Vanguard Self Storage, Lawrence Hill, Bristol

Mark Creighton

Mark Creighton


Tel: 020 3096 7567


Tercon Limited


  • 3D Finite Element Analysis
  • Ground Movement and Impact Assessment Report (Sewers)

Impact assessment of proposed warehouse on existing sewers

CGL was engaged to provide an impact assessment on two sewers (assets of Wessex Water) below a proposed development at Church Road in Lawrence Hill, Bristol for a double level warehouse to be founded on piles of varying lengths.

The sewers run beneath the site at different orientations and depths comprising structures of different materials (concrete and brick) and different sizes.

Using existing information for the geology at the site and the surrounding area, CGL developed a ground model using PLAXIS 3D Finite Element software. The analysis required modelling of the sewers, the piles, the ground slab and the proposed retaining wall which would support the sloping ground to the south of the site.

CGL predicted the ground movements due to the proposed works and construction sequence and then used the data to calculate the sectional deformations of the sewers as well as the deformations along the sewers axes. The predicted deformations and strains were compared against published criteria, which define the limiting strains that can be sustained by pipes and sewers of different materials
and dimensions.

Based on the assessment, the potential impact on the existing sewers running beneath the site is not expected to be significant. The assessment has conservatively assumed that the stiffness of the sewers is negligible.