Articles & Case Studies

LAND DRAINAGE INSTALLATION SAVES WATER AND PREVENTS WATERLOGGING

Posted: Thursday 7th May 2009

Bereavement is traumatic under any circumstances but the thought that the grave site of a loved one is secure for the future assists many families in the grieving process. Unfortunately changing climate conditions can lead to circumstances where without intervention the security of such interment sites may become compromised due to rising ground water tables leading to waterlogged ground. Without adequate land drainage facilities interment plots could be damaged.

This was potentially the situation at the Surrey and Sussex Crematorium (SSC) in Crawley, West Sussex. Investigations showed that the existing land drainage network was working to capacity and that any increase in ground water levels or flows might overrun the interment plots in the Crematorium grounds. So, to prevent this possibility, the site management decided that a new and improved land drainage system was needed.

As part of the investigation of options for the new installation it was also decided the land drainage system could also be used to feed a water harvesting system. The harvesting system would extract water from the land drainage network at times when the water table was high and store it against times of water need such as in summer when, with future possible climate change, rainfall is predicted to be less. This would enable the site management to maintain a watering regime that would keep the crematorium gardens and interment plots green and pleasant throughout the year.

INSTALLTION WORKS

After careful consideration SSC engaged contractor Blockbusters Contracts Ltd of Glynde, East Sussex to complete the work.

The nature of the project required the contractor to ensure that all installations were completed with deference to the existing interment plots which were landscaped and tended not only by the crematorium management and staff but also by the loved ones of the deceased. So, the work was going to be of a very sensitive nature.

In order to achieve the best control of the new pipe network route and ensure that the interments were not disturbed it was decided to utilise open cut techniques to install the land drainage pipes. These pipes comprised in total some 2,000 m of 100 and 150 mm diameter perforated pipe supplied by Burdens from its Crawley depot.

The installation was designed to ensure that minimum a gradient of 1:100 was achieved across the pipe network which was to be installed at depths varying from 900 mm up to 2.4 m. The pipe route was also designed to ensure that an easement of a minimum 500 mm was left around existing interment sites, as well as ensuring that a similar easement existed in areas where future interments would be placed.

Excavation works were undertaken with a small footprint, track-mounted digger using a narrow bucket and a tipper to minimise disturbance of the ground surface and to keep the trench route parameters as tight as possible. The equipment was hired from Central Plant Hire, a company with which Blockbusters has worked for some 10 years.

Once the pipes were installed on a gravel bed and levelled to the required gradient, all trenches were in-filled with 25 mm shingle wrapped in Terram, a special drainage, soakaway and filtration material which allows water to flow into the land drainage pipes without fear of blockage from detritus in the soils. On the contractor’s part the trenches were then finished to ground level with some 150 mm depth of topsoil. The Crematorium’s gardeners were left to finish the site to the require standard by re-turfing and re-planting as necessary.

The water harvesting system was designed as a 4,000 gal (18,000 l) storage facility including one catchment pot and the harvesting tank, supplied by A & C Pumps. The system was also designed that once at full storage capacity overflow would drain into a nearby existing drainage ditch via a non return valve to ensure no backflow into the harvesting storage tank during the wet season. A secondary pump was also installed to over-pump flows to ensure that the system never fills to the base level of any of the interment plots.

In total the work schedule was about 10 weeks and was valued at over £100,000. Due to the sensitivity of the site with ongoing funerals and a steady stream of mourners visiting plots, Blockbusters agreed a work schedule which included the provision of a ceremony timetable to the site foreman which enabled work stoppages to be made at agreed times so as not to disturb funerals. There was also a facility put in place where mourners would be escorted to interment plots through the work site when necessary to maximise health and safety practices during the project duration.

There was also a need for the installation of de-watering pumps during the works to remove rainfall flows and ground water that might otherwise have caused difficulties in the open trenches.

Ultimately the new land drainage network and the water harvesting system were installed on time and to budget to the satisfaction of all parties concerned.

Commenting on the works for SSC Margaret Baynes, Crematorium manager said: “The project ran very smoothly and we now have the operational drainage system we require. Blockbusters Contracts staff, and in particular Tim Whalin the site foreman, were very quick to respond to any requirements from the crematorium during the works and were always helpful and respectful in dealings with the families. We could not have had a better working relationship during the course of the project.”

For Blockbusters Contracts Ltd Tim Hayes, general manager, commented: “Whilst the project in itself was not one that we felt would bring with it any great technical difficulty it was a very sensitive site. We had to work closely with the SSC management to ensure that funerals continued and that mourners were not in any way inconvenienced or more importantly endangered by the works. I would like to make a special thank you to our crew on site for their efficiency and sensitivity during the work. With the system now up and running the crematorium can now look forward to many years of service to its clients and their families without fear of flooding or water damage to the internment plots.”

Tel: 01273 858822
Fax: 01273 858848
Email: info@blockbusters.co.uk
Website: www.blockbusters.co.uk




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