United Utilities Manchester Ship Canal Water Quality Review Part 1 of 2 (Primary Document)

UNITED UTILITIES

______

MANCHESTER SHIP CANAL

WATER QUALITY REVIEW

PART 1 OF 2

(PRIMARY DOCUMENT) ______

FINAL REPORT

September 2007

APEM REF: 410039

APEM Scientific Report 410039

CLIENT: United Utilities

ADDRESS: Haweswater House, Lingley Mere Business Park, Lingley Green Avenue, Great Sankey, Warrington, WA5 3LP

PROJECT No: 410039

DATE OF ISSUE: September 2007

PROJECT DIRECTOR: Dr. Keith Hendry

PROJECT MANAGER: David Campbell, M.Sc.

SENIOR SCIENTISTS: Dr Roger Baker Margaret-Rose Vogel Heather Webb Kathleen Beyer

Riverview, Embankment Business Park, Heaton Mersey, Stockport, SK4 3GN Tel: 0161 442 8938 Fax: 0161 432 6083 Website: www.apemltd.co.uk Registered in England No. 2530851

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APEM Scientific Report 410039

CONTENTS

1 INTRODUCTION ...... 1 1.1 BACKGROUND TO WATER QUALITY WITHIN THE MSC ...... 1 1.2 SPECIFIC WATER QUALITY ISSUES OF THE MSC...... 2 1.3 WATER QUALITY IN THE PRESENT DAY WITHIN THE MSC ...... 3 1.4 INTRODUCTION TO DATA AVAILABILITY AND PREVIOUS WATER QUALITY REPORTS ...... 4 1.4.1 Data Availability ...... 4 1.5 BACKGROUND TO PREVIOUS REPORTS REVIEWING THE WATER QUALITY OF THE MSC...... 6 1.5.1 Academic reviews (1988-Present) ...... 6 1.5.2 APEM Review (1990) in association with Watson Hawksley (now MWH) ...... 7 1.5.3 Harper Review (2000)...... 7 2 REVIEW OF MSC WATER QUALITY DATA ...... 9 2.1 BOD ...... 9 2.2 AMMONIA...... 12 2.3 DISSOLVED OXYGEN ...... 14 2.4 SUSPENDED SOLIDS AND TRANSPARENCY...... 17 2.5 NUTRIENTS (PHOSPHORUS)...... 17 2.6 BACTERIOLOGY...... 18 2.7 OTHER DATA ...... 19 2.7.1 Metals...... 19 2.7.2 pH...... 19 2.7.3 Conductivity...... 20 2.7.4 Residual chlorine...... 20 2.8 SEDIMENTS ...... 20 2.9 KEY FINDINGS ...... 22 3 REVIEW OF MSC BIOLOGICAL DATA...... 23 3.1 HISTORICAL REVIEW OF MACRO-INVERTEBRATE DATA ...... 23 3.1.1 Upper MSC ...... 23 3.1.2 River Inputs...... 24 3.1.3 Salford Quays ...... 26 3.2 HISTORICAL REVIEW OF ALGAL DATA ...... 26 3.3 KEY FINDINGS ...... 28

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Final Report – September 2007 APEM Scientific Report 410039

Foreword

This report details a review of water quality within the Manchester Ship Canal and is the product of an extensive data and literature search. The primary section of the document provides a summary of important data and discusses the associated relevant issues. Detailed descriptions of the data used along with various graphs and charts are presented in an associated technical document (Appendix document).

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1 INTRODUCTION

The Manchester Ship Canal (MSC) was opened in 1894 creating a major freight access corridor into the heart of industrial Manchester. It extends some 35 miles (56km), from the River Mersey at Eastham to Manchester Docks. Following a decline in shipping use, Manchester Docks (now renamed Salford Quays) eventually closed as a shipping port in 1984, leading to severe urban decline in the area. Subsequent regeneration in Salford Quays from the 1987 onwards has since led to a thriving area of intense development with the Quays currently playing host to modern apartment buildings, office developments and art and cultural centres. The shift from deprivation and decline in the Quays area to its current prosperity is inextricably linked to the history of water quality within the Manchester Ship Canal.

This review is specifically concerned with the changes in water quality of the MSC and Salford Quays over the past three plus decades (for which survey data were available), along with development of the ecology of the phytoplankton, periphytic diatoms, and benthic macro-invertebrate communities present in this system. It was prepared for United Utilities as part of a wider investigation into the water quality of the Manchester Ship Canal (MSC), within the context of the European Community Freshwater Fish Directive (EC FFD). Crucially, the MSC has been designated under the directive as a cyprinid fishery from the River Irwell near Salford University to the freshwater limit of the Canal at Latchford Locks (22km of the MSC). The quality of water in the MSC does not currently meet the EC FFD standards, which has ultimately been the impetus behind this study.

The objective of this review is to summarise the extent of the water quality monitoring that has been conducted on the MSC and Salford Quays and to discuss the changes that have taken place in the aquatic environment of these water bodies over the preceding decades.

1.1 Background to Water Quality Within the MSC

The Manchester Ship Canal has experienced poor water quality since its construction. The overriding issues driving this are two fold; one that the Mersey catchment is arguably overpopulated and two; that as a water body the MSC is essentially too small for the catchment it serves.

Regarding the first of these points, the Upper Mersey catchment encompasses large densely populated areas including the cities of Manchester and Salford which generate huge amounts of anthropogenic waste. This is particularly true of the River Irwell, that flows through the centre of Manchester and directly into the MSC at its upper extent. Over 90% of the Irwell’s dry weather flow is made up of combined sewage effluent from the various waste water treatment works (WwTWs) and industrial effluents along the river. In addition, the construction of the sewer network is such that during heavy rainfall events, the sewer system is occasionally unable to cope with the large volumes of water entering it, which bring about direct spills of untreated sewage from the combined sewage overflows (CSOs) (Rees and White 1993). During a CSO event untreated sewage is washed into the MSC, adding further to the dry

Final Report – September 2007 APEM Scientific Report 410039 weather pollutant load. This clearly presents severe water quality issues for the Ship Canal, but further to this, not only is the inflowing water extremely polluted, but as this water enters the MSC the physical nature of the Canal exacerbates the problem.

The MSC receives water from a number of arguably heavily modified but reasonably natural rivers, including the Rivers Irwell, Irk, Medlock, Mersey and Bollin, which combine to give an average total inflow of over 3000 Megalitres (Ml) per day. However, the physical structure of the Canal fundamentally changes the flow regime of these rivers by slowing the flow, which has a profound effect upon water quality. The vertical walls and deep nature of the Canal (up to 9m) dramatically changes the hydraulic regime compared to that experienced in the inflowing rivers. The high residence time in the Canal means that pollutants are not readily flushed out and particulate contaminants can settle out onto the sediment layer. As a result the water within the Canal can become stratified and the lower sections of the water column often become anoxic.

