EPA/600/B-20/219 | January 2020
www.epa.gov/homeland-security-research
United States
Environmental Protection
Agency
&EPA
Hydrologic Evaluation of
Landfill Performance:
HELP 4.0 User Manual
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Office of Research and Development
Homeland Security Research Program
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Hydrologic Evaluation of Landfill Performance
HELP 4.0 User Manual
Edited by:
Thabet Tolaymat
U.S. EPA/Center for Environmental Solutions and Emergency Management,
Cincinnati, OH 45268
Max Krause
U.S. EPA/Center for Environmental Solutions and Emergency Management,
Cincinnati, OH 45268
Center for Environmental Solutions and Emergency Management
Cincinnati, Ohio, 45268
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Notice/Disclaimer
The research described in this manual has been funded by the U.S. Environmental Protection Agency
under contract EP-D-15-12 with GTID. This document has been subjected to the Agency's peer and
administrative review and has been approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute endorsement or recommendation for use.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's land,
air, and water resources. Under a mandate of national environmental laws, the Agency strives to
formulate and implement actions leading to a compatible balance between human activities and the
ability of natural systems to support and nurture life. To meet this mandate, EPA's research program is
providing data and technical support for solving environmental problems today and building a science
knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect
our health, and prevent or reduce environmental risks in the future.
The Center for Environmental Solutions and Emergency Management (CESER) within the Office of
Research and Development (ORD) is the Agency's center for investigation of technological and
management approaches for preventing and reducing risks from pollution that threaten human health
and the environment. The focus of the Laboratory's research program is on methods and their cost-
effectiveness for prevention and control of pollution to air, land, water, and subsurface resources;
protection of water quality in public water systems; remediation of contaminated sites, sediments and
ground water; prevention and control of indoor air pollution; and restoration of ecosystems. CESER
collaborates with both public and private sector partners to foster technologies that reduce the cost of
compliance and to anticipate emerging problems. CESER's research provides solutions to environmental
problems by: developing and promoting technologies that protect and improve the environment;
advancing scientific and engineering information to support regulatory and policy decisions; and providing
the technical support and information transfer to ensure implementation of environmental regulations
and strategies at the national, state, and community levels.
Center for Environmental Solutions and Emergency Management
Greg Sayles, Director
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Table of Contents
Notice/Disclaimer ii
Foreword iii
1. Basic Landfill Design Concepts 1
1.1 Leachate Production 1
1.2 Design For Leachate Control 1
2. About the Model 4
2.1 Overview 4
2.2 Model Assumptions 5
2.2.1 Runoff 5
2.2.2 Water Flow 5
2.2.3 Leakage 6
2.2.4 Vegetative Growth 7
2.3 Additional Technical Documentation 7
3. Getting Started 8
3.1 Downloading the Software 8
3.3 Overview of User Interface 8
4. Inputting Data 11
4.1 Importing HELP v3.07 Data Files 11
4.2 General Information 11
4.2.1 Landfill Title and Location 12
4.2.2 Modeling Parameters 12
4.3 Weather Data 14
4.3.1 Synthetic Weather Generation (WGEN) 14
4.3.2 Importing Precipitation and Temperature Data 15
4.3.3 Importing Solar Radiation Data 16
4.3.4 Wind Speed and Relative Humidity 17
4.3.5 Other Weather-Related Parameters 18
4.4 Runoff Curve Number 18
4.5 Soil & Design 20
4.5.1 Setting Up a New Landfill Profile 21
4.5.2 Specifying a New Landfill Layer 21
4.5.3 Editing Landfill Layers 23
4.5.4 Adding, Moving and Deleting Layers 24
5. Reviewing Data Quality 25
6. Running the Model and Saving Results 26
REFERENCES 27
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Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
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1. Basic Landfill Design Concepts
1.1 Leachate Production
Storage of any waste material in a landfill poses several potential problems. One problem is the possible
contamination of soil, groundwater, and surface water that may occur as leachate produced by water or
liquid wastes moving into, through and out of the landfill migrates into adjacent areas. This problem is
especially important when hazardous wastes are involved because many of these substances are resistant
to biological or chemical degradation, and thus are expected to persist in their original form for many years,
perhaps even for centuries. Given this possibility, hazardous waste landfills should be designed to prevent
any waste or leachate from moving into adjacent areas. This objective is beyond the capability of current
technology but does represent a goal in the design and operation of today's landfills.
In the context of a landfill, leachate is described as liquid that has percolated through layers of waste
material. Leachate may be composed of liquids that originate from a number of sources, including
precipitation, groundwater, waste consolidation, initial moisture storage, and reactions associated with
decomposition of waste materials. The chemical quality of leachate varies as a function of a number of
factors, including the quantity produced, the original nature of the buried waste materials, and the various
chemical and biochemical reactions that may occur as the waste materials decompose. In the absence of
evidence to the contrary, most regulatory agencies prefer to assume that any leachate produced will
contaminate either ground or surface waters; in the light of the potential water quality impact of leachate
contamination, this assumption appears reasonable.
The quantity of leachate produced is affected to some extent by decomposition reactions and initial
moisture content; however, it is largely governed by the amount of external water entering the landfill.
Thus, a key first step in controlling leachate migration is to limit production by preventing, to the extent
feasible, the entry of external water into waste layers. A second step is to collect any leachate that is
produced for subsequent treatment and disposal. Techniques are currently available to limit the amount
of leachate that migrates into adjoining areas to a virtually immeasurable volume, as long as the integrity
of the landfill structure and leachate control system are maintained.
1.2 Design For Leachate Control
Key landfill design features used for leachate control include liner systems, lateral drainage layers, and a
final cap or landfill cover. The following schematic diagram illustrates these key design features, which are
outlined below.
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PRECIPITATION
EVAPO TRANSPIRA TtON
^^ M M. j M M M
sts VERTICAL TAnonn !
^ PERCOLATION LAYER TOPSOIL j INFILTRATIONj
ฉ LATERAL DRAINAGE LAYER SAND LATERAL DRAINAGE
^ (PROM COVER)
GEOMEMBRANE LINER
@ BARRIER SOIL LAYER
T
CLAY
PERCOLATION
VERTICAL
(5) PERCOLATION
LAYER
WASTE
(6) LATERAL DRAINAGE LAYER
@ LATERAL DRAINAGE NET
SAND
LATERAL DRAINAGE
(LEACHATE COLLECTION)
LEAKAGE
GEOMEMBRANE LINER
LATERAL DRAINAGE
LAYER
LATERAL DRAINAGE
(LEAKAGE DETECTION)
SAND
SLOPE
DRAIN
MAXIMUM
BARRIER SOIL LINER
UHAfNAut
DISTANCE
CLAY
it
&
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| PERCOLATION (LEAKAGE!
Schematic of Landfill Profile Illustrating Typical Landfill Features
The bottom layer of soil may be naturally existing material or it may be hauled in, placed and compacted
to specifications following excavation to a suitable subgrade. In either case, the base of the landfill should
act as a liner with some minimum thickness and a very low hydraulic conductivity (or permeability).
Treatments may be used on the barrier soil to reduce its permeability to an acceptable level. As an added
factor of safety, an impermeable synthetic membrane may be placed on the top of the barrier soil layer
to form a composite liner.
Immediately above the bottom composite liner is a leakage detection drainage layer to collect leakage
from the primary liner, in this case, a geomembrane. Above the primary liner are a geosynthetic drainage
net and a sand layer that serve as drainage layers for leachate collection. The drainage layers composed
of sand are typically at least 1-ft thick and have suitably spaced perforated or open joint drain pipe
embedded below the surface of the liner. The leachate collection drainage layer serves to collect any
leachate that may percolate through the waste layers. In this case where the liner is solely a
geomembrane, a drainage net may be used to rapidly drain leachate from the liner, avoiding a significant
buildup of head and limiting leakage. The liners are sloped to prevent ponding by encouraging leachate
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to flow toward the drains. The net effect is that very little leachate is expected to percolate through the
primary liner and virtually no migration of leachate through the bottom composite liner to the natural
formations below. Taken as a whole, the drainage layers, geomembrane liners, and barrier soil liners may
be referred to as the leachate collection and removal system (drain/liner system) or, more specifically, a
double liner system.
After the landfill is closed, the leachate collection and removal system serves basically in a back-up
capacity. However, while the landfill is open and waste is being added, these components constitute the
principal defense against contamination of adjacent areas. Thus, care must be given to their design and
construction. Day-to-day operation of a modern sanitary landfill calls for wastes to be placed in relatively
thin lifts, compacted, and covered with soil each day. Thus, wastes should not remain exposed for more
than a few hours. Although the daily soil cover serves effectively to hide the wastes and limit the access
of nuisance insects and potential disease vectors, it is of limited value for preventing the formation of
leachate. Thus, even though a similar procedure can be used for hazardous wastes, the drainage/liner
system must function well throughout and after the active life of the landfill.
When the capacity of the landfill is reached, the waste cells are covered with a cap or final cover, typically
composed of four distinct layers. At the base of the cap is a drainage layer and a liner system layer similar
to that used at the base of the landfill. Again, geomembrane liners would normally be used in conjunction
with the barrier soil liner for hazardous waste landfills but have been used less frequently in municipal
waste landfills. The top of the barrier soil layer is graded so that water percolating into the drainage layer
will tend to move horizontally toward some removal system (drain) located at the edge of the landfill or
subunit thereof. A layer of soil suitable for vegetative growth is placed at the top of final cover system to
complete the landfill. A 2-ft-thick layer of soil having a loamy, silty nature serves this purpose well. The
upper surface is graded so that run-on is restricted and infiltration is controlled to provide moisture for
vegetation while limiting percolation through the topsoil. Runoff is promoted but controlled to prevent
excessive erosion of the cap. The vegetation used should be selected for ease of establishment in a given
area, promotion of evapotranspiration, and year-round protection from erosion. The root system should
not penetrate, disrupt, or desiccate the upper liner system (Layers # 3 and # 4). Grasses are usually best
for this purpose; however, local experts should be consulted to aid in selection of appropriate species.
The combination of site selection, surface grading, transpiration from vegetation, soil evaporation,
drainage through the sand, and the low hydraulic conductivity of the barrier soil liner serves effectively to
minimize leachate production from external water. Added effectiveness is gained by the use of
geomembrane liners in the cap in conjunction with the barrier soil liner. The cap should be no more
permeable than the leachate collection and removal system so that the landfill will not gradually fill and
overflow into adjacent areas following abandonment of the landfill (a phenomenon sometimes referred
to as the "bathtub" effect).
The HELP model has been developed as a tool to be used by designers and regulatory reviewers to
evaluate and select practical landfill designs that minimize leakage of leachate to adjacent areas and, thus,
minimize potential contamination problems.
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2. About the Model
2.1 Overview
The Hydrologic Evaluation of Landfill Performance (HELP) model is a quasi-two-dimensional hydrologic
model of water movement across, into, through and out of landfills. The model accepts weather, soil, and
design data. It uses solution techniques that account for key factors affecting water movement in a landfill,
including: surface storage; snowmelt; runoff; infiltration; evapotranspiration; vegetative growth; soil
moisture storage; lateral subsurface drainage; leachate recirculation; unsaturated vertical drainage; and
leakage through soil, geomembrane, and composite liners. Landfill systems including various
combinations of vegetation, cover soils, waste cells, lateral drain layers, low permeability barrier soils, and
synthetic geomembrane liners may be modeled. The model was developed to conduct water balance
analysis of landfills, cover systems, and solid waste disposal and containment facilities. As such, the model
facilitates rapid estimation of the amounts of runoff, evapotranspiration, drainage, leachate collection,
and liner leakage that may be expected to result from the operation of a wide variety of landfill designs.
