We've got some +/-60 acre sites that we are cutting out for processing facilities and the client is requesting 3 benchmarks per site for the contractor. I am looking for recommendations for the benchmarks that don't necessarily need to be permanent, just get us through 6-12 months of construction (if even that long).
RR Spike in phone poles or trees won't work because those critters are rare in the area we'll be working (West Texas desert). Would rather not have to pour concrete as water is a limited resource and would have to be carried in. Soil can vary between rock outcrop or sandy loam or sandy, just depends on the site. Obviously the rock outcrops will be easy enough to mark just looking for suggestions of something cheap and easy but maybe a little more than a just a capped iron rod.
If the rock outcrop is stable, I would set a domed cap in the outcrop.
Again, the soil type varies on each site. There is no guarantee that there is any rock on all of the sites. Where there is rock, it will be easy enough. Quite possible that there is no rock on any of the sites. I haven't seen them yet.
How about a 3' section of 4"x4" post with a rr spike in a pre-drilled hole in the end buried flush. You can stamp control number or elev into the head of the spike.
That much mass should resist movement for your time frame. Adjust lengths as needed.
I don't know how you carry but you could tote quite a few on a four wheeler or pack them in.
No trees, no power poles, no water, just rock and sand, huh?
little more than a just a capped iron rod.
If you have a Cobra or other gas powered jack hammer, one guy can drive a rebar into just about anything to point of refusal. The right bit will round off the top of the rebar nicely. Plant one of those metal fence posts with the spade foot inverted a foot away and write your details on the spade foot part with nail polish, flag her up like a Christmas tree and away you go. Cheap, quick n easy. I'd stay away from caps, they're prone to getting knocked off or working loose. It is just a TBM after all.
Just because I'm paranoid, doesn't mean they aren't out to get me.
Here is a link to Google streetview of the typical terrain, except that it is probably 20 miles off the highway.
@31.7195752,-103.8177063,3a,23.8y,38.36h,85.28t/data=!3m4!1e1!3m2!1s1iLB7nkOKpCFj1of_DAi7g!2e0?hl=en"> https://www.google.com/maps/ @31.7195752,-103.8177063,3a,23.8y,38.36h,85.28t/data=!3m4!1e1!3m2!1s1iLB7nkOKpCFj1of_DAi7g!2e0?hl=en
No poles, no trees no water spouts,
Not a single luxury,
Like Robinson Crusoe,
As primative as can be.
That actually made me laugh out loud. I want to send that to my "engineers" when they ask me for a benchmark. Actually, i think i will. (the picture above Andys post)
> I am looking for recommendations for the benchmarks that don't necessarily need to be permanent, just get us through 6-12 months of construction (if even that long).
In sandy and clayey soil, I've been satisfied with how relatively well a 6'8" #5 rebar with aluminum cap performs. 6'8" is just 1/3 the length of a 20 ft. stick of rebar, nothing otherwise magic about it.
In expansive soils, I use a 36" length of 1/2" thin wall PVC irrigation pipe as a sleeve to isolate the upper part of the rod.
Installation consists of driving a 36" length of 3/4 in. pipe (with pipe cap on hammered end, pulling pipe with vise grip pliers, inserting PVC pipe sleeve, dropping rebar into sleeve and finishing driving rod with tee post pounder and sledge.
There wouldn't be any reason not to use 8' rebars if you have a means to transport them. The longer the rebar, the more important it is to have the tee post pounder to do most of the work, just finishing off the rod with the sledge.
"RR Spike in phone poles or trees won't work"
Railroad spikes in poles are illegal. Poles are owned by the utilities and are n ot public property. Spikes in them are a safety hazard for anyone who climbs them and they can cause structural damage to the pole.
I think a surveyor in NE Alabama was successfully sued for about $30,000 for damages.
We're gonna put thumbtacks in the greasewood for BM's.
FWIW, I don't spike utility poles.
> Railroad spikes in poles are illegal.
In Oklahoma spikes are in every pole within taping distance of a section corner and sometimes more than one. I'm sure it's the same in Texas. We don't put spikes in poles here in Oregon anymore either, but that's just one of the differences.
A 7 foot rod would do the job splendidly and remain stable for many years, but it seems like overkill for a single year. Any rod driven to a depth of about twice the depth of the deepest frost penetration should be good. Domed aluminum caps over a 5/8" x 30" iron rod would be quite sufficient, and installed with nothing more than a hammer. Adding the PVC sleeve is a nice touch if the soil is expansive and the budget bears it.
Okay, unless I'm missing something, I would just set 24-30" #5 rebar with control caps. I would assume that by benchmark the client actually 3D site control. Unless your project is in a swamp or straight up sand I don't see the need for 6' of iron in the ground or setting an NGS bench seems a little overkill. I've set quite a few bench marks to refusal and your in the $500 to $1000 range for each. Not something I would even thick about for 6 months.
> No poles, no trees no water spouts,
> Not a single luxury,
> Like Robinson Crusoe,
> As primitive as can be.
Not sure that scenario allows for a cheap solution.
Driving sections of rod screwed together down till your comfortable or point of refusal would be prefered as logistically that can be fairly easy.
Burying a RR tie, or large 6x6 post deep down should stay stable but the rod sections would be easier
> A 7 foot rod would do the job splendidly and remain stable for many years, but it seems like overkill for a single year. Any rod driven to a depth of about twice the depth of the deepest frost penetration should be good. Domed aluminum caps over a 5/8" x 30" iron rod would be quite sufficient, and installed with nothing more than a hammer. Adding the PVC sleeve is a nice touch if the soil is expansive and the budget bears it.
Except in some of the blackland soils in Texas, the problem is wet/dry cycle more than frost. In some of the highly expansive clay soils in Central Texas, the active zone of the soil can extend more than 48 inches down, a good clue being how deeply cracks form in the dry season. I've set 5/8" x 30" capped rebars and measured elevations differences in the range of 0.10 ft. from wet season to dry season, while the 6.7 ft. rebar on the same site was stable.
The PVC sleeve I use is really just a length of 1/2 in. thin-wall irrigation pipe that costs maybe $0.75 or less. It isn't one of the fancy sleeves and monument covers that NGS uses for driven rod benchmarks. The idea is just to keep the most active zone of the soil from getting a grip on the rebar.
> Unless your project is in a swamp or straight up sand I don't see the need for 6' of iron in the ground or setting an NGS bench seems a little overkill. I've set quite a few bench marks to refusal and your in the $500 to $1000 range for each. Not something I would even thick about for 6 months.
When you consider it takes less than 30 minutes to install a 6'8" capped rebar benchmark and maybe 10 minutes to get a 30" bar driven, capped, and stamped, the increment in cost is really more like 20 minutes, which seems quite reasonable to me given the enhancement in stability.
Updated Information
OK, I just got a new email from the client and it looks like these are going to be permanent benchmarks. We'll be setting rods driven to refusal, concrete collars and aluminum benchmark caps. Glad the client recognizes the long term value and is willing to pay the cost for a proper, permanent mark.
Sorry for the goose chase, I was going on the limited information I had at the time.
Looks like everything west of Big Spring to me. I agree with the previous posts, drive a rod to refusal and set your elevation.