Today I planned to stay relatively close to home and do some Survey Mark Hunting. I mentally divided up my day into equal parts and headed over to Rancho Cuyamaca State Park with three primary objectives in mind
Pick up some "Drive-Bys" or opportunistic recoveries along a 2.5-mile stretch of SR 79 that is southeast of North Peak and northwest of Lake Cuyamaca
Hike to Fletcher Island High Point to bag the peak and explore the special survey marks along the trail (Post opens in new window)
Summit Stonewall Mountain and recover Reference Mark 1 for the Cuyamaca Azimuth Mark (Post opens in new window)
Part I: "Drive-By" Recoveries
I like to call these Drive-Bys because they're usually right along the roadside and are likely survey marks related to the placement of the road system (past or present). These are generally noted on the Topographical (Topo) map with a large "X", the initials "BM" (Benchmark), and the observed elevation (as in the first photo below).
Sometimes I'll just drive with my GAIA Topo Map up in navigation mode, but I also check the National Geodetic Survey (NGS) Data Explorer interactive map to look for potential marks along my route or at my destination (second photo).
These are 'Opportunistic' recoveries because they don't require going too far off the beaten path and are usually easy to locate. Either one (or both) of the aforementioned methods can be spot-on accurate within inches, or they can be off as much as 50-feet in any direction. It's the "usually" that makes hunting for these marks challenging.
Today I picked a 2.5-mile stretch of SR 79 that wraps around the southeastern base of North Peak. On the Topo map, it appears as if this section of road also parallels the northwestern border of Lake Cuyamaca, however the actual size of the lake today is just a fraction of what is depicted on older Topos.
Of the seven marks on my recovery list, I had previously found two of them on my way to hike Cuyamaca Peak last month, I'd had my Topo map up, and they were right where they were supposed to be. For the remaining five I pulled the coordinates from the NGS Explorer site and the respective datasheets. This map, with waypoints showing the coordinates for each mark, and images of the survey markers I found, is a good visual reminder that survey marks are all over the place.
Previous Recoveries from January 4, 2021
1343+71.88 4658.11 USDA BPR 1936 (PID: DX0178)
M 308 1935 USC&GS Benchmark (PID: DC0540)
U.S. Department of Agriculture, Bureau of Public Roads Benchmark Disc
This is the first mark that I’ve found that was stamped U.S. Department of Agriculture, Bureau of Public Roads (which operated under that name from 1918-1939) its predecessor agencies dated back to 1893, and the Office of Road Inquiry. Ultimately its functions would be absorbed by the Federal Highway Administration under the Department of Transportation in 1970.
According to government archives, the primary functions of the Bureau of Public Roads included: Supervise the cooperative federal-state highway construction program. Administer the highway beautification program and the highway construction phase of the Appalachian regional development program. Construct defense highways and roads in national parks and forests. Conduct research in transportation and highway design.
The stamping on this mark shows that it was set in 1936, notes the elevation of 4,658.11 feet, and provides the station and offset (1343+71.88) Initially I didn't understand what the station and offset were, but after posting a picture of the mark in a surveying group on FB, I received a quick reply explaining the numbers, which led me down yet another path of research. The station and offset are common markings on a highway project. This marker is 71.88 feet past station number 1343 on the plans for this roadway. A "station" is a segment equal to 100 feet. Station numbers usually increase from the beginning of the project to the end of the project. Also, stationing usually runs from South to North or from West to East. I learn something new every day!
This mark was accompanied by a witness stake (that coincidentally had a State Park Boundary sign attached. While this looks like a traditional 3" brass benchmark disc, it's actually a 2" bronze pipe cap style of marker.
U.S. Coast & Geodetic Survey Benchmark M 308 1935
This was an easy recovery and it surprises me how many I have found along roadways like this, relatively undisturbed, and still in amazing condition. However, mounting a standard disc in the top of a concrete monument such as the one shown here offers the lowest level of anticipated stability (C - May hold, but is of the type subject to surface motion). Unfortunately, I have also found the remains of many broken monuments where the discs have been removed.
The number 308 is a reference to the surveying job that included setting this marker, other marks along that project will the same number and will have increasing alpha designators along the line (ascending from East to West). I would end up finding two more marks on this line today, L 308 and P 308.
Today's New Recoveries
As I mentioned above, I found two more benchmarks in the '308' series, the first one L 308 (PID: DX0177) was obviously marked with paint on the rock it was mounted in. It was just off the road and not too far away from the BPR disc I found last month. The second was P 308 (PID: DC0546), which while not on this section of SR 79, was part of that same survey job labeled 308. It was located further down the road, in front of the Rancho Cuyamaca State Park Headquarters building, a few hundred feet south of the Paso Picacho Campground entrance.
Tips and Tricks
I have put together a small kit that I use to make it easier to photograph the markers that I find. Of course, I have my trowel and a long screwdriver that I can use to probe the ground for marks that may be slightly buried, but so far I've only had to dig for one mark.
More often than not, the bronze or brass discs are tarnished and dirty, the stamped information can be difficult to read if the disc is weathered or debris fills the stamped information.
I carry a small brush, bandana, bottle of water, and a travel-size bottle of liquid chalk (used for climbing or weight lifting). I use the brush and water to clean off the surface of the disc, get the dirt out of the recessed stamping.
I cover the disc with the liquid chalk, let it dry some, then wipe the surface off with bandana, leaving the stamped info highlighted in the white chalk. When I'm done, I splash some water on it to remove the chalk residue. This worked really well with the L 308 marker as you can see above.
San Diego County Monuments
The next two finds were both standard brass San Diego County Engineer Department Survey Monuments. They differ from the typical slightly domed discs because they have a raised button in the center, with a stamped hole in the middle for placing the surveying tool. Mark SY 107 1969 (PID: DX0176) was easier to locate as the witness stake was nearby, still this mark was 50-feet WSW of the coordinates on the NGS datasheet. CY 75 1969 (PID: DC0541) was even further off the mark, 205-feet ENE of its stated coordinates.
Most people would think locating these with the GPS coordinates from the datasheet is easy, just plot the coordinates and proceed to the route. I am finding that more often than not, I am relying as much, if not more, on the original descriptions of the mark placement in order to find them. When I reached the coordinates for CY 75, there was no boulder nearby that fit the description of the mounting position in the datasheet so I kept looking for the rock outcropping that fit the description.
Unable to Locate and Lost/Destroyed
It seems like there are always some marks that I can't find and today was no different. I was unable to locate CY 77 1969 (PID: DC0538) even after wandering around the field well beyond the state coordinates. Perhaps next time I'm out this way I'll stop and look again, but I was doing well with other recoveries and still had a lot more on my plate for the day so I gave up on this one for now. Just as there are those I can't locate, I always seem to find evidence of a mark that has been lost or destroyed. CY 76 1969 won that prize today. Again, the coordinates weren't really helpful, this was 312-feet NNE of the supposed location. Thankfully, part of the description referenced it as [sic] "SIX FT E OF 17 FOOT LONG BY 2 FOOT WIDE BY 6 FOOT HIGH GRANITE BOULDER." Once I found that boulder, it was easy to see where this mark USED to be.
Overall, the day started off well, with four new recoveries and a confirmed lost/destroyed mark. From here it was just a short drive around the lake to the trailhead for Part II of my day, bagging Fletcher Island High Point.