- Billy Nichols of the Philadelphia Water Department (PWD) attended and discussed proposed regulations for geomembranes used in stormwater containment applications.
- Billy is in the water resources team & working on green infrastructure systems that intercepts storm water before water reaches storm water system
- Stormwater Detention System is a system that retains stormwater until stormwater system can handle the flow
- Detention Systems are fully-lined with a geomembrane - The geomembrane liner system is installed to protect nearby basements, prevent sinkholes, etc.
- Use of geomembranes is new to PWD
- PWD tested completed systems since 2020 and some of the systems are not holding water => the test involves filling the completed system with fire hydrant water before placing it in service
- PWD is running leak test after stone installation – to reflect stone placement and stone weight on geomembrane with full weight of water
- However, it is difficult to find leak with stone in-place = must vacuum out stone to locate and fix the leaks
- Old Allowable Leakage rate = 1 inch/hour = f(size) = ?
- Moving to new Allowable Leakage rate of < 0.5 inch/hour
- 143 systems and 216 tests performedso far and 73 systems failed on first filling or testing
- 70% of systems pass initial leakage test (see figure below)
- Leakage mostly occurring at:(1) Pipe penetrations, (2) failed extrusion welds in a tight space, and (3)holes or tears in the geomembrane
- Extrusion Welds = common failure points
- PWD thinking thicker material is better because more material to weld to
- PWD Specification says use fusion welds where possible to minimize extrusion welds
- PWD considering requiring cushion geotextiles on side walls as well as bottom on storage chamber
- Applications: storm trench (PWD and public projects) v. storage chambers (private projects)
- Storm trench used within roadway Right-of-Way = public system not private system
- Primarily 40 mil and 60 mil thick HDPE geomembranes have been used for storm trenches
- PWD Weld Testing = ?
- spark, vacuum box, and air channel testing specified but tests may not be performed

- Suggestions:
‍- A 12 ounce/yd cushion geotextile is a cost-effective protection for the geomembrane
- Field fabrication should be considered to minimize field extrusion welds
- Atlantic Lining Company(ALCO)  has installed many of these systems– Tim Rafter of ALCO shared his experiences with Philly contractors, different geomembrane polymers, and system water testing
- PWD Testing = ? PWD water test not ASTM but developed to test final product
- PVC tube installed in stormwater trench to measure water level every five minutes and filled system sits overnight to measure leakage rate
- Tim Rafter thought a 30 mil GM could not stand up to Philly contractors and thus thought a thicker geomembrane was a good idea
- Terry Sheridan of Geo-Storage described some of his geomembrane experiences designing subsurface storage chambers
- Terry is only working on private projects so new PWD regs don’t impact his private projects
- Terry thinks 40 mil PVC Geomembrane and a thick cushion geotextile are adequate for stormwater containment systems
- Terry suggested using more flexible geomembrane due to better puncture resistance, pipe boot welding, andlarger tensile elongation, which is good with a rising groundwater level

TOPIC:    Geomembranes/Regulations for Stormwater Containment

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Geomembranes/Regulation for Stormwater Containment”.This topic generated significant discussion with the main “take-aways” listed below:

Concerns/Suggestions for Geomembranes/Regulations for Stormwater Containment

- Terry Sheridan ofGeo-Storage described Villanova Conference on Stormwater Containment and presentation by Philadelphia Water Department (PWD)
- PWD is issuing a 2025 regulation requiring a minimum 60 mil thick geomembrane for stormwater chambers
- Terry Sheridan has designed10 to 20 chambers and 2/3 of them are lined with 30 mil PVC GM and two cushion geotextiles, i.e., above and below the GM
- Terry says design needs a flexible GM to resist uplift due to groundwater rise
- Angular aggregate is placed on top of the GM so a thicker cushion geotextile is needed on top
- Contaminated sites but water is not leachate so chemical resistance is not a GM issue
- 60 mil will be difficult to form and weld in below ground chambers
- 30 mil PVC GM can be factory fabricated, which facilitates construction
- William Nichols at PWD is handling the new GM regulations
- 90 to 95% of chambers have the GM placed on the side and bottom of the chamber
- 5 to 10% of chambers have the GM wrapped around the top of the chamber and along the sides and bottom of the chamber

