Water Wrangling: Restoring and Rejuvenating Hydraulic Excellence in Siem Reap

May 12, 2005

ENGR340

Team 15 Monsoon Platoon

Ben Giudice, Kevin Gritters, Dan Vander Heide

© 2005, Calvin College and Ben Giudice, Kevin Gritters, and Dan Vander Heide

I. EXECUTIVE SUMMARY................................................................................................................................3 II. INTRODUCTION/OVERVIEW ......................................................................................................................4

A. GENERAL .........................................................................................................................................................4 B. HYDRAULIC HISTORY ......................................................................................................................................5

1. History of the Siem Reap River...................................................................................................................5 2. History of Barays........................................................................................................................................6 3. History of Mountain Dams .........................................................................................................................7

III. CHALLENGE ...............................................................................................................................................8 A. GENERAL .........................................................................................................................................................8 B. DESIGN NORMS..............................................................................................................................................10

1. Cultural Appropriateness .........................................................................................................................10 2. Transparency............................................................................................................................................10 3. Integrity ....................................................................................................................................................10 4. Stewardship ..............................................................................................................................................11 5. Justice.......................................................................................................................................................11 6. Caring.......................................................................................................................................................11 7. Trust..........................................................................................................................................................11

IV. SOLUTION..................................................................................................................................................12 A. CHANNEL AND RIVER ....................................................................................................................................12

1. Purpose.....................................................................................................................................................12 2. Site ............................................................................................................................................................12 3. Social and Environmental Considerations ...............................................................................................14 4. Hydrology.................................................................................................................................................14 5. Design.......................................................................................................................................................15 6. Safety ........................................................................................................................................................25 7. Cost Analysis ............................................................................................................................................25

B. RESTORATION OF THE EAST BARAY...............................................................................................................27 1. Purpose.....................................................................................................................................................27 2. Site ............................................................................................................................................................27 3. Social and Environmental Considerations ...............................................................................................29 4. Hydrology.................................................................................................................................................29 5. Design.......................................................................................................................................................30 6. Safety ........................................................................................................................................................49 7. Cost Analysis ............................................................................................................................................50

C. MOUNTAIN DAM............................................................................................................................................52 1. Purpose.....................................................................................................................................................52 2. Site ............................................................................................................................................................52 3. Social and Environmental Considerations ...............................................................................................53 4. Hydrology.................................................................................................................................................55 5. Design.......................................................................................................................................................58 6. Safety ........................................................................................................................................................67 7. Cost Analysis ............................................................................................................................................68

V. DISCUSSION ...................................................................................................................................................69 A. COORDINATION BETWEEN MOUNTAIN DAM AND EAST BARAY ......................................................................69

1. Necessity of baray and dam......................................................................................................................69 2. Controls ....................................................................................................................................................70

B. CONCLUSIONS................................................................................................................................................71 VI. RECOMMENDATIONS ............................................................................................................................72 VI. ACKNOWLEDGEMENTS................................................................................................................................73 APPENDIX ................................................................................................................................................................74

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I. Executive Summary

Increasing tourism surrounding the Angkor temple sites in Siem Reap, Cambodia has spurred

development which requires advanced water resources management. The goal of our project was

to construct a canal with a constant water level that would connect the city of Siem Reap to Lake

Tonle Sap to allow for water transport. In order to maintain that constant water level, the

restoration of the East Baray and construction of a dam in the Kulen Mountains to the north

would provide water storage from the wet season for use in the dry season. While the total

project cost if done in the United States is $240 million, the cost if done in Cambodia may be

significantly less, and there would be many benefits to the people of Siem Reap for many years

to come.

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II. Introduction/Overview

A. General

In the 1970’s, a large portion of Cambodia was devastated by the Khmer Rouge. As a result,

there is almost a complete generation missing, and much of the infrastructure is in poor shape.

Recently, in the area around Siem Reap, tourism associated with the ancient temples and

monuments of the Angkor Empire has spurred development (see Figure APP – D.1). Professor

Hackchul Kim of Handong Global University has come up with a master plan to assist in the

proper development of the region, shown in Figure APP – D.2.

The plan includes water resources developments, specifically, a new canal connecting the city

and Lake Tonle Sap to the south and the restoration of part of the East Baray.

The goal of our project was to construct a canal with a constant water level that would connect

the city of Siem Reap to Lake Tonle Sap. In order to maintain that constant water level, the

restoration of the East Baray and construction of a dam in the Kulen Mountains to the north

would provide water storage from the wet season for use in the dry season.

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B. Hydraulic History1

1. History of the Siem Reap River

The River Siem Reap is the only permanent stream in the area. This is due mostly to the Kulen

Mountains in the north; they are oriented in such a way as to create the most rain in the region,

which flows through the river to Lake Tonle Sap. The history of the river can be traced back to

before the Angkor period began, when the Khmer used water management near the base of the

Kulen Mountains to store and retain water in order to release it through the River Siem Reap.

Around 950 A.D., King Rajendravarman diverted the River Siem Reap north of the East Baray to

direct it straight south to the Baray, and then turn it west.

There is debate whether the river was diverted south right away, along the East Baray, or if it

continued west to the present West Baray. For certain though, beginning in the 16th century, the

river broke though a wall extending from East Baray to Angkor Thom west of the baray and

began to flow south along the East Baray.

The River Siem Reap most likely did not fill anything east of the temples in the ancient times.

The East Baray, North Baray (Indratataka), and the moats of the temples were most likely filled

by the River Roluos before the inlet to the East Baray silted up. The River Siem Reap did

however fill the West Baray, through a canal built when the River Siem Reap was diverted

around the East Baray. Later, when the East Baray silted up and the West Baray was taken out

1 Hisotry in this section derived from: Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Various Pages.

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of use, the River Siem Reap is assumed to have filled the temple moats though the West Baray

diversion canal.

Regardless of the debate as to what the River Siem Reap did and did not do, one thing is for

certain: The River Siem Reap has long been a part of the area’s water management strategy, and

the idea that it should be used to help the people and the temples regain some of the respect they

deserve is appropriate to the culture in the area.

2. History of Barays

A baray is a huge, man-made reservoir built to store water for use during a dry season. Barays

typically have a very large surface area and a relatively shallow depth. The reservoir is typically

constructed above the ground, and the water is held in by a rectangular wall of earthen walls, or

dikes.

The original barays in Cambodia were built by the ancient Khmer civilization. While recognized

primarily for its construction of the magnificent Angkor temples, this civilization also displayed

its architectural genius by building the barays. These barays were essential in both agriculture

and in the survival of the people themselves. The people used water from the barays during the

dry season for irrigation, drinking, and bathing.

The largest baray was the West Baray, and it was nearly twice as large as the East Baray. The

West Baray covered an area of about 17.6 square kilometers (km2) and could hold a depth of 7 m

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of water. This enabled the West Baray to hold over 123 million m3 (32.5 billion gallons) of

water.

The second largest baray ever built by the Khmer civilization was the East Baray, and it was

built during the reign of Yasovarman I. Upon completion, the East Baray measured 7.5 km in

length and 1.83 km in width. The original depth of water was 4-5 m, which enabled the baray to

hold up to 55 million cubic meters (m3) (14.5 billion gallons) of water.

Since their original construction, both of these barays have been intruded upon and developed

with homes to a certain extent. The West Baray was restored in the mid 1900s to again hold

water, but the East Baray is dry and about one-third (the east third) has been developed. People

began to build homes in the barays for various reasons, but primarily because certain areas of the

barays became insufficient to hold water due to sediment buildup in these areas.

3. History of Mountain Dams

Even before the Angkor Empire became established, there is evidence that the Khmers

“practiced water management at high engineering standards in the Kulen Mountains.” They

diverted and retained water to meet growing demand. Even today citizens reap the benefits of

these ancient engineering projects. These have helped alleviate the stresses imposed on the

citizens by the seasonal fluctuations in water availability.

Though it is difficult to detect them today due to overgrowth, names still used to refer to the

features, like “the rivulets of the great dam,” “the rivulets of the broken dam,” “the artificial

basin,” “and “the reservoir,” may bear witness to these ancient structures.

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III. Challenge

A. General Currently the Siem Reap River flows from the Kulen Mountains north of the city through the

Angkor temple site, through the city of Siem Reap, and south to Tonle Sap Lake. The monsoon

climate that the area experiences means a 5 month dry season during which there is very little

rain and a 7 month wet season during which there is abundant rain. During the rainy season

there is significant flooding along the river. During the dry season, the flow in the river is not

sufficient to support boat traffic, and water availability for irrigation is very limited. Because of

these large variations in flow, water quality is also an issue. During low flows, eutrophication

has caused significant water quality problems.2 During flooding events, roadside ditches filled

with sewage and those filled with fresh water are mixed. This is a serious human health hazard.

Construction of a new canal alone would mean even lower flow rates and depths in the dry

season, as water would have less resistance to flow and would flow out of the system as fast as it

is brought in during the wet season. Also, many people depend on the existing branch of the

river for their livelihood. Therefore, both the old branch and the new canal would need to

maintain high flows and depths through the whole dry season.

According to the study,

The potential alternatives for enhancing the flow in the River Siem Reap include the

construction of one or several new dams in the Kulen Mountains, expansion of the West

2 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 46.

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Baray and reconstruction of the ancient Khmer reservoirs, such as the North and East

Barays…Thanks to their relatively small surface and low seepage losses, the deep

mountain reservoirs would be capable of storing the runoff of wet years for dry years…It

is important to note that such a new dam storing the high-quality waters in the Kulen

Mountains may be the key to the long-term water supply problem in Siem Reap

town…For exploring the valley-dam storage opportunities in the Angkor area, the

preparation of policy plan covering all details, a so-called Master Plan appears essential.3

From this, the decision to restore the East Baray and construct a mountain dam originated.

Given the decision to use the baray and mountain dam for storage, new challenges arise. First,

there are some people living inside the dried-up East Baray. Either they would need to relocate,

or only the portion of the baray that is uninhabited could be restored.

There is little data available on the geotechnical features of the Kulen Mountains. Many

assumptions have to be made in light of this. Also, the topography is such that there is no

location suitable for a small dam that could still impound the necessary water volumes. Little is

known about habitation in the mountains, and if the filling of the reservoir would affect people

living in the canyon.

3 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 64-65.

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B. Design Norms

The following is a brief discussion on the design norms that bounded certain aspects of our

project. Under each, an example of one decision made in order to honor the norm is given.

1. Cultural Appropriateness

In order to be culturally appropriate, a design should fit into the culture in which it is intended in

terms of scale, culture, materials, and aesthetics. Siem Reap has a very distinct culture that

contains some bamboo huts, floating villages, and small local fishing rafts. Restoring the baray,

an icon of Cambodia’s cultural heritage, would be very culturally appropriate as well, as it would

fit in with the existing landscape and enhance the value of their cultural history.

2. Transparency

Transparent design should include open communication, should be understandable, and should

be consistent, reliable, and predictable. Because of this, complicated valves or piping are not

being used in the operation of the East Baray, but rather hand operated controls with simple gates

and pipes are being used.

3. Integrity

A design with integrity is complete, has harmony of form and function, and promotes values and

relationships. In choosing the lining of the baray, natural available clay in the area would make

for the most economic and harmonious solution, while a concrete lining would be an eyesore,

would not blend in with the surroundings, and would be dangerous.

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4. Stewardship

A stewardly design carefully uses the earth’s environmental resources as well as economic and

human resources. In line with this, earth excavated from one area, such as the canal or baray

floor, will be used as fill in other areas, such as the peninsular birm or the protective dike. This

will save money and time (man power).

5. Justice

Just design respects the rights of all stakeholders. The components in our design will benefit all

of the people in Siem Reap, but some more than others. For example, increased dry season water

availability and flow rates in the river will allow for more water for irrigation and thus a longer

growing season.

6. Caring

Caring design takes into account the effect on individuals physically, socially, and

psychologically. Because our design will increase the quality of life, it will care for the

individuals of Siem Reap in these ways.

7. Trust

A design that is trustworthy is dependable and avoids conflicts of interest. Proper measures will

be taken in order to ensure that components can still function and be easily repaired in case of

failure.

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IV. Solution

In order to address the problem, the design was split into the three components. Also, a

(partially) scaled model of the area (see Figure APP – D.3) was created to assist in visualization

of the landscape and to show others the effects the design would have on the region.

A. Channel and River

1. Purpose

The channel will create an easily navigable waterway from the city of Siem Reap to Tonle Sap

Lake south of the city. Due to large variations in the Tonle Sap Lake and the Siem Reap River, it

is not possible to reach the city by boat for the dry season. The channel, in conjunction with the

mountain dam, the East Baray, and the set of locks designed by Keep it Cambodian, will create a

constant waterway for boat traffic to reach the city from the lake and vice-versa.

2. Site

The location of the channel has been set by the architect of the Master Plan, Professor Kim. He

has specified that the channel break away from the existing river and head due south to Lake

Tonle Sap, south of the city. The junction of the new channel and the River Siem Reap is to be

located in the center of the city, allowing tourist boats to leave from the city, travel upriver to the

temples and downriver to the lake. Shown below in Figure A.1 is a diagram of the area, showing

the new channel.

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Figure A.1 Site diagram.

The dominant soil in the area is laterite clay, although very little data is available beyond this.

The clay was used to make bricks for the temples and other buildings constructed during that

time period. Because the clay can be used to make bricks and therefore must be a fairly stiff

clay, a clay lining was assumed to be appropriate. More on this feature of the channel is

available in the Lining section of this report.

