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Slopes and Walls


1.3_overview.jpgLEAP's Engineers have 20+ years individually of slope stability analysis and slope engineering in cut slopes and embankments, covering the full range of soil and rock conditions encountered in the southeast of England. LEAP is able also to draw upon the expertise of a number of independent consultants working under the LEAP banner, utilising a wide range of analytical methods. LEAP has undertaken a number of slope assignments and this case study highlights just one of those.


Historically the site comprised part of a gas works and was more recently a builder’s yard. Contamination associated with the site’s former use and buried structures including gas holder bases and liquor tanks were anticipated on site. The site is located on a principle aquifer (Chalk) and adjacent to a sensitive tidal river. Redevelopment of the site with housing was proposed.
LEAP was appointed to carry out a review of the previous investigation reports carried out by others and to produce quantitative risk assessments for both human health and controlled waters for the site to provide remedial targets for site clean-up.
Seven intrusive investigations undertaken by various parties had identified elevated levels of petroleum hydrocarbons (TPH), phenols, cyanide and Polyaromatic hydrocarbons (PAH) as well as heavy metals in the shallow soils. Groundwater sampling detected similar contaminants in the shallow groundwater. Slightly elevated levels of TPH, PAH, phenol and metals were also detected in the deep groundwater within the chalk. River water samples both up and downstream of the site contained traces of cyanide.

The site is located on the mid slopes of a dry valley on the scarp slope of the South Downs. Efficient use of the limited land space included cutting the houses into the slope with the rear ground floor outer walls acting as retaining structures. Ground conditions comprised a highly weathered chalk and chalk sequence and initial site investigations identified a potential slope stability issue for the temporary works. LEAP worked in conjunction with a specialist external Consultant to provide a low cost workable solution to the problem which put site safety at the forefront of design.



Project Overview



National Housebuilder


SE England

Sevices Provided

  • Desk Study
  • Geotechnical and Geoenvironmental Intrusive Site Investigation
  • Interpretative Report including detailed slope stability analysis