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Title: River Loddon / Basingstoke STW SIMCAT modelling (UC 3330) : final report
Author: Environment Agency Thames Region
Document Type: Monograph
Several major sewage treatment works in Thames Region are situated in the headwaters of river catchments where there are proposals for significant housing developments in the towns served by these major works. Thus, Thames Water Utilities have been asked to consider increasing the populations served at these works by significant amounts. The resultant increases in flow will put further pressure on watercourses. As the Environment Agency will not accept any degradation in quality, particularly in watercourses designated under the EU Fish Directive, any increases in flow due to the proposed population increases at these works may require tightening of consent standards. The problems of works at or close to headwaters in Thames Region is one that has been recognised by the Agency and some of these works already have the tightest discharge consent standards in England and Wales. Thames Water Utilities Limited (TWUL) are concerned that increases in population could lead to the imposition of consent standards that cannot be met without too great a risk of failure or with too high a cost. The Agency has agreed to co-operate with TWUL to carry out detailed, auditable modelling studies of the effects of increases in flows from these sewage works on the effluent receiving watercourses. The main question that the modelling has to answer is What are the standards required at the STW to meet the river standards required by the Agency with the proposed increase in flow?. The Agency operates a load standstill and no deterioration policy, interpreted as meaning that the quality in the river downstream that would be delivered by the current consent must be maintained after the population increases. Basingstoke STW discharges to the River Loddon, which is a designated Salmonid Fishery (RE2), and is seen as the highest priority in responding to development pressures. Currently, Basingstoke STW has a consent of 10/2 for BOD and Total Ammonia and a maximum consented flow of 65 Ml/day. Smaller STWs at Sherborne and Sherfield on Loddon (Sherfield) discharge to the Vyne Stream/Bow Brook which is a tributary of the Loddon, below Basingstoke. The Vyne Stream/Bow Brook is classified as RE3 and is not a designated fishery. Current consents for Sherborne and Sherfield are equivalent to 8/7.51 and 30/7 mg/l for BOD and Total Ammonia respectively. The Total Ammonia consent for Sherborne is seasonal and is represented for modelling purposes as an average of winter and summer 95%iles. The consented flow at Sherfield is exceeded under current operation. Figure 1.1 shows the locations of the catchment features that are referred to in later sections of this Report.
Publisher: Environment Agency
Publication Date: 1999
Publication Place: Reading
Subject Keywords: RiversCatchment managementSewage treatmentUrban populationPollution prevention
Geographic Keywords: EA South EastHampshireLoddonLoddon catchment
Extent: 63
Total file downloads: 327

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