What type of leach field??? I assume it is not a sand mound. If it is a sand mound, or similar type, the roots will most likely grow under the distribution pipes. If properly designed and installed, the drainage should be fairly even throughout the leach field. Copper sulfate can also kill the microbes that break down the sewage. The microbes will come back when the copper sulfate level goes down enough. This can cause problems too. Ziggy

I was told by my county extension office that I could put a raised bed on top of my leach field soI did. My plants grew with no problem other then lack of watering on my part.

Beca, thanks for posting. I believe you need a more specialized forum to consult with regards to your garden. Xeriscaping seems to be far more suitable for your area. You need to find plants that do not require as much watering and obviously plants that can withstand very cold nights and very hot days. A little design tip of mine. I take a photo of the garden in question and I take it from the angle you see it the most. Like from your door or your window. Then I blow up this photo in a black and white photocopier. And then I start drawing directly on them. So for the area you need to block off from view, take a pencil and draw on paper blocks, squares, rectangles, columns, rounds and basically move them about on the photo until you are satisfied with the positions. These figures represent plants. Columns can be a trellis, post, vine, tree, rounds, squares, rectangles are hedges, grasses, etc.. and for the moment, forget about flowers. When you do figure out how to position the plants, it's time to go to your local nurseries to consult on suitable plants. Keep in mind, avoid trees because this is a septic tank area and roots can do a large amount of damage to pipes and tanks. Also keep in mind that in Arizona -- as I believe, you need plants that do not require watering - so this must be either cacti, agave, echeverias and other similar plants that get it's moisture from morning dew or mists. I do hope these are helpful tips for you.

I'm still not clear on the concept of the hay. I understand what you're saying about it being used as a filter but a couple of questions come to mind. First, even if the hay is standard operating procedure for your area the leach bed must be back filled. In that case, the hay will eventually rot and you'll be left with a sunken place all along your leach bed which will require more fill dirt to take care of the settling. I'm guessing your permitting agency has a minimum requirement for the distance from the top of the gravel to the surface. In other words, if it's 3 feet, for example, it's my opinion the 3 feet should be nothing but back fill. And that brings up another point....using the hay seems totally useless to me since the only purpose it could possibly be providing is acting as a filter and had your bed been back filled to begin with you wouldn't need the hay. The dirt on top of the gravel shouldn't cause a problem even if it did eventually seep to some degree into the gravel. Think of it this way: your entire leach bed is surrounded by dirt (so adding dirt to the top doesn't do harm with seepage of dirt into the gravel) and if the depth of gravel meets code requirements and if the distance between the top of the gravel and the top of the back fill meets code then you should be good to go. It sounds to me as if the contractor who installed the leach bed used the hay as nothing more than a quick and cheap way to cover the gravel to buy time until either you or the permitting agency figured out something wasn't right. I still think you need to get in touch with the permitting agency and have them check the system to see if it is up to standards. As it is now, with no back fill, your leach bed with surface water draining into it will quickly become nothing more than a huge ditch with both ends closed and that's not what you want for you septic system.