The effect of a change in flow on water quality is clearly observable with regards the River Irwell. 5km upstream of the MSC the River Irwell at Adelphi Weir contains a similar level of pollutants to that entering the MSC, but does not display the same water quality problems. At Adelphi Weir the river is relatively fast flowing and turbulent having the additional benefit of the weir’s mixing and oxygenating potential. As the same waters flow into the Turning Basin at Salford Quays, the speed of flow decreases, as does the water’s particulate carrying capacity. As such, particulate pollutants can settle out and are deposited on the bed, building up gradually over the years to eventually create a thick layer of severely contaminated sediment. The bottom sediments in turn exert a demand for oxygen on the overlying water that combined with high retention time, facilitate stratification and bottom water anoxia during the warmer months.

1.2 Specific water quality issues of the MSC

Water Quality within the MSC is considered poor due to high levels of biological oxygen demand (BOD), ammonia and suspended solids (SS) within the water column and a high sediment oxygen demand (SOD) from the bottom deposits. The MSC also experiences high levels of nutrients, bacteria and metals.

The high BOD, SOD and ammonia combine to exert a total oxygen demand on the water, which if not satisfied, leads to oxygen stripping and eventual anoxia. Bottom water anoxia has historically been a common problem within the MSC and, although very little oxygen profile data exists below Mode Wheel Locks, probably occurs in the layer of water immediately above the sediments throughout the summer months. In terms of fish populations, a confined anoxic layer in the lower depths of stratified water does not present a significant problem. However under certain conditions, for example following a combined sewage overflow (CSO) event coincident with warm dry weather, the deoxygenated layer can extend toward the surface and create total water column anoxia. However, it is also important to realise that anoxia can occur in the absence of a CSO spill during prolonged spells of hot, dry weather. An example of this occurred during 2006 when several thousand fish were killed during an extended

Final Report – September 2007 APEM Scientific Report 410039 warm, sunny period, when total water column anoxia was experienced after several weeks without rain. Both types of event occur annually in the MSC below Mode Wheel locks and lead to large scale fish kills.

Another pertinent issue concerns the levels of suspended solids and nutrients. The MSC has high phosphorous and nitrate concentrations within the water column due to the pollutants of the inflowing rivers and WwTW effluent. This, coupled with high levels of phosphorous in the underlying sediments creats the potential to fuel severe algal blooms. Such high productivity is, however, prevented from occurring by the high turbidity of the water, restricting light penetration and therefore denying algae of the energy they need to thrive. If turbidity of the water were to decrease then algal productivity would rapidly increase to a hyper-eutrophic level and the resultant algal blooms could have a detrimental impact upon the ecology of the system. It is therefore important to consider this in the context of any future works that may impact upon turbidity (i.e. reducing suspended solids loads from WwTW).

In terms of fish health, heavy metal contamination of the water and bottom sediments can impact upon fish, through bioaccumulation up the food chain, although to date there is little evidence of this occuring. In addition the MSC contains high levels of endocrine disrupting chemicals largely coming from anthropogenic oestrogen (the natural steroids oestrone and 17β-oestradiol) and synthetic steroids (ethinylestradiol) entering the watercourse, which cause sex reversal of fish. This is a major issue and an increasing problem in many inland waters running through heavily populated areas as it leads to the feminisation of the fish population. The impact of feminisation on fish populations are, as yet poorly understood.

1.3 Water Quality in the Present Day within the MSC

The issues discussed above concerning water quality have prevailed in the MSC for many decades, and although the overall trend is one of improvement, most continue to the present day below Mode Wheel Locks. However, above Mode Wheel locks, in the Turning Basin and at Salford Quays, significant changes to the way the water body is managed have resulted in dramatic improvement in water quality.

The potential real estate value at the disused docks at Salford, following closure in 1984, was highly attractive in terms of redevelopment due to the combination of water frontage and its location near urban centres (Hendry, 1991). However, poor water quality precluded the initiation of such development due to aesthetically unpleasant floating rafts of sediment, bubbling of hydrogen sulphide and associated unpleasant odours. For this reason, initiatives to improve conditions in the MSC began in the 1980's (Hendry et al., 1993) as part of an overall development plan supported financially by the government. Salford City Council bought the land surrounding Salford Quays in the early 1980's (Law and Grime, 1993) and three of the Salford Quays basins were isolated from the MSC (1987-89).

The isolation of Basins 7, 8 and 9 (around 20 acres of enclosed water) created what is known today as Salford Quays and fundamentally changed water quality within them. The isolation prevented polluted water from the Irwell entering the Quays and

Final Report – September 2007 APEM Scientific Report 410039 investigations by APEM and NWW led to the installation of a destratification system in 1987, which eventually created a system with water quality suitable as a ‘blue flag’ bathing water. Today the Quays are used as a major water sports centre for the North West, the success of the water management system being displayed on the world stage as it hosted the international triathlon event in the Commonwealth Games of 2002 and subsequent world cup events.

Along side the success story of Salford Quays, impressive improvements were also made to the adjacent Turning Basin area of the MSC, upstream of Mode Wheel Locks. The Mersey Basin Campaign (MBC) (set up in 1985) contracted APEM in association with Watson Hawksely (now MWH) to explore remediation options for the aquatic environment of the MSC in 1989 (APEM, 1990a and b) and a series of studies investigating the feasibility of oxygen injection in the MSC followed (APEM, 2000). These studies resulted in the installation of five oxygen injection units in the upper MSC and the successful maintenance of average bottom water dissolved oxygen concentrations above the minimum management target of 4 mg/l (APEM, 2007a) in the 70 acres of the Turning Basin adjacent to the Quays. Routine water quality monitoring of the Manchester Ship Canal and Salford Quays is currently conducted by APEM on behalf of Salford City Council, and in the Turning Basin on behalf of United Utilities.

1.4 Introduction to Data Availability and Previous Water Quality Reports

1.4.1 Data Availability

By far the most detailed and extensive water quality data set available in the MSC and Salford Quays comes from APEM ltd and their monitoring contracts with Salford City Council and United Utilities together with ongoing research undertaken by the company over the last 20 years.

At Salford Quays APEM have monitored dissolved oxygen and temperature profiles within all basins since 1987 (initially through academic research of Hendry (1991) and Montgomery (1988)). This is conducted on a weekly basis from November to April, and twice weekly from May to October. In addition to this a more detailed survey is carried out on a monthly basis and incorporates water quality measurements of BOD, pH, Conductivity, Secci depth, Chlorophyll a, nutrients and ammonia. Suspended solids are measured four times per year, and phenols, metals and pesticide levels are measured twice yearly (APEM, 2007b). This provides a crucial data set as it monitors the progression of water quality in the Quays since isolation and provides empirical data as to the effects of removing the inflow of polluted water into the system. Such an insight will prove invaluable to future plans for improvement in the MSC enabling a ‘control’ scenario to be developed to help in water quality model calibration as part of the wider catchment study. In addition, the development of the biota in the absence of water quality pollution loads but in the presence of highly contaminated sediments will also be invaluable in this project. However, perhaps the most important data relates to two control sites located in the MSC. These sites were monitored along side the Salford Quays monitoring program and demonstrate the difference in water quality between the open MSC and closed basins (isolated from

Final Report – September 2007 APEM Scientific Report 410039 the MSC and hence devoid of sewage related inputs). Prior to the APEM sampling program some additional data collection was commissioned by Salford City Council (undertaken by the North West Rivers Authority) as well as work undertaken by Manchester University between 1985 and 1987.

