Introduction

The area of the Ruseifa landfill is about 2 km2 and isbetween longitude 248�–250.5�Eand latitude 156�–158�N(Fig. 1). This landfill serves about 2.5 million inhabitantsliving in Amman, Zarqa and the Ruseifa areas. TheRuseifa Landfill receives 2,200 tons/day, more than halfof the solid waste in Jordan. Solid waste is collectedin containers and transported to an intermediatedump station. Ruseifa landfill was placed on the top ofthe Amman–Wadi Sir Aquifer (B2/A7) which is themost important groundwater aquifer in the area. Thisaquifer consists mainly of highly fractured silicifiedlimestone.

The municipal solid waste (MSW) composition inRuseifa landfill is characterized by a high organiccontent, and food waste constitutes almost 53% of

the total waste. Bulk density of the MSW is about0.37 kg/m3, but it was found to be 0.6 kg/m3 in thecollection vehicles after some compaction (UNDP1997). The leachate generated at Ruseifa landfill ischaracterized by high concentration of inorganiccompounds, such as sodium, chloride, etc., andhigh concentration of organic compounds such aschloroform, trichloroethylene and acetic acid (Tadros2000).

Geology of the area

The geological formations outcropping at Ruseifa land-fill are of Upper Cretaceous age, (Masri 1963) belongingto Ajlun and Balqa Groups except for the wadi filldeposits, which are of Quaternary age (Fig. 2). The only

E. Al-Tarazi

A. El-Naqa

M. El-Waheidi

J. Abu Rajab

Electrical geophysical and hydrogeologicalinvestigations of groundwater aquifersin Ruseifa municipal landfill, Jordan

Received: 6 January 2006Accepted: 29 March 2006� Springer-Verlag 2006

Abstract The effect of the Ruseifamunicipal landfill on the shallowgroundwater aquifers in the area wasinvestigated in two separate sites.The first one was not used since1994, whereas the other is still beingused for dumping. Fourteen electri-cal resistivity soundings were per-formed to detect the leachate and itseffect on the quality of the ground-water. Results indicated that thesolid waste thickness of the landfillwas ranged from 3 to 20 m withresistivity value less than 10 W m.Based on the resistivity decreases ofvalues less than 5 W m, the leachatewas detected in the landfill sites atdepths ranged from 10 to 50 m.However, the flow direction of theleachate at depth ranging 10–20 m in

the terminated site was towardnorth, whereas the flow direction ofthe leachate in the site still used fordumping was toward east–northeastwhich causes the major source ofgroundwater pollution.

Keywords Electrical resistivity ÆLandfill pollution ÆHydrogeological Æ Jordan

Environ Geol (2006)DOI 10.1007/s00254-006-0283-4 ORIGINAL ARTICLE

E. Al-Tarazi (&) Æ J. Abu RajabDepartment of Earth and EnvironmentalSciences, Hashemite University,13115 Zarqa, JordanE-mail: ealtarazi@yahoo.comTel.: +962-5-3903333Fax: +962-5-3826823

A. El-NaqaDepartment of Water and Environment,Hashemite University,13115 Zarqa, JordanE-mail: elnaqa@hu.edu.joTel.: +962-5-3903333Fax: +962-5-3826823

M. El-WaheidiP.O. Box 184168, Amman 11118, JordanE-mail: drwaheidi@gmail.com

formation of the Ajlun group that outcrops in the landfillarea is the Wadi Sir Formation (A7), which consistsmainly of hard crystalline dolomitic limestone, chalkylimestone with occasional chert bands and nodules. Thethickness of this formation is 80–100 m and forms a partof the upper aquifer in the Amman–Zarqa Basin (Bender1974). The Balqa Group is represented by the AmmanFormation (B2). The Amman Formation consists oflimestones with chert interbedded with phosphatic layersand marls. It outcrops at the landfill and its surroundingareas and varies in thickness from 80 to 150 m (Howardand Humphreys 1983). The distinguishing feature of thisformation is its undulations and fracturing and jointingof the chert beds. It is subdivided into two units: thelower unit is Silicified limestone and the upper is thePhosphorite unit. The Silicified limestone is characterizedby chert beds. The Phosphorite unit forms part of thePhosphorite belt in which the phosphate horizons weremined in the Ruseifa area. The wadi fill deposits overliethe Amman and Wadi Sir Formations and consist ofsands and gravels with variable thickness from 15 to20 m (Bender 1974). The main structures encountered at

the landfill area are faults related to the Amman–Hall-abat structure, which extends from southwest of Ammantoward the northeast (Mikbel and Zacher 1986).

