case study2 - yuan-san-tsu flood division tunnel

土木工程概念設計

Conceptual Design Studio

│員山子分洪道│Yuan-Shan-TSU Flood Diversion Tunnel│ 1

Yuan-San-Tsu Flood Division Tunnel

ainstream Keelung River runs 84.6 kilometers, it originates

from Mount. Jintong of Pinxi District in New Taipei City, and

is one of the main branches of the Tamsui River. Keelung River

runs through Ruifang, Qidu, Nangang, Xizhi, into Taipei City and

finally merges with Tamsui River in Guandu. There are three

major branches to Tamsui River: Xindian River, Dahang River, and

Keelung River. When Keelung River enters into the Taipei basin,

the river way curves and winds causing inadequate discharges.

During the raining season when there is ample perspiration, cities

along the river banks such as Xizhi and Wudu suffer from severe

flooding problems and people complain about it. In the previous

years, we could still see on the TV news the flooding footage in

Xizhi and Wudu. Although the government adopted the cutting the

bends of the river to improve the Keelung river flooding problem,

the original natural river way is now occupied by houses. During

the high-water season, storm water and river were left with no path

to discharge. Water overflowed into the housing areas, leaving

people along the river banks again suffer from the flooding problem.

Typhoon Nari in 2001 turned northern Taiwan into water world,

and both banks of the Keelung River suffered heavy blow from the

flood. People voiced out to the government, demanding the

government to face the flooding problem along the Keelung River.

The lashing from the public stressed the urgency of the improvement

work of the Keelung River. The government also sensed people’s

demand to never suffer from the flood, and began proactively

M 1、 Introduction




promote the Keelung River Improvement Project. In 2002, Yuan

San Tzu Flood Division Tunnel was approved for construction.

The idea of Yuan San Tzu flood division tunnel was to diverse the

flood water using a tunnel to contour the over flowing water to the

East Sea outside of Ruifang. This measure would prevent the flood

water from overflowing into the residential area.

The concept of Yuan Shan Tzu flood division tunnel was

initiated in the 70s; however, the planned tunnel crossed three fault

zone and the geological criteria were inadequate for the construction.

In addition, there was also concern that the massive amount of fresh

water being poured into the sea would impact the coastal ecology.

The government thus was reluctant in approving the construction.

The ample perspiration brought by typhoons was the unceasing

nightmares to the people that lived along the Keelung River before

the improvement construction. After accessing the public need and

the maturity of the tunnel construction technology, the government




Photo 1. Keelung river field of recent years.

(Source : Water Resources Agency, Ministry of Economic Affairs.)

finally decided to begin with this improvement idea that existed for

over a decade. Yuan San Tzu flood division tunnel was finished in

2004 and it was a successful case of water treatment. With Yuan

Shan Tzu flood division tunnel, the people in Xizhi, Wudu ,and other

cities along the Keelung River were no longer the victims of flood.

The successful water treatment case brought fame to the Yuan

Shan Tzu flood division tunnel and made it the role model for the

future flood division constructions. However, there were great

many hardships and trouble solving wisdom behind this construction.

There are also issues raised by this construction that await better

methods in the future to solve and tackle.




The main intake construction site of the Yuan Shan Flood

Division Tunnel situated in the RuiGan New Village of RuiFang

Township in Keelung County. The key categories of the

construction included: flood division tunnel, flood division weir,

stilling basin, side weir, and barrage weir. Each structure has its

own purpose and function in design. In photo 2, you can see the

location of each structure. We will introduce the main design and

function of each structure in the following.

Typhoon

(year)

Lynn

(1987)

Reib

(1998)

Babs

(1998)

Xangsane

(2000)

Nari

(2001)

Flood Area

(hectare)

3,332 345 338 771 4,806

Flood Depth

(meter)

0.2 - 7.5 0.2 – 7.5 0.5 – 3.8 0.5 – 7.5 0.3 – 8.5

Death

(person)

32 0 0 59 104

Damage Before the treatment project, there were already 195

lives taken in the recent few years; the lost of property

reached over hundreds of billion dollars.

2、 Yuan Shan Flood Division Tunnel Structure Introduction

Chart 1. Statistics of Keelung River Typhoon Flood Water.




Photo 2. Intake of the Yuan Shan Flood Division Tunnel.

(Image taken from : Water Conservation Quarterly, volume 48)

2.1 Intake Structure Introduction

2.1.1 Barrage Weir

(1). Structure: concrete gravity wide weir, 8 meters high, 30 meters

long, top of the weir marked 68 meters high.

(2). Function: 3 comb type check dams built in the upstream to block

huge rocks and drift woods from floating to downstream.

2.1.2 Sediment Releasing Tunnel

(1). Structure: concrete gravity broad crested weir, 9 meter in height;

weir top length 20 meters and marked 69 meters high.




Photo 4. Elevation of the Barrage Weir, flood division tunnel is on the

left, and the sediment releasing tunnel is on the right.

(Source : Water Resources Agency, Ministry of Economic Affairs.)

(2). Function: releasing the stilling basin sediment to Keelung river

downstream, as well as ensuring the ecology of the downstream and

preventing the sediment from over depositing in the stilling pool.

Photo 3. Upper left and right: barrage weir; bottom left is a corner of

the downstream; bottom right is the sediment releasing tunnel.