The model, applicable to open, partially closed, and fully closed sites, is a tool for both designers and
permit writers.
HELP model Version 4 was developed by EPA ORD/CESER. HELP model Versions 1, 2, and 3 were
developed by the U.S. Army Engineer Waterways Experiment Station (WES) for EPA. The model was
developed in response to needs in the Resource Conservation and Recovery Act (RCRA) and
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, better known as
Superfund), as identified by the EPA Office of Land Management and Emergency Response.
As in the earlier versions of the model, the hydrologic processes modeled can be divided into two
categories: surface processes and subsurface processes. The surface processes modeled are snowmelt,
interception of rainfall by vegetation, surface runoff, and surface evaporation. The subsurface processes
modeled are evaporation from the soil profile, plant transpiration, unsaturated vertical drainage, barrier
soil liner percolation, geomembrane leakage, and saturated lateral drainage.
Daily infiltration into the landfill is determined indirectly from a surface water balance. Infiltration is
assumed to equal the sum of rainfall, surface storage, and snowmelt minus the sum of runoff, additional
storage in snowpack, and evaporation of surface water. No liquid water is assumed to be held in surface
storage from one day to the next except in the snowpack or when the top soil is saturated and runoff is
not permitted. Each day, the available water for infiltration, runoff or evaporation from water on the
surface is determined from the surface storage, discharge from the snowpack and/or rainfall. Snowfall is
added to the surface snow storage which is depleted by either evaporation or melting. Snowmelt is added
to the available water and is treated as rainfall except that it is not intercepted by vegetation. This
available water is used to compute the runoff by the Soil Conservation Society (SCS) rainfall-runoff
relationship. The interception is the measure of water available to evaporate from the surface.
Interception in excess of the potential evaporation is added to infiltration. Surface evaporation is then
computed. Potential evaporation from the surface is first applied to the interception; any excess is applied
to the snowmelt, then to the snowpack and finally to the groundmelt. Potential evaporation in excess of
the evaporation from the surface is applied to the soil column and plant transpiration. The snowmelt and
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rainfall that does not run off or evaporate is assumed to infiltrate into the landfill along with any ground
melt that does not evaporate.
The first subsurface processes considered are soil evaporation and plant transpiration from the
evaporative zone of the upper sub-profile. A vegetative growth model accounts for the daily growth and
decay of the surface vegetation. The other subsurface processes are modeled one subprofile at a time,
from top to bottom, using a design dependent time step ranging from 30 minutes to 6 hours. A storage-
routing procedure is used to redistribute the soil water among the modeling segments that comprise the
sub-profile. This procedure accounts for infiltration or percolation into the subprofile and
evapotranspiration from the evaporative zone. Then, if the subprofile contains a liner, the model
computes the head on the liner. The head on the liner is then used to compute the leakage/percolation
through the liner and, if lateral drainage is permitted above the top of the liner, the lateral drainage to
the collection and removal system.
2.2 Model Assumptions
The modeling procedures are based on many simplifying assumptions. Generally, these assumptions are
reasonable and consistent with the objectives of the model when applied to standard landfill designs.
However, some of these assumptions may not account for unusual designs.
2.2.1 Runoff
Runoff is computed using the SCS method based on daily amounts of rainfall and snowmelt. The model
assumes that areas adjacent to the landfill do not drain onto the landfill. The time distribution of rainfall
intensity is not considered. As such, the model cannot be expected to give accurate estimates of runoff
volumes for individual storm events on the basis of daily rainfall data. However, because the SCS rainfall-
runoff relationship is based on considerable daily field data, long-term estimates of runoff should be
reasonable.
The SCS method does not explicitly consider the length and slope of the surface over which overland flow
occurs. HELP v4.0 provides two methods (labelled Methods 2 and 3) that address this limitation by
including procedures for computing curve numbers that take into consideration the effect of slope and
slope length (the SCS limitation is not addressed in Method 1). This limitation is not a concern if the slope
and slope length of the landfill do not differ dramatically from those of the test plots upon which the SCS
method is based. The SCS method would probably underestimate runoff somewhat where the overland
flow distance is very short, or the slope is very steep, or when the rainfall duration is very short and the
intensity is very high.
2.2.2 Water Flow
The HELP model assumes Darcian flow by gravity influences through homogeneous soil and waste layers.
It does not consider explicitly preferential flow through channels such as cracks, root holes, or animal
burrows but allows for vertical drainage through the evaporative zone at moisture contents below field
capacity. Similarly, the model allows vertical drainage from a layer at moisture contents below field
capacity when the inflow would occupy a significant fraction of the available storage capacity below
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capacity. The drainage rate out of a segment is assumed to equal the unsaturated hydraulic conductivity
of the segment corresponding to its moisture content, provided that the underlying segment is not a liner
and is not saturated. In addition to these special cases, the drainage rate out of a segment can be limited
by the saturated hydraulic conductivity of the segment below it. When limited, the model computes an
effective gradient for saturated flow through the lower segment. This permits vertical percolation or
lateral drainage layers to be arranged without restrictions on their properties so long as they perform as
their layer description implies and not as liners.
The model assumes that a) the soil moisture retention properties and unsaturated hydraulic conductivity
can be calculated from the saturated hydraulic conductivity and limited soil moisture retention
parameters (porosity, field capacity, and wilting point) and b) that the soil moisture retention properties
fit a Brooks-Corey relation (Brooks et al., 1964) defined by the three soil moisture retention parameters.
Upon obtaining the Brooks-Corey parameters, the model assumes that the unsaturated hydraulic
conductivity relationship with soil moisture is well described by the Campbell equation.
The model does not explicitly compute flow by differences in soil suction (soil suction gradient) and as
such does not model the draw of water upward by capillary drying. This draw of water upward is modeled
as an extraction rather than transport of water upward. Therefore, it is important that the evaporative
zone depth be specified as the depth of capillary drying. Drainage downward by soil suction exerted by
dry soils lower in the landfill profile is modeled as Darcian flow for any soil having a relative moisture
content greater than the lower soils. The drainage rate is equal to the unsaturated hydraulic conductivity
computed as a function of the soil moisture content. As such, the rate is assumed to be independent of
the pressure gradient.
2.2.3 Leakage
Leakage through barrier soil liners is modeled as saturated Darcian flow. Leakage is assumed to occur only
as long as there is head on the surface of the liner. It is assumed that the head driving the percolation can
be represented by the average head across the entire liner and can be estimated from the soil moisture
storage. It is also assumed that the liner underlies the entire area of the landfill and, conservatively, that
when leakage occurs, the entire area of the landfill leaks. The model does not consider aging or drying of
the liner and therefore the saturated hydraulic conductivity of the liner does not vary as a function of
time.
Geomembranes are assumed to leak primarily through holes. The leakage passes through the holes and
spreads between the geomembrane and soil until the head is dissipated. The leakage then percolates
through the soil at the rate dependent on the saturated hydraulic conductivity and the pressure gradient.
Therefore, the net effect of a geomembrane is to reduce the area of percolation through the liner system.
The model assumes the holes to be uniformly distributed and the head is distributed across the entire
liner. The model does not consider aging of the liner and therefore the number and size of the holes do
not vary as a function of time. In addition, it is conservatively assumed that the head on the holes can be
represented by the average head across the entire liner and can be estimated from the soil moisture
storage. It is also assumed that the liner underlies the entire area of the landfill.
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The lateral drainage model is based on the assumption that the saturated depth profile is characteristic
of the steady-state profile for the given average depth of saturation. As such, it is assumed that the lateral
drainage rate for steady-state drainage at a given average depth of saturation is representative of
unsteady lateral drainage rate for the same average saturated depth. In actuality the rate would be
somewhat larger for periods when the depth is building and somewhat smaller for periods when the depth
is falling. Steady drainage implies that saturated conditions exist above the entire surface of the liner,
agreeing with the assumptions for leakage through liner systems.
2.2.4 Vegetative Growth
The model assumes the vegetative growth and decay can be characterized by a vegetative growth model
developed for crops and perennial grasses. In addition, it is assumed that the vegetation transpires water,
shades the surface, intercepts rainfall, and reduces runoff in similar quantities as grasses or as an adjusted
equivalence of leaf area index.
2.3 Additional Technical Documentation
For additional technical documentation, please refer to the Engineering Documentation for HELP Model
version 3 available on the EPA's Hydrologic Evaluation of Landfill Performance (HELP) Model web page.
https://www.epa.gov/land-research/hvdrologic-evaluation-landfill-performance-help-model
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3. Getting Started
3.1 Downloading the Software
HELP v4.0 is written for Microsoft Excel and has been
tested for use in Excel 2007 (Windows operating system)
and higher. The version of the model can be downloaded
from EPA's website at the following address:
https://www.epa.gov/land-research/hvdrologic-
evaluation-landfill-performance-help-model.
The model uses macros, which require that you enable
macros when you first open the file (see text box). After
enabling macros, read the initial disclaimer and click the
OK button to proceed to using HELP V4.0.1
3.3 Overview of User Interface
The interface of the model is a worksheet titled Dashboard. The Dashboard consists of five main panels,
including an overarching Control Panel and four panels for providing model input: General Information,
Weather, Runoff Curve Number, and Soil & Design.
Enabling Macros in Excel
HELP v4.0 uses an Excel workbook with
embedded macros to support the user
interface. The use of spreadsheets with macros
received from an unknown source can
represent an IT systems security risk.
Therefore, MS Excel requires that you confirm
the source by clicking the "Options" button or
"Enable Content" button at the top of the
screen (depending on the version of Excel that
you are using) before you begin.
1 Note that zooming in or out with Excel could change relative font sizes and visible text. It is recommended that
zoom not exceed +/-10%.
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General Information
:xaiTipje
Title
Address I \
fJashwIle
Coordinate* (degrees) Lat
ExaniWe RCRA Landfill
Year* ol Simulation
LF Area (acres) | 15 00
% Subject to Runoff | 100
Weather
Simulate with
WGEN
Import NOAW
NREL Data
PrecipitaiRJPK.,^
Temp-eraUice
Solar Radiation
IN 37218
Lorr-g -8b 89
LJ S blandara
Specify tnrtial (Wurture? No
Water/snow ซorag^(|n)
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Enter or Import | Wind 5p*>rcd/Rcl Humidity (5)
ctor Other Parameters
iner Parameters /y
tMtmg season. LAJ A evap zottt) ^ -
Runoff Curve Number
HฃLPcomputซd curvo number (3}
HELP will u*e the curve number: 82 2
Dashboard ฎ
Impart v3 Q7 Files Reset All
Run HELP
Model
Soil & Design Add'lnsert New Layers [ Reset |
,qS Q Temporanty suspend laj*f rule checking
Silty Loam
Cofe - Coarse Sand
LD3E Membrane
SIC - Salty Clay (Moderate)
Municipal Solid Waste |MSW) (900 pcyf
LFS Loamy Fine Sand
Drainage Net (0.5 on)
8 HD5ฃ Membrane
10 HD 3E Membrane
11 Un>?r Soil (High)
Data Entry Panels
The Control Panel allows you to initiate actions that apply to the whole model, including importing data
files from HELP v3.07, resetting all fields, reviewing model input, and running the HELP model. These
actions are described in more detail in the following sections. With a few exceptions, the four data input
panels work independently, allowing you to input data and model values in any sequence. You are
encouraged to decide on the units of measure for the model (see General Information panel) before you
enter information that references a specific system of measurement (e.g., landfill area). In addition, the
model will not compute a runoff curve number using Method 3 until you have entered information about
the topmost layer of the landfill in the Soil & Design panel. The model will prompt you to alert you to
these types of information dependencies.
