Hello fellow HEF members, I've heard of although never seen a Sewer Structure where the bench and channel/s are precast into a monolithic base. Here we do it the old-fashioned way with bricks and mortar, same for the chimney, frame and cover atop the corbel/cone. I can certainly see the benefits of it being precast where the concern for invert alignment and elevation is aleviated by the invert boot. Another benefit of cast-in benches and channels is the prevalence of lined/coated structures where if Mason's have to build the B/C's it's an added step to apply the lining/coating on top of the masonry work. My question is, anyone here use these precast structures? Also, I know they precast grade rings to sit atop the corbel/cone but again we still do it the old-fashioned way we're required to have at minimum two (2) courses of brick to a maximum of five (5) to set the frame at final grade. Anyone use these too?
We first used them in the 70's. Some with inverts cast, where you used about a sack of Quickrete to finish the edge around the pipe. At first they were opened bottomed, they were set on cinder blocks, then the base and invert were poured. A few years later they started coming bases poured but no invert. The invert poured ones used a hole with a gasket w/wedge...A PAIN in the drain LOL The others had a u shaped hole, so an exact grade wasn't required for setting. Just put a rubber on the pipe, place the mud, some around the outside on the pipe, then finish the invert.
Hi heavy, In your opinion, are they economical and labor saving in the long run? I know first hand how miserable it can be in the August/September heat of summer with 90+ percent humidity to climb down inside a structure to build the B&C. I have seen those online while researching where the base, walls, B&C are all monolithic and in some cases lined. I'm not sure if it's common industry wide but all our structures are provided with rubber boots cast-in-place that only require two stainless-steel hose clamp type bands. We do however use brick and mud to lock in place the DIP or SDR then seal both inside and out. Since you said the 70's that only further confirms my long-time suspicion that in certain aspects Florida is woefully behind the technological curve. I'm thinking that locating or convincing a local precast yard to form and pour such structures just might be worth it. The time and money saved should - I hope- offset the cost of brick and portland. Considering how many bricks -at 43cents each- get left behind, broken or needlessly discarded not to mention all the 94lb bags of #2 Portland that get wasted or left uncovered -a whole other peeve of mine- you begin to see the cost savings in materials alone.
Precast are all I've ever used for new sanitary. I've done some brick work and rebuilds on older manholes, but everything around here from the 70's on has been all precast. We still use brick on the occasional storm manhole or CB, but only when it's more practical than precast which is rare. The bench and invert aren't actually mono poured though... They pour the floor monolithically with the walls, then core it, most plants put the chunks from the cores in the benches then pour over them forming the invert and benches. IMO it just depends which plant they come from how well the inverts end up working out, but you generally have enough play in the boot to make it work then grout it in. I have used brick, concrete doughnuts, 30" RCP on end, and HDPE Rings to set castings. We also developed a form system which you place inside the chimney section, it expands then your pour concrete around it and set the casting in the wet concrete for a perfect seal and grade/cross slope. For me the main reason to use precast is an exponentially smaller amount of seams which imo is an exponentially smaller chance for infiltration that my kids or grand kids will have to pay to fix.
Huh, Seems we really ARE behing the curve here in South Florida. Of course I never thought of cutting rings out of RCP, better than smashing the bones to bits and having it hauled away. Then again getting the cut good enough for grade purposes relies on he who holds the cut-off saw. We don't use HDPE enough so having scrap around doesn't apply for us. I like the idea of having things all sealed up -the Inspector's like it too- so we religiously use Ram-Nek then mud the seam inside and out. As for the castings, all it takes is an errant blade and off it slides, what I've seen online is the use of precast grade rings where they apply a thin layer of grout then Redhead the frame down permanently, an idea I am fond of for sure. Getting some really valuable input here, keep it coming and thanks...
It's all we use up north too. We only use bricks and mud to seal up around the pipes in and out of the structure where we'd cut or smash a hole in.
Hi stretch, Yeah, like I said, it would appear we're woefully behind the curve with respect to our precast yards. However we don't have to core or smash the invert hole, at least that's done for us with a boot installed to boot. We've got a busy week ahead but I plan on making some calls about having the B&C's cast-in to the base and why our yards don't offer that option. It will be interesting to hear their responses.
all we use is pre-cast manholes. I didn't even think they still build manholes (storm or sanitary) out of brick. As for the cost around here a good roll of thumb is about $150 per foot. The time you guys spend lating brick would be insane. You can build a manhole in less then an hour. Thats base, riesers, cone, and frame.
