Geo + Pipeline 101
Geosynthetics often play an important role on the environmental side of pipeline installations. During construction, actions must be taken to protect water quality, stabilize soil, and prevent soil erosion.
Pipeline right-of-ways traverse many different types of landscapes, passing through sensitive resource areas such as streams and wetlands. Geosynthetics are used in a variety of situations from start to finish on a pipeline construction project and they aid in water filtration, prevention of soil erosion, and resource protection.
Geosynthetic materials are typically used as a barrier to prevent unwanted material from entering resource areas or unapproved areas. For example, silt fence is often used for perimeter control. Silt fence may be used to keep soil within the construction limits or, more commonly, to serve as a barrier, slowing down sediment-laden water and promoting infiltration. Woven geotextile fabric is also used to line bridges over stream crossings to contain and prevent soil from falling into a waterbody as equipment passes over.
The impermeable type of geosynthetic materials have many applications during pipeline installations. They are often used to construct secondary containment structures for fuels and pumps near waterbodies or to keep contaminated material separated. Impermeable plastic sheeting material can also be used to contain inadvertent fuel spills or leaks in situations where equipment needs to be staged or parked near a sensitive resource area for an extended period of time.
Geosynthetics are also used during water pumping and pipeline stream-crossing activities. Geotextile filter bags are commonly used to treat sediment-laden water prior to pumping water off-site. The effectiveness of treating sediment-laden water depends on the weave density of the filter bag. Most filter bags do not filter out clays, only sand and silt sized particles. In addition to a filter bag, secondary measures should be taken to treat sediment-laden water prior to discharging off-site or into a waterbody. These additional measures may include placing filter bags in lined straw bale dewatering structures or well-vegetated areas to allow for particle settling and infiltration, or the use of polyacrylamide. In situations where high-velocity discharge from a pump or filter bag could result in soil erosion, a layer of plastic should be installed over the ground surface to prevent scour and allow the water to disperse.
Constructing pipelines through streams involves a significant amount of planning and environmental oversight. Geosynthetics are a key component to maintaining environmental compliance and protecting resources. Most commonly, stream flow is diverted and pumped around to allow equipment to dig through the streambed.
Bladder-type cofferdams are a popular option for streams with rocky or uneven substrate because the bladder dam molds to the channel to effectively block streamflow. Impermeable geosynthetics are installed on stream banks and bed to protect the vegetation and the integrity of the bank, as well as to prevent scour of the streambed.
The applications of geosynthetic materials for pipeline installations are numerous. Although geosynthetics are commonly used for permanent and long-term stabilization, they serve an integral role in protecting resources from temporary earth disturbance. Most of the environmental challenges that occur on a pipeline project can be addressed with one of the many geosynthetics available.
Virginia Brown, M.S., is an environmental scientist who provides environmental compliance inspection on oil and gas pipelines as well as electric transmission lines. She presented on this topic at the IECA’s Environmental Connection 2016 conference in San Antonio, Texas.