Essay On T3 Test Hole

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The purpose of this assignment was to determine whether a site located on LIT Tipperary’s Thurles campus, was suitable or not for an onsite wastewater treatment system. The assessment onsite predicts the wastewater flow through the subsoil and into the subsurface materials if a wastewater treatment system was to be put in place (EPA, 2009). The site characterisation process our class used is only applicable to a single house. I was assigned to the T3 test hole. The result in the texture test meant that the modified percolation test had to be carried out for silt/clay subsoil found onsite in LIT Tipperary.

Deviations from Procedures
According to the EPA code of practice (2009) the T test hole should have the following
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The hole was pre-soaked on the 22/2/16 at 2:15 and dropped 10mm by 3:00 when it was refilled and left overnight to soak. On the 23/2/16 we resumed work at 9:00 and it was clear that the water had not fully soaked away with 100mm water still present at the bottom. Mud had to be removed from the bottom of the hole before we proceeded to the percolation test. The hole was filled to 400mm at 9:23. From our observations the water level was very slow dropping down throughout the day. After the first hour the level had only dropped by 22mm. The level dropped a further 18mm between 10:30 and 11:50. The level dropped by 20mm from 11:50 to 14:04 and by 14:23, five hours after the start of the test the level had only dropped by 65mm. The T3 test hole failed to drop 100mm in the first five hours of the test which meant it failed as an average T value of >90 would have been …show more content…
This appears to make sense as bedrock was found while digging and a large rock lined the bottom of our T3 test hole. The bedrock present was possibly poorly permeable explaining why the level did not soak away in a sufficient length of time.
The steps involved in the site characterisation are a desk study which allows the collection of information about the site such as maps and then an onsite assessment is carried out (EPA, 2009). A visual assessment of the site was first carried out by the class where surface features were identified.
From the visual assessment carried out by the class on site in Thurles Campus the class made the following observations:
• There are no rivers or streams in close proximity, there are hedgerows present around the field, there is a gentle East facing slope in the field, poaching has occurred around the headlands of the field due to horses being present, waterlogging doesn’t seem to be an issue at the top of the field however as the slope moves down in an eastern direction waterlogging has taken place over the last few weeks. This may indicate surface run off on site. There is no evidence of bedrock above the ground surface or no outcrops are present. There are no rushes present at the top of the field where the proposed percolation test will take

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