Oftentimes I'm asked why it is important to complete manhole inspections. Manhole inspections should be performed during wet weather, or when the groundwater level is at its peak. Ideally November to May is the better time for manhole inspections to detect inflow and infiltration. With the snow/ice melt in February and March compounded with heavy rains cities and towns will experience peaks at the lift stations and wastewater treatment facilities. Below is a list of the five most important items that to look at during manhole inspections that will help reduce inflow and infiltration, or eliminate potential backups. One of the most observed items during a manhole inspection is the manhole chimney. As you can see below, the manhole was constructed of precast with the exception of the manhole chimney that was constructed out of brick. During dry weather it may appear to be in good shape; but when the groundwater rises or heavy rains appear you will see a different story as shown below. Example shown below of a brick chimney at the start of a rain event, and after the rain has set in for 30 minutes...hard to believe it's the same manhole with slightly different conditions. The inflow that was observed to the right measured 7 gallons a minute.
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