Manchester Ship Canal: Summary of Known Data and Relevant Information

Final Report

Appendix Document

United Utilities

413687

February 2015

Dr Keith Hendry, Heather Webb, Dr Michael Dobson, Caitlin Riddick

Client: United Utilities

Address: Lingley Mere Business Park

Lingley Green Avenue

Great Sankey

Warrington

WA5 3LP

Project reference: 413687

Date of issue: February 10, 2015

______

Project Director: Dr Keith Hendry

Project Manager: Heather Webb

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APEM Ltd Riverview A17 Embankment Business Park Heaton Mersey Stockport SK4 3GN

Tel: 0161 442 8938 Fax: 0161 432 6083

Registered in England No. 2530851

Report should be cited as:

“APEM (2014). Manchester Ship Canal: Summary of Known Data and Relevant Information. Appendix Document. United Utilities, February 2015 Final”

Report Note:

This is a technical report only. It does not consider or make any statements in relation to legal liability or legal responsibilities. Any statements on allocation or source apportionment are purely factual following the approach set out Appendix IV of this report.

Revision and Amendment Register

Version Date Section(s) Page(s) Summary of Changes Approved Number by

Preparation of draft report for V01 09/01/2015 All All HW client submission

Preparation of final report for All All HW V02 11/02/2015 client submission

Contents

Appendix I Data Availability and Previous Water Quality Reports...... 1

AI.1 Data Availability ...... 1

AI.2 Background to Previous Reports Reviewing the Water Quality of the MSC ...... 9

Appendix II Review of Historic MSC Water Quality Data ...... 11

AII.1 Dissolved Oxygen (DO) ...... 11

AII.2 BOD ...... 19

AII.3 Ammonia...... 32

AII.4 Nutrients (Phosphorus) ...... 37

AII.5 Sediment Oxygen Demand (SOD) ...... 38

AII.6 Sediments ...... 40

Appendix III Algal Blooms ...... 43

Appendix IV Source Apportionment for Factors Influencing Water Quality ...... 47

AIV.1 Method ...... 47

AIV.2 Results ...... 53

AIV.3 Discussion ...... 59

Appendix V Flood Risk ...... 60

AV.1 Introduction ...... 60

AV.2 Sources of Flooding ...... 60

AV.3 Flood Risk Results ...... 62

AV.4 Conclusion ...... 66

List of Figures Figure AI 1 APEM and EA Sampling Sites for BOD and Ammonia - Pound 1 ...... 5 Figure AI 2 APEM and EA Sampling Sites for BOD and Ammonia - Pound 2 ...... 6 Figure AI 3 APEM and EA Sampling Sites for BOD and Ammonia - Pound 3 ...... 7 Figure AI 4 APEM and EA Sampling Sites for BOD and Ammonia - Pound 4 ...... 8

Figure AII 1 Mean annual surface DO (mg/l) in the MSC Pounds. TB = Turning Basin...... 12 Figure AII 2 Minimum surface DO (mg/l) recorded each year in the MSC Pounds TB = Turning Basin...... 12 Figure AII 3 Mean annual bottom water DO (mg/l) in the MSC Pounds. TB = Turning Basin. 13 Figure AII 4 Minimum bottom water DO (mg/l) recorded each year in the MSC Pounds. TB = Turning Basin...... 13 Figure AII 5 Bottom water DO concentrations in the Turning Basin, 3rd June 2013 ...... 14 Figure AII 6 Bottom water DO concentrations in the Turning Basin, 8th July 2013 ...... 14 Figure AII 7 DO at the EA Sonde at Barton, 2014...... 15 Figure AII 8 DO at the EA Sonde at Irlam, 2014...... 16

Figure AII 9 DO at the EA Sonde at Caddishead, 2014...... 16 Figure AII 10 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sonde at Barton, 17th to 18th March 2014...... 17 Figure AII 11 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sonde at at Irlam, 25th May 2014...... 17 Figure AII 12 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 13th and 19th of May 2006...... 18 Figure AII 13 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 29th June and 5th of July 2006...... 18 Figure AII 14 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 8th and 13th August 2006...... 19 Figure AII 15 Mean annual and maximum BOD within the MSC Turning Basin...... 20 Figure AII 16 Mean annual and maximum BOD within the MSC Turning Basin and upstream to Woden Street...... 21 Figure AII 17 Mean annual and maximum BOD within the MSC Turning Basin and upstream to Woden Street during oxygenation/aeration...... 21 Figure AII 18 Maximum BOD concentrations on tributaries into Pound 1...... 22 Figure AII 19 Mean annual and maximum BOD between Mode Wheel and Barton Locks. .... 23 Figure AII 20 Maximum annual BOD sites between Mode Wheel and Barton Locks. Sites upstream of Salford WwTW denoted by dashed lines...... 24 Figure AII 21 Mean annual and maximum BOD between Barton and Irlam Locks (EA data). 25 Figure AII 22 Maximum annual BOD sites between Barton and Irlam Locks...... 25 Figure AII 23 Mean annual and maximum BOD between Irlam and Latchford Locks...... 26 Figure AII 24 Maximum BOD between up- and downstream of Irlam Locks...... 27 Figure AII 25 Maximum BOD concentrations at EA sites within Pound 4...... 28 Figure AII 26 Maximum BOD concentrations in the River Mersey and MSC sites up- and downstream of the Mersey confluence ...... 29 Figure AII 27 Maximum BOD concentrations in the River Glaze and Red Brook compared to the MSC...... 30 Figure AII 28 Maximum BOD concentrations in the River Bollin compared to the MSC...... 31 Figure AII 29 Maximum BOD concentrations in the River Mersey compared to the MSC...... 31 Figure AII 30 Mean, minimum and maximum ammonia concentrations within Pound 1 ...... 32 Figure AII 31 Mean, minimum and maximum ammonia concentrations within Pound 2 ...... 33 Figure AII 32 Maximum ammonia concentrations ...... 34 Figure AII 33 Mean, minimum and maximum ammonia concentrations within Pound 3 ...... 35 Figure AII 34 Mean, minimum and maximum ammonia concentrations in the MSC within Pound 4 ...... 36 Figure AII 35 Maximum ammonia concentrations within Pound 4 ...... 37 Figure AII 36 Mean annual total phosphorus concentrations within the MSC ...... 38 Figure AII 37 SOD measurements from the Turning Basin and MSC. Data labelled as MSC are just denoted as MSC in the relevant source reports...... 39 Figure AII 38 SOD measured throughout the MSC Pounds in 2007 ...... 39 Figure AII 39 SOD measurements at individual sites throughout the MSC ...... 40 Figure AII 40 Metal concentrations within the MSC sediments in 1997 and 2013 ...... 41 Figure AII 41 Metal concentrations within the MSC sediments in 1997 and 2013 ...... 41

Figure AIII 1 Mean surface and bottom water DO levels during the algal bloom in 2010 ...... 46

List of Tables Table AI 1 Available data for the EA monitoring sites between Pomona and Latchford Locks ( = DO, × = BOD, ● = Ammonia). Surface samples only on a typically monthly basis...... 3

Table AIV 1 Flow volumes for each input ...... 48 Table AIV 2 Source of data for source apportionment of inputs from each river. Flow was derived for each river directly. Proportional source of inputs was estimated by using

percentages derived from data on subcatchments within the River Mersey catchment, themselves calculated from UU (2013)...... 49 Table AIV 3 Breakdown of tributary inputs with the Mersey catchment ...... 50 Table AIV 4 Source of data for the inflowing loads from the upstream MSC reach...... 51 Table AIV 5 Source of data for STW loads. Flow data from each STW was considered separately...... 51 Table AIV 6 Summary of source apportionment by the Environment Agency ...... 52 Table AIV 7 Estimated surface water BOD and AOD inputs, highlighting UU contribution. .... 53 Table AIV 8 Summary of source apportionment using the data analysed here ...... 54 Table AIV 9 ...... 55 Table AIV 10 MSC Turning Basin Total Oxygen Demand Model ...... 56 Table AIV 11 ...... 58

Table AV 1 Historic records of flooding from the MSC ...... 61

APEM Scientific Report 413687

Appendix I Data Availability and Previous Water Quality Reports

AI.1 Data Availability

An overview of the available data for the MSC and its major tributaries is given below. As part of the current investigation, these data have been extended using more recent information to create an almost continuous data set of water quality within the various pounds of the MSC and inflowing rivers over the past 40+ years. Maps of the sites from which data have been used in this report are provided in Figure AI 1 to Figure AI 4.

AI.1.1 APEM Water Quality Monitoring

By far the most detailed and extensive water quality data set available in the MSC and Salford Quays comes from APEM, including monitoring contracts with Salford City Council and United Utilities along with ongoing research undertaken by the company over the last 28 years.

At Salford Quays APEM have monitored dissolved oxygen (DO) and temperature profiles within the Inner Basins since 1987. This is conducted on at least a weekly basis, with a more detailed monthly survey which incorporates measurements of BOD, pH, conductivity, Secchi depth, Chlorophyll a, nutrients and ammonia. Suspended solids are measured on a quarterly basis, and phenols, metals and pesticide levels are measured twice yearly. The monitoring sites include two sites in the MSC Turning Basin: Sites 1 (South Bay) and 10 (Central Bay). The sampling programme and site selection allows comparisons to be made between the isolated Inner Basins and the MSC for both control purposes and also to gauge progress and success of the management strategy with the Inner Basins.

APEM have also been commissioned to undertake monitoring in the MSC Turning Basin in the summer (May to September/October) since 2001. This is to assess the effectiveness, and to manage the operation of the oxygenation system (until 2011) and the aeration system (from 2012 onwards). Temperature and DO profiles (1 m resolution) were measured one to three times a week at 29 sites in the MSC from Trafford Road Bridge to Mode Wheel Locks, and a further four sites in and around Pomona docks which serve as control sites upstream of the areas influenced by the oxygen injection/aeration units.

These sampling programs include profile measurements of DO and temperature, thereby allowing the occurrence of bottom water anoxia to be identified.

In recent years however restrictions to the funding available to undertake the monitoring in the MSC Turning Basin have meant that the scope and precision of data collection has significantly reduced. In 2013 no funding was available to monitor the system during an exceptionally warm, dry period in July. It was therefore not possible to determine how the system coped with such conditions. Furthermore these conditions would have allowed the system to be operated to test its effectiveness in raising such low oxygen levels and would have allowed updated performance data to be obtained which could be used for the design of a system for the remainder of the canal. In 2014 monitoring was only undertaken at nine sites within the Turning Basin and at three control sites. This provided only limited data to manage the operation of the system.

As part of the MSC AMP4 water quality investigation, APEM undertook a detailed water quality and ecological survey of the MSC during 2007. The survey programme collected previously unavailable data. For example, DO profile measurements were taken downstream of Mode Wheel Locks, where only surface measurements had previously been taken. A key

February 2015 - Final 1 APEM Scientific Report 413687 aspect of the survey was also to target peak storm events in order to investigate the impact of CSO spills on canal water quality.

