Catchment hazards

Contamination from a variety of activities or places can occur at any point throughout a water supply system if it is not adequately protected, managed and/or maintained. This document provides some of the key measures that can be undertaken to prevent and remediate the main forms of contamination that pose a risk to a private water supply.

Catchment risks

Microbiological contamination

Microbiological contamination from faecal material can lead to illness. The following is a list of examples of actions that will assist in preventing contamination of the source:

• Employ regular inspection and maintenance of septic tanks, at a frequency that is in accordance with the manufacturer’s instructions.
• Installation of stock proof fencing to protect the water source from grazing animals, including rabbits and deer as well as domestic livestock.
• Prevent storage and/or the spreading of manure within 50 metres of the water source.
• Restrict the access of livestock from the vicinity of the source. This may be up to 50m depending on ground conditions, topography, presence of swallow holes etc.
• Eliminate or relocate storm water overflows away from the water source;
• Construct embankments, walls or ditches to prevent surface water entering spring collection chambers or borehole headworks.
• Raise the well head or borehole head-works to at least 0.5 metres above ground level to prevent surface water or spillages of contaminated material entering into the water source.
• Construct storage lagoons or tanks for untreated source water to allow settlement of sediment and organic matter ahead of any treatment.
• Design tanks, storage chambers and borehole head works to prevent access from all animals, including rodents, invertebrates etc. This document contains more specific advice about borehole design and protection.
• Cover and backfill or seal any abandoned boreholes or wells to prevent surface water contamination of the aquifer.
• Limit or control recreational use of the source water near the intake point (surface water supplies).
• Locate surface water intakes where they are least exposed to possible contamination from up-stream activities, such as surface water run-off, effluent discharge points, or other polluting activities.
• For rainwater harvesting systems, remove or avoid the use of roof-mounted aerials or overhanging trees in the water collection area. Birds should be discouraged from perching on roof collection areas as droppings will contain bacteria. Also consider installing mechanisms to divert the first flush of rainwater to a waste system. Approved materials (e.g. WRAS or permitted under Regulation 5) should be used to prevent the contamination of rainwater during runoff and collection.

Chemical contamination

Some chemical contamination can lead potentially to illness or other long term health effects. Some of the following improvements at the water source will assist in preventing them from entering the water supply:

• Establish with the environmental regulator whether any discharges from licensed facilities, such as industrial premises exist in the catchment area.
• Limit or control recreational use of the source water to prevent contamination e.g. boat fuel spillages.
• Limit or control the use of pesticides, herbicides and fertilisers within the catchment.
• Construct facilities (e.g. bankside storage) to enable intakes to be closed if surface water is contaminated.
• Create a run to waste facility for borehole or spring chambers to prevent contaminated water (e.g. after pesticide or fertiliser spraying) entering into supply. NB. Any discharges to waste may need to be agreed with the environmental regulator.
• Locate surface water intakes where they are least exposed to possible contamination from up-stream activities, such as surface water run-off, effluent discharge points, or other polluting activities.
• All stored fuels or oils within a 50m radius of the source should be adequately bunded to prevent leaks from contaminating the supply.

Physical contamination

Contamination by physical particles can lead to the water becoming unacceptable in appearance, taste or odour, and may act as a substrate for micro-organisms to live on and replicate. Some of the following improvements at the source can be effective in preventing them from entering the water supply:

• Install screens or filters for rainwater harvesting systems; protection of inlets and the setting up of a cleaning regime for any collection gutters will help prevent/reduce ingress of organic matter into the system.
• Construct storage lagoons or tanks for raw surface? water to allow settlement to occur.
• Regularly maintain treatment equipment e.g. cartridge filters need to be cleaned or replaced according to manufacturer’s instructions.
• Install screens and covers on storage tanks to prevent ingress of particles, insects and other small animals etc.
• Regularly carry out visual checks, inspections and cleaning of storage tanks at suitable intervals to reduce sludge or sediment build-up.
• Consider using valves and/or level sensors to help prevent stagnation of water and ensure water turnover occurs.