The Crane operational catchment

Transcription

1 The Crane operational catchment Thames River Basin Management Plan consultation support pack Nov 2014 This pack is to help those with an interest in the Crane operational catchment to respond to the 2014/15 consultation on the draft updated Thames River Basin Management Plan. It should be read alongside the official consultation documents and the London catchment summary, and does not seek to duplicate the explanation or information they contain. Access the consultation online at Alternatively you can request a hard copy of the reports and response forms by contacting our enquiries team on or enquiries@environment-agency.gov.uk 1

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3 List of Contents Changes to water bodies information to support consultation question 1 Cycle 1 water bodies Cycle 2 water bodies Proposed changes to designated uses of heavily modified and artificial water bodies Long-term objectives for 2021 information to support consultation question 2 Catchment Data Explorer information to support consultation question 3 Measures information to support consultation questions 4 and 6 Catchment-wide measures for all water bodies Measures for the Crane GB Measures for the Yeading Brook GB Measures for the Port Lane Brook GB Measures for the Duke of Northumberland s River at Heathrow* GB *includes measures for the Duke of Northumberland s River at Twickenham and the Longford River these rivers are not currently on the proposed cycle 2 water body network but were included in the costbenefit analysis Measures for Kempton Park East Reservoir GB Cost benefit analysis final appraisal report information to support consultation question 5 3

4 Water bodies in RBMP cycle 1 (current) 4

5 Water bodies in RBMP cycle 2 (proposed) 5

6 Long-term objectives for 2021 We are proposing long term objectives of good ecological status by 2021 for the Crane water body, and good ecological potential by 2021 for the other water bodies. 6

7 Catchment Data Explorer Information about the status of water bodies in the Crane operational catchment can be found doing a classification search on Catchment Data Explorer at 7

8 Proposed designated uses of heavily modified and artificial water bodies. Water body Cycle 1 designated use(s) Proposed Cycle 2 designated use(s) Reasons for change Crane Urbanisation No designated use remove heavily modified designation The most urbanised reaches of the cycle 1 water body have been assigned to other cycle 2 water bodies. Most of the cycle 2 Crane water body runs through open space where measures will not have an impact on buildings or infrastructure and are likely to result in good ecological status. Yeading Brook Urbanisation (applies to cycle 1 water bodies that are merged to create cycle 2 water body) Urbanisation Restoration to a natural state would require major redevelopment, involving the removal of residential and industrial/commercial properties and removal or diversion of roads and railways. Flood protection (applies to cycle 1 water bodies that are merged to create cycle 2 water body) Incorrect designation in first cycle: flood protection structures are not extensive. Flood storage areas do not have a significant impact on ecology; one is been decommissioned. Port Lane Brook Urbanisation Urbanisation Restoration to a natural state would require major redevelopment, involving the removal of residential and industrial/commercial properties and removal or diversion of roads. Duke of Northumberland s River at Heathrow Urbanisation Near-natural conditions could only be achieved through redevelopment involving the removal of residential and industrial/commercial properties and major transport infrastructure. Water Regulation Incorrect designation in first cycle: not used for drinking water supply. Kempton Park East Reservoir Wider Environment Water storage Wider Environment The reservoir is a SSSI. Incorrect designation used in cycle 1: decommissioned as a drinking water reservoir in

9 Measures Measures are on 4 different scales: Catchment-wide measures (listed on the next page) applicable to all water bodies in the Crane catchment. Water body wide measures (listed for each water body) applicable throughout the water body and/or its catchment area. Reach measures (mapped for each water body) measures for specific lengths of river. Note that the colours used are to distinguish neighbouring or overlapping measures and have no other significance. Point measures (mapped for each water body) measures for specific locations centred on a single point represented by a dot on the map. 9

