This article contains the most common questions regarding site settings, such as Aquifer Designation, Bedrock Geology, Ecological Features, Geological Permeability, Groundwater Vulnerability (SPZ), Source Protection Zones and Superficial Deposits.
Aquifer Designation
Question: What is an aquifer?
Answer: An aquifer is a body of porous rock or sediment saturated with groundwater. Groundwater enters an aquifer as precipitation seeps through the soil. It can move through the aquifer and resurface through springs and wells.
Question: What do the types of aquifer mean?
Answer: The type of aquifer at your location will affect how vulnerable it is to pollution and how much is available to abstract.
Question: Principal Aquifer
Answer: Regionally extensive aquifer or aquifer system that has the potential to be used as a source of potable (drinkable) water.
Question: Secondary A
Answer: Comprise permeable layers that can support local water supplies, and may form an important source of base flow to rivers
Question: Secondary B
Answer: Mainly lower permeability layers that may store and yield limited amounts of groundwater through characteristics like thin cracks (called fissures) and openings or eroded layers
Question: Secondary Undifferentiated
Answer: Aquifers where it is not possible to apply either a Secondary A or B definition because of the variable characteristics of the rock type. These have only a minor value.
Question: Unproductive strata
Answer: Largely unable to provide usable water supplies, and are unlikely to have surface water and wetland ecosystems dependent on them.
Question: Unconfined and confined aquifers
Answer: Aquifers can be unconfined or confined, or a mix of both.
Question: Unconfined aquifer
Answer: When the upper surface of the aquifer (and water table) is open to the atmosphere either directly or through permeable overlying material. Because of this, it’s more vulnerable to pollution than a confined aquifer.
Question: Confined aquifer
Answer: Overlain by a low-permeability material (for example, clay) that does not transmit water in any appreciable amount. It’s less vulnerable to pollution than an unconfined aquifer because there is greater protection.
Bedrock Geology
Question: What is bedrock?
Answer: The relatively hard, solid rock beneath surface materials such as soil and gravel
Question: Common bedrock we see in our reports?
Answer: Mudstone - Hardened mud; a mix of silt and clay-sized particles.
Sandstone - Clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains
Clay - Fine-grained natural soil material containing clay minerals./ Clays develop plasticity when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or firing.
Silt/Siltstone - Granular material of a size between sand and clay, and composed mostly of broken grains of quartz
Sand - Granular material composed of finely divided mineral particles
Ecological Features
Question: SSSI
Answer: Site of Special Scientific Interest. Conservation designation denoting a protected area in the United Kingdom.
Question: National Character Area
Answer: Natural subdivision of England based on a combination of landscape, biodiversity, geodiversity and economic activity. There are 159 National Character Areas, and they follow natural, rather than administrative, boundaries.
Question: Priority Habitat
Answer: UK BAP priority habitats cover a wide range of semi-natural habitat types, and were those that were identified as being the most threatened and requiring conservation action under the UK Biodiversity Action Plan (UK BAP)
Geological Permeability
Question: Permeability definition
Answer: Whether and how water can flow through a rock (BGS).
Question: What are the Permeability Flow Types?
Answer: Intergranular - Flow between grains - through the interconnected pore spaces between solid grains in a material
Fracture - Rock flow through a fractured rock
A mixture of intergranular and fracture flow - See above
Maximum permeability index - highest potential vertical rate of fluid migration through the unsaturated zone of a rock
Minimum permeability index - the likely slowest rate of vertical water flow through a geological unit.
Source Protection Zones (SZP)
Question: What are SPZ's?
Answer: Groundwater zones which show the level of risk to the source from contamination. This could be from any activity that might cause pollution in the area. For example, storing pollutants like petrol underground, soakaways from septic tanks to the ground. The closer the activity, the greater the risk.
Question: Why is Groundwater important?
Answer: Groundwater supplies a third of our drinking water. In some areas of southern England, up to 80% of the water you get from your taps is from groundwater. It also keeps many of our rivers flowing. The Environment Agency must protect groundwater sources used to supply drinking water from pollution.
Question: What types of Groundwater sources are there?
Answer: Wells, boreholes and springs.
Question: What Zones are there?
Answer: SZP 1 - Inner > This zone is 50 day travel time of pollutant to source with a 50 metres default minimum radius.
SZP 2 - Outer > This zone is 400 day travel time of pollutant to source. This has a 250 or 500 metres minimum radius around the source depending on the amount of water taken.
SZP 3 - Total Catchment > This is the area around a supply source within which all the groundwater ends up at the abstraction point. This is the point from where the water is taken. This could extend some distance from the source point.
Superficial Deposits
Question: What are they?
Answer: Geological deposits typically of Quaternary age (less than 2.6 million years old). All pre-Quaternary deposits are referred to as bedrock.
Question: Diamicton
Answer: A type of siliciclastic sediment and sedimentary rock. Sediments that are poorly sorted and contain a wide range of clast sizes can be given this root name, from clay to boulders.