Groundworks for factory extension
Vitacress Salads, Hampshire
Project challenges
High water table
We were approached by the main contractor Brymor Construction to tender for the various aspects of groundworks across the St Mary Bourne factory site. The site was challenging from the point of view that the natural groundwater level below the site was less then 900mm from ground level. The groundwater pressure was so prolific that any works greater than 1.0m deep required professional dewatering to keep the groundwater down. The St Mary Bourne site is a busy production and distribution centre, so it was essential that any works were carried out safely and with due regard to the existing operations of their business.
The works in 2020/21 were associated with the factory extension and involved:
- Design of factory wash underground pump station consisting of 2.5m diameter concrete pump chamber at 3.0m deep, bespoke and built in house, DN100 stainless steel internal pipework with guide rails and ducks foot mounting, double variable speed pumps and controls
- Culvert diversion works by installing 3 x 180mm diameter polyethylene pipework in a common trench at 800mm deep, PE manifold to single 355mm flanged inlet
- Installation of 400mm diameter gravity Funke HS pipework across a reinforced concrete yard, additional 400mm diverting valves, various valve chamber and concrete chambers
- Installation of gravel wash 90mm HPPE pumped pipework across the site to take raw water from the process
- Installation of a SPEL Puraceptor Class 1 Separator below ground, in the concrete yard to serve the lorry wash including all chambers, inlet pipework and connection to an ACO Q-Max system
- Various concrete formworks and yard reinstatement
- Concrete formed manhole chambers of varying depths.
As the site has existed and evolved since 1964, the ground was heavily obstructed with various services, pipes and cables, laying 5 no. large bore pipes in common trenches was a challenge, not only dealing groundwater but encountering and having to negotiate existing services.
Our approach
Minimal disruption to the client's business
Due to the site being in full production and distribution in full swing, regard to health and safety was paramount to the project to ensure the business could operate. Working with Brymor and all consulting engineers, MJ Abbott formed a health and safety strategy to ensure these essential works were not disruptive to the client’s business.
In order to carry out some of the 11m x 5m x 4m deep excavations for the GRP separator, we developed a suitable system of ground dewatering by drilling 4 no. boreholes around the proposed excavation at 6m deep. Pumps were set up around the proposed excavation drawing water from each borehole to allow the ground water to be pulled down below the proposed excavation depth. Due to the sensitivity of the site and to ensure that pollution did not occur, the abstracted water was passed through settlement tanks and silt traps prior to be discharged across the field to the north of the site.
Heavy duty interlocking Larsen sheet piles with interlocking corners and mega frame hydraulic braces were installed around the excavations to support the pure gravel and flint ground. Excavations were formed sufficiently to a depth below the proposed tanks to allow steel reinforced bases to be formed before the tanks were placed into position and backfilled with further concrete to avoid flotation.
The pumping stations were fabricated in-house, consisting of heavy-duty concrete pumping chambers and cover slabs. For longevity, we designed and fabricated stainless steel guide rails and pump discharge pipework.
Outcomes
Client satisfaction
The whole MJ Abbott team carried out the works to an incredibly high standard to the satisfaction of the client and main contractor.
We were looking for a contractor who had experience with dewatering, groundwater and working with a high water table. MJ Abbotts certainly had the experience and from their first moment on site it was clear we had found the right contractor for our unique site. This turned into us being awarded additional work from our client which we were happy to instruct MJ Abbott to proceed with. This led to a year long relationship on site that was in my opinion a pleasure to be a part of.
It was clear from the outset that MJ Abbott are a highly technical company who were able to assist and engage with our design team and provide solutions or recommendations to products the designers were perhaps not aware of. This helped overcome a number of challenges encountered on site.
In terms of their physical work, the operatives from MJ Abbott also have that technical knowledge, gathered from vast experience within the industry. They were all proven to be methodical and conscientious workers who had a sharp eye for detail and a real drive to get the job right, first time. Safety was never at risk and recommendations and feedback was always shared both ways.
Overall, it was a pleasure to work with MJ Abbott and I have personally recommended them within our business and hope we can create some opportunities that will see us working together again.
Michael Beeching