APEM Ltd, are also commissioned to undertake intensive monitoring in the MSC upstream of Mode Wheel Locks in the summer (May to September) on behalf of United Utilities. The intensive summer monitoring on the Ship Canal is conducted in order inform the management of the MSC oxygenation project, which became operational in July 2001 (APEM, 2002). The objective of the scheme is to maintain oxygen levels above 4mg/l, whilst minimising oxygen usage. Temperature and dissolved oxygen profiles (1m resolution) are measured 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 units.

Together the sampling program within Salford Quays and the MSC above Mode Wheel locks provide a precious dataset. Crucially, the sampling programs were undertaken with profile measurements of DO and temperature, data largely unavailable from any other data records. This gives insight as to the occurrence of bottom water anoxia (which would otherwise be missed by surface sampling only).

The Environment Agency conduct 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 1975 and encompasses a number of sites between Pomona and Latchford Locks. 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. A more detailed appraisal of the EA monitoring sites and data is provided in Appendix Section 1. However, the data is for surface sites only, severely limiting it’s usefulness in this study. This is primarily because bottom water anoxia is rarely present within 30-50cm of the water’s surface. However, experience from the APEM data set has revealed that during summer months, below this depth the water column can be completely devoid of oxygen and hence to all intense and purposes, devoid of life. However, in recent years the EA has deployed continuous water quality monitoring probes (data sondes) capable of continuous monitoring of water quality parameters such as DO, temperature, pH and conductivity. 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. Of great value is the diurnal data that reveals the extent of oxygen flux (supersaturation to anoxia) as a consequence of algal bloom photosynthesis and respiration and the effect of storm water and/or still windless weather conditions over several days. The sondes are deployed at a fixed depth at the surface and although they do not provide the valuable profile data throughout the water column described above, present a useful short-term temporal data set, which again is important in assessing the functions of the MSC system. Three data sondes are deployed upstream Barton Locks, Upstream of Irlam Locks and at Partington (between Irlam and Latchford Locks).

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1.5 Background to Previous Reports Reviewing the Water Quality of the MSC

1.5.1 Academic reviews (1988-Present)

One of the earliest academic investigations into the water quality of the MSC was by Montgomery (1988). This work in collaboration with Hendry (1991) 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 huge potential for 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 as to the effects of isolation and artificial mixing in Salford Quays and provided insight as to the water quality improvements of the Quays within the context of other similar systems within the UK. It provides the first investigation as to the response of water quality in the Quays to the installation of artificial mixing units (Helixors) and the subsequent effect upon biota. As found in 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 hugely important finding for the future management strategy of the MSC coming out of Hendry’s work was how an increase in trophic status (algal blooms) occurred following isolation. As discussed previously, turbidity in the MSC water inhibits algal growth, but following isolation the inflow of turbid water ceased. This resulted in a ‘clearing’ of water, allowing much greater light penetration which, combined with high levels of nutrients leached from the sediments, lead to elevated algal productivity. However, despite this tendency for increased trophic status, the overall improvements in water quality were found to be beneficial for biota. Eventually, after a period of about eight years, the excessive algal blooms were brought under control, allowing a balanced and diverse ecosystem to develop. Again, 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 APEM Ltd, each providing data on the various microbiological and ecological aspects of the MSC. Teesdale (2002) carried out some important work of the spatial variation of sediment oxygen demand between Pomona and Mode Wheel locks finding that SOD was highest within the Turning Basin. This was attributable 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.

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1.5.2 APEM Review (1990) in association with Watson Hawksley (now MWH)

APEM (1999a and 1990b) compiled a comprehensive review of historical data available within the MSC Salford Quays, and the input rivers Irwell, Irk and Medlock. It drew upon data recorded by the North West River Authority (now the Environment Agency) and the APEM data archive.

Detailed mass flux analysis revealed that at the 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 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 Medlolck, that periodically resulted in large volumes of organic pollutants entering the river network. The loading of BOD and ammonia from these events were found to enter the MSC where much of the particulates would settle (due to slowing of flow) and create an elevated oxygen demand, eventually creating 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, to sediment oxygen demand (SOD). Sediment cores were taken at various sites in the upper MSC and analysed for gas release and the demand for oxygen 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.

1.5.3 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.

1 At that time intensive pig farming in the Medlock valley formed a significant contribution to the organic pollution load. 7

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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. As part of the current investigation, these data have been extended using more recent information to create an invaluable and almost continuous data set of water quality within the various pounds of the MSC and inflowing rivers over the 32 years.

Of particular importance was the comment by Harper recognising the MSC as the ‘sump’ of the Mersey basin system. The artificial nature of the Canal (depth and vertical walls) meant that it was inevitable that given the high population density and hence sewage derived load to the Canal, that society could not expect it to behave as a ‘normal’ river would and absorb the polluting loads. In fact the opposite was anticipated where serious future problems might be expected, 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 for the future of the MSC to continue its progress of water quality improvement. These included improvements to the WwTWs and CSOs in the catchment, develop ing a more in depth water quality model to understand the water quality processes within the MSC and undertaking detailed ecological surveys. These points are particularly important for the current investigation and demonstrate the historical context in which the current survey lies.

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2 REVIEW OF MSC WATER QUALITY DATA

This section provides a summary of water quality data for the Manchester Ship Canal with reference to specific water quality parameters. Further technical details and data are presented in the technical document in Appendix I.

2.1 BOD

Biological oxygen demand (BOD) is a key parameter in the Freshwater Fish Directive (EC FFD 78/659/EEC) and gives an indication of the organic matter present in the water column. Decomposition of this organic matter by bacteria strips dissolved oxygen out of the water causing significant problems for fish and aquatic ecology as a whole. In cyprinid waters such as the MSC, the EC FFD (UK amendment) designation stipulates that BOD should remain below 6 mg/l for 92% of the time. However, based upon EA data the MSC repeatedly fails this target, resulting in non- compliance. Further, it is likely that the existing sampling program by the EA has repeatedly missed some of the highest BOD values that occur following a CSO event. As such, historical records may under represent the high BOD values of the MSC.

As discussed in Section 1.1. high organic load entering the MSC can be attributed to the high population density of the surrounding catchment and associated sewage effluent inputs. The significance of these organic inputs entering the MSC are clearly apparent considering that over 90% of the dry weather flow in the River Irwell originates from sewage effluent (Hendry, 1991). The significance of the River Irwell upon MSC water quality is clearly apparent from detailed mass balance analysis, showing that 84% of the BOD load entering the MSC in the upper reaches during 2006 originated from the Irwell (Appendix Section 3). This is compared to similar analysis in APEM (1990b), which showed the same dominance of the Irwell’s BOD loading in the Upper MSC. However, while the Irwell has remained the chief polluting input, since 1990 there has been a halving of the overall load entering the MSC showing a marked improvement in the WwTW discharging into the inflowing rivers .

High BOD has been an issue in the MSC for many years and since 1986 APEM have gathered an important long term dataset from the MSC upstream of Mode Wheel Locks. Routine monitoring of BOD at two sites have shown a continued improvement and echoes the data presented by Harper in 2000(a) (Figure 1.1). At APEM Site 1 the mean annual BOD has decreased from 6.4 mg/l in 1986 to 2.9 mg/l in 20062. This long term dataset provides a valuable history of BOD in the MSC revealing an improving trend at all sites (Figure A2.2).