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3. Social and Environmental Considerations

This part of our project requires some special considerations be taken in terms of the

environmental and socio-economic impact. As with any large scale project, an in-depth study of

the impact of this project on all areas of concern including many not listed here should be

undertaken.

By moving the main waterway in the area, there is the risk that wildlife and plant-life can be

disrupted. A study should be conducted, and recommendations regarding the fish patterns and

plant life concentrations made. We have recommended the existing branch of the river be left

intact in order to lessen the impact on the area. At the junction of the two branches, a weir

should be placed to control flow between the branches. This dam should not interfere with any

wildlife. If it does, special projects should be considered to amend these interferences.

Due to the relatively dense population in the area and the people’s dependence on the river for

health and economic wellbeing, special care should be taken with such a large alteration of the

landscape. The effect of the new channel on the rice paddies should be especially studied, as this

is the sole source of income for many of the people in the area.

4. Hydrology

The hydrology of the area is dominated by its monsoon climate. During the wet season, there

can be over 10 in. of rain in one month. However during the month of January, the average

rainfall is less than 0.2 in. This creates the navigational situation described above.

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This project does not account for runoff into the river and channel along its length. While there

will be some runoff entering the river and channel, there is not enough data on the duration and

frequency of the storms to accurately model this part of the hydrology. At the beginning of each

storm, a certain amount of the rainfall is absorbed into the ground as infiltration. With shorter

duration storms that happen more frequently, more runoff is lost to infiltration, with more storms

lasting longer less is lost. Without allowing for this runoff to enter the river and channel, we

have used a conservative model, and actual needs in terms of flow from the baray and the dam

will be less than this report specifies.

5. Design

a) Methods

The design of the channel was done using mainly the U.S. Army Corps of Engineers’ Hydrologic

Engineering Center River Analysis System (HEC-RAS) modeling software. This software is

considered the standard in river modeling software, and is used industry-wide in the U.S.4

Several other methods were incorporated where appropriate, but are secondary to the modeling

software. They will be referenced as needed. Figure A.2 shows an example of the interface.

4 http://www.hec.usace.army.mil/

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Figure A.2 HEC-RAS

b) Geometry

The channel geometry is dictated mainly by the amount of storage the baray and the dam can

provide. In addition, it must be able to handle the tourist ferries that are common in the area.

Due to these constraints, the following dimensions are proposed (Table A.1):

Table A.1 Channel dimensions. Total Length: 20 km

Extension: 4 km Width: 12 m Depth: 2 m Side Slope: 1.5 m/m Bottom Slope: 0.0012 m/m

The existing river has dimensions which are variable, but can be approximated as follows based

on available GIS (Table A.2):

Table A.2 River dimensions. Total Length: 80 km Width: 10 m Depth: 2 m Side Slope: 1.5 m/m Bottom Slope: Varies

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The river has two ninety degree bends near the Angkor temple site north of the city. These

bends have been included in the model. The existing river makes a turn to the west as it exits the

city; however the proposed channel will track due south as it leaves the city until its end. Figure

A.3 shows the river and proposed channel as they were entered into the HEC-RAS model.

Figure A.3 HEC-RAS geometry.

c) Baray Structures

Several structures were added to the model to accurately predict velocities and flow geometry.

Most complex are the inlet and outlet structures to the East Baray. Culverts were modeled as

taking water to and from the river to the Baray, with check valves used to control flow.

Hydraulics controls the water level in the Baray. During the wet season, the Baray will fill using

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water from the river, and during the dry season the Baray will add flow to the river to maintain a

reasonable water level. A more complex explanation of these structures, their workings, and

their purpose is in the Baray Restoration section of this report.

d) Excavation

In order to make an accurate cost estimation, cut and fill numbers were estimated. This was

done using a Microsoft Excel spreadsheet. The volume of the channel was calculated and

marked as cut. The volume needed to create the extension of the channel into the lake was

calculated and marked as fill. The difference was taken, and this was the number used in cost

estimation. Shown in Table A.3 below are the numbers obtained from the spreadsheet. The

entire spreadsheet is shown in Table APP – A.2. More information on the assumptions made

about the extension of the channel into the lake is available in the Channel Extension section of

this report.

Table A.3 Excavation numbers Total Cut 363,200 m3

Total Fill 5,602,775 m3

Sum Total Excavation 5,239,575 m3

e) Lining

Due to the relatively high velocities in the channel, a lining for the channel walls has been

specified. Determining that a concrete lined channel does not fit with the integrity of our project

due to unappealing visual properties and a clash with local culture, the options considered are

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limited. Using a report on earthen channel construction by an Australian research firm,5 we can

obtain a maximum velocity for clay of 1.65 meters per second. The maximum velocity reported

in the HEC-RAS model is 1.64 meters per second without riprap at the junction, although most

of the channel remains under one meter per second. This allows use of the naturally occurring

laterite clay in the area as the lining material for the channel. Special care should be taken within

a few months of construction, as these velocities are based on fully established flow and

sedimentation.

At the junction of the new channel and the existing branch of the river, riprap protection is

recommended. This is due to the higher velocities and stresses experienced at the junction.

Shown in the appendix is the calculation of D30 of the riprap, in feet. This is the size of stone for

which no more than 30% of the stones in the sample are smaller than a diameter of D30. This is

the standard way to define a size of stone used in riprap, and is based on many factors including

the velocity and depth of flow and specific weight of the stone. It includes a safety factor of 1½.

We feel this safety factor is reasonable, given the relative predictability of the water levels on the

river after this project is completed. A more comprehensive calculation should be done onsite,

and should include more detailed information on what size and weight stone is available near the

site. This analysis is based on the Army Corps of Engineers’ Hydraulic Design of Flood Control

Channels manual.

5 National Program for Irrigation Research and Development. "Section 12.11.3 - Maximum Velocities." Construction and Refurbishment of Earthen Irrigation Channel Banks. Canberra ACT, Australia: Land and Water Resources Research and Development Corporation, 2001. 81

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This analysis yields, according to page 3-3 in the ACE manual, a maximum stone size of nine

inches, and a maximum stone weight of thirty six pounds. This also yields a W15 of two pounds.

This is the weight where less than 15% of the stones should be less in weight than W15. The

minimum weight is more important than the maximum, and should be given preference when

determining if a particular sample is appropriate for the riprap lining. The riprap should be well-

graded, with a D85/D15 of less than three. The thickness of the layer should be at least the

diameter of the largest stone, or at least nine inches.

It should be noted that using riprap at the junction brings the velocity down to 1.34 meters per

second, and the velocities return to normal (less than one meter per second) before the riprap

lining ends. The decrease in velocity is due to changes in the friction between the water and the

sidewalls of the channel. Riprap creates more friction than the existing weedy banks of the river,

so the water slows down, adding to the protection provided by the riprap.

Guidelines for the determination of length of rip rap protection have not been well established.

Usually the point downstream where velocities return to normal, sub-erosion speeds is

considered far enough. Using our model as a guide, the velocity has returned to normal

immediately after the junction, since it is before the junction that the velocity speeds up. Rip rap

should be placed for one hundred meters upstream of the junction, and fifty meters downstream

on both the river and channel.

f) Junction

At the junction, a flow split is forced. Unfortunately, the natural flow split is insufficient to meet

the needs of the navigable channel. A structure will need to be placed in the old branch of the

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river. By placing the structure in the old brand of the river, boat traffic will not be impeded by

the structure. Two options were considered for the structure, a weir and a small dam. Both

structures were found to meet the requirements. The biggest difference will be if a road is

needed at that point in the river. The dam would create an embankment to place the road on,

whereas the weir is completely submerged.

If chosen, the dam should be placed at the junction of the new channel and the existing branch of

the river. The dam was modeled as placed across the old branch of the river 480 meters

downstream of the junction to control flow entering the new channel, as a deck with two 1 meter

diameter concrete culverts at the base and 16 meters thick. The level of control will be

maintained hydraulically, so periodic inspection of the culverts and dam should be made to

ensure safety.

As with any dam, there are specific considerations to be made. Safety is always a concern with

any hydraulic structure. Dams are especially prone to scrutiny, as their failure is often

catastrophic, with serious repercussions to humans, animal life, plant life, and geologic features.

Environmental impacts of dams are also significant. As with this project as a whole, studies

should be performed to measure this impact and determine the best method of dealing with the

impacts. A fish ladder should be constructed to maintain a path for fish species to migrate.

Locally performed studies should be relied on for in-depth specifications on appurtenant

structures. A more detailed discussion on the repercussions of a dam can be found in the dam

design section of this report.

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If a roadway is not needed, the weir is recommended. A weir is completely submerged, and so

the natural surroundings will not be disturbed. Fish will be able to pass over the weir, and so no

additional structures will be needed to accommodate them. The environmental impacts of the

weir are less, since water is allowed to flow over the weir naturally. There is a concern with

weirs that they increase the velocity in the channel to unacceptably high levels. However, the

maximum velocity reached with the weir in place is 0.87 meters per second, well within the

maximum velocities set by the channel banks, and well within the capability of most fish. Using

pink salmon as a gauge, we can find the sustained swimming velocities of fish. The University of

British Columbia found the sustained velocity of a pink salmon as 2.5 body lengths per second,

or 1.14 meters per second, with prolonged velocities up to 1.46 meters per second.6

The weir should be 2 meters from channel bed to the top of embankment, at the same location as

the dam above. The top of the weir should be 2 meters long (inline with the river) and have side

slopes of 2 to1. See Figure A.4.

Figure A.4 Weir in the existing river.

6 Hinch, Scott G., Emily M. Standen, Michael C. Healey, and Anthony P. Farrell. "Swimming patterns and behaviour of upriver-migrating adult pink (Oncorhynchus gorbuscha) and sockeye (O. nerka) salmon as assessed by EMG telemetry in the Fraser River, British Columbia, Canada" Hydrobiologia 483.1-3 (2002): 147-160.

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g) Channel Extension

This part of the channel’s purpose is to create a way for boats to gain access to the channel year

round. In the dry season, the level of Tonle Sap Lake drops significantly. This creates a section

of river which is too shallow for boats to navigate. By extending our channel out 4 kilometers

out into the lake, the level in the channel can be kept constant, and using the set of locks

currently being investigated boats will be able to reach the City of Siem Reap year round.

Table A.3 shows excavation numbers. Because of the magnitude of the required fill, the

feasibility of this part of the project hinges on whether locally available fill material will be well

suited to the application. To haul in soil from a source far enough away to require extensive

trucking or barge transport may be too costly to complete. A full cost estimate is presented later

in the report.

Shown below in Figure A.4 are two views of the extension into the lake. The dimensions will

change depending on how far into the lake you take the cross section, so dimensions are not

shown. Also, without good elevation data on the lake bottom, all figures, excavation numbers,

and cost estimates are approximate and should not be used for bidding purposes.

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Figure A.5 Channel extension.

The top view is a cutaway of how the fill will need to be placed. The slope of both the inside

and outside slopes have been set at 1:1½, although this will depend on the type of material used.

The bottom view is a side view of how the extension will rest in relation to the lake bottom. The

dashed line represents the channel bottom.

The top width on either side of the channel was figured to be 70m wide, enough for a United

States typical 1-acre square lot (4046m2), plus 6.5m for a road to run the length on either side of

the channel. The channel width and depth in the extension are the same as for the channel after

the junction. Two meters was specified for the freeboard on the extension, because of storms on

the lake that could create waves that would endanger the buildings on the extension. If local

storms dictate that more freeboard than two meters is necessary, changes to the design should be

made to accommodate those storms.

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In order to allow the flow coming down the channel to escape without flooding the channel, a

spillway will need to be constructed at the end of the extension. The weir elevation should be set

at two meters below the level of the extension, and therefore equal to the level of the ground at

the highest lake level. This will maintain the level of the channel at a depth of two meters, and

allow for emergency flows if both locks have been out of operation for extended periods of time.

Width is not crucial as long as width is relatively large, because hydraulics will control the

amount of flow exiting, and there is no danger with high velocity flows leaving the spillway, as

the lake will absorb any excess of energy. A width of 6 meters was chosen, and with a length of

18 meters down the embankment, and a side slope of 1 to 1 on the walls, an area of 159 m2 for

the spillway was used for costs.

6. Safety

The largest issue with safety in the channel is the velocity of the water. With a velocity of over

two feet per second (over 0.62 meters per second), there is the potential for safety concerns. The

river is a central part of the culture in the area, and the people of Siem Reap use the river daily

for drinking and multi-purpose water, bathing, cleaning, and many other uses. Extreme caution

should be exercised when approaching the river, as water velocities of two feet per second can be

strong enough to sweep weak swimmers downstream. The channel is not deep, and is not

expected to contain rapids or other dangerous structures, but the rip rap and the weir at the

junction could cause injuries.

7. Cost Analysis

The cost analysis presented in this report is based on limited data. Very little data on the soils in

the area, the construction methods, hydrology, topography, and many other very important

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factors was available for this report. Presented below is a cost estimate based on assumptions

and United States methods, and it should not be used for bidding purposes.

Excavation is the single largest cost in the construction of the channel. While some fill material

will be available from the excavation of the channel north of the lake, a lot of material will need

to brought in to construct the extension. Table A.4 summarizes the excavation numbers, costs

associated with each type of excavation, and the total cost for that type of excavation.