The general recommended workflow for entering information and running the model is as follows:
Download any external files that you plan to use, including weather data from external sources or
parameter value files for weather simulation (see Section 4.3)
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Import and/or enter information describing the landfill location and weather context and landfill
design parameters
Review information using the Review function in the Control Panel
When you have met all input requirements and are satisfied with the model inputs, run the HELP
model and review the output
Additional information regarding each of these steps is described in Sections 4-6.
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4. Inputting Data
The following section provides stepwise guidance for importing and/or entering information in each of
the input panels. The model includes aids to help you find information from external sources (e.g.,
weather data) and to check for missing information and values that are outside of the expected range. In
some cases the model will allow you to continue entering information even when missing or invalid values
are encountered. This is intended to allow you to build the model with minimal disruptions to your work
flow. The model will check for missing and invalid values and remind you to enter or correct this
information before it will run (see Section 6).
Appendix A includes a list of model input requirements and valid ranges for each data element or model
parameter value. Input requirements for each panel are described below.
4.1 Importing HELP v3.07 Data Files
HELP v4.0 allows you to import precipitation, temperature,
solar radiation, other landfill location parameters (e.g., wind
speed, relative humidity), curve number values, and landfill
design information generated using HELP v3.07. To do so, click
the Import v3.07 Files from the Control Panel at the top of the
dashboard. A pop-up window with several import options will
be displayed.
Check the box next to the data file(s) that you wish to import
and click Import Files. A file browser window will open for you
to navigate to and select the data files. See Appendix A for a
list of data elements and model parameter values that will be
imported from each HELP v3.07 data file type.
4.2 General Information
General information used in
the HELP model includes
landfill location information
and model simulation
parameters. You can import
elements of general landfill
information from existing
HELP v3.07 data files (.D10 and
.Dll) or enter the information
directly through the interface.
Section 4.1 describes how to
import general information.
Import HELP V3.07 Files
1^-
Data files created with HELP v3.07 can be imported to
HELP v4.0. Identify the data files that you would like to
import and select "import files." For each selected data
file type, you will be asked to locate and upload the file.
r Precipitation (.D4)
r Temperature (.D7)
P Solar Radiation (.D13)
r Landfill Location Parameters (.D11)
r Landfill Design and CN (.D10)
Import Files
General Information
Edit
Reset
Title
Address
Example RCRA Landfill
Nashville
TIM
37201
Coordinates (degrees) Lat
36.17
Long
-86.78
Years of Simulation
LF Area (acres)
% Subject to Runoff
15.00
100
Units
U S Standard
Specify Initial Moisture?
Watertsnow storage {in}
No
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Depending on the type of information, the model will ask you to input information through a pop-up user
form (when you click Edit) or directly via the interface, as outlined below. If you click Reset in the General
Information panel, all information in the panel will be deleted. If you import HELP v3.07 data files containing
general information, existing information in the General Information panel will be overwritten by imported
information.
4.2.1 Landfill Title and Location
To enter or edit landfill title, address, and latitude and
longitude coordinates, click Edit in the top right corner of
the General Information panel, and a separate data entry
form will pop-up. Enter the project title, street address,
city and state. The HELP model requires valid latitude
coordinates. If you plan to simulate weather using the
built-in weather generator (see Section 4.3.1), the model
will also require valid longitude coordinates. If you know
the latitude and longitude of your landfill site, you can
enter them directly in the Latitude and Longitude fields
(in decimal degrees). If you do not know the latitude and
longitude, you can enter the 5-digit ZIP code for the
landfill, and click on the Find Lat/Long for ZIP. The model
will look up the latitude and longitude associated with
the ZIP code and populate both the Latitude and Longitude fields.2
General Information
Title
Street address
City
State
ZIP code
Latitude
Longitude
Example RCRA Landfill
Nashville
Tennessee
37201
36.17
Find Lat/Long for ZIP
-86 78
(degrees)
(degrees)
Cancel
Submit
User Tip
4.2.2 Modeling Parameters
Modeling parameters are located in the lower portion of the General Information panel. Enter values for
the following parameters directly through the user interface
2 Note that HELP v4.0 is designed for use with latitudes and longitudes in the U.S.
12
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Units: Select either U.S. Standard or Metric.
Years of Simulation: Enter number of years (1-100)
you would like the simulation to run. Note that the
number of years must be less than or equal to the
shortest number of years of daily data available for
precipitation, temperature or solar radiation (e.g., if
you have 30 years of precipitation data and 10 years
of solar radiation data, years of simulation can be no
more than 10).
Landfill Area: The size of the landfill approached horizontally at birds-eye view, in acres or hectares
depending on the selected measurement system.
% Subject to Runoff: The portion of the area that is sloped in a manner that would permit drainage
off the surface. Runoff estimates predicted by the model are equal to the computed runoff by the
curve number method times this percentage. The difference between the computed runoff and the
actual runoff is added to the infiltration.
Specify Initial Moisture? Initial moisture content for the landfill layers can be specified if data are
available. If you know the initial moisture content, select Yes. If you select No, the model assumes
near steady-state values and runs the first year of the simulation to improve the initialization to
steady-state. Soil water content at the end of this year of initialization are used as the initial values
for the simulation period.
Initial water/snow water storage on landfill: If you decide to specify initial moisture, enter the
amount of water or snow water on the landfill surface. You can enter 0 for no initial water or snow
water on the surface. If you do not specify initial moisture, this value will be treated as zero in the
model.
User Tip
If you answered Yes to the Specify Initial Moisture? question, you will be asked to specify
initial moisture for certain landfill layers in the Soil & Design input panel.
User Tip
Enter units of measure at the start of data
entry. This information is required prior to
entering other information that references a
specific system of measurement (e.g.,
landfill area). A warning message will display
to alert you of this dependency.
13
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4.3 Weather Data
The HELP model requires several
inputs to model the weather
context of a landfill, including daily
precipitation, temperature and
solar radiation; average annual
wind speed; quarterly relative
humidity; growing season start and
end dates; maximum leaf area
index (LAI); and evaporative zone
depth. Depending on the
parameter, you can import weather
data from existing HELP v3.07 data
files (,D4, ,D7, .Dll and .D13), simulate weather data using the WGEN weather generator, import data
downloaded from National Oceanic and Atmospheric Administration (NOAA) or National Renewable
Energy Laboratory (NREL) websites, or enter the information directly through the interface.
Section 4.1 describes how to import general information from existing HELP v3.07 files from the Control
Panel. The Simulate Weather button in the Weather panel allows you to run a weather simulation for
precipitation, temperature and solar radiation using the built-in WGEN weather generator. The Import
NOAA/NREL Data button in the Weather panel allows you to import data downloaded from NOAA and NREL
websites. The Enter or Import button for wind speed and relative humidity generates a form that can be
used to import data from NREL or enter data directly. The Enter button for other parameters generates a
form for entering growing season, leaf area index, and evaporative zone depth information. The Enter/Edit
icons allow you to see and edit weather data inputs. If you click Reset in the Weather panel, all
information in the panel will be deleted.
4.3.1 Synthetic Weather Generation (WGEN)
HELP v4.0 will generate up to 100 years of daily precipitation, temperature, and solar radiation data
stochastically for a location. The synthetic weather generator is based on a routine developed by the USDA
Agricultural Research Service (Richardson and Wright, 1984). Weather parameter values used in the
synthetic weather generator are imported from a database of calculated weather parameters for over
13,000 points located on a 0.25 x 0.25 degree grid across the continental U.S. The program retrieves
parameter values from the closest grid point in the dataset based on the latitude and longitude specified
forthe landfill location. For more information on WGEN and the gridded dataset used to develop location-
specific parameter values for use in WGEN, please refer to Appendix B.
Weather
Data Method
Simulate with
WGEN
Import NOAA/
NREL Data
Reset |
Parameter Years of Data
Precipitation 30 @ Gi
Temperature 30 ฉ
Solar Radiation 30 ฉ
Enter or Import
Enter
^ Wind Speed/Rel Humidity 0 (VJ
Other Parameters py
(proving season, LAI & evap zone)
14
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User Tip
The weather simulation option in HELP v4.0 requires a set of 60 weather parameter inputs to synthetically
generate weather for a specified location. These inputs are stored in a WGEN parameter values file. Before
running the Simulate Weather option, it is necessary to download the "WGEN Par Values for OPP Grid.xlsx" file
from https://www.epa.gov/land-research/hvdrologic-evaluation-landfill-performance-help-model, store the
file on your local PC, and note the folder location as you will navigate to it when running the simulation. The
model will alert you if the file is not available.
To generate synthetic weather data (precipitation, temperature, and solar radiation), verify that the
latitude and longitude coordinates have been entered in General Information, then click the Simulate
Weather button in the Weather panel.
A prompt for the WGEN parameter value file is
displayed the first time the weather simulation is run
for a given location or any time that the location
information is reset. See the User Tip text box above
for information on downloading the parameter value
file). If you are prompted to import WGEN parameter
values, click Import on the Import WGEN Parameter
Values dialog to continue. A file browser window will
open for you to navigate to and select the parameter
value file. Select the file and click Open.
Once the parameter values are imported (or if you imported the values for a previous weather simulation
for the same location), the program will prompt you to input the number of years of weather data to be
synthetically generated, from 1 to 100. Enter the number of years and click Submit to run the weather
simulation. The weather simulation will generate daily values of precipitation, temperature, and solar
radiation for the number of years specified. When finished, the data status column in the Weather panel
will show a check mark {S).
The resulting output may be viewed or edited by clicking the Enter/Edit icon.
4.3.2 Importing Precipitation and Temperature Data
You can import daily precipitation and temperature data from existing Help v3.07 ,D4 and ,D7 files,
respectively, as described in Section 4.1, or synthetically generate precipitation and temperature values
using the Simulate Weather option, as described in Section 4.3.1. Alternatively, you can import daily
precipitation and temperature data that you
have downloaded from NOAA's National
Centers for Environmental Information (NCEI)
Climate Data Online (CDO) website. To import
NOAA data, first download data files from three
weather stations near the landfill using the
procedure described in Appendix C.
Import WGEN Parameter Values
X
1 To run the weather simulator, you will need to import WGEN
parameter values for this location.
Please save the WGEN parameter value file to a local drive
and click "import" to continue.
! Cancel ;
j Import
User Tip
The HELP model requires that you import daily
weather data in full year increments (January 1 -
December 31). If you attempt to import a partial year
of data, the model will interpret the data for the part
of the year for which you did not import data as
"missing" and the import will fail (you will receive an
error message indicating too many missing values).
15
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Once you have downloaded the files, click the Import NOAA/NREL Data button in the Weather panel. A
dialog will prompt you to choose the type of data to import. To import precipitation and temperature data
from NOAA, select this option and click the Import Data button. A pop-up window reminding you to
download data will appear. Click Import from this window, and a file browser window will open for you
to navigate to and select the three data files (precipitation, minimum temperature, and maximum
temperature), one at a time. Once the import is complete, the data status column will show a check mark
(S)I and the years of precipitation and temperature data available for simulation will be displayed in the
Weather panel.
To view or edit daily precipitation or temperature
data, click the Enter/Edit icon (>) next to
Precipitation or Temperature in the Weather panel,
and the model will open (unhide) the Precipitation D4
or Temperature D7 worksheet, respectively. These
worksheets contain daily data in a 10 column by 3,700
row matrix. Each year of data is contained in 37 rows,
resulting in totaling 370 cells, where cells 366-370 are
ignored for a typical year and cells 367-370 are ignored
for leap years. Average monthly rainfall or
temperature are shown near the top of the worksheet
to the right of the 10 columns of daily data. This allows
you a quick check to ensure the data qualitatively
seem appropriate for the site location.
