IMTH Wey Weirs Refurbishment Project Options Appraisal Stage

Transcription

1 IMTH Wey Weirs Refurbishment Project Options Appraisal Stage Fish Pass Scoping Note 1.0 Introduction This note has been prepared as an Appendix to the Preliminary Environmental Information Report (PEI) to document the development, scoping and selection of fish and eel pass designs that meet legislation and are appropriate for the scale of works to be included within the project or in the complementary Wey Weirs Structures project. Twelve weirs were identified in the Wey Flood Risk Management Strategy and initially included in the Wey Weirs Refurbishment Project. Further detail is contained in the PEI report. They were: High Mill Weir (NGR: SU8647) Elstead Mill Bypass (SU9044) Millmead Bypass, Guildford (SU9948) Stoke Mill Bypass (SU9951) Bowers Mill Bypass (TQ0152) Broadmead Weir, Old Woking (TQ0156) Newark Mill Bypass (TQ0357) Abbey Overfall (TQ0357) Ockham Mill Sluice (TQ0357) Walsham Weir (TQ0557) Bluegates Hole (TQ0761) Hamm Oil Mills, Weybridge (adjacent to Thames Lock - TQ0765) 2.0 Options Appraisal Stage The screening and scoping was carried out for three milestones: Project Planning Phase Options Workshop Preferred Option Development and PEI Report The initial outline design and options screening and scoping developed in a Planning Phase of the project, culminating in a Site Visit and Outline Options Report (Jan 2013). An Appraisal Summary Table was completed identifying a range of options for weir management and fish/eel pass works at each site. It also considered the rationale for which of these should be included in the options appraisal stage of the project. This is reproduced in Appendix G to the PEI.

2 After investigation, it was found that the Agency do own part of Bluegates Hole Sluices, aand there are liabilities laid out in the Title Deeds A fish pass outline design sketch was developed. The Byfleet Weir close to this site was installed as part of the River Wey Improvement Scheme so we also have similar responsibilities for this structure. However, it would appear to be relatively simple to convert Bluegates Hole Sluice gate structure and apron to a fish pass as noted in the Appraisal Summary Table. The design and sketch will be transferred to the Wey Structures Project for potential implementation. In preparation for an Options Workshop held on 19 September 2013, outline designs for the remaining sites and options were developed and costed and then discussed in a webconference on 11 September 2013 with input from the Environment Agency Fisheries team (Steve Sheridan) and Jacobs fish pass specialists (Gillian McCoy and Guy Russell). The presentation on which these discussions were based is included as Appendix 1. It was concluded during the discussions that the preferred option could be identified without the need for explicitly scoring each option with respect to the number of species that could be passed. The presentation included: schematic overall layouts for each weir site sketches on which the fish pass options are based summary costs tables to help identify the most cost effective option at each site At the end of the Planning Stage it was recognised that, relative to the cost of weir works, the cost of making provision for fish passage could be disproportionate. The current FDGiA/Levy funded project does not incorporate fish passes at all of the six priority sites due to the relative costs compared to the scale refurbishment works being proposed. Following a workshop (see Minutes of the Options Workshop held on 19 th September ) further investigation of costs and options for fish passes and priority the most important weirs for fish pass installation were carried out. An extract from the prioritisation paper prepared following the meeting (see Appendix 3) follows: Restoring connectivity from the Thames through the main stem of the Wey (Shalford to Thames waterbody) is a fundamental stage in ensuring GES / GEP objectives can be met throughout this and the other WFD water bodies in the catchment. In terms of a simple prioritisation of the structures for fish passage i.e. focussing on upstream migration from the Thames, suggested priorities are as follows (weirs relevant to this project in bold): Priority 1 Hamm, Byfleet / Bluegates, Walsham, Abbey / Newark, Broadmead, Broadoak, Bowers, Stoke and Millmead - this connects the main stem of the Wey from the Thames to confluences of the significant tributaries Tillingbourne and Cranleigh Waters. Priority 2 St Catherine s, Unstead, Catteshall, Westbrook, Eashing, Somerset, Elstead, Tilford Gauging weir, Frensham Mill (fish pass installed). - This connects the main stem of the Wey to the North and South branches and to the Slea. Priority 3 Numerous but includes EA assets: High Mill and Farnham Gauging station 1 Information taken from Jacobs meeting notes for the Wey Weirs Refurbishment Options Workshop held on 19 th September 2013.