A thorough understanding of BOD in the MSC is important in the context of the current study to enable accurate modelling of water quality processes. BOD is a key factor contributing to low DO and therefore the APEM dataset will prove invaluable for assessing whether reducing the effluent inputs to the MSC would improve compliance with the FFD. Accurate measurements of BOD are an essential part of understanding these processes. With reference to this, a comparison of EA and APEM

2 Peak values of BOD as high as 85mg/l were recorded. 9

Final Report – September 2007 APEM Scientific Report 410039 data collected between Trafford Road Bridge and Mode Wheel Locks was made and highlights the importance of commencing BOD measurement in accordance with industry standard ‘blue book’ techniques recommendations within three hours of the sample being taken. Measurements of BOD undertaken by APEM were consistently higher than EA measurements (taken at Trafford Road Bridge) between 1988 and 1992. In fact measurements of BOD taken by the EA were up to 50% lower than those measured by APEM. This difference can be attributed to the storage of BOD samples by the EA for up to 48 prior to analysis which results in a reduction in the organic matter available for decomposition. Conversely with APEM samples, the analysis is started within 3 hours of sample collection which reduces the risk of unpredictable changes in BOD on storage (HMSO, 1998). For example it is known that in conventional BOD analysis 50% of the BOD is exerted in the first 24 hours of the 5- day test. The accurate measurement of BOD rapidly after sample collection is of obvious fundamental importance to the modelling of processes occurring in the MSC.

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20 Irwell Salford (Harper, 2000a) d/s Barton Locks (Harper, 2000a) Value not known but > 20 mg/l 18 Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) Latchford Locks (Harper, 2000a) 16 River Irwell at Foot Bridge at Salford University MSC below Barton Locks MSC at Irlam Locks 14 MSC at Latchford Locks Mersey at Howley Weir 12

10 BOD (mg/l) 8

0 1972 1973 1974 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

Figure 1.1 BOD annual averages in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Appendix Section 2.

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2.2 Ammonia

Inputs of sewage and industrial effluents have contributed to historic problems with ammonia in the MSC. These high concentrations continue to the present day and have resulted in the non-compliance with the cyprinid waters standards of the FFD. As with BOD, mass flux calculations reveal the Irwell contributes the greatest load to the Canal, although during localised storm events the water entering from the Irk historically was of significance (1990a,b). Some of the highest concentrations of ammonia (as well as BOD) within the MSC can be attributed to the flushing of combined sewage overflows (CSO’s and to a lesser extent storm storage tanks) following storm events. These are particularly problematic following periods of dry weather flows.

The un-ionised form of ammonia is of chief concern due to its toxicity to fish. The transformation of ammonia to un-ionised ammonia is facilitated by high pH and temperature which often occurs in the summer months. However, recent improvements have been observed and, since 1995 (with the exception of 2002) the mean annual un-ionised ammonia at APEM monitoring Site 10 has been consistently measured at less than 0.025mg/l (Figure A2.8), although still repeatedly fails the EC FFD mandatory requirements for both ammonium and un-ionizes ammonia.

Historically there were distinct spatial variations in the concentrations of total ammonia in the MSC. Prior to 2000 the highest concentrations were frequently measured at Irlam Locks which is located downstream of Eccles and Davyhulme WwTW (Figure 1.2). Substantial improvements have been observed at this EA monitoring site and concentrations of total ammonia have been in closer agreement with the remainder of the MSC for the last 6 years, giving a more homogenous and lower ammonia concentration throughout the MSC.

In 2006 the River Irwell contributed nearly all (97%) of the ammonia load to the upper MSC (Appendix Section 3.). This has increased as a proportion of the total load entering the upper MSC from 86% (based on data gathered between 1983 and 1987; APEM, 1990b). Despite this percentage increase, the mean daily load has almost halved from 4256 kg/day (from 1983 to 1987) to 2185 kg/day (in 2006). Clearly this is a substantial reduction in the ammonia load entering the MSC, although it still fails to allow compliance with the imperative levels for total ammonia and un-ionised ammonia required by the EC FFD.

Another important aspect of ammonia concentration concerns nitrogen cycling. Nitrosomonas sp. bacteria play an important role in this, oxidizing ammonia to nitrite. Then Nitrobacter bacteria, convert nitrite to nitrate. Importantly, this bacterial oxidiation of ammonia strips oxygen from the water column, adding to the DO problem caused by BOD. Typically this is responsible for around 10% of the combined oxygen demand on the system (North West Water Authority 1997). However, under certain conditions nitrite concentrations can build up. This is caused by environmental conditions such as low DO differentially affecting the latter bacteria (Nitrobacter) preventing conversion of nitrite to nitrate before Nitrosomonas sp. is affected. As a consequence, nitrite concentrations routinely exceed the FFD guideline value of <0.03mg/l for designated cyprinid waters.

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20 Irwell Salford (Harper, 2000a) d/s Barton Locks (Harper, 2000a) 18 Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) Latchford Locks (Harper, 2000a) 16 River Irwell at Foot Bridge at Salford University MSC below Barton Locks MSC at Irlam Locks 14 MSC at Latchford Locks Mersey at Howley Weir 12

10 (mg/l) 4 NH

0 1972 1973 1974 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

Figure 1.2 Ammonia annual averages in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Appendix Section 2.

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2.3 Dissolved Oxygen

Dissolved Oxygen (DO) is perhaps the single most important determinand to the overall health of the biota, as anoxic conditions results in catastrophic ecological consequences. Low DO has historically been a major issue in the MSC, with periodic total water anoxia causing large scale fish kills, and largely prevents the passage of salmon through the MSC to the on line river catchments for prolonged periods during the warmer months.

Considerable investment in the treatment processes at the WwTWs have helped to reduce organic pollution in the MSC over the previous decades, but low DO continues to be recorded during dry weather flows as the effluents are not diluted to the same extent as during higher flows. These conditions can be exacerbated by wet weather events introducing high concentrations of effluents from combined sewage overflows (CSO’s). The influx of untreated effluent and associated high BOD and ammonia are likely to result in low dissolved oxygen events and potentially cause fish kills.

Aside from these episodic pollution events, low DO in the MSC occurs as a result of the combined oxygen demands from the BOD of the water column, oxidisation of ammonia and from the sediment oxygen demand. The comparatively high base pollution load from the inflowing waters create severe DO stress when it reaches the Canal. The structure of the MSC slows flow and reduces the type of aeration occurring naturally arising from turbulent flow of the upstream river systems. This is clearly apparent in Figure 1.3. when comparing relatively high DO at the site ‘Irwell at Salford’ with the low DO from that downstream of Barton Locks.

Furthermore, the near vertical walls of the Canal and the depth (up to 9m) means that it stratifies readily during quiescent still conditions with little wind. On warm, sunny days thermal stratification results in the formulation of a thermocline (1oC difference in water temperature over 1m depth). This results in effective layering of the water column temperature inducing density differences at depth. The warmer, lighter water floats on top of the cooler denser water and considerable wind energy is required to break down the thermocline (Hendry 1991). In effect, the deeper cooler water becomes isolated from the surface and hence cannot replenish oxygen concentrations from atmospheric diffusion (via surface air). Under these conditions, a combination of water column and sediment oxygen demands rapidly remove all oxygen from the bottom water, resulting in total anoxia. The influence of SOD in this process is illustrated at Salford Quays, where the enclosed basins isolated from polluted water from the MSC have still experienced bottom water anoxia during periods of Helixor breakdown. This occurs in the absence of any ‘real’ water column BOD and again highlights the importance of understanding the processes that occur in this highly modified system. This, again, provides an indication of the importance of the Salford Quays data sets to the modelling of MSC water quality.

