Redevelopment of Disused Farm, Delvyns Lane Gestingthorpe Essex CO9

Case Study Reference: CS21-10-02

Planning Authority: Braintree District Council

Planning Reference: https://www.braintree.gov.uk/planning-building-control/view-comment-planning-applications and 20/02053/FUL

Synopsis:

Given the sensitive nature of the development (residential) and the history of the site a contaminated land planning condition was attached to the decision notice for the proposed development.

The first stage of discharging the condition was to prepare a Phase I desk study report in order to determine if the site has the potential to be impacted by elevated levels of contamination, and to determine the source as well as the likelihood of the risk occurring.

A desk study determines what issues relating to historical contamination may affect the site, this is undertaken by reviewing the site history using a combination of O.S. maps, aerial, plates and street level imagery, a review of data held by regulatory bodies (Environment Agency, local authority, BGS etc.) as well as a site walkover survey.

The history of the site and surrounds were researched using a combination of Ordnance Survey (O.S.) maps, street level imagery and aerial plates, this revealed the site was initially developed prior to the first edition O.S. map (1876). A pond was noted 1m to the east of the site which was noted on all subsequent maps.

The site was developed both circa 1896 and circa 1953.

Street level imagery confirmed the buildings were agricultural.

The planning history of the site was reviewed as part of the desk based research and reports associated with any previous application were located and studied and no previous applications were noted.

The published geological maps identified the drift geology being the Lowestoft Formation. The bedrock was given as the London Clay Formation.

Data provided by regulatory bodies identified two ponds, one on the eastern boundary and the second 210m east. A number of waste exception licenses were noted for the site relating to the treatment of waste as well as the presence of a hopper and a silo in close proximity to the site.

The sensitivity of controlled waters was undertaken to determine if the site posed a risk to the nearby water bodies, this concluded that as the bedrock was an unperceptive aquifer the groundwater was of low risk due to the history of the site and further assessment was not warranted.

On completion of the desk based research a site reconnaissance visit was undertaken, this confirmed the site comprised of a number of barns with a workshop identified in once of the barns and storage containers in another.

Once the walkover survey was completed a qualitative risk assessment was undertaken on the potential sources of contamination identified in the desk study report in order to determine if any warranted further investigation, this concluded that the potential for made ground on the site as well as the past uses of the buildings, containers, road planings required further assessment.

The report concluded that further intrusive works were required to provide further information on the potential sources of contamination on the site and as mobile contamination may be present remediation in lieu of further works was not suitable.

The proposed works were undertaken in March 2022 and comprised  21 trial pits on a 20m, non-targeted sampling grid. The site was unchanged from the October 2021 site visit.

The investigation confirmed the presence of made ground on the site, however it was not present sitewide and using GIS the predicted depths of made ground across the site were predicted.

Olfactory evidence of hydrocarbons were noted at one location and damaged cement sheeting at a second, additional chemical testing was scheduled to assess these risks.

The chemical data was data was statistically assessed with data for each strata being assessed separately and this concluded that whilst the made ground on the site was impacted by lead,  PAH’s and asbestos the chemical storage on site and the road planings had not impacted site soils.

A water mains risk assessment was also undertaken and this concluded that the site soils at two locations prevented the use of PE mains.

The conceptual model created in the Phase I report was refined and using the predicted depth of made ground across the site  proposals for remediation were tailored on a plot by plot basis giving the most cost effective options.

The Phase I and Phase II reports were submitted (23/01927/DAC) to discharge Condition 3. The reports were accepted and the condition discharged.

Once the recommendations had bene approved the final part of the pre commencement condition (remediation strategy / implementation plan) was prepared, this provided the methodology of how the remediation will be undertaken as well as how the works will be inspected and validated.  As of November 2023 the remediation strategy had not been submitted.