3 When the status of partnership funding, FDGiA funding limitations and scale of works were taken into account, it was agreed at a progress meeting that the priority sites to be included within the project would be Hamm Oil Mills and Walsham (see Appendix 2). Hamm Oil Mills site is the highest priority site in this project for inclusion of a fish pass as there is currently no provision for fish passage from the Thames at Weybridge to the entire Wey catchment. Walsham weir is the next fish passage priority site upstream as it has a large attractive flow and it is highly unlikely that fish passage is possible at this site through the main river past any of the structures at this site. The project cost estimates indicate that including any significant further fish pass works in the project would result in the cost of fish passage exceeding the 25% limit. An extract from the Project Cost Plan evaluating the percentage costs is in Appendix 4. After extensive further work on prioritisation, design development and cost investigation against national average figures, the cost for the 4 other priority sites remains disproportionate, however, eel passes are low cost and a higher statutory priority and are included. While this work will help make significant steps towards achieving WFD on the River Wey catchment, it leaves 3 of our weir structures (Millmead, Newark and Broadmead; Bowers weir is included in a separate bid detailed below) without any provision or commitment within the project or by the Environment Agency as a whole to providing fish passage and requiring this before 2027, i.e. within 13 years. It should be noted that there are other barriers to passage owned by others which in some cases are on parallel channels or shared at the actual weir site. Further significant maintenance on the sub-structure of these 6 weir structures is not expected within the WFD timetable. Under the WFD; it is the Owners responsibility to ensure that eel/fish passage is delivered. Due to the FDGiA funding constraint, additional funding has been investigated.sources of funding in addition to Flood Defence Grant in Aid (FDGiA) were explored such as Levy and potential WFD funding from within the Environment Agency and potential external partners Guildford and Woking Borough Councils and the National Trust. Discussions and meetings were held to explore each of these potential sources. However, only 20k of direct financial partner funding has so far been successfully secured from Guildford Borough Council for works at Millmead with other funds potentially available. These funds are known as S106 funds which need spending by 2017 which cannot be used on design fees or feasibility work. Further investigation continues. Other non-financial contributions have been agreed in principle, including from the National Trust. At this time no additional sources of funding have currently been identified. As such there is currently no certainty of significant monetary contributions becoming available within the expected timescale of the refurbishments works ( ), whilst repairs are needed now. The project has worked alongside the FCRM PSO team and Technical specialists and latterly with an emerging Fisheries and Biodiversity Integrated Environment Planning (IEP) project known as the Wey Forward Project. A funding application has been made including for other fish pass sites, namely Broadoak, St Catherine s, Unstead, the Hell Ditch, and Bowers weir fish pass is now included in this project. There remain 3 other priority sites which currently have no provision, so there remains a risk of failure on the WFD target to the Agency and loss of packaging efficiency. Further opportunities for funding will be explored alongside the Wey Forward Project with construction delivery a potential option through the refurbishment project s Contractor.