A mass flux analysis of the relative load of oxygen from the major river inputs was carried out both in the 1990(b) APEM review using data from 1983 to 1987 and as part of the current review using data from 2006. A comparison of these shows that there have been some minor improvements in the DO over the last twenty years (Appendix Section 3.). Further to this, each pound in the MSC below Mode Wheel

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Locks has repeatedly failed to achieve concentrations of dissolved oxygen greater than the standard of 4 mg/l which is required for compliance with the FFD. Above Mode Wheel Locks, artificial oxygenation by specifically designed units (as discussed previously) maintain DO above a 4mg/l target.

Much of the data discussed from below Mode Wheel Locks consists of surface values of DO only. In fact the EA’s sampling program of the MSC only includes surface measurements, which may lead to false interpretations of the Canal’s condition. Profile measurements are much more meaningful, as the processes occurring immediately above the sediment surface are of equal and 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 units in order to maintain oxygen in the Turning Basin above 4mg/l, whilst minimising oxygenation costs (Appendix Section 2.3). Four control sites at Pomona show how, without the influence of oxygen injection, bottom water anoxia frequently occurs. Equally, during periods of oxygen unit malfunction, oxygen levels have quickly fallen below the 4mg/l target. An example of this was in May 2006 where DO levels fell below 1mg/l in some parts of the Turning Basin during oxygenation unit failure.

Very little oxygen profile data is available below Mode Wheel Locks and therefore the extent of bottom water anoxia has not been recorded. The only data that exists is from APEM’s monitoring of DO following a fish kill event in 2006 between Mode Wheel and Barton Locks.

Bottom water oxygen was recorded below 3mg/l whilst surface values approached 20mg/l (>200% saturation). This is some of the strongest evidence yet of intense algal activity in the surface waters fuelled by excessive phosphorous concentrations.

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 the ecology, particularly fish. This therefore highlights the importance of the data from continuous monitoring sondes located at three of the routine EA monitoring sites, which record DO at 15 minute intervals. These are an important tool in understanding diurnal fluctuations in dissolved oxygen which are usually missed by spot sampling during the day (Appendix Section 2.3.5.). The low DO that caused the fish kill downstream of Mode Wheel lock in May 2006 would not have been record without the aid of the continuous monitoring sonde.

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Irwell Salford (Harper, 2000a) 160 d/s Barton Locks (Harper, 2000a) Irlam Locks (Harper, 2000a) Howley Weir (Harper, 2000a) 140 Latchford Locks (Harper, 2000a) Woolston Weir (Harper, 2000a) River Irwell at Foot Bridge at Salford University 120 MSC below Barton Locks MSC at Irlam Locks MSC at Latchford Locks 100 Woolston Weir Mersey at Howley Weir

80 Dissolved oxygen (%) 60

0 1972 1973 1974 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

Figure 1.3 DO (%) annual averages in the Manchester Ship Canal since 1974, adapted from Harper (2000a). Data post 2000 provided by routine EA monitoring as detailed in Appendix Section 2.

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2.4 Suspended solids and transparency

Suspended solids are an important water quality parameter in the EC Freshwater Fish Directive (EC FFD). High concentrations can be damaging to fish habitats and populations as they can clog fish gills, decrease resistance to disease, reduce growth rates and prevent egg and larval development. The FFD therefore stipulates that guideline concentrations of suspended solids should remain below 25 mg/l. The canalisation of the Rivers Irwell, Irk and Medlock as they form the MSC, results in a slowing of the water velocity. This, in turn results in the settling out of sediments and particulate matter.

However, suspended solids have a much more important role in the MSC than direct effects on fish health alone. The continual supply of suspended solids to the Canal (much of it thought to originate from the WwTW) and the gradual reducing flow keep the finer particulate pollutants in suspension (Montgomery, 1988). In contrast the isolated Salford Quays do not have through flow or the continual introduction of new sediments and therefore suspended solids in Salford Quays during 2006 had a mean annual value of just 3.64 mg/l, whereas they were a much higher 20.4 mg/l in the MSC. Correspondingly, the secchi extinction depths are also considerably lower in the MSC than those seen in the enclosed Salford Quays basins. For example in recent years secchi depth in the MSC has typically been less than 1m, but up 3-5m in the Quays.

Thus suspended solids in the MSC resulting from the high concentrations of sewage derived organic matter affect the water’s transparency. Hence, despite the high concentrations of phosphorus in both dissolved and particulate form in the MSC (as discussed in the nutrients section below), the MSC cannot be classified as hypereutrophic since the light transmittance is a limiting factor to phytoplankton growth. However, as mentioned previously, indications are that algal blooms are becoming more commonplace.

It is known that suspended solids play an important role in the limited transparency of the MSC, however it is possible that dissolved solutes such as peaty organics may also be responsible for colouration of the water. It is important to differentiate and hence it is suggested that that colour tests are undertaken on samples gathered from the MSC to determine whether the dissolved or particulate matter are of greater significance in controlling light attenuation.

2.5 Nutrients (Phosphorus)

The MSC contains high concentrations of phosphorus which are mainly derived from industrial and sewage effluent. Concentrations of both total phosphorus and orthophosphate have been measured upstream of Mode Wheel Locks at APEM monitoring sites. 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 underestimation of the total phosphorus available for algal uptake (ie in filtered samples, algal cells containing phosphorous are removed but may contain much of the available phosphorous). 17

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The MSC routinely has concentrations of total phosphorus in excess of 1,000 µg/l, therefore according to the OECD classification this waterbody has the potential to be hypereutrophic. However, as discussed previously the suspended solids and associated limited transparency mean that despite high nutrient concentrations, the growth of algal populations is limited by light penetration through the water column. For the MSC to be considered hypereutrophic according to its chlorophyll a content, annual mean concentrations would need to be measured in excess of 25 µg/l. In fact the concentrations measured upstream of Mode Wheel Locks at APEM Sites 1 and 10 are closer to 10 µg/l (Appendix Section 4.), although recent occasional elevated levels have been recorded (e.g. 30 µg/l).

The interaction between available nutrients and algal productivity is of great importance to the future water quality of the MSC. The history of algal activity in Salford Quays following isolation provides important insight into this. The isolation of the Quays immediately stopped the influx of organic matter from the inflowing waters and as a result dramatically reduced suspended solids concentration. The associated increase in water clarity triggered a huge increase in algal productivity which occurred because algal cells were now provided with ample sunlight as well as high levels of phosphorous from the bottom sediments. This caused significant problems in the early 1990s as total phosphorous levels over 800 µg/l led to extremely high chlorophyll concentrations reaching a peak of 800µg/l in 1993 (compared to more typical 30 µg/l in the MSC). The blue green algal species Oscillatoria was the dominant taxa during the period following isolation and is able to fix phosphorous from the bottom sediments.

