ADVANCED METHOD OF PROJECTING MANHOLE I/I QUANTIFICATION FOR SPECIFIC STORM EVENTS IMPROVES REHABILITATION PRIORITIZATION SCORING PROCESS

Manholes represent a rather complex structure for assessing its structural condition and
“leakiness” potential. Factors such as the assembly of components with multiple construction
materials and exposure mechanisms to rainfall and runoff make computational scoring and I/I
quantification logic complicated. Manholes have the potential to be significant sources of
extraneous infiltration/inflow (I/I) but it is difficult converting visual inspections into I/I
quantification. The American Society of Civil Engineers (ASCE) 2009 publication titled
Manhole Inspection and Rehabilitation and other publications were used to develop an analysis
tool for assigning infiltration/inflow (I/I) to standard manhole defects and projecting the I/I rates
to vary with specific storm event rainfall frequency, intensity, and duration. The tool also adjusts
the I/I rates depending the defect’s component location and on which one of four rainfall runoff
exposure mechanisms the manhole is exposed; sheet-flow, ponding/tributary limited,
ponding/tributary un-limited, and elevated. The tool’s I/I quantification process and development
basis improves the engineering integrity of rehabilitation cost effective analysis and prioritization
decisions.