Benchmarks At Hoover Dam

[+G-Squad]

This past weekend, my wife and I celebrated our 15th wedding anniversary in Las Vegas. On the drive there from Phoenix, we decided to stop at Hoover Dam. While there, I found several benchmarks on the top of the dam so I took photo's of the ones I found. Now that I am home, I want to log them in at Geocaching.com. The first mark I found had "Nevada Base" designation so I did a search on that. Lo and behold, two PID's came up on the search--- GR0578 and GR1854. I checked the NGS website datasheets. The datasheets are worded differently but are sufficiently close to describe the same mark.

 

Are they the same mark?

 

If they are the same mark, then I will log one as "found" and make a reference to the other PID. On the other PID, I will post a note referencing the first. I would do this as you can't "find" the same mark twice, right?

 

So, which PID should I log as found and the other as a note?

[2oldfarts (the rockhounders)]

It appears as though there are 2 different benchmarks. One is in the sidewalk and the coordinates are adjusted and the other is in a designated block of concrete and has scaled coordinates.

 

GR1854 is adjusted so the GPSr should read 'very' close to the given coordinates.

 

Hope this helps.

 

John

[Wild T2]

Given these two comments from the description...

 

ON TOP OF HOOVER DAM

 

and

 

STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY

 

I am sure glad that I do not live downstream of there.

[+Kordite]

MARK OF QUESTIONABLE OR UNKNOWN STABILITY

My wife was inVegas a few weeks ago and went to log the marks on the dam. Judging from the picture, I thought the "questionable stability" comes from the fact that it is set in an asphault sidewalk which shows signs of cracking. I could see this getting broken up and re-paved in the future, thus the stability issue.

 

It is pretty funny, though, to have that comment for a mark on Boulder Dam.

 

Hey, did you know that there is no re-bar in that structure.

[+G-Squad]

It appears as though there are 2 different benchmarks. One is in the sidewalk and the coordinates are adjusted and the other is in a designated block of concrete and has scaled coordinates.

John, I still think they are the same one. The monumenting note from 1935 for GR1854 states it is on a sidewalk. The distances given in the note also fall in line with the mark. However, that is the last note from the NGS on this PID.

 

Oddly, the description for GR0578 is missing the monumenting note from 1935. But, in 1950, the NGS notes the mark is in the concrete floor of an observation niche. That is where the mark is located. Further, the measurements from the east wall and the north edge of the SIDEWALK all match-up also. The NGS notes good recovery in 1963 and 1981.

 

So, my theory is they are one and the same. Somehow there was a mix-up in the documentation. I also noticed most of the benchmarks are in a series as "GR05xx". I think this was the original designation so I am going to log this one as found and note the other one as being the same. I may be wrong but that is how I am going to log them on geocaching.com.

[2oldfarts (the rockhounders)]

GeoGeorge,

 

We will be in the Vegas area on vacation next week, if you would like us to go take a look & maybe help document your findings, we would be more than happy to take a little side jaunt. We are not retired surveyors, but we do have a little experience in tracking the disks down.

 

~Shirley & John~

[+GeckoGeek]

What's interesting is that GR0578 is listed as a "triangulation station" even though the coordinates are SCALED. I'm suspecting a paperwork screw-up or the original triangulation station was also made into a real vertical bench mark and the dual paperwork came from that.

[+Me & Bucky]

Hi GeoGeorge,

 

I've been to the dam several times for the sole purpose of finding the benchmarks that are on the top. I've also looked for the benchmarks that are inside, but this is much more difficult now that the tours are more restricted.

 

I think it is highly likely that your two NEVADA BASE PIDs are one and the same. I've looked for the duplicate NEVADA BASE disk on both sides of the road, but only found the one in the niche off of the sidewalk.

 

As far as trusting GPSr to lead you right to an ADJUSTED benchmark, the dam is in a fairly steep canyon and even with several satelites, there is a good chance of getting some funky signals.

 

I've never seen a place that was more loaded with benchmarks than the top of Hoover Dam (the Capital Building and the White House are notible exceptions, but just try getting in there to record them! ). A methodical 2-hour walk around the top of the dam and nearby spillways will yield you around 20 benchmarks.

[2oldfarts (the rockhounders)]

I am wondering, since all of the increased 9/11 security thing, are people with GPSr's & digital cameras hassled at all? We live close to Glen Canyon Dam/bridge & they seem to gone overboard on who to watch...they are used to seeing us with our GPSr, but we are well known to everyone here. I would hate for anyone looking for benchmarks to get stopped & harassed by local security guards at Hoover Dam.

 

Has anyone have any problems at all?

 

~Shirley~

[+G-Squad]

Me & Bucky, when I went to the dam, I had no idea there were benchmarks all over it. I didn't use my GPSr to try to find them. I, uh, stumbled upon them. I only walked across the top along the downstream from NV to AZ and then back along the lakeside. I nabbed about 6 or so as the pedestrian traffic would sometimes overflow into the street while I was taking the photos. Safety first!

 

Shirley, first let me apologize for not responding sooner to your previous offer. My desktop blew a circuit the other day. I finally pulled out the laptop and took the desktop in for repairs. Although I didn't use my GPSr to look for marks, I still had it out and clipped to my pants pocket. I also took digital photos of the marks I found. Nobody blinked twice or said word one to me. As for your offer, I appreciate it but you don't need to check it out. I am comfortable with my thought that the PID's are one and the same. Thanks for the offer.

 

AJ

[+Me & Bucky]

I would hate for anyone looking for benchmarks to get stopped & harassed by local security guards at Hoover Dam.

 

Has anyone have any problems at all?

 

~Shirley~

 

I've had no problems whatsoever, and that includes me with the digital camera, GPS receiver, binoculars, and 60x spotting scope.

 

I think you would have a good time if you stopped off at the dam while you were next door in Las Vegas.

 

By the way, here are a couple more marks that I think it likely to have been duplicated:

 

Triangulation Station A (GR1863 and GR0581)

Triangulation Station B (GR1850 and GR0585)

 

Possibly Triangulation Station C (GR1849 and GR0598). I haven't seen this one, but the two descriptions sound similar.

 

If you make it to the dam, it would probably be good to check these out as well.

 

The best way I've found to search for marks here is to not use your receiver, but to just walk from one side of the dam to the other, cross the road, and walk back to the side you started from. I only used my receiver to record where the marks were, but with the close canyon walls, closeness of the benchmarks, and overlap of signal, I think it would be difficult to use your GPSr to find the marks.

 

Best of luck to everyone who looks here. It is a great place!!

 

Finally, GeoGeorge, HAPPY ANNIVERSARY!