Reducing Inflow and Infiltration (I/I) of rainwater and groundwater into the wastewater system is an important function of the City’s Capacity, Management, Operations & Maintenance (CMOM) plan. This aspect of the CMOM plan ensures pipe capacity for wastewater flows and reduces costs associated with the treatment of rainwater and groundwater. Sanitary Sewer Evaluation Surveys (SSES) are used by Public Works staff to identify failing wastewater infrastructure needing repair as a primary method of reducing I/I.
The engineering professional services are to complete a SSES of two metered sub-basins within the North Dallas Trunk Basin for I/I reduction. The survey area consists of approximately 135,000 linear feet of smoke testing, 425 manhole inspections, 5 dye tests and 10,000 linear feet of Closed-Capital Televised (CCTV) Inspections. To help manage costs, existing CCTV inspection data of sanitary sewer mains will be used for assessment when available.
RJN Group, Inc. was deemed most qualified based on their Statement of Qualifications submission for RFQ No. 2021-0379-XR. RJN has also successfully completed SSES projects similar in scope. RJN has extensive expertise in scoring the condition of sanitary sewer infrastructure, planning sanitary sewer systems, designing sewer rehabilitation projects and managing the construction of the projects.
RJN Group, Inc. completed an Inflow and Infiltration Basin Study of the Lower White Rock Creek and Dallas North Trunk Basins in 2021. Based on the analysis of data, excessive inflow was identified in approximately 57% of the monitored area. RJN Group, Inc. has completed two previous SSES studies in this area of excessive inflow and this Year 3 Study will complete the analysis for the area.
If this expenditure is not approved, the City will continue to experience reduced sanitary sewer capacity and pay higher sewer treatment costs for rainwater entering the sewer system during rain events. Sanitary sewer overflows during rain events may also become more prevalent.