10 Catchment-wide measures measures for all water bodies in the Crane catchment 2041 Only Rain in Rivers - Be a Solution to Water Pollution' pollution awareness campaign throughout the Crane catchment to raise awareness and elicit behaviour change about misconnections, blockages, and other sources of domestic pollution Ongoing, co-ordinated programme for the control and management of Himalayan Balsam in a catchment-wide strategy as a contribution to national Invasive Species Action Plan 2283 Slow the spread of high impact invasive non-native species by adopting good biosecurity practice and by promoting campaigns such as, Check, Clean, Dry and Be Plantwise to local stakeholders who take part in water sports, boating, angling and other activities in or near water Continue to improve knowledge of species distributions and improve public awareness of new and established Invasive Non-native Species through co-ordinated catchment-wide monitoring, surveys and mapping Ongoing, co-ordinated programme for the control and management of giant hogweed in a catchment-wide strategy as a contribution to national Invasive Species Action Plan Ongoing, co-ordinated programme for the control and management of Japanese knotweed in a catchment-wide strategy as a contribution to national Invasive Species Action Plan Promote Local Action Groups in the Crane catchment to engage the support of the third sector in controlling invasive non-native species and in promoting key messages. 10

11 Measures for the Crane GB Measures are to: Resolve failures in Phosphate, Diatoms and Macrophytes caused by pollution from misconnections, Combined Sewer Overflows (CSOs) and shared manholes, urban run-off and incidents Our source apportionment modelling of phosphate indicates: o 20-40% of Phosphate load comes from shared manholes (CSOs) and associated incidents o 20-40% of Phosphate load comes from misconnections o 20-40% of Phosphate load comes from urban run-off o less than 20% of Phosphate load comes from sewage treatment works in the Colne catchment Resolve failures in Invertebrates caused by modified habitat, misconnections and airport de-icer pollution Resolve failures in Fish caused by modified habitat Water body wide measures 2408 In-channel habitat enhancements, removal or replacement of hard bank revetment and bank rehabilitation/reprofiling where appropriate in reaches still to be identified Assess and improve or remove CSOs in the Crane (including part of the Yeading Brook) water body; identify all cross connections and shared manholes and assess, improve and formally permit, or remove these overflows Identify and correct polluted surface water outfalls throughout the Crane water body Coordinated Pollution Prevention/Hazardous Waste inspections of businesses, particularly in the Southall area Rectify the majority of misconnections leading to identified polluted surface water outfalls on the River Crane Assess and improve highway runoff management, including best practice gulley maintenance, throughout the the catchment area of the Crane water body. 11

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13 Measures for the Yeading Brook GB Measures are to: Put mitigation measures in place Resolve failures in Invertebrates caused by pollution from misconnections and urban run-off Water body wide measures Note: water body wide measures were identified for the two separate cycle 1 water bodies which we are now proposing to combine in cycle 2. We propose that otherwise identical actions listed below for both cycle 1 water bodies should be combined into single actions for the cycle 2 water body. 008 Educate riparian landowners along whole watercourse on sensitive management in response to changes to vegetation, hydrology and sediment supply as a result of urbanisation. 009 Enhance channel bed within all railway and road culverts downstream of the A Educate riparian landowners along whole watercourse on sensitive management in response to changes to vegetation, hydrology and sediment supply as a result of urbanisation. 024 Enhance channel bed within all railway and road culverts downstream of Victoria Retail Park Identify and correct polluted surface water outfalls throughout the Yeading Brook West water body Identify and correct polluted surface water outfalls throughout the Yeading Brook East water body Rectify the majority of misconnections leading to identified polluted surface water outfalls on the Yeading Brook East Rectify the majority of misconnections leading to identified polluted surface water outfalls on the Yeading Brook West Assess and improve highway runoff management, including best practice gulley maintenance, throughout the the catchment area of the Yeading Brook East water body Assess and improve highway runoff management, including best practice gulley maintenance, throughout the the catchment area of the Yeading Brook West water body. 13

