Invitation to Tender for Sediment source apportionment (Smarter Water Catchments Initiative)

The Chilterns Chalk Streams Project and Chilterns Conservation Board are catchment hosts for the Chess Smarter Water Catchments Initiative developed by Thames Water. The group would like to understand:

1. the proportion of different sources of fine sediment entering the River Chess and how these vary spatially along the river and temporally over the year;
2. annual fine sediment load for the River Chess;

to guide mitigation plans and actions to prevent fine sediment delivery to the river. Preliminary evidence suggests that the different sources of fine sediment might include, but not be limited to agricultural (arable and grassland) and urban runoff, damaged road verges and riverbank erosion.

Specific objectives of sediment source apportionment project

• PART 1. Work with Chilterns Chalk Streams Project and Environment Agency to identify appropriate locations from which to collect representative source/suspended/bed sediment samples. Costing should include production of maps and GIS data layers (ArcGIS format) with sample points categorised by land use and source sample type, identification of land owners and contact with landowners to gain permission to take source samples.
• PART 2. Collect representative source samples from each of the five source types i.e. collect at least 150 samples in total (additional numbers of samples may be required depending on how many land use types are identified) and prepare samples for analysis. Collect any additional bed sediment and gully pot samples needed for analysis.
• PART 3. Analyse all samples (suspended sediment, bed sediment and source samples including gully pot samples) for the chosen tracer fingerprint properties that will provide adequate source discrimination and apportionment of sediment. The chosen tracers need full justification in tender response documents.
• PART 4. Carry out numerical modelling for source apportionment of bed and suspended sediment samples to include Monte Carlo uncertainty analysis. Reasons for choice of numerical model should be explained in tender response.
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• PART 5. Collect suspended sediment samples over sufficient storm events to calibrate four turbidity sensors at Blackwell Hall, Restore Hope Latimer, Loudwater and Elms Lake. Calibrate sensors using bespoke rating curve.
• PART 6. Estimate annual sediment load at six sites using available turbidity sensor data.
• PART 7. Evaluate the impact of fine sediment sources and their temporal variation on chalk stream habitat, priority species and hydro-geomorphology in the River Chess.
• PART 8. Produce high level mitigation costed options with a summary of benefits to each Chess Smarter Water Catchment theme (see Section 3.2.3).
• PART 9. Produce report to present results (see Section 3.2.3).
  Tender response should include justification of tracers to be used for the source apportionment. A phased approach to tracer use will be considered.

Please download the full tender document below for further information and to complete the supplier questionnaire.