Electrical resistivity survey

Electrical resistivity methods developed in the early1900s are widely used since 1970s, due primarily to theavailability of computers to process and analyze thedata. These techniques are used extensively in the searchfor suitable groundwater and to monitor types ofgroundwater pollution. The method is also used tolocate subsurface cavities, faults and fissures, permafrostand mineshafts. Resistivity methods have been used tomonitor leachate in many places in the world such as inProvincetown in USA by Froholich et al. (1994) and inPortugal by Matias et al. (1994).

During the period between July 19, 2001 and August22, 2001, 12 vertical electrical sounding (VES) profileswere performed using a Schlumberger array. Twoadditional VESs were measured in the period betweenApril 11 and 4 May 2002 to investigate the area. Inaddition, a Syscal R1 Plus resistivitymeter has been usedto survey the study area. The locations of these VESs areshown in Fig. 1.

Fig. 1 The location of the Ruseifa landfill. The resistivity VESsthat measured at the site are shown and monitoring wells too. Insetmap shows general overview of the study area in Jordan

The Schlumberger configuration was used to detectthe vertical variation in resistivities and, to determine ifthe groundwater was polluted by landfill leachate. Themaximum response depth using the Schlumberger arrayreached about 0.12 of maximum current electrodesseparation (AB).

Interpretation of the resistivity data

The ResixTM (version 3.11) software has been used forinterpretating the resistivity data soundings. This pro-gram is used to interpret resistivity-sounding data interms of a layered earth (1-D) model (Interpex limited1998).

Depending on their locations the 14 VESs wereclassified into four groups (Fig. 1):

Group 1. Outside the landfill (north and northeasternboundary): VESs Nos. 1, 2, 8, 12 and 13.

Group 2. Outside the landfill (south and south westernboundary): Nos. 7 and 14.

Group 3. Inside the recent landfill: VESs Nos. 3, 4, 5and 11.

Group 4. Inside the evacuated landfill: VESs Nos. 6, 9and 10.

Groups 1 and 2: outside the landfill

The depth to water table in the area of VESs 1 and 13 isvery shallow as from monitoring well AL2720 (Fig. 1)located near these VESs. The last layer (the solid line) inthe models of VES1 and VES13 is characterized by rapiddecrease in the resistivity value that ranged between 20and 30 W m. This may indicate highly saturated layerand the presence of the leachate as they are close to theterminated (old landfill, the period between 1987 and1994), see Fig. 1.

The resulted anomaly curves (the dash line) of theVESs that belong to these two groups are shown inFig. 3. The rapid decrease in the resistivity values shown

Fig. 2 The geological map ofthe Amman–Zarqa Basin

Fig. 3 The apparent resistivity–depth models resulted for the 14VESs

in Fig. 3 of these VESs is an indication for the presenceof the leachate at this site. This is supported by thepolluted groundwater samples taken from the nearbyobserved wells (Fig. 1).

Groups 3 and 4: inside the landfills

The resulted resistivity depth models of these two groupsare shown in Fig. 3.

The rapid decrease in the resulted anomaly indicatesthat the dumped solid waste is responsible for thisdecline. The solid waste has resistivity value of 5 W m atthe measured sites. Also it seems that this waste is mixedwith a leachate because the resulted values are too low.

The grossed layered structure of terminated and usedlandfill sites show mainly H-type; the cover layer con-sists of limestone mixed with refuse materials with25 W m average resistivity followed by saturated layer ofrefuse and leachate that reach up to 7 W m (Table 1),except for VES 3 (KA-type) and VES 10 (A-type) whichshow near surface saturated layer. Two pseudosectionswere constructed in order to trace out the tendency ofleachate movements. The pseudosection for terminatedlandfill (Fig. 4a) bound the leachate plume down 20 min depth and about 100 m breadth, it mainly reduce thelateral rock resistivity to the northern direction, whilethe other pseudosection (Fig. 4b) of recent landfillreduce the resistivity of substratum rocks verticallydown to 50 m depth with little effect and small breadthdirected toward the north direction.

