New questions have been raised about whether drilling for oil should be allowed in an area of the South Downs that feeds a source of drinking water.
UK Oil and Gas Investments plc (UKOG) has applied for permission to drill new wells and produce oil at Markwells Wood. The site is in the catchment of the Bedhampton & Havant Springs, which provide water to the Portsmouth area.
An independent study for a local community group has concluded that water contaminated by oil exploration or production at Markwells Wood could quickly reach the springs 8km away.
It also argues that the area had been incorrectly classified for groundwater protection and should have greater safeguards that would prohibit drilling for oil.
Markwells Wood Watch, which commissioned the study, has urged the South Downs National Park Authority to refuse planning permission.
In November last year, both the Environment Agency and Portsmouth Water objected to UKOG’s planning application for Markwell’s Wood. They said the company’s groundwater risk assessment was inadequate. The two organisations are expected to comment next week on a revised risk assessment.
Speed of water
The threat to drinking water depends partly on the speed with which any contaminated water could travel underground through the chalk to the Bedhampton & Havant Springs.
Aidan Foley, the author of The Markwells Wood Watch study, estimated that groundwater in the chalk aquifer at Markwells Wood could reach the springs in around 10 days. This is far faster than the Environment Agency (EA) has estimated.
The EA has said it would oppose hydrocarbon development in areas where underground water below a drill site could reach a drinking water source in no more than 50 days. These areas are classified as a Source Protection Zone 1 or SPZ1.
Markwells Wood is classified as a Source Protection Zone 2 (SPZ2), an area within 51-400 days travel time to a water source.
But Dr Foley said:
“There is considerable justification for the designation of the area around the UKOG site as within SPZ1.”
Fissures in the chalk
One way groundwater and pollutants can travel rapidly through chalk is along what are known as karstic features. This is where chalk is dissolved to create fissures and conduits, along which water and contaminants can flow.
Last year, the Environment Agency said if there was strong evidence to suggest karstic flows in the area of the UKOG site it would treat it as if it was in an SPZ1 and oppose oil and gas operations.
UKOG’s revised risk assessment concluded that the chalk near Markwells Wood had “less potential for solution weathering and karstic flows” than other areas in the South Downs.
But Dr Foley concluded that sink holes and dry valleys around UKOG’s proposed site and along the route for vehicles visiting the site were evidence of underground fissures in the chalk.
Dr Foley said:
“All of the geological and groundwater conditions required for karstification of the Chalk Principal Aquifer are in place at Markwells Wood.
“There is an almost complete absence of surface water within the district, with the exception of ‘Winterbournes’ flowing in normally dry valleys during periods of unusually high groundwater recharge, thus indicating that all flow is concentrated in the subsurface”.
Dr Foley said:
“Due to the high groundwater velocities (up to several kilometres per day) that frequently occur within flowing fractures, fissures and conduits, karstic groundwater supplies are among those most vulnerable to pollution.”
He said tracer tests from nearby Rowlands Castle proved that groundwater was travelling more than 12km a day and reaching the springs at Havant in about nine hours.
“The weight of these observations, on the basis of multiple lines of evidence, suggest that karstic groundwater flow conditions, of potentially kilometres per hour, are present in the vicinity of the UKOG site at Markwells Wood.
“There is little evidence to suggest that what takes 9 hours to travel from Rowlands Castle to Havant (a distance of 4.6 km), would take over 50 days to travel from the UKOG site to Rowlands Castle (a distance of less than 3.5 km).”
He said the delineation of the SPZ1 and SPZ2 zones appeared to be based on what he called “incomplete mapping of surface karst features”. He also questioned the basis of the calculations of the transport of contaminants.
Jo Hawes, who lives in Forestside, the nearest village to the Markwells Wood, said:
“The risk of water pollution as a result of drilling for oil is obvious. I believe the local authorities must take a precautionary stance and not allow an oil company to chase short term profits at the expense of our long term health.”
Reed Paget, a member of Markwells Wood Watch, said:
“It is now clear that the groundwater in this region is moving very quickly and if there is an oil spill, the people of Portsmouth could have chemicals in their drinking water in a matter of days. This is far too great a risk to accept. I hope Portsmouth Water and the EA do what’s right for the local population and object to UKOG’s oil extraction proposal next week”.
UKOG gave the following response:
“The report commissioned by MW Watch has been written in response to the old groundwater risk assessment submitted with our planning application in September 2016. However, subsequent to this and following discussions with the Environment Agency and Portsmouth Water, we have carried out a more comprehensive and detailed assessment. This was delivered to the South Downs National Park Authority in early March of this year and is currently being reviewed by both the Environment Agency and Portsmouth Water as part of the statutory planning application consultation process.
“Our assessment, like the report commissioned by MW Watch, recognises the high sensitivity of the chalk aquifer and shows that robust mitigation measures are required to manage the risks associated with our development. Since the wellsite has already been constructed in accordance with modern industry standards, the only potential risk associated with our development relates to the construction of new oil wells through the chalk aquifer.
“This low risk will be managed by constructing new wells using the same techniques used in the water well drilling industry. This will include using a British manufactured, natural, biodegradable drilling fluid in our operations. This zero-hazard water-based drilling fluid is the only drilling fluid to be formally approved by the Department for the Environment, Food and Rural Affairs for use in drilling wells for public water supply and will help to ensure that there is no impact to the Havant & Bedhampton Springs during the drilling process.”
The South Downs National Park Authority is expected to consider the UKOG application on 11 May 2017.
Updated 4 April 2017 to include response from UK Oil & Gas