Table A.4 Excavation cost summary. Bulk Need (CY) Unit Cost Total Cost

Cut 474339 $ 1.71 $ 862,085

Hauling 474339 $ 7.90 $ 36,346,892

Fill 7317224 $ 8.15 $ 26,830,609

$ 64,039,587

The fill cost includes compaction, but assumes the material will be hauled from 5 km and

dumped at the site. The cut cost includes loading the material into waiting trucks.

Other than excavation, there is little cost associated with the channel. The next largest cost will

be the rip rap at the junction of the river and the new channel. Using the size of stone and length

of coverage shown in the Lining Section of this report, we can calculate a volume of rip rap

needed. Using a depth of 9 inches and a length of 150 meters (492 feet), with a width of twelve

meters (40 feet), we get a volume of rip rap of 14,760 cubic feet. Using RS Means data, we can

get a cost of rip rap of $21,378. The second cost other than embankment is the concrete spillway

26

at the end of the extension. As previously stated, a surface area of 159 m2 was used, and with

RS Means data, this brings the spillway cost to $4,413.

Using these three costs, which are the three main costs that can be calculated in this report given

the limited data on construction methods, gives a total U.S. dollar construction cost of

$64,082,343. This total cost does not include any extra fees or costs. Including 15%

contingency, 5% licensing, 5% environmental, and 10% engineering, the cost becomes

$86,488,261. However, this assumes U.S. construction methods. Were we to assume that in

Cambodia, labor is cheaper and equipment is more expensive, we should adjust the cost of the

project. Due to the lack of data, no adjustments can be made. To account for this, it should be

assumed that the price of the project could fluctuate by up to 10% in either direction. This is

based on estimates of cost changes, and the fact that there are certain baseline costs that will not

be affected, such as contractors overhead and profit.

B. Restoration of the East Baray

1. Purpose

The purpose of restoring the East Baray is to create a reservoir that will store water from the wet

season for use in the dry season. The baray storage will supplement the storage gained from the

mountain dam, and together they will maintain a more constant water level in the new channel.

2. Site

The East Baray is located to the East of the Angkor Wat temple in the city of Siem Reap,

Cambodia. A GIS rendering of the site can be seen in the Appendix in Figure APP – B.1. In its

present state, the East Baray is about one-third developed and two-thirds undeveloped (left in its

27

original constructed state). As mentioned above, the ground elevation of the eastern one-third of

the baray has increased to a point where it is no longer feasible to store water in this area.

However, an extensive construction project potentially could enable the western two-thirds of the

East Baray to be used for water storage. Four cross-sections of the East Baray at various

locations in the baray can be seen in Figure APP – B.2.

As shown in the last sketch in Figure APP – B.2, the average depth in the section farthest to the

east is generally less since this cross section is in the one-third of the baray that is silted in and

developed.

It also can be noted from the first three sketches in Figure APP – B.2 that the average top

elevation of the baray walls (dike) is about 30 m. The following paragraphs describe cross-

sections of the four dikes that compose the boundary for the rectangular East Baray.

The northern dike of the East Baray is about 2.5m tall, with side slopes of about 1:7. The crest

width is about 6-8m. The crest of the dike is partially clear of vegetation, but both the slopes are

covered fairly heavily with vegetation about 4-5m tall.

The southern and eastern dikes are 6-7m tall, with side slopes between 1:6 and 1:12. The steeper

slope is generally on the water side of the dike. The crest width is about 8-10m. The crests of

the dikes are clear of vegetation, but both the slopes have sparse medium-sized trees and light

vegetation.

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The western dike is about 5-10m tall, with side slopes between 1:6 and 1:12. The steeper slope

is generally on the water side of the dike. The crest width is about 8-10m. The crest of the dike

is clear of vegetation, but both the slopes have sparse medium-sized trees and light vegetation.

3. Social and Environmental Considerations

In addition to restoring part of the East Baray for water storage purposes, the restoration also

would have cultural and historical significance. Restoration of the E. Baray nearly to its original

state will evoke a great sense of pride in the Cambodian people for their ancestors. The

restoration also should draw more tourism to the temples and create a special wildlife habitat for

the fish and birds in the area. Finally, the restored baray – in conjunction with the mountain dam

– will decrease annual flooding, require fewer repairs on homes, and allow for easier

transportation.

4. Hydrology7

The hydrology of the area of Siem Reap is vital to the restoration of the East Baray. That is, the

intensity, duration, and frequency must be determined for any rainfall event that can be expected

to occur in any given year and contribute to the functioning of the baray. The amount of rainfall

must be determined as well as the evaporation rate, infiltration rate, and other mechanisms that

could cause water to or inhibit water from getting into the baray.

7 Data in this section taken from: Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 10-18.

29

The monsoon rains typically occur between June and October, and they follow a similar pattern

of clear mornings with one- to three-hour rains in the afternoon. The table in Table APP – B.1

shows the monthly distribution of the total yearly rainfall.

Table APP –B.1 indicates an average yearly rainfall of 1434-mm (56.5-in). Another source

predicts a mean annual rainfall of closer to 1600mm (Figure A3.2 p A-31 Irrigation Study). For

the purposes of our design, we will assume the lesser rainfall.

The reports listed above also presented information regarding the average evaporation rate and

the potential evapotranspiration rate. The mean annual evaporation is about 1020-mm while the

mean annual potential evapotranspiration is 1542-mm. Therefore, is easily can be concluded that

the rain that falls directly into the baray cannot be considered a reliable, dependable water source

by itself. Water must be collected from a much larger area in order completely to fill the western

portion of the East Baray.

5. Design

There are six main components to the design. First, the western two-thirds of the East Baray

must be excavated to a certain extent to allow for adequate water storage in the baray. When

utilized in coordination with the mountain dam described in another section of this report, the

baray will assist in providing year-round water flows in the River Siem Reap.

Second, a new dike (baray wall) must be constructed to isolate the developed area of the East

Baray from the western area that will be used for water storage. This new dike should match the

existing dikes, fit into the natural surroundings, and be aesthetically pleasing.

30

Third, the existing dikes must be reconstructed or re-stabilized, as they have not been used for

water storage for many years. Dikes that have not been used for many years are often worn and

undermined by human activity, rodents burrowing into the dike, and natural erosion.

Fourth, roads either must be re-built or constructed on the crown of the dikes to facilitate

transportation around and across the East Baray.

Fifth, an intake structure and pipeline must be utilized to transport water from the River Siem

Reap into the baray during the rainy season.

Sixth, an outlet works must be designed to release water from the East Baray back into the River

Siem Reap during the dry season.

a) Excavation in East Baray

The first main component of the restoration of the East Baray is the excavation, or removal, of

enough of the built-up silt and sediment from the bottom of the baray to provide the desired

water storage volume. As was mentioned in the “Site” section above, the average elevation of

the top of the baray dikes is about 30-meters. As it is probably not feasible to continue building

up the baray walls, it will be necessary to excavate from the floor of the baray. Therefore, it will

be assumed that the elevation of the top of the baray dikes will remain at 30-m.

To obtain the desired water storage volume of 30,000,000-m3, an average water depth of 3.5-m –

4.0-m is required throughout the western two-thirds of the baray. To minimize the risk of

31

significant damage due to flooding and erosion, the maximum water elevation in the East Baray

must be 29-m. With this parameter set, there will be a safety zone of 1-m in which a variety of

actions can be undertaken to prevent potential flooding.

To obtain the required water depth of 3.5-m – 4.0-m while holding the maximum water elevation

at 29-m, it can be deduced that the average elevation of the baray floor must be between 25.0-m

and 25.5-m. As it has been difficult for our design team to obtain accurate and precise survey

data for the land inside the baray dikes, we have estimated that an average of about 0.5-m of silt

must be excavated from the western two-thirds of the baray. However, it must be noted that this

number may not be completely accurate. Therefore, the Owner or the contractor must verify the

elevations in the field to ensure that adequate excavation is performed. It also must be noted that

certain areas may require more excavation than estimated, while other areas may require less

excavation or no excavation at all. However, to ensure that the baray, in coordination with the

mountain dam, can provide sufficient flow to the River Siem Reap all year long, the baray must

be able to hold about 30,000,000-m3 of water.

It has been estimated that the western two-thirds of the East Baray covers an area of about 9.15-

km (1830-m x 5000-m). If an average excavation of 0.5-m occurs, the total excavation volume

will be about 4,600,000-m3.

b) Construction of new dike across East Baray

The second main component of the restoration of the East Baray is the construction of a new

dike that will separate the western two-thirds from the more developed eastern one-third. This

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new dike should match the existing dikes, fit into the natural surroundings, and provide a

reliable, dependable safeguard against the water that will fill the baray.

In order for the new dike to match the existing dikes, it should be constructed of similar material

and it should have similar geometric characteristics. After researching the geology of the area, it

was determined that most of the soil in the area is composed of laterite clay. Therefore, the new

dike should be constructed with laterite clay or another material approved by the Owner. Since

extensive excavation will be taking place in the western part of the baray, some of the excavated

material should be used for the construction of the new dike.

The new dike also should have similar geometric characteristics as the existing dikes. Therefore,

the elevation of the top of the dike should, on average, be 30-m. The width of the top, or crown,

of the dike should be 10-m. To minimize both erosion and the potential for injury, the average

side slope of both sides of the dike should be four meters horizontal displacement for every one-

meter vertical displacement. Since the average elevation of the baray floor (in its present state)

is about 26.25-m, the average height of the new dike will be about 3.75-m. Therefore, the

bottom width of the new dike will be about 40-m. The total length of the dike will be

approximately 1800-m, the width of the baray.

With these dimensions, the volume of material required to construct this dike is about 172,000-

m3 of compacted material. The dike must be constructed at no greater than 0.25-m lift intervals,

and heavy compaction should take place after every lift. That is, accumulation of material

should not progress in any one location to a depth greater than 0.25-m before the layer is

33

compacted. Once the material is compacted, another 0.25-m lift can be distributed, and

compaction can take place again. This sequence must be followed for the construction of the

entire dike. See Figure APP – B.3 for a schematic of the average cross-section of the dike.

For the new dike to fit the natural surrounding, very small trees and light vegetation may be

planted on the sides of the dike. Planting of anything larger than bushes or small trees is

discouraged because larger root systems would present passageways for increased water seepage

(and thus erosion) through the dike.

For the new dike to provide a reliable and dependable safeguard against the water, it should be

compacted heavily to minimize water seepage through the dike. The soil material with which the

dike is constructed should be a well-graded mixture (diversified soil particle size). The larger

soil particles (gravels) will provide structural stability while the smaller particles (silts and clays)

will provide a hydraulic barrier to minimize seepage.

c) Reconstruction of existing dikes

The third main component of the restoration of the East Baray is the reconstruction or repair of

the three existing dikes surrounding the western portion of the baray (the new dike will be the

fourth boundary). It is the understanding of our design team that the East Baray has not been

used to store water for a very long period of time. Consequently, the dikes most likely have been

eroded and undermined by human activity, animal and rodent activity, and heavy rain during the

rainy season. In addition, embankments that have not held water for a long time are more

susceptible to erosion because stored water normally protects the dikes.

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Therefore, it will be necessary carefully to inspect all the baray walls and report any damage or

erosion, however minimal it may be. Upon completion of the inspections, the dikes should be

reconstructed or repaired. If it is concluded that portions of the dikes are weak but do not require

complete reconstruction, the dike should be stabilized so that it is as structurally sound as the

other dikes.

The material used for the reconstruction and stabilization of the existing dikes should be the

material excavated from the floor of the baray, or another material approved by the Owner. If

there is an inadequate amount of material from the baray excavation to repair the dikes,

coordination should be made with construction of the new channel to transport clay from the new

channel to the baray.

d) Construction of roads on top of East Baray walls (dikes)

The fourth main component of the restoration of the East Baray is the new construction or the

reconstruction of a roadway surface on top of all the dikes. These roads will facilitate

transportation both around and across the barays.

To provide open space for the roads, the top of the dikes should be cleared of all trees, brush, and

other vegetation. The root systems of all trees must be removed as well to ensure the structural

integrity of the dike. Once cleared, the dike crown should be graded to a smooth surface. If the

materials can be obtained, it would be valuable to the long-term reliability of the road to

incorporate a layer of gravel on top of the dikes for the road surface. This gravel layer also

should be compacted for optimum stabilization for the road. In addition, the gravel will assist in

35

transporting and draining rainwater from the surface of the dike. Special care should be taken to

maintain these roads, as degradation of the roads could lead to degradation of the dikes

themselves.

e) Inlet Works from River Siem Reap to East Baray

(1) Goals for Design

The goals for the fifth main component of the implementation of the East Baray are twofold:

First, to take water from a location in the River Siem Reap upstream of the East Baray and

transport it to the baray during the wet season. Ideally, the baray will be filled completely upon

the onset of the dry season. Second, to design the system so that each function can be performed

with minimal effort by the operators, such as simply opening and closing a valve or gate at a

specified time.

(2) Design Options and Alternatives

Realizing that this was a significant feature of the implementation of the East Baray, three design

alternatives were developed and evaluated with the intent to select the most viable option. The

alternatives were as follows:

First, construct a diversion structure in the River Siem Reap as close to the baray as possible.

Water would then be diverted from the river to the baray for a certain period of time, and the

baray would be filled. This was the method used when the barays originally were built.

This option is shown schematically in Figure APP – B.4.

