Ronald Kerry Rowe

Queen's University | QueensU · Department of Civil Engineering

The stress crack resistance (SCR) of different multilayered textured geomembranes (GMBs) immersed in synthetic municipal solid waste leachate at 55 and 85 o C for 50 months is assessed using their smooth edge or smooth equivalent GMBs made from the same formulation of the textured GMBs. The difference between the actual thickness of the smooth edge...

This study offers an analytical solution for radial consolidation that captures the bio-geochemical clogging effect in acid sulfate soils. Field sites and personal communication with industry practitioners have provided evidence of piezometers exhibiting retarded pore pressure readings that do not follow conventional soil consolidation and seepage...

The durability of five 1.5-mm thick geomembranes (GMBs) is investigated in pH 0.5 and 13.5 synthetic mining solutions using immersion tests. Two high density polyethylene (HDPE), two linear low density polyethylene (LLDPE), and one blended polyethylene (BPO) GMBs are investigated at 85 • C for incubation durations of 4.5-6.5 years. It is shown that...

The longevity of two white multilayered textured geomembranes, manufactured with a smooth edge for welding, is examined when immersed in synthetic municipal solid waste leachate at five temperatures (40, 55, 65, 75, and 85°C) for 50 months. The textured and smooth parts of the geomembranes had similar initial chemical and physical properties, but t...

The long-term performance of a geosynthetic clay liner (GCL) above a drainage layer and a geocomposite drain (GCD) are investigated. Full-scale tests are used to: (i) assess the integrity of GCL and GCD in a double composite liner below a defect in the primary geomembrane with ageing, and (ii) establish the head at which there was internal erosion...

Leakage and erosion of a soluble subgrade overlain by a geomembrane with a 70-mm-long slit defect is examined. The subgrade (gypsum) solubility and its rate of dissolution from a solid state in contact with various solutions are investigated. In the absence of flow, the rate of dissolution is negligible. However, when there is flow there is dissolu...

Low-permeability liners are required at the base of municipal solid waste (MSW) landfills to minimize leachate leakage and contaminant migration into groundwater. This paper uses a two-dimensional coupled groundwater flow and contaminant transport model to examine the performance of three types of low-permeability liners specified by the current Ch...

To safely contain Per-and Polyfluoroalkyl substances (PFAS) in municipal solid waste landfills and contaminated soil monofills, it is necessary to understand how these substances interact with components of engineered systems designed to contain them. This paper examines the interaction between one of the most critical components of the system: a h...

Tailings dams and heap leach pads projects are among the mining applications that extensively use polyethylene geomembranes to prevent the migration of fluids to the surrounding environments. The pH of acidic heap leaching solutions are typically at or below 2.0, while tailings pore waters from pre-filtered or unsaturated tailings may range between...

In landfill covers, geomembranes are mainly used to control the infiltration of moisture from rainfall and snow melt. Unlike the base liners, cover geomembranes are on a slope and are more vulnerable to differential settlement due to the non-uniform degradation and thawing of waste. Also, in the long term, some holes in cover geomembranes are inevi...

The difference in seam squeeze-out antioxidant loss (in terms of standard oxidative induction time, Std-OIT loss) and thickness reduction are evaluated for three different 1.5 mm-thick high density polyethylene (HDPE) geomembranes (GMBs) seamed using a variety of welding parameters and two different wedge welders. Partial squeeze-out antioxidant lo...

An experimental study of the effect of closed system and a limited study of open system freeze-thaw cycles on the interface transmissivity at applied stresses between 10 and 150 kPa is described. The effect of closed system freeze-thaw is most apparent after 100 freeze-thaw cycles and permeation at a stress ≤25 kPa. The effect of permeating fluid c...

The stress crack resistance (SCR) and standard oxidative induction time (Std-OIT) reduction of high density polyethylene (HDPE) geomembrane (GMB) fusion seams is examined for a 12-year old 1.5 mm HDPE GMB when welded using nine welding parameter combinations. The GMB experienced a decrease in Std-OIT from 135 to 87 min between manufacturing and wel...

The degradation in physical and mechanical properties of a 1.5 mm-thick HDPE geomembrane immersed in seven different low pH and three high pH simulated mining solutions is examined at temperatures between 95 and 40oC for 3 years. The solutions with pH between 0.5 and 13.5 encompass solutions found in copper, nickel, uranium, gold, and silver heap l...

