Infiltration design guideline - Observation well
Infiltration practices should include an observation well, consisting of an anchored 4- to 6-inch diameter perforated PVC pipe fitted with a lockable cap installed flush with the ground surface. See MNDOT Manual Section 3248 for design guidance on PVC pipes. It is recommended to install one well per 50 feet of length in the infiltration practice.
The purpose of the observation well is to monitor water drainage in the infiltration practice. Check observation wells within the specified drawdown time (24 or 48 hours) after a storm event. Standing water in the well is an indication of clogging of the infiltration system. Observation wells should not be used for water quality monitoring since monitoring wells extend into underlying groundwater.
Examples of details for observation wells can be found at the following websites.