Underground Services Check?
Before any intrusive site work using a mechanical excavator can commence a full underground services search must be completed. Premier Water Solutions can organise this, if required and a risk assessment and method statement must be prepared before going to site. This is undertaken in house and is a requirement for compliance with the HSE.
Site investigations are required to design infiltration (soakaways) solutions. There are two types of infiltration testing and these are highlighted below:
Surface Water (CIRIA 156)
Infiltration testing in accordance with CIRIA 156 will require a JCB, tractor and water bowser. Test holes will typically be in the region of 2.5m (l) x 2.5m (d) x 0.8m (w) and water is filled to approximately 1m depth. The time is recorded to monitor on how quickly the water infiltrates into the sub soil and is usually expressed in m/hr.
Surface Water (BS 6297)
If the area draining to a soakaway is less than 100m2 then this method can be appropriate. This is useful if designing a soakaway for a small domestic extension, for example. Test holes 0.3m x 0.3m x 0.3 are dug in the bottom of a test hole at the approximate depth of the position of the soakaway. For example, when designing filter strips at surface level, test holes can be at the surface and for traditional soakaways where there will be underground pipework, the test holes would need to be dug at the approximate depth below ground - usually about 1m below ground level. These tests are less intrusive and require less water volume so standard water containers will suffice rather than the tractor and bowser.
Foul Water (BS 6297)
A 0.3m cube must be hand dug in the base of a 1.0m deep trial hole and water from a water container should be poured into the hole, timing how quickly the water depth decreases. This will provide a result in s/mm and provides a Vp. For sizing soakaways for foul water it is important to know that the water cannot drain too fast where the Vp is less than 10 or too slow where the Vp is greater than 100.