Strule SEC – Site Preparation Works

CEEQUAL Excellent Sustainability rating (75.4%) – Whole Team Award
Version 5, February 2021| Omagh, Northern Ireland

Assessor: Claire McIlwaine, WYG
Verifier:  Peter Shaw
Designers: WYG Engineering (NI) Ltd (Scheme Design) & ByrneLooby (Technical Design)
Client: Department of Education NI
Constructor: Fox Contracts

Project Summary

This project is a site preparation works for the Strule Shared Education Campus (SSEC), Omagh, which will be delivered under a separate contract. The purpose of the project was to redevelop the former army barracks at Lisanelly and St Lucia and to provide the town of Omagh with a the SSEC consisting of 5 schools, shared facilities, 13 playing pitches and an assortment of infrastructure and parking facilities. The SSEC will place education strategically at the heart of the community meaning that young people will be connected through education which will filter into the wider community. There is potentially a huge social and educational dividend which can promote and enhance community relations.

The Site Preparation Works broadly consisted of

  • Bulk earthworks soil improvement/stabilisation (some 220,500m3 of earthworks)
  • Reinforced earth retaining embankments
  • Brownfield remediation and ecological features
  • Site clearance including removal of redundant substructures, foundation, unsuitable demolition materials
  • Diversion of Northern Ireland Water foul sewers
  • Diversion of stormwater culverts
  • Earthworks cut/fill to establish building and hardstanding formation platforms for future main works package
  • Soil improvement/ stabilisation of unsuitable excavated soils to be used for fill
  • Earth retaining reinforced embankments
  • Installation of protection to ecological features
  • Management of asbestos containing material

Achievements

People and Communities

A Community engagement programme was set up by the Department of Education to encourage the local community to become involved in the project. A community stakeholder group was established to encourage cross community engagement. The Stakeholder Group remained active during the Site Preparation Works project, where the Contractor attended the group meetings and kept the group up to date with the progress on site.

Land Use and Landscape

For this project the WYG Environmental Team took an innovative approach to groundwater contamination. The former Lisanelly Barracks site contained a hydrocarbon groundwater plume. The WYG design team of experts further characterised the contamination and carried out a quantitative risk assessment. A robust case was then presented to the regulatory authorities proposing a programme of monitoring during the site preparation works to further demonstrate an absence of risk and support for contaminant degradation through natural attenuation via the collection of additional contaminant and groundwater chemistry data. Since gaining regulatory approval, WYG have since shared this innovative approach with the environmental industry through seminars, presentations at industry events, social media releases and publication articles.

The design team produced a remediation strategy based on offering a sustainable and cost-effective solution whilst maintaining sufficient robustness to ensure the remedial objective of the site were achieved.

The key aspects of the strategy were:

  • Excavate and segregate contaminated soils
  • Capping of contaminated soils (in situ) within zones of proposed fill and exposed during excavation
  • Capping of contaminated soils (re-use on site) within designated re-use zones beneath the proposed synthetic pitched.

This strategy resulted in the maximisation of material reuse on site and minimised off-site disposal. A total of 220,500m3 of material was reused on site.

Ecology and Biodiversity

The site contained many protected and notable species bats, badgers, otters, Atlantic Salmon, smooth newts, nesting birds, trees and the River Strule. The ecological protection measures were therefore of high importance for the project. An ecological constraints and protection plan was produced by the design team to ensure the ecological features of the site were protected. An ecological toolbox talk was delivered to the Contractor to ensure all parties were aware of the protected species on the site. The Contractor worked well with the design team and the statutory authorities and ensured all the required protection measures were put in place including the installation of the paladin fence to provide ling term protection to the badger sett.

The Water Environment

A Construction Environmental Management Plan was agreed with NIEA Water Management Unit, which included an Earthworks Management Plan and temporary SuDs measures that were adopted to mitigate pollution to the local Strule river from construction site works.

Physical Resources – Use and Management (Energy, Water, Materials, Waste)

The earthworks proposals for this project comprised cut and fill ground remodelling to achieve proposed development formation levels for the schools in the Main Works Project. A full site cut and fill analysis was completed to establish the formation levels to ensure minimum volumes of excavated waste to leave the site. To maximise the reuse of unacceptable cut/excavated material for engineering and structural fill there was a requirement to implement Ground Improvement works involving cement stabilised bulk fill and capping layers below the roads, hardstanding, carpark, building footprint and sports pitch areas to achieve the specified CBR at formation level. To ensure compliance with the specification, field tests were completed, and a verification process was established. Engineered fill compaction verification tests, ground settlement monitoring tests and earthworks completion reports were all completed. This process allowed for almost 220,500m3 of material to be beneficially reused on site, which equated to 86% the total fill volume. The additional 14% of the fill material was supplied from local quarries.

Additionally, all suitable topsoil on the site has been stockpiled and stored on site for future use to be used for the Main Works Contract.

This project also included the deconstruction/ crushing of a large area of reinforced concrete yard. This material was crushed on site and the reinforcement metals separated. The metals were sent to a recycling scrap yard and the concrete was crushed and reused on site. Other oversized concrete structures were also crushed and reused on site. The crushed material was used for the construction and maintenance of temporary haul roads and general fill throughout the site. This equated to 99% of the de-construction material from the site to be reused on site.

Did the use of CEEQUAL deliver any financial benefits?

Financial benefits included maximum reuse of site won and demolition material thus reducing the need for imported material resources. Contaminated soils that were suitable for reuse were retained on site and disposed within specified reuse zones and capped in accordance with NIEA consent, and this significantly reduced costs by avoiding disposal off site.

Estimated savings that can be attributed to CEEQUAL

By retaining the contaminated material on site, it contributed to a cost saving of approx. £900k.

Challenges

One of the main challenges for the project was the assessment, verification and management of the contaminated soils on the site. The testing, excavation and movement of the soils was required to be monitored. As such a large volume of material was required to be moved this was a major task.

What were the drivers and perceived benefits for undertaking a CEEQUAL assessment on this project?

The drivers for the assessment were to ensure best practice was embedded and enhanced sustainability approach was delivered from all aspects of the project team

How did the use of CEEQUAL influence the outcomes of the project? What was done differently because of the CEEQUAL process?

  • Ecological surveys and mitigations proposals avoided biodiversity losses
  • Earthworks surface water management controlled using innovative SuDs control measures

What elements of this project highlight best practice and innovation?

Best practice: reuse of site won materials and implementation of Suds for earthworks management and pollution control; detailed ecological surveys to ensure habitants were managed during and after the construction phase