Suitability of Hydrologic Evaluation of Landfill Performance (HELP) model of the US Environmental Protection Agency for the simulation of the water balance of landfill cover systems

Berger, Klaus; Melchior, Stefan; Miehlich, Günter

doi:10.1007/s002540050092

Cited by 16 publications

(8 citation statements)

References 2 publications

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“…Although the storage‐routing approach accurately simulated drainage in the latter 2 years at the Idaho site, it greatly overestimated drainage during the first few months when the site was irrigated and overestimated water storage change at the Texas site. Previous studies also demonstrate that this approach generally overestimates drainage [ Berger et al , 1996; Khire et al , 1997; Wilson et al , 1999]. The greater accuracy of the Richards' equation based models, the increased computational efficiency of these codes in recent years, recent advances in computer technology, and the availability of online hydraulic parameter data make the use of Richards' equation based codes more feasible.…”

Section: Resultsmentioning

confidence: 99%

“…The Alternative Cover Assessment Program (ACAP) has been set up by the Desert Research Institute (DRI, Nevada), Pacific Northwest National Laboratory (Hanford, Washington), and the Environmental Protection Agency (EPA) to provide detailed water balance monitoring of engineered covers in different types of climate, vegetation, and soils [ Wilson et al , 1999]. Limited code‐comparison studies have been conducted using water balance‐monitoring data from engineered covers [ Nichols , 1991; Berger et al , 1996; Khire et al , 1997; Ogan et al , 1999; Wilson et al , 1999]. Including field data for model input and comparison with model results should strengthen modeling studies.…”

Section: Introductionmentioning

confidence: 99%

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Intercode comparisons for simulating water balance of surficial sediments in semiarid regions

Scanlon

Christman

Reedy

et al. 2002

Water Resources Research

126

118

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[1] Near-surface water balance modeling is often used to evaluate land-atmosphere interactions, deep drainage, and groundwater recharge. The purpose of this study was to compare water balance simulation results from seven different codes, HELP, HYDRUS-1D, SHAW, SoilCover, SWIM, UNSAT-H, and VS2DTI, using 1-3 year water balance monitoring data from nonvegetated engineered covers (3 m deep) in warm (Texas) and cold (Idaho) desert regions. Simulation results from most codes were similar and reasonably approximated measured water balance components. Simulation of infiltrationexcess runoff was a problem for all codes. Annual drainage was estimated to within ±64% by most codes. Outliers result from the modeling approach (storage routing versus Richards' equation), upper boundary condition during precipitation, lower boundary condition (seepage face versus unit gradient), and water retention function (van Genuchten versus Brooks and Corey). A unique aspect of the code comparison study was the ability to explain the outliers by incorporating the simulation approaches (boundary conditions or hydraulic parameters) used in the outlying codes in a single code and comparing the results of the modified and unmodified code. This approach overcomes the criticism that valid code comparisons are infeasible because of large numbers of differences among codes. The code comparison study identified important factors for simulating the near-surface water balance.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intercode comparisons for simulating water balance of surficial sediments in semiarid regions

Scanlon

Christman

Reedy

et al. 2002

Water Resources Research

126

118

View full text Add to dashboard Cite

show abstract

“…(Stothoff, 1997;Kearns and Hendrickx, 1998;Khire et al, 2000). However, some code-comparison studies included some field data for model input (Nichols, 1991;Berger et al, 1996;Khire et al, 1997;Ogan et al, 1999). Field data were collected for this set of comparisons from October 1997 through September 1998 (Table 2.2).…”

Section: Design Procedures For Alternativesmentioning

confidence: 99%

Water Balance Measurements and Computer Simulations of Landfill Covers.