Hydrogeological features of the landfill area

The Ruseifa landfill is within the Amman–Zarqa Basin,the most important groundwater basin in Jordan. Theamount of renewable groundwater averages 88 mil-lion m3/year (Salameh and Bannayan 1993). Table 2summarizes the geological and hydrogeological classifi-cation of the rock units in Amman–Zarqa Basin(Rimawi 1985). The two main aquifers in the basinnamely, the Amman–Wadi Sir Formation (B2/A7) andthe Hummar (A4) Formation are both exposed in thebasin. The two aquifers are well jointed, cavernous andexhibit karstic features. The regional groundwater flowin the B2/A7 is influenced by the recharge/dischargeareas, topography and the structural characteristics in

the basin. The main recharge occurs from the south-western side of the area. A part of water flows to thewest increases the level of the springs in the Wadi Sirwest of Amman. The rest of the groundwater flowsnortheastward down the Amman–Zarqa syncline torecharge the upper aquifer and the rest flows into thedesert (Kuisi 1992). Also the groundwater movement ofthe A4 aquifer is from east to west except north ofZerqa, where the flow appears to be north ward(Howard and Humphreys 1983).

The hydrogeology of the landfill area is controlled bythe prevalent geological conditions in the area. Themajor aquifer system in the area is B2/A7, which isknown as the Upper Aquifer. These aquifers are welljointed and fissured and on local scale exhibit solutionchannels and karstic features. It is believed that the twoaquifers are hydraulically connected and in some loca-tions are separated by an aquiclude (i.e., GhudranFormation B1), which consists of chalk, marl and marlylimestone (Table 2). The Amman Formation (B2),which acts as an aquifer, consists mainly of chert andlimestone with phosphate beds. The Wadi Sir Aquiferlies below the Amman Formation and consists mainly ofhighly fractured limestone, dolomitic limestone andsome chert concretions. Most of the groundwater wellssurrounding the landfill are used to extract water fromthese aquifers (Fig. 1).

The groundwater contour map was based on thestatic water levels recorded at different groundwaterwells in the vicinity of the disposal landfill site. Thepresence of the water table underlying landfill has beendetected at a depth of 30 m. VESs 1 and 13 are near wellAL2720 (Fig. 1); VES 12 is near well AL1350; and VESs6, 8, 9 and 10 are near well AL1345 (Fig. 1). Thegroundwater contour map of the B2/A7 aquifer is shownin Fig. 5. In general, the flow direction in the north-eastern part of the landfill area is toward the north andin the southeastern part it is toward the northeast.Moreover, there is some groundwater recharge in thesouthern part of the study area.

The aquifer hydraulic parameters were obtained byanalyzing the pumping test data of some groundwaterwells in the vicinity of the landfill site such as wastedisposal monitoring well (AL2720); phosphate mineNo. 7 (AL1345); and phosphate mine No. 10 (AL1350)see Fig. 1 for their locations. The pumping test datawere analyzed using GWW software (Braticevic andKaranjac 1997) with different techniques to derive the

Table 1 Distribution of the resulted anomaly curves measured at Ruseifa landfill depending on the standard curves (Reynolds 1997)

Q-type A-type K-type H-type AH-type AQ-type KA-type

VES1 VES10 VES2 VES4, VES5VES6,VES8VES9, VES11

VES12,VES13VES14

VES7 VES3

See Fig. 1 for VES locations

hydraulic parameters of the aquifer such as Theis, Ja-cob and Hantush methods (Fetter 2001). The pumping

test of waste disposal monitoring well (AL 2720) hasbeen carried out in the period from 4–7August 2003,which indicated that the discharge of the well was52.2 m3/h with drawdown of 1.63 m.

Fig. 4 Two apparent resistivity pseudosections of the landfill.a For the terminated site, b for the recent site

Table 2 Geological and hydrogeological classification of the rock units in Amman–Zarqa Area (modified after Rimawi 1985)

Epoch Age Group Formation Symbol Rock type Thickness(m)

Aquiferpotentiality

Permeability(m/s)

Tertiary Holocene Balqa Wadi Fill Al Soil, sandand gravel

10–40 Good 2.4 · 10 )7

Pleistocene Basalt V Basalt,clay

0–50 Good –

UpperCretaceous

Maestrichtain Muwaqqar B3 Chalk, marland chalkylimestone

60–70 Poor –

Campanian Amman B2 Chert, limestonewith phosphate

80–120 Excellent 1 · 10 –5–3 · 10)4

Santonian Ghudran B1 Chalk, marland marly limestone

15–20 Poor –

Turonian Ajlun Wadi Sir A7 Hard crystallinelimestone. Dolomiticand some chert

90–110 Excellent 1 · 10)7–1 · 10)4

The transmissivity (T) values of the (B2/A7) aquifersystem ranged from 33.9 to 409 m2/day. The valuesof chydraulic conductivity (K) ranged from 0.38 to5.18 m/day.