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16 Measures for the Port Lane Brook GB Measures are to: Put mitigation measures in place Resolve failures in Phosphate and Invertebrates caused by pollution from misconnections and urban run-off; and in Phosphate caused by Combined Sewer Overflows (CSOs) and industry Our source apportionment modelling of phosphate indicates: o Urban run-off and misconnections are a major source of the Phosphate load o Combined Sewer Overflows (CSOs) and shared manholes are a minor source of the Phosphate load o Industry is a minor source of the Phosphate load Water body wide measures 2316 Enhance marginal and in-channel habitats wherever possible along the Port Lane Brook and Felthamhill Brook Identify and correct polluted surface water outfalls throughout the Port Lane Brook water body Co-ordinated Pollution Prevention/Hazardous Waste inspections of businesses, particularly in the Bedfont and Hanworth areas Rectify the majority of misconnections leading to identified polluted surface water outfalls on the Port Lane Brook Assess and improve highway runoff management, including best practice gulley maintenance, throughout the the catchment area of the Port Lane Brook water body. 16

17 Measures for the Duke of Northumberland s River at Heathrow GB Measures are to: Put mitigation measures in place Water body wide measures 2486 Educate riparian landowners along whole watercourse on sensitive management in response to changes to vegetation, hydrology and sediment supply as a result of urbanisation Enhance channel bed within the six road culverts (total length 284m) passing beneath the major roads around the perimeter of Heathrow Airport Remove timber toe-boarding and realign/reprofile banks in appropriate locations still to be identified. Measures for the Duke of Northumberland s River at Twickenham Note: this water body is not currently proposed as a cycle 2 water body, but actions have been identified for it as part of the cost benefit analysis and are listed here. Measures are to: Put mitigation measures in place Water body wide measures 2571 Ongoing, co-ordinated programme for the control and management of Floating pennywort (Hydrocotyle ranunculoides) on the Duke of Northumberland s River as a contribution to the national Invasive Species Action Plan. 307 Remove toe-boarding and realign/reprofile banks in appropriate locations still to be identified. 308 Retain and enhance the vegetation within the river channel and riparian zones. 312 Educate riparian landowners along whole watercourse on sensitive management in response to changes to vegetation, hydrology and sediment supply as a result of urbanisation. 17

18 Measures for the Longford River Note: this water body is not currently proposed as a cycle 2 water body, but actions have been identified for it as part of the cost benefit analysis and are listed here. Measures are to: Put mitigation measures in place Water body wide measure 2558 Enhance channel bed within the four road culverts (total length 250m) passing beneath the major roads around the perimeter of Heathrow Airport. 18

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20 Measures for Kempton Park East Reservoir GB Measures have not been identified for this water body, as we consider it to be at good ecological potential. 20

21 Operational Catchment Economic Appraisal - Final Appraisal Report Further detail, including a list of costs, is available on request Note: appraisal was carried out using Cycle 1 water bodies Overview Operational catchment Crane Part of the London management catchment. Waterbodies: 4 rivers (heavily modified) 2 surface water transfers* 1 lake (heavily modified) *A third surface water transfer, the Longford River, is included in the Port Lane Brook water body. Date economic appraisal started Date economic appraisal completed Name/s of assessor/s Objective and aim of economic appraisal Number of bundles of measures assessed 1 November January 2014 Lead assessor: Amanda MacLean, Catchment Co-ordinator (Brent & Crane) Contributors: Neale Hider, Biodiversity Officer Lucy Shuker, Geomorphology Technical Specialist John Bryden, Biodiversity Technical Specialist Phil Belfield, Fisheries Technical Specialist Karen Douse, Senior Environment Officer Laura Beardsworth, IEP officer (AST) Tom Perry, Area WFD Co-ordinator Objective To identify a bundle of measures to improve all six failing water bodies in the Crane operational catchment to good ecological potential. Aim To identify whether the bundle of measures is cost beneficial or not. One bundle was assessed, comprising all the actions identified to resolve the reasons for failure in the Crane catchment and achieve Good Ecological Potential. 21