The state-of-the-art for barriers systems control of pollution migration and hydraulic structures including liner systems for landfills, mine waste, and dams/lagoons are discussed along with some comments on current significant environmental issues.

Experiments are conducted to quantify short-term tensile strains induced in a 1.5-mm-thick high-density polyethylene geomembrane overlain by tailings. Four subgrades, a poorly graded angular to sub-angular gravel (GP), a well-graded angular to sub-angular gravel (GW), a poorly subrounded graded sand (SP), and silty sand (SM), and two nonwoven geote...

The state-of-the-art for barriers systems control of pollution migration and hydraulic structures including liner systems for landfills, mine waste, and dams/lagoons are discussed along with some comments on current significant environmental issues.

Waste disposal facilities commonly have a composite liner (e.g., a geomembrane, GMB, over a geosynthetic clay liner, GCL) in both the cover and bottom liner. The performance of a composite liner primarily depends on the size, number, and location of holes in the geomembrane together with the hydraulic conductivity, k, of the GCL, and the interface...

Time and method dependencies, lack of sufficient capillary connections, and wetting-drying hysteresis may cause inaccurate results from filter paper tests (FPTs) when used for suction measurements of geosynthetic clay liners (GCLs). These limitations of the filter paper method for suction measurements of GCLs were investigated using initially dry c...

Experimental data is presented for leakage through slits, square, and rectangular geomembrane defects overlain by silty sand tailings and underlain by a well-graded gravel. The rectangular GMB defects have a range of widths, B, lengths, L, and aspect ratios (L/B), and ratios of defect length to thickness of tailings above the geomembrane (L/T). A b...

Two GCLs with sodium bentonite and three GCLs with polymer amended bentonite were subjected to wet-dry cycles selected to simulate the conditions to which a GCL on an 18 o slope might be subjected: for a GCL below an exposed geomembrane wrinkle with a hole. The wetting involved water flowing over the GCL for 8 hours each cycle. Three drying cycles...

The effect on GCL hydration and dehydration, when subject to thermal cycles, of (1) GCL bentonite granularity (powdered vs. granular), (2) GCL geotextile type (scrim-reinforced nonwoven vs. woven), (3) subgrade macrostructure due to fines aggregation, and (4) subgrade density and fines content is examined. Results of 17 hydration tests were assesse...

The stress crack resistance (SCR) of high density polyethylene (HDPE) geomembrane (GMB) fusion seams is examined for two 1.5mm HDPE GMBs and a range of welding parameters. Results are reported for both unnotched and notched seams as well as their corresponding sheet material. Unnotched seam SCR specimens are shown to preferentially initiate craze f...

This study demonstrates the change in porosity of permeable reactive barrier (PRB) material when it reacts with acidic flow. The laboratory column test data obtained over nine months proves that the porosity of a granular limestone assembly decreases significantly due to bio-geochemical clogging caused by a continuous flow of acidic groundwater. Th...

The self-healing of five geosynthetic clay liners (GCLs) with laboratory simulated down-slope erosion defects (quasi-circular holes and linear slits where there is little or no bentonite) upon hydration from Godfrey silty sand subgrade with w fdn = 16% under an overburden stress σ v = 20 and 100 kPa is examined. While there was an up to 9.6 mm redu...

Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown t...

ABSTRACT Over a period of 40 years, fuels spills and leaks have occurred at Canadian sub-Arctic and Arctic Distant Early Warning Line (DEW Line) sites. The Canadian Department of National Defence has initiated cleanup program of these sites estimated to cost $320 million (Cdn). Access to these sites is often limited and the environmental conditions...

The impact of time-dependent unsaturated behaviour of virgin and the impact of cation self-diffusion on the time-dependent unsaturated behaviour of exhumed Geosynthetic Clay Liner (GCL) specimens were investigated using a chilled mirror hygrometer. Total suction values (after 7 weeks water homogenization) are reported for ten virgin (six different...

A laboratory investigation was conducted on two different conventional GCLs (one with fine granular and another one with powdered bentonite) to explore the effect of prehydration and permeant fluid; GCL desiccation on the interface transmissivity, θ, between the interfaces of a 1.5 mm-thick high-density polyethylene (HDPE) geomembrane (GMB) and a G...