APEM has also undertaken water quality monitoring of the MSC at the site of the new Carrington Power Station within Pound 4. In 2009, as part of the feasibility stage of the development APEM, was contracted by Carrington Power Ltd to investigate water quality of the MSC and River Mersey where they meet at the Carrington Site (APEM 2010). Weekly water sampling was undertaken between April 2009 and May 2010 and laboratory analysis carried out for key parameters. The construction company, Duro Felguera Energía, was then required to validate or review the previous data to account for any changes in water quality at the site over the past two years, and commissioned APEM to undertake a programme of surveys to update the data gathered during the previous surveys. Water quality sampling of the MSC within the vicinity of the intake was undertaken every two months from November 2012 until September 2014.

AI.1.2 Environment Agency Water Quality Monitoring

The Environment Agency (EA) conducts two separate monitoring programs on the MSC and tributaries; one by a ‘river monitoring team’ and the other by a ‘marine team’. Data extends back as early as 1976 and encompasses a number of sites from the Irwell down to Latchford Locks (Table AI 1 ). Although many of the sites were temporary, some long term data sets are available from the EA’s compliance monitoring determinands, including DO, BOD, ammonia, nitrate and nitrite. Each of the pounds considered in this investigation is covered by at least one of the EA’s sites. However, the data are for surface sites only, limiting its value in this study primarily because anoxia, a major issue with respect to MSC water quality, is rarely present within 30-50 cm of the water’s surface. Furthermore, data are typically only collected on a monthly basis. There are also only recent data, up to 2014, for 10 of these sites.

In recent years the EA has also deployed continuous water quality monitoring probes (data sondes) capable of continuous monitoring of parameters such as DO, temperature, pH and conductivity at the surface. The data are recorded at 15 minute intervals. Although there are concerns over data sondes, particularly the need for regular calibration, they do provide a valuable insight into water quality behaviour that is difficult to achieve with manual monitoring alone. It is of particular value is demonstrating the extent of short term oxygen flux (supersaturation to anoxia) as a consequence of algal metabolism (photosynthesis and respiration) and the effects of weather conditions. Three data sondes are deployed: upstream of Barton Locks, Upstream of Irlam Locks and at Partington (between Irlam and Latchford Locks).

The EA also monitors the final effluents from Davyhulme, Eccles, Salford and Urmston WwTWs. However, these data are of limited value to the current study and so are not discussed further here.

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Table AI 1 Available data for the EA monitoring sites between Pomona and Latchford Locks ( = DO, × = BOD, ● = Ammonia). Surface samples only on a typically monthly basis.

EA Site Name 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

Pound 1 Upstream Mode Wheel Locks River Irwell at Searchlight Ltd.                                ×   Premises, Water St. (was above × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ● ● ● Woden St. Footbridge) ● ● MSC at Woden Street     × × × × MSC upstream of Pomona  Docks × MSC downstream of Pomona  Docks × MSC at Swing Rail Bridge                  × × × × × × × × × × × × × × × × × Pound 2 Mode Wheel to Barton Locks MSC at Mode Wheel Locks                  Bridge × × × × × × × × × × × × × × ×

MSC below Mode Wheel                × × × × × × × × × × × × × × × ● ● MSC below Barton Bridge                            × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ● ● ● ●

MSC upstream of Barton Locks                × × × × × × × × × × × × × × × ● ● MSC at Barton Locks               × × × × × × × × × × × × × × × ×

Pound 3 Barton to Irlam Locks Old Course Irwell at Boatman ●  ● Pub ● MSC upstream of Irlam Locks              × × × × × × × × × × ● ● MSC at Irlam Locks                                    × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ● ● ● ● ● ● ● ● Pound 4 Irlam to Latchford Locks MSC downstream of Irlam Locks              × × × × × × × × × × × ● ● ● MSC at Cadishead Ferry        × × × × ×

MSC upstream of Lanstar                × × × × × × × × × × × × × × × ● ● ● ● ● ● ● MSC at Warburton Bridge   × ×

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EA Site Name 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

MSC upstream of River Bollin        × × × × × × × MSC upstream of Latchford                        Locks × × × × × × × × × × × × × × × × × × ×

MSC at Latchford Locks                                      × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ● ● ● ● ● ● ● River inputs Pound 1 River Irwell at Blackfriars Bridge    × × × River Irwell near Salford Station           ×   × × × × × × × × × × × ×

River Irk at Red Bank above                               Scotland Weir × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

River Irwell at Foot Bridge at                               Salford University × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

Pound 3 Salteye Brook above Confluence                       ×  with MSC × × × × × × × × × × × × × × × × × × × × × × ● × ● ● ●

Pound 4 River Mersey at Flixton Road                                Bridge × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

Red Brook at Partington Road                                        Bridge × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

River Glaze at Little Woolden                                Hall × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

River Glaze above confluence ● ● ● ● ● ● ● ● with MSC River Bollin Warburton Bridge                                Heatley × × × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

River Mersey at Woolston Weir                             × × × × × × × × × × × × × × × × × × × × × × × × × × × ×

Old Course Irwell PTC Platts ●  ● Brook ● Old Course Irwell PTC Ship    Canal ● ● ● Platts Brook PTC Old Course   ● Irwell ● ●

February 2015 - Final 4 APEM Scientific Report 413687

Figure AI 1 APEM and EA Sampling Sites for BOD and Ammonia - Pound 1

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Figure AI 2 APEM and EA Sampling Sites for BOD and Ammonia - Pound 2

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Figure AI 3 APEM and EA Sampling Sites for BOD and Ammonia - Pound 3

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Figure AI 4 APEM and EA Sampling Sites for BOD and Ammonia - Pound 4

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AI.2 Background to Previous Reports Reviewing the Water Quality of the MSC

AI.2.1 Academic Reviews (1988 - Present)

One of the earliest academic investigations into the water quality of the MSC was by Montgomery (1988), who reviewed the water quality in Manchester Docks before isolation and creation of Salford Quays and found a significant reduction in the pollutant load of the Quays coupled with an improvement in DO. This was compared against water quality in the adjacent upper reaches of the MSC, finding it to be heavily polluted. This work also discussed how a potential for economic redevelopment in the Salford area was previously prevented by poor water quality of the docks. Montgomery’s study marked the beginning of a long period of high quality scientific investigation into Salford Quays and the upper reaches of the MSC.

Following Montgomery’s work, Hendry (1991) provided a detailed investigation into the effects of isolation and artificial mixing in Salford Quays and an insight into water quality improvements of the Quays within the context of other similar systems within the UK. It provided the first investigation of the response of water quality in the Quays to the installation of artificial mixing units (Helixors) and the subsequent effect upon biota. As found by Montgomery (1988), Hendry’s work showed a marked reduction in pollutants of the waters since isolation and demonstrated how the vigorous mixing system installed in the Quays prevent bottom water anoxia.

A major finding from Hendry’s work was in explaining how an increase in algal blooms occurred following isolation. Once isolated the inflow of turbid water ceased and the water became clearer, allowing much greater light penetration which, combined with high levels of nutrients leached from the sediments, led to elevated algal productivity. However, despite this tendency for increased trophic status, the overall changes in water quality were found to be beneficial for biota. After about eight years the excessive algal blooms were brought under control, allowing a balanced and diverse ecosystem to develop. This information will prove valuable in future modelling of ecological development in the MSC following water quality improvements.

Several masters degree projects have since been conducted under the supervision of APEM Ltd, each providing data on the various microbiological and ecological aspects of the MSC. Teesdale (2002) carried out some important work on the spatial variation of sediment oxygen demand (SOD) between Pomona and Mode Wheel locks, finding that SOD was highest within the Turning Basin. This was attributed to particulate deposition in this area due to reduction in flow as the Irwell enters the MSC. Obviously this has important ramifications for the oxygen concentrations in the overlying water, a key issue for the present modelling study.

AI.2.2 APEM Review (1990) in association with Watson Hawksley (now MWH)

APEM (1990a and 1990b) compiled a comprehensive review of historical data available within the MSC Salford Quays, and the input rivers Irwell, Irk and Medlock. These reports drew upon data recorded by the North West River Authority (now part of the EA) and the APEM data archive.

Detailed mass flux analysis revealed that during this time the River Irwell in particular was the major source of organic loading into the MSC, with high concentrations of BOD and ammonia combined with low DO. The report attributed much of the organic pollution found in

February 2015 - Final 9 APEM Scientific Report 413687 the Rivers Irwell, Irk and Medlock to inadequately treated sewage and farm waste1. Localised storm events also led to frequent CSO spill events, particularly in the Rivers Irk and Medlock, that periodically resulted in large volumes of organic pollutants entering the river network. BOD and ammonia from these events entered the MSC where much of the particulate matter would settle (due to slowing of flow) and create an elevated oxygen demand, eventually resulting in total water anoxia in parts of the MSC.

This report also developed water quality models to predict variations in DO in the MSC caused by temperature and velocity and, more crucially, due to SOD. Sediment cores were taken at various sites in the upper MSC and analysed for gas release and oxygen demand exerted by the sediment on the overlying water. The importance of SOD to the overall oxygen budget of the MSC was initially recognised here and followed up by subsequent investigations (e.g. APEM 1999, Teesdale 2002). The report also discussed the bacteriology of the MSC, finding high concentrations of faecal bacteria, rendering the waters unsuitable for water sports use.

The findings of this report, in combination with the studies by Montgomery (1988) and Hendry (1991), provided the foundation for the management strategy in the upper MSC and Salford Quays and gave impetus for the intensive monitoring programs still in place today. They also provide invaluable historical data records that can be used to inform the water quality model created as part of the current MSC monitoring program. The data can be used as a historical marker against which any future improvements can be gauged.

AI.2.3 Harper Review (2000)

A more recent review of water quality in the upper MSC comes from Harper (2000). The report discussed historic water quality data within the context of assessing the Mersey Basin Campaign’s (MBC) target of achieving a River Ecosystem Class of RE4. It provides an important overview of the improvements in ammonia, BOD and DO since data collection began in 1974. Harper discussed many of the pertinent issues relating to the MSC including its storm sewage inflow problems, anthropogenic water usage, changes observed in ecology, and impact of dredging.

The historical data compiled for the report provides an important long term data set for multiple determinands (including BOD, DO, Ammonia and SS) both within each pound of the upper MSC and for the major river inputs.

Of particular importance was the comment by Harper recognising the MSC as the ‘sump’ of the Mersey basin system. The artificial nature of the MSC (depth and vertical walls) meant that it was inevitable that, given the high population density and hence sewage derived load to the MSC, it would not behave as a ‘normal’ river would and absorb the polluting loads. In fact the opposite was anticipated with serious future problems predicted, as indeed has been the case.

Overall the findings of the report show that the condition of the MSC in 2000 was the best it had been since records began. It made some important recommendations to continue its progress of water quality improvement, including improvements to the WwTWs and CSOs in the catchment, developing a more in depth water quality model to understand the water quality processes within the MSC and undertaking detailed ecological surveys.

1 At that time intensive pig farming in the Medlock valley formed a significant contribution to the organic pollution load.

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Appendix II Review of Historic MSC Water Quality Data

AII.1 Dissolved Oxygen (DO)

DO concentrations in the MSC are generally poor below Mode Wheel Locks, away from the influence of artificial oxygen injection in the Turning Basin (Figure AII 1 ). There is a general downstream deterioration in concentrations, with the highest levels reported in the Irwell upstream (Pound 1 on the figures). Minimum concentrations in all Pounds downstream of Trafford Road Bridge have fallen below 1 mg/l on repeated occasions and complete anoxia has been recorded (Figure AII 2 ). The long term dataset does however indicate an improvement in DO concentrations over the data period.

