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85 GEO-ECO-MARINA 16/2010

IntroductIon

Over the years, the water supply o Constana Harbor has

been totally dependent o the water supply o Constana city.

The increase o the drinking water delivery price made the

Constana Harbor Administration evaluate alternatives or

drinking water supply rom groundwater sources.

All the investigations carried out by now in South Dobro-

gea were made on land. The marine domain located in the

proximity o the coast wasnt investigated, the danger o con-

tamination with salty marine water being raised by skeptics.

The aquier potential in the Constana Harbor is evaluat-ed or the rst time in this paper, based on geological, struc-

tural and hydrogeological data. That is why this approach is

a challenge.

1. MaterIals and Methods

Preliminary hydrogeological studies and technical re-

ports or water supply or some industrial or private objec-

tives located in the Constana area (Fig. 1), were analyzed.

Field investigations were also carried out, in order to

achieve additional data concerning water sources.

2. MaIn geographIc features

The Constana Harbor domain has been acquired arti-

cially rom the sea, by civil engineering works, such as dams

and llings. It extends rom the Cape Constana (Gate 1) to

Agigea. Its western boundary ollows the base o the ma-

rine cli, previously modeled by the marine hydrodynamic

regime, but also bearing the damaging eects o landslides

and erosions.

The average elevation is 60 to 70 m, increasing to 80 90

m south o the Albeti Valley. The Constana Harbor, as coastal

zone, belongs to the category o erosion coast lines, with cli,

taken out o the direct infuence o the marine hydrodynamicregime, by civil engineering works.

The climate is typically continental, with the sea infuence

upon a 10 to 15 km wide littoral strip. The average multi-an-

nual temperature is 11.2 oC. The precipitations are low and

unevenly distributed during the year, not exceeding 400 mm/

year.

3. regIonal geologIcal fraMework

The Constana Harbor and the South Constana Agigea

area are comprised in the South Dobrogea platorm, bound-

Possibility of extending the drinking watersuPPly for the Constana harbor

Glicherie cArAiVAN(1), iriNA DiNU(2), coNstANtiNA FUlGA(1), VlAD rADU(3)

(1)National Institute for Marine Geology and Geoecology - GeoEcoMar Constana, 304 Mamaia Blvd, 900581, Constana, Romania(2)National Institute for Marine Geology and Geoecology - GeoEcoMar Bucharest, 23 2 5 Dimitrie Onciul, 024053 Bucharest 2, Romania

(3)National Institute for Land Reclamation ISPIF Bucharest, 35 37 O lteniei Rd, 024053 Bucharest 4, Romania

e-mail: [email protected], [email protected], [email protected]

Abstract. The Constana Harbor is located along three struc tural blocks: Constana, South Constana and Eorie - Techirghiol, with dierent hydrogeologicalcharacteristics. This paper presents the main sources or drinking water supply o the Constana Harbor. A new abstraction well was proposed and installed,to intercept the Upper Jurassic Lower Cretaceous confned aquier, in the proximity o the Cernavod - Constana Fault, in the marine area o the ConstanaHarbor platorm.

Key words: aquier, Constanta Harbor, tectonic block, abstraction well


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Glicherie Caraivan, Irina Dinu, Constantina Fulga, Vlad Radu Possibility of extending the drinking water supply for the Constana Harbor

Fig. 2 Sketch o the ault systems and tectonic blocks o South Dobrogea in the study area with the wells used or the cross-sections rom Figs. 3-5;

similar codes or tectonic blocks as used by Moldoveanu, 1998

Fig. 3 WNW-ESE cross-section (see Fig. 2)


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89GEO-ECO-MARINA 16/2010


Thus, both rom the quantitative and qualitative points oview, this aquier is not appropriate as drinking water source.

5.1. he armatian aquifer

In the area o Constana city, the medium depth aquier in

altered and karstied Sarmatian limestones, is locally covered

by bentonitic clay. The thickness o the Sarmatian deposits

varies between 2 and 68 m, in the zone o Constana city, in-

creasing southward, up to 180 m.

The Sarmatian aquier is not continuous in the study area.

Groundwater fow in the Sarmatian limestones is mixed. The

aquier is locally unconned, in the zones where it is covered

by silty loess deposits, or locally conned, in zones where it iscovered by clayey loess deposits (Moldoveanu, 1998).