36

However, sedimentation has increased the floor elevation of the baray and necessitated the

increase in elevation of the top of the dikes. Consequently, the highest water level needed in the

baray to obtain the required volume is 29.0-m. Our limited data shows that the elevation of the

water surface in the River Siem Reap at the location mentioned above is about 26.5-m, which

would not be adequate completely to fill the baray and attain the necessary storage volume.

Second, build an above-ground pipeline that would take water from a location in the River Siem

Reap a few kilometers upstream of the East Baray and deliver it to the baray. The intake for the

pipe would be far enough upstream so the water could flow by gravity through the pipeline and

discharge the water over the baray wall. This arrangement would allow for the highest possible

water level in the baray. However, it would be difficult to build and it would be a safety hazard

and an eyesore to have a large concrete pipe up resting on supports up in the air. This

arrangement would not be aesthetically pleasing or fit into the natural surroundings at all.

Third, construct an underground pipeline from an intake structure in the River Siem Reap

upstream of the baray. The intake structure would draw water from the river bottom at a location

between 1-km and 2-km upstream of the baray at higher elevation. The water would flow

pressurized through the pipeline since the river essentially would act as a reservoir with the pipe

coming out the bottom. The intake structure would be far enough upstream to ensure adequate

flow to the baray and allow the baray completely to be filled. The pipe would be underground

for its entire length, and at the baray it would discharge into the baray at the bottom of one of the

dikes. The pipe would be pressurized the whole time so that the water would flow from the

37

higher reservoir (river) to the lower reservoir (baray) even if it has to flow uphill for a short

distance. An outlet structure would deliver water from the pipeline to the baray.

(3) Selected Final Design

The final design selected for the inlet works from the River Siem Reap to the East Baray was the

underground pipeline with an intake structure in the river and outlet works to discharge into the

baray (design option 3). The following pages of this report will outline the main components of

the final design.

(4) Components of Final Design

The structure that will charge the East Baray with water will have the following three main

components: an intake structure in the River Siem Reap, a concrete pipeline to transport water

from the intake structure to the East Baray, and an outlet works to discharge the water into the

baray. In addition to these components, consideration will be given to sedimentation in the baray

and the possible necessity of a stilling basin inside the baray.

(a) Intake structure in River Siem Reap

As water needs to be taken from the fairly shallow River Siem Reap, there must be an intake

structure that enables water to be removed from the river without posing significant challenges to

boat traffic. The water must be obtained from a location in the river at an elevation high enough

to pressurize the flow in the pipe and cause it to flow into the baray. Therefore, three important

parameters must be specified regarding the intake structure: the location of the intake structure,

the elevation of the river at the intake structure, and the dimensions of the structure itself.

38

First, the intake structure must be located at a point in the river at which it has minimal impact on

the environment, the surrounding area, and the boat traffic in the river. Such a point is located to

the north of the East Baray. Since relatively few people travel north of the city of Siem Reap, an

intake structure in the river here would not pose significant problems.

Second, the water elevation of the river at the intake structure is critical to this component of the

design. As the pipeline always will be pressurized, the water surface elevation at the intake must

be high enough to overcome the head losses in the pipeline and cause water to flow into the

baray even when the baray is nearly full. However, the surface elevation should not be required

to be so high that excessive money is spent to construct a pipeline to the location that has this

elevation. A detailed model was created to determine the necessary elevations and dimensions

of the intake structure. Since the maximum desired water elevation in the baray is 29.0-m, it was

decided that a river water surface elevation of 30.0-m would be sufficient and necessary to

charge the baray. The place in the river that has this water surface elevation is located at a point

approximately 1.3-km north of the East Baray in the middle of the river.

Third, the physical characteristics of the intake structure are important in defining the capacity of

the pipeline. As the structure will be located in the middle and at the bottom of the River Siem

Reap, it is desired to have the structure as short as possible to eliminate interference with boat

traffic. Therefore, it was determined to construct a concrete intake structure 3-m long by 3-m

wide by 0.75-m tall. See Figure APP – B.5 below for a diagram of the intake structure. The top

and two sides of the structure will be open to accept water flow, but the backside (opposite the

39

pipeline) will have no opening. The top and sides will be protected from brush and debris by

steel trash racks that cover the openings but don’t inhibit flow.

Consequently, the intake structure will draw water from the River Siem Reap and convey it to

the pipeline, which will then transport the water to the East Baray.

(b) Pipeline from intake structure to East Baray

Next, the water must be transported from the intake structure located upstream of the baray to the

outlet works that will discharge the water into the baray. A base design was developed and

optimized, and it was determined that a 4-ft diameter concrete pipe would be necessary to

provide adequate flow into the baray. Assuming the water surface elevation at the intake

structure is 30-m and the maximum and minimum water surface elevations in the baray are 29-m

and 25.5-m, respectively, a 4-ft pipe would provide flow between 1-m3/s and 4-m3/s to the baray.

Rather than having an aboveground pipeline that discharges water over the baray wall, it was

decided to construct an underground pipeline from the intake structure to the baray. Since the

pipeline will originate at the bottom of the river, it always will be full of water and thus

pressurized. As the pipe always will be pressurized, it can be constructed at the minimum depth

sufficient for adequate cover over the pipe, which will minimize construction costs. The pipeline

can follow the lay of the land. At the baray wall, it should penetrate the base of the dike and

discharge into the baray with no vertical displacement of the water as it exits the pipe.

With respect to the location of the pipeline, it should follow a fairly straight line from the intake

structure to the outlet works (see Figure APP – B.6 in the Appendix). Trees and vegetation

40

should be cleared from this pathway because sudden bends in the pipeline would cause

unnecessary and excessive exfiltration of water from and pressure head loss in the pipeline. Both

these situations would compromise the hydraulic functionality of the pipeline in charging the

baray each year.

(c) Outlet structure from pipeline into East Baray

The outlet structure is an important component of this part of the design. It must have the

capacity manually to open and close depending on the water level of the River Siem Reap at the

intake structure. For example, the gate should be open during the wet season to allow water into

the baray, and it should be closed during the dry season.

Two important parameters determine the structure and function of the outlet works. First, the

size of the outlet must be determined that will allow the desired flow to be released into the baray

at a velocity that will minimize erosion. Second, the materials with which the outlet works is

constructed must be decided.

Using an example from the book Design of Small Dams (Bureau of Reclamation), an outlet

works was designed that would take the flow from the pipeline and discharge it into the baray. It

was desired to design an outlet works that would create minimal head loss so that maximum flow

could be achieved in the pipeline. See Figure APP – B.7 in the Appendix for a detailed drawing

and dimensions of the outlet works. The concrete pipe will go through the baray dike and enter

the outlet works, which simply is a gated box so flow can be stopped. Another pipe will exit the

gated box and end inside the baray, where the water will be discharged into the stilling basin as

described below. The outlet works must be constructed of concrete or an approved substitute.

41

(d) Water flow control into East Baray

Water should not be allowed to flow uninhibited into the East Baray. The Owner should

determine the optimum times for opening and closing the gate in the pipeline that feeds the

baray. Generally, the gate should be open during the rainy season to allow for water to flow into

the baray. When the water level in the baray reaches Elev. 29.0-m, there are two options. First,

the gate could be closed and the water forced to bypass the baray via the River Siem Reap.

Second, the gate could remain open and water would be allowed to flow into the baray. Since

the emergency spillway on the outlet works back into River Siem Reap (in SW corner of baray)

is set at elev. 29.0-m, water would flow out of the baray at the same rate as it flowed in, thus

preventing stagnation and eutrophication. In addition, the hydraulics of the intake structure was

designed so that very little water would be flowing through the pipeline when the baray is full.

If water is allowed to flow into the baray at an average rate of 2.5m3/s and the maximum baray

volume is 30,000,000m3, it would take approximately 140 days (4.6 months) completely to

charge the baray. As the dry season is estimated to be about 6-months long, the baray should be

able to be charged each rainy season.

(e) Sedimentation considerations

As mentioned previously in this report, one-third of the East Baray was rendered not viable for

water storage due to soil transport and sedimentation from the Roulous River. Therefore, it is

important for our design to address this problem.

As it is not possible completely to eliminate the transport of sediment in the river, it is desired to

minimize it and remove it upon deposition in the baray. For a flow rate of 0.7-m3/s (lowest flow

42

rate in pipe), the water is flowing at a velocity of 0.61-m/s (2-ft/s), which will keep the sediment

suspended. Therefore, the velocity should be reduced so the particles settle out of suspension.

Such a velocity is less than 2-ft/s (0.61m/s). The velocity of the water will be reduced in a

stilling basin, as described in the next section, and the sediment will settle out of suspension.

Since it is undesirable for the stilling basin to fill with sediment, the basin should be cleaned

whenever necessary. If excessive sedimentation occurs at locations extending beyond the stilling

basin, parts of the baray may need to be dredged annually to maintain storage volume.

(f) Stilling basin inside dike

For a maximum flow rate of about 4.5-m3/s coming through the intake pipe and a pipe diameter

of 4-ft, water would be entering the baray at a velocity over 3.7-m/s (12.2-ft/s). At this velocity,

the water possesses an immense amount of energy and significant erosion would occur at the

point of discharge into the baray. Therefore, an energy dissipation device should be included

that will reduce the velocity of the water. The velocity of the water decreases, a hydraulic jump

occurs, and water leaves the basin with greatly reduced energy.

This is the purpose of the stilling basin. The stilling basin is a large, concrete, rectangular

structure into which the water flows upon exiting the outlet works to the baray. The concrete

basin easily can reduce the energy of the fast-moving water. The water is, in essence, held in a

large pool. On the baray side of the stilling basin (opposite side as where the water enters) is a

spillway set at an elevation of 26-m. See Figure APP – B.8 for a diagram of the stilling basin.

Dimensions and calculation for the stilling basin can be seen in Table APP – B.2. When water

reaches Elev. 26-m, it flows over the spillway and discharges into the baray at a velocity much

43

lower than the velocity at which it entered the basin. This greatly limits the potential erosion at

the area of the discharge.

f) Outlet Works from East Baray to River Siem Reap

The complete restoration of the western two-thirds of the East Baray and the intake pipeline to

charge the baray would be useless if the baray could not discharge water back into the River

Siem Reap during the dry season. As one may recall, one of the most general goals of our

project was to release stored water at a certain rate so the water surface elevation in the River

Siem Reap could remain relatively constant. Therefore, outlet works must be located somewhere

in the southwestern region of the baray to transport water from the baray back into the river.

The next section of this report will state the goals we have for this feature of the design, explore

design options and alternatives, present the selected final design, and expound on the

components of the final design.

(1) Goals for Design

The primary goal for the outlet works is the discharge of water from the baray to the river during

the dry season. This structure should be dependable, understandable, and fairly simple to use.

(2) Design Options and Alternatives

We evaluated two primary designs for the discharge of stored water into the river. The first

design option was a single, large spillway structure in the Western Dike of the East Baray. The

elevation of the spillway would be set at the maximum desired water level for the baray.

Consequently, any excess water would flow over the spillway and discharge into the river.

44

The second design option was an outlet works as the primary means of discharge and an

emergency spillway that would handle any unforeseen or emergency flows. The outlet works

would be a concrete structure that would transport water from the baray into a stilling basin. The

stilling basin would be the energy dissipation device to reduce the velocity of the water as it

came out the pipe. The emergency spillway would be similar to the spillway described in the

first design option, but in this case it likely could be significantly smaller.

(3) Selected Final Design

The design chosen as the means to release water from the baray to the River Siem Reap was the

second design option. The following paragraphs will describe the characteristics of the outlet

works, the emergency spillway, and the stilling basin, and safety measures will be presented for

the structures involved in operating the baray.

(4) Components of Final Design

(a) Outlet works

The outlet works is the most essential feature of this component of the design. It will have the

capacity manually to open and close depending on the water level in the baray. Three important

parameters determine the structure and function of the outlet works. First, the size of the intake

and pipe must be determined that will allow the desired flow rate to be released into the river.

Second, the materials with which the outlet works is constructed must be decided. Finally, the

location of the outlet works that will provide the maximum flow must be determined.

45

Using an example from the Design of Small Dams (Bureau of Reclamation) book, an outlet

works was designed to achieve the desired flow rate out of the baray. It was desired to provide a

flow rate to the river between one and six cubic meters per second. This flow rate, when

combined with the flow rate from the mountain dam, would provide enough flow to the river to

obtain the 2-feet per second velocity that would keep solids suspended and reduce sedimentation.

See Figure APP – B.9 in the Appendix for a detailed drawing and dimensions of the outlet

works. The intake portion will be 2-m long by 2-m wide by 1.5-m tall, and the pipe running

through the dike will be a 4-ft diameter pipe.

The outlet works must be constructed of concrete or an approved substitute. Concrete is a

durable, reliable material and is resistant – for the most part – to the erosive effects of flowing

water.

The outlet works should be located at the point in the Western dike closest to the River Siem

Reap. It is our understanding that the river winds and turns to a great extent. Therefore, to

minimize construction requirements, the outlet works should be built at the point in the dike

closest to the river. Ideally, in constructing the outlet works in this manner, the pipe through the

dike will discharge to the stilling basin, which will then discharge directly into the river.

(b) Emergency spillway

As the outlet works release water only when the gate is open, it would be necessary to construct

an emergency spillway that could release water should the water level in the baray rise too high

or too quickly. In the situation of a very heavy rain, excess baray water would flow over this

spillway and into the stilling basin, which would then discharge into the river as described in the

46

previous section. As the maximum water level in the baray should be at Elev. 29.0-m, the

spillway should be constructed at Elev. 29.0-m.