Despite severity of these initial algal blooms, the vigorous mixing system installed in the Quays has controlled the release of phosphorous from the bottom sediments. Oxidisation of the sediments interstitial layer has effectively locked away the previously available phosphorus, and had a hugely beneficial impact upon the Quays. While this form of algal control has been effective in the Quays, it would not be applicable to the MSC. Since the MSC is an open system, locking away phosphorous through sediment oxygenation is unlikely to be achievable, due to the continual input of organics from upstream. As such, other approaches to control nutrient release from the sediments will have to be found.

Nitrogen, in the form of Nitrate, is also an essential nutrient for algal growth. However, in freshwaters it is seldom limiting and indeed the concentrations found in the MSC (typically over 3mg/l) indicate that it is in plentiful supply to fuel algal growth.

2.6 Bacteriology

Organisms that can cause disease or illness to other species (including humans) are known as pathogenic. Gastro-enteritis is the main illness associated with these pathogens and has been linked to a range of micro-organisms including bacteria (such as Escherichia coli, Campylobacter, Salmonella and Shigella) and protozoa (Entamoeba and Giardia). In 1976 The EC Bathing Waters Directive (76/160/EEC) became one of the first pieces of European environmental legislation aimed at 18

Final Report – September 2007 APEM Scientific Report 410039 providing a regulatory framework to reduce the concentration of these pathogens to acceptable levels. The MSC and Salford Quays are not currently designated as EC Directive bathing waters although an application for official recognition under the Directive is underway for the Quays. Nevertheless, the directive offers a useful yardstick against which pathogenic bacteria contamination from sewage can be assessed.

The waters within the MSC contain sewage which is likely to contain pathogenic micro-organisms excreted by humans. Although much of the effluent receives some treatment by United Utilities before disposal to the river, the aim of the treatment is mainly to reduce the level of biochemical oxygen demand (BOD), ammonia and suspended solids. Therefore considerable levels of bacteria and viruses can remain in the discharged treated sewage effluent.

The continual supply of pathogenic organisms to the MSC is ongoing and is monitored by APEM upstream of Mode Wheel Locks to provide control data for Salford Quays where many water sport activities are practiced. Routine monitoring from these control sites of both faecal and total coliforms in the MSC consistently indicate that cell counts are present at levels greater than the limit of detection (>20,000 cells per 100 ml). These levels far exceed those required for mandatory compliance of the EC Bathing Water Directive (95% of samples must not exceed 10,000 total coliforms per 100 ml and 2,000 faecal coliforms per 100 ml). The implications are that from a public health perspective, extreme caution should be exercised when considering any kind of water contact activity in the Canal.

2.7 Other data

2.7.1 Metals

Total zinc and dissolved copper both have toxic effects on aquatic ecology including fish. The importance of these metals is recognised in the EC FFD levels for total zinc and dissolved copper have been set as ≤1.0 mg/l (mandatory level) and ≤0.04 mg/l (guideline level) respectively for cyprinid fish. Measurements of these parameters in the MSC have been very limited with the only data coming from surveys being undertaken by APEM in the 1980’s. Concentrations of total zinc and dissolved copper at this time were less than the stipulated imperative levels, although it is considered that these measurements are too limited to characterise the current conditions in the MSC.

In addition to dissolved metals in the MSC, it is known that high concentrations of metals are contained within the sediments (see Section 2.8).

2.7.2 pH

The pH of the MSC is an important parameter due to its effect on ammonia and the subsequent toxicity implications for fish. An increase in pH can result from algal activity utilising carbon dioxide in the water, altering the carbon dioxide - hydrogen carbonate balance in the water. Although this is not a problem in itself, it can affect 19

Final Report – September 2007 APEM Scientific Report 410039 the equilibrium of ammonium. A higher pH (together with higher temperatures) creates the potential for a greater proportion of total ammonia within the water to be present in the more toxic un-ionised form. This un-ionised form is several orders of magnitude more toxic to fish than the ionised form.

Measurements of pH are routinely taken in all pounds within the MSC and the pH has largely remained within the range of 6 to 8 (and within the stipulated pH 6 to 9 in the EC FFD). However, on occasion pH has risen to 8.9 upstream of Mode Wheel Locks in Basin 6, which may be associated with increased algal activity. Continuous monitoring sondes located in three of the pounds (Appendix Section 2.3.5.) monitor pH at 15 minute intervals therefore acting as a proxy for high algal productivity.

2.7.3 Conductivity

Conductivity of water is related to the concentration of dissolved ions and in general terms acts as a surrogate for the amount of dissolved solids. Routine measurements of conductivity have been taken throughout the MSC since 1989 and are also measured on a 15 minute interval with three continuous monitoring sondes by the EA. Conductivity was consistently within the range of 200 and 900 µS/ downstream of Mode Wheel Locks. However, lower measurements were recorded within the Turning Basin area, reflecting lower dissolved solids, possibly associated with the sewage discharges downstream.

2.7.4 Residual chlorine

Chlorine is utilised during processing at the WwTW as a disinfectant and along with other industrial discharges, acts as a source of Chlorine. It can be toxic to aquatic life and as such, limits under the EC FFD are imposed (<0.005mg/l). Measurements of residual chlorine are not known to have been taken previously from the MSC.

2.8 Sediments

Industrial and WwTW derived organic-rich pollutants suspended within the inflowing river water continually enter the MSC (Montgomery, 1988). As the inflowing waters reach the canalised MSC where velocities reduce dramatically, these particulates settle out and accumulate on the bed. This occurs throughout the MSC, but specific areas, such as the Turning Basin at Salford Quays, experience high levels of deposition and require periodic dredging by the Manchester Ship Canal Company in order to maintain navigation and prevent flooding.

The polluted nature of the particulate load has resulted in nutrient rich and contaminated sand and silts comprising the sediment layer at the bottom of the Canal. Due to the high organic content of the sediment material the MSC has a history of associated problems including floating sediment mats and bottom water anoxia. In addition, generation of hydrogen sulphide and methane creates foul odours (Hendry, 1991) related to the resuspension of either the sediment itself or gases produced within the sediment layer (White et al., 1993; Boult & Hendry, 1995).

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The interactions between the sediment and water play an important role in determining overall water quality within the MSC. The greatest direct impact upon the overlying water chemistry is the sediments potential to strip dissolved oxygen out of the water column, which is known as the sediment oxygen demand (SOD). The SOD in the Ship Canal is known to be high from surveys carried out by APEM using sediment cores in 1999 (APEM, 1999) and subsequently by using a more sophisticated SOD chamber which takes insitu measurements. The latter measurements are of greater accuracy than those undertaken using sediment cores due to the measurements being taken insitu, rather than taking samples to a laboratory for analysis with inherent inaccuracies in relation to disturbance and overlying water quality.

SOD therefore has an extremely important influence on Ship Canal water quality and combined with high periods of BOD, can cause anoxia throughout the water column. Controlling the influence of sediments is an extremely difficult task, but one that has been achieved in the enclosed basins of Salford Quays. Here, mixing units have been installed to prevent stratification and maintain high levels of dissolved oxygen throughout the water column. Since oxygen rich waters are constantly present, an oxidised layer at the sediment water interface eventually develops and effectively creates a barrier to the release of phosphorus and other chemicals/metals within the sediment. This also has implications for the sediment oxygen demand as it reduces the potential for sediment to strip oxygen from the water column.