2.1.3 Side Weir

(1). Structure: concrete gravity weir with flat crest, 2.5 meters in

height, 184meters in length, top of the weir marked 62.5

meters high, free overflow, connecting to the flood division

stilling pool.

(2). Function: separating Keelung River and the stilling basin.

When Keelung River waterline exceeds 62.5 meters, water

would flow over the side weir and enter the stilling pool.

2.1.4 Flood Division Stilling pool

(1). Structure: bottom of the pond marked 60 meters in depth.

Two sediment tunnel gates were set at the river way that led to

the downstream of Keelung River. Flood division weir was

built at the entrance that connected to the flood division tunnel

(2). Function: main function is for sediment deposit to prevent

sediment from being flushed into the tunnel and blocking the

tunnel. When the water level of the stilling pool exceeds 63

meters, the water will overflow the flood division weir and

enter the flood division tunnel.

(3). Maintenance: stilling pool deposit massive amount of

sediment, the sediment tunnel often opens for discharge.

There will also be one desilting on the stilling pool each year

in order for the stilling pool to function normally.




Photo 5. Upper left and right: side weir; bottom left and right,

stilling pool.

2.1.5 Flood Division Weir

(1). Structure: curved ogee weir, 3 meters in height, weir top

length is 80 meters with the height marked as 63 meters.

Middle section of the weir body on the upstream has a 7 meter

high division block, using free flowing method to connect to

the contraction section.

(2). Function: separating the contraction section between stilling

pool and intake, when the water line of the stilling pool

exceeds 63 meters, the flood water will overflow the flood

division weir and enter into the flood division tunnel naturally.




Photo 6. Left : flood division weir. Right : water level marking of

the stilling pool.

2.1.6 Contraction Section and Transition Section at the Entrance

(1). Structure: open channel, bottom elevation descents by a fixed

10% slope starting from 60 meters high, and connects to the

flood division tunnel entrance.

(2). Function: improve the tunnel entrance flow. The sophisticated

design allows the water to speed up and carries the sediment

away swiftly without blocking the tunnel.

Photo 7. Contraction and transition section at the entrance.




2.1.7 Flood Division Tunnel

(1). Structure: tunnel standard section is round hollow section,

internal diameter 12 meters, total length 2,484 meters, grade

1/100.

(2). Intake: RuiGan New Village of RuiFang Township in Keelung

County.

(3). Outtake: Provincial Highway 2 (Taiwan), coastal highway.

(4). Tunnel 1: 1,160 long, grade 1/100.

(5). Giufeng River Crossing Section: 33 meters long, grade 1/100.

(6). Tunnel 2: 1,290.5 meters long, grade 1/100.

(7). Function: automatically diverse the flood water that naturally

overflow the flood division weir into the sea outside of Ruifang

for discharge.

2.2 Outlet Structure Introduction

2.2.1 Outlet Transition Section and Chute

(1). Structure: dicth, transition section bottom elevation descends at

1% slope, chute bottom grade at 1:1, inner net width transits

from 12 meters to 35 meters.

(2). Function: improve water flow at the tunnel exit.

Photo 8. Left : tunnel intake; right : tunnel intake model.




Photo 9. Left : tunnel outlet transition section model; right : tunnel

outlet stilling basin.

Photo 10. Construction process of the Yuan Shan Tzu Flood Division

Tunnel Outlet

2.2.2 Outlet Stilling Basin

(1). Structure: close conduit and open channel, inner net width 35

meters, net height 20.8 meters; elevation of the bottom marks

-6 meters, end sill elevation 4 meters, normally maintains 10

meters pool for energy dissipation.

(2). Function: stilling basin dissipates massive flood energy before

flood water is discharged into the East Sea, preventing coastal

erosion that might damage the ecology and the view.




Photo 11. Yuan Shan Tzu Flood Division Tunnel Outlet, at the

Provincial Highway 2 (Taiwan), the coastal highway.

(Source : Water Resources Agency of the Ministry of Economic

Affairs.)

2.3 Sediment Tunnel Gate Regulations

2.3.1 Regular Operation: when the water level at the upstream

of the barrage weir is below 63 meters, the gate will remain

opened at all times.

2.3.2 Flood Division Operation: when the water level at the

barrage weir rises over 63 meters, the sediment tunnel gate

will be closed until the flood water subsided and the water

level is blow 62.5 meters. The sediment releasing gate will

be opened again, resuming regular operation status, of

which the gate will remain opened at all times.




2.4 Alert Policy

According to the operation regulation of the Keelung River Yuan

Shan Tzu Flood Tunnel Division, currently there are three types of

alerts :

2.4.1 Pre Flood Division Alert: when the barrage weir upstream

water level reaches 62.5 meters, alert the Tamsui River Flood

Prevention Command Center, and the Command Center will

post the warning along with the Tamsui River flood alert.

Control Center uses intake and outlet broadcasting stations to

distribute the flood division alert, and notifies the New Taipei

City Emergency Management Center at the same time.

2.4.2 Flood Division Alert: when the barrage weir upstream water

level reaches 63 meters, the flood division is commenced.

The Control Center notifies the Tamsui River Flood

Prevention Command Center, and the Command Center will

issue the warning together with the Tamsui River flood alert.

Control Center uses intake and outlet broadcasting stations to

distribute the flood division alert, and notifies the New Taipei

City Emergency Management Center at the same time.