22 Overview Risk of failure % applied to recommended bundle of measures 25%. This value is towards the upper end of the low risk category. The great majority of actions, including the key ones, are physical modification or water quality improvement projects that will address issues directly, with relatively certain outcomes when delivered. A small minority of actions require behavioural change. This was approved in a meeting of the the North East Thames Area Economics & Investigations Group* as the right level of risk on 20/1/2014. *The North East Thames Area Economics & Investigations Group is composed of Environment Agency Technical experts from the North East Thames Area Office. Results of Stage 1 valuation for recommended bundle of measures Net Present Value Benefit Cost Ratio: Present Value Benefits: Present Value Costs: 43 million million 44.7 million Non-monetised benefits The following benefit categories were recorded as having significant positive benefit in the AST: Recreation and tourism Aesthetic value Intellectual and scientific, educational Provision of habitat WFD status achievable All water bodies within the operational catchment could achieve Good Ecological Potential by Sensitivity testing Sensitivity testing was carried out within the Stage 1 valuation. In addition we have assessed an alternative high cost scenario. Recommendation of assessor Stage 1+ valuation The bundle of measures is cost beneficial. In addition, there are significant non-monetised benefits. The bundle of measures should be included in the draft River Basin Management Plan for consultation. No 22

23 Overview required? WAG section 5 QA undertaken An informal QA was undertaken by NE area staff in January 2014, however no formal QA has been completed. Detail Bundle/s of measures The main types of measures included in the bundle are to deliver three of the seven key objectives in The Crane Valley - a Water Framework Directive Catchment Plan produced by the Crane Valley Partnership: 1. River rich and diverse in habitats and native wildlife - creating and enhancing wetland habitats throughout the river corridor; reducing shading of the river channel; an ongoing, catchment wide programme for the control and management of Giant hogweed, Japanese knotweed, Himalayan balsam and floating pennywort 2. Clean, clear water- reducing pollution from diffuse and point sources (primarily sewer overflows, domestic pollution, and urban drainage) 3. A natural looking and functioning river with sustainable flow- removing or modifying man-made structures; improving connectivity by removing or bypassing barriers to fish passage; improved water level management; realignment and reprofiling Relevant actions from the Crane Catchment Plan are incorporated alongside others identified by Environment Agency staff. Measures which address no deterioration were removed from the cost benefit analysis of the bundle of measures (as per guidance) before economic appraisal was carried out. The benefits and effects on the wider environment are recorded in the Appraisal Summary Table. Measures have been chosen primarily to address the impacts of significant water management issues causing failures under the Water Framework Directive. Where possible, climate resilient measures have been chosen. However it is considered unlikely that the measures will be sufficient to address all impacts of climate change and we will be assessing the likely gaps before the publication of the final River Basin Management Plans. Reference: Measures, Bundles and Costs sheet (see below) Costs Costs used Total costs for the Crane cost benefit analysis for CAPEX (Capital 23

24 Detail expenditure) and OPEX (Operational Expenditure) are presented in the table below. OPEX costs apply to a minority of actions in this category. Where OPEX costs are expected to be incurred for less than 40 years, they are included in the CAPEX cost. One off CAPEX TOTAL OPEX Medium cost scenario: Annual OPEX (of costs sustained for 40 years) River rich and diverse in habitats and native wildlife Clean, clear water 3,451, ,250 2,750 25,779,672 19,228, ,042 A natural looking and functioning river with sustainable flow 8,765, ,000 6,000 TOTAL 37,996,647 19,569, ,792 In order to account for uncertainty in cost estimates, high and low cost estimates were entered and a calculated midpoint value was used in the bundle of measures. The high and low cost estimates are considered to be the maximum and minimum costs likely, for the most complex and simplest conditions for each measure. For measures where there was more certainty in the cost, one cost estimate was used. The high cost estimates were used to create an alternative scenario for sensitivity testing. Costs were derived from both local and national sources, as follows: Reducing Pollution 24

