Dive on the Submerged Old Waddell Dam in Lake Pleasant, AZ
September 30, 2000
Greg Porter


 
Aerial Photo Closeup of Aerial Exposed Dam Closeup of Dam

History:
When completed in 1927, the Old Waddell Dam was the largest concrete arch and buttress dam in the world.  It spanned 1,260 feet and was 176 feet above the deepest part of the stream bed.  In 1936 a roadway was added to the top of the dam.  In the mid-1980's the Central Arizona Project (CAP) folks decided to build a larger dam 1/2 mile downstream.  This new Waddell Dam was completed in 1992 - it is an earthen dam.  The new dam added tremendous capacity to Lake Pleasant, whose function is to be a storage facility for the CAP.  The CAP canal system transports water from the Colorado river to Southeastern Arizona. The new dam allows water levels to tower 100 feet over the top of the old dam by the end of March each year.  Water is pumped into the lake from the CAP canal all winter when power is cheap and water demands are lower.  During the summer the lake is drained to keep the CAP canals running.  The drainage continues all summer, at times exposing the top of the Old dam before re-filling begins in the fall.  Sometime in October the winter filling of the reservoir commences.  The fall of each year is the best time to reach the most interesting parts of the dam.
 

Safety:
3 months were devoted to researching the safety of diving this structure.  The main concern being it's proximity to the new dam's intakes and investigating any possibility of current being present that would suck a diver under the new dam.  In brief there is no danger of this.  I contacted the Bureau of Reclamation and acquired engineering drawings of the dam's current configuration and relationship to the new dam.  This complete lack of current was confirmed on the 9-30-00 141' dive in the area where a current would have existed had there been one.  The dive did reveal that structures thought to have been removed still exist - such as the 65' foot tall pump house and possibly the crane.  More structures may exist and can pose hazards, as they were never intended to be 'diver safe' at the time the area was flooded.  The concrete dam itself is structurally sound.

The 9-30-00 Dive:
Here's a view of the upstream side of the old dam when it was still in use. Here's a full view of the downstream side of the dam.  Zooming in a bit reveals a large building (the valve house) labeled 'building still intact' in the image.  The dive covered the area bounded by the buttresses (concrete dam columns) on either side of this building. Zooming in more is a close-up of the dive area and will provide the best reference for this narrative – note that the photograph is taken facing upstream and basically Northward. The circa 1936 image shows roadway support structure on top of the dam (now removed), buttress strengthening concrete shelves along the face of the left buttress, and the valve house. The water shooting from the bottom left of the valve house is coming from the outlet valve – the termination of the single penstock pipe that ran through the bottom of the dam.  Also pictured is a doorway to the right of the outlet valve, and the main doorway to the valve house, which is higher up against the right buttress where the round guardrail is.  Also pictured is an 18 inch diameter pipe that ascends above the house to the top of the dam along the right buttress face.  The crane assembly is out of the picture farther to the right. The scale of the dam is difficult to grasp.  The valve house is about 60' high – about 5 stories tall. From the top of the dam to the top of the valve is 140'

According to historical records all structures other that the dam itself were supposed to be removed prior to project completion.  The only structure expected to still exist was the penstock pipe and valve itself, as they were used to fill the area between the old and new dams during the initial 'new' lake filling in 1992. Before the old dam was initially submerged in 1992, a 240' dam section 70' deep was removed from the dam to allow safe boating during low water periods.  The 240' breach begins immediately to the left of the left column and continues left-ward, as shown in the previous zoomed out image. Reef buoys had been placed by the Lake Patrol at the top of each buttress along the entire dam's length to warn boaters.  A red buoy was placed above the column on the left in the image with a green buoy 240' Westward where the next column was located.

On the day of this dive (9-30-00) the water level was 6' above the top of the dam.  The descent began down the left column with 5 feet of visibility.  The water temp was 81 degrees. A thermocline was encountered at about 92 feet. The temperature dropped 22 degrees to 59 degrees and the visibility improved to 45 feet.  I'm confident in this figure as I recall being able to see at least 2 of the buttress strengthening shelves below me, which would set the visibility at 45-50 feet per the engineering drawings.  The view was fairly stunning, with a beautiful 16 foot wide concrete column descending into inky blackness.  The descent terminated 7 minutes into the dive at 141', just over the valve, where I spent 2 minutes taking a couple of pictures, which didn't turn out.  I think I had bumped the extension flash out of alignment sometime during the descent, so distance pictures didn't illuminate well enough – unfortunate.  The ascent was initially up the face of the valve house, where at about 110' I was surprised to encounter some overhead twisted structure.  In later dives I discovered that this structure was the road bed and support trestles that had been pushed off the top of the fat buttress on the right.  I never touched the structure due to the conservative ascent rate, and avoided it by moving slightly downstream, then came back in toward the building above it.  I then turned toward the left column near the top of the valve house, contacted the edge of the left buttress and began ascending it's face. The inside of the buttress began to curve to the right at about 100', where I took a pretty descent picture in the 45' visibility. I continued the ascent up through the thermocline to stop at 82'.  After a couple of minutes there I set a compass course in the now 5' visibility and crossed the 45' space to the right buttress.  This was just above the top of the valve house.  As I ascended the left corner of the right buttress I came to an 18-inch diameter steel pipe angling upward from left to right. I followed this pipe up and found that it was the vertical pipe in the image – it had been forcibly bent over like a huge straw at the point where it attached to a bracket holding the pipe to the wall.  Apparently it was bent over when the roadway above was pushed off this downstream side.   At 15-20 feet depth I took several pictures of the concrete pads that once supported the roadway trestle structure and also some 1 inch thick steel cable loops about 2 feet long that are cemented into the buttresses.  Surfaced 44 minutes after the start without a decompression obligation.

Later dives included a look into the valve house where poor visibility precluded seeing much - no penetration attempt made.  Also on later dives the extent of the twisted roadway's wreckage became more evident.  The trestle structure and roadbed lie in a tangled, disorienting heap against the fat buttress on the right and on top of the stairway and guardrail leading to the valve house door.  A 4 ft by 3 ft hole has been jackhammered into the downstream face of the fat buttress at it's base.  The buttresses are hollow.

With the lake level varying throughout the year along with the thermocline and improved visibility below it, Old Waddell Dam and it's beautiful architecture are available for all ranges of diving, from recreational to very technical.  Dive safe.

Anyone interested in more detail please contact me.  Over 100 images of the Old dam's initial construction can be found at the Library of Congress website. Type in 'Waddell Dam' in their search engine and then click on the first occurrence the engine produced.  Then click on the Black and White image icon that appears in the upper left.

Best Regards,
Greg Porter
greg@porter-az.com