An audit of the surface water outfalls in the River Pinn - Outfall Safari

Transcription

1 An audit of the surface water outfalls in the River Pinn - Outfall Safari October 2017 UK & Europe Conservation Programme Zoological Society of London Regent's Park London, NW1 4RY marineandfreshwater@zsl.org s-rivers

2 Acknowledgements This project, funded by Rivers and Wetlands Community Days and the City Bridge Trust, has been delivered in partnership with Thames21 with the support of the Environment Agency and Thames Water. It would not have been possible without the help of all the dedicated volunteers who collected the data. Introduction Misconnected wastewater pipework, cross-connected sewers and combined sewer overflows are a chronic source of pollution in urban rivers. An estimated 3% of properties in Greater London are misconnected (Dunk et al., 2008) sending pollution, via outfalls, into the nearest watercourse. There is currently no systematic surveying of outfalls in rivers to identify sources of pollution and to notify the relevant authorities. The Outfall Safari is a survey method devised to address this evidence gathering and reporting gap. It was created by the Citizen Crane project steering group which consists of staff of Thames Water, Environment Agency (EA), Crane Valley Partnership, Friends of River Crane Environment, Frog Environmental and the Zoological Society of London (ZSL). It was first used on the River Crane in May Aims The aims of the River Pinn Outfall Safari were to: Record and map the dry weather condition behaviour of surface water outfalls in the River Pinn; Assess and rank the impact of the outfalls and report those that are polluting to the Environment Agency and Thames Water; Build evidence on the scale of the problem of polluted surface water outfalls in Greater London; and Recruit more volunteers and further engage existing volunteers in the work of the Pinn and wider Colne Valley Catchment Partnership. 12

3 Method The survey of outfalls was conducted between 25 th July and 15 th September trained volunteers took part in the Outfall Safari. Volunteers were trained at the Kings Café in Ruislip. Training, delivered by ZSL, Thames21 and Thames Water included: An overview of water quality issues in the River Pinn; Information on outfalls and how they become polluted; Information on Thames Water s surface water outfall team; Instruction on how to assess each outfall using the project App and how to upload information to the database; and A health & safety briefing and signing of the risk assessment. During the training, groups of volunteers were assigned lengths of the River Pinn to survey. Further coordination of survey dates and reaches was conducted by the volunteer group on a closed Facebook group set up specifically for the Outfall Safari. Groups of volunteers were free to conduct the survey of their reach when convenient to them, within the survey period, provided there had been no rain for 48 hours prior to survey. A period of 48 hours of no rain is required before any survey work as rainfall and high surface water flows can obscure the negative impacts of outfalls by washing away sewage fungus, discoloured sediments and rag. In total 18.3 km of the River Pinn was surveyed 16 km by volunteers walking along the river banks and 2.3 km in- channel by staff off ZSL, the Environment Agency and Thames 21. The majority of the survey work was conducted from the riverside path (see Figure 1a), with the occasional need to enter the river to properly assess and photograph outfalls. The risk assessment for riverside outfall surveying highlighted the need to assess conditions in the river before entering it and stressed that volunteers should only enter the river channel if the level was lower than Wellington boot depth (c.35cm). During the training volunteers were also shown images of Giant Hogweed (Heracleum mantegazzianum). It was essential that volunteers could identify Hogweed before undertaking any survey work as it is a relatively common plant along the banks of rivers in London and can burn and blister skin if touched. In some reaches of the river where it flows through private land or are inaccessible from the banks, the survey had to be conducted in-channel. More stringent health and safety rules 13

4 applied to in-channel surveys all of which were led by ZSL staff. Waders, stabilising poles and life jackets were used by in-channel survey teams (see Figure 1b). In addition to personal protective equipment (PPE) volunteers took a printed handout, designed to help with ranking the impacts of each outfall, and a smart phone or tablet loaded with a specially created data entry app. b Figure 1- Photos of a, volunteer surveying the River Pinn and, b, an In-channel survey with the Environment Agency ZSL The App For ease of data collection from the river, the volunteers used an app created in Epicollect 5 and Epicollect Beta+ (five.epicollect.net). Created by researchers at Imperial College, Epicollect is free and openly available. Once a project is set up in Epicollect it provides an app for remote data collection and upload, usable on GPS enabled smart phones, and a web portal to access and download the data. The outfall assessment form created in the app consisted of ten questions for volunteers to fill in at each outfall. The questions are taken directly from the form that Thames Water use for assessing the impact of outfalls and are shown in Table 1. 14

5 Table 1 Questions used in the Epicollect app to assess each outfall and their corresponding Impact Score Question Options EA score 1. Volunteer name 2. Date of survey 3. GPS location 4. Photo of the outfall 5. Description of the nearest landmark 6. Which bank is the outfall on (when looking downstream) 7. Ranking of the flow coming out of the outfall a. No Flow b. Trickle c. Low Flow d. Moderate Flow e. High Flow 8. Ranking of the visual impact of the outfall 9. Ranking of the aesthetics of the outfall 10. Other signs of pollution a. No visible effect 0 b. Within 2m of outfall 2 c. Impact 2 to 10m 4 d. Impact 10 to 30m 6 e. Impact greater than 30m 10 a. No odour or visible aesthetics 0 b. Faint smell, slight discolouration 2 c. Mild smell, mild discolouration, small coverage of sewage fungus d. Strong smell, strong discolouration, large coverage of sewage fungus and/ or litter e. Gross smell, gross sewage