In the MSC Turning Basin DO levels are maintained above 4 mg/l by oxygenation injection. It is not known what effect oxygen injection will have on the more substantial SOD over the long term. It is debatable weather any significant reduction will be apparent due to the continual ‘rain’ of organic material and the anoxic nature of the interstitial waters within the sediment itself.

As well as the impact upon oxygen, sediments are also important because of its high nutrient content, which when leached into the overlying water, provides an almost endless supply of nutrients for algal growth. In addition severe metal contamination from historic industrial effluents inputs and shipping activities (including anti-fouling paints) remains within the sediment layers of MSC and can cause problems for fish and the ecology as a whole. Indeed metal contamination presents significant problems due to release into the water column of the Ship Canal under anoxic conditions. This presents a potential problem for aquatic biota through bioaccumulation of heavy metals. APEM (1989b) found that zooplankton and chironomid larvae may have bioaccumulated zinc and lead which was subsequently bioaccumulated by stickleback (which graze on zooplankton and chironomids). Although metal contamination generally had little impact upon other fish species, more recent investigations in the MSC above Mode Wheel Locks found Bioaccumulation of heavy metals to be a problem for invertebrate species (Bassett 2005) and clearly raises concern for ecology.

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2.9 Key findings

Oxygen, BOD and ammonia in the MSC continue to fail the Freshwater Fish Directive requirements despite improvements in the water quality over the last twenty years of monitoring.

Periods of anoxia are generally undetected by surface sampling of DO. The only section of the MSC in which routine profile measurements are undertaken are upstream of Mode Wheel Locks. These intensive surveys throughout the summer months provide a valuable long term dataset which is not available for any other section of the MSC.

Water column anoxia is seen both following sustained periods of hot dry weather and following CSO spills.

The sediment oxygen demand is a key factor in the total water column oxygen demand and should be considered as an important mechanism for stripping oxygen from the water column.

Nutrient concentrations have remained high in the MSC, leading to significant potential for substantial algal blooms.

High suspended solids and low transparency limit algal growth within the MSC. Improvements to effluent inputs to the MSC in future may improve the water clarity but increase the potential for algal blooms.

Increased algal activity will elevate pH, which in turn will cause the more toxic un-ionised form of ammonia to predominate with potentially serious consequences for fish populations.

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3.0 REVIEW OF MSC BIOLOGICAL DATA

3.1 Historical review of macro-invertebrate data

The most extensive macro-invertebrate data within the MSC comes from the work carried out by APEM in Salford Quays and in the MSC above Mode Wheel lock from the late 1980s to the present day (beginning with Hendry (1987). Some additional data preceding the APEM data set is from the North West Water Authority (1988)). Along side these data sets, the Environment Agency has carried out invertebrate sampling of some of the major river inflows to the MSC, but not the Canal itself.

3.1.1 Upper MSC

APEM have collected monthly samples from two sites in the MSC since May 1990 using ‘standard colonisation units’ (SUC’s). Qualitative samples were also collected between August 1986 and September 1988 using other techniques including an Ekman grab, hand net sweep and stone scrapings.

Initial samples (1986-1988 and 1990-94) at the two sites were seen to contain relatively few species known to be relatively tolerant of organically enriched conditions and associated low levels of dissolved oxygen (eg. leeches (Erpobdellidae) and non-biting midge (Chironomidae)). During the period from 1994-2000 additional organisms were recorded, including pollution sensitive taxa such as the mayflies (Heptageniidae) and caddis flies (Phryganeidae). By 2003 notable changes include the collection of several molluscan species including members of the Hydrobiidae, Planorbidae and Sphaeridae families.

An increase in macro-invertebrate diversity was therefore evident from the samples collected at the two MSC sites. These changes have most likely occurred due to an improvement in water quality as several of these recently discovered organisms are known to be sensitive to organic pollution. The major driver for improvements has come from the oxygen injection system installed in 2001, which has had a profound impact upon the species diversity observed, shown by comparison between the oxygenated and control sites.

Macroinvertebrate data from the MSC is also provided from a number of degree and masters theses supervised by APEM ltd (Fan, 1996; Litton, 1996; Govan, 2003 and Bassett, 2005). In 1996 Litton and Ming Fan both reported that the invertebrate community in the upper reaches of the MSC was composed of only pollution tolerant species i.e. Asellus sp., supporting the findings of Hendry et al. (1997).

However, after the installation of the oxygen units into the upper reaches of the MSC in 2001, Govan (2003) reported a noticeable increase in invertebrate diversity at some sites with a decrease in the abundance of the pollution tolerant species found previously (Figure 3.1).

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Number of Invertebrate Taxa in the Upper Manchester Ship Canal

45 Oxygenation

30 Oxygenation trials 25

Number of Taxa 15

1990-1991 1991-1992 1992-1993 1993-1994 1994-1995 1995-1996 1996-1997 1997-1998 1998-1999 1999-2000 2000-2001 2001-2002 2002-2003 2003-2004 2004-2005 2005-2006 Figure 3.1. Total number of macro-invertebrate taxa recorded in the MSC from 1990 to 2006.

In 2005 Bassett investigated the concentrations of manganese, zinc, copper and lead in the sediment and also the tissues of two genera of invertebrate (Asellus and Erpobdella) and gudgeon (Gobio gobio) from five sites on the upper reaches of the MSC and the lower reaches of the River Irwell. Bassett found that at Site 2, situated within the Turning Basin of the MSC, higher concentrations of lead, zinc and copper were found within the sediment and invertebrates compared to the other sites. This is clearly important from a bioaccumulation perspective to the overall ecology of the MSC and demonstrates a potential impact of heavy metal pollution not previously noted.

3.1.2 River Inputs

Macro-invertebrate sampling has been carried out by the Environment Agency at six sites on tributaries of the Manchester Ship Canal (MSC) from as early 1985. Three minute kick samples were taken and invertebrates were identified to family level to allow for the calculation of Biological Monitoring Working Party (BMWP) score and Average Score Per Taxon (ASPT). The Number of Scoring Taxa (NST) were also given. However, no such data is available for the MSC, as the sampling technique in inappropriate for deeper waters.

The BMWP system has been the accepted index for assessing pollution stress in rivers using macro-invertebrates in the United Kingdom since the early 1980s. Although it will detect a wide range of aquatic stressors, the index is primarily based on organisms’ sensitivity to organic pollution. (Further details of the BMWP classification system are given in Appendix Section 4.1).

A pristine salmonid river might be expected to have a BMWP score of over 150 in the UK with an ASPT of 6. A typical cyprinid river subject to little organic pollution will 24

Final Report – September 2007 APEM Scientific Report 410039 have a BMWP score within the region of 80 and an ASPT score of 4. Conversely, heavily polluted rivers would be expected to score poorly, with a BMWP of less than 10 and ASPT of less than 3.

