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Salt storage caverns are constructed within deep salt bed deposits by circulating fluid to dissolve the salt deposit. The resulting cavern or reservoir is used to store hydrocarbons and liquefied petrochemicals within the salt deposit. A salt cavern is constructed by dissolving the salt deposits underground and extracting the resulting brine solution and placing it into a holding pond. Layfield was tasked with lining a below ground storage pond in Ontario, Canada to prevent leakage and potential contamination of underlying aquifers. The brine storage pond was lined with a double liner system that consists of a geosynthetic drainage composite encapsulated between two layers of geomembrane. The drainage composite monitors and captures any leakage through the primary or overlying geomembrane and the secondary or underlying geomembrane contains the leakage that occurs through the primary geomembrane.
There were a series of challenges during the design phase for this large brine storage pond including:
1. Selection of geosynthetics and method of fabrication, e.g., factory fabrication v. field fabrication
2. Chemical resistance of the geosynthetics to the brine
3. UV resistance of the primary geomembrane due to the long-term exposure and weathering in this exposed application.
4. Performance of the geonet within the drainage composite when subjected to high compressive stresses and the sediment in the brine solution.
5. Local weather conditions, which included higher than average rainfall, resulted in the site being completely saturated in the fall months, but the owner wanted the pond operational by early Spring of the following year.
Available data from the manufacturer shows that the transmissivity of the geonet is 20 times higher than that of a double-sided drainage composite, i.e., a geonet with two non-woven geotextiles. A drainage composite has at least one non-woven geotextile heat-bonded to the top or bottom of the geonet, which over time can intrude into the geonet causing a reduction in transmissivity. Initial designs included a double-sided drainage composite, i.e., two heat-bonded geotextiles, between the two 40 mil (1.0 mm) thick geomembranes. Layfield proposed just using a geonet to prevent geotextile intrusion and maintain the full transmissivity of the geonet over time. However, questions were raised about the possibility of a flexible 40 mil (1.0 mm) thick geomembrane deforming into the openings of the geonet and reducing its transmissivity or the geonet puncturing the geomembrane at the places where seams of the geonet overlap and create a bump. Layfield simulated this possible puncture situation in the laboratory (see Figure 1a) and the test results show that the geonet overlap did not puncture the geomembrane at the field stresses (see Figure 1b). Based on the laboratory testing, a geonet instead of a double-sided drainage geocomposite was encapsulated between the two layers of geomembrane to create a double-liner system with a leak detection zone for this brine storage pond.
Due to difficult site conditions, Layfield proposed using factory fabricated geomembrane panels in order to: minimize the amount of field welding, increase quality of the seams and final liner system, and meet the short project construction schedule (see Figure 3). Factory fabrication involves welding rolls of the geomembrane into large panels in a controlled environment, which increases seam quality and allows faster seaming. The seam quality is better because the welding is not affected by weather changes, dirt and other impurities in the seam area, and a constant temperature so the welding temperature does not have to be varied. This results in higher efficiency and quality of the seams in the factory than in the field (see Figure 4).
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The Fabricated Geomembrane Institute(FGI) is pleased to welcome its newest College/University Member, Prairie View A&M University, Department of Civil & Environmental Engineering. Prairie View A&M University is the second-oldest public institution of higher education in the state of Texas. It is an Historically Black College and University (HBCU) consisting of nine colleges and schools and 70-degreeprograms. The Department of Civil & Environmental Engineering offers a Bachelor of Science degree in Civil Engineering. The Roy G. Perry College of Engineering offers a Master of Science in Engineering degree with concentrations in Civil Engineering as well as Environmental Engineering. The Civil& Environmental Engineering faculty are committed to excellence in teaching, research, and service to the university and its constituents. The FGI Liaison is Dr. Jobair Bin Alam, PE, Assistant Professor. He can be reached at mdalam@pvamu.edu. Please help us welcome Prairie View A&M University’s Department of Civil & Environmental Engineering to the FGI!!!!
Report from Biennial FGI Meeting - February 24, 2021
The Fabricated Geomembrane Institute (FGI) held its biennial membership meeting on 24 February 2021 during the Geosynthetics 2021 Conference. The meeting was attended by 26 people and held in conjunction with the Industrial Fabrics Association International organized conference. During the membership meeting, the newly elected FGI Officers and Board of Directors were introduced for their two (2) year term.
Before introducing the new Officers and Directors, Timothy D. Stark, FGI Technical Director and Professor of Civil Engineering at the University of Illinois at Urbana-Champaign, acknowledged the service of the outgoing Officers and Board Members: Greg Scales (Titan Environmental), Bill Shehane (Seaman Corporation), and Ed Silva (E Squared). Tim also acknowledged the recent retirement of John Heap from Colorado Lining International. John served as President of the PVC Geomembrane Institute(PGI) for four (4) years and was instrumental in expanding the PGI to the Fabricated Geomembrane Institute. The newly elected FGI Officers will serve a two-year term (2021-2023) and are:
The following newly elected FGI Board of Directors also will serve a two-year term (2021-2023) and are listed below in alphabetical order:
Other topics on the FGI’s Biennial Meeting agenda included: current and future research activities, accomplishments since the last membership meeting at Geosynthetics 2019, and the future direction and goals of the FGI.
The following research topics are being pursued by the FGI at the University of Illinois at Urbana-Champaign:
· fPP Case History
· fPP Air Channel Seam Testing
· PVC Specification for Desert Applications
· Reinforced Geomembrane Thermal/Wrinkle Testing
Other accomplishments of the FGI over the last two years include:
· Publication of several technical articles and papers
· Hosted short courses in Bogota, Colombia and Charlotte, North Carolina
· Publication of three new geomembrane calculators for cost comparisons, leakage rates, and panel weight shipping
· Publication of Installation Details and Drawings
· Created Geo-Engineering Audio and Video Podcast Series
· Created Geo-Engineering Pop Quiz Series
· Hosted 23 live webinars, averaging 250 attendees and 450 registrants per webinar
· Created on-line PDH Certificate Program with about 500 people receiving a PDH Certificate for downloading and listening to a webinar
· Created Women in Geosynthetics Program – hosting two successful Round Table Discussions and quarterly virtual meetings
The final portion of the FGI Biennial Membership Meeting was dedicated to a lively discussion on the future direction and goals of the FGI by its members. The FGI has five membership classifications: manufacturers, fabricators and Installers, Installer Only, Associate, and Government/Regulatory Agency. The FGI’s membership spans four continents: North America, South America, Australia, and Europe.
The FGI is dedicated to advancing the use of fabricated geomembranes through education, research, and technology transfer. The FGI is a consortium of manufacturers, fabricators/installers, designers, regulators, and material suppliers of fabricated geomembranes. For more information on the FGI, please visit www.fabricatedgeomembrane.com.
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