Questions & answers

MWAN's Standards & Technical Guidelines for the Design, Construction and Operation of Landfills (TG-WM-05 (2), 1 November 2024) set a minimum geomembrane for each landfill category: • Category 1 (hazardous waste): at least 2.5 mm HDPE, or a double liner with leak detection (2.0 mm HDPE, a geocomposite drainage layer and a second 2.0 mm HDPE). • Category 2 (non-hazardous waste): at least 1.5 mm HDPE. • Category 3 (inert waste): no geomembrane required, depending on the liner system used. The final thickness follows the approved design and can be increased based on the project's risk assessment.

Not by default. MWAN's landfill guideline notes that a leak location survey after cover placement is not mandatory, but the facility owner or the authorities may require one on high-risk sites. Where a project specifies a survey, Optimum Techniques for Contracting coordinates it with specialist survey providers.

A Construction Quality Assurance (CQA) plan sets out how the liner is supplied, installed, tested and documented. Under MWAN's guidelines, the geomembrane part covers material specifications; delivery, storage and handling; conformance testing; panel deployment; trial and field seam welding; non-destructive and destructive testing; repairs; and protection and backfilling. An independent third-party engineer supervises CQA throughout construction. A final CQA certification report records all test results, including failed tests with their corrective actions and retests, along with test location drawings, as-built drawings, daily site records and non-conformance records.

For most exposed evaporation ponds, 1.5 mm HDPE is the practical minimum. 2.0 mm is common where the pond holds hazardous brine, where desludging equipment will work on the liner, or where a long design life is required. Higher-risk applications often use a double liner: two HDPE layers with a leak detection layer between them, draining to a monitoring sump. In Saudi heat, thickness is only part of the answer. The material should meet GRI-GM13 for carbon black and antioxidant content, and the installation must allow for thermal movement, because exposed black HDPE can exceed 70 °C in summer.

During installation, seams are tested non-destructively and destructively. Non-destructive methods include vacuum box testing of extrusion welds and details, spark testing, and air-pressure testing of double-track fusion seams; ASTM D4437 describes non-destructive seam testing practice. Destructive testing means cutting samples and testing them in peel and shear with a tensiometer. After installation, an electrical leak location survey can scan the whole liner and pinpoint holes that seam testing cannot find, such as punctures from tools or stones. Optimum Techniques for Contracting tests with vacuum box and spark testing and runs peel and shear tests with an on-site tensiometer. Where a project specifies a leak location survey, we coordinate it with specialist providers.

These are the main cost drivers: • liner thickness, and whether it is smooth or textured • total area, since mobilisation is spread over more square metres on large jobs • geometry: slopes, corners, pipe penetrations and structures all add welding and detailing time • the condition of the subgrade and how much preparation it needs • extra layers, such as protection geotextile or a second liner with leak detection • QA/QC scope, including third-party testing and any leak location survey • site location, access and working hours, including summer restrictions. To give a firm price, a contractor needs the approximate area, the liner specification, drawings if available, and the site location.

Use textured HDPE where friction matters: on side slopes that will carry soil cover, drainage material or waste, and at interfaces with geotextiles where sliding could occur. Smooth HDPE is standard for pond floors, exposed slopes without cover and most water applications. Textured liner costs more and is harder to clean, so it is usually specified only where the stability analysis requires it. A common result is textured liner on the slopes and smooth liner on the floor.

GRI-GM13 is the Geosynthetic Institute's standard specification for smooth and textured HDPE geomembranes. It sets minimum values and test frequencies for properties such as thickness, density, tensile strength, tear and puncture resistance, carbon black content and dispersion, and oxidative induction time (antioxidant content). Referencing GM13, and asking for the manufacturer's certificates, is the simplest way to get a liner that will last in exposed Saudi conditions rather than a cheaper sheet that only looks the same.

At a minimum, the installer should hand over: • the approved method statement and inspection & test plan • manufacturer certificates for the material • panel layout and deployment records • trial weld and seam records • non-destructive and destructive test results, including any failed tests with their corrective actions and retests • a repair log • test-location records and as-built data. For MWAN-regulated landfills, these records feed the project's CQA certification report.

A covered HDPE liner, under soil, waste or water, is protected from UV and heat and can last many decades. An exposed liner ages faster. Its service life depends mainly on UV intensity, temperature and the antioxidant package in the material. In the Kingdom's climate, specify material that meets GRI-GM13 and use 1.5 mm or thicker for exposed industrial ponds. Inspect exposed liners periodically so that small damage is repaired before it spreads.

Yes. We repair HDPE liners with extrusion-welded patches, test every repair and document it. Aged, exposed HDPE needs its surface prepared before welding, and a trial weld on the old material shows whether a reliable repair is possible. We guarantee our workmanship and support our clients after handover.

Yes. We take on projects of all sizes, including farm irrigation ponds and water ponds. Small projects get the same trial welds, testing and records as large ones.

Yes. We work both as a direct contractor and as a specialist lining subcontractor to main contractors and EPC companies. For civil scope, such as earthworks, subgrade and cement-stabilised sand cover, we work with a partner civil contractor.

Heat affects both the crew and the liner. Outdoor work in direct sun is prohibited from 12:00 to 15:00 between 15 June and 15 September. Hot sheet temperatures also narrow the welding window and increase wrinkles. Good practice is to plan deployment and welding around the cooler hours, deploy only what can be welded and ballasted the same day, and place cover when the liner has contracted in the early morning. Summer projects are entirely feasible; they just need a realistic programme.

We are based in Dammam, in the Eastern Province, and serve all regions of Saudi Arabia.