4 3.0 Options Development Stage At the Options Workshop held on 19 September 2013 (see Minutes in Appendix 2 the Thames West Area Flood Risk Manager provided a clear direction to the project team that at some of the weirs fish passes will not be possible due to funding constraints unless alternative funding sources rather other than Flood Defence Grant-in Aid (FDGiA) were obtained (e.g. Levy Funding, third-party or riparian owner funding). An appropriate level of FDGiA funding was set at 25% of the capital cost was set as noted above. The Environment Agency Fisheries team were asked to provide justification and prioritisation for the sites (this is contained in Appendix 3). This list was considered in option development. Efforts were made to identify reduced cost options and establish reasonable ratios to allow inclusion of fish passage improvements at all (or at least most) sites. The Fisheries team provided details of costs and alternative designs fish passes installed at other locations. This was examined and showed that, where the extent of fish pass works was comparable, the basic construction cost was similar to the estimates for the Wey Weir sites. The main differences in the apparent total costs for fish pass works arose because of the inclusion of a comprehensive range of on-costs in the estimates for the Wey Weirs project which are necessary to derive a total Project Cost. The costs were also of similar magnitude to a national review of 237 implemented fish pass average costs provided by Daryl Clifton Dey Fisheries Technical Specialist (see dated ). The comparison did allow for additional risk, fees and overheads. Confirmation of earlier verbal advice was received in January 2014 that a fish pass at Hamm Oil Mills has the highest priority, not only for the Wey, but also for the Lower Thames and an agreement that Hamm and Walsham should be progressed first. The options for these sites have therefore been developed and are now included as part of the Wey Weirs Refurbishment Project for which a PAR has been prepared to gain approval for FDGiA/Levy funding. Eel passes using either simple bristle or top-hat panels will be incorporated in the vicinity of all priority weirs being refurbished under the project where there is a fixed crest section (i.e. Broadmead, Newark and Hamm and potentially at Bowers on the National Trust Weir and Millmead possibly on the GBC weir) as well as being integrated into the fish passes on Coleson s Channel (Hamm) and Walsham. Provisional sums are included within the cost plan for the Project Appraisal Report (PAR). 4.0 Water Framework Directive Context The project team have considered the Water Framework Directive (WFD) status and actions for the Wey water-bodies. These are summarised below. The proposed works fall within WFD water-bodies GB Wey (Shalford to River Thames confluence at Weybridge) and GB Thames (Egham to Teddington). They are Heavily Modified Water-bodies (HMWB) classified at Moderate and Poor Ecological Potential respectively. They have water-body objectives to reach Good Ecological Potential (GEP) by Reasons for failure include, for the Wey, Fish (Barriers to Fish Migration being one of the confirmed reasons) and for both the Thames and Wey, Mitigation Measures that are not yet in place. Relevant to this project is Mitigation measure 16, which is currently Not In Place. This refers to: Structures or other mechanisms in place and managed to enable fish to access waters upstream and downstream of the impounding works.

5 As part of a National WFD project, HMWB Mitigation Measures Investigation and Options Appraisal have identified fish pass installation as required at all of these sites for attainment of GEP. However, the WFD project has completed a Cost Benefit Analysis and the targeted package of works for the Wey has been found to be cost beneficial which means the all the actions will go into the updated River Basin Management Plan (RBMP) for consultation (and delivery). In the first cycle RBMP the objective was GEP by 2027, however following the options appraisal and CBA work, the new objective that is being put forward is Good Status for mitigation measures by The current WFD assessment goes on to conclude that a range of resources and partnerships will be required to restore adequate connectivity to the Wey catchment for it to reach Good Ecological Potential / Status. Refurbishment works can offer cost effective opportunities for installing fish passes. It will be important to find fish passage solutions at all sites, where weir works are proposed, that align in terms of design and affordability within the scheme. Inclusion of fish passes at weir sites would help restore connectivity within this water-body for fish (and other wildlife) with benefits for BAP species: eel, brown / sea trout, salmon and lamprey. In addition, this would create new and valuable flow dependent riverine habitats for a variety BAP species and importantly contribute to WFD mitigation measures 5, 6, 16, 19, 20 and 26. The fragmentation of the catchment by these structures not only impacts the ecological potential / status of this water-body but also of those water-bodies upstream, and of the Lower Thames downstream. It is acknowledged that the starting point for improvement is to restore connectivity within the main stem of the Wey. This includes all the structures in this report and, in addition, others both Agency and Non Agency owned. This is reflected in the prioritisation list in Appendix 3 and proposals contained in this note. The project has also been developed and reported through the Wey WFD Catchment Co-ordinator and Catchment Co-ordination Meetings. 5.0 Wey Fish Passage Studies Two reference studies have been used to inform the selection process. 5.1 University of Southampton Wey Barrier Assessment In 2012 a barrier assessment was carried for the River Wey catchment, in partnership with the University of Southampton 2. A geospatial of river infrastructure developed using various databases - National Flood and Coastal Defence database (NFCDD), EA channel section surveys and National River Obstruction Database. This identified 835 structures of which a sample (283) were assessed for passability using field appraisal and through desk study of channel survey information. The information collected during the survey was used to calculate a passability score for different species, families or life stages of fish depending on their swimming and leaping ability, depth requirements and susceptibility to turbulence conditions. Target fish identified by the Environment Agency for the Wey catchment were brown and sea trout (Salmo trutta), cyprinids and the European eel (Anguilla anguilla). Barriers were scored between 0 and 1 for each target species, family or life stage as follows: Value = 0: Complete barrier to passage 2 Eakins, L., Parks, K. and Kemp, P River Wey Barrier Assessment, Phase 1 Final report. Southampton University / Environment Agency

