a photo showing the site of Pinhoe Quarry before redevelopment begins

Pinhoe Quarry

Harrington Lane, Pinhoe, Exeter

Harrington Lane, Pinhoe, Exeter

Client: Pinhoe Quarry LLP

Key Facts

  • A clay pit up to 27m deep which formerly serviced a local brick-making factory
  • Planning consent for up to 380 new homes plus community facilities
  • Remediation planning and earthworks took place over 6 years.


Our Land Quality Service was delivered for this site in two stages:

We initially worked with the client to review the remediation and earthworks proposals prior to outline planning consent being granted in 2012. The bulk of the earthworks were completed between 2014 and 2016, with the final works and geotechnical and environmental monitoring being completed in 2017.

Environmental Hazards

Due to the site's previous use as a brick clay pit, there was potential for Made Ground and elevated ground gases.

Geotechnical Hazards

In addition to the presence of some existing fill, there was a potential for self-weight settlement of the new fill on this site with a resulting risk of differential settlement issues. This risk was managed by a stringent earthworks specification, which required a minimum relative compaction to 98% of the maximum dry density with maximum air voids of 5% together with surcharging of the fill thereafter.

The potential for collapse settlement arising from water inundation into the engineered fill was assessed by inundation plate tests as well as inundation of large scale load tests in-situ.

Remediation Strategy

NHBC and the client agreed a strategy for creation of a development platform using site-won and imported materials placed to an engineered-specification with the maximum depth fill material of 27m.

A programme of ongoing environmental and geotechnical monitoring and assessment was agreed and was conducted throughout the earthworks.


Up to 380 residential units and associated community facilities will be constructed on site in the future. In addition, the site has a feature listed as a ‘Regional Important Geological Site’ (RIGS). This geological feature will be preserved within a ‘Geopark’ which will be incorporated into the future development.