Ecohydrology Monitoring and Excavation of Semiarid Landfill Covers a Decade after Installation

Abstract

closure varies but is generally not expected to exceed more than 30 to 50 years for cases in which institutional Landfill covers are intended to protect buried waste from water control is applied (Suter et al., 1993). However, risks seepage and biointrusion for thirty to thousands of years, yet most cover studies are limited to a few years and do not directly investigate associated with the waste frequently persist beyond innet changes in the soil profile that affect changing landfill performance. stitutional control; hence, the longer-term integrity of We evaluated water balances, vegetation cover, rooting patterns, and landfill covers is of concern. soil profiles of two landfill-cover designs (two plots each) more than a Design of a landfill cover requires consideration of decade after installation at semiarid Los Alamos National Laboratory, several tradeoffs. To keep the wastes dry, the cover is NM, USA: a conventional design of 20 cm of topsoil over compacted designed to minimize seepage. This can be achieved crushed-tuff and an integrated design of 71 cm of topsoil over an in part by storing soil water within the cover and by engineered barrier designed to induce lateral flow (geotextile overmaximizing the subsequent removal of the stored water lying 46 cm of gravel). Water balances for both designs had~3% of through evapotranspiration. The evaporative component precipitation as seepage; the integrated plots lost Ͻ1% of water as of total evapotranspiration can be modified by orienting interflow, probably because the barrier interface had only a 5% slope. The conventional design had a net loss of stored soil water and propor-the cover to maximize incoming solar radiation (e.g., tionally more evapotranspiration than the integrated design. After Nyhan et al., 1997), while the transpiration component more than a decade, (i) vegetation changes included increased biomass can be modified through selection and management of and species diversity on most plots, with proportionally fewer invading plant species on the cover (e.g., Lopez et al., 1988). species and more extensive rooting in the integrated plots; (ii) the Seepage can be reduced further by increasing interflow geotextile was largely unchanged; and (iii) infiltration and subsequent (shallow subsurface lateral flow of water at the interwater penetration occurred primarily via macropores, including rootfaces between layers) that is then diverted to a location channels and animal burrows. Both cover designs effectively miniaway from the waste via engineering structures (e.g., mized seepage during their initial decade, but observed effects of Khire et al., 2000;Nyhan et al. 1997Nyhan et al. , 2001. Conversely, environmental processes such as succession and burrowing are exsurface runoff from the cover should be minimized pected to become progressively more important determinants of cover performance over additional decades.

Field-scale spatial variability of saturated hydraulic conductivity on a recently constructed artificial ecosystem

“…Bormann and Klaassen, 2008;Breshears et al, 2005;Buczko et al, 2001). In contrast to the substantial literature available on K s for natural soils (e.g.…”

“…Cover construction involves encapsulating the hazardous wastes in single or multiple layers of non-reactive material, followed by establishment of vegetation (Breshears et al, 2005). The nature of materials used for cover construction vary considerably, but locally available materials such as non-reactive overburden material and rock wastes from mineral processing are often used.…”

“…Botros et al, 2009;Gόmez et al, 2005;Sobieraj et al, 2002), there has been no systematic field evaluation of K s and its spatial variability for artificially constructed ecosystems such as engineered covers. The few studies conducted on mine waste disposal facilities or artificial catchments are based on indirect methods involving analysis of qualitative data on soil structure (Breshears et al, 2005;Buczko et al, 2001), while results of spatial analysis are often not reported probably due to small sample sizes that restrict such analysis (Gerwin et al, 2009;Holländer et al, 2009;Mazur et al, 2011;Wehr et al, 2005). Notable exceptions are two studies conducted in Germany, where geostatistical analysis of hydraulic parameters derived from pedotransfer functions developed for natural soils showed that particle segregation during transportation and dumping, and amelioration practices contributed to spatial variability on lignite mine spoils (Buczko et al, 2001;Buczko and Gerke, 2005).…”

“…Notable exceptions are two studies conducted in Germany, where geostatistical analysis of hydraulic parameters derived from pedotransfer functions developed for natural soils showed that particle segregation during transportation and dumping, and amelioration practices contributed to spatial variability on lignite mine spoils (Buczko et al, 2001;Buczko and Gerke, 2005). A dye tracer study conducted on covers in New Mexico, USA, a decade after installation showed that macropores caused by root intrusion and fauna enhanced drainage (Breshears et al, 2005). Other studies have evaluated the K s of synthetic geomembranes and clay liners used as hydraulic barriers (e.g.…”

Evaluation of Greenwaste Mulch to Control Runoff Quality from Landfill Sites During Frequent Storms

“…Municipal landfills used for the disposal of solid waste present considerable ecological and human risks unless there is effective landfill cover that minimises erosive runoff and isolates contaminants in the landfill from the nearby environment (Breshears et al 2005). Physical disturbance due to landfill activities can cause loss of vegetation and exposure of the surface soil within the active parts of the site.…”