The emergency spillway should be located directly above the outlet works so the water can flow

into the stilling basin. The spillway also must be constructed of concrete since water will flow

over its crest. Significant erosion could occur and potential for much damage could arise if the

water flowed over a spillway constructed of gravel or other loose material.

Since the top of the dike is at Elev. 30-m and the spillway is at Elev. 29-m, there will be a 1-m

drop in the top of the dike. As one may recall, the restoration of the baray called for the road to

be repaired or a new road to be built on top of the dikes. This would present a conflict with the

emergency spillway unless a small bridge was constructed that would span the spillway and

allow traffic to cross it. Since the spillway would be constructed of concrete, the bridge also

should be built with concrete. The thickness of the concrete slab should be six (6) inches and a

concrete column should be built to support the bridge. See Figure APP – B.10 for a drawing of

the bridge over the emergency spillway.

(c) Stilling basin at outlet to river

For a maximum outlet flow rate of 6-m3/s and an outlet pipe diameter of 4-ft, water would be

exiting the baray and entering the river at a velocity over 5-m/s (18.5-km/hr, 11.5mph). At this

velocity, the water possesses an immense amount of energy and significant erosion would occur

at the point of discharge into the river. Therefore, an energy dissipation device must be included

that will reduce the velocity of the water. This is the purpose of the stilling basin. The stilling

basin is a large, concrete, rectangular structure into which the water flows upon exiting the pipe.

47

The basin easily can reduce the energy of the fast-moving water. On the river side of the stilling

basin (opposite side as where the water enters) is a spillway set at an elevation of 24-m. For a

diagram of the stilling basin, see Figure APP – B.8. This is the same stilling basin as the

structure used for the intake pipeline, except for the discharge elevation. When water reaches

Elev. 24-m, it flows over the spillway and discharges into the river at a velocity much lower than

the velocity at which it entered the basin. This greatly limits the potential erosion at the area of

the discharge.

(d) Water flow rate into river

Since the East Baray will be used to supplement the mountain dam, it was desired for the baray

to provide water flows between 1-m3/s and 6-m3/s. The maximum and minimum flow rates

would be achieved when the water level in the baray was the highest and lowest, respectively.

Assuming the dry season is approximately five (5) months long, it was desired to design an

outlet works that could provide a flow rate in the desired range for most of the dry season. If 90-

percent of the East Baray could be drained, it would take between 5 and 6 months to do so (the

first meter of water drains at 5.5 m3/s and takes 19 days; the second meter of water (down to

elev. 27) drains at 4.4 m3/s and takes 23 days; the third meter of water drains at 3.3 m3/s and

takes 30 days; the fourth meter of water (down to elev. 25) drains at 2.2 m3/s and takes 42 days;

any remaining water drains at about 1.0 m3/s and takes 71 days. This amounts to a total flow

time of 185 days (6.2 months)). However, it might not be desired to have such a variable flow

rate through the dry season since most of the water probably will be needed near the end of the

dry season. Therefore, the operators can adjust the gate so the baray releases about 2.0 m3/s all

the time (27,000,000 m3 at 2.0 m3/s = 156 days (5.2 months)).

48

6. Safety

a) Safety measures at intake structure and at outlet works into E. Baray

To ensure that fish and debris are not allowed into the pipeline, the intake structure should be

lined with trash racks and fish screens. These devices will keep the outlet works clean while not

greatly inhibiting the flow of water. As debris could build up on the trash racks, cleaning

maintenance frequently must be performed on the intake structure, preferably during the dry

season when minimal water will be flowing through the structure.

As the water will be flowing at a high rate upon exiting the outlet works, a chain-link fence

should be constructed to keep children and other individuals out of danger areas.

To ensure safety at the baray outlet works, annual or semi-annual inspections of the outlet works

and spillway should be made by the local authority. Note that inspections could be made at the

end of the dry season after the baray has discharged into the river and the river is at its lowest

level. Extra precautions should be taken on the first filling of the pipeline to ensure proper

functioning of the intake structure, pipeline, and outlet works.

b) Safety measures around outlet works into River Siem Reap

To ensure that debris and fish are not allowed into the outlet works, the intake structure will be

lined with trash racks and fish screens. These devices will keep the outlet works clean while not

greatly inhibiting the flow of water. As debris could build up on the trash racks, cleaning

maintenance must be performed on the intake structure each year, preferably during the dry

season when minimal water will be flowing through the structure.

49

In addition to the gated structure to control flow, stop logs or bulkhead slots will be constructed

at the intake structure. This will serve two primary purposes. First, it will provide back up for

the gate structure in case of failure of the gates. Second, it will enable dewatering of the pipe

while the gate is open to allow for inspection and maintenance.

As the water will be flowing at a high rate upon exiting the outlet works, a chain-link fence

should be constructed to keep children and other individuals out of danger areas.

In order to ensure safety at the baray outlet works, annual or semi-annual inspections of the

intake structure, conduit, and spillway should be made by the local authority. While inspecting

the conduit, the stop logs at the intake structure should be in place and the downstream gate open

to enable workers to inspect the inside of the pipe. Note that inspections also could be made at

the end of the dry season after then entire baray has discharged into the river.

Extra precautions should be taken on the first filling of the reservoir to ensure proper functioning

of all elements of the baray. Reservoir slopes should be checked periodically to ensure

vegetation remains. Algal growth in the reservoir also should be monitored and controlled.

7. Cost Analysis

Table B.1 shows that the approximate cost for the restoration of the baray if it was constructed in

the United States in 2005 would be $61.3 million. Because costs in Cambodia may differ

greatly, these numbers serve only as a guide. Table APP – B.5 shows a more detailed cost

estimate broken down by material, labor, equipment, and inclusions for contractor overhead and

50

profit. A further cost analysis could make adjustments by category to fit Cambodian costs. For

example, labor may be only fifty percent of what it is in the United States, while material may be

twice as expensive. Contingency, licensing, environmental, and engineering costs are all

included in the final cost.

Table B.1 Item Total Cost

ExcavationClay Excavation $42,460,757

New Dike ConstructionHauling, 5 km $2,065,156Compaction $217,259Roadway unknown

Intake Pipeline1.22 m Dia. Conc. Pipe $543,164Excavation / Backfill $12,343Gates $10,612Stilling Basin into BarayConcrete Slab $3,054Concrete Walls $4,775

Outlet Works to RiverConcrete Slab $458Concrete Walls $7161.22 m Dia. Conc. Pipe $20,891SpillwayOgee Weir $9,789Stilling BasinConcrete Slab $3,054Concrete Walls $4,775Bridge $80,546

Subtotal $45,437,348Contingency, 15% $6,815,602Licensing, 5% $2,271,867Environmental, 5% $2,271,867Engineering, 10% $4,543,735Total $61,340,420

51

C. Mountain Dam

1. Purpose

The purpose of this dam is to create a reservoir that will store water from the wet season for use

in the dry season, and to store water from wet years for use in drier years. The reservoir storage

will complement the storage gained from the restoration of the East Baray, and together they will

help maintain a more constant water level in the channel. In the future, Siem Reap may want to

raise the dam and enlarge the reservoir to include more storage for irrigation and water supply, or

consider its use for hydroelectric power generation.

2. Site

The site for the dam will be north of Siem Reap in the Kulen Mountains. This allows for the use

of the steep mountain slopes as reservoir sides and therefore allows for a deeper reservoir. The

deeper the reservoir, the higher the quality of water contained therein. In order to determine the

necessary reservoir volume, calculations were done to determine the amount of water that would

flow out of the river into Lake Tonle Sap during the dry season if the river flowed at 2 ft/s (or .61

m/s, see above).

According to the study,

Closure of a gorge on the left-hand branch, or a dam a short distance downstream thereof

still on the left-hand branch, or one on the right-hand branch around the emergence from

the mountains, or a dam around the confluence seem to offer potential alternatives (64).

52

The potential sites on the left-hand branch were deemed unfeasible. Too little water would be

impounded at too great a cost. Also, the lower abutment heights and therefore shallower

canyons would mean more surface area per volume, which means more land destroyed due to the

reservoir and also more evaporation and seepage losses. A dam around the confluence, while

being fed by the greatest drainage area, has similar problems to dams on the left-hand branch.

Much of the additional water would be lost over the spillway, and flooding would only be

attenuated to a small degree.

The chosen site was on the right-hand branch around the emergence from the mountains. Three

possible sites were evaluated based on crest length, structural height of the embankment,

reservoir capacity, and land use. The easternmost site was chosen as the optimal site. Given this

site, the crest length would be approximately 1113 m, the maximum structural height would be

59.5 m, and the reservoir capacity would be 155 million m3. This is satisfactory in light of the

required storage capacity of 155 million m3. The elevation-area data of site C are shown in

Table APP – C.6.

3. Social and Environmental Considerations

Before construction takes place, an extensive environmental study would have to be done. This

study should include, but not be limited to, a determination of fish species present, their

migratory patterns and preferred flow regimes, reservoir temperature management and

stratification, existing silt composition and load, impact on disease, and plant and animal species

present on existing dry land. Some of the potential impacts of the dam may be disastrous to the

region. For example, normal river scouring would no longer be counteracted with as much silt,

53

which would cause erosion of the banks. Also, minerals present in the silt may help fertilize the

soil downstream, and the loss of these minerals would be detrimental to agriculture.

To accommodate the passage of fish, a fish ladder has been included in the design of the dam,

the details of which would follow an environmental study’s listing of specific fish species

requirements. Screens on intakes have also been included to keep fish from being sucked into

these structures. A reservoir water level management plan may want to be developed to help

increase populations of desirable species of aquatic plants and animals while limiting populations

of undesirable species.

In some cases around the world, earthquakes have found to be caused by the increase in pore

water pressure caused by the reservoir. Only one major earthquake has occurred under a

reservoir of less than 100 meters, and all of the earthquakes were in existing fault zones.

Because the proposed location is not in a fault zone and is less than 100 meters high, it is very

unlikely that this would be an issue.8

Following construction, a study should be done to determine the environmental impact of the

dam.

The social considerations of the construction of the dam include the displacement of people

living in the proposed reservoir site and the psychological impact of living in the shadow of a

large dam. Appropriate measures should be taken to ensure the safe and ethical movement of

8 Goldsmith, Edward and Nicholas Hildyard. The Social and Environmental Effects of Large Dams. San Francisco: Sierra Club Books, 1984. Page 113-119.

54

these people. Also, safety measures should be communicated to the people living downstream of

the dam to alleviate potential fears.

4. Hydrology

Figure APP – C.2 shows the approximate delineation of this mountain watershed. The area of

the watershed is 121.9 km2. A hydrologic model for the Siem Reap area was constructed using

HEC-HMS, the U.S.A.C.E. Hydrologic Modeling System. The basin model is shown in Figure

C.1. For the purposes of the dam, the focus was on the mountain watershed, upstream reach, and

reservoir.

Figure C.1 HEC-HMS schematic showing the watersheds, reaches, reservoir, junction, and

sink (Lake Tonle Sap).

For the mountain watershed, the SCS curve number was approximated as 50% woods at 83 and

50% meadow at 78, for a total SCS curve number of about 80. The SCS lag was estimated at 15

55

minutes. A baseflow of 10 m3/s in the river upstream of the dam was assumed in lieu of actual

data.

For the upstream reach, the Muskingum K was estimated at 2 hours, the Muskingum x at 0.004,

and 4 subreaches were modeled. These numbers would have to be calibrated on-site for a better

model.

For the reservoir, an outlet orifice was set at elevation 141 (9 m above the bottom of the

reservoir, to allow for sedimentation), the cross-sectional area was set at .567 m (for a .85 m

diameter tunnel), and the discharge coefficient was set at 0.63, the average of the coefficients for

maximum and minimum losses (see Table APP - C.7). An ogee spillway was also defined. The

approach depth was 3 m, the approach loss 0 m, the crest elevation 189.5 m, the crest width 14.1

m, the apron elevation 188.5 m, the apron width 14.1 m, and the design head 1.5 m. No

overflow or dam breaks were modeled. The initial reservoir elevation was set at the spillway

elevation for the worst case, which was 189.5 m.

The meteorological model was then defined for the design storm. A frequency storm method

was used. The exceedance probability was 4%, the maximum intensity duration 5 minutes, the

storm duration 1 hour, the peak center 50%, and the storm area 670 km (the size of the entire

Siem Reap River watershed). The duration-precipitation data was are shown in Table C.1. For

this model, evapotranspiration was ignored due to the short time-span. Evaporation of the

reservoir on an annual basis is addressed later in the report.

56

Table C.1 Design storm parameters.9

Duration (min)

Precipitation (mm)

5 20 15 45 60 120

The results of the model simulation are shown in Figure C.2. The peak inflow was 500.6 m3/s,

the peak outflow was 18.49 m3/s, the peak storage was 152,645,000 cubic meters, and the peak

elevation was 189.92 m, which is below the maximum allowable reservoir elevation of 190 m.

Figure C.2 Reservoir summary table.

Assuming 100 storms annually (about one storm every other day in the wet season), the annual

surface runoff was calculated to be 1622 mm, based on an annual rainfall of 1885.3 mm. Given

a watershed area of 121.9 km2, this makes for a total annual reservoir inflow of 197.8 million

cubic meters.

9 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 13.

