A large number of culvert pipes are installed every year in North Carolina. In the current research project (RP2022-02: Integration of Repair and Remediation Methods into Pipe Material Selection Approach), a Pipe Assessment and Selection Software (PASS) was developed. PASS accounts for the service life of a wide range of pipe materials (reinforced concrete, galvanized steel, aluminized steel, cast iron, mild steel, aluminum alloy, and polymeric pipes) based on their exposure conditions, and it has been enhanced to account for loading and structural requirements. Additional features of PASS include accounting for the effect of backfill replacement as well as repair and mitigation strategies such as the use of flowable fills and membrane lining of the trench on the service life of pipes. PASS also includes a method to account for the effect of substandard coating for galvanized and aluminized steel pipes on their service life and recommends discount rates based on estimated reduction in the service life. The estimation of the service life of pipe materials in PASS is based on exposure conditions that are assessed using a GIS database linked with jobsite latitude and longitude coordinates to obtain information on soil conditions (including those from nearby quarries.) Alternatively, field measurements of soil resistivity and chloride content can be input directly into PASS. Overall, PASS has evolved into a comprehensive framework for pipe selection. We would like to mention here that while PASS is developed for the State of North Carolina, it can be extended for use in other states by updating the GIS database with information relevant to that state.
We propose herein to integrate the following items into PASS; these ideas have come up during the discussion with NCDOT colleagues:
(i) Currently, PASS does not account for the selection of gaskets, especially in contaminated soils where the presence of Volatile Organic Compounds (VOCs) such as benzene, PCE, and TCE can significantly degrade gasket durability.
(ii) While PASS includes the effects of mitigation strategies such as flowable fill and lining the trench with membranes or clay liners, it does not have a robust process to account for the durability of such measures and the presence of damage in them; this may lead to an overestimation of service life since perfect (damage free) liners and membranes are assumed, but are not realistically achieved in the field.
(iii) PASS does not account for aging effects of polymeric pipes; that is the current service life estimation of polymeric pipes (e.g., HDPE and PVC) is a constant number and does not include interaction with the environment (i.e., moisture and contaminants) nor the effects of creep.