2.4.3 Emergency Alert: when the barrage weir upstream water

level exceeds 67.2 meters and the tunnel is filled, the Control

Center notifies the Tamsui River Flood Prevention Command

Center and the Command Center posts the alert with Tamsui

River flood alert. Control Center uses intake and outlet

broadcasting stations to sound the emergency alert, and

notifies the Emergency Management Center of Taipei City,

New Taipei City Keelung City, and town office, police

departments and fire departments of Ruifang district

simultaneously.




2.5 Flood Discharge Design

When Keelung River water level is below 62.5 meters, it is in

the safe range. However, when the water exceeds 62.5 meters, the

flood water will overflow into the side weir and enter in the stilling

pool for sediment deposit. At this time, the sediment releasing

tunnel is closed. After the sediment deposits for a period of time,

the flood water will be cleaner. When the water level of the stilling

pool exceeds 63 meters, the flood water will naturally overflow into

the flood division weir and enter into the division tunnel. The

contraction design before the flood division tunnel will speed up the

flood water and swiftly carry away the sediment particles in the

flood water. This will prevent the sediment clotting the walls of the

tunnel to shorten the tunnel life span.

The sediment deposit in the stilling pool will be over

accumulated after operating for a period of time. When the water

level is yet reaching the alert line, the sediment releasing tunnel will

be opened to flush the sediment in the stilling pool to the

downstream. This is because after being scrubbed by the river

water for a while, the downstream will suffer from the riverbed

erosion problem, and supplementing the sediment is very crucial to

the eco maintenance. The design of the sediment releasing tunnel

flushes sediment downstream so that the sediment volume would not

be insufficient, which in turn stabilizes the downstream eco function.

However, the problem of sediment over deposit results from the

sediment in the stilling basin being not flushing downstream

through sediment releasing tunnel. Government will perform

annual desilting to ensure the normal function of the stilling pool.




Once the flood water enters the flood division tunnel, it

discharges into the sea at the Provincial Highway 2 (Taiwan), the

coastal highway. The flood water carries massive amount of energy

from the long flowing, if it discharges directly into the sea, the

energy will cause erosion and damage the north east coast.

Therefore there is an stilling basin at the outlet, allowing the flood

water to dissipate the accumulated energy before entering the sea.

Once the flood water sits in the stilling basin for a while and the

energy is dissipated, the water then is discharged into the sea. This

shall reduce the erosion of the northern east coastal area.

The flood discharge principle of the Yuan Shan Flood Division

Tunnel is by discharging the excessive flood water into the sea

through the division tunnel. This is like setting up a large manual

draining pipe, and drains away the excessive water. The choice of

the construction site, the detail design of each structure are carefully

connected and associated. The design is so ingenious that if we

closely study the function of each structure, we will know how much

work was dedicated to the detail design of this construction.




Photo 12. Automatic flood division process

Upper left: flood water overflowing the flood division weir; upper right:

flood water discharging into the tunnel.

Bottom left: Intake of the flood division tunnel; bottom right: open sea

near Ruifang, the East Sea.

(Source: Water Resources Agency of the Ministry of Economic

Affairs.)

2.6 Hydraulic Modeling Verification

According to the related reports on the Public Construction

E-paper, in order to verify whether the detail design of the Yuan Shan

Tzu Flood Division Tunnel matched the design requirement which

specified that when Keelung river discharge was at Q200=1,620cms,




the tunnel division flood discharge was at Q200=1,310cms; a

hydraulic model was utilized for testing. The key objective was to

test on a hydraulic model at the ratio of 1/100 to closely examine the

design details of the intake structure, inside of the flood division

tunnel, the outlet structure physics and the flood routing capacity.

The research result of the testing was provided to the design unit as

the reference for detail design modification and environment

evaluation.

The focus points of the hydraulic model testing research were on:

1) flood division structures function and hydraulic physics under peak

discharge in different recurrent duration; 2) sediment distribution of

the river way and the stilling pool at the downstream of the side weir;

3). sediment density distribution at the river downstream, tunnel

entrance and exit.

Photo 13

Hydraulic Model

(Source : Water Resources Agency of the Ministry of Economic Affairs.)




3. Yuan Shan Tzu Flood Division Tunnel Construction Plan

Using a flood division tunnel to discharge the flood water was

an idea that started during the Japanese occupation era; however the

typhoon damage statistic at the time did not show any imminent

need for the Yuan Shan Tzu flood division tunnel. At the time, the

professional technology was not yet developed to overcome the

geological criteria such as fault zones and deserted mine pits;

therefore the construction was put on hold. In year 2000, flood

from Typhoon Xangsane took 59 lives of the coastal residents,

making the government aware of the inevitable action in improving

the Keelung River. By year 2001, Typhoon Nari claimed 104 lives

and uncountable property lost, the improvement project became of

great urgency. In addition to the imminent need of the people, the

government also wanted to demonstrate its determination to improve

the Keelung river. Yuan Shan Tzu Flood Division Tunnel project

thus was approved for construction immediately.