At regional scale, the Sarmatian aquier is supplied rom

precipitation on the Bulgarian territory, where the whole

structure is outcropping at higher elevations. Beore the

1990s, an irrigation system was also in unction and aerent

losses were increasing the recharge. Starting rom 1990, the

irrigations were gradually reduced and nowadays they are

not used anymore.

The Sarmatian aquier discharges to the east (Fig. 8), to

the Black Sea, and to the Danube Black Sea canal, which in-

Fig. 4 WSW-ENE cross-section (see Fig. 2), emphasizing the block without Upper Jurassic deposits

Fig. 5 Regional N-S cross-section (see Fig.2), parallel to the coast line


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tercepts the Sarmatian ormations on the last 5 - 6 km, beore

reaching the Black Sea. The aquier also discharges by down-ward leakage, to the conned Upper Jurassic Lower Creta-

ceous aquier, except or the coastal zone, where the leakage

is upward, due to the head dierence.

There are abstraction wellelds in the Sarmatian aquier

in the littoral zone and towards the border with Bulgaria.

The transmissivity o the Sarmatian aquier determined

rom pumping tests varies between 50 and 3500 m2/day

(Moldoveanu, 1998).

In the Constana Harbor area, the Sarmatian aquier was

intercepted by 100 to 155 m deep wells, such as F9, F11 and

F12. The aquier is intercepted up to 60 65 m deep. It is con-ned when covered by bentonitic clay and unconned when

the bentonitic clay is missing.

The water table in the abstraction wells rom the Sar-

matian aquier is, usually, mainly ascending, with stabilized

depths between 34.5 and 36 m. The pumping rates at the

installation are between 3.33 l/s (F12) and 6.25 l/s (F11) and

the optimal exploitable rates are between 3.64 l/s and 7.84 l/s

or a well, the estimated average hydraulic conductivities are

between 3.48 m/day and 6.90 m/day, corresponding to 16 to

30 m thick total screened intervals.

From the qualitative point o view, groundwater rom the

Sarmatian aquier, rom 100 to 155 m deep abstraction wells,exceeds the standard or nitrate content (80 mg/l) and or l-

trate residual (over 2000 mg/l). The bacteriological analyses

show that the abstraction wells in the industrial zone exceed

considerably the standard or total coliorms and ecal coli-

orms. We also appreciate that in the Harbor zone, the Sar-

matian aquier might be polluted by petroleum products. For

this reason, the drinking water supply o the Constana Har-

bor shouldnt be provided by the Sarmatian aquier.

5.2. he pper Jurassic ower Cretaceous aquifer

complex

The Upper Jurassic Lower Cretaceous aquier complex,

located in the limestone and dolomite deposits aected by

the regional WNW ESE and NNE SSW ault systems men-

tioned above (Fig. 2), is generally conned. The aquier can

become locally unconned in the western and northern parts

o South Dobrogea, where the Lower Cretaceous deposits

crop out (Moldoveanu, 1998). In the southern and eastern

parts o South Dobrogea, the deep aquier complex is sepa-

rated rom the Sarmatian aquier by the Senonian aquitard

consisting mainly o chalk and marl.

The natural boundary o the Upper Jurassic Lower Cre-

taceous aquier is the Capidava Ovidiu Fault. In the north-

Fig. 6 N-S hydrogeological cross-section (see Fig. 1) through Constana city


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Fig. 7 WSW-ENE hydrogeological cross-section (see Fig. 1) through Constana city


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ern compartment o the ault, the Upper Jurassic have low

thickness and are overlapped on the Green Schists Forma-

tion, with high elevations and low permeability, that make

a barrier or the groundwater fow, deviating it towards east

(Zamrescu et al., 1994). Thus, the Capidava Ovidiu Fault is

considered an impervious boundary.

The thickness o the Upper Jurassic Lower Cretaceous

deposits varies between 200 m and more than 1000 m in the

northern part. The aquier geometry is emphasized in Figs.

3-5.

The piezometric heads (Fig. 9) show that the Upper Ju-

rassic Lower Cretaceous aquier is supplied rom the Bul-

garian territory, where the Upper Jurassic deposits crop out

(Zamrescu et al., 2005). The aquier discharges to the east, to

the Black Sea, and also to northeast, in the Lake Siutghiol. The

aquier is also supplied by downward leakage rom the Sar-

matian aquier or, in the western part o South Dobrogea, by

eective inltration rom precipitation. Along the coast, thepiezometric heads o the Upper Jurassic Lower Cretaceous

aquier are higher than the ones o the Sarmation aquier, so

there is an upward leakage.

