I've been slowly trying to get stuff figured out for testing a wind fence set up at LHO, and am getting ready to try to set something up. I'll summarize where I think things are here.

Currently, I want to try a small, cheap wind fence at EX, mostly to explore how effective screens are at slowing wind, effects on ground motion and tumbleweed build up. The fence would be a couple of 4x4-ish 12-15 foot posts and some fine polymer netting like that used around tennis courts, gardens and the like. It may be necessary to add guy lines, as well.  In addition to the fence, Richard has said he will help me get an STS buried at EX, similar to Robert's set up at EY, and we are ordering 3 anemometers with stand alone data collection so no changes need to be made to CDS for this. I think this set up will allow me to look at a few of the concerns that people have brought up. So far the concerns I've heard are:

1. Increased ground motion. Fences slow wind by applying a force to the airstream, this is transmitted to the ground and produces increased tilt and other high frequency motion. I think the tilt can be addressed by placing the fence some few tens of meters from the building, per Robert's measurements of building tilt. Higher frequency motion can hopefully be addressed by design of the fence support structure, but we'll have to see how bad the motion is.

2. Similarly, the fence could make airflow more turbulent. I suspect that airflow at the building level is probably turbulent anyway. Hopefully, a well designed fence push turbulent flows around the building, while slowing most of the air makes it through.

3. Tumbleweed build up. Anything that blocks the wind will gather tumbleweeds around here, which could make a fence a fire hazard and maintenance issue.  This  could be addressed by leaving a gap at the bottom. The airflow below a few feet probably isn't a significant source of problems for us, but I don't know how big this gap would need to be. I also plan on using a mesh fine enough that tumbleweeds won't stick to the fence very easily. Industrial fences are flame resistant, and won't ignite on their own.

4. Wind damage. We have seen winds above 100 mph during a storm, this would create very high loads on any fence. I haven't been able to figure out how to calculate wind loads on a permeable wall yet, but Civil Engineers have building codes dealing with this. For my test, I'm trying to get some idea of the loads involved with moderatewind, and just making the fence so that the mesh will tear free in a way that won't damage the EX building if the wind gets too bad. Industrial fences are designed to stand similar wind loads, and their screens are held in place with replaceable break-away clips to prevent damage.

5. Cost/size. BrianL talked to a company that makes industrial fences a few months ago. The ball park figure for a 40 x 200 foot fence was about $250,000. That was a first pass at a price and the company had some suggestions at how to cut down on the cost. This price also needs to be weighed against the 10-15 % of down time we have due to wind. Something of that size would also probably have to be approved by the DOE. It's also unclear if we would have to completely surround each endstation, or if we could get away with less coverage. Probably, we don't need to "protect" EY along the X-axis, or EX along the Y-axis.

Comments, criticism, praise are all welcome.