Dwyer¹

2005

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ABSRACTSix large-scale landfill test covers were constructed and monitored for water balance from May 1997 through June 2002. Two of the covers were used as U.S. EPA standard baseline prototypes for comparison: one that met minimum requirements set forth for municipal landfills (RCRA Subtitle D Cover) and the other meeting minimum requirements set forth for hazardous waste landfills (RCRA Subtitle C Cover). Four alternative covers were then constructed side-by-side with the baseline covers to enable direct comparison under the same ambient conditions. The first alternative cover featured a geosynthetic clay liner (GCL) designed for low saturated hydraulic 5 conductivity. The remaining three covers were designed specifically for optimal performance in dry environments; specifically, they were designed to take advantage of the storage capacity of the cover and maximize removal of water via evapotranspiration (ET). Two of the dry environment alternative landfill covers featured capillary barriers within their profiles while the last cover consisted of a simple monolithic soil cover, referred to as an ET Cover. Two common water balance computer programs (Hydrologic Evaluation of LandfillPerformance and UNSAT-H) were evaluated for their applicability as a design tool for landfill covers and for their accurate prediction of a cover's flux. The first evaluation involved using input parameters that simulated a typical design process; the second involved using soil hydraulic properties measured on the covers in their initial or as-built condition along with actual vegetation and weather measurements made on-site; and the 6 final evaluation involved the use of soil hydraulic properties measured on the covers at the end of the monitoring period along with actual vegetation and weather data as input parameters. Neither program predicted flux through these landfill cover profiles with the accuracy desired by regulators and design engineers.7 Table 6.2. Average Annual Simulation Results with UNSAT-H (all units = mm) 160 Table 6.3. Average Annual Simulation Results with HELP (all units = mm/year) 160 As pointed out above, there is some observational evidence that the performance of some landfill covers decreases with time. The amount of water that moves through a landfill cover into the underlying waste is generally not monitored or measured, so the contribution of poorly performing covers to eventual environmental problems is not well known. However, it is known that virtually all parts of the nation have experienced water contamination to some degree caused by leachate leaking from landfills (EPA 1988). Inadequate landfill covers are undoubtedly contributing to some of these problems. In addition to problematic covers, many older landfills were crudely installed 23 (e.g., poor siting or no bottom liner) and thus destined for failure, but capping the entire landfill with a properly designed cover can mitigate these problems.Regulators have the authority to accept alternative landfill covers in lieu of prescr...

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“…The user has the option to specify the initial moisture of different layers or let the model specify the initial MC for each layer based on wilting point, field capacity (FC), and total porosity for each layer of material; the user can define the initial MC for each layer. In the HELP model, surface water runoff is modeled using the US Soil Conservation Service's curve number method, infiltration, evapotranspiration, and percolation using the Darcy equation adapted for unsaturated conditions, lateral drainage using the Boussinesq equation adapted for landfill conditions, and liner leakage using the Darcy equation for saturated conditions [2]. Evapotranspiration is modeled by a plant growth and decay model for perennial and annual crops.…”

Section: Help Model Basicsmentioning

confidence: 99%

Hydrologic evaluation of landfill performance (HELP) modeling in bioreactor landfill design and permitting

Kim

Jain³

et al. 2011

J Mater Cycles Waste Manag

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The practice of operating municipal solid waste landfills as bioreactor landfills has become more common over the past decade. Because simulating moisture balance and flow is more critical in such landfills than in dry landfills, researchers have developed methods to address this problem using the hydrologic evaluation of landfill performance (HELP) model. This paper discusses three methods of applying the HELP model to simulate the percolation of liquids added to landfill waste: the leachate recirculation feature (LRF), the subsurface inflow (SSI) feature, and additional rainfall to mimic liquids addition. The LRF is simple to use but may not be able to bring the landfill to bioreactor conditions. The SSI feature provides a convenient user interface for modeling liquids addition to each layer. The additional rainfall feature provides flexibility to the model, allowing users to estimate the leachate generation rate and the leachate head on bottom liner associated with daily variation in the liquids addition rate. Additionally, this paper discusses several issues that may affect the HELP model, such as the time of model simulation, layers of liquids addition, and the limitations of the HELP model itself. Based on the simulation results, it is suggested that the HELP model should be run over an extended period of time after the cessation of liquids addition in order to capture the peak leachate generation rate and the head on the liner (HOL). From the perspectives of leachate generation and the HOL, there are few differences between single-layer injection and multiple-layer injection. This paper also discusses the limitations of using the HELP model for designing and permitting bioreactor landfills.

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Suitability of Hydrologic Evaluation of Landfill Performance (HELP) model of the US Environmental Protection Agency for the simulation of the water balance of landfill cover systems

Cited by 16 publications

References 2 publications

Intercode comparisons for simulating water balance of surficial sediments in semiarid regions

Intercode comparisons for simulating water balance of surficial sediments in semiarid regions

Water Balance Measurements and Computer Simulations of Landfill Covers.

Hydrologic evaluation of landfill performance (HELP) modeling in bioreactor landfill design and permitting

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