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THE HYDROLOGICAL EVALUATION OF LANDFILL PERFORMANCE (HELP) MODEL ASSESSMENT OF THE GEOLOGY
INTRODUCTION
Purpose:
-Conduct HELP model variations in weather
data, profile characteristics, and hydraulic
conductivities for major rock units
-Compare and contrast the results of
simulations
*Obtain an estimation of leakage through the
landfill from the surface to the aquifer
'Evaluate contaminant transport to the aquifer
utilizing leakage estimation'Helps
waste
'Requrr
dosur
-As
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'Aids in
periodAT LOS ALAMOS NATIONAL LABORATORY, TECHNICAL AREA 54, MATERIAL DISPOSAL AREA J
L.ciama R. Vigil-Holternan
Jennifer Lindlin wexcoigland innersty
- - ' Located on north
Significance: Technical Area 54
assess risk to the general public from - figures 1 &
- t - Historically used
ed by regulators in planning and - - - r r - Main aquifer depth
e of iandf'lls -- Ma"n ---ATeradems
well as other operations that could "'-- 'Grudatf
rentially contaminate groundwater '""""''""""" Gudatrfo
Groundwaterthe determination o monitoring Gundwater age:
t his 2000)site:
west part of Mesita del Buey, Los Alamos National Laboratory,
Material Disposal AreaJ (MDA-J)
2
o dispose of nonhazardous, administratively controlled wastes
: 330 i at the western end and 259 w at the eastern end of
- eastward towards Rio Grande, 7.2 km away from site (Figure 3)
'4C data indicates groundwater is 6k -10 k years old (Keating,THE HELP MODEL
Why the HELP Model?
'Designed to assess landfill performance
-Capable of estimating the magnitude of various fluid
components
-The volume of leadrat produced
-The thickness of water-saturated sod above any linen
emplaced within the landfillClimatic Infonmation:
-Evapotranspiration
- Evaporative zone depth and average wind
speed
- Maximum leaf area index and growing season
dates
-Weather
- Precipitation, temperature, and solar radiation
dataDATA REQUIREMENTS
Soil and Landfill Design: Weather Generator:
'Landfill general information *Temperature and precipitation
-Area, slope, and rate of subsurface inflow - User may enter from 1-100 years worth of
.Layer and layout design information monthly mean temperature and precipitation
- Layering beneath surface (Figure 4) - r data
'Soil properties and thickness associated with -Calculated from the temperature and
precipitation values
-Engineering controlsAssumptions:
'Does not take into account extensive fracture system at
research site
'Assumes that runoff does not occur from surrounding
areas onto the landfill
'Does not consider rainfall intensity
'Assumes that vegetative growth and decay can be
characterized using a model developed for crops and
perennial grasses
'Does not consider aging of profileRESULTS
Trial Descriptions:
'Trial 1
- Weather Generator was used to obtain data for
Albuquerque, NM for 8 years
-Trial 2
- Weather Generator was used to obtain data for
Albuquerque, NM for 100 years
'Trial 3
- Database within the Weather Generator was edited to
iclude site-specific average monthly values
-Trial 4
- Files generated by Weather Generator were replaced
with formatted files containing site-specific
precipitation and weather data for 8 years
'Trial 5- Basalt layer within the profile was modeled as a barrier
soil liner instead of a vertical percolation layer as in
other trials -L
-Trial 6 - , , ,
- Maximum hydraulic conductivity values for 4 profile "
layers were used
'Trial7 ,'. '--
- Minimum hydraulic conductivity values for4 profile
layers were usedTrial Results:
'Values for Trial 1 & the first 8 years of Trial 2 were
identical
'Values for Trials 1 & 3 were almost identical
- -Precipitation, evapotranspiration, runoff, and leakage
rates varied little among Trials 1, 2, & 3
- Average leakage rates for Trial 1 was 2.65E-9 m/d,
for Trial 2 was 1.25E-8, and Trial 3 was 1.27E-8
' Precipitation, evapotranspiration, runoff, and leakage
rates were higher for Trial 4 (Figure 5)
- Average leakage rate for Trial 4 was 1.51 E-6 m/d
'Trial 5 showed overall greater leakage rates than Trial 4
(Figure 6)
' Barrier soil within the HELP model is modeled as alays
saturated, whereas vertical percolation layer saturation
begins at zero
-Trial 6 displayed higher leakage rates in the beginning
and became progressively lower as simulation continued
(igure 7)
-Trial 7 showed lower leakage rates in the beginning and
became progressively higher as simulation continued
(Figure 7)
' Hydraulic head building on top of the layer within Trial 7
and less of this occurrence in Trial 6- - --- - - __ ._ .