Hey buckfever, We don't build the entire structure out of brick although I have seen some old one's built that way. No Sir, I'm referring to the Bench & Channel or Invert at the base. Here we build up the bench with bricks then scuplt out the channels or inverts if you will. We also build the chimney out of bricks 2-course min., 5-course max then set the casting on top. I have seen online the "base" structure being monolithic precast including the B&C. WHAT a flippin' labor and dollar saver! I've also seen precast "grade rings" to use in lieu of bricks for the chimney. Having said that, we did get quite a few drainage structures and a boat load of RCP delivered today and I asked one of the drivers about such structures. He informed me that yes, the yard "can do" but has only been asked once prior, by who other than an out of state contractor. Our PM is going to look into the cost and labor savings since we have yet to order the sanitary structures, hey, maybe I'll actually get to see and set one in the near future...
when you use precast manholes generaly do they have pipes comeing out of them like we do or do you always grout your pipes in ? All i have to do is e-mail drawings to the precast place and they bench all of the inverts and install either a bell or a pre beveld piece of pipe for me in all different sises and droop structures
Deeretime, Our precast structures come with rubber boots set at the proper invert elevation. We do however lock the DIP or SDR in place with bricks then mud the opening both inside and out.
Ok I understand what your saying Seamac. I have never seen a sanitary base without a pre-pored invert. Most of the storm bases come without a invert and we either order concrete from a local concrete company. If we do only a couple we get out our mixer and 80 pound bags of gravel mix. On a sanitary base the only thing that needs grouted is around the pipe where it enters the flow line.
Hey buckfever, As a rule we don't do anything to the base of drainage only sanitary and that's where we seem to do it the "hard" way. If the PM get's good numbers then maybe we too will join the 21st Century 'til then nothin' but brick-n-mortar.
Then how do you keep garbage from building up in the bottom? We have installed catch basens with the intent of going back after 4 or 5 are set. after sitting through one or two rains you could already see gravel and road dirt building up in the bottom. Around here no engineer will sign off on your work unless the bottom is poured and the pipe comming in and going out are both grouted.
Don't get me wrong, we absolutely grout the inlet/outlet of drainage structures. When still under construction we regularly change and religiously keep Mirafi paper under the grate. If "crap" starts to build up in the basin we have a Vac Truck to remedy that. All the cities and counties 'round here have Vac Trucks too, it's how they keep 'em clean as well. I've never seen any bench or channel poured into or built in a drainage structure. Again, it would appear that down here we may be a little behind the curve.
Hey Buckfever ever install and mainline for McCandles township Sewar Authority? See you are in the same area I am. They make you pour them by hand, not pre-pours. They have to be smooth as glass, they test it with toliet paper if they run it across the invert and it snags anything, gotta chip it out. The trick I have learned is first thing next morning gotta polish them with around 400 sandpaper. The pre-pours are really nice compared to doing them the other way. A lot less work.
Hey 390eric, Here's a trick we use if the Inspector/s and Spec's approve, we add white plaster mix to our portland #2 cement and do so in a 2:1 ratio. It not only sets and cures faster but you can make a VERY smooth finish easily. Of course it all depends on the Inspector and Spec's, some allow some strictly forbid. Just a thought but then having it precast and ploymer lined affords a finish which is basically slicker than Owl snot, which I've heard is pretty darn slick. Again, just a thought...
Hi, We've used pre-benched manholes with pipe entry gaskets on sanitary sewer applications almost exclusively for over 10 years now. Quicker and easier than pouring a bench especially when dealing with an existing sewer flow. Dominion
Cann't say I have but I do reconise the name. It's funny how some places have crazy specs for some things but look right past some others. Case and point. had a guy from Cecil twp. that made us go in after a structure was built and vac. tested and cut any con-seal that was sticking inside. But they didn't care that the manhole that was installed 2 years ago that we were coring into had a Meannnnnnnnnnnn lean to it. I'm talking a lean that when you looked down to the bottom you had vertigo. Had to make sure you didn't get dizzy and fall into the hole.
O yeah trimming con-seal, always the last part of the mainline inspection, really sucks when you are in a 20 foot manhole hanging on with one hand and trimming with the other.
Hey Eric, I'm curious, what are you calling Con-Seal? Here we use RamNek which is used when we seal risers and cones on top of each other, we do also use a product called Con-Seal but is a coating we apply on top of all mud work, it seals out moisture. To be honest, most of our Inspectors prefer to see the RamNek oozing from the joint just to be sure we put it there in the first place.
the black tar like stuff that sticks to every thing but the concrete in the hot summer sun. We call it con-seal or a few other four letter words when it pulls the hair out of your arm. It comes in a roll that is long enough that you can make it all the way around the outer ring in one pass. Run this stuff on the tongue and ao the groove and you will ripout the lifting lugs before you pull it back appart.