The hydraulic gradient of the landfill area was calcu-lated to be equal to 2.0 · 10)3. Based on three ground-water-monitoring wells exist within the landfill, where dh/dl represents the change in headbetween twowells that arevery close together and dl is the small distance betweenthese wells. Considering a hydraulic conductivity of theaquifer k = 6 · 10)5 m/s and dh/dl = 2 · 10)3, the

darcian velocity = K dh/dl = 1.19 · 10)7 m/s. To findthe velocity atwhichwater is actuallymoving, theDarcianvelocity is divided by the effective porosity. In this case,considering a porosity value of the aquifer of 0.35,therefore, the true velocity will be 3.4 · 10)7 m/s. Thegroundwater velocity is 1 · 10)7 m/s. To determine howfast the leachate can reach the groundwater, some soilsamples were collected from the top and the base of therecent landfill. The grain size analysis of the landfill soilsamples shows 35% gravels, 40% of sand, 11.5% of siltand 14% of clay. The soil permeability was estimated

Fig. 5 The upper part showsgroundwater contour map ofthe B2/A7 aquifer at Ruseifalandfill. The lower part showsthe groundwater level deter-mined at different wells

based on the grain size analysis and usingHazen empiricalformula. The average value of soil permeability is3.3 · 10)7 m/s. Based on the permeability value of thesoil, the leachate will reach the water table which isapproximately at a depth of 30 m, after approximately10 years. This is confirmed by the geophysical results (seeFig. 4b).

Discussions and conclusion

Depending on the above results it is clear that the VESsperformed in the landfill area have detected differentsegments and layers in the subsurface of the sites studiedin the area. To give clearer reason for the detected layersand to make it easier to discuss the leachate penetrationand its effect on the aquifers in the studied sites, 2-Dspatial distribution is used to describe the resistivity valuevariations as a function of depth. In the first 30 m depth acontour sheet is produced each 10 m (i.e., for depths 10, 20and 30 m). The results are illustrated in Fig. 6. Twomajortrends of low resistant materials are detected at depth10 m. The first is in the northern direction where theanomalies decrease to less than 5 W mand the second is inthe northeastern direction of the same resistivity value.Both low resistant anomalies detected at depth 10 mwerealso noticed at depth 20 m. It is very clear that for these

depths, the leachate plume became wider and thicker,because of the rapid decrease in the resistivity values (nearto 1 W m) that are noticed at both depths. By comparingthe locations of the terminated landfill and the recent onewith the detected plumes, it is clear that the first plume thatwas directed in the northern direction resulted from theterminated landfill, while the second that was directed inthe northeastern direction resulted from the recently usedone. For the 30 m depth, the first leachate that trendstoward the north has changed its direction toward thesouthwest. The second plume that was directed towardnortheast has kept its direction towards the northeast as inthe above depths (Fig. 6).

It is obvious from leachate spatial distributionthrough depth levels 10, 20, 30 m that the terminatedlandfill is not able to supply leachate under depth morethan 20 m. The base of the landfill is paved by a well-compacted clay blanket, which may prevent seepage outof the landfill base body, but most of the leachate wastrapped in the dumped wastes and moved up ward dueto load pressure. This led to the formation of somebatches of leachate observed at the site. The pollutiondetected at well AL1345 may seep into the groundwaterfrom the northern bank of the landfill, as the rock of thisbank is highly fissured and folded (see Fig. 6).

On the other hand, the plume of recently used landfillhas an immense potential to pollute the groundwater; itwill gain access to groundwater by the relatively highhydraulic conductivity (10)5 m/s) and transmissivityvalues that range from 34 to 409 m2/day as calculatedabove. The leachate plume became wider in the east–west direction till 30 m depth; the movement of plume iscontrolled by the shallow groundwater flow (Fig. 4b).This increases the susceptibility of contamination ofgroundwater of the Ruseifa landfill, (see Figs. 5, 6).

The hydrological investigations of monitoring wellsinstalled at the landfill area and around show that theleachate of solid wastes has highly contaminated B2aquifer and slightly effected A7 aquifer. On the otherhand, the flow direction of the leachate plume at thelandfill is controlled by the groundwater movement,which is toward the north at the terminated landfill siteand toward the east–northeast at the recent site.

Acknowledgements This paper is part of a research funded by theHigher Council of Science and Technology (HCST) in Jordan. Theauthors express great gratitude for the HCST. Many thanks for theHashemite University for offering support during the geophysicaland hydrogeological measurements.

Fig. 6 The distribution of resistivity anomaly values (less than5 W m) as a function of depth at the studied site

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