2.9.0 Water Management
2.9.1 Background
Water management within the Medina includes wastewater management, the monitoring of water quality and the management of potential oil spills.
Wastewater management: Improvements in wastewater management within the Medina Estuary have occurred during the 20th century. A major development in 1935 was the construction of a primary sewage treatment works (STW) at Fairlee. Further improvements occurred in the 1970s when monitoring by Southern Water (SW) indicated that further improvements in sewage treatment were necessary. A major investment programme was instigated and the STW at Fairlee was rebuilt to incorporate new inlet works, storm holding tanks, secondary biological treatment, sludge treatment and the extension of the discharge pipe into the deep water channel of the estuary with the aim of ensuring that, even at low tide, the effluent was dispersed rather than being deposited on mudflats. Associated with the new plant was a sealing of unsatisfactory storm overflows and a new overflow sited at Town Quay, Newport. The Fairlee plant is presently the Island's largest sewage treatment works, until Sandown is operational (End 2000), and has consent from the EA to discharge up to 12,115 m3 per day into the estuary.
Wastewater management at Cowes was not tackled until the 1980s. A scheme was adopted in 1985 to provide preliminary treatment for effluent from Cowes with treated effluent being discharged into the deep water of the Solent from a outfall off Old Castle Point. The EU Designated Bathing Beach at West Cowes, which had consistently failed tests every summer, now passes all tests, providing evidence of significant improvements in water quality.
Sewage treatment on the Island has been reviewed by Southern Water which has applied for consents to develop a treatment works in Sandown to treat much of the Island’s wastewater before discharging effluent into the English Channel, to conform to European Directives. Wastewater from Cowes, East Cowes, Gurnard and Norton will be part of this scheme with wastewater being pumped across the island.
The Fairlee works will continue to operate and will treat wastewater from Newport, Porchfield, Whitecroft Hospital, Havenstreet and Wootton. There are also a number of small wastewater treatment works (population >2000) which will remain operational.
All the Island’s sludge will be transported to Sandown where it will be digested, dried and sold to farmers.
The Medina crossing will use trenchless technology reducing any disturbance to the estuary bed. The works at Sandown, aim to be operational before the end of 2000.
Other discharges of wastewater into the estuary include wastewater from storm overflows, run off from roads etc. and wastewater from private treatment works and recreational craft. Map 9 illustrates the present points of discharge within the estuary. (Please note that the sea outfall north of the Shrape will no longer be used once Sandown Treatment Works are operational.)
Water quality monitoring: The EA have three main sampling points, at Newport Harbour, the Folly and the main pontoon in West Cowes, with interim sites scattered around the estuary. The EA report that there are no significant water quality problems. Monitoring of oyster quality is also carried out by Environmental Health Officers from the Isle of Wight Council who sample oysters to grade shellfish harvesting areas depending on the levels of bacteria. This determines the level of treatment the oysters require before they are fit for human consumption. Water samples are also taken to detect dangerous algal blooms.
Management of potential oils spills: The estuary is vulnerable to potential pollution from a tanker incident in the wider Solent and to oil tank ruptures in East Cowes. Oil spill plans exist for the Solent, Isle of Wight, Cowes Harbour and Newport Harbour to provide emergency action in the event of a spill.
Regulation: The EA has a duty conferred by the Water Resources Act 1991 to maintain and protect the water quality in controlled waters. Its duty includes the setting of water quality standards, controlling all discharges of wastewater from sewage works and industry, monitoring water quality and taking corrective action, and taking action to reduce the risk of pollution incidents.
Cowes Harbour bye-laws state that no person shall discharge sewage or other pollution into the Harbour when moored to areas that have access to the shore.
2.9.2 Issues
2.9.2.1 Wastewater management
Despite the improvements in water quality, there are a number of remaining issues regarding effluent disposal. At present, heavy rainfall results in storm discharge (approximately twice a month) of effluent which has only been subject to primary treatment. There are also continuing concerns about the private treatment works which have consents from the EA to discharge wastewater into the estuary.
2.9.1 Background
Water management within the Medina includes wastewater management, the monitoring of water quality and the management of potential oil spills.
Wastewater management: Improvements in wastewater management within the Medina Estuary have occurred during the 20th century. A major development in 1935 was the construction of a primary sewage treatment works (STW) at Fairlee. Further improvements occurred in the 1970s when monitoring by Southern Water (SW) indicated that further improvements in sewage treatment were necessary. A major investment programme was instigated and the STW at Fairlee was rebuilt to incorporate new inlet works, storm holding tanks, secondary biological treatment, sludge treatment and the extension of the discharge pipe into the deep water channel of the estuary with the aim of ensuring that, even at low tide, the effluent was dispersed rather than being deposited on mudflats. Associated with the new plant was a sealing of unsatisfactory storm overflows and a new overflow sited at Town Quay, Newport. The Fairlee plant is presently the Island's largest sewage treatment works, until Sandown is operational (End 2000), and has consent from the EA to discharge up to 12,115 m3 per day into the estuary.