After viewing precipitation or temperature data, click
Return to Main Dashboard. This will close the precipitation or temperature worksheet and return you to
the main user interface.
4.3.3 Importing Solar Radiation Data
You can import daily solar radiation data from an existing Help v3.07 .D13 file, as described in Section 4.1
or synthetically generate solar radiation values using the Simulate Weather option, as described in
Section 4.3.1. Alternatively, you can import solar radiation data that you have downloaded from NREL's
National Solar Radiation Database (NSRDB). To import NSRDB data, first download data files using the
procedure described in Appendix D.
Once you have downloaded the files, click Import NOAA/NREL Data next to Solar Radiation in the
Weather panel. A dialog will prompt you to choose the type of data to import. To import solar radiation
data from NREL (NSRDB), select this option and click the Import Data button. A pop-up window reminding
you to download data will appear along with a prompt to enter the site name. After entering the Site
Name, click Import from this window, and a file browser window will open for you to navigate to and
select the directory containing the data files. Once complete, the data status column will show a check
mark (S) and the years of solar radiation data available for simulation will be displayed in the Weather
panel.
Modifying Daily Precipitation,
Temperature and Solar Radiation Data
The model allows you to edit daily
precipitation, temperature and solar radiation
data in the respective worksheets (e.g., to
simulate a storm or drought event). However,
any changes should be carefully documented
and daily values should fall within valid ranges
(see Appendix A) to avoid errors and erroneous
results. Note that if you imported weather data
from v3.07 files, the monthly average values
will not automatically recalculate when you
change daily values. To reset changes to
imported daily precipitation, temperature and
solar radiation data, you can re-import the
original data files.
16
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To view or edit daily solar radiation data, clickthe Enter/Edit icon next to Solar Radiation in the
Weather panel, and the model will open (unhide) the Solar Radiation D13 worksheet. The solar radiation
worksheet is structured using the same approach as the precipitation and temperature worksheets, as
described in Section 4.3.1. After viewing solar radiation data, click Return to Main Dashboard, and the
program will close the worksheet and return you to the main user interface.
4.3.4 Wind Speed and Relative Humidity
HELP v4.0 uses average annual wind speed and average
quarterly relative humidity to model monthly
evapotranspiration (see text box). You can import wind
speed and relative humidity data from an existing Help
v3.07 .Dll file (along with other information; see
Appendix A), as described in Section 4.1. Alternatively,
you can import wind speed and relative humidity data
that you have downloaded from NREL's NSRDB or enter
the information directly.
To import NSRDB data, first download data files using
the procedure described in Appendix E. Once you have
downloaded the files, click Enter or Import next to Wind
Speed/Rel Humidity in the Weather panel. Then, click
the Import button on the resulting pop-up user form. A
pop-up window reminding you to download data will
appear. Click Import from this window, and a file browser
window will open for you to navigate to and select the
data file.
To enter the data directly or to edit imported or
previously entered data, click the Enter or Import button
or click the Enter/Edit icon next to Wind Speed/Rel Humidity in the Weather panel, and a pop-up
user form will be displayed. Enter or edit the average annual wind speed and/or average quarterly
relatively humidity values for the landfill location and click Update.
Once the wind speed and relative humidity data are complete (imported and/or entered directly), the
data status column in the Weather panel will show a check mark (S).
User Tip
The HELP model v3.07 .Dll file contains wind speed, relative humidity, growing season, leaf area index, and
evaporative zone depth data. When you import from a .Dll file (i.e., using the Import v3.07 Files button from
the Control Panel), any previously imported or entered data for these fields will be replaced. If you plan to use
HELP v3.07 data for one or more of these parameters, it is recommended that you import the .Dll files first
(e.g., before importing an NSRDB file containing wind speed and relative humidity data).
HELP v4.0 Approach to Modeling
Evapotranspiration
Unlike previous versions of the model, the HELP
4.0 model does not permit the use of a default
evapotranspiration option with location specific
guidance. HELP v4.0 requires location-specific
average annual wind speed and average
quarterly relative humidity to model monthly
evapotranspiration at the site.
Wind Speed and Relative Humidity
Average wind speed | s MPH
Average first quarter relative humidity
Average second quarter relative humidity
Average third quarter relative humidity
Average fourth quarter relative humidity r^%
Import j Cancel { Update
17
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4.3.5 Other Weather-Related Parameters
Other weather-related parameters used by the HELP model are growing season start and end dates,
maximum leaf area index, and evaporative zone depth. Definitions of these parameters and data sources
are described in Appendix F.
You can import data for these parameters from an existing
Help v3.07 .Dll file (along with other information; see
Appendix A), as described in Section 4.1. Alternatively, you
can enter the data directly by clicking the Enter button or
the Enter/Edit icon next to Other Parameters in
the Weather panel, after which a pop-up user form will
display. This user form will also allow you to edit imported
data. See the User Tip text box above for considerations
regarding the order of data import, entry and editing. Enter
or edit the values for growing season start and end dates,
maximum leaf area index, and evaporative zone depth for the landfill location and click Update.
Once the other weather-related parameters are complete (imported and/or entered directly), the data
status column in the Weather panel will show a check mark (S).
4.4 Runoff Curve Number
As with previous versions of the model, HELP v4.0 models the rainfall-runoff process using the Soil
Conservation Service (SCS) curve-number method. The model uses an SCS runoff curve number (CN) for
Antecedent Moisture Condition II (AMC-II) determined using one of the following methods:
Method 1, User-specified CN: The user enters an SCS AMC-II CN directly
Method 2, Modified User's CN: The user enters an SCS AMC-II CN, landfill surface slope, and slope length,
and the model computes a modified SCS AMC-II CN, accounting for slope and slope length
X
Other Weather-Related Parameters
Start of growing season
day of year
End of growing season
day of year
Maximum leaf area index
1
Evaporative zone depth
inches
Cancel | Update
18
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Method 3, HELP-computed CN: The user enters the landfill surface slope, slope length, and vegetative
cover, and the model computes an SCS AMC-II CN
based on these inputs and the soil texture of the
topmost layer (entered in the Soil & Design panel,
as described in Section 4.5)
You can import runoff curve number information
from existing HELP v3.07 data files (.D10) or enter
the information directly through the interface.
Section 4.1 describes how to import existing .D10
files from the Control Panel.
To enter information, directly, click in the text box in
the Runoff Curve Number panel, and then click the
drop down arrow to display the list of methods for
computing the SCS AMC-II CN. Select the desired
method from the options listed.
Next, click Edit, and the model will display a pop-
up user form for entering information required for
the selected method. When you are done entering
the required information, click Submit. The user
form will close, and the SCS AMC-II CN entered by
you (Method 1) or computed by the model
(Method 2 or 3) will be displayed in the Runoff
Curve Number panel. If insufficient information is
entered, the SCS AMC-II CN field will display "TBD"
along with a note explaining that additional input
is required.
Vegetative Cover (CN Method 3)
If you use Method 3 to determine an ACS AMC-II CN,
the model will provide a dropdown list with the
following options for specifying the quality of
vegetative cover on the landfill:
Bare ground
Poor stand of grass
Fair stand of grass
Good stand of grass
Excellent stand of grass
Most landfills will tend to have a poor or fair stand
of grass, as landfills are typically not ideal support
systems for vegetative growth.
Runoff Curve Number Edit | Rese| |
Additional input needed
User-specified curve number (1)
Modified user s curve number (2)
HELP-computed curve number (3)
Runoff Curve Number
Edit |
Reset |
HELP-computed curve number (3)
HELP will use the curve number: TBD*
Additional input needed
User Tips
If you click Reset in the Runoff Curve Number panel, all information in the panel will be deleted. If you import
existing .D10 files, existing information in the Runoff Curve Number panel will be overwritten by imported
information.
The HELP model v3.07 .D10 file contains model simulation, runoff curve number and landfill design inputs (See
Appendix A). When you import from a .D10 file, any previously imported or entered data for these fields will be
replaced. If you plan to use HELP v3.07 data for one or more of these parameters, it is recommended that you
import the .D10 files first.
Method 3 computes an SCS AMC-II CN based on inputs from both the Runoff Curve Number and Soil & Design
panels. If you enter CN inputs for Method 3 before specifying the topmost layer of the landfill, the CN in the
Runoff Curve Number panel will display 'TBD." When you specify the topmost layer, the CN will be computed
and displayed.
19
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4.5 Soil & Design
The landfill profile, including information about layer functions and the characteristics of soils,
geomembranes and other materials, is specified in the Soil & Design panel. The panel allows you to set
up the profile by importing data or defining and initial number of layers, specify and edit layer types and
properties, and adjust the design by adding, moving and deleting layers. For information on the default layer
textures and their associated characteristics, refer to the table in Appendix G.
You can import elements of general landfill information from existing HELP v3.07 .D10 data files or start from
scratch with a new landfill profile. Section 4.1 describes how to import existing .D10 files. Section 4.5.1,
below, describes how to start a new profile from scratch. Sections 4.5.2 and 4.5.3 describe how to specify
new layers and edit existing layers (newly defined or imported). Section 4.5.4 describes how to rearrange
the landfill profile by adding, moving and deleting layers. If you click Reset in the Soil & Design panel, all
information in the panel will be deleted.
Layer Rules, Data Validation and Data Validation Control
in the Soil & Design Panel
Information Requirements and Layer Rules
The HELP model includes requirements for the information that must be provided when specifying layers, as
outlined in Table 1 (below) and Appendix A. The model also requires that the arrangement of layers in the
landfill profile conform to the following basic rules:
A vertical percolation layer cannot be underlying a lateral drainage layer
A barrier soil liner cannot be underlying another barrier soil liner
A geomembrane liner cannot be placed between two barrier soil liners
A geomembrane liner cannot be underlying another geomembrane liner
A barrier soil liner cannot be placed directly between two geomembrane liners
The top layer cannot be a barrier soil liner
The top layer cannot be a geomembrane liner
The profile can contain no more than five barrier soil liners and geomembrane liners
Data Validation Approach and Control - Layer Information
The program will check for missing information, values outside the valid range, and consistency of layer
arrangement with the above rules when you click Submit after entering values or editing information for a layer.
If you try to submit a layer with incomplete or invalid information, the program will notify you and give you the
option of returning to the form to fill in the information or saving the layer with incomplete information. You
can Edit the layer later or use the Review function from the Control Panel to identify missing data before you
run the model.
Data Validation Approach and Control - Layer Arrangement
In addition, the program will check for consistency of layer arrangement when you Move or Delete layers. You
can turn off layer rule checking (e.g., if you are in the midst of moving several layers) by clicking Temporarily
suspend layer rule checking in the Soil & Design panel. You can use the Review function from the Control Panel
to check for conformance with layer rules before you run the model.
20
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4.5.1 Setting Up a New Landfill Profile
To define a landfill profile from scratch, start by clicking
Add/Insert New Layers. A pop-up user form will asking to
specify the number of layers (up to 20) to include in the initial
profile. Note that the number of layers can be changed after
this initial specification, as explained in Section 4.5.4. After
entering the initial number of layers, click Submit.
Soil & Design
1 Layer to be specified
2 Layer to be specified
3 Layer to be specified
4 Layer to be specified
5 Layer to be specified
6 Layer to be specified
7 Layer to be specified
8 Layer to be specified
9 Layer to be specified
10 Layer to be specified
11 Layer to be specified
Blank Profile
~ Temporarily suspend layer rule checking
Add/Insert New Layers | Reset |
gs i o
GS i 0
GS * 0
C5!0
GS t 0
esa
GS i 0
GS $ fr
GS i 0
GS ~ Q
The program will produce a "blank" profile. Each layer will
initially be labelled "Layer to be specified." To the right of
each layer will be three icons that are used for editing,
moving, and deleting layers (see figure to the right). From this
blank profile, you can add information for each layer by
clicking the Enter/Edit icon next to each layer, as
described in Section 4.5.2.