Yuan Shan Tzu Flood Division Tunnel construction was one

of the construction categories of Keelung River Yuan Shan Tzu

Flood Division Tunnel Construction Project. There were other

construction projects that aimed at the improvement of Keelung

River; however, Yuan Shan Tzu Flood Division Tunnel was the

most effective one. It is now the role model of many other flood

division construction projects. The main construction of Yuan

Shan Tzu Flood Division Tunnel cost approximately NT$3.994

billion. The construction began on June 5th 2002 and was

originally scheduled to finish on October 4th, 2004, giving the total

construction duration a little over 2 years to finish. The timing

was very tight, and many works were needed to be done within

such a short time: intake, tunnel, outlet, check dam, and the

clearing of the residual soil and rocks. At that time, government




adopted the most advantaged turn-key method, having the turn-key

contractor responsible for both construction detail design and the

actual construction work. The detail design also required using

hydraulic modeling to verify the flood division function, ensuring

the flood discharge would reach the expected goal.

Before the construction was completed, typhoons with ample

perspiration struck Taiwan and resulted flood water overflow.

Government must make a decision immediately to execute

emergency flood division in order to discharge excessive flood

water. Three emergency flood divisions were executed before the

completion of the Yuan Shan Tzu flood division tunnel. These

three flood divisions successfully protected people’s lives and

properties and the emergency measure was validated. However, it

was also because the divisions that the completion of the

construction was postponed to October 28th, 2005. In just a short

3-year for Yuan Shan Tzu Flood Division Tunnel to be finished for

operation, naturally there existed many obstacles to be overcome

one by one. This construction also caused a few ecological issues

that brought the attention of the ecological protectionists. There

are many things that we have not done and things we could do

better for Yuan Shan Tzu flood division tunnel construction, or in

the design of flood division constructions in other regions in the

future. In chart 2 we will have detailed description on the

construction plan.




4. Construction Obstacles

4.1 Timing: Short Construction Time

From the design and the structure we can see the enormous scale

of the Yuan Shan Tzu flood division tunnel construction. There are

several detail constructions for different functions, such as the intake,

tunnel, outlet construction, et al. If government adopted the usual one

step at a time construction progress - waiting for one construction stage

completed to begin the next stage - then how long will it take for Yuan

Shan Tzu flood division tunnel to complete? From the need of people

at the time, we could understand that, if such a construction indeed was

capable of relieving people from the flood problem, people would

naturally want the construction to finish as soon as possible. The

government also expected this construction to effectively discharge the

flood water and reduce the harm of flood. Taiwan goes through

several strikes from typhoons every year, and typhoon normally carries

heavy perspiration. With the early completion, we could prevent the

recurrence of the catastrophic tragedy of casualties and property lost.

Government ruled on the commence of the construction on June 5th,

2002 with completion date set on October 4th, 2004, giving only a little

over 2 years for the construction to complete. Such a large-scale

construction would take a fairly long time if were to finish gradually;

however, the purpose of this construction was to prevent disaster, it was

a disaster prevention construction urgently needed by people; the

government thus must adopt an effective and shorter duration

construction procedure to deal with the compressed timing.

To ensure the flood division function and the early

completion, Water Resources Agency of the Ministry of

the Economic Affairs adopted the most advantaged

turn-key method to execute the main construction.




Under the basic design framework, the turn-key

contractor shall be responsible for the detail design and

construction. The detail design of the flood division

structure shall require hydraulic modeling to verify the

flood division function. United Geotech Inc. is entrusted

with the construction supervision, and the CTCI

Corporation will be in charge of environmental

monitoring and evaluation during construction and

operation.

--Water Conservation Quarterly, Vol.48

Turn-key method can reduce the waste of time as the turn-key

contractor is responsible for detail design and construction, which

reduces the communication problems between design and construction

detail. This will decrease the obstacles in design and construction to

the minimum and move forward the completion date. In order to

bore through the tunnel expeditiously, multiple adits were set up inside

the tunnel. This would increase the cross sections during the tunnel

construction and helped to shorten the work schedule. The measure

made it possible for the tunnel to bore through within one year.

What the government did was to simultaneously undergo several

detail constructions to reduce the waste of time. Finally the

construction was able to finish within the shortest possible time,

providing one more protection to the lives and property of the people

at the middle and downstream of Keelung River.

4.2 Geological Obstacles: Faults and Deserted Mine Pits

When the concept of Yuan Shan Tzu flood division tunnel was

generated in the 70s, the first and foremost obstacle was the geological

instability. The planned route of the tunnel crossed several faults

including Ruifang fault, Yuken fault and Fantzeou fault. The geo




rock formation of the planned route was mainly composed by

sandstone, shale and sandstone/shale interlayer, in which the rocky

stratum was coal-bearing seams. The stratigraphic faces were

complicated, there lacking complete geographical data base to

encounter different geological conditions, and the estuary of the

division tunnel was a slope formed by the wasted coal cinder; these

made the stability questionable and require further investigation. In

addition, there were many deserted coal mine pits within the tunnel

excavation route, there most certainly deposited some flammable gas

such as fuel gas and methane gas. Inappropriate construction would

cause disastrous consequences or collapsing due to the mine pits.

Also there could be massive inflow of water during construction as the

stratum was saturated with ample underground water. All these

elements added uncertainty to the excavation process.