6 Value = 0.3: A partial high impact barrier. Some of the population will pass at some times. For example less than one third of the population will be able to pass, or the barrier is only passable for a third of the time. Value = 0.6: A partial low impact barrier. Most of the population will be able to pass at some point. For example more than two thirds of the population will be able to pass or the barrier is impassable less than one third of the time. Value = 1: The barrier is passable for all individuals at all times An estimate of passability during high flows was also completed. For example if depth is the limiting factor and large species such as trout are impeded at the measured depth, high flow conditions may enable passage. Following the field visit the data was summarised into a database of final passability scores for each fish species, family, or life stage, along with barrier type, location and watercourse name. Summary values for hydraulic head, velocity and depth were recorded where available and the use of the structure if known. Hamm Oil Mills / Coleson s Overfall and Walsham are impassable to all species, scoring zero for each. These large barriers are the first that any migratory species moving from the Thames into the Wey would meet and passage is blocked immediately. Due to the high number of bypasses and side channels there is the potential for some fish species to pass by alternative routes at some barriers. For example at Newark / Abbey there is a pool and traverse fish pass on the Abbey overfall which is passable to adult salmonid fish, though not for juveniles, cyprinids or eel. Newark Weir is impassable to all species. The impoundment upstream of Broadmead is also controlled by structures on a separate channel at Gresham Mill where fish passes are being installed as part of a hydropower development. However a separate channel leads to Broadmead weir which is over 2.5km in length, attracting upstream migrating fish to a structure completely impassable to all species. Bowers Mill, Bowers weir and Millmead Weir also have zero values for upstream passage for all species. 1.2 Lower Thames Fish Passage Study A Lower Thames Fish Passage Study was carried out for the Agency by Babtie, Brown and Root in which ranked priorities for fish pass improvement projects in the Lower Thames catchment. The Hamm Oil Mills site was ranked as top priority of the 19 sites. This study focussed on structures directly impacting the main river Thames fish populations and simply support the importance of this site in the wider catchment context. 6.0 Preferred Fish Passage Options Where preferred options have not been shown for progression within the project, it is understood that the Wey Forward Project will use outline designs and data produced to date will be used to progress these fish passes subject to funding. 6.1 Hamm Oil Mills The preferred fish pass option for Hamm Oil Mills is Hamm_F01 Convert Coleson s Channel, which runs alongside the River Wey Navigation. This would include a pre-barrage at the upstream end of Coleson s Channel at the confluence with the River Wey Navigation, and 3 Lower Thames Fish Passage Study, Babtie, Brown and Root (ref ), Environment Agency Project (ref.1/0776/228/ )