Much of the data from below Mode Wheel Locks consists of surface values of DO only, which have in the past led to false interpretations of the MSC’s condition. Profile measurements are much more meaningful, as the processes occurring immediately above the sediment surface are of arguably greater importance than those nearer the surface of the water column. Records of DO and temperature profiles are available from the APEM archive containing data from intensive monitoring upstream of Mode Wheel Locks. This monitoring is carried out in the summer months to inform management of oxygen injection, and now aeration units, in order to maintain oxygen in the Turning Basin above 4 mg/l. These data indicate very low DO in the mid 1980s with annual means below 2 mg/l in 1985 and 1986 (Figure AII 3 ) and minimum values of complete anoxia (Figure AII 4 ). Concentrations have since improved. Where data are available for the downstream Pounds (2006, 2007, 2012, 2013) these indicate lower annual means than the Turning Basin, which is expected given the influence of the oxygen injection system between 2001 and 2011 and the aeration thereafter.

Low DO can however still develop in the Turning Basin. For example, in 2013 several periods of low DO occurred. In June 2013 DO decreased to below 4 mg/l in North Bay (Figure AII 5 ). This coincided with the presence of raw sewage in the canal and dredging operations at the time of survey. In response to this the Mode Wheel compressor was increased to 24 hour operation and DO concentrations then improved to an average of 6 mg/l on the 5th June, whereas they remained low at the control site at 3.15 mg/l.

Particularly widespread low DO concentrations were recorded on 8th July 2013 (Figure AII 6 ). Bottom water DO at the control site downstream of Mode Wheel Locks was also low on this occasion at 2.98 mg/l. This coincided with a marked increase in water and air temperatures and a period of dry weather and a pollution incident on the River Irwell upstream. Bacterial degradation of the organic matter in the sewage would have been enhanced as the temperature increased and it is likely that this will have contributed to the lower DO concentrations recorded. Monitoring then ceased until 7th August so it was not possible to assess the duration of these low concentrations.

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Figure AII 1 Mean annual surface DO (mg/l) in the MSC Pounds. TB = Turning Basin.

Figure AII 2 Minimum surface DO (mg/l) recorded each year in the MSC Pounds TB = Turning Basin.

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Figure AII 3 Mean annual bottom water DO (mg/l) in the MSC Pounds. TB = Turning Basin.

Figure AII 4 Minimum bottom water DO (mg/l) recorded each year in the MSC Pounds. TB = Turning Basin.

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Figure AII 5 Bottom water DO concentrations in the Turning Basin, 3rd June 2013

Figure AII 6 Bottom water DO concentrations in the Turning Basin, 8th July 2013

The daily mean, minimum and maximum DO saturations in 2014 from the EA continuous monitoring sondes at Barton, Irlam and Caddishead, are presented in Figure AII 7 to Figure

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AII 9 . The sondes are at fixed positions targeted to collect surface measurements only. These data highlight the marked variability in DO across the year along with low DO in spring and summer. Supersaturation (DO>100%) was recorded during the summer months at all three locations.

Oxygen supersaturation during the daytime indicates high primary productivity (from algal blooms or macrophytes). Whilst a high oxygen concentration is not problematic in itself, an oxygen sag of equal magnitude during the night and particularly at dawn can exert stress on organisms, particularly fish. These diurnal fluctuations are illustrated in the data, examples of which are presented in Figure AII 10 to Figure AII 14 . A fish kill event was reported in the MSC on 15th May 2006 as discussed in Section Error! Reference source not found.. The continuous monitoring sonde located at Barton Locks recorded the event (Figure AII 12 ).

Figure AII 7 DO at the EA Sonde at Barton, 2014.

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Figure AII 8 DO at the EA Sonde at Irlam, 2014.

Figure AII 9 DO at the EA Sonde at Caddishead, 2014.

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Figure AII 10 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sonde at Barton, 17th to 18th March 2014.

Figure AII 11 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sonde at at Irlam, 25th May 2014.

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Figure AII 12 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 13th and 19th of May 2006.

Figure AII 13 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 29th June and 5th of July 2006.

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Figure AII 14 Diurnal variations in dissolved oxygen (%) from the EA continuous monitoring sondes between the 8th and 13th August 2006.

AII.2 BOD

Pound 1 Upstream of Mode Wheel Locks

Within the Turning Basin area of the MSC annual mean BOD concentrations have decreased since 2001, coinciding with the commencement of oxygenation within this area (Figure AII 15). Annual mean concentrations exceeded the FFD and WFD standards for most of the period up to 2001 and also marginally above the WFD standard in 2003. Maximum concentrations have however exceeded these standards in all years except in 2009 (5.59 mg/l). However, annual mean concentrations within the Turning Basin have decreased from a maximum of 12.65 mg/l in 1997 to 3.81 mg/l in 2014.

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Figure AII 15 Mean annual and maximum BOD within the MSC Turning Basin.

Upstream of the Turning Basin, from Trafford Road Bridge to Woden Street (where the MSC proper starts) the canal is outside the influence of the oxygenation/aeration system. BOD concentrations within this reach were comparable to the Turning Basin until 1991 when they decreased to within the FFD and WFD standards (Figure AII 16). Concentrations have since continued to decrease from a maximum annual average of 10.69 mg/l in 1980 to 2.32 mg/l in 2012 and have been within both standards since 1993. Maximum concentrations have however exceeded these standards in most years.

Between 1988 and 2001 (when oxygenation of the Turning Basin commenced) BOD concentrations within the Turning Basin were typically higher than in the upstream reach between Trafford Road Bridge and Woden Street (Figure AII 17 ). Since oxygenation was initiated, BOD concentrations within the Turning Basin have decreased. Maximum concentrations do however remain much more elevated in the Turning Basin.

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Figure AII 16 Mean annual and maximum BOD within the MSC Turning Basin and upstream to Woden Street.

Figure AII 17 Mean annual and maximum BOD within the MSC Turning Basin and upstream to Woden Street during oxygenation/aeration.

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Data available from upstream of Woden Street indicate elevated maximum reported values on the Irk and on the Irwell at Salford University (Figure AII 18 ). This is in agreement with previous reports which attribute high organic load entering the MSC to the high population density of the surrounding catchment and significant sewage effluent inputs, particularly from the Irwell (APEM, 2007a). Indeed previous mass balance estimates of the BOD load entering the MSC in the upper reaches indicated that 84% originated from the Irwell (APEM, 2007a). There has however been a marked improvement since 1990, indicating improvement in WwTW discharges to the inflowing rivers.

Figure AII 18 Maximum BOD concentrations on tributaries into Pound 1.

Pound 2 Mode Wheel Locks to Barton Locks

The BOD data for Pound 2 indicates a decreasing trend with a marked decrease since 1993 with the mean annual BOD within FFD and WFD standards since 1993 (Figure AII 19 ). However maximum concentrations have exceeded this in a number of years.

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Figure AII 19 Mean annual and maximum BOD between Mode Wheel and Barton Locks.

Salford WwTW discharges into the upper reaches of this Pound, downstream of the monitoring sites around Mode Wheel Locks. Comparison of the data for these sites with those downstream indicate higher reported maximum concentrations downstream in a several years (1979, 1988, 1992, 1999, 2004 and 2014), which may reflect CSO discharges (Figure AII 20).

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Figure AII 20 Maximum annual BOD sites between Mode Wheel and Barton Locks. Sites upstream of Salford WwTW denoted by dashed lines.

Pound 3 Barton to Irlam Locks

The BOD data for Pound 3 indicates a decreasing trend over the data period (Figure AII 21 ). The mean annual BOD has been within FFD and WFD standards since 1997. However maximum concentrations have exceeded the FFD standard for the majority of the period (exceptions 1991, 2002, 2003, 2009 and 2011) and consistently exceeded the WFD standard.

Comparison of the data from the EA monitoring site at Irlam Locks, and the data collected by Harper just downstream of Barton Locks over the same period, indicate higher concentrations downstream in the Pound at Irlam (Figure AII 22 ). This could be due to additional BOD loads from Salteye Brook and/or Bent Lanes Brook which flow into the Pound, or could reflect the transport, and subsequent accumulation of, organic matter in the downstream reaches whilst the locks are closed and flow out of the pound reduced.

Salteye Brook enters the MSC just downstream of Barton Locks and has an input from Eccles WwTW. BOD concentrations are higher in the Brook for the majority of the data period (Figure AII 22 ), indicating a high BOD load from the Brook.

The Davyhulme WwTW has a discharge point immediately downstream of Barton Locks. Comparison of the data from the EA location at Barton Locks (within Pound 2) with that downstream collected by Harper does not indicate an apparent effect of this discharge on BOD concentrations, with Harper reporting lower concentrations.

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Figure AII 21 Mean annual and maximum BOD between Barton and Irlam Locks (EA data).

Figure AII 22 Maximum annual BOD sites between Barton and Irlam Locks.

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Pound 4 Irlam to Latchford Locks

BOD data for Pound 4 indicate relatively stable concentrations since 1978 with mean annual concentrations consistently within FFD and WFD standards for the majority of the data period (Figure AII 23 ). Maximum concentrations have however increased since the 1990s and consistently exceeded the FFD and WFD standards in most years since 1993.

Figure AII 23 Mean annual and maximum BOD between Irlam and Latchford Locks.

Urmston WwTW discharge is located immediately downstream of Irlam Locks. Comparison of the data from the EA locations at Irlam Locks (in Pound 3) and the site downstream of the Locks and discharge indicate no apparent effect of the discharge on BOD downstream in the canal.

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Figure AII 24 Maximum BOD between up- and downstream of Irlam Locks.

When measured concurrently at sites upstream and downstream within the Pound, BOD concentrations were typically highest downstream within the Pound at Latchford Locks until 2007 (Figure AII 25 ). This most likely reflects the transport of and subsequent accumulation of organic matter in the downstream reaches. Since 2007 higher concentrations were reported downstream of Irlam Locks and upstream of Lanstar.

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Figure AII 25 Maximum BOD concentrations at EA sites within Pound 4

The River Mersey enters the MSC approximately 0.5 km downstream of Irlam Locks. Comparison of data from upstream and downstream of the confluence indicates marginally higher maximum concentrations below the confluence at Lanstar compared to d/s Irlam Locks on most sampling occasions between 2000 and 2010 (Figure AII 26 ). The data from the Carrington site, which is immediately downstream of the confluence, indicates much higher maximum concentrations. The highest concentration of 45 mg/l was reported during a prolonged period of high flows. However this result does seem to be an outlier compared to other data collected from this site, particularly the 2009 results which were collected during storm events. Actual concentrations on the Mersey at Flixton Road Bridge were either lower or comparable to that reported upstream in the canal. The data from Sites 8 and K do however indicate lower concentrations at these sites compared to upstream (and also at Lanstar).

