Trenchless Technology

JAN 2019

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60 T R E N C H L E S S T EC H N O LO GY JA N UA RY 2019 N A S S C O R E P O R T AN IMPORTANT ACTIVITY involved in the rehabilitation of sewer pipes is the assurance that flow can be pumped through a bypass system while the work is being done. Additional consid- erations in this process include mini- mizing disruption to traffic in the sur- rounding area, avoiding utilities and protecting the existing infrastructure. Typically the contractor is respon- sible for providing all materials, labor, equipment, power and other services to implement a temporary pump- ing system to divert the existing flow around the work area for the duration of the project. As such, the contractor must submit a bypass plan to the proj- ect engineer which includes locations, elevations, capacity of equipment, ma- terials and all other incidental items necessary and/or required to ensure proper protection of the facilities. The plan should also include information regarding protection of the access and bypass pumping locations from dam- age due to discharge flows, along with information pertaining to compliance requirements and permit conditions specified in these contract documents. An example bypass plan may include: • Staging area for pumps; • Sewer plugging method and types of plugs; • Number, size, material, location and method of installation of suction piping; • Number, size, material, method of installation and location of installation of discharge piping; • Bypass pump sizes, capacity, number of each size to be on site and power requirements; • Calculations of static lift, friction losses, and flow velocity (pump curves showing pump operating range shall be submitted); • Standby power generator size, location; • Downstream discharge plan; • Method of protecting discharge manholes or structures from erosion and damage; • Thrust and restraint block sizes and locations; • Sections showing suction and discharge pipe depth, embedment, select fill and special backfill; • Method of noise control for each pump and/or generator; • Any temporary pipe supports and anchoring required; • Design plans and computation for access to bypass pumping locations indicated on the drawings; • Calculations for selection of bypass pumping pipe size; • Schedule for installation of and maintenance of bypass pumping lines; • Plan indicating selected location of bypass pumping line locations, including proposed vehicle and pedestrian ramps; the plan must show any locations where bypass lines or equipment are located outside of public right-of-way, or existing utility easements; • Any required manholes to be altered for access; • Any required trenching; and • Any required traffic control. Construction should not begin until all provisions and requirements have been reviewed by the engineer. Once approved, preparation may begin and should include the identification of any existing utilities in the area of the bypass pipelines in order to minimize disturbance to those utilities. The ex- isting wastewater system infrastruc- ture must be protected from the by- pass process, as well. NASSCO 's Operations and Mainte- nance Committee is currently work- ing on a comprehensive Specifica- tion Guideline for Bypass Pumping , which will be released next spring. The document will detail the specific requirements, equipment, field qual - ity control, installation and removal practices, and everything else re- quired for successful bypass pumping. We believe this is an important part of NASSCO 's mission to set standards for the assessment, maintenance and rehabilitation of underground infra- structure and to assure the continued acceptance and growth of trenchless technologies. This article was provided by the O&M Committee of NASSCO. By p a s s P u m p i n g : T h e I m p o r ta n c e o f P l a n n i n g S u b m i t t e d b y N A S S C O ' s O & M C o m m i t t e e NASSCO's Operations and Maintenance Committee is currently working on a comprehensive Specification Guideline for Bypass Pumping, which will be released next spring.

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