The early records from each site showed the macro-invertebrate diversity to be very poor. BMWP scores as low as 2, a sample in which only non-biting midges (Chironomidae) were found, were recorded on one occasion in the Salteye Brook downstream of Eccles treatment works. Fauna at all sites was restricted to a few specimens of Oligochaete worms, Chironomidae, and freshwater hog-louse (Asellidae), all of which are tolerant to highly organic conditions and associated low oxygen concentrations.

The universally poor BMWP and ASPT scores recorded in these watercourses in the 1980s were seen to improve during the early 1990s. The biotic scores of samples in Salteye Brook and Red Brook appear to improve after 1991, albeit only briefly in the former, with ASPT scores regularly exceeding 3 for the first time since records began. A second staged improvement was recorded in 1997 in Salteye Brook. Samples taken in the River Medlock, River Glaze and River Mersey at Flixton Bridge show also show an increase in BMWP and ASPT scores after 1992.

While there appears to be an improvement in the communities at each site, even those samples taken most recently would be considered to be poor in terms of biodiversity, and are comprised largely of pollution tolerant taxa. These results would suggest that the MSC inflowing rivers sites are still highly organically enriched and are likely to suffer from low levels of dissolved oxygen if only periodically.

The Riverine InVertebrate Prediction And Classification System (RIVPACS) is also used to compare the macro-invertebrate communities in a site to those that might be expected if it were in pristine condition. Using the RIVPACS methodology, the macro-invertebrate communities are compared to those that might be found, given the habitat, in an unpolluted system. The ratios generated are used by the Environment Agency to determine the biological General Quality Assessment (GQA). These GQA grades range from ‘a’ (very good) to ‘f ‘(bad).

Table 3.1 shows the biological GQA grades for the six sites upstream of the MSC. It can be seen that recent improvements were recorded over the 17 year period in all but one of the six watercourses. The greatest improvements were recorded in Red Brook and the River Medlock, however all were graded either bad (f), poor (e), or fair (d) at best. Salteye Brook, having improved in 2000, was actually considered to have deteriorated in 2002-4. Unfortunately the latest GQA has not been calculated for three of the sites, Salteye Brook being one of them, but further improvement might be expected.

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Table 3.1. Historical Biological General Quality Assessment (GQA) Grades

Site 1990 1995 2000 2002-4 2005-7 River Mersey, Bollin Point f f f f e Salteye Brook downstream of Eccles f f e f No ETW, ptc MSC data Red Brook upstream Partington road f e f d No bridge data River Medlock upstream Dawson f e e d No Street data River Glaze ptc MSC, downstream of f e e e e the A57 River Mersey, Flixton Bridge f e e f e

3.1.3 Salford Quays

When sampling first commenced in Salford Quays in 1986 the diversity and abundance of macro-invertebrates was poor at all sites within both the Quays and the MSC, reflecting poor water quality.

There was initially little response in the invertebrate community following the implementation of the water management strategy in Salford Quays (1987) and no differences between the invertebrate fauna in the open MSC and closed basin at Salford Quays were apparent, both being dominated by pollution tolerant taxa. Following this initial period, artificial reefs and macrophytes were introduced to provide an increased number of niches for invertebrates to colonise within the Quays. As the quality of water improved, species richness increased and by 1997 the enclosed basins were found to support 29 invertebrate taxa, many of which were species indicative of improving water quality (Hendry et al., 1997). This was a huge improvement on the nine species found ten years earlier. Today the Quays support over 50 taxa showing continued water quality improvement and habitat diversity.

As is the case for water quality and discussed earlier, Salford Quays acts as a test bed model for future improvement in ecology that may occur within the MSC in years to come, demonstrating the hugely beneficial impact of removing organic pollution and alleviating oxygen stress. The data set generated from the quays will form a large component of the input data for the ecological model for the MSC.

3.2 Historical review of algal data

Algal data from the MSC and Salford Quays comes from APEM’s regular monitoring of Salford Quays (since 1987), which includes two sites within the MSC (Sites 1 and 10). In this sampling program analysis for species composition and chlorophyll a concentration is carried out. Earlier sampling of algal populations within the MSC and Salford Quays was carried out as part of water quality monitoring between 1986 and 1988 (North West Water Authority, 1988a & b).

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As discussed in Section 1.10, the MSC has the potential to become hyper eutrophic due to the high nutrient concentrations in its waters, but the turbidity prevents light penetration and inhibits algal growth. Historical algal data is therefore very important, and the knowledge gained from the isolation of Salford Quays provided a vital data source to assess what might happen in the MSC should water clarity increase via improved wastewater treatment.

The earliest sampling of the MSC and Salford Quays showed that the species composition reflected highly eutrophic conditions, with high proportions of pollution tolerant taxa. This was the case for both the open and closed basins as there was initially very little difference in the phytoplankton density and species composition between the two.

Following this initial period, the MSC and Salford Quays have displayed very different patterns in species present and algal abundance. At APEM Site 10 in the MSC, chlorophyll a concentration has generally been below 30 µg/l, with occasional summer peak of up to 200 µg/l (in 1995). Conversely in Salford Quays, chlorophyll a concentration displayed a steadily rising trend from 1987 to 1993, where it peaked at over 800 µg/l. As described earlier, throughout the following years chlorophyll a generally declined, although periodic peaks continued up until 2001. Since 2001 algae in the Quays has remained stable and at a low level (generally below 30 µg/l).

Salford Quays in the early 1990s therefore displayed algal response to a reduction in suspended solids. The nutrient content of the water (sediment derived) combined with increased light penetration as the waters of Salford Quays cleared, resulted in high algal productivity. Algal density and associated chlorophyll a concentration was much higher in the Quays during this period compared with the control site in the MSC despite phosphorous levels in the Canal being much higher. Algal productivity continued to be limited by high suspended solids in the MSC as a result of continued turbid inflow from the River Irwell as well as dredging activities in the Turning Basin.

Algal abundance in the Quays was eventually controlled by the indirect action of the Helixor destratification system within the enclosed basins. Vigorous mixing distributes oxygen rich water throughout the water column, and over several years an oxidised layer built up on the sediment surface. This oxic layer acted as a barrier to the release of nutrients from the polluted sediments, thus reducing nutrient release from the sediments and hence limiting algal productivity. The history of algae in the Quays highlights important issues for the current MSC investigation and shows the potential problems that may arise from reducing suspended solids and increased water clarity.

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3.3 Key Findings

• The Invertebrate community in the MSC generally reflects poor water quality, although species diversity has increased in recent years.

• The oxygen injection units have had a beneficial effect upon invertebrate species composition above Mode Wheel Locks illustrating what might be achieved by alleviating oxygen stress.

• Salford Quays currently has an invertebrate community that reflects the competitively pollution free conditions compared to the MSC, illustrating the future ecological potential in the Canal.

• After separation of the MSC and Salford Quays there was initially very little difference in the phytoplankton biomass and diversity between the two water bodies.

• In Salford Quays an increase in water clarity led to a period of high algal productivity, punctuated with extremely high peaks during the summer months. In recent years algal population has stabilised and chlorophyll a has remained low by controlling the release of phosphorous from the sediments.

• Algal productivity in the MSC has remained low in comparison to the Quays due to high turbidity limiting light penetration.

• There is evidence of occasional high algal productivity in the MSC during dry, still conditions giving an indication as to what might be anticipated in future years should water clarity improve.

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