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Figure AII 26 Maximum BOD concentrations in the River Mersey and MSC sites up- and downstream of the Mersey confluence

Glaze Brook and Red Brook enter the MSC downstream of Lanstar. There are EA monitoring sites on both brooks which indicate markedly higher BOD concentrations than those in the canal downstream (Figure AII 27 ).

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Figure AII 27 Maximum BOD concentrations in the River Glaze and Red Brook compared to the MSC.

BOD concentrations on the River Bollin are high compared to sites up- and downstream of the confluence on the canal (Figure AII 28 ).

Concentrations on the Mersey, as it leaves the MSC, were also elevated compared to the canal until the late 1990s (Figure AII 29 ). Concentrations since then were comparable to those reported in the canal both up- and downstream of the confluence.

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Figure AII 28 Maximum BOD concentrations in the River Bollin compared to the MSC.

Figure AII 29 Maximum BOD concentrations in the River Mersey compared to the MSC.

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AII.3 Ammonia

Pound 1 Upstream of Mode Wheel Locks

Overall there has been a decrease in ammonia concentrations within the Turning Basin since 1985, and particularly since 2008 (Figure AII 30 ). Annual mean ammonia concentrations within the Turning Basin consistently exceeded the FFD guideline level over the entire data period. The mandatory level was exceeded between 1985 and 2005 and in 2007. Maximum concentrations did however also exceed the mandatory level in all years except 2009, 2011 and 2014. The elevated concentration of 93.55 mg/l was reported at Site 1 within South Bay in May 1987.

In relation to the WFD, the annual mean for the Turning Basin exceeded the standard on all occasions except in 2009, 2011, 2012 and 2014. Based on an annual mean of 0.36 mg/l in 2014 the MSC would be classed as Good status for this element. Status in 2013 would however have been Moderate.

Data for upstream of Trafford Road Bridge are limited to the period 2007 to 2014. Aside from a slight increase in 2013, annual concentrations have decreased from an average of 1.5 mg/l in 2007 to 0.4 mg/l in 2014. Annual mean concentrations were consistently higher than the FFD guideline level and the mandatory level in 2007. Maximum concentrations exceeded the mandatory in 2007, 2008 and 2013. The WFD standard for Good status was exceeded in 2007, 2008, and 2013 with the current annual mean of 0.38 mg/l indicative of Good status.

No data were available for the River Irwell upstream of Woden Street to assess the impact of this on loads within the canal. There are however known significant industrial sources in this area, for example Magnesium Elektron on the River Irwell. The EA supplied limited data for the monitoring they undertake at this site which indicated elevated ammonia concentrations of 1.95 mg/l in November 2013 and 3.04 mg/l on October 2014.

Figure AII 30 Mean, minimum and maximum ammonia concentrations within Pound 1

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Pound 2 Mode Wheel Locks to Barton Locks

Ammonia data for Pound 2 is limited to the period 2007 to 2012. These data do however indicate an improvement from an annual average of 1.8 mg/l in 2007 to 0.5 mg/l in 2012 (Figure AII 31 ). Annual mean concentrations were consistently higher than the FFD guideline level over the entire data period; however the mandatory level was only exceeded in 2007 and 2008. Maximum concentrations exceeded the mandatory level in all years except 2012.

In relation to the WFD the standard for Good status was exceeded until 2012, with annual mean concentrations indicative of Poor (2007/08) and Moderate (2009/10) status. The annual mean of 0.53 mg/l in 2012 is indicative of Good status.

The data from 2007 indicate a possible effect of the Salford WwTW discharge on ammonia concentrations in the canal downstream, with marginally lower concentrations reported upstream (Figure AII 32 ). The data are however extremely limited.

The much higher ammonia values reported by APEM at Site 4 and Site 5 may reflect differences in sampling approach by APEM and the EA. The EA do sometimes store samples for up to 48 hours prior to analysis which results in a reduction in the ammonia present in the samples. In contrast APEM samples are analysed within 3 hours of sample collection according to the standard method (M.E.W.A.M., The Determination of Ammonium in Water, 1981).

Figure AII 31 Mean, minimum and maximum ammonia concentrations within Pound 2

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Figure AII 32 Maximum ammonia concentrations

Pound 3 Barton to Irlam Locks

Ammonia data for Pound 3 are available from 2007 to 2014, and indicates a decrease in concentrations between 2007 and 2008, relatively stable levels until 2012 and then an increase in 2013 and 2014 (Figure AII 33 ). Annual mean ammonia concentrations were consistently higher than the FFD guideline level over the entire data period; however the mandatory level of was only exceeded in 2007 and 2013 and 2014. Maximum concentrations exceeded the mandatory level in all years.

In relation to the WFD standards, the annual mean concentrations indicate an improvement from Poor status in 2007 to Moderate status from 2008 to 2012 but then a deterioration to Poor status again in 2013 and 2014.

Salteye Brook enters the MSC just downstream of Barton Locks and has an input from Eccles WwTW. Ammonia concentrations in the Brook are higher than in the MSC (Figure AII 33 ), indicating a high ammonia load from the Brook.

There are insufficient data to assess confidently the potential effect of the Davyhulme WwTW discharge on ammonia concentrations within the MSC. This is because there is no monitoring site downstream of the WwTW discharge but upstream of the confluence with Salteye Brook to separate the effects of these two inputs on concentrations within the canal downstream.

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Figure AII 33 Mean, minimum and maximum ammonia concentrations within Pound 3

Pound 4 Irlam to Latchford Locks

Ammonia data for Pound 4 is available from 2007 to 2014 which, in common with the results from Pound 3, indicates a decrease in concentrations between 2007 and 2008, relatively stable levels until 2012 and then an increase in 2013 (Figure AII 34 ). Annual mean ammonia concentrations were consistently higher than the FFD guideline level over the entire data period. However the mandatory level was only exceeded in 2007 and 2013. Maximum concentrations exceeded the mandatory level in all years except 2008 and 2011.

The annual mean exceeded the WFD boundary for Good status in all years except 2008 and 2011. Status improved from Poor in 2007 to Good in 2008, Moderate on 2009 and 2010, Good in 2011 and Moderate from 2012.

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Figure AII 34 Mean, minimum and maximum ammonia concentrations in the MSC within Pound 4

Ammonia data are also available from Platts Brook which enters the MSC at the same point, but on the opposite bank, to the River Mersey in the upper area of the pound. Average concentrations on the Brook were either higher or comparable to that reported in the canal (Figure AII 35 ). The data from the site d/s of Irlam Locks, which is upstream of the influence of Platts Brook, indicates higher concentrations. There are no ammonia data available for the River Mersey to assess its contribution.

The River Glaze/Glaze Brook enters the Pound downstream of Lanstar. The EA have collected data from a location above the confluence with the MSC which indicates lower annual average concentrations on the Glaze compared to the canal (Figure AII 35 ).

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Figure AII 35 Maximum ammonia concentrations within Pound 4

AII.4 Nutrients (Phosphorus) Data are available for total phosphorus and orthophosphate. The values of total phosphorus are of greatest importance as they describe the complete pool of phosphorus available for algal growth. Estimates of available phosphorus based solely on orthophosphate measurements are therefore an underestimate of the total phosphorus available for algal uptake (e.g. some data, including from the EA uses filtered samples. In such samples, algal cells containing phosphorous are removed but may contain much of the available phosphorous).

The data indicate that phosphorus concentrations in the Turning Basin have decreased since the 1980s to an annual mean of 260 µg/l in 2014 (Figure AII 36 ). Concentrations upstream on the Irwell and at Site 1 upstream of Woden Street were comparable with those reported in the Turning Basin. To put these figures into perspective, for effective control, concentrations need to be below 25 µg/l, preferably below 15 µg/l.

Data for Pounds 2-4 are limited but indicate concentrations comparable to that reported in the Turning Basin in Pound 2, and higher concentrations in Pounds 3 and 4. The latest data from Pound 4 (2012-2014) are mostly from APEM’s monitoring of the Carrington site which indicate a one off elevated concentration of 5000 µg/l in November 2012. This site is immediately downstream of the River Mersey and this elevated concentration coincided with a prolonged period of high flows on the river. Data from the EA site at Flixton Road Bridge indicate higher concentrations here than on the canal which could suggest phosphorus input from the river.

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Figure AII 36 Mean annual total phosphorus concentrations within the MSC

AII.5 Sediment Oxygen Demand (SOD) Sediment oxygen demand (SOD) is a measure of the rate at which oxygen in the water overlying the sediment is used up by biological activity within the sediment. This is relevant because the rate of oxygen depletion at or near the sediment surface determines the time required for anoxic conditions to develop in bottom waters.

APEM has developed a dedicated chamber to take in situ measurements of SOD which has provided invaluable data for water quality modelling and system design. The SOD chamber is lowered onto the bottom of the water body, thereby isolating a volume of water above a known area of sediment. Attached to the chamber is a Hydrolab multi-parameter water quality probe together with a small impellor mixer to ensure that low oxygen ‘dead zones’ are not created within the chamber. With the water and sediments in isolation, the change in DO within the chamber is then recorded over a one hour period and the oxygen demand assessed directly.

SOD has been measured on a number of occasions in the MSC. Figures for the Turning Basin show an improvement with SOD values ranging from 905 to 2,941 mg m-2 hr in 1995, 1996 and 1998 down to a range of between 163 and 1,611 mg m-2 hr in 2012 (Figure AII 37 ). There are less data for the downstream Pounds being limited to surveys undertaken in 2007 (Figure AII 38 ). These data indicate SOD ranging from 272 mg m-2 hr in Pound 3 to 391 mg m-2 hr in Pound 4. Results were however highly variable both spatially and temporally throughout the MSC (Figure AII 39 ).

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Figure AII 37 SOD measurements from the Turning Basin and MSC. Data labelled as MSC are just denoted as MSC in the relevant source reports.

Figure AII 38 SOD measured throughout the MSC Pounds in 2007

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Figure AII 39 SOD measurements at individual sites throughout the MSC

AII.6 Sediments

Recent sediment quality data is limited to a just a few of surveys undertaken by APEM although some historic information does exist, primarily via Masters Student Theses on placement with APEM from Manchester University.

Historical data on heavy metal contamination of the sediments of the MSC is available from an M.Sc study undertaken by Critchley (1998) who examined the levels of heavy metals in sediments in the lower reaches of the River Irwell. Burgess (1999) also collected sediment core samples from two locations within the Turning Basin of the MSC near the Lowry Outlet Mall in 1998.

Most recently, in 2013, APEM have undertaken sediment surveys for Salford City Council to support the proposals for a water taxi connecting Central Manchester with Salford Quays via the lower River Irwell and Upper Manchester Ship Canal Turning Basin. Sediment samples were collected throughout this reach. The sediment contaminant data indicate that in most survey zones, heavy metals, (excluding mercury), were present at concentrations above the threshold levels at which adverse biological effects may occur. Heavy metal concentrations peaked around Pomona Docks where levels of arsenic, chromium, copper, lead and zinc were recorded above the probable effect level i.e. the level above which adverse effects are expected to occur frequently. Zinc and lead were also recorded above the probable effect level in the Turning Basin. The results indicate an increase in heavy metal contaminant levels with distance downstream with concentrations being most elevated by Pomona Docks.

