Question
Crazy question. I have a 16' wide x 70' long trailer as a vacation home in Wild Rose, Wisconsin. The campground/mobile home park is in a pine tree grove. This summer I installed landscape timbers around the entire trailer about 18" out from the trailer. Then I filled in between the trailer and timbers with lava rocks. It looks great. I did this because Wild Rose is in the sand belt of Wisconsin and every time it rained the trailer would get all dirty and messy with sand about three feet up. Everything was fine until fall came around. Pine needles fell everywhere including into the lava rocks. I am not talking about just a few needles but literally at least two inches worth. The problem is how do I get the pine needles out of the lava rocks? I can rack out just so many until the lava rocks start coming out as well. I've tried alot of things from vacuming, sticky tape and even burning with a small propane torch! Everything that I've tried works small scale but would take months to finish the job. Any suggestions other than taking out the rocks and replacing with a skinny "deck" of pressure treated wood around the trailer - my backup plan.

Answer
Jim,

A couple of suggestions short of construction...

I hesitate to use the 'B' word, but have you tried a blower?  I'm not sure how big  the actual rock is (we call it dogfood), but if it's big enough, you can blow a lot of the needles out.  But this doesn't mean blasting.  You need to find the speed that falls between "strong enough to blow needles" and  "not strong enough to blow rocks'.  If the lava rocks are too small, there won't be much of a difference.

So that brings the next suggestion (which doesn't help you this year)...if it's available, get the lava a size larger, so that blowing difference is  bigger.  You wouldn't need to replace all  the rock.  Just get a covering of the larger chunks to give you a blower buffer.

Or...since you know when the pines drop needles. .. How about next year covering the rock with some netting, like the kind that's used by sod farmers, or bird netting used by orchards.  You can get it in rolls.  Cover the rocks just as needles  start to drop, and you should be able to lift off the net and needles after the month/6weeks of falling.  Then roll up the net & store it for the next year.

I had this problem on several flat roofs.  I'm not sure why, but someone decided to surround drains with LOTS of small dogfood lava rock.  I had to get rid of a combo of oak leaves and ponderosa pine needles.  I eventually had to shovel it into 5 gal buckets, fill them with water and float the junk away, empty the clean rock, and do it again.  Bucket by bucket it worked, but I wasn't happy at the end of that day.

For what it's worth.
Mark in Portland