakes as a consequenceof the declining aquifer. The valleylakes have a greater surface waterinfluence, which is also reflected inthe more elongate shapes comparedwith the round ridge lakes.

The shift from native uplands tourban development represents achange in surface water storage inthe watershed, although the urbanareas actually had greater storage.Consequently, urban areas that

were formerly native uplands wereassigned a value of 0 to avoidthe appearance that restorationwas recommended solely based ona gain in surface water storage. Inaddition to mapping the changesin surface water from historic tocurrent conditions, the loss ofstorage represented by the changeswas calculated. For example, aconversion from wetlands such ascypress swamp and wet prairie to

agriculture and urban land usesrepresents a particular loss of surfacewater storage that may be restored,although restoration of agriculturallands is more likely than restorationof urban lands.

A total of 2,124 acre-feet (Table4) of historic water storage in

cypress swamp has been lost dueto conversion to many differentland uses (e.g. 90 acre-feet ofstorage to agriculture, 60 acre-feet to golf course, 618 acre-feetto urban development). Similarly,6,596 acre-feet of former lake/openwater storage have been convertedto other land covers/uses (e.g. 101acre-feet of historic lakes convertedto agriculture). Overall, this indicatesan estimated 20,815 acre-feet ofsurface water storage have beenlost, primarily due to a conversionof wetlands and lakes to developed(urban, agriculture, and golf courses)land uses (Table 5). These losseswere due primarily to loss in forestedwetlands (cypress swamp and swampforest, 12,904 acre-feet) and openwater/lakes (6,596 acre-feet).

In terms of restoration opportunities,some of the conversions mayrepresent opportunities to regain

water storage. For example, a total of10,061 acre-feet of former wetlandsand open water were lost due toconversions to pasture and bareground (Table 5) and represent aloss of the same amount of storage


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31


Figure 3. Composite surface water quantity resource function layer

that may be seen as a restorationopportunity.

Numerous lakes are mapped asrestoration (brown) due to storageloss, while some are mapped asconservation (green) due to gains.Losses and gains are based oncomparisons between historic andexisting land use cover (i.e. arealextent of lakes) and typical changes

in depth associated with changesin land use. For example, a loss of10 acres of a lake due to a changefrom open water to urban wouldbe a greater loss than a shift to amarsh or forested wetland because

of the differences in water depths.Although changes in lake levelshave not been evaluated for manylakes, a previous study (Atkins 2009)documented an average decline of5 feet in lake levels in the WinterHaven Chain of Lakes. Although dataare available that estimate 1850sland cover using 1927 soils maps, thesoils maps are not pre-development

and differences between the 1927and 1940s land cover maps appearnegligible. Consequently, the existinghistoric (circa 1940s) and current(2009) data are considered the bestdata available for this project.

Conservation andrestoration resourcetarget scenarios

The five individual resource functionlayers (groundwater quality,groundwater quantity, surface waterquality, surface water quantity, andhabitat) were merged to generate aconservation and restoration resourcetarget map that identifies areas for

restoration or conservation, based ona comparison of historic and existingconditions (e.g. historic and existingwater storage) or the presence/absence of historical attributes (e.g.permeable land surface). The fiveresource layers were, metaphoricallyspeaking, stacked together, andthe data in each of the five layerswere averaged together for eachpixel location across all five resourcelayers (refer back to Figure 2) toproduce a single map. Conservat

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