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Figure AII 40 presents sediment metal concentration data from the upper reaches of the MSC/lower Irwell. The data are from Critchley’s survey site at Cornbrook in 1997 and those collected in the upper reaches of the canal as part of the water taxi project in 2013. This indicates much lower concentrations of all metals in 2013 (Figure AII 40 ).

Figure AII 40 Metal concentrations within the MSC sediments in 1997 and 2013

Similarly, comparison of the data 1998 data from Burgess (1999) with the 2013 data indicate reduced concentrations of lead, however zinc concentrations appear to have increased (Figure AII 41 ).

Figure AII 41 Metal concentrations within the MSC sediments in 1997 and 2013

Data from 1998 are available from the surface and bottom of a sediment core as Burgess (1999) undertook vertical profiles of the sediment to map metal distributions. This has not been repeated since. In 2013, whilst a core of the same depth of sediment was taken, this was combined for analysis of just one single composite sample for each site. More recent

February 2015 - Final 41 APEM Scientific Report 413687 data on the vertical distribution of metals in the sediment would have allowed an assessment of the extent of re-working of the sediments to be made.

Nevertheless the data, such as it is, presents a picture of a generally improving situation over the past 15 years or so, albeit that the levels of metal contamination are still considered unacceptably high. The significance of this to the MSC aeration project is that construction methods must take into account the contamination levels in the sediment with a view to minimizing disturbance. Construction techniques that involve sediment removal will incur substantial disposal costs because of the nature and level of contamination present.

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Appendix III Algal Blooms

Phytoplankton are planktonic algae living in the water column and are the main primary producers in most aquatic environments. They provide food for zooplankton which in turn provide food for larger invertebrates and fish, therefore forming an essential base to the food chain. Under suitable conditions populations of these algae can however grow to nuisance levels, potentially causing a number of problems by affecting the transparency, DO, and pH of the water column, with subsequent effects on other biota e.g. fish. Furthermore, blooms, and the breakdown products, of certain types of phytoplankton (cyanobacteria/blue-green algae) can be toxic to fish, birds, and mammals.

Since the mid-1980s, a general upward trend has been observed in the abundance of phytoplankton within MSC waters. Historically, conditions within the MSC were not ideal for algal growth despite the very high phosphorus levels, in particular the high turbidity which prevented light penetration into the water column and restricted growth. It was however predicted that with reductions in suspended solids following the AMP investments by United Utilities, together with the high nutrient concentrations, that conditions could become suitable for the development of potentially substantial phytoplankton blooms. Indeed in mid May 2010 a phytoplankton bloom (hereafter referred to as an algal bloom) developed within the Turning Basin. Surface bubbling (supersaturated oxygen) was observed at most sites on 19th May with an algal bloom then developing from 20th to 23rd May (Plate AIII.1a-d). Die back of the bloom was then observed around 24th May (Plate AIII.1e).

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a) b)

c) d)

e)

Plate AIII.1 Algal bloom within surface waters of the MSC between 20th to 24th May 2010 (a-e).

The majority of algae were identified as rapidly growing chlorophyte flagellates of the genus Chlamydomonas (Plate AIII.2). Chlamydomonas spp tend to form blooms and dominate surface waters during periods of heavy organic contamination, with occasional late spring blooms occurring with prolonged day length and increased temperatures. A significant increase in water temperature prior to the bloom was therefore likely to have led to its formation.

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Plate AIII.2 Unicellular flagellate Chlamydomonas sp. dominated algal assemblages during the May 2010 algal bloom.

Algal growth was particularly prolific at the downstream sites within the Turning Basin near Mode Wheel Locks and within sheltered sites where algal cells and surface scum were seen to accumulate. This is to be expected as buoyant cells or colonies accumulate at the surface of the water and are then driven by light winds and currents to leeward areas.

During the bloom DO levels in surface waters increased significantly to a mean of 21.62 mg/l (~216%) on 21st May with values at individual sites ranging from 14.68 to 26.46 mg/l (~265%) (Figure AIII 1 ). Such supersaturation is typical of algal blooms whereby the algae photosynthesise during the day producing oxygen. Problems occur at night, however, as the algae respire and use up this oxygen which can often lead to periods of anoxia. Sudden population die back can also lead to anoxic conditions through decomposition of dead cells (which contribute to the BOD of the water column in much the same way as a pollution incident).

It was therefore recommended that the oxygen system be turned on during this period as this would help to alleviate oxygen sags occurring during the night and could provide oxygen to supply the demand generated during the die back of the bloom. Unfortunately the oxygen system did not become operational until 25th May, after the bloom had started to die back and after anoxic conditions were recorded at the two sites nearest Mode Wheel Locks. Nevertheless, the oxygen system did then help alleviate the problems of low DO associated with the bloom die back, as indicated in Figure AIII 1 by the slight increase in DO recorded from 26th May. DO levels after this initial increase then stabilised between 4 and 7 mg/l.

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Bottom water Surface water Oxygen off Oxygen on 30

Bloom period

25

20

15 Mean DO (mg/l)

10

5

0

04-May 05-May 06-May 07-May 08-May 09-May 10-May 11-May 12-May 13-May 14-May 15-May 16-May 17-May 18-May 19-May 20-May 21-May 22-May 23-May 24-May 25-May 26-May 27-May 28-May 29-May 30-May 31-May 01-Jun 02-Jun 03-Jun 04-Jun 05-Jun 06-Jun 07-Jun 08-Jun 09-Jun 10-Jun 11-Jun 12-Jun 13-Jun 14-Jun 15-Jun 16-Jun

Figure AIII 1 Mean surface and bottom water DO levels during the algal bloom in 2010

In addition to having effects on DO, photosynthesis of the algae present also directly affects the pH by altering the carbon dioxide/hydrogen carbonate balance, with increased photosynthesis resulting in a raised pH, which in turn leads to more alkaline conditions.

The pH values recorded in surface waters during the bloom ranged from 8.17 to 9.31 within the Turning Basin. The bloom was less prolific in Pomona Dock and this resulted in marginally lower pH values of 7.58 to 8.90. Concentrations of pH can affect the behaviour of several important water quality parameters, in particular, the ionisation status of ammonia and its subsequent toxicity to fish; a more alkaline pH allows for a greater proportion of the total ammonia to exist as the more toxic un-ionised form. In addition, pH variations have serious direct implications for fish. The EC Freshwater Fish Directive (78/659/EEC) states that pH levels must fall within the range of pH 6 to 9. The values recorded during the bloom period were above this range at several sites on 23rd May bearing in mind the pH scale is logarithmic. This implies an increased risk of fish mortality during this period, although no such incidents were observed on this occasion.

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Appendix IV Source Apportionment for Factors Influencing Water Quality

A source apportionment was carried out to determine the key sources of oxygen demand in the MSC. A summary of the method and key results of this exercise is given below. AIV.1 Method

General

The source apportionment is designed to give a high level indication of inputs to the MSC as a whole, and therefore no attempt at this stage was made to look at the individual pounds separately. All known inputs were identified as follows:  Inflowing rivers.  UU consented discharges - continuous (WwTWs).  UU CSO consents.  Other consented discharges. The following inputs were calculated or estimated:  Ammonia (N) loading, kg/day, converted to ammoniacal oxygen demand (AOD, kg/day) by multiplying by 4.57.  BOD loading, kg/day.  SOD loading, kg/day. These were determined from data provided by the EA or previously collected by APEM, as described in the sections above.

Inflowing rivers

Mean daily flow measurements (m3/day) were taken from the relevant EA gauging station, where available. Estimates of relative proportions of inputs from WwTWs, CSOs, SWOs and trade effluent were determined from data provided for the River Mersey catchment upstream of the MSC in United Utilities (2013). This document provides modelled predictions for river inputs in 2034; it includes actual and modelled data for the 17 large WwTWs in the catchment, while discharges from CSOs and SWOs are modelled predictions only. Therefore, as the data were being used to determine relative proportions of ammonia and BOD derived from the catchment, modelled data were used throughout. SWO predictions included assumed concentrations of ammonium and BOD, whereas CSO predictions included only anticipated water volumes; therefore, to calculate their estimated loading contribution, values of 1.45 mg/l NH4-N and 11 mg/l BOD were derived from Ellis (1991). The ammonium values presented by UU (2013) were stated as “ammonia” in the WwTW table and “NH4” in the SWO table, and it was assumed therefore that they were NH4 figures and were converted to NH4-N by multiplying by 0.776.

Mean flow was determined using the most recent data available (from 2009 to present). Where there were insufficient flow data after 2009, mean flow was calculated from data no earlier than 2004. In the case that EA flow data were not available, mean annual flow was derived from the National River Flow Archive (NRFA, CEH) or estimated by using flow data from a river with an equivalent sized catchment. Loading was then calculated from mean flow and corresponding Ammonia (N) and BOD concentrations, using data from the most downstream site (nearest to the MSC). If the most downstream site had insufficient data from 2009, data was derived from the next upstream site. Where insufficient data were

February 2015 - Final 47 APEM Scientific Report 413687 available since 2009, mean concentrations were calculated from data no earlier than 2004. Flow volumes from each input are summarised in Table AIV 1.

Table AIV 1 Flow volumes for each input

Reach Input Type No. Mean Volume StDev % Volume data (m3/day) Volume points (m3/day) 1 R. Irwell & R. Irk River 2140 1553180.78 1596449.26 36.26 1 Rochdale Canal & R. Medlock River 1 69984.00 - 1.63 1 Corn Brook River 2140 171764.29 122424.91 4.01 2 MSC MSC - 1623164.78 - - 2 Salford STW STW 11 56419.20 12995.79 1.32 2 Eccles STW STW 9 36720.00 13219.27 0.86 3 MSC MSC - 1623164.78 - - 3 Salteye Brook River 1 25833.60 - 0.60 3 Davyhulme STW STW 137 347301.25 148998.02 8.11 4 MSC MSC - 1623164.78 - - 4 R. Mersey River 2140 1183729.26 1131736.22 27.63 4 R. Glaze River 2131 250341.71 254178.33 5.84 4 Red Brook River 2140 39479.27 33707.58 0.92 4 Marsh Brook River 2140 39479.27 33707.58 0.92 4 R. Bollin River 2140 307653.20 278803.80 7.18 4 Sow Brook River 2140 39479.27 33707.58 0.92 4 Urmston STW STW 2 160000.00 128693.43 3.74 4 Northbank STW STW 9 448.08 261.76 0.01 4 Partington STW STW 9 1792.32 1047.06 0.04 Total 1 4283605.5

As these data were only available for the River Mersey catchment, estimates were made of inputs from other rivers in the following way. Each river was compared qualitatively with respect to degree of urbanisation and industry to the tributaries within the Mersey catchment, and the closest match was used as an indicator of relative importance of different sources of inputs (WwTWs, CSOs, SWOs). Using these proportional values, the actual calculated load was allocated in appropriate proportions to the various sources. The tributaries used for each river are shown in Table AIV 2 and the breakdown of tributary inputs with the Mersey catchment is provided in Table AIV 3.

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Table AIV 2 Source of data for source apportionment of inputs from each river. Flow was derived for each river directly. Proportional source of inputs was estimated by using percentages derived from data on subcatchments within the River Mersey catchment, themselves calculated from UU (2013).

