designated service area. 

In order to understand fully the issues raised on this appeal, it is necessary to review the NPDES permit history of the Village’s treatment facility, as well as the history of the facility itself.

The original treatment facility was built in 1926; it was last upgraded in 1978.  The facility is located in a residential area.  Construction of a new facility on the site is not possible since under current regulations the entire site is in a flood plain.  The sewer system, which is a tributary to the facility and which was constructed in 1926-27, allows for more than the normal amount of infiltration of storm water and groundwater flow.  When the facility was redesigned in 1977, it was determined that it would be easier toupgrades."  

The Village appealed the NPDES permit conditions to the IPCB, and a hearing was held on September 17, 1997.

Daniel Hughes, the superintendent of water and sewer for the Village, testified and explained how the facility operated.  He noted that, due to the use of biological contractors in the water treatment process, the process is less effective during the winter because the cold slows down the metabolism of the microorganisms used in the process.  He further explained that hydraulic capacity of the facility was 1.25 mgd, which means that the facility is designed for an average flow of 1.25 million gallons of wastewater per day.  The 9,900 P.E. rating is the organic loadings and refers to the CBOD and suspended solids loadings.  According to Mr. Hughes, the facility