The technology inherited from Japanese occupation era was

insufficient to overcome all these problems. As the technology

matured through time, the geological database was established and

geological exploration equipments were developed. Yuan Shan Tzu

flood division tunnel construction finally was able to cope with these

complicated and uncertain issues and tunnel 1 and 2 were bored

though within one year. Overall speaking, the tunnels were able to

bore through so smoothly was a reflection of people’s urgent need, the

government’s respond with policies, and the maturity of the

construction technology. In short, this is a successful case of all

elements come together. When all elements came together, Yuan

Shan Tzu flood division tunnel was made possible. Naturally there

were many problems to be solved to help the smooth progress of the

construction.




Photo 14. Location of the adits

Photo 15. Problems encountered during tunnel

construction.

Fault

Deserted Mine Pits

Massive

Inflow of

Water

Flammable

Gas

Tunnel Construction




4.3 Public Resistance: NIMBY Effect

NIMBY effect actually is a grass rooted and advanced

movement; it is even a chance to promote social

collective review. Because NIMBY (Not In My Back

Yard), hence NIABY (Not In Anybody’s Back Yard),

thus NOPE (Not On the Plant of Earth), and further

pondering the review of the over all structural question,

making it the power to push the society to grow.

--Wei-Chieh Lai, Secretary-General, Green Citizens’

Action Alliance

NIMBY truly reflects the tug of war between the need of a

partial of people and the large group. How to reach a balance

where both side wins is a challenge to the wisdom of the decision

making organization. All construction come from the need of

people; any construction that does not originate from people’s need

is unwanted and is not possible to exist. However, a question is

pulled from this that is “the construction itself satisfies whose need?”

Some constructions may protect the lives of some people, and thus

has its reason to exist; however at the same time when some people’s

need are satisfied, would some others’ interests/benefits be deprived

or damaged? This is like the two ends of a seesaw: when someone

wins, someone else looses.

The construction itself not always has a positive impression on

people. If a construction is in the neighborhood and it results in the

rising of the estate value, people of the neighborhood naturally have

a higher acceptance to the construction. However, if the

construction brings negative impression, people of the neighborhood

for sure would receive it differently. Construction as such that

brings negative impressions tend to bring in problems that would




induce people’s resistance. For example, air pollution, decrease of

the estate value, damaging of the nearby environment, etc.

However, if the construction is associated with the daily lives then

this construction must find a place to work on. If everybody is in

the “NIMBY” state of mind, then the actual collective meaning

would be “NIABY” which in further concludes as “NOPE”. This is

a very realistic public phenomenon that is very difficult to overcome.

Everybody needs to get rid of garbage, but no one

wants the garbage yard to be right next to my house,

this is NIMBY effect. We have to solve this NIMBY

effect. It does not matter if Ruifang suffers from

flood, when the flood division tunnel is finished, Xizhi

is the area that will be benefited from it. This

involves the social welfare. Namely the

government allows houses to be built in Xizhi, forcing

the government to spend top dollars in building flood

division tunnel in the upstream, does this make

sense at all? Or is it to say that since we have flood

division tunnel at the upstream to relieve

downstream from flood problems, the area in the

downstream thus can be developed without any

limitation or restriction? This is a question of

chicken and egg.

-- April 12th, 2010, Zhen-Yu Du, Chief, Yuan Shan

Tzu Flood Division Tunnel Management Center

At the planning stage, government heard the opposing voices

from the local residents that were against the construction of Yuan

Shan Tzu flood division tunnel. This was because that the outlet of

the division tunnel located in Ruifang, but the beneficiary of this




construction would be the people in Xizhi district. Construction

proposals such as these where the construction site ‘would be in my

neighborhood but I would not be benefitted from it’ normally could

not receive full support of the local residents. NIMBY effect can

be found in many construction cases, especially the ones that

associated to the negative perspective of the public; for example,

garbage incinerator, landfill etc. How to smooth away public’s

rejection to the construction was a big challenge the government

faced at the time. To change the public’s perspective towards a

construction and further to make people accept the fact that they

would not be the direct beneficiary of this construction was a test to

government’s wisdom.

Zhen-Yu Du, the chief of Yuan Shan Tzu Flood Division Tunnel

Management Center pointed out that, due to the uncontrollable

development in the Xizhi district, the flood discharge became a

problem which contributed greatly to the Keelung River flood

problems. In order to improve the flood problem in Xizhi district,

was it really reasonable to install a flood division tunnel at the

upstream in Ruifang district? With such a solution in operation,

could Xizhi district keep on developing for commercial reasons?

This indeed worth careful considerations.

According to the 10th River Management Office of the

Hydraulic Engineering Office, Yuan Shan Tzu Flood

Division Tunnel Improvement Project that scheduled to

complete in 2004 was scheduled to contract out for

construction in the middle of May. However, there was

resistance in the land acquisition, and conflict of mining

and fishery rights that waited communication. If these

problems could not be resolved, the construction

progress was likely to be stalled. Yuan Shan Tzu Flood




Division Tunnel construction mattered greatly with the

Keelung River Improvement Project. Executive Yuan

ordered the construction to be completed before end of

2004; Hydraulic Engineering Office hoped to finish as

early as possible. However, resistance lied in the

execution process. On the land acquisition, the basic

principle was that any land with the overburden depth

below 40 meters, the 10th River Management Office shall

levy the land use; when the overburden depth exceeded

40 meters, the office shall register the user right and

render reasonable compensation. However, no

measure was able to satisfy all parties. Despite the

estimated land acquisition being not much, the attempt to

resolve it in a short time may not be as easy.