Edit S | \ De|ete
Move
G5 *t
4.5.2 Specifying a New Landfill Layer
To specify information for a new layer, click the Enter/Edit icon next to the layer. For a new layer,
the program will produce a pop-up user form asking you to select a layer category from a drop-down
menu and to specify whether the layer will be a standard HELP layer, a previously saved custom layer, or
a new custom layer. After making these selections, the user form will display the fields appropriate for
the selected layer category and will prepopulate information for standard layers and previously defined
which they are editable, and whether the layer characteristic is required, conditional, or optional for a
particular layer category. Appendix G provides a list of standard layers included in the HELP Model,
including texture numbers, descriptions, and layer characteristics (e.g., porosity, hydraulic conductivity).
The HELP model uses texture numbers to refer to standard soil, waste, geosynthetic drainage nets, and
geomembranes included in the model. See Appendix G for standard layers and associated texture numbers.
These are the same standard layers and texture numbers used in HELP v3, and the texture numbers can be used
to cross-referencing the model versions. When the user defines a custom layer, HELP v4.0 automatically defines
a new texture number for the custom layer (HELP v3.07 defaults to a texture number of 0). The new texture
number is displayed in the pop-up user form for the layer (when you click the Edit icon) and is listed in the
output (Model Data). These texture numbers are included as a reference so you can reuse the custom layers in
modified or new designs.
After entering the required information for a layer, click Submit. If you click Reset while entering or editing
information for a layer, the user form and characteristics of the layer will be deleted. If you try to submit
a layer with incomplete or invalid information, the program will notify you of missing fields or invalid
values. You will have the option of correcting the information or saving the incomplete/invalid
Texture Numbers
21
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information. Incomplete or invalid values will need to be corrected before you run the HELP model. See
Sections 4.5 and 5 for a description of the layer validation approach and control.
After submitting information for a layer, you can continue to edit information for blank ("to be specified")
layers as described above until the landfill profile is completely specified. After entering the required
information for a layer, click Submit. If you click Reset while entering or editing information for a layer,
the user form and characteristics of the layer will be deleted. If you try to submit a layer with incomplete
or invalid information, the program will notify you of missing fields or invalid values. You will have the
option of correcting the information or saving the incomplete/invalid information. Incomplete or invalid
values will need to be corrected before you run the HELP model. See Sections 4.5 and 5 for a description
of the layer validation approach and control.
Table 1. Landfill Layer Data Elements
Layer characteristic
Layer Category
Editable?
Notes
Final cover soil (topmost layer)
Vertical percolation layer (soil)
Lateral drainage layer (soil)
Barrier soil liner
Waste
Geomembrane liner
Geosynthetic drainage net
Standard Layer
Custom Layer
Layer thickness
R
R
R
R
R
R
R
Yes
Yes
Total porosity
R
R
R
R
R
R
No
Yes
Field capacity
R
R
R
R
R
R
No
Yes
Wilting point
R
R
R
R
R
R
No
Yes
Saturated hydraulic
conductivity
R
R
R
R
R
R
R
No
Yes
Initial moisture
C
C
C
C
C
Yes
Yes
Required for categories
labelled "C" when user
chooses to specify initial
moisture
Drainage length
C
R
Yes
Yes
Required for lateral drainage
layer when it is the lowest
drainage layer in a subprofile
Drainage slope
C
R
Yes
Yes
Required for lateral drainage
layer when it is the lowest
drainage layer in a subprofile
Leachate recirculation
0
Yes
Yes
Recirculation to layer
C
Yes
Yes
Required for lateral drainage
layer when leachate
recirculation is non-zero
22
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Layer characteristic
Layer Category
Editable?
Notes
Final cover soil (topmost layer)
Vertical percolation layer (soil)
Lateral drainage layer (soil)
Barrier soil liner
Waste
Geomembrane liner
Geosynthetic drainage net
Standard Layer
Custom Layer
Subsurface inflow
O
O
O
O
0
O
O
Yes
Yes
Membrane pinhole density
R
Yes
Yes
Membrane installation
defects
R
Yes
Yes
Membrane placement quality
R
Yes
Yes
Geotextile transmissivity
C
Yes
Yes
Required for membrane
when placement quality = 6
Legend: R - Required, C - Conditional, O - Optional
After submitting information for a layer, you can continue to edit information for blank ("to be specified")
layers as described above until the landfill profile is completely specified.
4.5.3 Editing Landfill Layers
To edit the information for a landfill layer,
including a layer imported from a HELP v3.07
.D10 file, click the Enter/Edit icon next
to the layer. The program will produce a pop-
up user form with the previously defined
information for the layer. Table 1 describes the
fields that will be displayed depending on the
layer category. If you change the layer
category on click Reset while editing a layer,
this will reset the user form, and you will be
asked to enter a layer description and
additional information, as described in Section
4.5.1 for a new layer. If you change the layer
description while editing a layer, the form will
update information corresponding to the new
layer description (e.g., predefined porosity
values for a standard soil layer).
Soil & Design
Total porosity (vol/vol)
Subsurface inflow* (in/y)
Layer category | Lateral drainage layer (soil)| V| < Standard HELP layer
c Saved custom layer
c New custom layer
Layer description | CoS - Coarse Sand
Layer thickness J 12 (in)
Field capacity (vol/vol)
Drainage length (ft)
Drainage slope (%)*
0.417 Wilting point (vol/vol)
0.045 Saturated hydraulic
conductivity (cm/s)
200
Leachate recirculation
Layer texture no.
1.00E-02
0.018
* Optional (blank value assumed to be "0" or N/A)
Layer No. 2
Cancel
Reset
Submit
23
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After editing information for a layer, click Submit. The program will run a layer validation check. If missing
or invalid values are found, you will have the option of correcting the information or saving the
incomplete/invalid information. Incomplete or invalid values will need to be corrected before you run the
HELP model. See Sections 4.5 and 5 for a description of the layer validation approach and control.
4.5.4 Adding, Moving and Deleting Layers
The program gives you the option of adding and rearranging layers in the Soil & Design panel using the
Add, Move and Delete icons (see Section 4.5). To add a layer click Add/Insert New Layers, and the
program will display a user form asking you to specify the number of layers to add and the position of the
new layer(s). To move a layer to a new position in the profile, click the Move icon next to the layer to be
moved. The program will display a user form that asks you to specify the new location of the selected
layer. To delete a layer, click the Delete icon next to the layer.
The program will check layer rules when you add, move or delete layers and will notify you if the resulting
layer arrangement is inconsistent with layer rules (see text box in Section 4.5). You can turn off layer rule
checking (e.g., if you are in the midst of moving several layers) by clicking Temporarily suspend layer rule
checking in the Soil & Design panel. Inconsistencies with the layer rules will need to be corrected before
you run the HELP model. See Sections 4.5 and 5 for a description of the layer validation approach and
control.
24
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5. Reviewing Data Quality
HELP v4.0 uses three layers of data validation to help assure the quality of model inputs and results. First,
the model reviews user input when you enter information in a pop-up user form and click Submit or when
you perform other functions like moving or deleting layers or changing the runoff curve number method.
Second, the model allows you to review model inputs at any time by clicking the Review button from the
Control Panel. Finally, when you click Run HELP Model from the Control Panel, the program reviews input
before running the modeling routines.
The different data validation routines review data and other modeling input for completeness (i.e., review
for missing values) and check whether data and values are within the valid range and are expressed in
valid formats (e.g., numeric vs. non-numeric). Appendix A lists input requirements and valid ranges used
by the validation routines. The model also reviews the landfill profile to ensure that layers arrangement
is consistent with model requirements, as described in Section 4.5.
Input value review summary
Please review the following errors and/or warnings:
The following required information is missing:
- Project title
- Percent landfill area subject to runoff
- Drainage length (Layer No. 6)
Value input errors:
- Leachate must recirculate to a vertical percolation or lateral drainage layer (Layer No. 9)
Warning messages:
- Geomembrane installation defects value not provided; the model will use a value of 0 (Layer No. 3)
Please provide and/or correct this information before running the HELP model.
If missing values, values outside of the valid range, or values using invalid formats are detected during
data entry and editing, the program will notify you of the missing/invalid input. In most cases, the model
will give you the option of filling in or correcting the input before continuing or saving the input with the
expectation that you will return and complete or correct the input before running the model. This is
intended to allow for efficient data entry and editing. If you do not return and complete or correct the
input, missing or invalid input will be identified when you click Review or Run HELP Model. The model will
not run until all missing and invalid input is addressed.
The review functions also check for inputs that could represent incorrect interpretation of the input
requirements. For example, if the model requires an input expressed as a percentage (e.g., 10%) and
detects an input value of less than 1 (e.g., 0.1), it will generate a warning message to alert the user to
check and confirm the input. Warning messages do not need to be addressed for the model to run.
25
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6. Running the Model and Saving Results
It is recommended that the model be saved with the current inputs, prior to running the model. After
reviewing your input and saving a copy of the model, click Run HELP Model from the Control Panel. The
program will run a data validation check. If detected, the program will notify you of missing or invalid
values and will stop running. If the inputs pass the validation check, the program will run the model. As
the program cycles through simulation years, it will generate a temporary worksheet for each year,
indicating that the model is running. These worksheets will later be moved to an output file where you
can review the information in detail.
User Tips
If a run-time error is encountered while working with the model, the program should be reloaded by closing
and reopening the HELP Model v4.0 in Excel. This will reset any protections in worksheet and avoid potential
issues with running the model following an error condition. If a run-time error is encountered after the model
has started generating output, you may find a residual "Tempout" file in the directory from which you launched
the model. You must delete this file before your next run or your output may not be saved properly.
To avoid any potential data loss, it is recommended that a clean version of the model, including your current
inputs, be saved prior to running the model.
Longer simulation run times have been noted with HELP Model v4.0 compared to the previous version. This is
in part a function of Excel limitations and, in some cases, individual operating environments. EPA has taken steps
to optimize run times and, if further opportunities to optimize run-times are identified, may implement further
improvements in the future.
When the HELP model isfinished running, a dialog boxwill appearand asking you to identify the format(s),
Excel or PDF, for saving output file(s). When you select the desired format and click Submit, a file browser
window will open for you to navigate to and save the output file(s).
The output files will contain the following tabs (Excel) or pages (PDF):
Model Input: Summary of model input, including landfill layer information, general design data,
evapotranspiration data, and mean monthly rainfall and temperature data.
Annual Simulation Output: Simulation results by year including daily estimates for rainfall, runoff,
evapotranspiration, lateral drainage, and leakage/percolation through liners, and head on liners. A
summary table of annual totals is presented after the daily results for each simulation year.
Averages Annual Totals Summary: Summary of results for the entire simulation period including
average annual total rainfall, runoff, evapotranspiration, lateral drainage and drainage recirculation,
subsurface inflow, leakage/percolation through liners, head on liners, and change in water storage.
Peak Values Summary: Summary of results for the entire simulation period including peak values for
rainfall, runoff, lateral drainage and drainage recirculation, leakage/percolation through liners, head
on liners, and location of maximum head on liners.
Final Water Storage: Summary of final water storage in each layer at the end of the simulation period.
26
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REFERENCES
Frye et al. (2016). Daily gridded weather for pesticide exposure modeling. Environmental Modeling &
Software. 82(2016):167-173.
Richardson, C. W., and Wright, D. A. (1984). "WGEN: A model for generating daily weather variables/'
ARS-8, Agricultural Research Service, USDA. 83 pp.