- Application/Function =retention (usually unlined) or detention (GM lined)
- Stormwater Management Trend= store stormwater underground
- Chambers are 3 to 5 ft deep and vary in size from small to large
- Need highly flexible GM materials– PVC, flexible LLDPE, and polypropylene are recommended due to geometry changes, groundwater uplift, and rough subgrade
- A lot of detail work, e.g., pipe penetrations, so a flexible GM is preferred
- Require 30 mil flexible membrane liner (FML) to William Nichols at PWD
- 30 mil PVC geomembranes are readily available around Philadelphia so cost effective for chambers
- Two local installers install the factory fabricated PVC GM panels
- Tim Rafter at ALCO uses 40 mil PVC GM – include in Department Meeting
- Mark Ramsden at EGI – works with
- GM Requirements – no concerns about UV exposure or chemical resistance so flexibility is the key attribute
- Corner of chambers at 90-degreeangles so high-density materials could stress crack
- Need to quantify flexibility using FGI flexibility testing

- Field CQA requirements = ?Fill system with water and monitor rate of leakage, which must be less than 1inch/hour – Volume = ?
- Air lance and vacuum box testing the installed GM

- PWD Discussion Topics: (1)GM flexibility, (2) GM thickness and (3) allowable leakage rate
- Straw Poll of FGI Members that have used 60 mil GM in this application?
- 60 mil PVC and unsupported EIA GM –requested by engineer
- 45 mil reinforced polypropylene = thickest used by Cooley
- If require 60 mil, GM would have to be PVC, EIA, or polypropylene GM
- Thickness increasing to protect against puncture so include thicker cushion geotextile
- Create Technical Note on Geomembrane Flexibility – Function and Importance

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Terminology and Applications for Used Geomembrane Polymers”. This topic generated significant discussion with the main “take-aways” listed below:

Terminology for Thermo-Plastics and not Thermo-Set Plastics:
‍- Thermo-Set Plastics can’t be reworked or recycled due to reinforcement so repurpose them
- Reworked = material from like product internal to the manufacturing process but not after field/external usage; could be wrong formulation or scarp material so a “prime product”
- Reground = edge trimmings, startup scraps that from manufacturing process and has not left the factory
- Recycled = material from like product after field/external usage, melted and reformed thermos-plastics but properties degrade with every re-use
- Repurposed = after field application – same product cleaned and using it in a different application, e.g., billboard film being used as a wood pile cover
- Reprocessed = after field application - cleaned, reground, and remanufactured for less critical application - landfill geomembrane reprocessed for a less critical application, e.g., use in an agricultural application, e.g., wee control film
- Post-Consumer Products – plastic bottles are usually polyester (PET) and are not typically used for engineered geomembranes, but could be used for other geosynthetics
- IGS website has information on sustainability: https://www.geosyntheticssociety.org/sustainability/; https://www.geosyntheticssociety.org/wp-content/uploads/2022/10/Fontana-Bologna-2022.pdf
‍

Applications
‍- Short-term applications due to changes in applications
- Not permanent applications
- Applications driving amount of reworked material
- Agricultural applications
- Old billboards used for tarps
- Non-critical applications
- If the reprocessed material meets GM-17 for LLDPE, it may be suitable
- Water v. potable water – not viable for potable water unless it meets NSF specifications
- PFAS applications=? Probably not viable and must prove chemical resistance with new formulation
- Use for core of multi-layer materials

 Amount of Rework Material
‍- Usually 5 to 10% for new geomembranes
- Can be as high as 50% for repurposed applications, i.e., less critical applications