- - - --
1-
-- -Statistics:
' Coefficient of correlation was conducted on chosen
weather data related combinations
-Trial 4 showed little correlation with Trials 1 or 3
-Trial 1 showed high correlation with Trial 3 and the
first eight-years of Trial 2
" Histograms were developed for weather data related
trials
- Indicated that only Trial 4 was significantly different
from the other three trials
' Sensitivity analysis was conducted on trials that changed
model parameters (Figure 8)
-When model parameters are increased, the percent
change in leakage rate is only about 10%
-When the change in the model parameter is negative,
the percent change in leakage is higher, reaching
almost 100%Contaminant Transport
'Soil sampling at the site revealed the presence of lead
(0.20 mg/U and barium (1.2 mg/U in concentrations
below regulatory limits (Dye, 2001)
-The amount of leachate that wouid reach the aquifer
in 30 years would be 5.8 m3 for one pit
-Assuming no speciation, Trial 4 average leakage rates,
and an aquifer of I m thick, concentration of lead
would be 3.31 E-3 mg/L
-Drinking water limit for lead is 15 ppb
-Unrealistic estimate but illustrates that leachate
transport is minor
Conclusions:
' The HELP Model is useful to assess landfill design
alternatives or the performance of a pre-existing
landfill
" Model results using site-spedfic data incorporated
into the Weather Generator (Trail 4), varied
significantly from generalized runs (Trials 1-3)
- consequently, models that lack site-specific data
should be used cautiously
'Data from this study suggest that there will not be
significant downward percolation of leachate from
the surface of the landfill cap to the aquifer -leachate
transport rates have been calculated to be slowREFERENCES ACKNOWLEDGEMENTS
Uy-. Alcr., raf report 0, 0thAj so r s and anelysas r oans'ATA-54. Ata J ui-of hz AralundfiR-FSM-19, Nar d dSnld War Cup, los AdrE NZl001.ssr Lciaa, i Ah-,or r' FSs-01-0Thes 200!. Ta ns0 cc.,aae*0OI00m,, or,00,h chndu0e0d at NSYeImh 1Hgh10ds Uisivy
v-19. "Dmn,, tion for sus n nqu et eatndse one m'Eid- rn0 pln TA-54, Asaj Iazdous nd Soa muste GrwR la Aam s Natmi l aboramn, bs Mans, NM: 199 . Thas to o ALiamos Natnaoora y & Ne Mexo a Hghndsd Und erty fr pmaEdi,5g fn-, l sstnc, ad trchnical rapport fnr thisork
KeCmg. Ei0be[h. Ed Kwikis. 5r Vassein, Ap lr. Zhimwo I. asp ZyWoI,-. 4 Mi vOOskt sA ,gi "d s r0 .ad baspor[de r9.d -terat Anos Neael lahbonary." Snnubedto FplmOe9bgi Clcesiatin Program PAogiss RRrt,. LosAMos National Twtraimismwivg,}Hdtn's Ts cmmie dfor 5Heir adsreLoemOgh t5hec0rs-of eh-resuo!
Laboraty, lA A,,s. Nu: LA-UR-01-2199, 2000.
Paw . Stsven L. David 0. oitas 0'h sn. ry, a r ed c aMf, La up. c u' t Tshirege Membero t ander Tufat Mesina deury, ThlaAa 54, LsAaos Naati!l laberamy. LasO A ,m, Nafo,0 Laborasr, Los ALam, NM IA-13538-AM0. 0C-2t00,1996.- -
*
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Synchrotron-based high-pressure research in materials science, article, Date Unknown; [Los Alamos, New Mexico]. (https://digital.library.unt.edu/ark:/67531/metadc926642/m1/2/: accessed March 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.