Construction Inspection Servicesforthe Laghar Diversion Dam

Narrative Description of Project

Laghar diversion dam was proposed as part of the Salman Farsi Dam Downstream Reclamation Project. The reclamation project included three main plains downstream to the dam: the Ghir Plain, the Afzar Plain, and the Laghar Plain. Laghar Plain,covering an area of 8250 Hectares, was designed to be irrigated by a gravity water distribution network. The water distribution network initiates from a diversion dam on a reach of the Ghare-Aghaj river. The construction site for Laghar Diversion Dam was thus proposed 10 kilometers south of the Abgarm Village. A water intake from the dam will be laying at the right-hand banks of the stream. Up to 10 cubic meters of water will flow into the distribution network per second, at peak irrigation demands. The basin of the Ghare-Aghaj river is as large as about 13000 square kilometers at the Laghar Dam. Average altitude at this water basin is about 1650 meters. Maximum flood flow rate at the dam in virgin and reclaimed scenarios would be 5000 and 3100 cubic meters per second respectively.

Some characteristics of the river at the dam site include

· Mean slope of the river is about 2 to 1000
· Alluvial river bed consists of sand, gravel and some cobbles
· Main river section is 100 to 150 meters wide
· Flooding section is about 300 meters wide upstream and more than 1000 meters downstream to the dam
· Maximum, minimum, and average mean yearly discharge are 46, 4, and 16 cubic meters per second, respectively
MGCE was in charge for construction inspector consultant and the dam construction is currently accomplished satisfactorily. It is noteworthy to say MGCE had also been also assigned to carry out the prefeasibility and detailed design of the dam.

Description of actual services provided by your staff within the assignment

LagharDiversion Dam construction works included several elements. The following structures and facilities were successfully made under our construction inspection services: · Spillway: an uncontrolled concrete spillway 250 meters wide and 6 meters high was designed to divert up to 10 cubic meters of water per second into the water conveyance canal
· Silt ejector: the ejector is 9 meters long and consists of two radial gates of 2 x 4 meters size
· Still basin: a USBR Type-I with a length of 21 meters
· Intake: the intake is 13 meters wide and consists of three roller gates of 2.5 x 1.5 meters size
· De-silting lagoon: in order to eliminate particles of 0.25 mm and larger in diameter, a de-silting lagoon was designed with a trapezoidal section and with a length of 300 meters. A connecting canal brings water from the dam intake 140 meters down into the de-silting lagoon.
· Connecting canal
· Fish ladder
· Retaining walls
· Marginal embankments and protective dikes
· Vehicle bridge over connecting canal
· Cut-off wall: in order to reduce water seepage and preventing piping within the soil body, and to decrease the uplift pressure on the dam facilities, a cut-off wall is considered with a width of 0.6 meters

Inspected construction activitiesbill of quantities

· Excavation works: 1'100'000 m3
· Fill works: 77'000 m3
· Concrete pouring: 40'000 m3
· Concrete forms: 25'000 m2
· Total reinforcementsteel placed: 1100 tons
· Dry masonry: 32'000 m3
· Hydro-mechanical facilities: 27 facilities built, transported and installed
· Operation and Maintenance buildings: 150 m2