The Trusts Dredging Strategy - Canal & River Trust

The Trusts Dredging StrategyNAG Meeting21st September 2012Graham HollandHead of Asset Management

The Trusts Dredging StrategyCurrent Review – Why Now?• Previous practices not always well defined• Processes – required greater clarity• The need to apply asset management rigour to decisions in linewith the requirements of AMP12/PAS55 – risk management

The Trusts Dredging StrategyDredging methods• Traditional excavation using floating plant and hoppers - normal• Land based excavators possible if access allows - rare• Water Injection Dredging (Rivers, G&S)• Cutter Suction Dredging - rare• Hoeing and Raking – Rivers, and occasional for weed and debris removal• Spot dredging – often high unit costs due to site set upTreatment & Disposal• On-site treatment to lower water content by vacuum, centrifuge, lime, mixing,spreading, drying – expensive, laborious and may increase disposal volumes.• Disposal as on-site backfill to piles or bank protection - preferred• Disposal to local agricultural land – environmental legislation• Disposal to licensed Trust owned tip – few left with adequate capacity• Disposal to licensed waste site – few available in UK, large transport costs

COSTS• Expensive – generally£100k/km to +£500k/km• Waste Regs. making thisincreasingly expensive(doubled 2003 to 2006)• Series of Acts andRegulations 1998 to 2005– still continuing – Trustnot exempt in any way• Traditional disposal tolandfill or to banks andbehind bank protectionpreferred• Liquid waste now bannedso pre-treatment required- lime, centrifuge, PFAThe Trusts Dredging Strategy

8 year cycle – full networkThe Trusts Dredging StrategyIdentification - Hydrographic SurveySingle Point Sonar surveys• GPS Controlled Single Point echo sounding - forreservoir, dock and tidal surveys.• Survey output - contour bed plan, digital terrainmodel, enables volume calculations for dredging andreservoir capacity.Scanning Sonar Profiler surveys• GPS Controlled Scanning profiler - collects a ‘swathe’of data across the canal bed. Many 1000’s of points.• Allows extraction of cross sections extracted at anypoint• Cross section data used to calculate DredgingPriority Trigger (DPT) compliance

The Trusts Dredging StrategyOnboard DisplayRiver Aire –Section locationOn-board display of section ofRiver Aire

The Trusts Dredging StrategySurvey Report OutputsContour chart and ‘run line’ survey ofthe River Mersey at Liverpool DocksapproachColour DTM of Brent Reservoir showingrelic river channel running through centre ofreservoir

• Controlling water levelestablished to ensureaccuracy andrepeatability of survey.• GPS height and positionfound on controlling weir,to accuracy of

The Trusts Dredging StrategyCross Section Analysis• MOC ‘trigger’ box sections developed in late 1990’s. Terminology confusing• Now changing to Dredging Priority Trigger (DPT) box• Cross sections extracted from survey data every 50m and DPT box ‘driven’ over eachcross section• 95% of DPT box must be clear from silt blockage at the ‘best-fit’ location.• Formerly 70% of cross sections in each km must meet the DPT requirement to becompliant - changed to 90% - much tougher testFailing SectionPassing Section

The Trusts Dredging StrategyCurrent 70/30 DPT Compliance Map• Visual display of DPT• Passing lengths shown ingreen, failing lengths in red.• At 70/30 ratio 217km (7%) of3078km of canal and river fail– 93% pass• Time to increase threshold totarget better customer service

The Trusts Dredging Strategy90/10 DPT Compliance Map• At a 90/10 ratio 488km (16%)of 3078km canal and river fail –84% pass• Doubles the number of failinglengths• Better match with customercomplaint data• Target to achieve 90% pass

Dredging score matrixThe Trusts Dredging StrategyRanking - The Dredging Matrix ScoreSections of canal that are identified as ‘failing’ DPT initiates further analysis:• Traffic type – is the waterway commercial or leisure use?• Boat usage – what are the annual lockage figures for the canal?• Water Management – has the pound the ability to act as reservoir storage if dredgingwas carried out (usually deemed as over 5km long).Calculation results in a Matrix ScoreDredging Priority• Matrix score together with customer complaints of obstruction and weed growthallows ranking and priority list for dredging• Planning for dredging work commences.

• National dredging team• Potential dredgingprojects consideredalongside other assetrepairs on risk basis• Term Contract withLand & Water Services• Minimum throughputagreed, when achievedresults in contractdiscountThe Trusts Dredging StrategyProject Delivery

The Trusts Dredging StrategyAnnual Dredging Expenditure1998/99 £500,0001999/00 £1,685,0002000/01 £2,778,0002001/02 £3,773,0002002/03 £6,817,0002003/04 £4,950,0002004/05 £2,230,0002005/06 £4,649,0002006/07 £5,132,0002007/08 £4,770,0002008/09 £2,978,0002009/10 £3,453,0002010/11 £3.546,0002011/12 £3,742,000Current 10 year Average = £4m/year(excludes approx. £0.75m to £1.0m/year spot dredging)

The Trusts Dredging StrategyNew Strategy• Strategy and methodology to be published• DPT boxes logically defined and published.• Failing length threshold reduced to10% from 30%• Increase ratio of spot dredging to main-line dredgingover next 3 years - Cycles analysed and implemented• Total dredging expenditure to rise steadily from around£5m (2012/13) to £10m (2021/22) - but kept underreview for efficiencies• £80m investment over 10 years – and possibly moredepending on Trust risk profile• Better communication of programme and designs toNAG, Waterway Partnerships, stakeholders.

The Trusts Dredging Strategy2013/14 Planned Dredging – HEALTH WARNING! - £6m• G&S/River Severn• Mon& Brec• Ribble Link• Weaver• Selby• Shropshire Union• Slough Arm• River Trent Lock tail• Ellesmere/Chester• Ashton• Erewash• Birmingham Main Line – spot• GU summit – spot• T&M – spot• HNC – spot• Harecastle/Macc – spot• Daw End/Rushall – spot• Various other spot locations under review