--- February 28th 2005, China Times.

In order to begin the construction of the flood division tunnel

smoothly, the government adopted forceful land acquisition and

provide reasonable compensation to solve the public resistance issue.

Though government listed compensation standard, there still lacking

recognition from the upstream residents whose land were forcefully

acquired. Acquiring land for flood discharge policy is bond to

encounter public resistance and opposition. Government

summoned several coordination councils and continued to

communicate and explain to the public, hoping that the public would

understand the effect behind the policy and turn to support and

recognize the policy. This process was rather painstaking and

difficult.




Dr. Jihn-Sung. Lai of the Hydrotech Research Institute at the

National Taiwan University pointed out that people at the time was

in great concern over the safety of Yuan Shan Tzu flood division

tunnel construction. It would be very difficult for the government

to convince people by answering all their questions. Dr. Lai’s team

used virtual animation so people could understand immediately the

influence of the flood division tunnel construction have on their

future. After the video presentation, people learned that the

construction imposed no threat to their safety and that there would

be better environment for their leisure use. The construction would

help solve the flood problem for the people at the downstream and

create better and safer lives in the future. After people understood

the Yuan Shan Tzu Flood Division Tunnel better, the acceptance

level was greatly increased. However, after people accepted the

project, there came issues of profit groups and local residents

demanding compensation. How to receive reasonable

compensation has always been the primary concern the people have

after accepting the construction projects. Government at the time

issued a set of compensation standard. Despite adopting forceful

acquisition and reasonable compensation to settle the public

resistance issue, the government still could not make all the involved

parties satisfied with the compensation. One comforting note was

that during the coordination process, there was no large scale public

resistance in stopping the operation of the construction. When

Yuan Shan Tzu Flood Division Tunnel was finished, the effect was

recognized by the local residents, and it indeed relieved people in

Xizhi of the flood problems, shaking off the nightmares that had

been haunting the residents in the middle to downstream of Keelung

River.




Photo 16. Computer simulated flood division tunnel operation

status during flood.

4.4 Flood Before Completion: Emergency Flood Discharge

Before Yuan Shan Tzu flood division tunnel was completed,

there were three occasions that required flood discharge, we called

them the “emergency flood discharge”. In 2004, Yuan Shan Tzu

flood division tunnel went through 0911 extremely heavy rain,

typhoon Nock-Ten and Nanmadol total 3 emergency flood

discharges, the combined flow was approximately 1.278 million

square meters, effectively reduced the flood water level at the middle

and downstream and prevented flood damage at the downstream.

The government then faced a decision making issue. Before

they issued the emergency executive order for the emergency flood

discharge, they must evaluate how much damage would the

emergency flood discharge do to the tunnel, and the positive

economic effect on the society after the flood damage on the middle




to downstream was relieved. The government thus must draft a

plan in advance for emergency flood division, evacuation and

control operation. These three emergency flood divisions displayed

the positive effect on protecting the lives and properties of the

residents. According to the Water Resource Agency’s report, the

appearance of the concrete lining inside the tunnel remained intact

from the three divisions, the damage was mainly on the lining steel

mold and the heavy machineries inside the tunnel. After re-order

the steel mold, the tunnel concrete lining was fully completed in

March 2005. The decision of emergency flood discharge was

approved and recognized by the residents; it was also a direct proof

to the flood division effect of the Yuan Shan Tzu flood division

tunnel. The opposition voice was finally diminished.




Photo 17. Emergency flood division damage to the tunnel portal.

Before the flood division tunnel was finished, in order to protect the lives

and properties of people, the government ordered emergency flood

discharge after overall evaluation. The heavy flow of the flood from

typhoons severely damaged the heavy machineries and steel mold of

the concrete lining. However, the emergency flood discharge also

protected the lives and properties of the downstream residents. This

decision won the unified recognition.

(Source : Water Resource Agency, Ministry of Economic Affairs)




Chart 3 Statistics of Historical Flood Discharge of Yuan Shan Tzu

Flood Division Tunnel

Year Name of

Typhoon

Maximum Flood

Discharge

(CMS)

Total

Flood Discharge

(M3)

(per million)

Emergency

Flood

Discharge

2004 9/11/2004 0911 Extremely

Heavy Rain

200

10/25/2004 Nock-Ten 600

12/03/2004 Nanmadol 450

Regular

Flood

Discharge

2005 7/18/2005 Haitang 211

8/04/2005 Matsa 78

8/31/2005 Talim 382

10/02/2005 Longwang 115

2006 9/10/2006 Extremely Heavy

Rain

140


Rain

35

9/18/2007 Wipha 76

10/06/2007 Krosa 636

11/26/2007 Mitag 91

2008 7/28/2008 Fung-Wong 75

9/12/2009 Sinlaku 247

9/27/2009 Jangme 351


Rain

296

10/05/2009 Extremely Heavy

Rain

94

10/23/2009 Extremely Heavy

Rain

168

Total 18 flood divisions 79.94




4.5 Ecological Issue : North East Costal Ecosystem

Yuan Shan Tzu flood division tunnel solved the flood problems

that troubled Xizhi and Keelung River downstream for years. The

effect and achievement won praises and affirmation; however, such

construction arose issues that require our further thinking in how to

improve it in the future.