Hey Buckfever, Yep, same stuff different brand name, oh yeah, it can be a b i t c h at times, we get ours in rolled stick form. It generally takes 4 sticks to go around a structure but we do use a Con-Seal product, which we apply over all mud work and all bare concrete on the exterior of a structure. It's funny different regions, different names, but all playing in the same game. Should I ever head outta here I'll have to get the local lingo low down from members. We had a guy from California working with us a while back and when we told him we were off to set the cannons and shoot the pig he looked at us as if we were insane. Now the cannon part I could understand but shooting a pig, c'mon, doesn't everyone run a pig through new pipeline to clean out the crap?
In my area it depends on the municipality. Some will allow pre-cast inverts, some only allow brick and mortar and others only allow concrete. A few of the smaller cities you can use what you want. All sanitary structures are precast, the most common have the rubber boots installed. Some muni's allow up to 2-3 courses of brick to adjust the ring and lid and others will only allow concrete "donuts" to adjust the lid. We always pour our storm drain inverts with concrete. Mud and brick around the pipe and box when you get a few set and depending on how many boxes you have, either pour 6-8 at a time or wait until the pipe is laid and fall back and pour them all. Concrete works good to seal around the bottom of the pipe where it enters the box since it's a pain in the arse to seal it up with brick and mortar. We commonly use square 4'x4' knock-out boxes for up to 30" pipe. Easy to handle and set, just knock out the side you need the pipe to come out of.
Hey CM, I think you're the second member to say you bench and channel a storm drain, I have never once seen that done here. If they get dirty out come the Vac Trucks. Knock-out boxes are another oddity 'round here again, never seen, heard of or set one. All of our structures are precast except the B&C being precast for sanitary and have all holes required from the yard. We do have boots for sanitary though. It certainly makes sense to B&C drainage structures but then all those Vac Truck Driver/Operators would be out of work and you see them all the time on the road. We have one ourselves but we generally use it to excavate and sometimes "rod" a sewer line.
all of our storm drain manholes and inlets must have a channel. usually they are poured but the job we are on now specifies brick channels and if the manhole has more than a 5 foot drop it needs a granite channel . as far as sewer goes we usually have precast channels for the smaller pipe runs up to 15" i belive. do you guys have to tar and tape the outside joints on your sewer structures?
Hey j.r., We don't tar or tape, we use RamNek, mud the seams/joints then coat with Con-Seal.
This is a typical knock out box we use - http://www.foleyproducts.com/v/02_11.pdf#view=Fit The knock outs bust pretty easy with a sledge. After you set your pipe there is a 2-3" gap from the bottom of the pipe to the bottom of the box. This gets poured with concrete, "sweeping" the concrete up to the sides to create an invert and keep any water from standing in the box. The concrete invert also seals the bottom of the pipe/box connection.
Hey CM, That sure looks a lot easier to work with but again, and I'm even embarassed to keep repeating it, here in South Florida we are WOEFULLY behind the technological curve when it comes to our materials. On the bright side our Utility Project Manager appears open to new ideas that can save time and money. At present we have more work than we have manpower or iron and it's imperative that our projects be profitable in anyway possible. I keep emailing him the suggestions and links I receive in here and have been after him to join HEF. Hopefully 2013 will see some changes, hopefully that is. I personally joined HEF with the intent to garner as much info as possible to bid on a CD&R contract which unfortunately got "bought" by a major player in the industry. Then I got tired of chasing my money doing electrical work so. If I am unable to convince others that there IS a better and more profitable way of doing things I just might have to break out on my own once again. To be honest, HEF has been a major contributor to that line of thinking too! Thanks...
We use knock-out boxes on occation but in some twps. they don't allow them. Let the salt eat them for a little while and put alot heavy truck traffic and it won't take long for them to fall appart.
We don't have to worry about salt down South. Most of the applications for the knock out boxes are curb inlets that aren't exposed to traffic.
I wonder if that's because you have so much sandy soil that they're intended to act as a sand trap?
