Geotechnical questions associated with various geological environments - Geotechnical Engineering of Dams - page 116

Table 3.3. Dams at which very high leakage rates were recorded (Based on Erguvanli, 1979; Riemer

et al., 1997; Salembier et al., 1998).

Maximum recorded

leakage (m 3 /s) Dam Country Rock

Hales Bar USA Carboniferous limestone and shale 54

Keban Turkey Palaeozoic limestone 26

Lar Iran Mesozoic limestone, volcanics, lake deposits 16

Attaturk Turkey Palaeozoic limestones, folded and faulted 14

Great Falls USA Limestone 13

Camarasa Spain Jurassic dolomitic limestone 12

Dokan Iraq Cretaceous dolomitic limestone 4 to 5

Fodda Morroco Jurassic limestone 3 to 5

Table 3.4. Dams which failed to store water (Erguvanli 1979).

Dam Country Rock

Civitella Liciana Italy Cretaceous limestone

Cuber Spain -

Kopili India Eocene limestone*

May Turkey Mesozoic and Tertiary limestone *

Montejagne Spain Mesozoic and Tertiary limestone*

Perdikas Greece Miocene limestone*

Villette Berra Italy -

* Geologically young carbonate rock ( Category Y ) present.

are governed mainly by reservoir level. The (1997) total discharge is estimated as
11-14 m 3 /sec, with reservoir levels ranging from 6-8 m below FSL. These losses are tolerable,
as the average flow of the impounded river is 850 m 3 /sec. The monitoring also shows some
high piezometric levels downstream from the curtain and some decrease in head upstream of
it. Riemer et al. (1997) point out that these results “could hint at” ongoing erosion, either
of grout or clayey infilling and they foreshadow the possible need for further grouting
and/or drainage works.
Lar Dam . This is an earthfill embankment dam, 110 m high and 1100 m long, across
the valley of the Lar River in Iran. Djalaly (1988) and Salembier et al. (1998) summarise
the site geology and describe difficulties met since completion of the dam construction in
1980. Uromeihy (2000) provides more detail on the geology. The site is at the foot of an
active volcano. Bedrock in the area is complexly folded, faulted and karstic limestones
and mudrocks of Mesozoic Age. The dam and 15 km long reservoir area are located
partly on these rocks and partly on near-horizontal materials of Quaternary Age. These
include lava, ash, alluvial and lake deposits (mainly sandy and silty). They fill an old val-
ley, which is around 200 m deep at the dam site and up to 600 m deep in the reservoir
area. Before construction there were several large sinkholes (up to 25 m across and 30 m
deep) in the alluvial/lake deposits in the reservoir area. The water table in the dam area
was more than 200 m below the river bed and there was a karstic spring 10 km down-
stream from the dam, flowing at about 0.5 m 3 /sec.
Uromeihy (2000) notes that outgassing CO 2 and H 2 S from hot springs flanking the vol-
cano would increase the acidity of the streams draining into the reservoir but provides no
data on the chemistry of the reservoir water.
After impoundment started in 1981, large new sinkholes appeared in alluvium. These
were exposed when the lake was drawn down and many depressions in the lake floor