Gentlemen, need help with a drainage issue using a LAZER LEVEL. On my personal farm in SW MS, I had a lake constructed 12 years ago. The terrain is gentle to moderate hills and where two ravines merged into one, a large dam was built. It was calculated from the original layout and perimeter elevation survey to be 13 acres when full. Unfortunately, it has never reached full capacity due to not enough drainage uphill and more so due to leakage. To make a very long saga story of why we thought "LAKE LEAKY" has been leaking down to a certain level all these years, we are happy to report we just recently discovered where the leak is and soon she will be fixed!!! (Actually, my nemesis, "Mr. Beaver", showed me the leak and it was not the dam!!!). Assuming it will be successfully fixed and holds water, we have determined how we can capture an additional 42 acres of natural drainage area and re-direct it into the lake on a permanent basis. In doing some GPS elevation checks on the projected water line at full capacity, we found the water level will be approximately 9 ft BELOW the absolute bottom of an adjacent ravine which parallels one of the dammed up ravines. That adjacent ravine drains 42 acres and my plan is to direct that water into the lake by installing a drain pipe THROUGH the ridge and into the lake. The top of the ridge separating the two ravines is approximately 22 ft high and 320 ft wide. Luckily it has gentle slopes on both sides. The pipe trench will be approximately 320 ft long and end up "banana" shaped when completed. I want to put in a min 1/4" drop per ft. Digging the trench is not my problem. I own/operate a JD 160 LC Excavator and a JD 650 H Dozer. The trench will be dug with a 24" bucket. I also own a CST BERGER self leveling Lazer Level with receiver. I don't believe it has the sloping feature. SO FINALLY MY QUESTION: How do you use the Lazer level with such a high hill to dig through? Obviously I cant set up the Level at the bottom of the ravine, as the beam will be hitting the side of the hill. I cant do line of site in the trench due to it only being 24" wide AND banana shaped. Also cant attach the Lazer receiver unit to the digging stick, due to digging depth!! This is where I need experienced help or suggestions. Where do I set up the level? If on top of the hill, do I just determine my bench mark using the receiver on a LONG stick and then as the trench is dug (towards the down slope), calculate the 1/4" drop totals for every 10 or 20 ft and just re-position the receiver unit on the stick accordingly? Sorry this post has been so long winded. But I hope to hear back from some "professionals" with experience in this area. Hopefully someone knows of some neat tricks using the Lazer.
To start, figure out your low point. Once you have that mark it and move your laser uphill another 20 feet of so(or as long as your stick is). Keep doing that until you are close to the top of the ridge. Then start digging, using your last point, shoot the bottom of trench. Once you establish the bottom of the trench, just leave your laser down in the hole. At 20' deep you are going to moving a ton of material. A 160 may be small but you own it, go for it. I would probably bench the whole thing down 8' or so to start. Good luck Cd
If you have a 25' grade rod you may be able to do your preliminary set up in one setting if you can set your laser close to the ground and it is self leveling (on something solid). If it were me, I would shoot the daylight point on each side of the ridge, determine the amount of fall, measure the length of your intended path including the curve, and divide the amount of fall that you have by the length to determine what you slope should be. Example; if you have 9' of fall between the bottom of the ravine and the intended water surface, and your anticipated trench length including the banana curve is 330 feet, you will have 2.73% slope (9/330 =.0273). If your pipe joints are 20' long, then every 20' should fall .545 feet. (20 x .0272727....). You then can start your trench excavation at either end with the laser set up at that level and check each joint of pipe to fall (or rise if you lay your pipe uphill) .545 (roughly 6 and 1/2 inches). With 9 feet of fall in that distance you do not have to be perfect, and when you get close to the end of your trench you will be able to make minor adjustments in the slope to end up where you need to be. 2 points of caution: 1 - dig your trench in a V shape sloping the sides so that the material will not slough in and kill someone, unless you are using a trench box, and at your maximum depth I don't think you have the reach or mass with your machine to handle big trench boxes. 2 - make sure that you do not have any portion of the pipe that does not slope somewhat or you will develope an air lock and you will not get water through it. As Colorado Digger said, you are way light on the machine that you have for this project, so you will probably want to bench down at least 10' in the deepest area. Your dozer may be able to help in this regard if you can take the top of the hill both ways and wide enough to allow room for your excavator and spoil pile. You will be astonished at how much earth you are going to have move in order to do this job. It is do-able, but in order to do it safely you must move a lot of dirt. If you hit rock in the middle of that ridge you have just compunded the problems. I hope it helps! BE CAREFUL GETTING INTO DEEP TRENCHES
OXBOW, thanks again for the reply and all of the technical suggestions. And as I stated to ERIC in the other forum section, under "LAZERS", no one will ever get in the trench. Thanks for your advice and concern. And also as mentioned to him, I have contingency plans when its does "slough" off.
