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Performance Mapping the Wastewater Collection Grid
Since both the EPA and the American Water Works Association suggest a “Systems Approach”
for locating major sources of inflow and infiltration (I&I), Eastech’s Engineering Group decided to
follow this identical approach. Wastewater collection systems selected for investigation are
initially divided into separate Sub-Systems (major basins) and then again into Mini-Systems in
order to cost-effectively ascertain the most prevalent areas of unwanted ingress.
I&I Location, Volume and Cost Analysis
Extensive international studies of inflow and infiltration have proven in case after case that the
80/20 Principle usually applies (approximately 20% of the wastewater infrastructure network
contributes 80% of the I&I). These extensive studies only confirm the economic value of
implementing a structured Performance Mapping approach.
Initially, a portable iTracker I&I Detection Monitor is placed at the base of each major Sub-System
within the overall collection grid. iTracker level monitoring is conducted for a minimum period of
five consecutive dry days in order to establish a “dry weather” baseline for calculating a pattern
of diurnal flows completely absent of I&I. The identical procedure is then repeated for a period of
three consecutive months of combined dry and wet weather. Once the collected data is gathered
and transferred through flash card technology to CostView’s Analysis Program, Delta Q algorithms
categorize by volume and cost the extent of I&I effecting each major Sub-System.
Municipal managers are now capable of initiating the process of pinpointing the probable
20% of the collection grid contributing the major portions of inflow and infiltration.
iTracker
I&I Detection
Monitor
Sub-System Isolation
One iTracker is placed at the base
of each major Sub-System
Mini-System Isolation
One iTracker is placed in
every 10th manhole
40
30
1 10
20
6
Manhole with iTracker