Experiments are conducted to study leakage and piping through circular geomembrane holes from the overlying silty sand tailings. Three subgrades, a poorly graded gravel, a well-graded gravel, and a poorly graded sand are studied. Test results show that leakage through the geomembrane hole is not proportional to the surface area of the hole. A 5-fol...

The design of saturated tailings impoundments often relies on geomembrane liners at the base and upstream face of the storage facility to prevent the movement of tailings-derived water into the adjacent groundwater flow system. The geomembrane must be chemically compatible with the tailings pore water to ensure its long-term performance in protecti...

The observation of failure surfaces within column supported embankments is critical to understanding how the embankment stresses are transferred towards the column heads. In this study, finite element simulations utilising a strain softening constitutive model, non-local regularisation and the Arbitrary Lagrangian-Eulerian formulation are used to e...

Waste disposal facilities commonly have a composite liner (e.g., a geomembrane, GMB, over a geosynthetic clay liner, GCL) in both the cover and bottom liner. The performance of a composite liner primarily depends on the size, number, and location of holes in the geomembrane together with the hydraulic conductivity, k, of the GCL, and the interface...

The contaminant transport of perfluorooctane sulfonate (PFOS) through the base of a municipal solid waste landfill lined by a single composite liner comprised of a geomembrane over a geosynthetic clay liner (GCL) and a 3.75 m-thick attenuation layer underlain by an aquifer is examined. Both pure diffusive transport and advective transport through h...

Performance indicators of geosynthetic clay liners (GCLs) exposed to the Antarctic environment were assessed using field and laboratory methods. Barrier properties of the GCLs were not impacted by the field conditions and exhumed hydraulic conductivities with respect to tap water ranged from 0.4x10-11 m/s to 12x10-11 m/s, compared to 5x10-11 m/s (v...

Experiments are conducted to quantify leakage through holes in a geomembrane (GMB) overlain by tailings with 30% fines and underlain by a well-graded gravel. Analytical and empirical equations for predicting leakage through a circular hole are used to analyze the data. Test results show that changing the hole shape from circular to noncircular incr...

Experiments are conducted to quantify leakage through a circular geomembrane (GMB) hole using two types of underliner not meeting modern filter criteria. Test results show that a 1.9 and 5.0-fold increase in hole diameter cause a 1.8 and 6.2-fold increase in leakage, respectively; while a 2-fold increase in GMB thickness results in an approximate 1...

CSCE's Engineering Mechanics and Materials (EMM) division is organizing a panel session titled: Transitioning from Graduate Studies to Securing Faculty Positions, to be held on Wed, May 26, 12-1 pm (EST), as a part of the CSCE annual conference (https://csce2021.ca/). All CSCE graduate student members are welcome to join.

Leakage through a 10-mm-diameter hole in a geomembrane beneath fine-grained tailings is examined for a range of pore pressures and effective stresses. Leakage was measured in an experiment with coupled physical and hydraulic conditions to simulate the effective stresses and flow conditions near the hole. The leakage rate was at little as 0.16 L/day...

The self-healing of a GCL with a circular hole is examined in experiments where the GCL, overlain by geomembrane, is hydrated from a silica sand subgrade (SSS) having three different pore water chemistries. Factors considered included: hole size, subgrade initial moisture content wfdn, GCL mass per unit area, and overburden stress (20–100 kPa). GCL...

The performance of five different GCLs (two GCLs with standard sodium bentonite and three GCLs with polymer enhanced bentonite) subjected to three different climatic modes of wet-dry cycles simulating conditions to which a GCL might expose in cover systems over a prolonged time is reported. The wetting cycles lasted for 8 h, while the drying cycles...

Swelling characteristics of compacted bentonite when hydrated with a hypersaline pore fluid (332 g/L total dissolved solids; 6.6 mol/L ionic strength) are reported. The pore fluid mimics the multiple constituents and their concentrations found for the Cobourg limestone of the Michigan Basin and is dominated by sodium (25% mole fraction) with some p...