27
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Appendix A
HELP Model Data and Parameter Value Input Requirements
Input Field
Input Options
Required to
Run?
Valid values
Comments
User Input
Panel
HELP V3.07
Data File
Title
General
Information
D10
Yes
Any value up to
60 characters
Click Edit to enter or edit
in pop-up form
Address
General
Information
No
Any
Click Edit to enter or edit
in pop-up form
City
General
Information
Dll
No
Any
Click Edit to enter or edit
in pop-up form
State
General
Information
Dll
No
Dropdown list
provided
Click Edit to enter or edit
in pop-up form
ZIP code
General
Information
No
Validated based
on U.S. ZIP codes
Click Edit to enter or edit
in pop-up form
Latitude (Lat)
General
Information
Dll
Yes
-14.32 to 71.25
Click Edit to enter, find, or
edit in pop-up form; value
set based on ZIP code if
not specified by user
Longitude (Long)
General
Information
Yes
Click Edit to enter, find, or
edit in pop-up form; value
set based on ZIP code if
not specified by user
Years of Simulation
General
Information
Yes
1 to < years of
weather data
(max 100 years)
Units
General
Information
D10
Yes
Dropdown list
provided
Landfill Area (LF Area
acres)
General
Information
D10
Yes
>0
User prompted to set
units if LF Area (acres) is
entered before units
specified
% Subject to Runoff
General
Information
D10
Yes
0 -100%
Specify Initial Moisture?
General
Information
D10
Yes
Yes/No
Water/snow storage
General
Information
D10
Contingent
>0
Required if initial
moisture specified
Precipitation (daily)
D4
Yes
Recommended that data
be simulated with WGEN,
or imported from NOAA
data or HELP v3.07 file
Temperature (daily)
D7
Yes
Recommended that data
be simulated with WGEN,
or imported from NOAA
data or HELP v3.07 file
28
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Input Field
Input Options
Required to
Run?
Valid values
Comments
User Input
Panel
HELP V3.07
Data File
Solar Radiation (daily)
D13
Yes
Recommended that data
be simulated with WGEN,
or imported from NOAA
data or HELP v3.07 file
Average annual wind
speed
Weather
Dll
Yes
0-20 MPH (0-
32.2 KPH)
Click Enter or Import to
enter or edit Wind
Speed/Rel Humidity in
pop-up form; option to
import NREL data
Average relative humidity,
first quarter
Weather
Dll
Yes
>0 -100%
Click Enter or Import to
enter or edit Wind
Speed/Rel Humidity in
pop-up form; option to
import NREL data
Average relative humidity,
second quarter
Weather
Dll
Yes
>0 -100%
Click Enter or Import to
enter or edit Wind
Speed/Rel Humidity in
pop-up form; option to
import NREL data
Average relative humidity,
third quarter
Weather
Dll
Yes
>0 -100%
Click Enter or Import to
enter or edit Wind
Speed/Rel Humidity in
pop-up form; option to
import NREL data
Average relative humidity,
fourth quarter
Weather
Dll
Yes
>0 -100%
Click Enter or Import to
enter or edit Wind
Speed/Rel Humidity in
pop-up form; option to
import NREL data
Start of growing season
Weather
Dll
Yes
0-367
Click Enter to enter or
edit Other Parameters in
pop-up form
End of growing season
Weather
Dll
Yes
0-367
Click Enter to enter or
edit Other Parameters in
pop-up form
Maximum leaf area index
Weather
Dll
Yes
>0
Click Enter to enter or
edit Other Parameters in
pop-up form; model is
insensitive to differences
in LAI values >5
Evaporative zone depth
Weather
Dll
Yes
>0, cannot
exceed depth to
top membrane
Click Enter to enter or
edit Other Parameters in
pop-up form
Curve number method
Curve
Number
D10
Yes
1-3
Dropdown list
provided
29
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Input Field
Input Options
Required to
Run?
Valid values
Comments
User Input
Panel
HELP V3.07
Data File
CN Method 1, SCS AMCII
CN
Curve
Number
D10
Contingent
>0
Click Edit to enter or edit
in pop-up form; required
for Method 1
CN Method 2, SCS AMCII
CN
Curve
Number
D10
Contingent
>0
Click Edit to enter or edit
in pop-up form; required
for Method 2
CN Method 2, slope
Curve
Number
D10
Contingent
>0 -100%
Click Edit to enter or edit
in pop-up form; required
for Method 2
CN Method 2, slope length
Curve
Number
D10
Contingent
>0 to effective
length calculated
at LF width = 10
yds or 10 m
Click Edit to enter or edit
in pop-up form; required
for Method 2
CN Method 3, slope
Curve
Number
D10
Contingent
>0 -100%
Click Edit to enter or edit
in pop-up form; required
for Method 3
CN Method 3, slope length
Curve
Number
D10
Contingent
>0 to effective
length calculated
at LF width = 10
yds or 10 m
Click Edit to enter or edit
in pop-up form; required
for Method 3
CN Method 3, soil texture
Yes
Determined based on
topmost landfill layer
description
CN Method 3, vegetative
cover
Curve
Number
D10
Contingent
Dropdown list
provided
Click Edit to enter or edit
in pop-up form; required
for Method 3
Layer category
Soil &
Design
D10
Yes
Dropdown list
provided
Click Enter/Edit
to enter or edit in pop-up
form
Layer description
Soil &
Design
D10
Yes
Dropdown list or
custom entry
Click Enter/Edit
to enter or edit in pop-up
form
Layer type
Yes
Determined based on
layer category
Layer thickness
Soil &
Design
D10
Yes
>0
Click Enter/Edit
to enter or edit in pop-up
form
Total porosity
Soil &
Design
D10
Contingent
>0-1
Click Enter/Edit
to enter or edit in pop-up
form; required for soil,
waste, geonets; not
required for barrier soil
liner unless initial
moisture is user-
specified; user-defined
for custom layers
30
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Input Field
Input Options
Required to
Run?
Valid values
Comments
User Input
Panel
HELP V3.07
Data File
Field capacity
Soil &
Design
D10
Contingent
>0 - < porosity
Click Enter/Edit
to enter or edit in pop-up
form; required for soil,
waste, geonets; not
required for barrier soil
liner; user-defined for
custom layers
Wilting point
Soil &
Design
D10
Contingent
>0 - < field
capacity
Click Enter/Edit
to enter or edit in pop-up
form; required for soil,
waste, geonets; not
required for barrier soil
liner; user-defined for
custom layers
Saturated hydraulic
conductivity
Soil &
Design
D10
Yes
>0
Click Enter/Edit
to enter or edit in pop-up
form
Initial moisture
Soil &
Design
D10
Contingent
> wilting point
and < porosity
Click Enter/Edit
to enter or edit in pop-up
form; required if initial
moisture is user-
specified; not required for
barrier soil or
geomembrane liners
Drainage length
Soil &
Design
D10*
Contingent
>0
Click Enter/Edit
to enter or edit in pop-up
form; required for lateral
drainage layers
Drainage slope
Soil &
Design
D10
Contingent
0 - 50%
Click Enter/Edit
to enter or edit in pop-up
form; required for lateral
drainage layers
Leachate recirculation
Soil &
Design
D10
No
0 -100%
Click Enter/Edit
to enter or edit in pop-up
form
Recirculation to layer
Soil &
Design
D10
Contingent
1 - 20; vertical
percolation or
lateral drainage
layer only
Click Enter/Edit
to enter or edit in pop-up
form; required when
leachate recirculation is
non-zero
Subsurface inflow
Soil &
Design
D10
No
>0
Click Enter/Edit
to enter or edit in pop-up
form
Geomembrane pinhole
density
Soil &
Design
D10
Contingent
>0
Click Enter/Edit
to enter or edit in pop-up
form; required for
membranes
31
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Input Field
Input Options
Required to
Run?
Valid values
Comments
User Input
Panel
HELP V3.07
Data File
Geomembrane installation
defects
Soil &
Design
D10
Contingent
>0
Click Enter/Edit
to enter or edit in pop-up
form; required for
membranes
Geomembrane placement
quality
Soil &
Design
D10
Contingent
Dropdown list
provided
Click Enter/Edit
to enter or edit in pop-up
form; required for
membranes
Geotextile transmissivity
Soil &
Design
D10
Contingent
>0
Click Enter/Edit
to enter or edit in pop-up
form; required if
membrane placement
quality = 6
* HELP v4.0 requires the user to enter drainage length for all components of a lateral drainage layer, including soil
and geosynthetic drainage nets. Some HELP v3.07 files do not contain drainage length for soil lateral drainage layers.
If the user imports a HELP v3.07 file without this information, the model will alert the user that the information is
missing during data validation (e.g., when the user clicks Review or Run Help Model from the Control Panel).
32
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Appendix B
Weather Simulation in HELP v4.0
HELP v4.0 incorporates the WGEN synthetic weather generator developed by the USDA Agricultural
Research Service (Richardson and Wright, 1984). Weather parameter values used in the synthetic weather
generator are imported from a dataset of weather parameters for over 13,000 points located on a 0.25 x
0.25 degree (latitude/longitude) grid across the 48 contiguous states of the U.S. developed by EPA's Office
of Pesticide Programs (OPP) using two NOAA data products. This appendix provides a brief summary of
the WGEN program, OPP gridded weather dataset, and methods used to integrate weather simulation
into HELP v4.0.
Weather Generator (WGEN)
The WGEN synthetic weather generator was originally added to Version 2 of the HELP model to provide
users with the option of simulating daily values for precipitation, temperature and solar radiation. Prior
to this enhancement, the HELP model used mean monthly values. Version 3 of the model maintained this
capability, incorporating WGEN for daily weather simulation.
WGEN simulates daily values for precipitation, maximum temperature, minimum temperature, and solar
radiation using historical weather data. The model is designed to preserve the dependence in time, the
correlation between variables, and the seasonal characteristics in actual weather data for a specified
location.
The precipitation component of WGEN is a Markov chain-gamma model. A first-order Markov chain is
used to generate the occurrence of wet or dry days. When a wet day is generated, a two-parameter
gamma distribution is used to generate the precipitation amount. Precipitation occurrence probabilities
are conditioned on whether the previous day was a wet or dry. WGEN uses two precipitation probability
values - probability of a wet day following a wet day and probability of a wet day following a dry day-for
each month for each location to account for location-specific seasonal characteristics. WGEN uses a two-
parameter gamma distribution model, where the probability density function is defined by shape and
scale parameters.
Temperature (maximum and minimum) and solar radiation variables are modeled using harmonic
equations to simulate seasonal weather patterns. Harmonic equation are defined for each variable
(maximum and minimum temperature and solar radiation) using statistically determined parameter
values. Daily temperature and solar radiation values are modeled based on precipitation condition (wet
or dry) and position on the harmonic, as defined by the day of the year.
In total, WGEN requires 60 parameter values for each location:
Twelve monthly probability of a wet day given a previous wet day (Pw/w) values
Twelve monthly probability of a wet day given a previous dry day (Pw/d) values
Twelve monthly shape parameter values (a) to specify the rainfall gamma distribution
Twelve monthly scale parameter values ((B) to describe rainfall distribution
33
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Five parameters describing the maximum temperature harmonic equation: means for wet and
dry days, coefficient of variation, amplitude, and amplitude of coefficient of variation
Four parameters describing the minimum temperature harmonic equation: mean (wet or dry),
coefficient of variation, amplitude, and amplitude of coefficient of variation
Three parameters describing the solar radiation harmonic equation: means for wet and dry days
and amplitude
The version of WGEN incorporated Version 3 of the HELP model in is currently available as a standalone
application that can be run on the GoldSim Player.3 This version of WGEN uses the original parameter
values calculated based on weather data for the 20 years from 1951 to 1970. Precipitation parameter
values were calculated for 139 locations and temperature and solar radiation parameter values were
calculated for 31 locations across the 48 contiguous states of the U.S.