57

Evaporation is estimated at about 1500 mm/yr for reservoirs in the area.10 This will reduce the

height of the reservoir by 1.5 meters over the course of a year, with a maximum loss of

approximately 10 million cubic meters of water.

5. Design

Below is a plan and profile view of the proposed dam. The subsections go into more detail on

the design of each component.

Figure C.3 Plan view (top) and profile cross-section (bottom) of dam.

10 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 14.

58

a) Material

Three types of material were considered for the dam: earth, rock, and concrete. Table C.2 shows

a decision matrix comparing the three types. The lower numbers were preferable, so the result

was the decision to design a rockfill dam.

Table C.2 Dam type decision matrix. Weight 25 25 15 15 20 100

Foundation Requirements Cost

Complexity of Design

Climate Concerns

Material Availability Total Weighted Total

Earthfill 1 1 2 3 1.5 8.5 155Rockfill 2 1 1 1 1.5 6.5 135

Concrete Gravity 3 3 3 1 3 13 270

Foundation requirements are more stringent than earthfill dams, so an in-depth geological

investigation would have to be done to determine if the foundation would be adequate for a

rockfill dam. While comparable in cost, an earthfill dam would be difficult to construct if the

construction was to last more than the 5 month dry season as the wet season’s rains would

destroy unfinished earthwork. Material availability would depend on site geological

investigations of adequate rock. Either earth or rock may be more plentiful and available around

the site, but a more in-depth site study would have to be done to determine this.

b) Foundation

Foundation analysis and design is a vital component to the design of the dam. Because of the

lack of geotechnical data, foundation concerns were not addressed in this design. A geotechnical

investigation would need to be conducted to determine the depth of bedrock, character of

bedrock, and soil characteristics in light of the final settling requirements of the embankment.

Following seepage calculations, a design of the foundation and proper construction preparation

plans could be created.

59

c) Reservoir

The fetch (the distance over which the wind can act on a body of water; in this case, the normal

distance from the windward shore to the crest) was determined to be 4.5 km, or 2.8 mi. Thus, the

required freeboard was set at 7 ft based on Table APP – C.4. A coping wall was added to the

crest to lower the freeboard requirement to 5 ft, or 1.5 m. This makes for a maximum reservoir

elevation of 190 m and a minimum reservoir elevation of 132 m, making a maximum reservoir

depth of 58 m just upstream of the embankment.

The volume of the reservoir had to be increased enough to allow for 100 years of sedimentation

along the bottom. The sediment load for the portion of the Siem Reap river near the temples is

20 tons/km2/yr. The sedimentation in the reservoir should be much lower, but based on this

conservative number, 820,000 m3 of capacity should be subtracted from the total reservoir

volume due to the 100 year sedimentation level.

Seepage out of the reservoir and under the dam is a big factor that this design has ignored. This

is for several reasons. First and foremost, inadequate data on soil and geological properties,

especially hydraulic conductivity, soil type and layer thickness, and depth of bedrock, makes

calculation nearly impossible. Second, inadequate data on water table height makes seepage

losses difficult to calculate. Because seepage can vary so greatly, even an estimate can be very

inaccurate. Seepage calculations would have to be done before the dam was constructed.

There are few sources of pollution known in the proposed reservoir watershed. The area is

mostly uninhabited and undeveloped.

60

d) Embankment and Membrane

The first decision to make for the embankment was where to place the impervious membrane.

The two options were to use an upstream membrane or a central membrane. Table APP – C.1

shows the pros and cons for a central core and upstream membrane configuration. Based on

these, an upstream membrane was chosen.

Once the upstream membrane configuration was chose, the material was chosen. Table APP –

C.2 shows the pros and cons of the three most common upstream membrane materials.

At the base of the membrane a cutoff wall was included to prevent seepage in the upper few feet

of the foundation, to allow for grouting, to provide a watertight seal with the membrane, and to

support the downward thrust of the membrane. Figure APP – C.3 shows a detail of the concrete

membrane at the cutoff wall. Once a geotechnical survey is done, seepage and structural support

calculations can be used to determine the height of the cutoff wall. For our purposes, we used a

height of 6 ft, a typical value for dams this size.

As mentioned above, the choice of site dictated that the structural height of the dam be 59.5 m

and that the length of the crest be 1113 ft, the distance between the abutments at the elevation of

the crest. The slope of the upstream and downstream embankments was set at 1.3:1, a typical

value for rockfill dams. The total embankment volume was found with Autodesk Inventor to be

2.31 million m3.

61

The embankment was then divided into three zones. Figure APP -C.4 shows a typical cross

section of the embankment with these three zones shown and described. Gradation requirements

were set according to general guidelines. Table APP – C.5 shows the requirements for the three

zones. The type of rock used for these zones will be primarily sandstone11 quarried from the

mountains. The effect of quarry blasting methods on the gradation of the rock should be

examined and the methods revised to meet with requirements.

Accepted construction techniques should be practiced especially in the construction of the heel

of the dam. Grouting will be necessary to add stability and reduce seepage under the dam. The

depth and degree of grouting should be determined based on seepage calculations and

geotechnical data following an investigation.

e) Spillway

Based on the results of the hydrological model (see Hydrology), the design storm was

determined to cause an additional inflow of 501 m3/s and a peak outflow of 18.5 m3/s, 7.2 m3/s

of which are taken by the spillway. However, the spillway should be designed to handle a total

flood-flow of 150 m3/s. This is because flooding on this order takes place downstream near the

temples12 and also because spillways typically should have approximately ten times their

associated outlet works’ capacity. The hydrologic model is only one storm, while a spillway for

a reservoir this size should be sized for a flood-conducive season, not just a single storm. Table

APP – C.3 shows the pros and cons for the available spillway configurations.

11 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 8. 12 Garami, Ferene and Istvan Kertai. “Water Management in the Angkor Area.” Angkor Foundation. Budapest, Hungary: 1993. Page 17.

62

Based on this, the chute spillway with an uncontrolled ogee crest configuration was chosen.

The value of the surcharge head was set at 1 m. The height of the crest was assumed to be 2 m.

Figure APP – C.1 shows the value of the discharge coefficient for different weir and surcharge

head combinations, and based on this the discharge coefficient was determined to be 3.7. The

required length of the crest was then calculated to be 40.5 m using the weir equation.

The chute width was then set at 5 m. At maximum flow, the gradually varied flow profile was

modeled along the length of the chute as shown in Figures APP - C.7-C.10. The chute then

empties into a widening section where it is joined by the outlet works flow in order to widen to

the width of the stilling basin and river. Coupled with the outlet works maximum flow, the final

depth and velocity at the stilling basin were calculated to be .83 m and 20.0 m/s, respectively.

The freeboard required was calculated to be 2.54 ft.

The design of the stilling basin is described in a subsequent section.

f) Outlet Works

The elevation of the inlet structure was desired to be as low as possible to allow for maximum

reservoir drawdown, while still being high enough to be above the 100 year sedimentation level.

Thus, the invert elevation of the inlet structure was set at 141 m. The configuration was chosen

to be a submerged structure with trashracks, as shown in Figure APP – C.5. Fishscreens will

probably be necessary following an environmental study of the area, but were not included in

this design.

63

Outlet works configurations are typically either cut-and-cover conduits running through or

alongside the embankment, or tunnels bored through one of the abutments. Tunneling can

usually be more cost-effective, but requires favorable rock and soil conditions. Following a

geological and geotechnical survey of the site, an economical analysis should be done to

determine which option would be most cost effective. Because of the relatively low outlet flow

rate demanded of the outlet works and an uncertainty of the surrounding conditions, a smaller

cut-and-cover conduit flowing under pressure was chosen for this analysis.

As described in the channel section earlier in the report, the required flow rate was 8 m3/s. The

diameter of the pipe was adjusted in the HMS model until the flow rate for the first 125 million

m3 was at least this value, which meant a 0.85 m diameter conduit. Hand calculations verified

this and are shown in Table APP – C.7. The rating curve for the reservoir based on this conduit

is shown in Figure C.4. The final maximum velocity is 27.4 m/s, and this empties into the

widening section where it joins the spillway flow before emptying into the stilling basin.

64

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

132 142 152 162 172 182

Elevation (m)

Out

flow

(cm

s)

0

20000000

40000000

60000000

80000000

100000000

120000000

140000000

160000000

180000000

Res

ervo

ir Vo

lum

e (m

^3)

OutflowVolume

30000000

Figure C.4 Reservoir rating curve and associated volumes.

g) Stilling Basin13

Both the outlet works and spillway empty into the hydraulic jump stilling basin. The basin will

be made of concrete and will have vertical walls. The worksheet design of the stilling basin is

shown in Table APP – C.10. The width of the basin was set at approximately the width of the

tailwater, 30 feet. The initial depth is 0.83 m and the initial velocity at maximum flow rates is

20.0 m/s, as shown in Figure APP – C.10. The final depth was then calculated to be 7.83 m.

This makes the initial tailwater elevation equal to 139.3 m. The length factor was determined

13 Calculations done in this section were according to equations set forth in: (design of small dams)

65

according to Figure APP – C.11 to be 4.15. Therefore the required length of the basin was

calculated to be 32.5 m. Figure APP – C.12 shows a cross section for a typical hydraulic jump

stilling basin. The size of the chute blocks and dentated sill was then calculated, so 25 chute

blocks and 18 dentated sill blocks are required. The required freeboard was calculated to be 2.78

m.

h) Instrumentation

Key

SP - Survey point TS - VW Temperature sensor

I - Inclinometer W - V-Notch Weir PC - VW Pressure Cell

PZ - Piezometer (single or string) EX - Extensometers SC - Settlement Cell WL - Water Level Meter SM - Strong Motion Accelerograph

Figure C.5 Rockfill dam showing placement of instrumentation.14 Survey points are surface-mounted prisms that will be read by automated or manual theodolites.

VW Temperature Sensors are high resolution Vibrating Wire temperature sensors that allow

remote readings and data logging.

Inclinometers are used to measure lateral movements in the dam.

A V-Notch Weir accurately measures water flow, and is usually used to check seepage

14 from http://www.soil.co.uk/AppEmbDam.htm

66

VW Pressure Cells monitor the total pressure in a soil mass; in other words, the combined

pressure of the soil and the pore water within the soil.

Piezometers measure pore water pressure.

Extensometers are used to identify movements of the dam base or the ground at the base. Rod

extensometers are useful, as they give highly accurate readings, even at great depths.

Settlement Cells measure settlement.

Water Level Meters are simple Staff Gauge Boards fixed to the upstream face of the dam.

Strong Motion Accelerographs are for monitoring violent earth tremors that might occur in the

event of an earthquake.

6. Safety

In order to ensure safety at the dam, annual or semi-annual inspections should be made by the

local authority. Table C.3 shows items that should be inspected. In addition, an underwater

inspection should be done every six years.

Table C.3 Items to be inspected annually or semi-annually.

Operations Dam Attendance at Dam Upstream Face Written Instructions Downstream Face Communications Crest Auxiliary Power Abutments Access Roads Seepage and Drainage Landslides Instruments

Spillway Outlet Works

Control Structures Inlet Structure Chute Outlet Conduit Stilling Basin Control Facilities Outlet Channel Chute Bridge Stilling Basin Outlet Channel

67

Extra precautions should be taken on the first filling of the reservoir to ensure proper functioning

of all elements of the dam. Reservoir slopes should be periodically checked to ensure vegetation

remains. Algal growth in the reservoir should also be monitored and controlled.

At least two operators should be in attendance at all times. A downstream warning and

communication system should be put in place to make sure people are notified early enough in

case of dam failure. A detailed Emergency Preparedness Plan (EPP) should be prepared and

submitted to the authorities before construction is begun.

Security must also be maintained around the dam at all times. Due to the instability in the

region, rebels may attempt to sabotage the dam to embarrass government officials or to have

their demands met. The degree of this should be determined based on present instability.

7. Cost Analysis

Table C.4 shows that the approximate cost for the dam if it was constructed in the United States

in 2005 would be $115.0 million. Because costs in Cambodia may differ greatly, these numbers

serve only as a guide. Table APP – C.9 shows a more detailed cost estimate broken down by

material, labor, equipment, and inclusions for contractor overhead and profit. A further cost

analysis could make adjustments by category to fit Cambodian costs. For example, labor may be

only fifty percent of what it is in the United States, while material may be twice as expensive.

Contingency, licensing, environmental, and engineering costs are all included in the final cost.

Table C.4 Cost summary. Item Total Cost Diversion $1,591,812

68

Embankment Rock Excavation $62,124,363Hauling, 5 km $14,268,563Compaction $6,476,966Bridge $27,576Roadway $97,302 Outlet Works .85 m Diameter Pipe $40,678Gates $10,612 Spillway Ogee Weir $43,512Concrete Slab $7,436Concrete Walls $87,906 Stilling Basin Concrete Slab $5,039Concrete Walls $15,948 Reservoir Preparation $212,242 Instrumentation $159,181 Subtotal $85,169,135Contingency, 15% $12,775,370Licensing, 5% $4,258,457Environmental, 5% $4,258,457Engineering, 10% $8,516,914Total $114,978,332

V. Discussion

A. Coordination between mountain dam and East Baray

1. Necessity of baray and dam

The East Baray can hold 30,000,000 m3 of water, and the mountain dam can hold 155,000,000

m3 of water at full capacity. However, with seepage and evapotranspiration losses, the volume

available for the dry season would be less than this. Also, the lower 30,000,000 m3 provide a

flow rate of less than 8 m3/s, so the elevation associated with this volume this will be the

maximum drawdown level of the reservoir (see Figure C.4). Thus, the effective volume

69

available in the reservoir is 125,000,000 m3. As the River Siem Reap requires 155,000,000 m3

of water to remain at the desired water level for the entire dry season, the dam storage can

provide for most of the dry season flows, but the baray storage is required to assist with the dry

season. Therefore, the two storage facilities must be used in conjunction with each other to

supply the River Siem Reap with water for the entire year.

