BHA Consulting - Casestudy

Client: Greater London Authority (GLA) & Transport for London



Project Description

Foul sewage and trade effluent pumping station for industrial development

BHA Consultings Commission

The London Sustainable Industries Park provides fully serviced industrial plots for renewable energy projects and material regeneration and reuse. In 2014 the GLA approached BHA to undertake studies of capacities of the existing foul sewerage infrastructure that served both the future LSIP development, and existing industrial areas. This infrastructure included a pumping station handling the substantial trade effluent flows regenerated by existing industrial plants. The study highlighted insufficient capacity in both the existing pumping station and associated rising main. Working with Turner and Townsend (as project managers) BHA developed a strategy for replacing the existing pumping station and rising main with a new structure that would be designed to a suitable standard for adoption by Thames Water. BHA were subsequently commissioned by GLA/TfL to undertake the detailed design of the pumping station, rising main, and sewer diversions, and obtain approval from Thames Water.

The pumping station has a flow capacity of 25l/s, which required a 6m diameter 14m deep wet well. Being close to the River Thames ground conditions comprised peat and very soft silt down to gravel at 14m depth and with high ground water, there was the risk of this groundwater being contaminated.

Contractor Breheny constructed the wet well using caisson methods sinking the concrete rings through the poor ground, at one stage there was a risk of the caisson being lost as it dropped rapidly into the soft ground.

The 645m long, 225mm diameter, rising main was laid along a busy industrial road using directional drilling through poor ground to connect to the existing Thames Water combined sewer at Chequers Lane.

New sewers were laid at depths of up to 6m to divert flows from the redundant pumping station to the new pumping station. Due to the poor ground conditions it was not feasible to construct these sewers using conventional open cut methods and consequently all sewers were constructed using thrust boring methods. Again with ground conditions unsuitable for supporting structures all manholes were installed using caisson methods to be founded on the underlying gravel.

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