25 Detail Point Source Pollution Combined Sewer Overflows Costs were provided by Thames Water but were aggregated to cover entire water body catchments for all water bodies identified as being affected by CSOs. Urban Diffuse Pollution Highways drainage Costs for increased gully pot cleaning were calculated using cost estimates provided by London Borough of Waltham Forest. A cost of increasing gulley pot cleaning per km 2 of urban and suburban land was calculated. This figure was multiplied by the urban and suburban area of each water body to give an estimate of increased costs for gulley pot cleaning for each water body catchment. Polluted Surface Water Outfalls were costed at information redacted per outfall project (figure provided by Thames Water) for all water bodies identified as being affected by misconnections and/or urban drainage. For most of these water bodies, the number of outfalls was known from recent walkover surveys. Since no walkover surveys had been carried out on the Port Lane Brook water body, the number of polluted outfalls was estimated from the average of approximately one outfall per kilometre of river in the other Crane catchment water bodies. Other costs were calculated using modifications to the Urban Diffuse Pollution Measures Costs Calculator, a spreadsheet tool developed by the Environment Agency Midlands Region, as follows: Rectifying misconnections The default costs in the tool were used for the high cost estimate. A low cost estimate was calculated using the lower bound of costs in the National Cost Effectiveness Database, on the understanding that a lower figure would be more representative of average costs* than the mean in the cost calculator, which is derived from only two data points (maximum and minimum). *evidence: figures quoted in a National Misconnections Strategy Group presentation indicate an average of 440 per misconnection, whether above or below ground; Policy Consulting Network document quotes an average cost of between 20 and 200, while acknowledging that some will require excavation at a cost of several hundred pounds. Pollution prevention visits to industrial estates The number of 25

26 Detail small and large industrial estates was counted using aerial photography. Awareness campaigns for the general public The default costs in the tool were used as the high cost estimate. The low cost estimate was based on an enhanced version of a current pilot campaign. More accurate population figures for the catchment area of each water body were obtained using data from the 2011 census. Annual savings were included for awareness campaigns, based on the results of the Anglian Water Keep it Clear campaign, where blockages and associated costs were cut by 75%. Applied to Thames Water s current costs of 12 million per annum on blockages covering 9 million customers, this gave an estimated saving of 1 per dwelling. Making Rivers More Natural Project costs were used in cases where they were available (e.g. London Rivers Action Plan; quotes from contractors). However, for the majority of measures, area staff (Fisheries, Biodiversity, Planning & Strategic Overview, and Catchment Coordinators) estimated high and low costs using expert judgement, supported by a list of recent projects in North East Thames and a list of cost estimates for river restoration works from Halcrow (2008). The National Cost-Effectiveness Database was used to supply costs in cases where there was uncertainty concerning the type or extent of works required. Tackling Problem Invasive Species The Biodiversity Technical Specialist used expert judgement to estimate costs per km for a ten-year programme of invasive species management for key invasive species. These costs were applied to the length of river currently affected, as estimated by a Biodiversity Officer with extensive knowledge of the catchment. 26

27 Detail Willingness to pay Central (default) Value used The communities living within the Crane catchment range from the relatively deprived to the more affluent. Extensive reaches of the River Crane and its tributaries are in open space and are used for recreation, so a central willingness to pay value is a good representation of the average. NWEBS baseline The NWEBS baseline was determined using the agreed comparative WFD status approach. The 2013 classification was used to predict 2015 baseline status because it uses the most complete set of sample data and best reflects the current ecological status of water bodies in the Crane catchment between 2013 and There were a number of cases where better local information was available, where data for relevant elements was not available, or where expert judgement indicated that the suggested baseline was not representative of the situation in the water body. In these cases, the suggested baseline was modified to better reflect the current NWEBS condition of the water body. Km /km 2 or m 3 of benefits In most cases, the entire length/area of the water body was Actions to reduce pollution and tackle invasive species will happen on a whole water body basis. Specific measures that have been identified to improve physical habitat cover lengths the equivalent of the river line used as the basis of the calculations. In the cases of the Yeading Brook (east arm) and the Port Lane Brook, measures that have been identified to improve physical habitat do not cover the full length of the water body so only a percentage of the water body was considered to be improved. Where there are substantial culverts that cannot realistically be removed, the length of river benefited was reduced proportionally for Flow and Safety. Benefit lengths were decided by expert judgement. Decisions were made collectively during meetings involving Neale Hider, Lucy Shuker, Laura Beardsworth, Amanda MacLean and Tom Perry. Adjustments to benefit lengths Correcting for duplication of water body lengths The Duke of Northumberland's River at Mogden (GB ) is a surface water transfer 27

