Erosion and Sediment Control
Managing Construction Stormwater on Pipelines
Linear pipeline construction projects provide many challenges in managing construction stormwater. The Stormwater Pollution Prevention Plan (SWPPP) must employ multiple features to address construction for various land use and soil types, sub watersheds, terrain extremes, and environmentally sensitive areas (ESAs). Multiple construction phases occur throughout long linear pipelines; thus, phasing and sequencing must also be incorporated in the SWPPP to address these operations. Access roads must be constructed and maintained throughout the project duration. This presentation will feature design and implementation tips for stormwater professionals working on pipelines.
Non-structural BMPs can be implemented as project specifications and provisions to minimize stormwater pollutants from entering ESAs. For projects or portions of projects located in ESAs, special procedures are required such as limiting and the amount and duration of ground exposure, delayed entry, phased seeding, and immediate permanent stabilization following final grade establishment. These non-structural BMPs apply to clearing and grubbing, temporary stream crossing, and grading operations within sensitive areas.
Historically, many linear projects have involved grading the full length of the corridor while only constructing discrete sections, leaving the majority of the project in an openly graded, exposed unstabilized state. Careful phasing and sequencing must be outlined in the project narrative to steer the contractor towards compliance. Incorporating three SWPPP phases to address clearing and grubbing, mass grading and trenching/boring/drilling, and final stabilization are recommended. Specific BMPs are utilized in each phase to address the unique challenges associated with the respective phases. Detailed phasing must also be addressed for trenching through wetlands and streams. Several examples will be illustrated during the presentation.
Special BMPs and practices must be incorporated in ESAs to provide protection for these jurisdictional areas. Delineation and flagging of riparian buffers are always required as an initial step. Delayed entry into riparian buffers has served as a protective measure to preserve stream side vegetation. Contractors are allowed to fell trees but no grubbing activities may occur in a fifty-foot zone on either side of the stream or wetland. Once grading activities commence in this zone, the work must be pursued in a continuous manner until reaching final stabilization.
Lessons learned associated with implementation and maintenance of erosion and sediment control practices will be highlighted. An emphasis will be placed on temporary groundcover, , clean water diversions, velocity control with water bars or slope breaks, flocculant use, sediment storage, stockpile management, and staged permanent stabilization. Tips for supplemental treatment for areas draining to adjacent farm ponds and waterbodies will be discussed.
Many pipeline projects utilize horizontal directional drilling (HDD) or trenchless construction methods. Inadvertent releases (IRs) of drilling fluids pose a high risk for impacts to ESAs. IR Release Plans that contain recommendations for containment, recovery, and restoration will be explored.