Although each flood discharge was merely 2 to 3 hundred

CMS, the worst scenario did happen. Flood water carried large

amount of sediment, garbage, fresh water life forms out of the tunnel

and entered the sea directly. The sea at the flood division tunnel

exit became the new Yin-yang sea.

Typhoon initiates the Yuan Shan Tzu flood division, and

the flood discharge flushes sediment, plankton, aquatic

lives to the sea. Ming-Xiu Zhen explained the formation

of the yin-yang sea, one is because the sediment flushing

into the sea, suspends, floats and results in shading; the

other one is because fresh water is lighter than the sea

water and would retain on the upper layer of the sea,

making the fresh water layer that carries sediment even

more obvious.

In addition to the visual impact of the fresh water, with large

amount of aquatic lives flush into the sea unexpectedly,

those that suffer the most would be the innocent fresh

water life forms that are forced out of their homes. Taiwan

Coral Reef Society receive many reports from their

members reporting that many mouthbreeders are found

lost in the sea area at the outlet of the flood division tunnel.

These mouthbreeders swim blindly, unable to find familiar

shelters and food to feed.




Flood water with high slit content causing the sea area to

be covered by debris, and this is a fetal blow to the life

forms in the sea area. As pointed out by Zhen, if the

sediment volume in the flood water is not too much, coral,

sea urchins would still be able to blow out the sediment

that covers their breathing mouths. However, if the

sediment amount is high and covers the mouth and

choking the anthozoa, it would for sure kill the anthozoa.

As for algae, since it is co-dependent to the coral and is

unable to move, when the flood sediment keeps covering,

death is inevitable.

--October 2nd 2005, United Daily

Flood water normally carries massive amount of sediment, so

we have stilling pool design at the intake entrance to deposit

sediment and allows it to discharged into the sea by way of the

flood division tunnel. Even so, the amount of the sediment

carries by the flood water is still in a big volume and causes

problems to the north east sea eco system when the flood is

discharged to the sea from the outlet exit. These issues have been

the concern of ecological protectionists. When the government

planned the Yuan Shan Tzu flood division tunnel, the main concern

was human lives and property safety. Here we find that the

ecological system of the nature should be included in the

consideration, because we are closely associated to the nature. It

is not what we would like to see if the survival of other species are

deprived for the need of human being, or that their ecological

habits are forced to change.

We can see from the ecological protection reports that, over

discharge sediment would choke the mouth and pharynx of coral

and prevent it from getting rid of the excessive debris. In the long




run, this would cause the death of the coral. There are even

disoriented fresh water lives that find it difficult to find shelters or

food. When our government was building the Yuan Shan Tzu

Flood Division Tunnel, did they realize such flood discharging

method would affect the ecosystem?

Honestly speaking, people in the past did not think much

about the ecology. Making money was all that mattered.

However, it works the other way around now. Ecology is

important because NGO groups are deeply involved and

they are eager to contribute to the issue. What the

result of the flood division would be, no one dares to

guarantee.

Flood water is generally yellow and dirty. The most

serious influence on the sea area is that “the sediment is

the number one killer to coral”. Once the sediment

deposit on the coral, especially the fine sand, coral would

not be able to grow. For this, when we made the design,

we tried to use the current at the exit to carry the find

sand away and disperse the find sand. Because the

current at the north east coast is stronger. So far

everything is fine, though there is most certainly influence

on the ecology. No one is to say there is none. Any

construction has its impact on ecology. Right now the

condition does not get any worse. We hope that when

the catchment basin at the upstream is better improved,

the sediment in the river would decrease in the future.

The influence of the flood water discharge to the coast

would be less and less.

-- April 12th, 2010, Zhen-Yu Du, Chief, Yuan Shan Tzu Flood Division Tunnel Management Center




In the interview of Mr. Du, we understood that government put

the outlet exit of the Yuan Shan Tzu flood division tunnel on the

north east sea coast where the current was stronger, hoping that the

current could swiftly and naturally carry the sediment away without

depositing on the coral and affect the natural ecology of the area.

From the stilling pool at the upstream to the location of the estuary,

we saw that the government had already putting the ecology issue

into concern when designing the Yuan Shan Tzu flood division

tunnel. The actual effect on the ecology surfaced when Yuan Shan

Tzu flood division tunnel was finished and the flood division was in

operation. Indeed, the sediment deposit problems still exist.

From the ecological protection point of view, the ecological

protection measure of the Yuan Shan Tzu flood division tunnel is not

good enough. Right now what we can do is to make sure the

situation not to get worse. Mr. Du thinks that the current situation

is well under control. If in the future we can do better in sediment

process at the upstream catchment basin, prevent large quantity of

the sediment from being flushed down to the outlet, then perhaps we

could actually improve the damage to the north east sea ecology.

Whether the current condition is truly improved, this

construction case inspires us in many ways. There are many factors

for a construction to consider. It is more than just construction

itself but also human needs, ecological needs, environmental needs,

etc. How to find the balance in so many different needs does worth

our time and effort to study and review. We expect to find better

designs to solve these problems that are not yet processed adequately;

or to design better construction role models to put an end to the

negative effects.




