Item 11 Addendum - Construction Cost Update - Gruggies Burn Flood Alleviation Scheme
West Dunbartonshire Council · 25 March 2026
Back to West Dunbartonshire Council — 25 March 2026 and its agenda
Text extracted from the council's PDF. Layout and reading order may differ from the original.
Page 1
WEST DUNBARTONSHIRE COUNCIL Report by Chief Officer – Roads & Neighbourhood West Dunbartonshire Council – 25 March 2026 Subject: Addendum to Item 11 - General Services Capital Budgetary Control Report 2025-26 to 31 January 2026 (Period 10) Construction Cost Update - Gruggies Burn Flood Alleviation Scheme 1. Purpose 1.1 The purpose of this addendum is to update members on the increase of construction costs since December 2025 to deliver the Gruggies Burn Flood Alleviation Scheme and to request approval to finalise and sign the construction contract to deliver Option 1 – Full Scheme Delivery. 2. Recommendations 2.1 It is recommended that Council: i) Note that, following receipt of all project costs, the construction cost for the Gruggies Burn Flood Alleviation Scheme has increased by £3.46m since council approval in December 2025. This increases the council’s capital contribution by £0.692m with an annual revenue implication of £0.032m. ii) Approve that the capital plan budget details for RN11 Gruggies Burn Flood Alleviation Scheme are updated to reflect the increase in capital costs to construct Option 1 – Full Scheme Delivery. iii) Authorise the Chief Officer Regulatory and Regeneration to conclude negotiations in relation to the finalisation and signing of the construction contract to deliver Option 1 - Full Scheme Delivery. 3. Summary 3.1 At the 17 December 2025 Council meeting elected members considered the following 4 options to deliver the Gruggies Flood Alleviation Scheme: Option 1 – Full Scheme Delivery Option 2 – Delivery of Inlet and Diversion Culvert Option 3 – Delivery of Coastal Defences and Flood Gates Option 4 – Do Nothing 3.2 The costs following detailed design considered in December 2025 were as ITEM 11 Addendum
Page 2
follows: December 2025 Option 1 Option 2 Option 3 Option 4 Total £44.7m £39.2m £14.7m £1.98m West Dunbartonshire Council Contribution (20%) £8.94m £7.84m £2.94m £1.98m Scottish Government Contribution (80%) £35.76m £31.36m £11.76m N/A 3.3 Council approved the progressing of Option 1 – Full Scheme Delivery. 3.4 Officers have progressed with the contract preparation for Option 1 to meet the deadline set to access Scottish Government funding. Should the 31 March 2026 deadline not be met the opportunity to access Scottish Government funding of 80% of project costs is no longer available. 3.5 The project costs included all anticipated major utility service diversions and construction work being undertaken by Network Rail however these have increased through confirmation with the key stakeholders. Final costs have been received which have increased the construction cost of Option 1 to £48.16m. 3.6 The updated construction costs to deliver the 3 options are set out in the table below: Construction Costs (Capital) March 2026 Option 1 Option 2 Option 3 £m £m £m Total 48.160 42.560 14.700 West Dunbartonshire Council Contribution (20%) 9.632 8.532 2.940 Scottish Government Contribution (80%) 38.528 34.028 11.760 3.7 The total revenue implications for the council are set out below: WDC REVENUE PER ANNUM Option 1 Option 2 Option 3 £m £m £m Principal Repayment 0.241 0.213 0.074 Interest on Principal 0.210 0.186 0.063 Total 0.451 0.399 0.137 WDC REVENUE 40 YEARS Option 1 Option 2 Option 3 £m £m £m Principal Repayment 9.632 8.532 2.940 Interest on Principal 8.400 7.440 2.520 Revenue in 2025/26 0.000 0.000 0.000 Total 18.032 15.972 5.460
Page 3
3.8 The additional capital impact of the construction cost increase since December 2025 is as follows: INCREASE IN CAPITAL Option 1 Option 2 Option 3 £m £m £m Total 3.460 3.460 0.000 West Dunbartonshire Council Contribution (20%) 0.692 0.692 0.000 Scottish Government Contribution (80%) 2.768 2.768 0.000 3.9 The additional revenue impact of the construction cost increase since December 2025 is as follows: WDC REVENUE PER ANNUM Option 1 Option 2 Option 3 £m £m £m Principal Repayment 0.017 0.017 0.000 Interest on Repayment 0.015 0.015 0.000 Total 0.032 0.032 0.000 WDC REVENUE 40 YEARS Option 1 Option 2 Option 3 £m £m £m Principal Repayment 0.692 0.692 0.000 Interest on Repayment 0.600 0.600 0.000 Revenue in 2025/26 0.000 0.000 0.000 Total 1.292 1.292 0.000 Chief Officer: Gail Macfarlane Service Area: Roads and Neighbourhood Date: 20 March 2026 Person to Contact: Liam Greene Roads and Transportation Manager Email: liam.greene@west-dunbarton.gov.uk Wards Affected: Dumbarton and Leven Wards