Reach River Source of flow data Source of Source concentration data apportionment percentages based on:

1 River Irwell & Adelphi Weir Upstream APEM - Site 1 River Tame River Irk & Collyhurst Weir 1 Rochdale Canal River Medlock at River Irwell @ River Goyt (minus & River Medlock London Road Searchlight Ltd WwTW input) premises 1 Corn Brook Collyhurst Weir * Corn Brook above Micker Brook Confluence with MSC 3 Salteye Brook Worsley Brook at Salteye Brook Micker Brook Eccles 4 River Mersey Ashton Weir River Mersey at Flixton N/A Road Bridge **

4 River Glaze Little Woolden Hall River Glaze above River Tame Ultrasonic confluence with MSC 4 Red Brook Partington Red Brook at Micker Brook Partington Rd Bridge 4 Marsh Brook Partington * Marsh Brook at Hollins Micker Brook Green ** 4 River Bollin Bollington Mill River Bollin at River Goyt Warbuton Bridge Heatley 4 Sow Brook Partington * Sow Brook d/s of Lymm River Goyt Dam * Estimated flow by using data from a river with an equivalent sized catchment **Mean concentration data estimated using data from an equivalent sized catchment

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Table AIV 3 Breakdown of tributary inputs with the Mersey catchment

Reach Input Type N Mean StDev Mean STW - CSO - SWO - Trade Diffuse Atmospheric BOD BOD BOD mean mean mean effluent river inputs 3 (mg/l) (mg/l) Load (kg/day) (kg/day) (kg/day) - mean inputs (kg/day) 1 1 1 (kg/day) 2 1 1 R. Irwell & R. Irk River 67 3.33 1.65 5171.86 4109.84 400.61 106.34 451.63 103.44 0.00 1 Rochdale Canal & R. Medlock River 35 3.11 1.79 217.51 172.85 16.85 4.47 18.99 4.35 0.00 1 Corn Brook River 36 2.77 2.44 475.60 0.00 183.64 282.45 0.00 9.51 0.00 2 MSC MSC 58 2.54 0.94 4122.84 ------2 Salford STW STW 205 10.43 4.95 588.64 ------2 Eccles STW STW 199 10.74 4.44 394.22 ------3 MSC MSC 55 2.88 1.15 4672.53 ------3 Salteye Brook River 32 8.30 3.44 214.51 0.00 82.83 127.39 0.00 4.29 0.00 3 Davyhulme STW STW 188 6.89 4.19 2392.81 ------4 MSC MSC 48 3.03 1.39 4915.48 ------4 R. Mersey River 67 3.33 1.65 3941.64 3450.37 248.12 71.55 92.76 78.83 0.00 4 R. Glaze River 30 3.40 1.62 851.08 676.31 65.92 17.50 74.32 17.02 0.00 4 Red Brook River 63 3.38 2.29 133.31 0.00 51.47 79.17 0.00 2.67 0.00 4 Marsh Brook River 63 3.38 2.29 133.31 0.00 51.47 79.17 0.00 2.67 0.00 4 R. Bollin River 63 3.38 2.29 1038.84 909.46 62.65 45.96 0.00 20.78 0.00 4 Sow Brook River 63 3.38 2.29 133.31 116.71 8.04 5.90 0.00 2.67 0.00 4 Urmston STW STW 131 14.63 6.85 2340.64 ------4 Northbank STW STW 61 6.90 4.45 3.09 ------4 Partington STW STW 87 8.89 4.00 15.93 ------Total 4 18046.30 9435.53 1171.60 819.90 637.71 246.22 0.00

Notes: 1 Based on 98% river point source. 2 Based on 2% diffuse river source. 3 Based on 0% atmospheric source. 4 Total does not include MSC

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Trade effluent inputs were estimated from data available for two specific sites: Magnesium Elektron (Swinton) on the River Irwell, for which ammonium (N) data were provided by the EA, and Botany Bay Bleachworks (Kruger Ltd) on the River Goyt, for which data were provided in United Utilities (2013). It was assumed that evaporation within the MSC is minimal and that it is sealed effectively against groundwater exchange. There are no rivers flowing out of the canal, except the River Mersey in Pound 4, therefore it was also assumed there was no loading loss due to outflowing tributaries. For each upstream input from the canal, mean flow was calculated as a sum of that measured individually in the River Irwell, River Irk and River Medlock. Loading from the upstream reach was then calculated from mean summed flow of the MSC and the corresponding Ammonia (N) and BOD concentrations measured at the most downstream site in the previous reach (Table AIV 4 ).

Table AIV 4 Source of data for the inflowing loads from the upstream MSC reach.

Reach Source of flow data Source of concentration data 2 Adelphi Weir Upstream & Collyhurst Manchester Ship Canal below Mode Weir & River Medlock at London Road Wheel 3 Adelphi Weir Upstream & Collyhurst Manchester Ship Canal U/S Barton Weir & River Medlock at London Road Locks 4 Adelphi Weir Upstream & Collyhurst Manchester Ship Canal at Irlam Locks Weir & River Medlock at London Road

WwTW discharges, direct

The mean flow for each WwTW that discharges directly into the MSC was derived from direct EA measurements of the WwTW effluent (Table AIV 5 ). Flow measurements were available as an instant rate (l/s or Ml/day), and converted appropriately. Mean flow was determined using the most recent data available (from 2009 to present). Where there were insufficient flow data after 2009, mean flow was calculated from data after 2004. Effluent flow data were unavailable for Northbank WwTW, and therefore the mean flow was assumed to be one quarter of that for Partington WwTW. Loading was then calculated from mean flow and corresponding ammonia (N) and BOD concentrations from EA measurements of the final effluents.

Table AIV 5 Source of data for STW loads. Flow data from each STW was considered separately.

Reach STW Source of flow data Source of concentration data 2 Salford STW Salford STW final effluent Salford STW final effluent 2 Eccles STW Eccles STW final effluent Eccles STW final effluent 3 Davyhulme STW Davyhulme STW final Davyhulme STW final effluent effluent 4 Urmston STW Urmston STW final effluent Urmston STW final effluent 4 Northbank STW Partington STW final Northbank STW final effluent effluent, Stage 3 4 Partington STW Partington STW final Partington STW final effluent, Stage 3 effluent, Stage 3

Sediment oxygen demand

SOD was determined from measurements taken by APEM from the MSC Turning Basin in March-October 2012, and in Pounds 2-4 in alternate months from January to November

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2007 and again in February 2013. These figures, in turn were incorporated into APEM’s Mass Flux models, developed over a number of years specifically for the MSC Oxygenation & Aeration studies.

Calculation of oxygen demand

The total oxygen demand was calculated as the sum of BOD, SOD and AOD. Calculations were based on mean values for each of these, and therefore do not take into account seasonal differences or differences among the four MSC pounds. Source apportionment Categories for source apportionment (SA) were derived from those produced by the EA in its original Source Apportionment document as provided to UU (see Table AIV 6 for summary table from the EA). Permitted sewage discharge contribution was calculated as the sum of direct WwTW inputs into the MSC, plus inputs from WwTWs and CSOs into tributaries. Very view CSOs discharging directly into the MSC were identified and so their input is considered insignificant. These are considered to originate from UU activities. Physical structure and sediment were combined, as they are closely interconnected, because sediment retention at the level observed would not occur in the absence of the canal structure. Sediment input was determined from APEM’s measurements of SOD; to this was added an arbitrary figure for physical structure derived from Table AIV 6 . These are considered not to be a consequence of UU activities. Diffuse inputs in this case are derived from the sum of SWO inputs and a value for diffuse catchment runoff. The diffuse runoff was derived from arbitrary figures: they were assumed to account for 2% of BOD input and 1% of ammonium input (based on evidence derived from APEM’s diffuse urban pollution studies including a recent (October 2014) wet weather walkover survey of Micker Brook). Atmospheric inputs were assumed to account for 0%. SWOs are assumed to be mainly road drains and urban surface water drains that are not connected to the sewerage system. These are considered not to be a consequence of UU activities. Other point sources are estimates of trade effluent. These are considered not to be a consequence of UU activities.

Table AIV 6 Summary of source apportionment by the Environment Agency

Source Contribution (%) Contributor (s) Permitted Sewage Discharges 80 – 85 United Utilities (Current) Physical Structure 5 – 10 Manchester Ship Canal Co Sediment (Historic) 5 – 10 United Utilities/ Industry/Diffuse Local Authorities/Highways Diffuse (Current) 1 – 5 Agency/Contaminated Surface Waters Other Point Sources (Current) 1 – 2 Industry

The calculated values are subject in most cases to a large degree of imprecision. Therefore, the model was run under the following two scenarios:  Maximum UU contribution: 50% of SOD is historic and physical structure is incorporated by adding an extra 5%.  Minimum UU contribution: 100% of SOD is historic and physical structure is incorporated by adding an extra 10%.

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The values generated from each of these scenarios were used to determine minimum and maximum values for source apportionment, which are considered to show a realistic range within which the true means values may fall. AIV.2 Results

Surface water inputs of BOD and AOD are dominated by the contribution from UU assets, including direct inputs to the MSC and indirect inputs via the tributary rivers (Table AIV 7 ).

Table AIV 7 Estimated surface water BOD and AOD inputs, highlighting UU contribution.

a) BOD kg/day percentage UU STW - direct 5,735.3 31.8 contribution STW - river 9,435.5 52.3 CSO -river 1,171.6 6.5 Other SWO - river 819.9 4.5 sources Trade effluent - river 637.7 3.5 Diffuse runoff 246.2 1.4 Atmospheric input - 0

b) AOD kg/day percentage UU STW - direct 6,091.5 29.5 contribution STW - river 11,862.7 57.5 CSO -river 1,478.8 7.2 Other SWO - river 929.4 4.5 sources Trade effluent - river 107.1 0.5 Diffuse runoff 145.2 0.7 Atmospheric input - 0

Total 38,661.1 UU 92.5 percentage

Within the MSC itself, estimates of total oxygen consumption are very variable (mean- 22,593 kg/day; standard deviation – 22,814 kg/day; range- 4434-113.561 kg/day), but the percentage contribution of SOD to this consumption, is somewhat less variable (mean- 23%; standard deviation – 13%; range- 3-57%). In view of this variability, a value of 20% was chosen to represent SOD in the source apportionment model. Using these figures, an alternative source apportionment table was produced (Table AIV 8 ).

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Table AIV 8 Summary of source apportionment using the data analysed here

Source Contribution (%) Contributor (s) Permitted Sewage Discharges 66.7 – 79.2 United Utilities (Current) Physical Structure/sediment 14.5 – 28.0 Manchester Ship Canal Co/ (historic) United Utilities/ Industry/ Diffuse Diffuse (Current) 4.1 – 4.9 Local Authorities/Highways Agency/Contaminated Surface Waters / Agriculture Other Point Sources (Current) 1.2 – 1.4 Industry

A summary of BOD, AOD and Total oxygen demand input data and summary statistics for SOD are provided in Table AIV 9, Table AIV 10, and Table AIV 11.