During the wet season, the reservoir behind the mountain dam will fill due to rainfall and runoff

from the entire mountain watershed. In addition, the baray will fill to a certain extent due to

rainfall. However, it cannot be assumed that the baray will fill completely due to rainfall.

Ideally, more water will fall and drain into the reservoir than it can hold, causing the dam to

release enough water to fill the baray by the end of the wet season. This extra water from the

dam will flow down the river and be captured by the intake structure for the baray, and the baray

will be filled. If the area receives average rainfall, both the reservoir behind the mountain dam

and the East Baray should be filled with water during the wet season.

2. Controls

As described in somewhat detail in a previous section, the design of the mountain dam and baray

must include controls to regulate what water is released and when it will be released. These

controls primarily are gates, but valves may be included if necessary. The basic operating

scheme for the mountain dam, baray intake structure, and baray outlet works is as follows:

(1) Mountain Dam

The outlet works is sized such that the maximum flow is around 11 m3/s. If less flow is required

for any reason, a gate is located midway through the embankment. This gate will be operated by

70

a hand crank (or hydraulic chain, depending on cost and availability of local expertise) and can

limit flow to any amount less than the maximum flow rate. It may be determined with better

flood data that the outlet works should be larger with one gate closed most of the time in order to

allow for greater flows if necessary. The gate will be closed upon the first filling of the dam

until the level reaches 161 m, the minimum expected water surface of the reservoir.

(2) Baray Intake Structure

The gates on the baray intake structure should be open during the rainy season in order for the

baray to fill with water (see the “Water flow control into East Baray” section above). The gates

on the baray outlet works should be closed during the rainy season in order for the baray to fill

with water (see the “Water flow rate into river” section above). If the gates remain closed for the

entire rainy season, excess water entering the baray will flow over the emergency spillway to

prevent any flooding. During the dry season, the gates can either be permanently opened or

opened periodically to provide flow to the River Siem Reap.

Note: the final decision on when to open and close all the gates should be made by the public

works owners and operators.

B. Conclusions

The final results of our project can be seen in Figure APP – D.4 which is a representative flow

chart of the hydraulic system proposed by our project. As described in detail in the previous

sections of this report, the component costs of the system are as follows: The new canal would

cost approximately $86,500,000 U.S., the restoration of the baray would cost about $61,300,000

71

U.S., and the mountain dam would about $115,000,000 U.S. This brings the total project cost to

approximately $262,800,000 U.S.

VI. Recommendations

Further projects could address the following:

• A more in-depth design of the dam alone. In order to do this, an on-site geological and

geotechnical investigation would have to be done, as well as the acquisition of more

detailed hydrology data, data on the availability of materials, and the acquisition of better

GIS and site details. This would allow for better flood prediction and spillway design,

seepage calculations relating to embankment stability and reservoir storage, as well as

possible change of site based on local habitation or site characteristics.

• A design of a dam for a location other than Cambodia, perhaps in the United States.

• Design and planning of dam removal for a local river.

• Consideration of hydroelectric power generation at the dam, and perhaps a design of a

hydroelectric power plant.

• A design that would involve the restoration of the North Baray.

• Consideration of several smaller dams at various sites instead of a single, large dam.

• An analysis of the specific effects our project would have on water quality, native fish

and wildlife species, and erosion concerns.

• The design of a water treatment plant and water distribution system, or a wastewater

treatment plant and collection system.

72

In addition, simply acquiring more data would allow a more detailed design and cost estimate.

All of these projects would require that data be collected early on, that communication improve

between Calvin and APSARA, Handong, and JICA.

VI. Acknowledgements The members of team 15 would like to thank Professor Hackchul Kim of Handong Global

University for the idea of this project and for all his work in the area; Professor Leonard DeRooy

for his communication with Professor Kim as well as some resources such as hydrologic studies,

GIS, and photos; Professor Hoeksema for his help with hydraulic and hydrologic issues; Roger

Lamer for his general consultation; Brian Katerberg for his help with Autodesk Inventor; team 6

for donating Pex pipe for the model; and our wonderful ladies, Audra, Mary, and Tracy, for

supporting us all year long.

73

Appendix

A. CANAL ............................................................................................................75

B. BARAY............................................................................................................77

C. MOUNTAIN DAM.............................................................................................89

D. GENERAL ..................................................................................................... 103

E. SCHEDULE ................................................................................................... 107

F. BUDGET ....................................................................................................... 108

74

A. Canal Table APP - A.1 Cost data and totals.

Figure APP - A.1 Calculation of D30

75

Figure APP - A.2 Embankment calculations.

76

B. Baray

Figure APP - B.1 GIS rendering of site location of East Baray

1200 m from the Western Dike

3000 m from the Western Dike

77

3000 m from the Eastern Dike

1200 m from the Eastern Dike

Figure APP - B.2 Cross-sections at specified locations in the East Baray

Table APP - B.1 Monthly rainfall distribution in Siem Reap.

Month Rainfall(mm)* Jan 6.5 Feb 4.3 March 36.6 April 55 May 188 June 209 July 166 Aug 226 Sept 264 Oct 215 Nov 49.8 Dec 13 Total 1434

*Based on Data from Department of Agriculture From the Mekong River Commission Secretariat “Natural Resources Based Development Strategy for the Tonle Sap Area, Cambodia, 1. Environment in the Tonle Sap Area.” (Table 2, pg. 5):

78

Figure APP - B.3 Typical cross-section of new dike that will divide the East Baray

and allow for water storage in the western two-thirds.

Figure APP - B.4 Design Option 1: Diversion structure at River Siem Reap to fill the

Baray

79

Figure APP - B.5 Schematic of intake structure in River Siem Reap

80

Figure APP - B.6 Location of 4-ft diameter concrete pipeline that will transport

water from the River Siem Reap to the East Baray.

81

Figure APP - B.7 Outlet works to discharge water from the concrete pipeline into

the East Baray

82

Figure APP - B.8 Diagram of stilling basin

Table APP - B.2 Values for stilling basin variables

g 9.806 D1 1.142944 V1 3.74 D2 1.32151 Required Tailwater 1.32151 Froude No. 1.116492 Length Factor (fig 9-42) 3.4 Length 4.493132 m Tailwater Depth 3 m

83

Chute Blocks TW Depth/d1 (fig 9-42) 2.63 d1 1.140684 Dentated Sill TW Depth/d2 1.05 d2 2.857143 s2 0.428571 w2 0.428571 h2 0.571429 Width of basin is arbitrary

Figure APP - B.9 Outlet works to discharge water from the East Baray to the River

84

Figure APP - B.10 Schematic of concrete roadway bridge over spillway

85

Table APP - B.3 Intake pipeline hydraulic calculations worksheet Design of Intake Structure from River Siem Reap to E. Baray

g 9.806 m/s2

Diameter of Feed pipe 4 ft length = 2 mDiameter of Tunnel 1.22 m width = 2 mArea of Tunnel 1.17 m^2 height = 1.5 m

Gate Cd 0.96trashrack

area = 10 m2trash rack on top and 2 sides - not front or back

Manning's n = 0.013 Manning's n = 0.008

ElementLength of Friction (m)

Hydraulic Radius (m)

Area (m^2) (a1/ax)^2 Loss Type Loss Coefficient

(a1/ax)^2 times Coefficient

Loss Coefficient

(a1/ax)^2 times Coefficient

Trashrack Gross 10.0 1.9E-02 Trashrack 0.345 0.007 0.000 0.000Net 8.5

Entrance 3.0 1.5E-01 Entrance 0.200 0.030 0.200 0.0305 2.4 3.0 1.5E-01 Friction 0.008 0.001 0.003 0.000

3.0 1.5E-01 Contraction 0.100 0.015 0.100 0.015Transition 1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

0 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.0001.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

Upstream Tunnel 1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

950 1.22 1.2 1.0E+00 Friction 3.587 3.587 1.358 1.3581.2 1.0E+00 30 deg bend 0.070 0.070 0.070 0.0701.2 1.0E+00 Expansion 0.200 0.200 0.200 0.200

Transition 1.2 1.0E+00 Expansion 0.200 0.200 0.200 0.2000 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.000

1.2 1.0E+00 Entrance 0.200 0.200 0.200 0.2000 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.000

1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100Gates 0.8 2.1E+00 Contraction 0.100 0.209 0.100 0.209

5 0.9 0.8 2.1E+00 Friction 0.028 0.059 0.011 0.0220.8 2.1E+00 Gates 0.085 0.177 0.085 0.1770.8 2.1E+00 Exit 1.000 2.086 1.000 2.086

Total = 7.2420 4.9693

Number of Gates 1.00Width of Gates 1.00Height of Gates 1.00Water Depth just downstream of Gates 0.96Water Surface Elevation at Intake Structure 30Water Surface Elevation in Baray 25.5 max water surface elevation is 29m

Total Head needed to overcome max head loss to produce discharge 3.54Max Flow Rate (max losses) 3.61 m^3/sMax Flow Rate (min losses) 4.36 m^3/s

Max Velocity (max losses) 3.10 m/sMax Velocity (min losses) 3.74 m/s

Dimensions of intake structure

Max Losses Min Losses

86

Table APP - B.4 Outlet works hydraulic calculations worksheet Design of Outlet Works from E. Baray to River Siem Reap

g 9.806 m/s2

Diameter of Feed pipe 4 ft length = 2 mDiameter of Tunnel 1.22 m width = 2 mArea of Tunnel 1.17 m^2 height = 1.5 m

Gate Cd 0.96trashrack

area = 10 m2trash rack on top and 2 sides - not front or back

Manning's n = 0.013 Manning's n = 0.008

ElementLength of Friction (m)

Hydraulic Radius (m)

Area (m^2) (a1/ax)^2 Loss Type Loss Coefficient

(a1/ax)^2 times Coefficient

Loss Coefficient

(a1/ax)^2 times Coefficient

Trashrack Gross 10.0 1.9E-02 Trashrack 0.345 0.007 0.000 0.000Net 8.5

Entrance 3.0 1.5E-01 Entrance 0.200 0.030 0.200 0.0302 2.4 3.0 1.5E-01 Friction 0.003 0.000 0.001 0.000

3.0 1.5E-01 Contraction 0.100 0.015 0.100 0.015Transition 1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

0 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.0001.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

Upstream Tunnel 1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100

130 1.22 1.2 1.0E+00 Friction 0.491 0.491 0.186 0.1861.2 1.0E+00 30 deg bend 0.070 0.070 0.070 0.0701.2 1.0E+00 Expansion 0.200 0.200 0.200 0.200

Transition 1.2 1.0E+00 Expansion 0.200 0.200 0.200 0.2000 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.000

1.2 1.0E+00 Entrance 0.200 0.200 0.200 0.2000 1.22 1.2 1.0E+00 Friction 0.000 0.000 0.000 0.000

1.2 1.0E+00 Contraction 0.100 0.100 0.100 0.100Gates 0.8 2.1E+00 Contraction 0.100 0.209 0.100 0.209

1 0.9 0.8 2.1E+00 Friction 0.006 0.012 0.002 0.0040.8 2.1E+00 Gates 0.085 0.177 0.085 0.1770.8 2.1E+00 Exit 1.000 2.086 1.000 2.086

Total = 4.0977 3.7786

Number of Gates 1.00Width of Gates 1.00Height of Gates 1Water Depth just downstream of Gates 0.96Maximum Baray Water Elevation 29Tunnel Invert at Gates 24

4.04Max Flow Rate (max losses) 5.13 m^3/sMax Flow Rate (min losses) 5.35 m^3/s

Max Velocity (max losses) 4.40 m/sMax Velocity (min losses) 4.58 m/s

Total Head needed to overcome max head loss to produce discharge

Dimensions of intake structure

Max Losses Min Losses

87

Table APP - B.5 Detailed cost breakdown for restoration of E. Baray

rIte

mQu

antity

(SI)

Unit (

SI)Co

nvers

ion Fa

ctoQu

anitit

y (En

gl)Un

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cl. O

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tion

Clay E

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ation

504,6

00,00

0CM

1.308

6016

800

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01.3

74.1

45.5

16.6

50.0

01.4

54.3

95.8

57.0

6$4

2,460

,757

New

Dike C

onstr

uctio

nHa

uling,

5 km

5317

2,000

CM1.3

0822

4976

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2.50

4.42

6.92

8.65

2.65

4.69

7.34

9.18

$2,06

5,156

Comp

actio

n48

172,0

00CM

1.308

2249

76CY

00.2

30.5

10.7

40.9

10.2

40.5

40.7

90.9

7$2

17,25

9Ro

adwa

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line1.2

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ia. Co

nc. P

ipe63

1,300

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8142

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62.00

22.50

15.20

99.70

120.0

065

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.1310

5.80

127.3

4$5

43,16

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tion /

Back

fill49

5,200

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0868

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0.00

0.45

0.93

1.38

1.71

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0.48

0.99

1.46

1.81

$12,3

43Ga

tes1

EACH

1.000

1EA

CH10

000.0

010

000.0

010

612.0

810

612.0

8$1

0,612

Stillin

g Bas

in int

o Bara

yCo

ncret

e Slab

20CM

1.308

26CY

77.00

12.45

5.80

18.25

110.0

081

.7113

.216.1

619

.3711

6.73

$3,05

4Co

ncret

e Walls

20CM

1.308

26CY

82.50

48.00

5.75

136.2

517

2.00

87.55

50.94

6.10

144.5

918

2.53

$4,77

5

Outle

t Work

s to R

iver

Conc

rete S

lab3

CM1.3

084

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.2511

0.00

81.71

13.21

6.16

19.37

116.7

3$4

58Co

ncret

e Walls

3CM

1.308

4CY

82.50

48.00

5.75

136.2

517

2.00

87.55

50.94

6.10

144.5

918

2.53

$716

1.22 m

Dia.

