Project Title: East Worthing FAS – Teville Stream Hydraulic Study
Project Number: IMSO001181
Project Stage: Initial Assessment
Environment Agency Project Manager:
Contact Details for EAPM: Address: Telephone: E-mail:
BRIEF DESCRIPTION OF PROBLEM:
The Teville Stream lies within the town of Worthing, West Sussex. The River Adur Catchment Flood Management Plan (Capita Symonds, 2008) identified possible areas of flood risk, but did not carry out broadscale modelling of the catchment and instead based it’s assessment of risk on the Flood Zone maps. The CFMP states that the current baseline is insufficient to appropriately determine fluvial flood risk within the system. This project seeks to accurately determine the level of fluvial flood risk within the Teville Stream catchment area.
The catchment is densely populated with much of the upper area being culverted and integrated with the surface water of the town. The semi-natural part of the upper watercourse is not very well defined, having several tributary streams and agricultural drainage channels. The main channel is a mixture of culverts and open sections, running under and alongside a pharmaceutical works, an industrial estate, historic landfill sites, a public amenity tip and a sewage works, finally emerging in an open channel which enters Brooklands Lake, a public leisure facility/boating lake occupying the area of the former tidal basin. This freshwater lake is maintained artificially by a terminal control structure at the seaward end, which drains into the sea after passing under the A259 seafront road. Flow from the north is augmented by runoff from the A27 highway and is discharged from a retention structure constructed on one of the tributaries.
BRIEF DESCRIPTION OF SERVICES REQUIRED: Identify full extent of urban and semi natural catchment area, including primary and secondary sewers and Main River area. Produce a detailed hydraulic study of the catchment, with a separate hydraulic study of the urban surface water system that makes up part of the upper catchment. Produce an assessment of flood risk from failure of any fixed assets and from storm events as outlined in Appendix B below.
This is to be completed in the following stages:
1. Topographic survey and asset survey (if required), to enhance existing LiDAR data (available from EA) and sewer maps (available from Worthing Borough Council or Southern Water). 2. Hydrology 3. Hydraulics 4. Production of draft project outputs 5. Production of final project outputs 6. Project completion and post project appraisal
The specifications to be used in this project are:
Survey - The National Standard Contract and Specification for Surveying Services (Version 3.0, April 2008) Modelling and Mapping - Flood Mapping Specification (Version 1.2, August 2006) Areas Benefiting from Defences – Criteria for Identification of Areas Benefiting from Flood Defences and Producing the Flood Map (Version 2, July 2005). Flood Hazard Pilot Study – Main Report and Work Packages 1, 2 & 3 Sewer model – to be confirmed
A detailed description of requirements for this project are included in Appendices B and C.
ENVIRONMENTAL CONSIDERATIONS: • Highways Agency runoff storage structure • Part of upper catchment runs through GSK pharmaceutical facility. GSK have discharge consent and operate control structures which allow them to capture flows in the event of a spillage. • Giant hogweed is present in part of the catchment • A sewage treatment works is located in the lower part of the catchment • Worthing Borough Council has identified probable contaminated land sites at Brooklands and Decoy Farm (both historic landfill sites). • Part of the stream runs alongside a municipal waste facility. • WFD status is Bad, with the status objective being to reach Good by 2027. • There are no Environmental Designations in the catchment, although the upper headwaters may originate from springs within the South Downs National Park (the location of the source is not clear) • Inflow from the east at Brooklands Lake is through the adjacent Industrial Area, and may contain heavy metal traces OUTLINE PROGRAMME: Contract Award – 1st Jan 2010 Report completion - 1st July 2010
CONTRACT STRATEGY:
Response time for return of initial proposal: to be returned by 12 midday on 8th Dec 2010 Late or non-compliant submissions will not be considered
¾ Project Services Contract - Option C
CONTRACT STRATEGY: cont.
Consultant(s) being approached: 1. 2. 3. ATTACHMENTS “Teville Stream Map.pdf” Contact at Worthing Borough Council to view surface water mapping information Contact at Environment Agency for LiDAR data.
