Good morning all.
I have been tasked to layout solar array tables on an existing capped landfill. The landfill has a membrane liner just below the surface of the ground, therefore I can't see using spikes or wooden stakes to mark out any layout features for fear of puncturing the liner. Unfortunately I do not know the depth of the liner, and if I did, if the depth is consistent throughout the entire site.
For those who may have staked construction features on a lined landfill before, what sort of maker(s) have you used that has some level of permanence between the time of layout and construction? Not knowing the time between when I stake the locations and actual construction, I don't think just painting a spot on the grass with a label will last.
Thanks for your suggestions and ideas.
From my experience working on landfill projects, the liner should have a significant amount of cover over it. Have you discussed depth with the operator?
If for some reason there is not reasonable fill, you could try to set some substantial chunks of concrete or metal that won't move and that you can mark. Just a thought.
Ask for construction drawings of the capping project. Typically the liner is installed first in the pit, much like an inground swimming pool. If the cell is capped, the liner should be way below the work area. The finish cap may be a clay lens, and not much else. The cross sections will tell the tale. If that is the case, stakes will be appropriate.
Thanks for the quick replies so far. Having not worked on a finished landfill before, I appreciate your comments as they will help in the questions that I need to ask the operator/municipality.
I was assuming that there should be enough fill over the liner that a wooden stake or hub could be driven down without damage. I would also assume that the liners are rugged enough that even if they were shallow, I should feel the resistance when hammering the stake, and stop.
Thanks again.
Communication is key.
I would personally probably use 1" x 2" x 6" long wooden hubs w/tacks.
The contractor installing the solar array is responsible for preservation of existing property - if you are working for them, get something in writing.
I would guess either there is already significant cover (3') or they will be bringing in additional fill as part of the construction.
The liners are pretty durable. This is a end view of a field weld.
The responsible agency, will have as-built surveys of the liner surface, and the top surface. They will also probably have a monitoring survey to detect settlement.
Wall Walker, post: 365498, member: 7427 wrote: Good morning all.
I have been tasked to layout solar array tables on an existing capped landfill. The landfill has a membrane liner just below the surface of the ground, therefore I can't see using spikes or wooden stakes to mark out any layout features for fear of puncturing the liner. Unfortunately I do not know the depth of the liner, and if I did, if the depth is consistent throughout the entire site.
For those who may have staked construction features on a lined landfill before, what sort of maker(s) have you used that has some level of permanence between the time of layout and construction? Not knowing the time between when I stake the locations and actual construction, I don't think just painting a spot on the grass with a label will last.
Thanks for your suggestions and ideas.
Just a dumb question here:
If you need to worry about damage to the membrane just staking the array tables, how the heck are they going to install the footings for those tables without penetrating the membrane? Are they gravity mounted? If that's the case, you can "gravity stake them":
Gently cut these into the turf once the approximate spot is staked; then scribe a cross with your portable Makita diamond saw; and write on the block with the info if needed.
http://www.homedepot.com/p/12-in-x-12-in-Pewter-Concrete-Step-Stone-71200/100333077
Wall Walker, post: 365507, member: 7427 wrote: I was assuming that there should be enough fill over the liner that a wooden stake or hub could be driven down without damage.
Make sure and ask to see the Design of Racking and Foundations. That should answer your question. B-)
From my experience working with the landfills in my area, there is a minimum required clay cover over the plastic liner of 2', and then an additional 3' of soil cover over the clay (I may have those two figures backwards). However, if you don't feel comfortable driving anything down too far, might try using a 20D or even a 10D nail, along with a pinflag marked with your cut/fill & info. Carry a pair of pliers or Vise-Grips in your pocket, helps to stick flags in stubborn ground.
I'm with some of the other folks here though, I'm wondering how they plan on installing the solar assemblies if the liner depth is an issue. Not to mention, a couple feet of soil on top of a plastic liner doesn't seem like the most laterally stable surface to use for that kind of thing.
When we surveyed in the piping and weirs installed on the liners of evaporation ponds we gave line and grade to the contractor at the time of construction. This was deemed necessary so as to avoid damage to the liner that any prior staking would cause. Our company negotiated a hourly rate for a three man crew using transit and level, (this was before GPS, which I imagine would simplify the operation today). I'd approach the owners and contractors with your situation and perhaps you'll end up with larger payment for services rendered. Good luck.