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Thursday, January 18, 2018

Infiltration & Inflow (I&I)

This page has been revised to reflect the Infiltration and Inflow (I&I) Plan submitted to the OhioEPA as a result of the Director's Final "Finding & Orders"


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Letter One to OhioEPA Letter Two to OhioEPA Plan Summary

Click on Image to the right for the OhioEPA Quarterly Reports on I & I.

Follow this image on that webpage.

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What is I & I?

I & I is clean storm and/or groundwater that enters the sewer system through cracked pipes, leaky manholes, or improperly connected storm drains, down spouts and sump pumps. Most inflow comes from storm water (rain) and most infiltration comes from groundwater. I & I affects the size of the Village of Ashville’s delivery and treatment systems and, ultimately, the rate businesses and residents pay to operate and maintain them. In extreme water flows Sanitary Server Overflows (SSO) were used to provide relief to Walnut Creek. We had at one time three (3) functioning SSO’s. The last Village of Ashville SSO was eliminated in mid 2007. Before that took place we spent twelve (12) months monitoring that location for any overflow. Please see definitions below.stormwater-i-i


The first I, Infiltration, is groundwater, or groundwater that is influenced by surface water that enters sewer pipes (interceptors, collectors, manholes (MH), or side sewers) through holes, breaks, joint failures, connection failures and other openings. Infiltration quantities often exhibit seasonal variation in response to groundwater levels. Storm events can trigger a rise in groundwater levels and increase infiltration flows. The highest infiltration flows are observed following significant storm events or following prolonged periods of precipitation. Since infiltration is related to the total amount of piping and appurtenances in the ground and not to any specified water use component, it is usually expressed in terms of the total land area being served, or in terms of the lengths and diameters of sewer pipe. The unit quantity used in this study is gallons per acre per day (GPAD).


The second I, Inflow is surface water that enters the wastewater system from yard, roof and footing drains, from cross-connections with storm drains, downspouts, and through holes in manhole covers. Inflow occurs as a result of storm events such as rainfall, snowfall, springs or snow melt that contribute to excessive sewer flows. Inflow can also occur in sewer pipes or facilities that are subject to excessive sewage flows due to direct or indirect connections to a water body or operational inflows such as water system connections for sewer cleaning. Peak inflow can occur during heavy storm events when storm sewer systems are surcharged, resulting in hydraulic backups and local ponding.

Steps to Correct I&I

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