Date of interview: Wednesday, February 18, 2015
On this day, we were all invited to see the Shin Naruha River Dam, and we stopped at the Senya Dam on the way there. It looks like a directly operated dam because of its gorgeous equipment, but it is a Okayama Prefecture-owned dam. The time was around 7:40 in the morning. We visited the dam in the sleet.
From the left bank
The most luxurious equipment is this. In addition to the 11 free overflow emergency flood discharges, there are also 11 free overflow flood discharges,crest gate(The station is fully equipped with four roller gates, two orifice gates, and two conduit gates for permanent flood discharge. In addition, there is one five-stage linear multistage selective intake system and one water discharge pipe.
The specifications of the flood control discharge system are as follows
discharge pipe
form (something takes) | Circular buried steel pipe with square hood |
Dimensions | Drinking mouth W3.200mxH4.400m Middle section Φ2.400mx Φ2.000m |
number of articles | two articles |
flow rate (esp. water or electricity) | 100m3/sec |
Completion date | March 1997 |
production | Mitsui Engineering & Shipbuilding Co. |
main gate
form (something takes) | Jet Flow Gate |
caliber | Φ2000mm |
number of gates | two gates |
Opening and closing speed | 0.1m/min |
open/close system | Hydraulic cylinder system |
Completion date | March 1997 |
production | Mitsui Engineering & Shipbuilding Co. |
secondary gate
form (something takes) | ring holowagate |
caliber | Φ2000mm |
number of gates | two gates |
Opening and closing speed | 0.3m/min |
open/close system | Hydraulic cylinder system |
Completion date | March 1997 |
production | Mitsui Engineering & Shipbuilding Co. |
This is the construction monument of the Senya Dam. It shows that the main body of the dam was constructed from March 1989 to June 1997, a period of eight years. The word "Heisei" sounds like a recent development, but it was a long time ago.
On the upstream side of the left bank, there is a magnificent building, which is a boatyard and a warehouse for storing patrol boats for the reservoir. An incline is also attached on the other side (reservoir side).
The top edge is open to automobile traffic.
The reservoir of the Senya Dam is named "Sensuiko (Thousand Water Lake).
There is another stone monument on the left bank with the river name "Takahashi River" engraved on it.
Looking at the upstream face, the facilities are so well equipped that it is hard to believe that it is a very prefectural dam.
There is a management office on the left bank. It also has an exhibition room, but it is too early in the morning and not open yet. I hear that the models and other exhibits are amazing, so I would like to visit again.
The font of "Chiya Dam" on the wall looks stylish, like Hotel Okura.
To the top
The mountains upstream were covered with a light overall snow cover and were white. The wind seemed to be strong.
The spare gate of the conduit gate can be seen in the middle of the top edge.
The preliminary gate specifications are as follows
form (something takes) | Steel roller gate |
Door body width, door body height | W3.700mxH4.620m |
number of gates | two gates |
Opening and closing speed | 0.5m/min when hoisting, 1.0m/min when lowering |
door weight | 32t |
Completion date | March 1997 |
production | Mitsui Engineering & Shipbuilding Co. |
Downstream side is directly downstream in the middle.conduit gate(The design is a bit unusual in that it has a (jet flow gate) building. The notch in the middle of the sub-dam is not there to prevent water from the jet flow gate from hitting the sub-dam and damaging it...right?
The building will be a selective water intake facility.
The specifications for each are as follows
Intake gate | Water control gate | Lower gate | |
form (something takes) | Straight multi-step gate (5 steps) (Water intake 5 m3/s) | Steel Slide Gate | Steel Slide Gate |
Effective dimension | 3.5m wide by 38.5m high | 1.9m dia. | 1.9m dia. |
number of gates | (one) gate | (one) gate | (one) gate |
Opening and closing speed | 0.3m/min | Raise 0.5m/min Lowering 1.0m/min | 1.0m/min |
door weight | 77.3 tons | 5.1ton | 1.8ton |
Completion date | June 1997 | June 1997 | June 1997 |
production | Mitsubishi Heavy Industries, Ltd. | Mitsubishi Heavy Industries, Ltd. | Mitsubishi Heavy Industries, Ltd. |
Go to the right bank.