28 Detail water body in its own right, but is also included in the Crane (including part of the Yeading Brook) (GB ) water body river line. To avoid double counting benefits along this reach, 2.93 km of benefits (equivalent to the length of the Duke of Northumberland's River at Mogden) were subtracted from the Crane water body. Benefits from improvements to water bodies outside the Crane catchment Improvements to water quality in the Colne catchment (in particular phosphate stripping at sewage treatment works) are expected to provide some benefits to the Crane (), both branches of the Duke of Northumberland's River (), and the Longford River. In order to distribute these benefits in a straightforward and simple manner between the two catchments it was decided to transfer the benefit lengths for Clarity and Plants from the Crane operational catchment to the Colne operational catchment. This is based on the principle that Clarity and Plants are the categories most impacted by actions to improve water quality in the Colne catchment. We estimate that the benefits to plants from physical modification measures will be roughly equal to the benefits to fish and invertebrates from water quality measures, so the overall transfer of benefits between the two catchments should be reasonably accurate. The methodology and reasoning for the transfer of benefit lengths to the Colne operational catchment is described in Appendix A. Once these adjustments are made, the total percentages of river length improved by the recommended bundle of measures in the Crane operational catchment are, for each NWEBS element: Clarity 82% Fish 90% Invertebrates 67% Plants 49% Flow 54% Safety 65% Sensitivity testing WAG section 7 Sensitivity test results are as follows: 28

29 Detail Baseline Whole life costs x 5 Whole life costs x 2 Whole life costs x 0.8 Change in one off costs for BCR to approximate to 1.0 Bundle ref Bundle name BCR Crane midpoint costs NPV x 50% decrease in km benefited Using low WTP value Using central WTP value Using high WTP value Risk of failure is 0% Risk of failure is 25% Risk of failure is 50% This assessment passes all of the sensitivity tests except for Whole Life Costs x 2, which resulted in a BCR of just below 1. However, this is considered to be an unrealistic scenario. Our own high-cost scenario passed the cost benefit analysis with a BCR of The majority of costs in the high-cost scenario are either provided by the water company, or uncertainty has already been built into the costings in assigning a maximum likely cost. Therefore doubling these figures is not considered to be realistic. Appraisal Summary Table WAG section 3 and 5 The AST records the following benefits as having significant positive benefit: Recreation and tourism Aesthetic value Intellectual and scientific, educational Provision of habitat The following benefit categories were recorded as having minor positive benefit in the AST: Fresh water Existence Values Social relations Much of the benefit recorded in the above categories is not monetised in the calculated NWEBS benefits for the catchment. This means that the overall benefit for the catchment is likely to be higher than estimated in the Present Value Benefits figures shown above. None of the benefit categories recorded an overall negative impact as a result of the proposed measures. However, potential minor negative impacts were identified in the case of: Heritage - Minor adverse impacts on the substantial cultural heritage of the Crane were identified as possible, but avoidable. Impacts can be prevented or mitigated for by designing proposals so that they will not damage the cultural heritage (e.g. by installing a 29

