Ortega Highway Scavenger Hunt
Updated: Apr 10, 2021
In the Survey Mark department, today was a successful day with 7 total recoveries, 3 on the summit of Sitton Peak and 4 located along SR 74 - Ortega Highway. The term 'Recovery' simply means finding the physical survey mark, verifying its location, and in the case of hobbyists like me, photographing the mark.
Survey Markers are also referred to as Monuments, in the Glossary of BLM
Surveying and Mapping Terms, the Bureau of Land Management defines a Monument as
"A physical structure, such as an iron post, marked stone or tree in place, which marks the location of a corner point established by a Cadastral Survey. Objects, to be ranked as monuments, should have certain physical properties such as visibility, durability and stability, and they must define location without resorting to measurements."
Today, a typical survey mark or monument is a brass, bronze, or aluminum disk or rod. Over 1.5 million permanent monuments are cataloged and tracked by the National Geodetic Survey (NGS). According to the NGS, these monuments have been placed by NGS, its predecessor agencies, and other organizations since 1807. Surveyors use these monuments to establish accurate location and elevation information that is important in engineering projects, determining property boundaries, and is an integral part of the Global Positioning System (GPS). Permanent monuments are protected by Federal and State laws as they are critical to the protection of private property rights and public infrastructure.
As I dug deeper into the surveying process and monuments, I started paying closer attention to my Topo maps as they provide a lot of information about the location of a wide variety of survey marks. Benchmarks are commonly noted on USGS Topo Maps with an "X" at the point of the reading, the letters "BM" and the elevation, usually in imperial feet.
Driving down the road with my GAIA GPS on (much like I'd use Google Maps for navigation) I could see upcoming benchmarks along my route. I'd make a quick determination to see if I could safely pull off the road and look for the mark. Safety is paramount, if the location is on a busy road and there's no shoulder, turnout, or side road where I can safely park, I'll just pass by.
A common practice when setting monuments is to also place some form of a witness stake close by (generally within a foot or so) to facilitate finding it in the future. Learning to scan for potential witness stakes can make it much easier to locate the actual monument. As you'll see in the galleries below, all four of the monuments I recovered this afternoon had a witness stake, three of the four were visible from the road without having to get out of the truck.
As I started locating these roadside monuments I dubbed them 'opportunistic' recoveries or 'drive-bys' as they generally didn't require a lot of work to find.
Ortega Highway Recoveries
I found three different types of monuments along the Ortega Highway as I headed home from Sitton Peak, a standard 3" Brass Disc mounted in a rock outcropping, a 1 ½" pipe cap (likely set in a 24" galvanized steel pipe driven into the ground, and a chiseled "X" in bedrock. This was the first time I've recovered a mark chiseled in the rock!
Two of the marks I found were Caltrans Survey Monuments (likely part of a Caltrans Right of Way Survey) these are the pipe cap style. Interesting that Monument 110 was located at almost exactly the same coordinates and elevation as a registered NGS Benchmark P 313 1935, PID: DX1742. The NGS monument was a 3" Brass Disc mounted on the top of a concrete monument. I didn't see any sign of the NGS marker or the concrete monument it would have been mounted on. The MON 110 was in a hole about 6" deep filled with loose rocks and trash. One of the things I like about this new hobby is where it takes me. While researching Caltrans Monuments, I came across this Basic Surveying Guide it's a training aid meant for surveyors, but finding documents like this helps me learn more about the surveying process that ultimately results in these monuments being set.
Some 'Drive-By' recoveries are almost TOO easy to find as in the case with N 313 1935, PID: DX1741. This was set near the back of a turnout area at the base of a cliff wall, some surveyor wanted to be sure everyone knew where this one was! 🤣
And finally, my "new" recovery of a chiseled "X" in the rock. This is another one that was close to where another NGS monument should have been, M 313 1935, PID: DX1740, also a 3" Brass Disc mounted in the top of a concrete monument. I didn't have the exact coordinates of the NGS monument with me but plotting it when I got home indicated it may have been about 200 feet further south than this one was. Maybe next time I'm out that way I'll look for M 313.
This was the only one of my finds that WASN'T right along the road, I had to pull off the shoulder and go about 80 feet into the weeds to find it, as is the case with many of these, there is often a path beaten down by previous surveyors or Geocachers searching for the mark.
All in all, a good day for finding survey marks!