We have reached the right bank. The rain has stopped, but the footing is a little bad. Two concrete structures can be seen on the upper part of the slope on the left bank, which may be the remains of the foundation of a cable crane.
The same was found on the upper right bank.
In terms of design and function, it still does not look very much like a prefectural dam. There are two pavilions with tongari roofs on the downstream side of the top edge, and the roofs of the boatyard and the administration office are of a uniform color, which is also nice.
The upstream side of the embankment soaking wet. It was early in the morning, but no one was around except for us. This kind of winter atmosphere is surprisingly nice, isn't it?
downstream
Moving downstream from the top end level, we can see the conduit gate (jet flow gate) building. The downstream side is quite close to the embankment. It is quite a large building.
Notched, visible from the top edge.sub-damI'm not sure if this is a good idea or not. If you look closely, you can see that there are screened holes on both sides to allow water to drain out.
This is the Senya Dam intake and discharge facility building. The triangular glass roof eaves are a distinctive feature.
The specifications of the intake and discharge facilities are as follows
Main gate for discharge pipe
form (something takes) | Jet Flow Gate |
Effective dimension | 0.65m dia. |
number of gates | (one) gate |
Opening and closing speed | 0.05m/min |
weight | 12.8 tons |
Years of construction completed | June 1997 |
production | Mitsubishi Heavy Industries, Ltd. |
Sub-gate for discharge pipe
form (something takes) | Circular high pressure slide gate |
Effective dimension | 0.65m dia. |
number of gates | (one) gate |
Opening and closing speed | 0.1m/min |
weight | 9.7 tons |
Years of construction completed | June 1997 |
production | Mitsubishi Heavy Industries, Ltd. |
The orifice gate and discharge pipe used for the test flooding are installed as a monument in the plaza downstream. I had thought that the orifice gate would be used for the test flooding, but I was surprised to see a steel slide gate. It seems a waste to use the gate only for test flooding, but perhaps that is because the dam was constructed during the bubble period.
This is the Senya Power Plant (back side) of the Okayama Prefectural Bureau of Public Enterprises. For some reason, I did not take a proper picture of the exterior. The Senya Power Station is a dam-type power station that uses water from the irrigation discharge and can provide up to 3,000 kW of electricity.
From here, it is hard to believe that this is a prefectural dam. And it is huge.
Detailing begins downstream. The windlass room of the crest gate is well designed and built. The triangular roof overhanging the front of the top edge is the observation platform and is located on both the left and right banks. Below it is theorifice gateThe formwork is made up of a series of decorative forms. If you look closely, you can see the decorative formwork near the center and on the downstream face of the observation deck.
And a conduit gate (jet flow gate) at the bottom.
The Senya Dam was gorgeous in every way.
Senya Dam Specifications
Location | Sugo, Niimi City, Okayama Prefecture |
River Name | Takahashi River, Takahashi River System |
Objective | F (flood control, agricultural disaster prevention) N (unspecified water, water for river maintenance) W(Water for water supply) I (industrial water) P(Power generation) |
Model | G(gravity-fed concrete dam) |
Bank height | 97.5m |
Bank length | 259m |
Dam volume | 697,000 m3 |
Watershed Area | 88km2 |
Reservoir area | 111ha |
Total storage capacity | 28,000,000 m3 |
Effective water storage capacity | 26,200,000 m3 |
Dam operator | Okayama prefecture (Chuugoku area) |
Main body constructor | Obayashi Corporation, Kajima Corporation, Omoto Corporation |
Year of launch | 1971 |
Year Completed | 1998 |
Name of Dam Lake | Sensui Lake |
Other facilities/observations
Restrooms appear to be located in the administration office. The observation deck at the top end is marked as x because it is outside the definition of this site.
Parking lot | ○ |
Toilet | ○ |
Park | × |
PR Exhibition Hall | ○ |
Fishing | ○ |
Viewing platform | × |
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