30 Detail fish pass around a historic mill structure, thus avoiding change to the historic structure itself). Water for non-consumptive use - Minor adverse impacts of weir removal could limit the opportunities for future hydropower schemes. However, any scheme would be small-scale and there is currently no hydropower in the Crane catchment. Improved flow in the lower Crane should have a positive impact on the potential for hydropower that would balance out these negative impacts. These minor negative impacts should not affect objectives. Engagement operational instruction (450_13) section 2 Internal The Crane Catchment Coordinator (Amanda MacLean) held a series of meetings and discussions with members of the following teams: Costing measures Biodiversity (Neale Hider, John Bryden), Geomorphology (Lucy Shuker), Fisheries (Phil Belfield, Planning & Strategic Overview (Anna Parr), Integrated Environment Planning (Tom Perry), Karen Douse (Land & Water) NWEBS benefits Biodiversity (Neale Hider), Geomorphology (Lucy Shuker), Integrated Environment Planning (Laura Beardsworth, Tom Perry) AST - Integrated Environment Planning (Laura Beardsworth) External Measures incorporate WFD-related actions from the The Crane Valley - a Water Framework Directive Catchment Plan produced by the Crane Valley Partnership. A summary of the process was discussed informally with several key members of the Crane Valley Partnership, including the catchment host. Partnership members have been invited to hear further details on the process and results in February Any other supporting information such as key uncertainties, other rules of thumb used and key assumptions made Nominally the base year for the financial numbers in all CBAs Nationally is 2012 based on the NWEBS values. Consequently all other financial numbers should be either inflated or deflated to their 2012 level. However due to the overall uncertainties around costs, savings and other financial benefits we have not applied an inflation or deflation factor. It is thought to try and use RPI/CPI to adjust costs to a 2012 base level would suggest a level of accuracy to the financial numbers we do not have. It is assumed the use of cost ranges and the standard national sensitivity testing will help to assure a BCR outcome fit for the purpose of a high level assessment. 30

31 Detail COSTS The costs are mostly derived from local costs (based on data from local projects, studies and experience of area staff); in some cases they were derived from the National Cost Effectiveness Database and taken as provided there. Capital costs are placed in the first year of the assessment (2015/16) unless we have evidence of where capital costs will be spent over the time horizon. We assume operational costs will occur in the first year after capital costs 2016/17 and will continue for the remaining time horizon. Operational costs that occur for shorter period of time are included in capital costs. Water Companies costs for water quality measures are placed in line with the schedule provided by them. Urban Diffuse Pollution actions were costed using the National Urban Diffuse Pollution Calculator, with modifications as described above under 'Costs'. BENEFITS It is assumed benefits start two years after capital expenditure (so in most cases 2017/18) and will continue for the remaining time horizon unless we have local or national evidence. As a rule NWEBS baselines and status changes are selected in accordance with National recommendations in the FAQ. However local evidence and expertise was used to override these rules of thumb when required. We do not include any financial cost savings or additional financial benefits unless we have local or national evidence. 31

32 Appendix A The methodology and reasoning for transferring benefit lengths to the Colne operational catchment is described below. Duke of Northumberland s River at Heathrow (water body ID: GB ) The whole length of this river will benefit from water quality improvements in the Colne. Longford River (included in Port Lane Brook water body ID: GB ) The whole length of this river will benefit from water quality improvements in the Colne. River Crane downstream of Duke of Northumberland s River at Heathrow; Duke of Northumberland s River at Mogden (lower section of Crane (including part of the Yeading Brook) water body ID: GB ; water body ID: GB ) SAGIS modelling found that 43% of the phosphate in the Crane was derived from sewage treatment works in the Colne. We therefore need to apportion 43% of the benefits to the Colne catchment. The easiest way to do this is to apportion the length improved between the two catchments. The Crane, downstream of the Duke of Northumberland s River at Heathrow, is 10km, so 43% is 4.3km. The Mogden reach of the Duke of Northumberland s River is 2.93km, so 43% is 1.26km. We have therefore apportioned 4.3km of benefits from the Crane and 1.26km of benefits from the Duke of Northumberland s River to the Colne. 32