COPA - PCBs and Superfund in Bloomington, Indiana

Lemon Lane Final Report
June, 2001

8.0 PLACEMENT OF GEOMEMBRANE AND GEONET

8.1 Inspection and Quality Control of Geosynthetics

Geosynthetics used in the construction of the RCRA Subtitle C cap consisted of a 40 mil thick textured very flexible polyethylene (VFPE) geomembrane liner, and a Geocomposite drainage medium with a geonet component composed of virgin high- density polyethlene resin (HDPE) wire mesh with non-woven geotextile fabric bonded to both sides. The VFPE is a broad classification of materials, which includes linear low density polyethylene (LLDPE), low density linear polyethylene (LDLPE), and very low density polyethylene (VLDPE). Each roll of LLDPE material delivered to the site was identified with a tag that included the lot number, roll number and date of manufacture.

Each of these cap components was subject to strict strength and performance specifications and was inspected upon delivery and during placement. Production QC tests were performed by Agru / America, Inc., the manufacturer, and were submitted to WAS at the time of delivery.

The manufacturing QC tests performed on the geomembrane material include:

Tensile Properties
Core Thickness
Puncture Resistance
Tear Resistance
Dimensional Stability
Carbon Black Dispersion
Carbon Black Content
Coefficient of Friction
Low Temperature Brittleness
Density

The manufacturing QC tests performed on the Geocomposite material include:

Flow Capacity
Transmissivity (Geocomposite)
Permittivity (Geotextle)
Mechanical Properties
Grab Tensile Strength (Geotextile)
Apparent Opening (Geotextile)
Peak Tensile Strength (Geonet)
Play Adhesion (Geocomposite)
Coefficient of Friction
Material Properties
Polyethylene Density (Geonet)
Carbon Black Content (Geonet)
Dimensions
Thickness (Geonet)
Mass/Area (Geotextile)

Each submittal was reviewed and approved by Golder Associates. The quality control review of these submissions is discussed in detail in the Golder Certification Report contained in Appendix F. In addition, Viacom representatives obtained samples periodically from the material delivered to the site. Golder conducted quality control testing on these samples to insure that the material performance matched the QC test results provided by the manufacturer. General inspection of these materials at the job site prior to deployment involved the matching of the manufacturer's Lot and Roll numbers that were tested, with those that were actually delivered to the site. These records are also included in the Golder report.

8.2 Geomembrane Panel Layout and Survey Documentation

Following the completion of a "Geomembrane Installer's Certification of Subsurface Acceptability" form for each area (Appendix lil of report in Appendix F), individual geomembrane panels were deployed over the slopes, cut to length and then fusion welded together over the full length of adjoining panel sections. Installation of the geomembrane started on the northeast and proceeded across the north slope. Once the north slope was completed the installation operation moved to the southeast and proceeded across the south slope. The geomembrane liner was deployed in panels approximately 23 ft. wide and 492 ft. in length. Dual-sided textured VFPE geomembrane was used over the landfill and extended into and through the perimeter channels. The textured geomebrane was also extended over the southwest slope, across the bottom of the retention pond and up the west bank of the retention pond. Smooth surface VFPE geomembrane was not used. The textured geomembrane was secured into an anchor trench that was constructed on the outside perimeter of the channel and retention pond. Placement of the GCL and the geomembrane over the surface of the consolidated materials was completed on November 11, 2000. The general configuration and arrangement of the panels was established in the field based on the final as-built shape of the landfill. An as-built panel layout drawing for the geomembrane covering the landfill was prepared by Envirocon and is included as Figure 10.

The as-built drawing shows the general configuration of individual panels over the top of the GCL, as well as survey data locating several panel intersection points. The panel layout survey data were developed by SNA and provided to Envirocon. This drawing also documents the individual panel and roll numbers, the locations of butt seams (panel end to panel end; square on relatively flat areas and diagonal on the slopes), the locations of CQA seam tests and repairs, and the extent of liner deployment beyond the LOC through the perimeter channels. In all cases, the geomembrane was extended into an anchor trench that was excavated around the perimeter channel about two feet beyond the outside edge of the channel. A trench was also excavated on the west and south edges of the retention pond. The purpose of the trench was to terminate the edge of the geomembrane, thus securing the RCRA cap. Other details regarding the geomembrane deployment are contained in the Golder CQA Certification Report for the cap in Appendix F.

8.3 Penetration Boots and Geomembrane Repairs

Penetrations through the geomembrane were made at each of the 6 new piezometers shown on Figure 8. Four piezometers were located within the LOC and two were just outside the limits between the consolidation and the perimeter channel on the west side of the site. All six piezometers penetrated the geomembrane. At each location, a penetration boot was fabricated in the field and installed around the base of the piezometer riser pipe. The boot was extrusion welded to the geomembrane panels at the base of the riser. A neoprene gasket material was placed between the boot and the riser pipe and two stainless steel hose clamps were used to clamp the boot to the pipe. This approach was necessary since it was not possible to extrusion-weld the VFPE boot directly to the PVC pipe due to incompatibility of these materials. Caulking was applied to the seam between the geomembrane and the PVC pipe. R

epairs were made to the geomembrane anytime the integrity of the membrane was in question or when testing of a seam was required. All repairs involved a patch being made from the same geomebrane material and having the patch extrusion welded to the membrane. Repair information and CQA of repairs is discussed in the Colder CQA Certification Report in Appendix F.

8.4 Geonet Drainage System

The geonet is a general drainage component of the cap. The geonet drainage composite system consists of a HDPE drainage grid sandwiched between two layers of non-woven geotextile fabric. The geonet drainage composite was placed over the entire cap and extended into the riprap contained in the drainage features around the perimeter of the LOC. The geonet composite was deployed in panels, much like the geomembrane, except that individual panels were overlapped 1 foot and spliced together using plastic zip-ties spaced 5 feet apart. The function of the geonet is to collect infiltration water that percolates through the vegetative support zone soils. The water collected in the drainage grid flows through the grid into the perimeter channel. The drainage net extends into the riprap that lines the channels and the bench between the retention pond and the LOC on the west.