The Public Works Department maintains the wastewater collection system for the City of Clive. All wastewater flows are transported through Clive in pipes ranging in size from 8" to 30" to the Wastewater Reclamation Facility in Des Moines.
The Wastewater Collection System provides for safe collection and transmission of wastewater through the City's underground sewer mains, collectors and interceptor lines. Systematic operations and maintenance programs help protect the capital investment and keep the system in good working order to provide consistent customer service and prevent overflows and backups. The purpose of the Wastewater division is to maintain the collection system in such a manner that protects the public safety, health and the environment. The City of Clive sanitary sewer collection system serves 15,447 residents in 4,909 residential units and numerous commercial businesses on nearly seven (7) square miles. The collection system is made up entirely of gravity mains ranging in size from 6” to 42”. The total length of the public collection system is 391,009 feet or 74 miles, with 1676 public manhole structures.
The function of the collection system is to collect, contain and transport waste water to a point for treatment. The function of this system is to keep waste water in a pipe and groundwater and surface water out providing an uninterrupted flow. Having a routine pipe inspection program can substantially affect the operations of a wastewater collection system. Some of the problems that may affect operation and maintenance of the system include: cracked pipe, broken or missing pieces and offset sewer joints connections that leave large gaps. Some operation and maintenance (O&M) defects include heavy roots, grease buildup, foreign objects not normally found in sewer. All these conditions have the potential to lead to sewer blockages that can then lead to sewer backups into basements or overflows out onto the surface of the ground. Time spent on a proactive CCTV inspection program will minimize time spent on emergency situations that have an effect on utility customers and the financial resources of the city.
Sewers need regular cleaning to prevent stoppages that create backups into basements or sanitary sewer overflows (SSOs). Collections systems use water to dissolve, carry in suspension, push, pull and drag solids. Well designed sewers are self-cleaning; they move solids easily. They have good slope and a low friction loss. Hydraulic conditions deteriorate over time as solids build up in the system. Dirty sewers are less efficient and lose their carrying capacity. The ideal 2 feet per second flow is considered self-cleaning. Slow, sluggish flows allow solids to settle out. This debris acts like a brake on the incoming flow, further slowing velocities. The end result is a dirty pipe gets dirtier.
Pipeline RehabilitationIn 2003, in cooperation with the City of Urbandale, the city began a pipeline rehabilitation program. Using historical data and other information collected during the inspection process, areas of the system were identified as being in need of rehabilitation. The method selected for the rehabilitation work was Cured-In-Place Pipe Relining. A felt tube is manufactured to fit inside the existing sewer main. The tube is soaked in a polyester resin, fed through the main, and finally cured and hardened inside the pipe with the use of heated water. This new pipe-within-a-pipe has an expected life span comparable to that of new sewer main. The system provides a new joint free sewer main without the expense and inconvenience of open cut pipe replacement.