Wastewater management at Cowes was not tackled until the 1980s. A scheme was adopted in 1985 to provide preliminary treatment for effluent from Cowes with treated effluent being discharged into the deep water of the Solent from a outfall off Old Castle Point. The EU Designated Bathing Beach at West Cowes, which had consistently failed tests every summer, now passes all tests, providing evidence of significant improvements in water quality.
Sewage treatment on the Island has been reviewed by Southern Water which has applied for consents to develop a treatment works in Sandown to treat much of the Island’s wastewater before discharging effluent into the English Channel, to conform to European Directives. Wastewater from Cowes, East Cowes, Gurnard and Norton will be part of this scheme with wastewater being pumped across the island.
The Fairlee works will continue to operate and will treat wastewater from Newport, Porchfield, Whitecroft Hospital, Havenstreet and Wootton. There are also a number of small wastewater treatment works (population >2000) which will remain operational.
All the Island’s sludge will be transported to Sandown where it will be digested, dried and sold to farmers.
The Medina crossing will use trenchless technology reducing any disturbance to the estuary bed. The works at Sandown, aim to be operational before the end of 2000.
Other discharges of wastewater into the estuary include wastewater from storm overflows, run off from roads etc. and wastewater from private treatment works and recreational craft. Map 9 illustrates the present points of discharge within the estuary. (Please note that the sea outfall north of the Shrape will no longer be used once Sandown Treatment Works are operational.)
Water quality monitoring: The EA have three main sampling points, at Newport Harbour, the Folly and the main pontoon in West Cowes, with interim sites scattered around the estuary. The EA report that there are no significant water quality problems. Monitoring of oyster quality is also carried out by Environmental Health Officers from the Isle of Wight Council who sample oysters to grade shellfish harvesting areas depending on the levels of bacteria. This determines the level of treatment the oysters require before they are fit for human consumption. Water samples are also taken to detect dangerous algal blooms.
Management of potential oils spills: The estuary is vulnerable to potential pollution from a tanker incident in the wider Solent and to oil tank ruptures in East Cowes. Oil spill plans exist for the Solent, Isle of Wight, Cowes Harbour and Newport Harbour to provide emergency action in the event of a spill.
Regulation: The EA has a duty conferred by the Water Resources Act 1991 to maintain and protect the water quality in controlled waters. Its duty includes the setting of water quality standards, controlling all discharges of wastewater from sewage works and industry, monitoring water quality and taking corrective action, and taking action to reduce the risk of pollution incidents.
Cowes Harbour bye-laws state that no person shall discharge sewage or other pollution into the Harbour when moored to areas that have access to the shore.
2.9.2 Issues
2.9.2.1 Wastewater management
Despite the improvements in water quality, there are a number of remaining issues regarding effluent disposal. At present, heavy rainfall results in storm discharge (approximately twice a month) of effluent which has only been subject to primary treatment. There are also continuing concerns about the private treatment works which have consents from the EA to discharge wastewater into the estuary.
| Objective W1 To improve the treatment of wastewater within the estuary. |
|---|
2.9.2.2 Chemical Aspects of Water Quality
One of the main chemical water quality concerns in the Medina has been the impact of the Tri Butyl Tin (TBT) based antifouling paints on the ecology of the estuary. Although the use of TBT was banned for use on vessels under 25m in length, the chemicals involved are persistent and are likely to have a long term impact. The disappearance of the common dog whelk from sea walls at Cowes and throughout the Solent is attributed to TBT contamination, with the Medina Estuary recording the highest levels on the Island (Langston et al 1994). Other potential chemical sources of pollution relate to contaminated land and agricultural run off.
Stag Lane tip is the main contaminated land site of concern. This landfill site is effectively decommissioned but still receives some special wastes such as drilling muds. The site has been stabilised but the tip requires ongoing management and monitoring in spite of a leachate recirculation system installed in the mid 1980s to prevent leachate entering the estuary. Other potentially contaminated sites, which could impact on the water quality, exist within the estuary. However, a comprehensive survey of contaminated sites has not been carried out to date.
Run off from agricultural land contains pesticides and fertilisers which can have an impact on the water quality. According to the EA, the impact of agriculture is not currently a serious problem in the Medina. However, monitoring is required to review agricultural inputs to ensure that negative impacts do not arise.
| Objective W2 To ensure that chemical pollutants do not significantly affect water quality. |
|---|
2.9.2.3 Oil Spill Contingency Planning
The impact of oil on the Medina is mainly thought to be an aesthetic problem comprising occasional oil sheens from commercial and recreational craft. However, the estuary is vulnerable to pollution from an oil spill within the Solent or within the estuary. Oil spill contingency planning within the estuary is fragmented, based primarily on the two Harbour Authority jurisdictions. Cowes Harbour has an Oil Spill Contingency Plan (1999/2000) which is reviewed yearly to be kept up to date, and oil spill incidents are addressed in the Newport Harbour Emergency Plan. In addition, the Isle of Wight Council is currently revising the IOW County Oil Spill Contingency Plan.
| Objective W3 To ensure that up to date and comprehensive plans to deal with any oil spill incident exist. |
|---|
Map 9: Discharges into the Medina
Click here to see the whole map
Click here to see the Water Management Action Plan
Page last updated on: 04/09/2001
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