This lecture examines the progress made in the last few decades concerning the use of geosynthetics for aiding in the construction on soft soils. Consideration is given to different soft soils ranging from peat to rate-sensitive soft clay and silt. Both relatively elastic and rate-sensitive reinforcements are examined. Consideration is given to bas...

The influence of co-disposal of municipal solid waste (MSW) and incinerator ash used as daily cover on the clogging of leachate collection systems (LCSs) from landfills is examined. The ‘BioClog’ model is used to simulate the fate and transport of the nine leachate constituents most responsible for the clogging the LCSs as they move through the por...

A series of laboratory tests were conducted to investigate the interface transmissivity, θ between a 1.5 mm thick high-density polyethylene geomembrane (GMB) and a multicomponent geosynthetic clay liner (MC_GCL) when permeated with a simulated municipal solid waste landfill leachate under a range of applied stresses (10-150 kPa). The effect of thre...

Diffusion of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) through 0.1 mm and 0.75 mm LLDPE and 0.1 mm and 0.75 mm LLDPE coextruded with ethyl vinyl alcohol (denoted as CoEx) at room temperature (23 °C), 35 °C, and 50 °C is examined. These tests had negligible source depletion throughout the monitoring period, indicating limited co...

This paper examines the hydration/dehydration behaviour of geosynthetic clay liner (GCL) under polar conditions for four simulated conditions experienced at Australia's Casey Station in Antarctica: (a) hydration during summer, (b) dehydration during a winter-summer cycle, (c) hydration through a fine Antarctic soil, and (d) hydration through a coar...

The interface transmissivity (θ) of two multicomponent geosynthetic clay liners (GCLs) is investigated upon hydration and permeation with a highly saline solution (TDS ≈ 260,000 mg/l; Na⁺ ~ 95,000 mg/l; K⁺~12,000 mg/l) at two stress levels (10 kPa and 150 kPa). One GCL had a smooth 0.2 mm-thick coating whereas the second GCL had a textured 1 mm-thi...

The longevity of textured geomembranes (GMB) widely used as base and slope liners is rarely studied. The variability of the thickness and defects on the surface of co-extruded textured GMBs result in non-uniform mechanical properties across the GMB roll. Therefore, the effect of texturing on the stress crack resistance (SCR) of unaged and aged high...

The paper examines the effects of settlement-induced downdrag on geosynthetic liner systems for a waste containment facility with steep side slopes for different design scenarios, and conducts the stability analysis of the waste mass during waste filling operations. Without the presence of a reinforcing layer above a geomembrane (GMB) liner, the li...

Geosynthetic reinforced column supported embankments predominantly utilise two mechanisms to transfer embankment loads towards column heads, soil arching and membrane actions. When undertaking the design of column supported embankments, it is common practice to perform a two-step design, whereby the arching actions are estimated independently of th...

Recently, there has been increased interest in the use of geosynthetic clay liners (GCL) in composite liners in harsh environments like the Arctic and Antarctic regions. The primary role of a GCL in the composite liner is to minimize the advective flow of contaminants if there are any holes in the geomembrane (GMB). The two parameters controlling t...

A modified osmotic suction control technique for monitoring apparent transient weight changes was successfully adapted to the wetting and drying paths of geosynthetic clay liners (GCLs). Reasonable control was possible, enabling suction equilibrium to be achieved without disruption to the test. The results provide unique insight into the time-depen...

Horizontal spacing of horizontal extraction gas wells can be designed to achieve a 90% pumping rate of the total generated landfill gas (LFG) from given waste properties (viz: gas permeability, landfill gas generation and non-homogeneity with depth), cover characteristics and vacuum pressure. However, cover characteristics and vacuum pressure are a...

The desiccation and subsequent hydraulic conductivity of both a standard (GCL_A) and polymer-enhanced (GCL_B) Na-bentonite GCL hydrated from a well-graded sandy subsoil under 20 kPa, then subjected to a thermal gradient, and finally rehydrated and permeated with distilled water or 0.325 mol/L Na⁺ synthetic brine are reported. With moderate temperat...

The long-term performance of geomembranes with twelve different resin/antioxidant master-batch combinations, including eight HDPE, three linear low density polyethylene (LLDPE), and one blended polyolefin (BPO) base resins, is investigated. Results are reported for immersion tests in chlorinated water (0.5 ppm) for 35 months at 85oC. The degradatio...