7 modifications to the weir structure at the downstream end of Coleson s Channel at the confluence with the River Thames. The inclusion of a fish passage solution at this site will restore longitudinal connectivity between the rivers Wey and Thames water bodies. From this site downstream, to the Sea, there are existing fish passes installed at all obstructions. 6.2 Walsham At the time of the tele-conference on 11 September 2013, the preferred fish pass option for the Walsham site (principally on cost grounds) was conversion of the existing drain to the south of the main navigation channel. However, subsequent advice from our Estates team was that the natural channel option closer to the weir was likely to be more acceptable to the riparian owners and that contributions may be easier to obtain therefore it is option Walsh_F03 which has been progressed to option development. It was also preferred as an option that would allow the channel profile to be optimised for habitat and passage. 6.3 Abbey / Newark / Ockham There is an existing fish pass adjacent to Abbey weir. The preferred fish pass option (subject to available funding) is Abb_F02 Fish Pass Upgrade Existing. No fish pass options were considered for Newark weir as it was thought to be cheaper and easier to upgrade the fish pass at Abbey as part of the project. Improvements to the fish pass at Abbey weir would help restore connectivity within this water body. Inclusion of an eel pass facility at Newark weir would improve upstream migration and colonisation of eel into the catchment and this has been included in the project. At the start of the options appraisal stage conversion of the Ockham Mill Channel to a potential route for fish passage was considered which would bypass both Walsham and Newark Weirs. Ockham Mill Sluice upstream of Newark Weir allows water to flow into this channel which extends almost 3km downstream, past Ockham Mill to rejoin the Wey. On further examination it was concluded that this option should not be pursued for the following reasons: Additional fish pass structures would be required around the obstruction presented by the Ockham Mill private residential properties The very low flow capacity of the channel compared to that of the main River Wey would be unlikely to provide sufficient attraction for fish at the downstream confluence with the Wey. The option would not facilitate fish passage in the main Wey channel past Walsham Weir and up to the existing fish pass on the Abbey Stream 6.4 Broadmead No fish pass options were considered as part of this project for Broadmead weir. However, to fully meet WFD objectives at this location a natural channel fish pass could be constructed on the right bank of the navigation channel which has a suitable land profile to bypass the weir which would connect with the 2.5km length of the Broadmead Cut below the weir. The layout would be similar to that proposed for Bowers. Alternatively, a Larinier solution similar to Millmead might also be possible. 6.5 Bowers Mill The preferred fish pass option for Bowers Mill is Bow_F03 Naturalised bypass channel on the left bank around the National Trust weir at the upstream end of the navigation channel from the main River Wey channel. This would be the most effective and sustainable solution and would not reduce the National Trust weir discharge capacity. Bowers Mill weir is off the

8 navigation some distance downstream of the National Trust weir. Construction work for a fish pass at this location would be essentially independent of the proposed weir works as land access can readily be obtained via the Slyfield Regeneration Site. The National Trust has indicated that there are no current plans to undertake works on their weir, although the longer term requirement to provide fish passage is recognised. It is therefore recommended that a potential fish pass at this location should be considered as part of a subsequent project, possibly in partnership with Guildford Borough Council as part of the Slyfield Regeneration. 6.6 Millmead The preferred fish pass option for our Millmead Weir is Mill_F01 Larinier, which is the least cost option. Downstream of our weir two other structures (the GBC weir and the Town Mill hydropower plant) owned by Guildford Borough Council also provide obstructions to fish passage However, Millmead Weir is the most upstream obstruction at this site and presents the optimum location for a fish pass facility. GBC has indicated that there are no current plans to undertake works on their weir or the Town Mill, although the longer term requirement to provide fish passage is recognised. The possibility of contributions to construction of a fish pass at Millmead Weir as part of the Wey Weirs Refurbishment Project has been discussed with GBC. GBC has indicated that while contributions in kind (e.g. making land available for access and permanent works) could be considered in a partnership arrangement, but so far only a 20k direct Section 106 financial contribution to fund construction only has been allocated, although more is possible. This means that third-party funding is uncertain within the timescale of the project ( ). 6.7 Elstead and High Mill Outline layouts of options for fish passes at these locations have been developed and will be passed to the Wey Structures project team. However, unlike on the navigable section of the River Wey, there is no requirement to prevent impact to navigation or heritage conservation designation. The benefits of the retained water levels are essentially for amenity reasons relating to local properties. However, as noted in the Site Visit and Outline Options Report, the control of the weirs at Elstead (which is carried out by the managers of the Elstead Mill pub/restaurant owned by Fuller Smith & Turner plc) is important for implementation of the Water Level Management Plan for Charleshill SSSI located upstream. The WLMP states that The river levels are controlled at Elstead Mill and In 1998 a new management regime had been agreed, that the head level will be maintained at 43.60m plus or minus 100mm. This is a more stable regime than that previously operated. Despite this agreement, in 2007 the Surrey Wildlife Trust noted that the river levels fluctuated considerably and that there was increasing erosion of the river banks due to changes in levels. The preferred option for our weirs at both Elstead and High Mill is to enter into negotiation with the local land owners with a view to transferring ownership as part of the Wey Weirs Refurbishment Project. The requirements for fish passage at all structures under WFD will be included as part of these negotiations alongside potential development of the outline designs provided to the parallel Wey Forward Project if funding is received.

9 Appendix 1 Fish Pass Option Presentation

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11 Appendix 2 Minutes of Project Team Meeting

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13 Appendix 3 Fish Pass Prioritisation Paper

14 Appendix 4 Fish Pass Percentage Comparison