Tender Summary

Nutrient Neutrality -Full Feasibility Assessment of the Potential for the Development of Constructed Wetlands within Norfolk

Buying Organisation

Natural England

Contract Value

£15,000 to £48,000

Tender Description

Further feasibility work should provide the following information in report form. The work should be informed by the initial pre-feasibility report, 'Pre-Feasibility Assessment of the Potential for the Development of Constructed Wetlands' dated 03/05/2023. The report should provide the confidence to proceed to 'design and build' phases or the rationale for not proceeding with wetland implementation.
Full feasibility Specification
The key deliverable for this contract will be:
I. Build on the 'pre-feasibility reduction figures' through identification of the possible range, ie minimum and maximum, for nutrient reduction capacity of the site, via wetland creation, for Nitrogen and Phosphorus using:
a. Transfer abstraction of water from the relevant watercourse and;
with generated reductions calculated using:
i. One of the following methods with a supporting narrative
- P-k-C* model
- k-C* model
- regression equation
ii. Details of potential Flow
- Flows of water from the relevant source
- Inflow of other water sources
- Variability of flow with time
iii. Details of Concentration within Flow
- Nitrogen and Phosphorus loads within all water sources considered
- Variability of the quality with time
iv. Refinement should enhance reduction calculations by ensuring the most relevant/localised data is used. Including:
- A water balance calculation
- Estimated sediment accumulation rates

2. Clarification of design objectives in terms of the site's capacity to generate nutrient reductions for N and P in the context of:

- Define the potential biodiversity impacts of:
o potential loss of ditch/stream (where relevant)
o water impoundment/abstraction
o water temperature impacts through wetland transfer

- Carry out soil substrate investigations to determine:
o potential for groundwater interaction
o the extent of clay onsite
o whether the wetland requires a clay or artificial liner
o if soil nutrient levels pose a risk of 'treatment liability' in terms of nutrient leaching

- Development of a monitoring and baselining strategy, including:
o identification of suitable monitoring points at in-flow and potential out-flows
o flow and nutrient concentration monitoring

- Ranged cost estimates of:
o implementation and construction
o performance monitoring to equilibrium
o annual wetland maintenance

- Carry out a desk-based assessment to identify any risks that may impact design or construction of the wetland from:
o archaeological areas on-site
o utilities on-site

- Define the potential impacts of 'urban runoff' on wetland effectiveness (where relevant) including but not limited to:
o contaminate collection and discharge risk
o contaminate effect on biological processes on wetland plants

DESCRIPTION CONTINUES IN ADDITIONAL TEXT SECTION

Tender categories (products & services required)

Environmental services (CPV 90700000)

Region

North East (UKC)

Buyer Information