Suggestions for Specification of CQA and Welding Certifications

- Add certifications to FGI Material Specifications
- FGI Members add to your specifications
- For example, make it similar to electrical certifications for construction
- How do we get regulators involved in the certification process?
- OEPA Landfill Rules – IAGI CWT was considered but couldn’t require IAGI over another provider – so specified a minimum level of experience = 1 M sq ft of liner experience for Junior Seamer &over 5 M sq ft for Master Seamer
- Fracking industry has limited requirements and many problems
- Most military and government specs require a minimum square footage of liner experience
- In PA they require training by DemTech or the installer = orientation classes not a certification class and exam
- Iowa DNR – including another entity's rule into Iowa’s Rule is difficult because it could change = hard to stay current so leave it to consultants to specify the certification
- Certification could result in liability
- FGI Create Drop-In Specifications for Consultants to download from FGI website and include list appropriate lab and field ASTM Test Methods
- Detail specification is at engineering level not regulatory level so target engineering firms
- How do we contact all state regulators? Instead contact ASTWMO, SWANA, AWWA, etc. and inquire about including specification
- CQA Course and Certification is do able but inspection is more difficult & probably requires regulatory involvement – certification does increase cost but inspection increases cost much more, especially for full-time inspection – have regulators consider requiring or recommending certification and/or inspection, especially full-time inspection
- OEPA – has required 3^rdparty CQA for a long time – right now CQA firm is hired by the landfill; future may have CQA paid by landfill but CQA firm reports to OEPA directly; another option is having CQA firm report to the contractor not the landfill owner
- Another option is landfill provides a pool of 3^rd party CQA firms and OEPA selects the firm or firm is randomly selected so same company cannot keep doing the CQA for the same landfill
- It may need a national requirement – USEPA – White Paper on Subtitle D updating and clarifications recommends adding CQA requirement to Subtitle D; Ed Silva will contact GMA about the status of presenting the White Paper to the USEPA

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

‍Hydropower Reservoir Applications

- Industry want a Geomembrane (GM) that will last 50 years, a 75 to 100 year life-cycle, and/or aa 75 year warranty
- Mt. Elbert Reservoir – GM is covered with 18 to 24” of soil and rockfill on the upstream slop
- Only GM lined hydropower reservoir in public us in the U.S.A.
- Tesla Reservoir– Original Design - exposed GM - 1995 & 2017
- Concern with a soil or rock cover is the soil or rock could get into turbines so industry is interested in exposed GM applications
- A bituminous geomembrane (BGM) might be suitable
- Taum Sauk Pumped Storage Hydropower (PSH) Facility leaking upper reservoir was repaired with exposed GM – subsequently embankment was overtopped because no spillway was present; should have initially lined the upper reservoir with a geomembrane
- Luddington PSH –leaking upper reservoir was repaired with exposed GM
- Asphalt concrete(AC) liners appear to be currently preferred to a GM – advantages are waterproof barrier & durable wear surface – a hydraulic grade of asphalt is used but overtime cracks develop & have to be sealed – in addition, subjected to seismic cracking
- FGI should research cost of AC liner system per square foot – probably cost is $15 to $20/ft^2
‍- Could install four or five GMs for the cost of an AC liner
- A better liner system in seismic areas could be a dual system of GM over lain by AC liner due to cracking
- Concrete facing is too expensive for a reservoir so not considered
- In non-seismic areas could use GM as a secondary liner under the AC liner to provide containment after AC starts cracking due to exposure
- GM under an asphalt liner system – hot asphalt (170⁰F) placed on top of fPP-R has been effective and can be installed with no wrinkles to facilitate AC liner placement
- Flexible geomembranes make more sense because few wrinkles and good elongation and ductility
- If there is a short-term application, e.g., line a spillway or a storage tank, a flexible geomembrane makes more sense
- AC Pavement design – asphalt pavements have exposure issues with time, e.g., reflective and shrinkage cracking; flexible geomembranes would be a good secondary barrier or use GM exposed and forego AC liner