Aqueous diffusion of trichloroethylene (TCE) and tetrachloroethylene (PCE) is examined for high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polyurethane/urea, and two polyethylene (PE) geomembranes coextruded with ethylene vinyl alcohol (EVOH). Additionally, the diffusion of benzene, toluene, ethylbenzene, and xylenes thro...

The self-healing of a GCL with artificial defects (circular holes and rectangular slits, both with and without the carrier geotextile preserved below the holes) upon hydration on a Godfrey silty sand (GSS) subgrade with wfdn = 5, 10 and 16% under 2–100 kPa is examined. Circular holes with the carrier geotextile missing below holes with diameters up...

Desiccation of geosynthetic clay liners (GCLs) in composite lining systems is investigated experimentally. Field conditions similar to those encountered in brine ponds (high surface temperature and low overburden pressure of 20 kPa) are simulated in two soil columns. The GCL is first allowed to hydrate from a sandy subsoil under isothermal conditio...

The behaviour of geosynthetic clay liners (GCLs) as part of a physical-environmental system is examined. Consideration is given to: (a) both the physical and hydraulic interactions with the materials, and the chemical interactions with the fluids, above and below the liner, (b) time-dependent changes in the materials, (c) heat generated from the ma...

Column experiments that investigate the use of calcitic limestone as a potential material for permeable reactive barriers (PRBs), as well as its clogging behavior, are conducted under conditions that involve continuous acidic flow containing Al, Fe, and acidophilic bacteria. Results show that nonhomogenous biogeochemical clogging occurred toward th...

Column experiments that investigate the use of calcitic limestone as a potential material for permeable reactive barriers (PRBs), as well as its clogging behavior, are conducted under conditions that involve continuous acidic flow containing Al, Fe, and acidophilic bacteria. Results show that nonhomogenous biogeochemical clogging occurred toward th...

A new approach is presented to obtain the water retention curve of a geosynthetic clay liner (GCL) on the wetting path (i.e. when it is hydrating). This approach is based on a back-analysis process using data from a hydration test. The back-analysis method was validated by comparing it to conventional experimental measurement techniques such as vap...

This paper presents empirical solutions for engineers to assess advective gas leakage through a GMB/GCL composite liner. The paper first introduces analytical solutions for gas leakage from a circular defect in GMB and derives an analytical solution from a long rectangle defect. The analytical solutions are rigorous but complicated, requiring a num...

An approach for selecting a geomembrane (GMB) for a long design-life is described and illustrated for five 2 mm-thick textured GMBs when immersed in a simulated municipal solid waste leachate (L3) and two low-level waste leachates (L7 and L9) for 9-16 months at a range of temperatures. Although made from the same nominal resin, the substantial diff...

The decrease in stress crack resistance (SCR) of geomembranes (GMBs) due to physical ageing is examined. It is shown that the SCR of a 1.5 mm high density polyethylene (HDPE) GMB immersed in municipal solid waste (MSW) leachate, deionized (DI) water, and air experienced a decrease to an equilibrium value, denoted herein as SCRm, in a few months and...

The impact of multi-component hypersaline groundwater is simulated by synthetic hypersaline water with 330 g/L total dissolved solids and an osmotic suction of 41 MPa. The effects of this hypersaline water on the retention behavior of compacted MX80 and MX80/ poorly graded sand mixtures as well as MX80 amounts and distributions of soluble and excha...

The self-healing of fully penetrating artificial defects (circular holes and rectangular slits) in geosynthetic clay liners (GCLs) on full hydration in deionized water and 10 mM calcium chloride (CaCl 2 ) solution under 2 kPa overburden stress are compared. Circular holes with diameters up to 41 mm self-healed in deionized water but with an indenta...

Considering exponential decreases in gas permeability and gas generation of waste with depth, a two-dimensional analytical model is developed to describe the landfill gas (LFG) recovery using horizontal wells. This model is used to simulate more than 680,000 scenarios involving typical values of waste properties, cover characteristics and design pa...

A high density polyethylene geomembrane (GMB) stabilized with hindered amine (light) stabilizers (HALS or HAS) is immersed in four chlorinated water solutions with a simulated free chlorine concentration range of 0.5-5 ppm at five different temperatures (25, 40, 65, 75, and 85 °C) for 70 months. Standard and high pressure oxidative induction time (...