CONSULTANT’S RESPONSE
The consultant shall provide a technical/quality/price proposal of a maximum of 3 pages consisting of the following information:
• Section 1 Key people to be used and their roles together with a maximum of 4 separately submitted CVs for key persons only. • Section 2 A brief proposed methodology and approach to the assignment. • Section 3 Outline Programme • Section 4 Outline assessment of consultant owned risks • Section 5 Estimated price for the project (with breakdown of costs included separately on Pricing Proforma) for carrying out the services. ASSESSMENT MODEL WEIGHTINGS 25:75 Price:Quality
DATA AND INFORMATION MANAGEMENT
INTELLECTUAL PROPERTY RIGHTS (IPR)
Project Managers must review and document the IP assets that will be used and created by the project and understand whether there are any specific IPR issues/concerns with the IP assets – these should be addressed in this section
DATA MANAGEMENT PLAN
For every commission that involves data and information, Project Managers must initiate a Data Management Plan which is then managed during the entire lifecycle of the project.
DATA CUSTODIANSHIP
Project Managers must identify and liaise with data custodians at the appropriate level of Local, National or Executive.
LICENCING INFORMATION AND KNOW-HOW
Project Managers to identify information and know-how from the Environment Agency that is to be supplied to contractors. All the Environment Agency and third party owned datasets that are supplied must be listed in a license which must be updated if new or updated dataset are supplied during the commission.
METADATA
Any new data or information that is created as part of a commission must have associated metadata which should be entered in the Information Asset Register. Project Managers need to ensure that any requirements from the consultants to provide this Metadata are identified in this section.
DATA SECURITY Please note that we consider the following information to have sensitivity or security restrictions and should be marked as ‘Protect – Commercial’ and be encrypted and password protected: • Topographic and hydrographic survey data (inc. LIDAR) • Hydrological/Hydraulic Models • 3rd Party Hydrological/Hydraulic Models • Surface Water mapping data obtained from either SWA or WBC.
FURTHER INFORMATION
This is a complex system involving water authority assets, highways drainage, urban drainage, agricultural drainage and main river. As such a combination of sewer and river modelling is likely to be required and submissions demonstrating an innovative approach to the problem will be welcomed.
Health and Safety is the number one priority. The consultant will promote and adopt safe working methods and shall strive to deliver solutions that provide optimum safety to all.
Should the consultant identify suitable additional requirements, other than those listed in this document, then these may be included in their submission as clearly defined additional items.
In the interests of efficiency and value for money, work undertaken on viability reports should be planned and carried out to make it relevant to a full detailed appraisal and environmental impact assessment, should they be undertaken.
Requests for further information should be directed through the Environment Agency PM / Senior Procurement Officer.
Access to Land along the main river route can be arranged via at WBC
APPENDIX A - GEOGRAPHICAL LOCATION OF WORK See “Teville Stream Map.pdf”. Note that there are significant inputs to the system which are not shown on the map, these require locating and identification. One culvert joins the middle of first extended culvert shown on the map. This culvert drains a significant part of the urban areas and highways in the town and may contribute more water to the upper part of the system than the streams shown on the map. A second large culvert (not shown) joins the downstream culvert before it runs under the sewage works. Historic maps of the town and evidence of urban flooding indicate that this may also have a significant contribution to the system.
Input from the north is via a Highways Agency Structure (a large interceptor) just north of the GSK boundary.
APPENDIX B – BREAKDOWN OF REQUIREMENTS & TARGET ACCURACY
Channel / Topographic survey
• If new channel survey data is required, the consultant shall arrange collection of this data. • Use all sources of information available to develop a sound understanding of the defences and other assets along the Teville Stream
Sewer modelling: o Produce sewer map, based on Southern Water’s electronic map verified against the hard copies held by Worthing Borough Council (there are some known discrepancies between the two sets of maps) o Include scenarios based on different levels of siltation in the culverts
Hydrology, Hydraulics and Production of Outputs • Make an initial review of the current hydrology developed for the Teville Stream • Make recommendations on a way forward for modelling the hydrology for the Teville Stream mapping study (this may be to make adjustments to the existing model or to remodel the hydrology using a different method).