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Table AIV 9 Ammonia loads

Reach Input Type N Mean StDev Mean Mean STW - CSO - SWO - Trade Diffuse Atmospheric 3 NH4-N NH4-N NH4-N NH4-N mean mean mean effluent river inputs (mg/l) (mg/l) Load Load (kg/day) (kg/day) (kg/day) - mean inputs (kg/day) Oxygen 1 1 1 (kg/day) 2 Demand 1 (AOD) (kg/day) 1 R. Irwell & R. Irk River 17 0.95 0.64 1479.64 6761.97 1241.74 151.60 71.51 0.00 14.80 0.00 1 Rochdale Canal & R. Medlock River 41 0.99 0.74 69.63 318.20 58.43 7.13 3.37 0.00 0.70 0.00 1 Corn Brook River 36 0.09 0.05 15.16 69.28 0.00 4.26 10.75 0.00 0.15 0.00 2 MSC MSC 58 0.59 0.31 958.93 4382.29 ------2 Salford STW STW 80 1.84 0.93 103.71 473.97 ------2 Eccles STW STW 67 1.65 1.30 60.47 276.36 ------3 MSC MSC 55 0.70 0.32 1130.73 5167.42 ------3 Salteye Brook River 32 1.83 1.35 47.36 216.42 0.00 6.65 16.79 23.44 0.47 0.00 3 Davyhulme STW STW 68 0.69 0.67 239.67 1095.29 ------4 MSC MSC 70 0.89 0.48 1442.83 6593.74 ------4 R. Mersey River 37 1.14 0.71 1355.11 6192.87 1154.65 124.26 62.65 0.00 13.55 0.00 4 R. Glaze River 41 0.45 0.40 111.57 509.89 93.63 11.43 5.39 0.00 1.12 0.00 4 Red Brook River 66 0.40 0.58 15.96 72.96 0.00 4.49 11.32 0.00 0.16 0.00 4 Marsh Brook River 66 0.40 0.58 15.96 72.96 0.00 4.49 11.32 0.00 0.16 0.00 4 R. Bollin River 36 0.19 0.16 59.78 273.20 41.87 8.21 9.10 0.00 0.60 0.00 4 Sow Brook River 37 0.20 0.13 7.79 35.60 5.46 1.07 1.19 0.00 0.08 0.00 4 Urmston STW STW 68 5.75 3.14 919.93 4204.08 ------4 Northbank STW STW 37 7.32 7.77 3.28 15.00 ------4 Partington STW STW 63 3.27 6.24 5.86 26.78 ------Total 4 4510.90 20614.82 2595.78 323.59 203.38 23.44 31.78 0.00 Notes: 1 Based on 99% river point source. 2 Based on 1% diffuse river source. 3 Based on 0% atmospheric source. 4 Total does not include MSC.

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Table AIV 10 MSC Turning Basin Total Oxygen Demand Model

2 Reach Month Area (m ) Water BOD BOD BOD load NH4 NH4 Load NH4 SOD SOD % Total Oxygen volume (mg/l (mg/l) 1st (kg) (mg/L) (kg) Oxygen (mg/hr/m2) (kg/day) SOD Consumption (m3) 5 day) day 1 Demand (kg/day) (kg) 1 Mar-12 224755 1573285 1.79 0.89 1405.30 0.59 934.92 4272.61 521.00 2810.34 33.11 8488.25 1 Apr-12 224755 1573285 2.27 1.13 1784.20 0.42 663.65 3032.88 250.00 1348.53 21.87 6165.62 1 May-23 224755 1573285 1.73 0.86 1359.71 0.59 923.57 4220.73 453.33 2445.33 30.47 8025.77 1 Jun-12 224755 1573285 1.55 0.78 1220.65 0.44 687.53 3141.99 541.67 2921.82 40.11 7284.45 1 Jul-12 224755 1573285 1.60 0.80 1254.69 0.28 439.34 2007.78 233.00 1256.83 27.81 4519.31 1 Aug-12 224755 1573285 2.04 1.02 1604.01 0.35 549.17 2509.73 375.00 2022.80 32.96 6136.54 1 Sep-12 224755 1573285 1.72 0.86 1349.58 0.27 425.77 1945.77 519.33 2801.35 45.95 6096.70 1 Oct-12 224755 1573285 2.00 1.00 1576.11 0.31 481.09 2198.60 918.33 4953.60 56.75 8728.31 1 Mar-13 224755 1573285 2.63 1.31 2067.48 0.93 1466.50 6701.90 521.00 2810.34 24.27 11579.71 1 Apr-13 224755 1573285 2.43 1.21 1909.82 0.42 663.65 3032.88 250.00 1348.53 21.44 6291.24 1 May-13 224755 1573285 3.64 1.82 2864.76 0.59 923.57 4220.73 453.33 2445.33 25.66 9530.82 1 Jun-13 224755 1573285 2.00 1.00 1571.01 0.69 1091.07 4986.20 541.67 2921.82 30.82 9479.03 1 Jul-13 224755 1573285 1.49 0.74 1169.15 0.28 439.34 2007.78 233.00 1256.83 28.35 4433.76 1 Aug-13 224755 1573285 2.25 1.12 1766.63 0.35 549.17 2509.73 375.00 2022.80 32.11 6299.15 1 Sep-13 224755 1573285 2.32 1.16 1826.24 0.36 559.01 2554.67 519.33 2801.35 39.00 7182.25 1 Oct-13 224755 1573285 3.26 1.63 2565.87 0.31 481.09 2198.60 918.33 4953.60 50.97 9718.07 2 Jan-07 418868 2932076 2.89 1.44 4233.18 1.26 3704.31 16928.70 974.00 9791.46 31.63 30953.35 2 Mar-07 418868 2932076 2.13 1.06 3115.33 1.85 5409.68 24722.24 252.00 2533.31 8.34 30370.88 2 May-07 418868 2932076 2.46 1.23 3610.12 2.16 6329.62 28926.36 249.00 2503.16 7.14 35039.63 2 Jul-07 418868 2932076 2.58 1.29 3775.05 0.54 1588.82 7260.90 122.50 1231.47 10.04 12267.42 2 Sep-07 418868 2932076 2.46 1.23 3610.12 2.66 7784.66 35575.90 365.00 3669.28 8.56 42855.31 2 Nov-07 418868 2932076 2.38 1.19 3481.84 0.74 2155.08 9848.70 321.50 3231.99 19.51 16562.52 2 Feb-13 418868 2932076 2.50 1.25 3665.10 1.61 4720.64 21573.34 290.81 2923.47 10.38 28161.90

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2 Reach Month Area (m ) Water BOD BOD BOD load NH4 NH4 Load NH4 SOD SOD % Total Oxygen volume (mg/l (mg/l) 1st (kg) (mg/L) (kg) Oxygen (mg/hr/m2) (kg/day) SOD Consumption (m3) 5 day) day 1 Demand (kg/day) (kg) 3 Jan-07 230781 1615467 2.20 1.10 1777.01 1.05 1695.03 7746.28 443.00 2453.66 20.49 11976.96 3 Mar-07 230781 1615467 2.15 1.08 1736.63 2.90 4688.89 21428.24 107.50 595.41 2.51 23760.28 3 May-07 230781 1615467 2.64 1.32 2130.40 1.95 3154.20 14414.69 209.00 1157.60 6.54 17702.69 3 Jul-07 230781 1615467 2.49 1.24 2009.24 0.53 862.46 3941.43 246.00 1362.53 18.63 7313.20 3 Sep-07 230781 1615467 2.04 1.02 1645.76 2.85 4602.06 21031.42 473.00 2619.83 10.36 25297.00 3 Nov-07 230781 1615467 3.23 1.61 2604.94 0.79 1278.24 5841.55 156.50 866.81 9.31 9313.30 3 Feb-13 230781 1615467 3.08 1.54 2483.78 1.63 2625.13 11996.86 907.65 5027.25 25.77 19507.89 4 Jan-07 896028 6272196 5.00 2.50 15664.81 1.00 6263.41 28623.81 999.80 21500.37 32.68 65788.99 4 Mar-07 896028 6272196 1.48 0.74 4641.43 3.54 22203.57 101470.33 346.40 7449.22 6.56 113560.98 4 May-07 896028 6272196 2.44 1.22 7652.08 1.77 11130.01 50864.15 274.40 5900.88 9.16 64417.12 4 Jul-07 896028 6272196 1.96 0.98 6154.59 0.55 3420.44 15631.40 140.20 3014.96 12.16 24800.95 4 Sep-07 896028 6272196 2.41 1.21 7558.00 1.21 7561.76 34557.24 231.80 4984.78 10.58 47100.02 4 Nov-07 896028 6272196 2.00 1.00 6256.52 0.79 4960.05 22667.44 352.00 7569.64 20.74 36493.60 4 Feb-13 896028 6272196 1.57 0.79 4923.67 1.24 7777.52 35543.28 570.84 12275.63 23.27 52742.58

1 Assumes 50% BOD removed in first 24 hours 2 Nitrification reqires 4.57 mg/l O2 per mg of NH4, therefore load (mg) is multiplied by 4.57 to obtain AOD

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Table AIV 11 SOD Data

Reach Mean SOD StDev SOD Mean % SOD StDev % SOD (kg/day) (kg/day)

1 2570.073425 1122.377581 33.8534907 10.25708442 2 3697.73378 2793.32649 13.65905183 8.924696154 3 2011.871053 1534.396521 13.37093734 8.39017862 4 8956.497 6231.290029 16.45112817 9.418471768

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AIV.3 Discussion

The figures presented in Table AIV 8 are generally similar to those in Table AIV 6 , with the main exception that the permitted sewage discharges component is around 10% lower and the combined physical structure/sediment component is higher. Increasing the proportion accountable to physical structure/sediment is considered justifiable because the creation of the canal itself led to the capture and storage of sediment that plays a key role in determining oxygen demand. In a natural low gradient river system the sediment would be retained in the system, albeit on the floodplain rather than in the channel; however, in the sort of industrialised river we would expect had the canal not been built, the river would have been separated from its floodplain and therefore flushed its sediment and deposited it in the estuary. The presence of the canal, therefore, is the single reason for the retention of sediment. While the estimates of impact of physical structure alone are derived from the range given by the EA, in practice there will be huge variation. The role of MSC structure in determining oxygen demand will be highly dependent on the weather and is also strongly seasonal. During warm, dry periods with no wind and therefore little mixing, oxygen demand will be very high and physical structure/sediment accountable for up to 100%. Conversely during winter it may account for 0%. Hence the range quoted in Table AIV 8 can be regarded as conservative. Diffuse inputs are calculated as contributing towards the higher end of the range identified by the Agency, mainly derived from estimated inputs from SWOs, which contribute c. 4%. The remainder (less than 1%) is an estimate derived from walkover data, including that collected on behalf of UU from Micker Brook, that shows evidence of inputs from features such as abandoned landfill sites, septic tank overflows and slurry stores.

Inputs from industry are in line with the predictions made by the EA.

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Appendix V Flood Risk AV.1 Introduction Each local authority is required by law to prepare Strategic Flood Risk Assessments (SFRA) to provide a central location for data pertaining to all sources of flood risk and to inform strategic planning decisions. In addition, the EA have a statutory duty to prepare fluvial flood risk maps based on hydraulic model data which they publish on their website2.

