Inflow & Infiltration (I&I) is a term attributed to rainwater and/or groundwater entering a sanitary sewer system and being treated at wastewater treatment facilities. I&I can come from variety of sources, some are easy to identify while others are not. Some examples of inflow include roof drains, yard drains, missing cleanout covers, foundation drains, vented manhole covers, and combined sewers while sources of infiltration include broken sewer laterals, defective collection pipes, or leaking manholes.
During 2010, Hurt and Proffitt (H&P) completed an Inflow & Infiltration study for the Town of Crewe to evaluate increased wet weather flows for the eastern portion of the collection system. After completing the I&I report, H&P prepared and submitted a Preliminary Engineering Report (PER) to USDA-Rural Development and Virginia Department of Environmental Quality for funding assistance. The Town was awarded $6.3 million for sanitary sewer improvements that included:
• Replacement of 2,900 feet of sanitary sewer pipes
• Cured-In-Place Pipe (CIPP) lining of 34,900 feet
• Rehabilitation of 123 manholes
• 1,015 LF of force main extension
• 20,000 gallon pump station equalization basin
• Pump station telemetry
• Generators
• Maintenance equipment
• 200,000 gallon off-line storage basin at the WWTP
Construction began in late September 2014 and was completed earlier this year. The pump station and rainfall data from the 2010 I&I Study was compared to post construction pump station and rainfall data. For the September to June monitoring periods, rainfall increased from 1.8% (49.4″ to 51.3″) while the pumped gallons reduced 34.7% (49.6 MG to 32.4 MG).
Hurt and Proffitt has five (5) Hach wireless flow meters for placement in sanitary sewers. Once installed, the wireless capability enables H&P, as well as clients, to review the results without having to visit the site. Each meter can also be programmed to send messages when increased flow is observed.
For more information on our flow meters and how we can put them to work for you, contact: Mike Wilson, P.E (434) 847-7796 or mdw@handp.com.
Mr. Wilson has over 24 years of civil engineering experience, including site design, land development, modeling sanitary sewer systems for inflow & infiltration, as well as analyzing and reporting information collected for contaminated sites. His engineering responsibilities include project management, designing and monitoring project infrastructure / construction, review of site plans and construction drawings, and creating documents for municipal sanitary sewer and water main projects.