Davenport Sanitary Sewer Inflow and Infiltration Project

The City of Davenport was concerned with increasing wet weather flows to the wastewater treatment plant as well as sewer inundation during periods of heavy rainfall. The City contracted with HR Green to perform a sanitary sewer I&I (inflow and infiltration) study and recommend projects for the removal of stormwater from the system. To gain a better understanding of the sewer network, flow meters were strategically placed throughout the system, and data from the flow meters were then utilized to develop a dynamic sewer model of the project area. HR Green used survey-grade GPS data collectors to inventory manhole and pipe assets in the sewer system and document key infrastructure details within a mobile Geographic Information System (GIS). National Association of Sewer Service Companies (NASSCO)-certified GIS professionals reviewed the asset inventory and applied custom quality control (QC) tools from Environmental Systems Research Institute’s (ESRI) GIS Data ReViewer software extension to identify and correct complicated network errors, thereby preparing a final GIS deliverable conforming to the latest NASSCO manhole and pipeline inspection standards. Following the field inventory and QC review, the GIS database was directly integrated with the project hydraulic model to deliver seamless results. Using the hydraulic model, regions of the City suffering from I&I issues were accurately identified and recommended for further investigation.

Smoke testing, televising, and manual inspections were then utilized to determine specific points of the sanitary sewer I&I and provide detailed improvement recommendations to the system in a Capital Improvements Plan (CIP). The CIP included a complete description of the problems encountered during the investigations including locations, links to investigative data, recommended improvements, relative priorities, and an opinion of probable cost for each. HR Green leveraged the project GIS database to provide a comprehensive database report containing all manholes captured in the asset inventory and was organized by condition rating. The report also detailed all associated tabular attributes, site photos, and field sketches.