Sewer Flow Modelling Expertise and Technical Support

The Supplier will review the sewer capacity modelling that was previously undertaken to determine whether the approach taken to modelling the available capacity in the sewer system was in-line with the wastewater company's own internal guidance and industry practices at the time that the work was carried out. This will include:

consideration of whether the modelling parameters used in the modelling work were reasonable;whether the scope of the modelling work undertaken was suitable to support decisions on the available capacity of the sewer system; modelling the available capacity of the sewer system to confirm the original sewer capacity modelling results; and review the wastewater company's approach to determining the expected peak flows from the new development.

If the Supplier concludes that there are concerns that the approach taken by the wastewater company to model the available capacity of the sewer was not reasonable, the Supplier will also be required to provide its view on what a reasonable approach would be and use the wastewater company's sewer model for the area to assess the available capacity in the sewer network in the area of the development site.In order to undertake this work, the Supplier will make arrangements with the wastewater company to be provided with: the initial assessment of the available capacity in the sewer network; the model verification report for the original model;information about the wastewater company's internal guidance; and the wastewater company's internal standards and practices that it uses when assessing the available capacity in its sewer network. This will contain commercially sensitive information. As a result, the Supplier will be required to enter into an agreement with the wastewater company to enable the Supplier to receive this information on a confidential basis.If the Supplier requires information about the standard industry practices for assessing sewer capacities from other wastewater companies it will be required to obtain this information from other wastewater companies itself.The successful Supplier's findings will help to inform Ofwat's determination on whether there was available capacity in the existing sewer network to accommodate the additional flows from the new development site without negatively impacting existing customers. The Supplier will be reviewing the modelling work undertaken to support both the planning and design stage of the capital scheme which was undertaken. The Supplier will be required to have access to the relevant software that is necessary for it to undertake any modelling work. This will not be provided by Ofwat. The modelling work that the Supplier will be reviewing was undertaken in 2014-2015. As a result, the Supplier will be required to have access to the appropriate version of the software, which may not be the most recent version. The relevant software is InfoWorks CS 11.5 and InfoWorks ICM.

Additional information: For Further Information, please contact: procurement@ofwat.gov.uk