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Details for Benchmark: HS3879

N 37° 39.900 W 121° 44.117 (NAD 83)

Altitude: 599.7

Coordinates may not be exact. Altitude is VERTCON and location is SCALED. (more info)

Location:
In ALAMEDA county, CA View Original Datasheet
Designation:
118 A CO
Marker Type:
survey disk
Setting:
set into the top of a round concrete monument
Stability:
May hold, but of type commonly subject to surface motion.

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Found where described. Geocaching has not updated the benchmark pages and lots of things have changed but a reset in the same location as the original is okay by me

[Photos:]
photoFor reference
photoEye level
photoMark

Lots of questions on this one - I would be very hesitant to call it DESTROYED. The DS

"HS3879_STAMPING: 118 118
HS3879_STABILITY: C = MAY HOLD, BUT OF TYPE COMMONLY SUBJECT TO
HS3879+STABILITY: SURFACE MOTION
HS3879
HS3879 HISTORY - Date Condition Report By
HS3879 HISTORY - UNK MONUMENTED CA-001
HS3879 HISTORY - 1961 GOOD NGS
HS3879 HISTORY - 20091127 MARK NOT FOUND GEOCAC"

indicates that it's designation '118' was stamped twice, which the photo's clearly show. I doubt that this double stamping would have carried over if a new disk
was placed. Looks like the call from the fence and WP is correct. How about the distance from the '55 FEET EAST OF A POWER POLE,'?

Does the road show recent widening? In which case maybe the entire post was moved and would require a new PID. In the documented cases that I have seen where this was done the replanted post shows some uneven settling.

Maybe the original was occupied in 1990 and it checked out for elevation, at which time somebody stamped the RESET 1990 but did not follow up with a recovery to NGS. These 'clerical errors' are rather common.

I sure do agree with Wintertime! The benchmark disk is clearly marked 1990, so how can it be the one on the datasheet, placed before 1961. Come on, folks! Just match up the descriptions. The disk described is very likely destroyed, and replaced in 1990 by the one pictured. As the disk cannot be at exactly the same location (vertically, in this case), the original disk is considered destroyed, and a new entry in the NGS database is normally made by the placing agency. In this case, the new database entry in 1990 was not made,

[Photos:]
photoCloseup of the horses in the corral behind HS3879
Pretty horses!
photoHS3879 Reset location
photoReset of HS3979 near Livermore CA
Pictured disk is the reset. The disk documented as HS3879 (118 A CO) is very likely destroyed.

Klemmer and I were just about to call it day with benchmark hunting and wine tasting when he spotted HS3879 on his GPS. It was right near where we were, so we went to look for it.

The benchmark now at this location is not HS3879. It is a reset mark monumented in 1990 by Alameda County. So HS3879 was destroyed sometime before that.

Coordinates are a little off. Better coordinates are: 37 39.913 N, 121 44.130 W. It's an easy find if look in the right place. Follow the NATIONAL GEODETIC SURVEY description and you won't have any trouble.

[Photos:]
photoBenchmark A Co. 118

My GPS took us to the wrong side of the road, took a little longer than expected, but once we realized that part, it was quick.

Finding the benchmark was easier than finding legal parking nearby where I wouldn't get mowed down by traffic. Neglected to get an updated photo, however it looks the same as the photos in previous logs.

That was an easy one (finally).

Located benchmark today about 1:00 pm.
Green Peas

[Photos:]
photomini dsc 00115.jpg
N 37° 39.913 W 121° 44.130

GPS readings showed within 16 feet of accuracy.
Located as described in 1961 description.

T&J (Scoobywatchers)

[Photos:]
photoWitness Post HS3879
photo118 A CO

Documented History (by the NGS)

Unknown by CA-001 (MONUMENTED)
01/01/1961 by NGS (GOOD)
DESCRIBED BY NATIONAL GEODETIC SURVEY 1961 2.2 MI SE FROM LIVERMORE. 2.15 MILES SOUTHEAST ALONG TESLA ROAD FROM THE POST OFFICE AT LIVERMORE, AT THE T JUNCTION OF BUENA VISTA AVENUE NORTH, 33 FEET NORTH OF THE CENTER LINE OF THE ROAD, 93 FEET WEST OF THE CENTER LINE OF THE AVENUE, 55 FEET EAST OF A POWER POLE, 1.0 FOOT SOUTH OF A FENCE, 0.6 FOOT WEST OF A WITNESS POST, ABOUT 1 FOOT HIGHER THAN THE ROAD, AND SET IN THE TOP OF A CONCRETE POST PROJECTING 0.3 FOOT ABOVE THE GROUND.

Control Text

  • The horizontal coordinates were scaled from a topographic map and have an estimated accuracy of +/- 6 seconds.
  • The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.) The vertical order pertains to the superseded datum.
  • The geoid height was determined by GEOID99.

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