A hydrologic and hydraulic model should be created to produce the outputs as described in the table below.
Requirements Fluvial Outputs 1D or 1D-2D linked model of channel 1 in 5, 1 in 10, 1 in 20, 1 in 50, 1 in 75, 1 in 100, 100+20% for climate change, design and floodplain ‘with defences’ events. 1D or 1D-2D linked model of channel Up to an additional 10 model runs of interim return periods to identify first property and floodplain ‘with defences’ flooding and culvert blockage and collapse scenarios. Levels and outlines for first property flooding event to be supplied. 1D or 1D-2D linked model of channel 1 in 20, 1 in 100, 100+20% for climate change, and 1 in 1000 design events. and floodplain ‘without defences’ Production of hazard maps Hazard will be rated and mapped for all Defended return periods. Hazard should be calculated using the formula as set out in the 'Framework and Guidance for Assessing and Managing Flood Risk for New Development' (FD2320/TR2) • Depth – Maximum modelled depth at any given time step • Velocity – Maximum modelled velocity at any given time step
Production of flood outlines 1 in 5, 1 in 20, 1 in 50, 1 in 75, 1 in 100, 100+20% and 1 in 250 for climate change events for the ‘with defences’ scenario
1 in 20, 1 in 100, 1 in 100+20% and 1 in 1000 events for the ‘without defences’ scenario
First Property flooding event outline. Floodplain levels and depths, Velocities, Grid Files to be supplied for all modelled scenarios. Animations to be produced for Flows, and Flow Direction agreed scenarios.
SCHEDULE 19 APPENDIX A STATEMENT OF REQUIREMENT
Reporting • All draft outputs, including all model files, are to be provided in electronic format only. • One hard copy of the final report, including A1 printed maps, to be provided • One electronic copy of all final outputs and report to be provided on CD/DVD/Hard drive • All reports prepared by the consultants need to be produced wherever possible on recycled paper containing at least 80% post consumer waste and printed double sided. • The final report will discuss modelling approach, updates to modelling, new modelling, and results. It should include chapters on defence standards, ABD modelling and hazard mapping. • Produce a User Guide to show how best to use the outputs of the model.
Target Accuracy The target accuracy for flood modelling shall meet the following two criteria:
1. The target should be +/- 250mm on the 100-year water level 2. The accuracy of the river model is such that for at least three calibration events, (covering both in and out of bank flows) the mean error plus one standard deviation of the error at all stations and over the whole time span of the events shall not exceed 150mm.
This refers to a given return period. Accuracy ranges for the model will be detailed in the Final Modelling Report.
Note: This is a target accuracy and a model will not be assumed to be unacceptable if it fails to meet this providing that a) the reasons for this failure are clearly stated and b) the actual accuracy is clearly stated.
The consultant shall use a quality assured system to control the quality of the hydrology and the hydraulic modelling. The quality of the 2D modelling shall be determined by checking the model outputs against any available historical flood data. Particular attention to accuracy should be given to key urban areas and significant structures.
The target accuracy for the sewer modelling is to be confirmed. Suggestions are welcome.
155_04_SD397 version 1 issue date: 02/09/09
APPENDIX C - AVAILABILITY OF INFORMATION
Previous Modelling or Study Work Available • West Sussex SFRA • Worthing & Adur SFRA • Adur CFMP (Capita Symonds / Environment Agency, 2008) • Condition Report of Borough Land Drainage Ditches (Worthing BC, 1999) • Restoring the Teville Stream Catchment for the Community Scoping report (Worthing & Adur Councils / Royal Haskoning, 2009) • Culvert CCTV survey
Flood Event Outlines and Aerial Photography: Flood Risk Mapping & Data Management Technical Specialist.
Hydrometric Data:. Flood Risk Mapping & Data Management Technical
LiDAR Data: Please contact
Channel/Structure Survey: Flood Risk Mapping & Data Management Technical Specialist
Sewer maps: Hard copies held by Worthing Borough Council; electronic copies showing only Southern Water’s assets are held by Southern Water.
155_04_SDXXX version 1 issue date: 21/05/09