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Dams Dam is a solid barrier constructed at a suitable location across a river valley to store flowing water. Storage of water is utilized for following objectives: Hydropower Irrigation Water for domestic consumption Drought and flood control For navigational facilities Other additional utilization is to develop fisheries

Structure of Dam:

Structure of Dam Heel Gallery Toe Spillway (inside dam) Crest NWL Normal water level MWL Max. level Free board Sluice way Upstream Down stream

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Heel: contact with the ground on the upstream side Toe: contact on the downstream side Abutment: Sides of the valley on which the structure of the dam rest Galleries: small rooms like structure left within the dam for checking operations. Diversion tunnel: Tunnels are constructed for diverting water before the construction of dam. This helps in keeping the river bed dry. Spillways: It is the arrangement near the top to release the excess water of the reservoir to downstream side Sluice way: An opening in the dam near the ground level, which is used to clear the silt accumulation in the reservoir side.

Construction Standards:

Construction Standards Soils to be used for dam embankment construction must be classified in accordance with ASTMD-2487 (Unified Soils Classification). A minimum of three samples must be classified. Soils acceptable for dam embankment construction are limited to GC, GM, SC, SM, CL or ML. Soils must contain a minimum of 20% of Plus No. 200 sieve materials.

Gradation Sheet:

Gradation Sheet GC- Clayey gravels GM- Silty gravels SC- Clayey sands SM- Silty sands CL- Inorganic clays low to medium plasticity ML- Inorganic silts and fine sand, slight plasticity

Site Preparation:

Site Preparation Foundation of dam embankment must be stripped and grubbed to a depth of two feet prior to any placement & compaction of earthfill. Any springs encountered in the foundation area should be drained to the outside/downstream toe of the embankment with a drain section two foot by two foot in dimension consisting of PennDOT Type A sand, compacted by hand tamper. No geotextiles to be used around sand. The last three feet of this drain at the outside/downstream slope should be AASHTO #8 material.

Dams on a Watercourse:

Dams on a Watercourse Greater than 100 acre drainage area, OR Greater than 15’ maximum depth, OR Greater than 50 acre-feet maximum storage

Drainage area:

Drainage area The drainage area is the total surface area upstream of a point on a stream, where the water from rain or snowmelt which is not absorbed into the ground flows over the ground surface back into the stream to finally reach that point on the stream.

Drainage area:

Drainage area

What the heck is an Acre Foot?:

What the heck is an Acre Foot? A measurement associated with a larger volume, in this case water storage. It is the amount of water required to cover an acre one foot deep. An acre foot is equivalent to 325,851 gallons of water 50 acre feet is equal to 16,292,550 gallons of water


MAXIMUM DEPTH Dmax > 15 ft

The bottom of the Pit or Impoundment must be constructed at least 20” above the seasonal high groundwater table. :

The bottom of the Pit or Impoundment must be constructed at least 20” above the seasonal high groundwater table.

Dams on a Watercourse:

Dams on a Watercourse Greater than 100 acre drainage area OR Greater than 15’ maximum depth OR Greater than 50 acre-feet maximum storage If this is the scenario, then a Dam Safety Permit is required from DEP’s Division of Dam Safety

Dams not on a watercourse :

Dams not on a watercourse Greater than 15’ maximum depth AND Greater than 50 acre-feet maximum storage


TYPES OF DAMS Gravity Dams: These dams are heavy and massive wall-like structures of concrete in which the whole weight acts vertically downwards Reservoir Force As the entire load is transmitted on the small area of foundation, such dams are constructed where rocks are competent and stable.

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Bhakra Dam is the highest Concrete Gravity dam in Asia and Second Highest in the world. Bhakra Dam is across river Sutlej in Himachal Pradesh The construction of this project was started in the year 1948 and was completed in 1963 . It is 740 ft. high above the deepest foundation as straight concrete dam being more than three times the height of Qutab Minar. Length at top 518.16 m (1700 feet); Width at base 190.5 m (625 feet), and at the top is 9.14 m (30 feet) Bhakra Dam is the highest Concrete Gravity dam in Asia and Second Highest in the world.

Buttress Dam::

Buttress Dam: Buttress Dam – Is a gravity dam reinforced by structural supports Buttress - a support that transmits a force from a roof or wall to another supporting structure This type of structure can be considered even if the foundation rocks are little weaker

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These type of dams are concrete or masonry dams which are curved or convex upstream in plan This shape helps to transmit the major part of the water load to the abutments Arch dams are built across narrow, deep river gorges, but now in recent years they have been considered even for little wider valleys. Arch Dams:

Earth Dams::

Earth Dams: They are trapezoidal in shape Earth dams are constructed where the foundation or the underlying material or rocks are weak to support the masonry dam or where the suitable competent rocks are at greater depth. Earthen dams are relatively smaller in height and broad at the base They are mainly built with clay, sand and gravel, hence they are also known as Earth fill dam or Rock fill dam

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EMBANKMENT DAMS Generally have some sort of water proof insides (called the core), which is covered with earth or rock fill. Water will seep in through the earth or rock fill, but should not seep into the core. The water will seep into the core material and should stop at the seepage line. Forces on Embankment Dams: 1. Force of the water (main force) 2. Uplift force

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Wolf Creek Dam, Nashville EMBANKMENT DAMS

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COFFER DAMS temporary structures (sheet-pile, water-tight) that allow construction operations diverts flow from construction areas until work completed

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Hoover Dam • 726.4 feet high .. • 1,244 feet across at the top .. • 660 feet thick at the base .. • 45 feet thick at the top .. • weighs 6.6 millions ton ... • 17 generators giving it the capacity to produce over 2,000 megawatts • can store up 2 years 'average' flow from the Colorado River ... • total storage capacity can be measured in 30,500,000 acre feet ...

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tHanK u !

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