Cuadrilla Ltd. Case Study
Groundwater Pollution Protection in the Onshore Gas Industry
By Miles Hillmann, Fosse Liquitrol
Prevention of Pollution from Surface spills.
Experience from the USA indicates the major threat to ground water comes from surface spills where large volumes of contaminated flowback water is handled.
Unlike the USA in North West England, where a number of sites are intent on operating, it rains a lot. Any contaminated water may pollute surface water and so technical guidelines require the whole site to be contained within a bund. All the rainwater and any liquid discharges from operations pass to an interceptor. During hydraulic fracturing operations and in the event of any operational spill the interceptor valves are closed and whole site contains all the liquid.
The most recent hydraulic fracturing for shale gas in the UK was carried out by Cuadrilla near Preston in autumn 2018 and early 2019s. Their site is probably the most environmentally monitored and protected site of all industries in the UK. For up to a year before hydraulic fracturing took place they had monitors in place and were measuring and placing the results in the public domain for natural, background levels of methane emissions, surface and groundwater analysis, air pollution, noise levels and traffic movements.
The groundwater protection plan prepared for the Cuadrilla site involved three levels of containment – tertiary, secondary and primary containment. This is the most comprehensive groundwater protection plan and concept was adopted by the Environment Agency in their Technical Guidelines for containment on Onshore Oil and Gas Sites.
A drainage plan was produced for the whole site providing for drainage of the complete site into an interceptor. Polluted liquid is taken off the site to specialist treatment plants.
The whole site was contained by oil and chemical proof sheeting laid on a geotextile underliner for protection.
Gravel is laid on the membrane and an open ditch feeds to the interceptor.
Within the site the working areas are protected by secondary containment using Ultratech Containment Walls in the Frack Farm and Flowback Tanks where containment of tanks in line with Control of Pollution (Oil Storage) Regulations 2001 was required and gorilla berms to contain spillage from the Frac Kit.
Ultratech International are a US company who pioneered the field of spill containment products in the early 1980’s. They are world leaders in spill containment and their Containment Wall System is used throughout the oil, gas, water and associated industries internationally.
Fosse Liquitrol are their partners in the UK and are market leaders in spill control in the UK.
The drainage plan provided for two types of secondary containment. On the frack tank farm and where the flowback water tanks are located, the Oil Storage regulations require containment of 110% of the contents of any one tank or 25% of the total volume of all the tanks. This is provided by Ultratech’s fully enclosed containment wall system. In the operational areas where access is required by vehicles, secondary containment is provided by Ultratech’s gorilla bund system.
Ultratech’s containment wall system consists of 3 ft modular walls laid out to the specific dimensions required by the containment area.
A geotextile membrane underliner was then laid to protect the liner
A 1 mm Atarfil LLD liner manufactured from maximum quality linear low density polyethylene LLDPE resins, duly contrasted, complies with the most rigorous requirements established for their use. Atarfil LLD contains 97,5% of pure polymer, and approximately 2,5% of Carbon Black, antioxidants and thermal stabilizers. The product does not contain plasticizers or fillers that can migrate over time.
This liner was laid over the underliner and welded into position
CQA records were kept of the liner laying process and the welds were sampled by the site tensometer.
The liner was secured to the walls by clamps on the walls
The tanks to be contained were positioned in the containment walls.
In working areas Ultratech’s gorilla berm system was used. Gorilla berms were laid across the entry to the working area to provide secondary containment whilst allowing access of heavy machinery.
Once laid the berms provide secondary containment in working areas
These three levels of containment – primary, secondary and tertiary – and the Ultratech containment wall and gorilla bund systems provide groundwater protection that equals or exceeds any level of water protection required in the petrochemical, mining and construction industries in the UK or USA.
Miles Hillmann is the MD of Fosse Liquitrol and Chairman of the Pollution Control Group of the Spill Control Group of the British Safety Industry Federation and also is a member of the Environmental Leadership Group of the UK Onshore Oil and Gas. This group provided the consultation to the Environment Agency in preparing the Technical Guidelines for Containment on Onshore Oil and Gas Sites.