Conveyance Structures

- Emergency spillways can be protected with a geotextile and then covered with rockfill

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

 Geomembrane Thickness

-      Thin geomembranes are usually (< 30 mil thickness) for temporary and non-critical containment applications
-      Examples of thin geomembranes = Woven Coated Polyethylene (WCPE) & linear low density polyethylene (LLDPE)
-      Thin geomembranes can be welded in a factory but difficulties in field
-      Thin geomembranes are preferred to create large factory fabricated factory panels
-      IAGI CWT Program could be expanded to include thin geomembranes

Temporary Repair/Welding Techniques

-      Solid Wedge weld– 12 to 20 mil is possible for thin geomembranes
-      Hot air wedge weld – 12 to 20 mil is possible for thin geomembranes
-      Hot air gun –Patches – 12 to 20 mil is possible for thin geomembranes
-      Tapes –available but not preferred unless for cap strip over a patch
-      Available tapes– Tapecoat/Chase Adhesives is a tape and primer supplier
-      Tape may be stable for a temporary small patch until crew arrives to install proper patch
-      Tape is available single-sided and double-sided tape
-      Tape may be useful for underwater applications
-      Can use tape to help seal penetrations
-      Tape is not preferred for long-term applications
-      No good adhesive for polyethylene based materials
-      Do you require trial welds for patches? Not for heat guns
-      Need some documentation/guideline to improve quality of field welding thin geomembranes - ASTM D8468-23 Practice for Data Recording Procedure may be a useful reference

Repair Testing

-      Air lance testing is preferred – ASTM D4437
-      Vacuum box testing preferred but limited with WCPE geomembranes b/c air can pass through patch with a thin geomembrane
-      Electrical leak surveys can be used with thin geomembranes

CQA of Thin Geomembranes

-      Can field test seams in shear
-      Peel testing of seams is limited
-      Same seam test procedures as thick geomembranes including documentation
-      No warranty on patching old thin geomembranes – case by case determination – only warranty repair was made “with good workmanship

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

Methane Detection Applications

-            Landfills
-            Biodigesters
-            Oil and gasproduction
-            Common in Europe

Methane Detection

-            Unmanned Aerial Vehicles (UAVs) – Attend May, 2024 FGI Webinar by Art Mohr
-            Hand-held gas meter – FLIR GF320
-            Neighbors are best detectors – of other gases b/c methane is odorless but usually accompanies landfill odors
-            Larger issue in eastern portion of USA than western portion, e.g., Colorado
-            Newer drones detecting other contaminants besides Methane
-            Satellites also being used to detect methane–
-            Safety issues –H₂S gas
-            Infrared gas meters in Europe – FLIRGF320 in Europe - https://www.flir.com/discover/instruments/gas-detection/biogas-facilities/ or Gas Detection Cameras | FLIR Industrial | Teledyne FLIR 

Methane Containment

-            Manufacturers investigating geomembrane durability subjected to Methane and other factors – see GRI GM-35 material specification
-            Use temporary geomembrane covers to control methane release – significant leakage around gas wells, i.e., final cover penetrations
-            Also use temporary geomembrane covers for leachate control as well as methane capture
-            Methane capture is proving lucrative, so temporary covers are gaining interest
-            Should FGI develop test method and criterion for methane/odor transmission through flexible geomembranes? Decided that methane geomembrane transmission is small compared to current leakage points so focus on leakage points - https://www.fabricatedgeomembrane.com/articles/methane-gas-migration-through-geomembranes
‍-            EVOH based geomembrane appear more effective than HDPE based geomembranes in containing landfill odors and methane
-            European regulations on methane control are available at https://energy.ec.europa.eu/topics/oil-gas-and-coal/methane-emissions_en

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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