An Antarctic biopile used a composite liner (high density polyethylene geomembrane (GMB) over a geosynthetic clay liner (GCL)) constructed on a coarse granular subgrade to contain hydrocarbon-contaminated soil and leachate. The soil was remediated after 4 years, and the biopile was decommissioned. The liner was exhumed to assess the properties and...

The effects of the silt aggregation, compaction density, and water content of the subgrade on the hydration of five different geosynthetic clay liner (GCL) products is reported based on a series of laboratory column experiments conducted over a six-year period. GCLs meeting typical specifications in terms of minimum hydraulic conductivity and swell...

The interface transmissivity (θ) and hydraulic conductivity (k) are measured for two geosynthetic clay liners (GCLs), one with polymer-enhanced bentonite, when hydrated and permeated with saline (brine) solutions at three different concentrations and Reverse Osmosis (RO) water. Two interface transmissivity values are reported, the 2-week (θ 2-week...

A multiphase, thermohydro-mechanical model of unsaturated soils is presented to assess the risk of desiccation of a geosynthetic clay liner (GCL) in a composite lining system (i.e., a high-density polyethylene geomembrane over a geosynthetic clay liner) under conditions encountered in brine or solar ponds, where temperatures can reach up to 95°C an...

The excavation and analysis of the barrier systems for four engineered containment cells, constructed from 1984 to 1987, is described. Very limited PCB migration was observed over the 22-25 year period prior to decommissioning. PCBs were predominantly, and preferentially, retarded by the geotextiles (GTX) and, where present, geomembranes (GMB). The...

The implications of the tensile stress/strain developed in high density polyethylene (HDPE) geomembranes (GMB) is explored in the context of a reduction in stress crack resistance due to ageing in contact with leachate in a municipal solid waste (MSW) landfill. The experimental evidence of GMB cracking and ultimately failure when subject to excessi...

The dependence of the geosynthetic clay liners (GCLs) soil-water characteristic curve (SWCC) on temperature and overburden stress are characterised experimentally. It is shown that changes in void ratio and temperature alter the relationship between suction and moisture content and new forms of existing SWCC equations are developed. To cover a wide...

The degradation of a 1.5 mm high-density polyethylene geomembrane without hindered amine light stabilizers (HALS) immersed in four chlorinated water solutions is examined over a 3-year period at five temperatures (25, 40, 65, 75, and 85oC). To simulate field conditions in potable water reservoirs in which high successive chlorine doses are introduc...

The effect of texturing (co-extrusion using blowing agent) on the longevity of a geomembrane (GMB) when immersed in synthetic municipal solid waste leachate is investigated over a ~ 3-year period. Based on data at four temperatures (40, 55, 75, and 85oC), the time to antioxidant depletion of the textured portion of a 1.5 mm core thickness high dens...

Canadian Nuclear Laboratories (CNL) proposes to develop a Near Surface Disposal Facility (NSDF) at the Chalk River Laboratories (CRL) site in Ontario, Canada for disposal of CNL’s Low Level Radioactive Waste (LLW) and other suitable wastes meeting the Waste Acceptance Criteria (WAC). The NSDF’s Engineered Containment Mound (ECM) includes base liner...

Geomembranes (GMB) are exposed to harsh conditions in heap leach pads including high stresses and exposure to extreme acidic/basic pregnant leach solutions (PLS). This study investigates the depletion of antioxidant at 85oC for a 2.0 mm blended polyolefin (BPO) and a 2.0 mm linear low density polyethylene (LLDPE) GMBs when exposed to PLS using imme...

A new vapour intrusion contaminant transport model was designed specifically to allow an assessment of the impact of a hydrocarbon fuel spill on air quality in cold region buildings. The model is applied to a recent situation in Antarctica, where a diesel spill impacted the construction of a new building. For the first time, this model allows consi...

A laboratory investigation of the interface transmissivity is reported for five different geosynthetic clay liners (GCLs) and a range of different geomembranes (GMBs) for a range of stresses from 10 to 150 kPa. The GCLs were prehydrated under normal stress before permeation. The GCLs examined comprised three multicomponent (a smooth coated, a smoot...