EPA distinguishes infiltration (groundwater entering through defective pipes, joints, or manholes) from inflow (stormwater entering through direct connections). Most agencies track the two together, since it is hard to isolate each source's contribution in the field.
Excess I&I eats into a system's usable treatment capacity and is a leading contributor to sanitary sewer overflows. An SSO is a Clean Water Act violation. Many agencies now manage I&I under a formal Capacity, Management, Operation, and Maintenance (CMOM) program, often mandated by a state agency or a consent decree. CIPP, pipe bursting, manhole rehabilitation, and point repairs are the standard toolkit for reducing I&I, so an active I&I reduction program tends to generate a steady, recurring stream of sewer rehabilitation bid work rather than a single one-off project. For contractors specializing in trenchless rehab, I&I reduction programs are a repeatable project type worth tracking across agencies and bid cycles. Nonlinear surfaces that pattern as it reads bid documents and capital plans across a territory.
