As the scheme progresses, monthly updates will be made to this page. The page will also include minutes of meetings,
design details of the preferred options and other new information as it becomes available.
23rd January 2015 - Public Meeting at Boverton Castle at 4pm.
16th December - Boverton General Arrangement Drawing December 2014
- Boverton General Arrangement -December-2014
8th December – VoG and NRW Progress meeting
Summary of meeting:
Intégral Géotechnique has completed the ground investigation and provided VoG with a report. VoG has considered the four options in the report and have concluded that the only feasible option going forward (based on time, risk and cost) is not a precast concrete box culvert but Option 4 a culvert with piled abutments and foundation. To ensure the most cost effective design is achieved an additional ground investigation focusing on the top 5metres of soft ground will be required and VoG will progress this investigation as soon as possible.
A draft design of the new proposal of a new 4m wide piled culvert along with the downstream widening works was presented to NRW.
It was agreed that this option had many advantages compared to the previous design.
NRW have identified and notified landowners affected by downstream detriment as a consequence of these works. NRW are nearing completion of the cost benefit analysis of the works which will be required in order to discuss funding with Welsh Government.
5th December – Ground Investigation Report.
Summary of report:
The ground investigation comprised of the drilling of five rotary boreholes at locations either side of the existing culvert, primarily to investigate the depth to, and the nature of the solid bedrock strata. It also included the drilling of three windowless samples holes within the vicinity of a previously identified potential solution feature, with the windowless sample holes positioned to delineate the lateral and vertical extent of the “soft/very soft” natural materials identified below the in-situ made ground deposits.
A summary of the ground conditions are shown below:
In almost all instances, this would place the base of the proposed culvert within the very highly weathered silts beneath the made ground deposits. In-situ testing and laboratory analysis has indicated these materials to be water saturated and poorly consolidated/highly sensitive.
Settlements will arise from any additional stresses applied to the soil. However ground movement can also arise from ground disturbance; and/or following a period of stress relief or heave as loads are removed and subsequent reconsolidation. Therefore it is anticipated that mitigation measures need to be adopted to control and manage these effects.
Based on the in-situ testing to date it is inferred that both the made ground and the soft and very soft silts will not support the proposed box culvert without excessive settlement, both total and differential.
Therefore, pending the results of the further recommended site investigation works, four foundation options for the proposed works are tentatively proposed comprised as follows:-
- Option 1 – Employ mitigation measures to minimise initial and long term settlement of the culvert;
- Option 2 – Soil mixing to stabilise the poor materials and provide a ‘stiffer’ stratum for the founding of the culvert;
- Option 3 – Adopt piled foundations for the proposed culvert; or
- Option 4 – Adopt a secant piled foundation solution, using the secant piles to form the ‘walls’ and the foundation of the culvert, therefore eliminating the need for the precast box culvert units.
Given the various practical, physical and management issues relating to the construction it is essential that all these options be reassessed once the supplementary investigations works are completed.
However, the use of a precast concrete box option as originally intended has various geotechnical risks associated with it and therefore of the four options considered at this stage and based on the site investigation data reported, the preferred approach is Option 4, that of a secant wall construction.
7th November – Site meeting BT
A site meeting was held with BT to discuss the diversion options of their services during the construction works.
30th October – Site meeting NRW
Summary of meeting:
A site meeting with the NRW’s flood consent group was held to discuss the design options for the downstream widening works.
30th October – Site meeting WPD
Summary of meeting:
A site meeting was held with WPD to discuss the diversion options of the electricity supplies during the construction works.
29th September – 3rd October – Ground Investigation carried out in Boverton.
August - In order to determine the line of a new culvert and downstream works and progress the design, as well as produce accurate estimates of the different scheme options, we are currently progressing discussions with utility companies (BT, Welsh Water, Western Power Distribution and Wales and West Utilities) to agree the diversion of services affected by the different scheme options.
We are also progressing and initiating talks with box culvert manufacturers, river diversion specialists, traffic diversions and management options with the VoG highways team and landowners.
In line with recommendations in the initial Factual Site Investigation Report, a further Ground Investigation is expected to be carried out in September to establish the ground conditions in the necessary detail.
12 August - VoG and NRW meeting to discuss the way forward.
Summary of meeting: JBA has now completed the modelling works for the catchment and provided NRW with a Culvert and River Channel Proposals Report. A few different design options are now available, and to ensure that the best option in relation to flood return period and cost is progressed, our engineers will produce a design report which will outline the benefits and constraints of the different options and provide more detailed cost estimates. This report is expected to be completed in October. From this report NRW will progress the Cost/Benefit calculations with the aim to submit for funding to Welsh Government by December 2014 and we will progress detailed design of the final preferred option. If funding can be sourced, it is anticipated that land entry notices will be issued by Spring 2015 and construction start date to be summer 2015.
It was decided that it is too early to have another public meeting but VoG will have their website for the scheme up and running by the end of August 2014 to ensure the Boverton residents are kept up to date with the progress.
The date of the next meeting between NRW and VoG is to be agreed on completion of the design report.
15 July - Meeting with VoG, NRW and JBA to discuss the draft Strategic Options Appraisal and Culvert and River Channel Proposals Report.
9 July - Factual Site Investigation Report was received for Ground Investigation 1. Summary of the report, Site Plan.
- Site meeting with VoG and NRW to establish requirements (flood risk, pollution and ecological controls) of the Flood Defence Consent for any investigation and culvert works.