Featured Technical Topics

Update PFAS and PFOS Regulations & Compliance

Update PFAS and PFOS Regulations & Compliance

Timothy D. Stark
February 2, 2024

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Update PFAS and PFOS Regulations & Compliance”. This topic generated significant discussion with the main “take-aways” being listed below:

PFAS Regulations

- No regulations promulgated yet so no compliance activities yet

- Proposed PFAS/PFOS rules released on 1/31/2024 – see excerpts below and full document at: prepublication_version_of_definition_of_hazardous_waste_proposal.pdf (epa.gov)

- Proposed rules released on 1/31/2024 do not classify PFAS/PFOS as a hazardous waste for disposal so they can be disposed in a Subtitle D facility (see pasted text below)

- See recent article on PFAS/PFOS regulations HERE.
- New drinking water standard lowers allowable level of PFAS/PFOS to 4 parts per trillion, which is hard to detect

- Kerry Rowe’s testing at Queens University shows many geomembranes exhibit good chemical resistance to PFAS/PFOS compounds (see FGI webinar that Kerry Rowe gave at this LINK.

- However, Kerry Rowe’s testing shows lower concentrations of PFOS exhibit higher diffusion rates than higher concentrations of PFAS through the geomembranes that he has tested

- Need long-term testing of geomembranes chemical resistance to PFAS/PFOS chemicals

- PFAS/PFOS somewhat new and predate geomembranes so PFAS/PFOS may be in prior chemical resistance testing that used actual leachate instead of synthetic leachate

- Some water agencies are asking if any geomembrane component is extractable PFAS/PFOS material over the service life of the geomembrane

- Manufacturers are being asked if PFAS/PFOS chemicals were used in geomembrane manufacturing? Manufacturers are reviewing their supply chain to confirm no traces of PFAS/PFOS due to requests of customers and regulators – manufacturers are issuing “to the best of our knowledge” letters about no PFAS/PFOS components

- National Sanitation Foundation (NSF) is pursuing extractable constituents and may include PFAS/PFOS – NSF 61

- NSF 61 is having training class in Michigan on April 24, 2024, which my address PFAS/PFOS

- Would be good to investigate water standards in Europe and Australia and how they are handling PFAS/PFOS

- Would be good to investigate municipal solid waste standards and compare them to water standards

- Military will be exempt from PFAS/PFOS regulations initially

- Any changes in geomembrane formulations to deal with PFAS/PFOS, none available yet

- Lots of litigation over PFAS/PFOS are underway

- Health impacts of PFAS/PFOS are starting to become understood

- No new placement restrictions at Subtitle D facilities for PFAS/PFOS compounds but a lot of Not In My Backyard (NIMBY) opinions because leachate will go to local treatment facility

- It is believed that PFAS/PFOS could have a large impact on waste and water industries

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Determining Lining/Floating Cover Systems for Critical and Non-Critical Applications

Determining Lining/Floating Cover Systems for Critical and Non-Critical Applications

Timothy D. Stark
January 5, 2024

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Determining Lining/Floating Cover Systems for Critical and Non-Critical Applications”. This topic generated significant discussion with the main “take-aways” being listed below:

 Non-Critical Applications

·        Relevant Factors/Questions:
-            Site Specific Determination – Activate ancient landslide or fault system? If so, critical application
-            Does the owner accept some leakage?
-            Regulations don’t require zero leakage?
-            What is the cost of a leak (environmentally or economically)?
-            What is allowable (regulation)/acceptable (owner) leakage rate?
-            What is subgrade condition? Soft, hard, existing asphalt, existing concrete, does it need remediation? If so, may be critical application
-            What is geomembrane being selected?
-            Site specific CQA/CQC requirements – depends on GM selected but usually less than critical applications
-            Is site specific Leak Location Testing necessary? – depends on site
-            Choice of material depends on availability, e.g., available soil v. GM

 ·        Non-Critical Applications:
-            Canal liners
-            Temporary remediation
-            Decorative ponds
-            Landscape ponds
-            Detention basins – control flow
-            Stormwater collection – depends on level of contamination – natural and man-made
-            Wetland mitigation
-            Dewatering
-            Freshwater containment if water is readily available
-            Final cover systems
-            Floating cover system for non-potable water – site specific

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Discussion of Subtitle D

Discussion of Subtitle D

Timothy D. Stark
December 1, 2023

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Discussion of Subtitle D”. This topic generated significant discussion with the main “take-aways” being listed below:

1.       Discussion Topics for Subtitle D

·        Subtitle D became effective in the late 1990s and thus is over thirty years old.