Local authority and EA documents relevant and available include:

Manchester City, Salford City, and Trafford Councils

 Manchester City, Salford City, and Trafford Councils Level 1 SFRA (March 2010)  Manchester City, Salford City, and Trafford Councils Level 2 Hybrid SFRA (March 2011)

Warrington Borough Council

 Warrington Strategic Flood Risk Assessment (Warrington Borough Council, 2007).  Warrington Borough Council Strategic Flood Risk Assessment Volume I - SFRA Guidance Report September 2011  Warrington Borough Council Strategic Flood Risk Assessment Volume II - SFRA Guidance Report September 2011

Environment Agency

 The Environment Agency – NW Region (South Area) Manchester Ship Canal Flood Mapping Study (2009) hydraulic modeling report.

These documents are comprehensive. The following section summarises the findings pertaining to the MSC in these documents with reference to each report provided so that the reader can consult the appropriate document for further information if required. AV.2 Sources of Flooding Fluvial Flooding Information within the SFRA and EA documents is obtained from two sources:

1. Recorded Historic Incidences of Flooding 2. Hydraulically Modelled Flood Levels and Extents.

The results from each information source for the MSC between Salford Quays and Latchford Locks is described below.

Historical Incidences of Flooding

Historical flood records can help build a picture of the level of flood risk. They are often anecdotal and incomplete and it can be difficult to determine accurately the frequency and consequences of events, but can be useful for providing background information. Gauged records and registers of flooded properties are valuable for estimating flood frequency and severity at different locations.

2 http://watermaps.environment- agency.gov.uk/wiyby/wiyby.aspx?&topic=floodmap#x=357683&y=355134&scale=2

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A summary of recorded incidences attributed to the MSC is presented in Table AV 1 .

Table AV 1 Historic records of flooding from the MSC

Date Source Description Data source 2008 MSC Overtopping of tow path SFRA Steering Group Manchester City, Salford City, 2004 MSC Overtopping of MSC Salford City Council and Trafford Councils Level 1 flooded 16 properties at SFRA: Barton Upon Irwell and roads in Peel Green

The EA MSC Flood Mapping Study (2009) hydraulic modeling report lists a number of fluvial flooding incidents along the MSC corridor whilst the Warrington Borough Council Strategic Flood Risk Assessment lists both tidal and fluvial flooding events that occurred on the Mersey despite the presence of the MSC, most recently in February 1990 and October/November 2000, however no events in either documents were attributed directly to the MSC.

Hydraulically Modelled Flood Levels and Extents

The sluice gates on the MSC are mainly used to maintain water levels for boats and ships. However, in times of very high flows they can be used to allow excess water to pass along the canal, reducing the risk of flooding to the surrounding areas. In Warrington, the MSC plays an important role in reducing flood risk from the River Mersey by diverting high flows away from the town centre. Indeed the Warrington Borough Council Strategic Flood Risk Assessment Volume II - SFRA concludes that:

Warrington has benefited from the Manchester Ship Canal, which transfers significant flow past Warrington and reduces the risk of fluvial flooding along the Mersey. Since its construction in 1894, the Mersey through Warrington has not caused fluvial flooding.

The Environment Agency MSC Flood Mapping Study (2009) hydraulic modeling report states:

It would appear from the limited number of mentions in the records that there have been few incidents of flooding along the Manchester Ship Canal corridor since its completion in 1894. The perception is therefore that there is little flood risk along the canal.

Individual automated systems control the movement of each set of sluice gates, the performance of which is constantly monitored by the MSCCo Lockmaster at Latchford Locks. Statutory water levels are maintained in each of the four upstream pounds by real time control of sluice gates, aided by the syphon weir at Woolston, which minimises variation in the “normal” upstream level through a wide range of flows. Maintenance of water levels in the MSC is based upon a set of Statutory Water Levels (SWLs) that have been agreed through a Parliamentary Act. Although the SWLs have been raised over the life of the canal, the last revision took place in 1956 (Manchester City, Salford City, and Trafford Councils Level 1 SFRA, 2010). Actual Water Levels (AWLs) in the canal vary from the SWLs for navigational reasons. The Harbour Master sets the AWLs and it is at these levels that the operators of the locks/sluice system must endeavour to maintain the canal. The AWLs are usually set to what is known as Normal Water Levels (NWLs). If water levels rise, the sluices are progressively opened to allow water to pass down the system.

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The Strategic Flood Risk Mapping hydraulic model of the MSC was developed by the EA to determine the flood risk from the canal. This model is based on work carried out for the MSCCo and is documented in Halcrow, (2005) and Halcrow (2008). The model has subsequently been amended to include the River Irk and River Medlock models (EA, 2008). The upstream point on the River Irwell in the model is at the rail bridge downstream of the A6042 Trinity Way road bridge near the confluence with the River Irk. The downstream boundary of the model is at Eastham.

The model report initially contained flood zone results based on a ‘sluices shut’ scenario at each lock system on the canal based on their policy of excluding flood defences in their mapping scenarios. However following a High Court challenge by MSCC, and developer Peel Land and Property, the model was changed to include sluice gate operation and the report is provided with the following EA caveats:

We have a series of models to simulate a range of gate failures (gates not opening). However please note the one that reflects the Flood Map is with all gates operational. You may request further models with gate failure to investigate how robust the system is to meet your needs’

Flood Mapping of the Manchester Ship Canal in Trafford, Salford and Warrington was updated on 9 August 2012 as a result of a judgment of the High Court. The judgment concluded that the Ship Canal sluice gates should not be regarded as 'formal' flood defences’ and that the decision to map the Ship Canal flood zones as if the sluice gates were closed was unlawful. We have applied to the Court of Appeal to appeal against this judgment, and we will keep this caveat updated.’

This EA appeal was rejected in May 2013.

Consequently, the model and model results that are shown on the EA flood maps reflect a sluice ‘fully operational’ scenario. This is in contrast with the SFRAs in the area which pre- date the High Court ruling and show a ‘sluice shut’ scenario. In the sluice operating scenario all sluice gates along the canal are open (four gates open at Mode Wheel and three gates open at all other sluices). This allows large flows originating from upstream catchments to flow unobstructed down the MSC.

For example at Latchford, during low and medium flows (up to a discharge of about 140 m³/s), Latchford sluices remain closed and water flows down the Mersey leg from Rixton to Woolston Weir. When flows at Woolston exceed a certain volume, the Latchford sluices, which have a capacity of about 560 m³/s, are opened to relieve the River Mersey channel through Warrington. During peak flow, the MSC conveys approximately 70% of the discharge, which therefore bypasses central Warrington, and this proportion reaches about 80% for a 1 in 100-year flood event on the River Mersey. However, even with optimum operation of the sluices, there is still a risk of flooding when considering an extreme 1 in 1000-year event, for which EA modelling predicts significant depths of water on the floodplain (Warrington Borough Council, 2011). AV.3 Flood Risk Results The EA flood maps provide information on flood extents based on four flood risk scenarios colour coded according to Figure AV 1 .

 High Flood Risk: Means that each year, this area has a chance of flooding of greater than 1 in 30 (3.3%).

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 Medium Flood Risk: Means that each year, this area has a chance of flooding of between 1 in 100 (1%) and 1 in 30 (3.3%).  Low Flood Risk: Means that each year, this area has a chance of flooding of between 1 in 1000 (0.1%) and 1 in 100 (1%).  Very Low Flood Risk: Means that each year, this area has a chance of flooding of less than 1 in 1000 (0.1%).

Figure AV 1 Environment Agency flood risk mapping colour bands

These flood maps take into account the effect of any flood defences that may be in this area. However for planning and development purposes, EA policy is for an undefended scenario to be used for delineating flood zones referred to in the National Planning Policy framework and as provided in the SFRA. This ensures that residual risk from flood defence failure is accounted for in new development.

The differences between the undefended and defended scenarios is substantial. For example in the undefended scenario, the SFRA flood zone map shows extensive flooding to Salford Quays, Ordsall and Trafford Park at the Medium Flood Risk 1:100 event (Figure AV 2 ) whereas in the defended scenario (EA online flood maps, Figure AV 3 ) this area is free from flooding. For the Low Flood Risk 1:1000 event, both maps are in general agreement.

However until the local SFRA is updated with the results from the high court ruling, there appears to be confusion as to which map should be used for planning and development purposes. Currently the undefended scenario with the full MSC sluice gate operation does not appear to exist in the SFRA (various scenarios exist with partial operation but not full operation).

For the purposes of describing flood risk in this report, the defended scenario as published on the EA website has been used.

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Figure AV 2 Manchester City, Salford City, and Trafford Councils Level 2 Hybrid SFRA flood zone map (March 2011) showing undefended scenario including a MSC ‘sluices shut’ scenario.

Figure AV 3 Environment Agency online flood map of Salford Quays showing a defended scenario including a ‘MSC fully operational’ scenario

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Salford Quays to Irlam

For the reach between Salford Quays and Irlam, the following can be seen (Figure AV 4 ):

 The area that has a High flood Risk from the MSC is limited to the area around the WwTW at Irlam Locks and the open ground between the MSC and Towns Gate on the south east side of the canal

 The area that has a Medium Flood Risk appears to be the same as the High Flood Risk extent with the exception of a small inundation on the left bank at Mode Wheel and on the left bank at Dumplington.

 The area that has a Low Flood Risk includes most of the MSC corridor with particularly extensive inundation at Ordsall, Salford Quays, Trafford Park, Dumplington, Barton upon Irwell, Peel green, Urmston, and Irlam.

Figure AV 4 Environment Agency online flood map of Salford Quays to Irlam

Irlam to Latchford Locks

For the reach between Irlam and Latchford Locks, the following can be seen (Figure AV 5 ):

 The area that has a High flood Risk from the MSC is limited to the extensive area on the left bank of the MSC between Warburton and Thelwall and on the right bank at Rixton and the Westy Park Works. Note, there are also a number of other smaller areas of inundation attributed to flooding from tributaries that may be backing up from the MSC.

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 The area that has a Medium Flood Risk appears to be the same as the High Flood Risk extent with the exception of greater inundation at Warburton and to the East of Junction 21 of the M6 associated with the overtopping of the Butchersfield Canal (linked to the MSC).

 The area that has a Low Flood Risk covers similar areas to the Medium Flood Risk extent but also includes parts of Irlam, Cadishead, Warburton, Heatley, Statham, Thelwall and Westy.

Figure AV 5 Environment Agency online flood map of Salford Quays to Irlam AV.4 Conclusion

To conclude, historic incidences of flooding from the MSC itself appears sparse, although flooding from its tributaries may be more significant and could be attributed to water levels on the MSC.

The hydraulic modelling studies show that under a defended scenario as published on the EA online flood maps, the risk of flooding is predominantly low, with the exception of the Warburton to Thelwall left bank area, although it is not clear whether the mechanism for flooding is from overtopping of the MSC or backing up from the tributaries including the River Bollin.

In an undefended scenario, the flooding is much more extensive and occurs much more frequently. This highlights that there is appears to be substantial level of residual risk to the MSC corridor in the event of failure of sluices to operate on the MSC or other failures such as a breach in flood defences.

Determining the level of existing and residual flood risk is therefore complex and differs according to the magnitude of flood flow in the MSC channel (and tributaries) and level of

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