A two-storey farmhouse with an outdoor garage was our next project. The farmhouse was situated in a rural area of Rushton with similar residential properties in close proximity. The property sat on a sloping ground with neighbouring properties situated at higher ground in relation to the farmhouse. The property was separated from the nearest property by a retaining wall which backs onto a 3m bank on top of which resides the nearest residential property. There is also a septic tank situated on the elevated ground behind the retaining stone wall which could pose a risk to health. Our surveyor was contacted by the client and asked to inspect and carry out microbiological sampling on the property.
On arrival at the property our surveyor observed evidence of water seepage from the bottom of the retaining wall and onto the stone driveway of the property. There was also a noticeable effluent type of odour present in the rain water drains of the property.
Methodology for Microbiological Sampling
Our surveyor collected microbiological samples for the evaluation of effluent contamination using Sterilin Transport Swabs Amine W/O charcoal and transported to the laboratory under temperature controlled conditions. The microbiological samples were then plated onto Tryptic Soy Agar (TSA) and cultured at 28-30C. Once cultured for 3 days a bacterial count and identification could be carried out. Our surveyor was evaluating the samples for the presence of Escherichia Coli and Faecal Streptococci Bacteria which are closely associated with sewage and human waste. A 1 litre sample of drain water was also collected to be analysed for total biological oxygen demand (BOD). Biological oxygen demand is an indicator of organic matter and microbiological contamination of water.
Conclusions and recommendations based on microbiological sampling
Based on the results of the microbiological sampling we concluded that E.coli bacteria was present at the bottom of the retaining wall. However E.coli bacteria can originate from natural environmental sources. The samples collected from the rain water drain, located at the bottom of the retaining wall, indicated the presence of effluent bacteria such as faecal enterococci. This group of bacteria can be confidently linked with effluent contamination of the water in the rain water drains. We did not find any evidence that faecal streptococci was present in the samples we collected however the biological demand analysis was indicative of high level contamination and of effluent contamination. It was in our surveyor’s opinion that the rain water drain contains sewage contaminated water which is the main source of odours in the courtyard of the property.