5 General Discussion – Successful Water Improvement Model

Taiwan is an island with many rivers and encounters high

frequency of typhoons. Many rivers in Taiwan have flood

problems, and a successful water improvement case could be the role

model for other disaster prevention constructions. Yuan Shan Tzu

flood division tunnel is the most recent construction case with the

best flood division effect. It successfully improves the long term

flood problem at the Keelung River downstream, and brings a safety

living for the residents in Xizhi District.

Government had the idea to have a flood division tunnel in

Ruifang District since the 70’s, but the geological uncertainty and

that the flood problems from typhoon were not very serious made

the construction remain an idea. In recent years, high rise buildings

were built in Xizhi District, many commercial buildings resulted in

the over development of the area. Typhoon Xangsane in 2000 and

Typhoon Nari in 2001 altogether took away over one hundred lives

and countless property damage. Government then realized the

situation and approved the construction of Yuan Shan Tzu flood

division tunnel.

The construction of Yuan Shan Tzu flood division tunnel includes

1) intake, 2) outlet, 3) tunnel, 4) check dam, 5) residual soil and rocks

clearing process, etc. As the construction time span was only three

years, the government adopted turn-key contract, having one turn-key

contractor in responsible for all the detail design and construction

works to reduce the construction time. Tunnel construction used

multiple adits to perform multiple cross sectional construction, using

the fastest speed to bore through the tunnel within one year. The

excavated soil and rocks from the tunnel construction were collected




in the residual soil treatment plant first then processed according to

the remaining soil process policy. The challenges faced by the tunnel

construction at that time were 1) geological uncertainty, 2) crossing

multiple fault zones, 3) water inflow, and 4) hidden crisis of

flammable gas.

On the construction of outlet and intake, in order for the flood

discharge to operate smoothly when completed, the detail design

utilized “hydraulic modeling” to test and verify the flow speed

analysis or sediment deposit. A stilling pool was designed at the

intake and the main function of this stilling pool was for desilting,

preventing excessive sediment being flushed into the tunnel. An

stilling basin was set at the outlet with design to dissipate the energy

carried by the flood water, before discharging into the sea and

resulting erosion at the coastal area. Despite that, the flood

discharge still carried massive amount of sediment and inflicted the

north east coastal ecology. Coral in that sea area suffered from

breathing problems from the excessive sediment in the sea. When

designing the Yuan Shan Tzu flood division tunnel, north east sea

area was chosen as the estuary of the tunnel for its strong current.

The idea was for the natural current to carry the sediment away

swiftly. There is still room for the improvement on the issue

involving ecology. If the sediment releasing job at the catchment

basin on the upstream can be better improved in the future, the

influence on the outlet ecology naturally would be decreased.

In addition to the above challenges, Yuan Shan Tzu flood

division tunnel also faced public resistance issue since was approved

for construction. There were also three emergency flood discharges

before the construction was completed to encounter the flood from

the typhoon perspiration. The government must assess between the




construction lost and the lost of lives and property on both sides of

the river to make the best decision. Building the Yuan Shan Tzu

flood division tunnel helped the middle to downstream residents

shake off the flood problem. The contribution is so great that it

becomes the role model for the future flood prevention

constructions.

From concept to birth, a construction overcomes many

obstacles along the way. Each process challenges the wisdom of

the construction team. However, use better, faster and more

diversified measures to achieve the final goal is the skill that

everyone in the construction field must learn. Through the

introduction to the Yuan Shan Tzu flood division tunnel, we hope

people in the future would come up with better solutions for flood

prevention; we also hope for more of the fine constructions in the

future to improve the lives of the future human being.




Practice Part I : Use your brain

1. Find a construction case in life, try to analyze its initial planning,

construction process and operation after completion, what are the

problems that this construction might encounter?




2. Find a river in Taiwan that requires flood discharge design and

explain why.

3. If you are the person in charge of the Yuan Shan Tzu Flood

Division Tunnel construction, since government only grants 3

years for the construction to finish, what measures would you

adopt to meet the short construction span?




4. If you are a member that participates the tunnel construction, and a

large inflow of water (underground water) happens half way

through the excavation, how will you discharge/drain the water?

5. Suppose you are a government official who is in charge of an

important construction decision making, and you are answering to

people’s demand to build a garbage landfill yard somewhere.

The nearby residents of the site raise strong opposition, how will

you solve the NIMBY effect issue?




6. Think of the soil and rocks from the tunnel construction

excavation, how to utilize them for further use?

(Please ignore the fact that government will solve this problem

based on policy, and come up with your own re-use method.)

7. Think of the positive effects of the flood water that normally

brings disaster, how can we use it to help and help with what?

Try to come up with the positive functions that can be created out

of the negative natural catastrophes.




8. Suppose your are a government official who is in charge of an

important construction decision making. If one day the rain is

highly acid or carries poisonous materials, and it would seriously

imperils the ecological safety of the sea area if the water is

discharged into the sea, i.e., causing the massive death of the

marine lives in the sea; when the flood strikes, would you choose

to discharge the flood or not? Why? Or, if you can come up

with a measure to protect human lives and property and the

ecology at the same time?




1. At the estuary of the Yuan Shan Tzu flood division tunnel there is

an “stilling basin” designed to prevent flood water overly eroding

the estuary. Now try and design another protective installation at

the estuary to prevent fresh water life forms to be flushed into the

sea during flood.

Part II : Use your hands

case study2 - yuan-san-tsu flood division tunnel

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