Patent ID: 8447533

Claim:
A method of reducing rainwater or ground water inflow or infiltration into a wastewater collection grid comprising the steps of (a) identifying a wastewater collection grid having a configuration comprising a plurality of manholes; (b) dividing said wastewater collection grid into a plurality of major subsystems, said configuration of said wastewater collection grid being such that each of said major subsystems has one of said manholes at an outlet end thereof; (c) installing flow depth level detectors in said manholes at said outlets ends of said major subsystems; (d) using said flow depth level detectors to determine for each of said major subsystems a ratio (ΔQ) of wet weather volume flow rate to dry weather volume flow rate by: (i) measuring for each of said major subsystems using said flow depth level detectors a dry weather flow depth level (Dd) for flow during dry weather conditions; (ii) measuring for each of said major subsystems using said flow depth level detectors a wet weather flow depth level (Dw) for flow during wet weather conditions or during a combination of wet weather and dry weather conditions; (iii) using said dry weather flow depth levels (Dd) measured by said flow depth level detectors to determine for each of said major subsystems a dry weather cross-sectional area of flow (Ad); (iv) using said wet weather flow depth levels (Dw) measured by said flow depth level detectors to determine for each of said major subsystems a wet weather cross-sectional area of flow (Aw); and then (v) determining for each of said major subsystems said ratio (ΔQ) of wet weather volume flow rate to dry weather volume flow rate according to a formula Δ ⁢ ⁢ Q = A ⁢ ⁢ w A ⁢ ⁢ d * ( R ⁢ ⁢ w R ⁢ ⁢ d ) 2 / 3 wherein Rw is a wet weather hydraulic flow radius based upon said Aw and Rd is a dry weather hydraulic flow radius based upon said Ad; (e) using said ΔQ ratios for said major subsystems to at least identify a highest ranking one of said major subsystems which ranks highest in contributing to said wastewater collection grid a greater volume amount or a greater cost amount of said rainwater or ground water; and (f) locating for repair or improvement one or more points of ground water or rainwater flow or infiltration in said highest ranking one of said major subsystems.