Infiltration/Inflow Study – Upper East River Valley

WestWater Engineering was part of an engineering team to complete the 201 Facilities Plan for a study area that encompasses five independent collection systems, including the Towns of Crested Butte and Mt. Crested Butte, Meridian Lake Subdivision, Crested Butte South Metro District and the East River Regional Sanitation District.

As part of the 201 study, WestWater Engineering conducted an infiltration and inflow analysis of the 5 separate sewer collection systems that were analyzed independently to determine the quality of I/I and the effects I/I has on each of the five treatment facilities. I/I evaluations generally consisted of reviews of the existing collection system mapping with maintenance personnel to identify the age, size and materials used in construction of sewer pipes and manholes and to develop a systematic flow monitoring plan of suspect areas.

Nighttime flows were measured and recorded at suspect locations throughout each collection system to the extent possible, as well as influent and/or effluent flows at the treatment plants during the same interval.

A cost-effective analysis was completed to determine whether documented I/I was excessive, or if future treatment facilities should be sized to include the extraneous flow. The study also considered the feasibility of meeting 85 percent BOD removal criteria for future discharge permits.