6 Conversion of Outfall Assessment to Impact Scores To assist with prioritisation of the outfalls, the Environment Agency provided a method of converting the assessment data to a numeric impact score for each outfall. These scores are shown in the right hand column in Table 1. Reporting Any outfall with an impact score 10, from the options in questions 8 and 9, were reported directly from the river to the Environment Agency s Incident Hotline and Thames Water. Both Thames Water and Environment Agency also received a copy of this report. Data Processing Outfall data were checked to remove double entries and longitude and latitude coordinates were converted to National Grid References using Results The volunteers photographed, located and assessed a total of 208 outfalls. Of this total 47 showed some signs of pollution and scored 0 and of these 32 had a score 4. The details of the outfalls with an impact score of 4 are given in Table 2. Three outfalls were reported to Thames Water and the Environment Agency from the river during the survey. The references for the reports and their identification number in Table 2 are; 1. 13, in Hatch End Playing fields, Thames Water reference and EA reference , upstream from Swakeleys Road bridge, Ickenham, Thames Water reference and EA reference is , at back Woodville Gardens, Ruislip, Thames Water Reference and EA reference A further three outfalls were reported to Thames Water and the Environment Agency on the 4 th and 5 th October 2017; 16

7 4. 31, 20 metres south of Swakeleys Drive, Thames Water reference and EA reference , in the copse wood behind the Broadwalk, Thames Water reference and EA reference , Wood Hall at footbridge, near Lawn Vale, Thames Water reference and EA reference The full 2017 River Pinn Outfall Safari dataset is available from ZSL. Table 2 Details and photos of River Pinn outfalls with an impact score of greater 4 Number Location Details NGR Bank Side Outfall Score Photo 1 50m south of Cowley High Street bridge, opposite Argos right 4 2 Swakeleys Road bridge, Ickenham (near Irwin Close, Ickenham, Uxbridge UB10 8BB right 8 3 Between car parks at M&S on Love Lane right 4 4 Between car parks at M&S on Love Lane right 4 5 Side of M&S- next to Bishops Walk right 6 17

8 6 Bridge Street Gardens (Marsh Rd) left m downstream of upper footbridge from Barrowpoint Avenue left 4 8 Waxwell Crescent left 4 9 Love Lane and Waxwell junction right 4 10 ditch from Ruislip Golf Course left 4 not available 11 railway bridge near Breakspear Road South and Holylake Crescent right 4 not available 12 At the Cannon Brook confluence right 4 not available 13 Hatch End Sports Centre left In the copse wood behind The Broadwalk, Northwood HA6 2XD right Green sace behind Southcote Rise, HA4 7PJ left 4 not available

9 16 Westcote footbridge off Grasmere Avenue 17 Woodville Gardens, Ruislip HA4 7ND right 4 not available left 4 not available 18 Woodville Gardens, Ruislip HA4 7ND, right Between Bridge at start of West End Lane allotments and bridge under Lloyd court, Pinner HA5 1EE Right 4 not available 20 Left hand side. Directly under the bridge on bend in Barnhill, Pinner HA5 2SY Left 8 not available 21 50m downstream of Cheney Street, Pinner HA5 2QW Right 6 22 Long Meadow opposite Case is Altered, Pinner HA5 2QA Right 4 23 High Rd Eastcote, Pinner HA5 2EL - by electricity sub station Left 4 24 Hillingdon Golf Course, Dawe's Rd, Uxbridge UB10 0RS, UK left 4 25 Hillingdon Golf Course,Dawe's Rd, Uxbridge UB10 0RS, UK right 8 19

10 26 Wood hall at footbridge, nr Lawn Vale, Pinner HA5 3EA, UK right Woodlhall Gate ditch nr 619 Uxbridge Rd, Pinner HA5, UK right 6 28 Nr 619 Uxbridge Rd, Pinner HA left 4 29 Paines Ln, Pinner HA5 3DF right 6 30 Nugent's Park, Pinner HA left metres south of Swakeleys Drive, Ickenham, Uxbridge, UB10 8QG right Near footbridge, Park View, HA5 4LJ right 4 not available Discussion Some outfalls pollute intermittently and may not have been detected as a problem during the survey but this report represents an audit of how outfalls, within the surveyed area, were behaving during the survey. Reports from volunteers identified one outfall in particular 20

11 (number 31 in Table 2) that from previous monitoring did not show signs of pollution but at the time of undertaking a survey in September 2017 pollution levels were significant (impact score of 10). Other outfalls could intermittently cause more serious problems than impact scores may suggest depending on what was observed at the time of the outfall safari survey. This outfall safari surveyed 20.6km of the River Pinn and recorded 32 significantly polluting outfalls (score of 4). This is approximately 15% of all outfalls assessed, which is comparable to the proportion of significantly polluting outfalls on other London catchments (Crane, 22% of those assessed; Hogsmill, 21% of those assessed). A higher proportion of polluting outfalls was observed on the Brent catchment (45%). The consistently high number of polluting surface water outfalls that have been reported through the outfall safaris to date demonstrates the likely scale of the problem across London. The findings of this report further support the need to increase efforts to properly address this pollution source which compromises the ecological value of rivers in London. This report outlines the findings of the fourth Outfall Safari conducted in Greater London. Outfall Safaris of the Rivers Ravensbourne and Ingrebourne are planned for autumn 2017, also in partnership with Thames 21. Once these are conducted, ZSL will work with members of the Catchment Partnerships in London to properly analyse Outfall Safari data and make recommendations about the numbers of outfalls that need to be remediated annually to effectively tackle the problem of pollution from outfalls degrading the ecological value of rivers in London. References Dunk, M.J., McMath, S.M., Arikans, J., A new management approach for the remediation of polluted surface water outfalls to improve river water quality. Water Environ. J. 22, Contact details Joe Pecorelli: Project Manager Conservation Programmes joe.pecorelli@zsl.org 21