The default application allows the user to specify a latitude for one of the 139 locations with precipitation
parameters as the basis for the simulation. The model also allows users to enter precipitation and
temperature data to correct for differences in weather between the closest WGEN default location and
the actual user location of interest (e.g., landfill site). A separate program, WGEN PAR, is provided to allow
users to generate their own parameter values based on actual weather data at a specific location of
interest.
For more information, please refer to Richardson and Wright (1984).
Daily Gridded Weather Data
EPA OPP compiled daily precipitation, temperature, wind speed, and solar radiation data for the period
1961 to 2014 using the NOAA products: the NOAA Climate Prediction Center (CPC) Unified Rain Gauge
Analysis and National Center for Environmental Prediction (NCEP) and National Center for Atmospheric
Research (NCAR) Reanalysis. The NOAA CPC Unified Rain Gauge analysis provides daily precipitation data
on a 0.25 x 0.25 degree grid resolution across the 48 contiguous U.S. states. The NCEP/NCAR Reanalysis
provides temperature (daily mean, maximum, and minimum), wind speed, and solar radiation data on a
2.5 x 2.5 degree rectilinear global grid.
To assemble a complete dataset, OPP compiled the CPC Unified Rain Gauge data at its native resolution
and spatial extent. OPP extracted NCEP/NCAR Reanalysis data for the continental U.S. and interpolated
the data from the native 2.5 x 2.5 degree rectilinear grid to the finer 0.25 x 0.25 degree grid used for the
CPC Unified Rain Gauge analysis using bilinear interpolation. Bilinear interpolation was first performed in
the x direction, followed by the y direction. This interpolation scheme was applied uniformly across the
lower 48 contiguous U.S. states for consistency and to limit any data voids.
For more information on the OPP gridded weather dataset, please refer to Frye et al. (2016).
3 https://support.goldsim.com/hc/en-us/articles/115012797188-WGEN-Weather-Simulator
34
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HELP v4.0 Integration
For HELP v4.0, EPA developed a more spatially resolved and up-to-date application of WGEN using the
OPP gridded weather dataset and incorporated this application of WGEN in the HELP model. Daily
precipitation, temperature (maximum and minimum), and solar radiation data were downloaded from
the OPP dataset. For efficiency, statistical software was used to calculate the 60 parameter values
required for WGEN for each of the more than 13,000 grid locations. Parameter values were calculated
based on the most recent 30-year period contained in the dataset (1985-2014).
The WGEN PAR program was run for a random sample of grid locations and parameter values calculated
using statistical software were compared to results generated by the WGEN PAR program to validate the
approach (confirm that the statistical analysis produced the same values as would have been obtained by
applying the WGEN PAR program).
To integrate WGEN as a weather simulation tool, the Fortran code described by Richardson and Wright
(1984) was reproduced as a VBA module in HELP v4.0. A complete dataset of parameter values was
compiled for each grid location and is available to HELP model users for running weather simulation.
Weather simulation results obtained using the integrated WGEN model were compared to results
obtained using the standalone version of WGEN (GoldSim Player) to confirm that the version integrated
in the HELP model conforms with the standalone version of WGEN.
Section 4.3.1 of this User Manual describes the operation of weather simulation using the integrated
WGEN model. For weather simulation, the HELP model uses the WGEN parameter values for the grid point
closest to the specified landfill location (latitude/longitude). Alternatives to this approach were explored
as part of the integration design, including reapplication of bilinear interpolation used to develop the OPP
dataset. Given the density of grid locations, it was determined that parameter values calculated using
bilinear interpolation would not be significantly different than those of the surrounding grid points. The
logic of obtaining values was the closest grid point was implemented to minimize unnecessary data
manipulation.
35
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Appendix C
Downloading Precipitation and Temperature Data from the
NOAA Website
If you are not using precipitation and temperature data files from HELP model v3.07 or the synthetic
weather generation option, you will need to import historical precipitation and temperature data from
the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental
Information (NCEI) from three weather stations near the landfill site. Weather stations occasionally
experience data gaps (e.g., during maintenance or due to damage, and, over time, stations are brought
on line or retired). The HELP model combines the data from the three selected stations to minimize data
gaps.
NOAA provides historical precipitation and air temperature data through the Climate Data Online (CDO)
search tool at https://www.ncdc.noaa.gov/cdo-web/search. As noted in Section 3, if you choose to import
precipitation and temperature data downloaded from the NOAA website, the HELP model will prompt
you to identify "primary," "secondary" and "tertiary" data files to be imported. You should select the
weather station that balances proximity to your site with relatively complete coverage of precipitation
and temperature variables for the date range selected as your "primary" file. Your secondary and tertiary
stations should also be located near the site and should provide relatively good coverage.
Please use the following steps to select and download precipitation and temperature data files to be
imported to the HELP model:
1. On the Climate Data Online Search page
(https://www.ncdc.noaa.gov/cdo-web/search):
a. Under Select Weather Observation Type/Dataset,
select Daily Summaries from the dropdown list
b. Under Select Date Range, select a date range of
interest using the calendar feature, and click Apply
(see text box for important information on
specifying the date range)
c. Under Search For, use the default selection,
Stations
d. Under Enter a Search Term, type location
information for the landfill site (e.g., city and state)
e. Click Search and the website will produce a map
showing your search results
2. On the Search Results: Daily Summaries page
(https://www.ncdc.noaa.gov/cdo-web/results)
a. Zoom-in to your landfill's location
Date Range
You will need to select data for a period (in
years) that equals or exceeds the number
of years of simulation that you plan to use
for the model.
In general, longer periods and more recent
data will be more representative of future
typical weather conditions, though care
should be taken to account for unusual
weather periods (e.g., extended drought)
when selecting the date range for
download.
NOTE The HELP model requires that you
import daily weather data in full year
increments (January 1 - December 31). If
you attempt to import a partial year of
data, the model will interpret the data for
the part of the year for which you did not
import data as "missing" and the import
will fail (you will receive an error message
indicating too many missing values).
36
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b.
c.
3
NOAA CDO weather
station icon
d.
e.
Click on the icon for a station near your site, and the website will provide a
pop-up box with Station Details
Review the Start/End dates in the Station Details box.
^ If the dates do not sufficiently cover the date range of interest or
^ provide relatively poor coverage (e.g., <90%), select another station
(Step 2b)
If the dates cover the date range of interest or provide relatively good coverage (e.g., >90%),
click Full Details, and the website will take you to a Station Details page
Scroll down to Station Data Inventory, Access & History, and review the information under
Available Data Types
^ If precipitation and/or temperature data are not available for this station, use your
^ browser Back button to return to the
Search Results: Daily Summaries page,
and select another station (Step 2b)
f. If the station provides precipitation and
temperature data:
i. Click on the Precipitation link, and review
the Start/End dates and Coverage %
information for the variable PRCP
ii. Click on the Air Temperature link, and
review the Start/End dates and Coverage %
information for the variables TAVG, TMAX,
TMIN and/or TOBS (see text box)
^ If the station does not provide
precipitation and temperature data with
relatively good coverage over the date
range of interest, use your browser Back
button to return to the Search Results:
Daily Summaries page, and select
another station (Step 2b)
g. If the station provides precipitation and
temperature data with relatively good
coverage over the date range of interest:
i. Click Add to Cart
ii. Click on the Cart (Free Data) button in the upper right hand corner of the page, and the
website will open the Cart for further data download specification
3. On the Cart: Daily Summaries page (https://www.ncdc.noaa.gov/cdo-web/cart):
a. Under Select the Output Format, select Custom GHCN-Daily CSV
Reviewing and Selecting NOAA
Temperature Data
The HELP model is designed to run with the
NOAA observed temperature (TOBS) variable
alone, average temperature (TAVG) variable
alone or maximum and minimum temperature
(TMAX, TMIN) variables (combined). The model
will review column headers in your NOAA data
file. If it detects TOBS, it will use the data from
this field. If not, it will use data from the TAVG
field. If neither the TOBS or TAVG fields are
detected, it will use a combination of TMAX and
TMIN data. The model will not independently
assess the completeness of the data in each
field.
When reviewing temperature data for weather
stations near your site (Step 2f), review the
start and end dates and coverage for all
temperature variables. Try to find three
stations that provide good coverage for the
date range of interest for the same variable
(TOBS or TAVG) or set of variables (TMAX and
TMIN). When selecting fields to download (Step
3), select the single variable or set of variables
with the best coverage.
37
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b. Under Select the Date Range, confirm or modify the date range of interest
c. Click Continue, and the website will open a Custom Options page
4. On the Custom Options: Daily Summaries page (https://www.ncdc.noaa.gov/cdo-
web/customoptions):
a. Under Station Detail & Data Flag Options:
i. Leave the default Station Name selected
ii. Ensure that the Units match the units you selected in the General Information panel of the
HELP model dashboard
b. Under Select Data Types for Custom Output:
i. Click the plus sign + next to Precipitation to display the available options and check the box
by Precipitation (PRCP)
ii. Click the plus sign + next to Air Temperature and check the box for either TOBS, TAVG, or
both TMAX and TMIN, depending on the variables you identified as providing the best
coverage across weather stations in the vicinity of your site (see Additional Notes text box)
c. Click Continue, and the website will open the Review Order page
5. On the Review Order page (https://www.ncdc.noaa.gov/cdo-web/review):
a. Enter the email address you would like results delivered
b. Click Submit Order
c. Scroll down to the bottom of the Request Submitted page and beneath Need more? click Go
back and complete another search
6. Repeat Steps 1-5 for two more stations
Additional Notes
In some areas, you may have difficulty finding three stations with relatively good precipitation and temperature
data coverage over the date range of interest. Try to find at least one station with good data coverage, and make
this your primary data file. The model uses your secondary and tertiary data files to fill gaps in the primary file,
so data completeness is not as important. At a minimum, try to find stations for your secondary and tertiary data
files that include both precipitation and temperature data over a reasonable period of time.
Once data have been requested from the NOAA website, it may take up to a couple hours for you to receive the
data. You must download the file within a week.
WARNING: Do not edit the format or contents of the .csv data files received from NOAA/CDO. Doing so will
result in errors in running the model.
7. When you receive your files from NOAA/CDO, save them to a file folder as .csv files and keep track
of which is your primary, secondary and tertiary file
38
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Appendix D
Downloading Solar Radiation Data from the NSRDB
If you are not using solar radiation data files from HELP
model v3.07 or the synthetic weather generation option,
you will need to import historical solar radiation data from
the National Renewable Energy Laboratory's National Solar
Radiation Database (NSRDB) website at
http://rredc.nrel.gov/solar/old data/nsrdb.
The NSRDB contains three different datasets, reflecting
changes data availability and processing methods over
time. HELP v4.0 allows you to download data files from one
or more of these datasets to generate a composite solar radiation input file for simulation. Note that the
program will only accept one data file per calendar year. Where datasets overlap (i.e., for the years 1998-
2010), you should only download the solar radiation data from one NSRDB dataset.
