If you’ve driven along Helpston Heath Road recently, you may have seen a drilling rig in the fields at the junction with Stamford Road. This work was undertaken by the Environment Agency and is associated with a major pollution incident at the nearby landfill sites known as Ben Johnson’s Pit and the Ailsworth Road Waste Disposal sites.
Water Treatment Plant in Ben Johnsons Pit
Back in the early 1980s, these two sites were used to dump domestic and industrial waste. One industrial producer alone disposed of tonnes of agrochemical waste into the disused limestone quarries.
Unfortunately, the exposed rock in these quarries is part of a bed of very porous Lincolnshire Limestone that, to the east of the site, dips beneath the ground to form a huge underground aquifer. It’s from this extremely prolific source, beneath our villages, that Anglian Water takes a large part of our drinking water. Historically, the water from this aquifer has been known for its purity, and was once bottled and sold as natural soda water; it also provided local artesian water for Peakirk, Glinton and Helpston (See Tribune Issue 52, page 29).
In 1988, traces of the agricultural herbicide mecoprop was detected in Anglian Waters’ boreholes at Waterworks Lane, Etton. The Ailsworth Road and Ben Johnson Pits waste disposal sites, some 2km away, were identified as the source of this pollution.
The pollutants had leached out of the landfill site through the porous limestone directly into the aquifer. To prevent the levels of mecoprop rising above the UK drinking water limit of 0.1 micrograms per litre, the boreholes at Etton were taken out of the supply network until new water treatment equipment was fitted. Following treatment, the levels of mecoprop were reduced to well below the UK limit, and the treated water continues to be safe to drink.
However, given our ever-increasing water consumption, and our over-use of existing sources, the Environment Agency decided to take remedial action to reduce the contaminants, and prevent it spreading further into the aquifer. Doing nothing could have resulted in the complete loss of the aquifer as a water supply, and the pollution of surface water via wild bores (uncontrolled boreholes).
Using complex computer groundwater modelling, and laboratory scale trials, a strategy for containment and treatment of the pollutants was established. In 2003 work started on the solution, this involved drilling 15 boreholes around the waste disposal sites, and pumping water out, along with the contamination, into a purpose-built treatment works. There, the polluted water is treated to reduce the contamination down to safe levels.
The process of biodegrading the mecoprop, and another contaminant ammonia, is assisted by the, rather surprising, addition of molasses to the water. The clean, treated water, is then returned to the pond in Ben Johnson’s pit.
By pumping water from the 15 boreholes at a high enough rate, around 350 cubic metres per day, a ‘hydraulic’ barrier is created. It is hoped that this will fully contain the contaminated groundwater in the vicinity of the site, and ensure that there is no further expansion of the pollution in the aquifer.
If this pump-and-treat system fully contains the pollution then it’s estimated it could take 10 to 15 years to naturally reduce the contaminates in the aquifer to safe levels; however, the pump-and-treat system may need to operate for up to 30 years. At the moment it’s too soon to say if the system is working but it looks as if all than can be done, is being done. Once the contamination is fully contained then remediation may be accelerated by directly removing pollutants from the pits.The cost of all this work to the taxpayer could exceed £10 million. Anglian Water’s costs in removing the mecoprop from drinking water have been estimated at over a million. The company who dumped the waste into the quarries went into liquidation in 2003.
The Tribune was given a special guided tour of the treatment works and was impressed by the Environment Agency’s enthusiasm and commitment to this project, and we hope this dedication brings about the success it deserves. We were also reassured that the Anglian Waters supply is, as its always been, perfectly safe to drink. The Tribune will, of course, keep you informed of progress, as well as details of any new work to speed up this essential work. The total cost of this clean up may explain why the UK operates strict anti-pollution legislation - saving money by dumping waste materials in a hole in the ground could cost us all a great deal more.
Bob Randall
Acknowledgement: Special thanks to Allison Hukin, and her colleagues in The Environment Agency for their invaluable assistance.
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