·        Subtitle D is followed in Canada but some of Europe has more stringent requirements than Subtitle D, e.g., Germany

·        A discussion of Subtitle D was convened to identify various requirements that might be clarified or updated

·        States can implement their own requirements if they are equally or more stringent than Subtitle D, i.e., Federal = minimum level – states can have different requirements, e.g., CA, PA, NY

·        As a result, clarifications and/or modifications can be initiated at the state level

·        Only major change in Subtitle D since its promulgation is inclusion of: Project XL Bioreactor Landfill Projects as are search and development initiative

 ·        First requirement discussed involved the Flexible Membrane Liner component of a composite liner system – under “Design Criteria”, the requirement is: “the upper component must consist of a minimum 30-mil flexible membrane liner (FML).” FML components consisting of high density polyethylene (HDPE) shall be at least 60-mil thick. The FML component must be installed in direct and uniform contact with the compacted soil component.”

Some of the suggestions for clarification and/or updating of this requirement include:

-      Replace 60 mil HDPE with at least 40 mil thick unreinforced or reinforced LLDPE b/c better dimensional stability, i.e., “direct and uniform contact”

-      Change requirement to be engineering property based instead of polymer and thickness based, e.g., make FML requirement to be a performance specification like compacted soil component, i.e., saturated hydraulic conductivity “of no more than 1x10-7 cm/sec”

-      Main advantage of HDPE = chemical resistance so require FML performance based on 9090 US EPA testing - immersion test with SW846 - https://www.epa.gov/hw-sw846/sw-846-test-method-9090a-compatibility-test-wastes-and-membrane-liners- Use landfill gas condensate for 9090 testing because more aggressive than bottom leachate

-       Can use different types of FMLs for the primary and secondary composite liner systems, e.g., 60 mil HDPE or 40 mil LLDPE for primary liner system and 30 mil or 40 mil thick FML (PVC, EIA, PP,LLDPE, WCPE, etc.) for secondary liner system

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Use of Geomembranes and Geosynthetics in Energy Applications

Use of Geomembranes and Geosynthetics in Energy Applications

Timothy D. Stark
November 3, 2023

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Use of Geomembranes and Geosynthetics in Energy Applications”. This topic generated significant discussion with the main “take-aways” being listed below:

 

1.       Use of Geomembranes and Geosynthetics in Energy Applications

Hydropower

Solar Power – white reflective geomembranes below solar panels increase solar capture

o   San Antonio Landfill – fPP-R cap and acres of solar panels – TVA 300 acres site

o   Closure turf – solar panels on artificial turf instead of on the ground – sure grip geomembrane from AGRU holds panels inplace

o   Solar panels on rails so they can be placed on 3:1 slopes – flat panels only on crest - https://watershedgeo.com/products/powercap/

Pumped Storage Hydropower (PSH) projects –

o   Use geomembrane for bottom liner system but flow velocities are difficult

o   Use floating cover to reduce evaporation

o   Mt. Elbert PSH project = bottom liner system with18” soil cover to project geomembrane from high flow velocities– 240 acres – installedin 1980 - chlorinated polyethylene (CSPE) geomembrane

o   Traditional pumped storage liner system =asphalt and concrete

o   Research topic – conduct 40-year costanalysis for Mt. Elbert PSH project – initial cost v. decrease loss of water &no seepage into old landslide in hillside b/c of slope instability concerns

o   Forebay/water conveyance projects – typically use asphalt or concrete liner system, which will eventually crack and leak –geomembrane installed to replace cracked compacted clay liner

Gas collection in landfills – near surface gas collection to capture methane

Coalfired powerplants – bottom liner systems – single composite bottom liner system– GM & clay

Oil and gas applications – geomembranes

Secondary containment – oil and gas

Wind Power = application uncertain for geosynthetics

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Electrical Leak Location Surveys with Flexible Geomembranes

Electrical Leak Location Surveys with Flexible Geomembranes

Timothy D. Stark
October 6, 2023

Electrical Leak Location Surveys with Flexible Geomembranes

Electrical Leak Location Surveys (ELLSs) can be performed with flexible geomembranes, i.e., non-HDPE geomembranes; if an HDPE geomembrane is used, it should be white to reduce wrinkling, which is discussed below:

  • In fact, it is easier to “leak locate” flexible geomembranes because they usually exhibit a greater amount of intimate contact with the subgrade, i.e., they lay flat, and exhibit smaller wrinkles that do not have to be removed as HDPE geomembranes do.  
  • In general, it is difficult to perform a ELLS with wrinkles greater than 3 inches high because they cannot be “walked out” and there is no intimate contact with the subgrade.
  • ELLSs are independent of geomembrane polymer type, the main limitations are wrinkles and the geomembrane being a good insulator.
  • However, ELLSs cannot be performed on two types of geomembranes; conductive geomembranes and EPDM geomembranes because of the large amount of carbon black.

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Best Practices for Dealing with Temperature Fluctuations During Installation and Service Life

Best Practices for Dealing with Temperature Fluctuations During Installation and Service Life

Timothy D. Stark
July 7, 2023

Best Practices for Dealing with Temperature Fluctuations include:

  • 50-degree temperature swings can cause  significant changes in GM dimensions  
  • never backfill anchor trench until GM has experienced two or three days of temperature cycles
  • install wrinkle across the toe on short slopes and then cut it out if needed on long slopes, place wrinkle further upslope because wrinkle will not move upslope
  • fill containment with water or other material to stabilize GM as soon as possible
  • include 3 to 3.5% extra unreinforced GM material (slack) for thermal contraction when large temperature fluctuations are anticipated
  • calculate the wrinkle height using the equation from Giroud and Wallace (2016) so the coefficient of thermal expansion for each GM type, interface friction angle, e.g., smooth v. textured, bending modulus, and material type, are important parameters in the calculation

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Longevity of Geonets and Geotextiles

Longevity of Geonets and Geotextiles

June 2, 2023

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Longevity of Geonets and Geotextiles”. This topic generated significant discussion with the main “take-aways” being listed below:

1.           Longevity of Geonets

·        Little performance specifications

·        No longer using an AOS requirement; no FOS

·        Civil v. Environmental grade geotextiles -

·        What is happening under the geomembrane?

·        Research – check embedment of geonet on GM without a cushion GT – when to transition to a composite

·        Industry moving to composites from sands and gravels – so check compatibility of nets with flexible GMs – Brian and Rohit webinar on net and 40 mil GM

 2.           Longevity of Geotextiles

·        Little performance specifications

·        No longer using an AOS requirement; no FOS

·        Civil v. Environmental grade geotextiles -

·        Are geotextiles chemically resistant to liquidsbeing contained?

·        Kerry Rowe – double composite liner system – GCLgeotextile decomposed

·        No specs to excavate and check the geonet andgeotextile

·        Intercell berm excavations look good –

·        Compatibility b/t net and GTs – Polyester & Polypropylene GTs -

·        Compatibility b/t net and GMs – use same resin for both – no spec requiring same resin as GM

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Leak Testing of Mechanical Attachments & Pipe Boots

Leak Testing of Mechanical Attachments & Pipe Boots

Tim Stark and Maya Innis
May 5, 2023

Leak Testing Mechanical Attachments

- Cannot conduct electronic leak locate survey near metalattachments because of interference so need some other type of testing ofattachments

- Place ballast tubes around penetration, inject airbelow geomembrane, soap the attachment, and watch for bubbles along or aroundattachment

- Thermal imaging – not tried yet but possibly effective onsunny day to measure cooler air being pumped below geomembrane and exiting atleak(s) along attachment

- Vacuum below the geomembrane in tank or attachment and listen for vacuum sound along attachment

- Vacuum Acoustic Leak Identification (VALID) method – apply vacuum between primary and secondary geomembranes and listen for vacuum soundalong attachments; tests both geomembranes; the top surface of the geomembrane is scanned with ultrasonic microphones that can detect distinctive sounds of a vacuum leak.

 - Smoke Test – smoke exits at attachment surrounded by ballast tubes

- Spark test with material embed but cannot be used at landfills and oil and gas sites

- Vacuum boxes for strips and corners but limited because not straight segments for box

- Dye test – divers places dye along attachment or concrete joint and see if dye disappears into attachment or crack (see video)

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