Summary of hydrogeology report, “A Review of Karstic Potential and Groundwater Vulnerability of the Chalk Principal Aquifer in and around Markwells Wood, West Sussex.”produced by Dr. Aidan Foley, Environmental Geology & Geotechnical Consultants Ltd, for Markwells Wood Watch
Background
The focus of the report is to establish the extent of karstic features in the geology in and around Markwells Wood.
Karstic features are channels in the chalk that allow water to flow more quickly underground. It is important because groundwater in the Chalk flows into the Havant & Bedhampton springs which supplies most of Portsmouth and the surrounding area. They are one of the largest spring sources used for public water supply in the whole of England.
The Environment agency (EA) designates water catchments into Source Protection Zones (SPZ). An SPZ 1 is an area where groundwater takes 50 days or less to reach a groundwater resource such as the springs.
The EA’s position is that drilling for oil should not take place in an SPZ 1 area. However they do consider exceptions. These require “substantial mitigating factors.”
At present, Markwells Wood is in a designated SPZ 2 area, defined as groundwater taking from 50-400 days to reach the springs.
This report supports the view that this designation is incorrect.
The Report Findings
1. The report shows that “all of the geological and groundwater conditions required for karstification of the Chalk Principal Aquifer are in place at Markwells Wood.”
2. Karst features were studied in detail in the Rowlands Castle/Horndean areas for a previous Landfill proposal. Studies showed that water could reach the springs as quickly as 9 hours.
3. There is no evidence to show that water from Markwells Wood would take 50 days or more. Markwells Wood is about 8km from the Havant and Bedhampton Springs. (Rowlands Castle is 4.6 km)
4. A number of reasons were found to support the view that the designation of Markwells Wood as an SPZ 1 area is incorrect. One is that the detailed studies were all in the Rowlands Castle/Horndean area and the area around Markwells Wood was not surveyed in this detail.
5. The study showed considerable support for the presence of karst around Markwells Wood. i. The presence of numerous “dolines”. These are depressions or pits in the ground. Water can travel down these and into the underlying chalk, rather than over the surface. ii. Maps show a broad band of land with very little surface water. This is considered a “dry valley”. This means that water is travelling below the surface. Markwells Wood is in this band.
6. A very cautious estimate, based on data that is available, is that water from Markwells Wood could take about 10 days to reach the Havant and Bedhampton springs.
Using a nationally published Groundwater Vulnerability Scoring system the report concludes, “Taking the mean gives a classification of High Vulnerability. Nonetheless, even a Moderate Vulnerability score is significant in terms of the proposed development. “
Additional Considerations
There are risks during all stages of oil production during transport, drilling, stimulation and storage of chemicals, hydrocarbons, hazardous injection fluids containing very strong acids, flowback and produced liquids (flowback fluids are likely to contain additional pollutants and pose additional impacts due to the possible release of heavy metals, salts and radioactive material in the acidizing context.)
We think there is sufficient evidence to show that any of these risks represent an unacceptable hazard. The precautionary principle should be invoked.
The claim that this development is “conventional” is highly debatable. Horizontal drilling and advanced well stimulation are generally considered features of unconventional oil developments.
Our “back of the envelope” calculation of the oil expected is 0.015% of U.K. annual consumption. This is one hundredth of one percent.
(Based on an average of 230 barrels per day over 20 years [UKOG’s estimate] and 1,500,000 barrels crude oil consumed in the UK in 2013 http://www.indexmundi.com/energy/?country=gb&product=oil&graph=consumption)
We do not consider this to be sufficient reason to endanger the local water supply.
Markwells Wood Watch
Stoughton Parish