Conc

. Pipe

6350

LM3.2

8116

4LF

62.00

22.50

15.20

99.70

120.0

065

.7923

.8816

.1310

5.80

127.3

4$2

0,891

Spillw

ayOg

ee W

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.5048

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513

6.25

172.0

087

.5550

.946.1

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4.59

182.5

3$0

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g Bas

inCo

ncret

e Slab

20CM

1.308

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77.00

12.45

5.80

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110.0

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6.73

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ncret

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20CM

1.308

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82.50

48.00

5.75

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87.55

50.94

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1100

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5,427

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$2,27

1,378

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10%

$4,54

2,756

Total

$61,3

27,20

6

2002

Bare

Costs

2005

Bare

Costs

(ass

uming

2% an

nual

inflat

ion ra

te)

88

C. Mountain Dam

Figure APP - C.1 Graph for weir coefficient determination from crest properties.

89

Figure APP - C.2 Topographical map showing location of mountain dam, reservoir, and

watershed boundry.

DAM

RESERVOIR

WATERSHED BOUNDRY

90

Figure APP - C.3 Detail of heel of dam showing cutoff wall.

Figure APP - C.4 Cross section of embankment showing rockfill zones.

91

Figure APP - C.5 Details of outlet works intake structure.

92

Figure APP - C.6 Details of gate at midway of outlet works.

93

Figure APP - C.7 Spillway profile showing critical water surface, water surface, and chute

bottom.

Figure APP - C.8 Properties of spillway chute at crest (STA. 80.85) under design flood

conditions.

94

Figure APP - C.9 Properties of spillway chute at beginning of widening section (STA. 0)

under design flood conditions.

Figure APP - C.10 Properties of spillway chute at end of widening section (STA. -10.0,

entrance to stilling basin) under design flood conditions.

95

Figure APP - C.11 Stilling basin characteristics for Froude numbers above 4.5.

96

Figure APP - C.12 Typical hydraulic jump stilling basin.

Table APP - C.1 Membrane type decision table. Type of Membrane

Description Pros and Cons Capital Cost

O&M Cost

Central Core

Impervious earth membrane located vertically in the center of the embankment

Pros--protected from the weather, less total area exposed to water; Cons--inaccessible for maintenance/inspection, lower stability

Same More Expensive

Upstream Membrane

Concrete, asphalt, or steel membrane located on the upstream slop of the embankment

Pros--different construction stage, slope protection, higher stability, accessible for maintenance, easy to raise dam, no impervious soil required; Cons--not protected from the weather, larger surface area exposed to water

Same Less Expensive

97

Table APP - C.2 Membrane material decision table. Material Pros and Cons Capital Cost O&M Cost Concrete Pros--wide range of acceptable

gradation, high material availability, experienced construction method; Cons--low settlement toleration

Low Moderate

Asphaltic Concrete

Pros--Can tolerate larger settlements than concrete; Cons--more stringent gradation requirements than concrete, construction must be done more carefully to avoid failure

Moderate Moderate if initial construction is good, high otherwise

Steel Pros--Can tolerate largest settlements, quick construction; Cons--Corrosion reduces economic life, limited material availability leads to higher costs

High Moderate

Table APP - C.3 Spillway type decision table. Type Pros Cons Cost Drop Inlet Medium Easy to design and

construct Low capacity, requires additional auxiliary spillway

Conduit and el ontro

High High capacity, allows great Difficult to maintain Tunn deal of c l

Culvert Easy to desiconstruc

gnt

and Low capacity Low

Side-Chan y,r

construct High nel High capacitvariation ovecrest, easy to

small head weir, long maintain

Difficult to

Chute Easy to design and ct, ada

atteristics

Requires crest bridge Medium construmany foundcharacmaintain

ptable to ion , easy to

Baffled Ch ee s

in already

sign

High ute Eliminates nbasin, saves

d for stilling pace

Stilling basnecessary for outlet works,difficult to de

98

Table APP - C.4 Freeboard requirements by fetch.

ockfill zone properties. Z Permeabi

Table APP - C.5 Rone Gradation Size lity

Z meter = 3 Low one A Well Grated

Max: Diain

5% o. 100

sieve

5% to 1passing N

Zone B Well Grated

Max: 10 ft^3 High

Min: 0 ft^3 Zon

Grated Max: 27 e C Well Moderate

ft^3 Min: 1 ft^ 3

Table APP - C.6 Reservoir elevation-area and elevation-volume. (m ) Area (m^2) Volume Below (m^3) Elevation ) Area (km^2132 0 0 0 140 0.168068 67168068 2272 150 0.990397 990397 6464597 16 8 21560 2.02992 2029928 6222 170 3.225423 3225423 47842977 180 4.532232 4532232 86631252

190* 9.109798 154849109798 1402 191.5 9.986047 6329986047 1691 85.8

Total Reservoir Volume Below Spillway = 154841402

ay * Elevation of Spillw

99

Table APP - C.7 Outlet works calculation worksheet.

g 9.81 m/s^2Diameter of Tunnel 0.85 m 2.788 33.46Area of Tunnel 0.5671625 m^2Wetted Perimeter 2.669 mGate Cd 0.96

Manning's n = 0.013 Manning's n = 0.008

ElementLength of Friction (m)

Hydraulic Radius (m)

Area (m^2) (a1/ax)^2 Loss Type

Loss Coefficient

(a1/ax)^2 times Coefficient Loss Coefficient

(a1/ax)^2 times Coefficient

Trashrack Gross 4.0 0.04 Trashrack 0.550 0.020 0.000 0.000Net 3.0

Entrance 1.0 0.32 Entrance 0.200 0.064 0.200 0.0643.05 0.5 1.0 0.32 Friction 0.038 0.012 0.014 0.005

1.0 0.32 Contraction 0.100 0.032 0.100 0.032

Upstream Tunnel 0.6 1.00 Contraction 0.100 0.100 0.100 0.10058.65 0.2125 0.6 1.00 Friction 2.275 2.27

Table X.XComputation of Outlet Works Loss Coefficients and Flow Rates

500

0.861 0.8610.6 1.00 30 deg bend 0.070 0.07 0.070 0.0700.6 1.00 Expansion 0.200 0.20 0.200 0.200

Gates 2.0 0.08 Contraction 0.100 0.008 0.100 0.0089.3 9 0.044 0.004

7 0.085 0.0070 1.000 0.080

Downstream Tunnel .10 0.100 0.1005 25 0.6 27 2.275 0.861 0.861

0.6 .200 0.200 0.200 0.2005.452 1.431299263

efficient = 0.43 0.84

0.5 2.0 0.08 Friction 0.115 0.002.0 0.08 Gates 0.085 0.002.0 0.08 Exit 1.000 0.08

0.6 1.00 Contraction 01.00 Friction 2.1.00 Expansion 0

0 0.1008.65 0.21 5

Total =HEC orifice coAverage orifice coefficient 0.63

Number of Gates 1Width of Gates 1.00Height of GatesWater Depth just downstream Maximum Reservoir ElevationTunnel Invert at Gates

Max Flow Rate (max losses) 3/s Adju til this meets necessary flowsMax Flow Rate (min losses) 15.58 m^3/s Use t stilling basinAverage Flow Rate 11.78 m^3/sMaximum Velocity 27.48 m/s

Total Head needed to overcommax head loss to produce discharge

Max Losses Min Losses

=

21.92190133

of Gates

55.087.98 m^ st above worksheet un

his value to design

e

Table APP - C.8 Stilling basin w sheet. Pre-Stilling Basin

ork

Flow from OWorks 1 3/s

utlet 5.51 m

Flow from S 1 3/spillway 50.00 mTotal Flow 1 3/s65.51 mArea 3/s8.27 mVelocity /s 20.01 mStilling Bas in g 9.81 m/s2

Width 10.00 m D1 0.83 m V1 20.01 m/s D2 7.83 m Required Tailwater 139.33 m Froude No. 7.01 Length Factor (fig 9-42) 4.15 Length 32.48 m

100

Freeboard 2.78 m Tailwater Depth 2.00 m Chute Blocks TW Depth/d1 (fig 9-42) 10.00 d1 0.20 m # of blocks 25 Dentated Sill TW Depth/d2 1.05 d2 1.90 m s2 0.29 m w2 0.29 m h2 0.38 m # of sill blocks 18 L/d2 (fig 9-42) 4.35 length of jump itself 8.29 m

101

Table APP - C.9 Detailed cost b

reakdown of dam.

Item

Quan

tity

(SI)

Unit

(SI)

Conv

ersi

on

Fact

orQu

aniti

ty

(Eng

l)Un

it (E

ngl)

Tota

l Cos

t

Mat

eria

lLa

bor

Equi

pmen

tTo

tal

Tota

l inc

l. Ov

erhe

ad a

nd

Prof

itM

ater

ial

Labo

rEq

uipm

ent

Tota

lTo

tal i

ncl.

Over

head

an

d Pr

ofit

Dive

rsio

n1

EACH

1.00

01

EACH

1500

000.

0015

0000

0.00

1591

812.

0015

9181

2.00

1591

812

Emba

nkm

ent

Rock

Exc

avat

ion

2310

000

CM1.

308

3021

480

CY1.

805.

837.

6615

.28

19.3

81.

91Ha

ulin

g, 5

km

2310

000

CM1.

308

3021

480

CY1.

042.

613.

654.

45Co

mpa

ctio

n23

1000

0CM

1.30

830

2148

0CY

0.43

1.25

1.68

2.02

78Br

idge

35SM

10.7

6037

7SF

39.0

010

.05

7.70

56.7

569

.00

41.3

960

.22

Road

way

7791

SM1.

196

9318

SY7.

130.

690.

858.

679.

847.

579.

20

Out

let W

orks

.85

m D

iam

eter

Pip

e16

2LM

3.28

153

1LF

31.2

518

.00

9.15

58.4

072

.25

33.1

661

.97

67G

ates

1EA

CH1.

000

1EA

CH10

000.

0010

000.

0010

612.

0810

612.

08

Spillw

ay0

Oge

e W

eir

182

CM1.

308

238

82.5

048

.00

5.75

136.

2517

2.00

87.5

6.10

144.

5918

2.53

12Co

ncre

te S

lab

49CM

1.30

864

CY77

.00

12.4

55.

8095

.25

110.

0081

.71

13.2

16.

1610

1.08

116.

7374

36Co

ncre

te W

alls

368

CM1.

308

482

CY82

.50

48.0

05.

7513

6.25

172.

0087

.55

50.9

46.

1014

4.59

182.

5387

906

Stilli

ng B

asin

Conc

rete

Sla

b33

CM1.

308

43CY

77.0

012

.45

5.80

95.2

511

0.00

81.7

16.

111

6.73

5039

Conc

rete

Wal

ls67

CM1.

308

87CY

82.5

048

.00

5.75

136.

2517

2.00

87.5

51

1594

8

Rese

rvoi

r Pre

para

tion

1EA

CH1.

000

1EA

CH20

0000

.00

2000

00.0

00.

000.

000.

0021

2241

.60

2122

41.6

021

2242

Inst

rum

enta

tion

1EA

CH1.

000

1EA

CH15

0000

.00

1500

00.0

015

9181

.20

1591

81

Subt

otal

8516

9135

Cont

inge

ncy,

15%

1277

5370

Lice

nsin

g, 5

%42

5845

7En

viron

men

tal,

5%42

5845

7En

gine

erin

g, 1

0%85

1691

4To

tal

1149

7833

2

2002

Bar

e Co

sts

2005

Bar

e Co

sts

(ass

umin

g 2%

ann

ual i

nfla

tion

rate

)

6.18

1.10

0.46

10.6

70.

73

19.1

0

0.94

8.12

2.77

1.33

8.17

0.90

9.71

1 1.6.22

3.87

20 4. 2. 73 10 76..5

672 14 .2

2.4

4

6212

1426

6476

927 97

30

40 10

043

54363

8563 66

576 2

678

612

55 13

.21

50.9

46

101.

0814

4.59

6.10

82.5

3

1591

81.2

0

102

D. General

Figure APP - D.1 The temple of Angkor Wat, the primary tourist attraction in the area.

103

Figure APP - D.2 The Siem Reap Master Plan, courtesy of Professor Hackchul Kim.

104

Figure APP - D.3 Overhead view of (partially) scaled model of area.

105

Figure APP - D.4 Flow chart of proposed hydraulic system.

106

E. Schedule

Figure APP - E.1 Condensed fall schedule.

Figure APP - E.2 Condensed spring schedule.

107

F. Budget Table APP - F.1 Team budget.

108