The transmissivity o the Upper Jurassic Lower Creta-

ceous aquier determined rom pumping tests varies be-

tween 10 and 200000 m2/day (Moldoveanu, 1998).

The most important abstraction wellelds in the Upper

Jurassic Lower Cretaceous aquier are located in the area

o Constana city. There are also abstraction wellelds in the

area o Medgidia city.

This aquier has been intercepted by means o several

wells in the study area, at depths between 57 and 103 m in

the tectonic block 5 (F3, F6, F13), at depths around 200 m in

the tectonic block 10 (F1, F2, F4, F5) and at depths around

300 m in the tectonic block 13 (F10, F14). The exploitable

potential o this karstied aquier complex is expressed by

the diering exploitable rates in the wells mentioned above,

refecting the anisotropic character o the ssuring porosity.

Thus, the abstraction rates at the installation o the wells

are around 22 l/s in the tectonic block 5, around 7.5 l/s in the

tectonic block 10 and around 6.6 l/s in the tectonic block 13.

The optimum abstraction rates vary between 5.5 and 267.3

l/s, while the average hydraulic conductivities vary between

1.84 and 332.73 m/day, corresponding to the screened inter-

vals with total thicknesses between 109 and 154 m.

The water rom the Upper Jurassic Lower Cretaceous aq-

uier meets the Romanian drinking water standard (Caraivan,

2006). The groundwater quality and the abstraction rates in-

dicate that this aquier should be used or the drinking water

supply o the Constana Harbor.

6. new well

Taking into account the geological structure, the hy-

drogeological conditions and the restrictions generated

by the accessibility o the drilling equipments, a irst in-

vestigation and abstraction well, marked by FP (Fig. 1),

was drilled and completed within the Harbor area, close

to Gate 5. The technical characteristics o the new well are

shown in Fig. 10. This well is sited on the prolongation o

Fig. 8 Piezometric map o the Sarmatian aquier in the study area (Moldoveanu, 1998 with modifcations)


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Fig. 9 Piezometric map o the Upper Jurassic Lower Cretaceous aquier complex in the study area (Moldoveanu, 1998 with modifcations)

Fig. 10 Sketch o the proposed and implemented construction o the FP well


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the Cernavod Constana Fault to the marine domain,

supposedly a zone with maximum issuring. Technical re-

strictions, such as high voltage networks or buried pipe-

lines have been taken into account when choosing the

location o this well.

The drilling works have been designed or an investiga-tion depth o 220 m. The well has been located at the limit

between blocks coded 10 and 5 and taps the Upper Jurassic

Lower Cretaceous aquier. The aquier is protected by the

potential anthropic stress by an aquitard, consisting o Seno-

nian chalk and marl. The depth o the open hole interval is

183 212 m and the depth o the piezometric head is 3 m.

The hydraulic conductivity is 6.5 m/day and the optimal ab-

straction rate is 6.92 l/s. The radius o infuence o the well is

203 m. There is no intererence between the new well and the

other wells (Caraivan, 2006).

The chosen location meets the requested conditions or

sanitary protection. Groundwater is o drinking quality, with atotal hardness o 18.625 German degrees. In order to improve

the groundwater quality, the water well system also includes

a UV lter.

The Beneciary is requested to monitor the abstraction rate,

the piezometric head and the groundwater quality o the well.

conclusIons

A brie review o the geological ramework and o the

drinking water sources is presented in this paper. Basedon the hydrogeological and technical conditions, a new in-

vestigation and abstraction well has been installed in the

Constana Harbor zone, opening the Upper Jurassic Lower

Cretaceous aquier. This one is more appropriate to be used

or the drinking water supply.

This study emphasizes the hydrogeological potential, es-

pecially in the zone adjacent to the tectonic blocks 5 and 10,

where the Senonian aquitard ensures the protection o the

conned aquier.

acknowledgMents

We thank Pro. Corneliu Dinu or more recent inormationconcerning the geological ramework. Also many thanks to

the reviewers, Dr. Adrian Iurkiewicz and Dr. Petru Enciu, or

their useul observations and suggestions.

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