Horizontal directional drill the line. Minimal digging required. 320 ft isn't a lot, however the diameter of the pipe will determine the time needed to complete the job. I've pulled 3- 6" pipes at once, which takes maybe an 18" cutter. It was about 400 feet and took just on day to complete. I don't know what the rates are now, but about 10 years ago it was under a buck a foot.
DM, Although off point from your laser question, here are a couple of thoughts you may have already considered: Since you are fixing the leak, will Lake Leaky need the extra water? Are you planning on controling the water coming in from the new pipe? If not, will the spillway handle a big rainfall once the lake reaches capacity? No need to answer, just a thought.
Couple other things to consider. 9 feet of fall over 320 feet is 2.8%... not really high, but not flat either. In Ontario, the recommendation is anything over 2% should be solid pipe (not perf) (with qualifications). The water velocity can erode the dirt from around the outside of the pipe and cause a collapse. Solid pipe avoids this problem. Tree roots love perf pipe, another reason to use solid wall pipe. Make sure your trench bottom is shaped to support the haunch of the pipe. Flat bottom trenchs cause flattened pipes. Simply use a plate cut in the desired trench bottom profile, welded to your cutting edge or teeth, to make the profile you want. I use a v shaped cutting edge to create a slot for all sized pipes. I know the first instinct will be to grab all the water, but you should at least consider what you are doing to the downstream area of your source ravine. Perhaps taking only a portion of the flow will meet your needs, and leave some for the critters and people downstream. If you redirect all the flow and people notice you may find yourself in hot water. Just a thought. It may not be an issue, for instance if your lake outlets to the same ravine downstream. Am i to understand you are using a flat lazer? I like the sounds of the horizontal bore. If it really is that cheap, it makes a pile of sense. Never seen anything that big done before so i wouldn't know.
This is what I was thinking
THANKS to EVERYONE above who has offered their input and advice! All points well taken. Sorry i stepped away from this thread for a week or so, but I was actually back at the site preparing Lake Leaky for her repair!! Installing and pumping her out with a natural siphon, which is another whole interesting thread I would like to do. I have plenty of pictures!! Concerning ALL of your advice, I was successfully in business for myself (Manufacturing/Wholesale to the Home Center industry) for 30 years and was very fortunate in my businesses early growth years to have had 2 very important older gentlemen in my life who mentored me for years and kept my business (and personal) decision making on the right track. One was my first building landlord, who I guess needed to make sure I could pay him each month!!! And the other was my father-in-law, who just wanted to make sure I was successful so I could provide for his daughter!!! But all joking aside, trust me when I say, I seek out and value experience and advice from those who have been there and done that!! Listening to smart and experienced people like all of you, is exactly why I am very fortunate to have a "Lake Leaky" and the "Big Boy Toys" to play with trying to fix it!! As I said, I was back at the site all last week and in looking it over again, the "benching" of the trench in stages is definitely on the table now. In fact, it will not require that much benching, only on the crown of the hill, due to the gentleness of the uphill sloping. So basically, very little DEEP digging. In answering some of the questions brought up, NO, it wont disrupt or be a problem "robbing" water from someone elses drainage downstream, as it all drains to the same place on my property, even after passing through Lake Leaky. The size pipe will be either 12" or 15". No need for a larger diameter, as our plan is to build a sufficient size dam in the source ravine at the intake so the water can just pool up and then drain out into the lake at whatever pace it wants to. Basically like a water retention pond which is now required in almost all developments here in the south. Thanks again to everyone and we will work safe and smart!! But first priority is making sure Lake Leaky becomes "Lake Tight as a Frogs
Everyone else covered the grade questions very well. On a legal note; you may want to check with your State Water Rights Dept,the Army Corp of Engineers and maybe the Bureau Of Reclaimation, before starting this. You may have to get a 401 permit even if it is all on private land. They moniter activity in certain areas with satellite imagery... I know of a local Indian Tribe that got into trouble this way. I would advise you to use RCP pipe of a suitable diameter on something like this project. Good Luck
Thanks TerraSmooth. I will certainly make sure we stay on the right side of any possible issues. Great website by the way!! I picked up a few pointers I have not thought about before in reading some of the Grading tips. Keep it coming!!!