Please use the following steps to select and download solar radiation data files to be imported to the HELP
model:
NSRDB 1961 - 1990 (http://rredc.nrel.gov/solar/old data/nsrdb/1961-1990/)
1. Under Data, click on Hourly Data Files
2. Under Data, click on Compressed Files of All Years for Each Site
3. Find the National Weather Service (NWS) site closest to the landfill and click Download
4. Save the resulting folder and unzip the file
5. Save annual data files that you would like to import in the native .txt format to the directory from
which you will import solar radiation data for the HELP model
NSRDB 1991 - 2010 Update (http://rredc.nrel.gov/solar/old data/nsrdb/1991-2010/)
1. Under the Data section of the screen, beneath Hourly Solar Data and Statistical Summaries, there
is a sub-heading All available solar data and statistical files in compressed site files (gzip
compression*) by:. Click on State and Site Name beneath this heading.
2. The Individual Site-Year Files page will display. Find the National Weather Service (NWS) site
closest to the landfill and click the site ID link.
3. Save the resulting folder and unzip the file
4. Save annual data files that you would like to import in the native .csv format to the directory from
which you will import solar radiation data for the HELP model
NSRDB Compressed Files
NSRDB provides some compressed data
files in a gzip format. Multiple products are
available for opening gzip files. To use
NSRDB compressed files, save the .gz file
to a known directory and use the
instructions provided with the selected
product to unzip/open the files.
39
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NSRDB 1998 - 2014 Update (https://maps.nrel.gov/nsrdb-viewer/)
1. Zoom the NSRDB Data Viewer map to the landfill location
2. Select the Download Data tab at the upper left corner of
the application
3. Select NSRDB Data Download (Point) and click on the
approximate landfill location
4. Enter name, affiliation, data use and email address in the
resulting form
5. In the Data Download Wizard:
a. Click on the PSM v3 tab
b. Under Select Years, select the years of data that you wish to download
NOTE: If you downloaded and wish to use the 1991 - 2010 update, avoid overlapping 1998 - 2010
data by only selecting the year 2011 and years forward.
c. Under Select Attributes, select GHI (at a minimum)
d. Under Select Download Options, make sure that Half Hour Intervals is not selected
6. Select Download Data, after which you will receive a link to your data files in an email from NREL
NSRDB 1998-2014 Update
Data File Attributes
You can select from several
attributes for files downloaded
via the NSRDB Data Viewer.
However, the HELP model will
not use any attributes other
than GHI. Therefore, it is
recommended that you select
only the GHI attribute.
Additional User Note
WARNING: Do not edit the file extensions, format or contents of the data files received from NREL/NSRBD. Doing
so will result in errors in running the model.
40
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Appendix E
Downloading Wind Speed and Relative Humidity Data from the NSRDB
As an alternative to importing wind speed and relative humidity data from an existing HELP v30.7 data file
or entering this information manually, you can import wind speed and relative humidity data from the
NSRDB website at https://nsrdb.nrel.gov/data-sets/archives.html. Here you will find typical
meteorological year (TMY) data sets for the 1991-2005 timeframe, which provide hourly values of
meteorological elements for a typical year for a specific location.
To download wind speed and relative humidity data from this source:
1. Click on the link above and scroll down to the section titled National Solar Radiation Database 1991-
2005
2. Click on the link for Download NSRDB 1991-2005 Archive Data to download the 3 GB file 1020 data
stations and save it your computer, un-compress the archive file and open the newly created 1991-
2005 folder
3. Navigate into the tmy3 folder and open the TMY3_StationsMeta{l).csv file which contains a listing
of the 1020 sites where data has been collected; make a note of the USAF Site ID for the Site Name
and state of interest
4. In the same folder, open the archive file alltmy3a.zip and look for the file that begins with the USAF
Site ID and extract that .csv file from the archive. This file contains the wind speed and relative
humidity data for selected dates and times.
A
DO NOT edit the format or contents of the files received. Doing so will result in errors in running
the model.
41
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Appendix F
Information and Data Sources for Growing Season, Leaf Area Index and
Evaporative Zone Depth
Growing Season
The start of the growing season is based on mean daily temperature and plant species. Typically, the start
of the growing season for grasses is the Julian date (day of the year) when the normal mean daily
temperature rises above 50 to 55 degrees Fahrenheit. The growing season ends when the normal mean
daily temperatures falls below 50 to 55 degrees Fahrenheit. In cooler climates the start and end would be
at lower temperatures and in warmer climates at higher temperatures. In locations where the growing
season extends year-round, the start of the growing season should be reported as day 0 and the end as
day 367.
Maximum Leaf Area Index (LAI)
LAI is the dimensionless ratio of the leaf area of actively transporting vegetation to the nominal surface
area of the land on which the vegetation is growing. The maximum LAI for bare ground is zero. For a poor
stand of grass the LAI could approach 1.0; for a fair stand of grass, 2.0; for a good stand of grass, 3.5; and
for an excellent stand of grass, 5.0. The LAI for dense stands of trees and shrubbery would also approach
5. The model is largely insensitive to values above 5.
If the vegetative species limit plant transpiration (such as succulent plants), the maximum LAI value should
be reduced to a value equivalent of the LAI for a stand of grass that would yield a similar quantity of plant
transpiration. Most landfills would tend to have at best a fair stand of grass and often only a poor stand
of grass because landfills are not designed as ideal support systems for vegetative growth. Surface soils
are commonly shallow and provide little moisture storage for dry periods. See below for appropriate
maximum LAI for the geographical location of your site.
Geographic Distribution of Maximum Leaf Area Index
42
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Evaporative Zone Depth
The evaporative zone depth is the maximum depth from which water may be removed by
evapotranspiration. HELP requires the ET zone depth to be greater than zero and less than or equal to the
depth to the topmost liner. The value specified influences the storage of water near the surface and,
therefore, directly affects the computations for evapotranspiration and runoff. Evaporative zone depth
value depends on site location and soil type. Below are some default values.
Minimum Evaporative Depths
Maximum Evaporative Depths
36
48
39
60
42
42
Geographic Distribution of Minimum Geographic Distribution of
Evaporative Depth (in) Maximum Evaporative Depth (in)
In general, clayey soils would have larger evaporative zone depths since they exert greater capillary
suction; analogously, sandy soils would have smaller evaporative zone depths. Shrubs and trees with tap
roots would have larger evaporative zone depths than the values presented in the figures above. For bare
soil the evaporative depth could be as small as several inches in gravels; in sands the depth may be about
4 to 8 inches, in silts about 8 to 18 inches, and in clays about 12 to 60 inches.
43
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Appendix G
Default Layer Textures and Associated Characteristics
HELP
Texture
No.
Description
General Material
Type
USDA
Texture
Class
uses
Texture
Class
Total
Porosity
(vol/vol)
Field
Capacity
(vol/vol)
Wilting
Point
(vol/vol)
Saturated Hydraulic
Conductivity
(cm/sec)
1
Coarse Sand
Soil - Low Density
CoS
SP
0.417
0.045
0.018
1.00E-02
2
Sand
Soil - Low Density
S
sw
0.437
0.062
0.024
5.80E-03
3
Fine Sand
Soil - Low Density
FS
sw
0.457
0.083
0.033
3.10E-03
4
Loamy Sand
Soil - Low Density
LS
SM
0.437
0.105
0.047
1.70E-03
5
Loamy Fine Sand
Soil - Low Density
LFS
SM
0.457
0.131
0.058
1.00E-03
6
Sandy Loam
Soil - Low Density
SL
SM
0.453
0.190
0.085
7.20E-04
7
Fine Sandy Loam
Soil - Low Density
FSL
SM
0.473
0.222
0.104
5.20E-04
8
Loam
Soil - Low Density
L
ML
0.463
0.232
0.116
3.70E-04
9
Silty Loam
Soil - Low Density
SiL
ML
0.501
0.284
0.135
1.90E-04
10
Sandy Clay Loam
Soil - Low Density
SCL
SC
0.398
0.244
0.136
1.20E-04
11
Clay Loam
Soil - Low Density
CL
CL
0.464
0.310
0.187
6.40E-05
12
Silty Clay Loam
Soil - Low Density
SiCL
CL
0.471
0.342
0.210
4.20E-05
13
Sandy Clay
Soil - Low Density
SC
SC
0.43
0.321
0.221
3.30E-05
14
Silty Clay
Soil - Low Density
SiC
CH
0.479
0.371
0.251
2.50E-05
15
Clay (Low Density)
Soil - Low Density
C
CH
0.475
0.378
0.265
1.70E-05
16
Liner Soil (High)
Soil - High Density
...
0.427
0.418
0.367
1.00E-07
17
Bentonite (High)
Soil - High Density
...
0.75
0.747
0.400
3.00E-09
18
Municipal Solid Waste (MSW) (900
pcy)
Waste
0.671
0.292
0.077
1.00E-03
19
MSW with Channeling
Waste
...
...
0.168
0.073
0.019
1.00E-03
20
Drainage Net (0.5 cm)
Geosynthetic
drainage net
0.850
0.010
0.005
1.00E+01
21
Gravel
Soil - Low Density
G
GP
0.397
0.032
0.013
3.00E-01
44
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HELP
Texture
No.
Description
General Material
Type
USDA
Texture
Class
uses
Texture
Class
Total
Porosity
(vol/vol)
Field
Capacity
(vol/vol)
Wilting
Point
(vol/vol)
Saturated Hydraulic
Conductivity
(cm/sec)
22
Loam (Moderate)
Soil - Moderate
Density
L
ML
0.419
0.307
0.180
1.90E-05
23
Silty Loam(Moderate)
Soil - Moderate
Density
SiL
ML
0.461
0.360
0.203
9.00E-06
24
Sandy Clay Loam (Moderate)
Soil - Moderate
Density
SCL
SC
0.365
0.305
0.202
2.70E-06
25
Clay Loam (Moderate)
Soil - Moderate
Density
CL
CL
0.437
0.373
0.266
3.60E-06
26
Silty Clay Loam (Moderate)
Soil - Moderate
Density
SiCL
CL
0.445
0.393
0.277
1.90E-06
27
Sandy Clay (Moderate)
Soil - Moderate
Density
SC
SC
0.4
0.366
0.288
7.80E-07
28
Silty Clay (Moderate)
Soil - Moderate
Density
SiC
CH
0.452
0.411
0.311
1.20E-06
29
Clay (Moderate)
Soil - Moderate
Density
C
CH
0.451
0.419
0.332
6.80E-07
30
High-Density Electric Plant Coal Fly
Ash
Waste
0.541
0.187
0.047
5.00E-05
31
High-Density Electric Plant Coal
Bottom Ash
Waste
0.578
0.076
0.025
4.10E-03
32
High-Density MSW Fly Ash
Waste
...
0.450
0.116
0.049
1.00E-02
33
High-Density Copper Slag
Waste
...
...
0.375
0.055
0.020
4.10E-02
34
Drainage Net (0.6 cm)
Geosynthetic
drainage net
0.850
0.010
0.005
3.30E+01
35
HDPE Membrane
Geomembrane liner
...
...
2.00E-13
36
LDPE Membrane
Geomembrane liner
...
...
4.00E-13
37
PVC Membrane
Geomembrane liner
...
...
2.00E-11
38
Butyl Rubber Membrane
Geomembrane liner
...
...
1.00E-12
45
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HELP
Texture
No.
Description
General Material
Type
USDA
Texture
Class
uses
Texture
Class
Total
Porosity
(vol/vol)
Field
Capacity
(vol/vol)
Wilting
Point
(vol/vol)
Saturated Hydraulic
Conductivity
(cm/sec)
39
Chlorinated Polyethylene (CPE)
Membrane
Geomembrane liner
4.00E-12
40
Hypalon or Chlorosfulfonated
Polyethylene (CSPE) Membrane
Geomembrane liner
3.00E-12
41
Ethylene-Propylene Diene Monomer
(EPDM) Membrane
Geomembrane liner
2.00E-12
42
Neoprene Membrane
Geomembrane liner
3.00E-12
46
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vvEPA
United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGE & FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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