Welding HDPE geomembranes with biogas present

April 1st, 2022

Q: We are a Brazilian company specializing in biogas plants. We have built a big lagoon biodigester with a high-density polyethylene (HDPE) geomembrane cover. Now the cover is leaking liquid contained in the lagoon: We are organizing the repair procedure, and we would like to first investigate state-of-art practices and procedures for welding HDPE geomembranes […]

Read More

NSF 61-certified HDPE geomembranes

April 1st, 2022

Q: Hi, we are looking for options for NSF 61-certified high-density polyethylene (HDPE) liners for installation in a potable water tank, 95th-percentile concentration of free chlorine in the tank is 1.2 ppm (1.2 mg/L). The current liner (60-mil [1.5-mm] textured HDPE, installed in 1999) is damaged and needs to be repaired or replaced. We are […]

Read More

Impregnation of GCLs

April 1st, 2022

Q: We are confused with the term “impregnation” as it relates to seaming geosynthetic clay liners (GCLs). There are two types of impregnations: (1) Edge impregnation, and (2) complete nonwoven (cap layer) impregnation of GCLs. How does a manufacturer do this? A: The edge impregnation of GCLs (1) is done in the field by an […]

Read More

GCL-GM geocomposite: Which end is up?

April 1st, 2022

Q: In a geosynthetic clay liner-geomembrane (GCL-GM) geocomposite, does it make any difference which side of the geocomposite is up: GM or clay? A: This is a very detailed question that is application specific. The following design details all need to be considered: Is the GCL-GM geocomposite used for a liner or a cover, is […]

Read More

Calendared nonwoven geotextiles

April 1st, 2022

Q: What is the difference between normal nonwoven and calendared nonwoven (both needlepunched) geotextiles? Where can we use calendared nonwoven geotextiles? A: Calendared nonwoven geotextiles are passed between a set of heated rollers that applies normal pressure as a tertiary process of the production. This process increases the modulus, strength, tear resistance, puncture resistance and […]

Read More

LCC curing effect on geogrids

April 1st, 2022

Q: Can you tell me whether modest warming of geogrids (e.g., due to heat generated by the curing of lightweight cellular concrete [LCC]) might impact the long-term strength or long-term modulus of geogrids? A: You need to know the maximum temperature due to the heat from hydration of the LCC. Most pozzolanic reaction temperatures (like […]

Read More

High pH effects geogrids?

April 1st, 2022

Q: Can you tell me whether the high pH of curing portland cement (typically ~12.4) might have any impact on the long-term performance of geogrids? A: It depends on the geogrid and its formulation. There are three categories of geogrid: (1) punched and drawn (polyethylene [PE] uniaxial, polypropylene [PP] biaxial and triaxial), (2) strap (polyvinyl […]

Read More

Methane gas geomembrane permeability

April 1st, 2022

Q: What is the least permeable geomembrane to methane gas? Regarding the permeability of geomembranes to methane gas, could you send me some technical guidelines? A: High-density polyethylene (HDPE) geomembranes are denser (more crystalline) than linear low-density polyethylene (LLDPE) geomembranes and less permeable. The water vapor, solvent and methane transmission (diffusion) of an HDPE barrier […]

Read More

Scratch impact on HDPE liners

April 1st, 2022

Q: I have a project where multiple and extensive scratches were created on the high-density polyethylene (HDPE) liner for a reservoir due to poor construction practices. (See the following Figures 2–4.) FIGURE 2 Construction equipment that caused scratches at crest of slope FIGURE 3 Overview of scratches in 60-mil (1.5-mm) high-density polyethylene (HDPE) conductive liner […]

Read More

Fusion-welded HDPE geomembrane patch

February 1st, 2022

Q: I need to make sure of what the minimum area is for a fusion-welded HDPE geomembrane patch with a 60-mil (1.5-mm) thickness that should be fusion welded instead of extrusion welded. Also, when does one need to replace a panel that is damaged (i.e., the percent of damage allowed to be repaired)? Thank you […]

Read More