The Khun Dan Prakan Chon Dam was completed in 2005. It is 93m high, 2720m long and an incredible 5.5 million cubic meters of concrete. It has a storage capacity of 224 million cubic meters of water. It is the biggest dam in Thailand. It is also the largest and longest roller compacted concrete (RCC) dam in the world.
The Khun Dan Prakan Chon Dam was originally named the Khlong Tha Dan Dam. The Thai authorities subsequently changed the name to the Khun Dan Prakan Chon Dam, which is the stream that flows from Heaw Narok Waterfall. You may still see some road signs pointing to Khlong Tha Dan Dam but most now call it the Khun Dan Prakan Chon Dam. They are the same place.
His Majesty King Bhumipol initiated the dam project. Nakhon Nayok had long suffered from a cycle of floods and drought. The resulting poor acidic soil caused Nakhon Nayok's farmers great hardship and occasional flash floods had claimed many lives.
His Majesty the King, highly revered by the Thai People, was aware of the suffering this cycle was causing to the people of Nakhon Nayok. He personally came to inspect the area in 1993. He spoke to local people about their problems, inspected the area on foot and by air. He concluded that a water management and irrigation system could solve many of Nakhon Nayok's problems and initiated the Tha Dan Dam project. Construction of the dam commenced in 1999.
The dam was built using the roller compressed concrete (RCC) technique. This involves adding lignite fly ash to the cement mix. This improves the fluidity and workability of the mix while reducing the amount of cement needed, so reducing material costs. The mix is then compacted by rollers to create a very strong concrete with excellent long-term resilience.
The benefits for Nakhon Nayok include:
The lives of Nakhon Nayok's people have already improved with the completion of the dam. Tourism and agriculture revenues are up and local land values have jumped sharply as investors look to cash in on the booming tourist industry.
Dams are rarely architecturally beautiful but the sheer scale of these constructions makes them an impressive sight. Visitors can go to the top of the dam and enjoy the spectacular scenery. There is a small park by the top and from there you can walk a few hundred meters along the top of the dam.
You can take a tour bus trip along the top of the dam to fully appreciate the fine views and the scale of the construction. The 15-minute trip costs 20-baht.
There are great views either way. In front of the dam, you have a view along the river and across Nakhon Nayok province. Behind the dam is the reservoir. It is possible to take a boat trip a few kilometers along the reservoir to the stream that feeds it.
You can also take a boat trip across the lake and up the river behind the dam into Khao Yai. How far you can go depends on how high the water level. When the water level is low you can travel just a few kilometers but if the damm is full you can travel many kilometers up the river and into the jungle. These boat trips also include the chance to do a short trek into the jungle to one of the small waterfalls with drop pools for a refreshing swim in the cool waters.
You will see the boats at the lake edge and the drivers will be waiting in the sala nearest them. The trip costs from 1,000-baht to 1,500-baht.
There is a nice museum at the base of the dam that gives lots more information.
The Khun Dan Prakan Chon Dam is located at Ban Tha Dan, Tambon Hin Tang. From Nakon Nayok town, take route 3049 north towards Nang Rong Waterfall and the foothills of Khao Yai. 12km out of town the road forks and you need to take the right road. It is not long before you get sight of the huge dam. Drive on for another 6km and you reach the right hand turn, signposted towards the dam. When you reach the traffic circle with the elephant fountain in the middle you turn left and climb the hill to the top of the dam.