Drainage and Sewerage Issues

Many sites do not have main drainage. Consequently, it is desirable for run-off from roofs, roads and/or effluent from a septic tank or sewerage plant to be discharged to the ground or a water course. However, many criteria have to be assessed in order to achieve a good result, namely:

• The site must have a sufficiently large area to locate the soakaway, septic tank, sewerage treatment plant and its drainage field, a legally minimum distance away from a buildings, water course and water supply.
• The soakaway, septic tank, sewerage treatment plant and its drainage field must be a legally minimum distance away from environmentally and archaeologically sensitive sites.
• The water table should be sufficiently below the base of any discharge drain or borehole, even in the wettest winter.
• The ground must be sufficiently permeable to take water from a soakaway and drainage field of a septic tank but not too permeable, otherwise treatment is reduced.
• Discharge from a septic tank and/or a sewage treatment plant may need additional treatment to enable discharge to the ground.
• The slope of the ground must be suitable.
• Run off from roofs will probably not need treatment prior to discharge to the ground via a soakaway.
• Run off from roads is likely to need the installation of an oil trap and a sediment trap, prior to discharge to the ground. Drainage from septic tanks and/or small scale sewage plants over 2 cubic metres per day will need a discharge licence from the EA and this will not be granted in unsuitable locations.
• It is important that the site is investigated in order to determine its suitability, prior to deciding upon a septic tank sewerage treatment plant and/or a soakaway.