Hey Digger, You know, I never thought of that and have yet to see it "spelled-out" in Spec's or Plan Detail's but that makes perfect sense. We do have our fair share of sand down here, don't we, seems the air is full of it these past two weeks. I just might have to email an old family friend who just happens to be a Civil Engineer, he very well could shed some light and offer clarification on the subject. While on the subject we do wrap our drainage structure bases in Mirafi cloth before setting them, they all have a 12" dia. opening in the bottom. On this new project the City Engineers have us wrapping then bedding the RCP as well, just as if we were installing French Drain. Since we Mirafi wrap the bell & spigot of each stick we are somewhat collectively bewildered by this "new" requirement.
Seamac, now that you said that the structures have a 12" hole in the bottom and your not sealing the RCP when you lay it all makes sense now. What they are doing by not sealing anything up is returning the some water into the ground before it ends up wherever the pipe drains to. In Butler Co. Ohio and probably other places what they are doing now is setting a rectangle precast box with an opening about eight inches wide and the length varies on a bed of gravel just before the catch basin. Next the box is backfilled on the outside with gravel and you fill the opening in the box with pee gravel to the the top. The box is set so the top of it is at the subgrade of the curb and then the curb is poured over top of it with the hole in the precast box formed into the flow line of the curb. After the curb sets up you pull out the forms and the opening of the precast box is now open in the flow line of the curb. You then fill the the void in the curb with porous concrete and some of the water will flow down through the porous concrete into and through the box under the curb through the gravel bed and back into the ground.
On the last storm project I did, the inspector wanted us to bull tar the joints. We were using gaskets and I asked him if we could use fabric in addition to the gaskets but he wanted the joints tarred too.:beatsme He said his concern with using fabric was that the fabric would allow the silty particles of the soil to washout or infiltrate the storm pipe, creating a washout around the pipe. Personally I think he has his head up his arse but what do I know? If you use gaskets on the RCP and bell it up properly, there really isn't any chance of soil migrating into the pipe, much less creating a washout.
Hey Truck, Oh we seal our RCP, first with a well greased gasket then Mirafi wrap the joint for silt intrusion. Our drainage structures unless a control box are always round with that 12" cored hole in the base. When we do bedding it's a minimum of 12" of 57 stone under the structure then at least 6" under the RCP up to the springline. As I said, we also Mirafi wrap the exterior of the structures base before setting.
Hey CM, I have to agree, sounds like your 'Spector has it way up there too, probably dark, smelly and scary. I have uncovered a lot of drainage pipe and have yet to see any washouts, with the ground water and high water table we contend that's a problem we surely would have dealt with before. When we home our RCP we always offset the choker and give the pipe a little spin, before sending'er home. Never had a problem doing it this way and have never had one come "un-homed". You should invite your Inspector to join your crew and help out with the "bulling" I think that would convince him otherwise. We're not Roofers dammit, we lay pipe.
I found it odd not to seal the bells. I thought the wrap was to prevent infiltration since i didn't think you were sealing them. What is the 12" hole in the bottom of the structure for.
I/we have absolutely no idea, they're always there when doing French Drain but this is RCP. It's what was in the Spec's so it's what we ordered, never done it like this before, or completely Mirafi wrapping the entire line. This must be some new hybrid French/RCP drainage system this particular City has devised to mess with our heads and it's working too, what a PITA. I can't recall EVER having to unload so much fabric, should get interesting when we start laying the 60".
The hole has to be to return water to the ground. I felt the same way about those curb inlets I described a few posts back. I had no idea what they were for until the inspector told me what they were for.
I suppose, but this project is literally right next to a huge and deep lake. Pretty much all we're really accomplishing here is balancing. I kid you not, Friday we set two structures and laid about 300' of 18", the last structure -6' tall- was 8' down with water a foot from the top. This is with (2) 10" and (1) 6" hydraulic pumps running at the lowest point of the run. Monday, we anticipate the Trench Crew to arrive wetsuits and us Operators will be wearing waders.
Speeking of water flooding your trench. We did a job once where water that had filled up some old coal mine shafts was now flooding the sanitary sewer. When they installed the sewer they ran a 10" pump all day. Once every thing was done and the builders excavator came in to conect the sewer latteral he would hit water three feet above the tap. So we ran a 18" cpp two feet below the main with T's every 100' to pick-up water. To give you an idea of how much water we where dealing with. We tied into a existing 24" storm line that emptied into a silt pond, by the time we were half way around the pipe was running full bore and the pond was getting hammered. We thought the pond was going to wash out. That was about 5 years ago and that pipe still flows about 2" deep.
Atsa lotta watuh buckfever! I know the GC's Superintedent has been seeking approval from SFWMD (South Florida Water Management District) to lower the lake level by 2'. As of yet that hasn't come through. It should be loads of wet-n-watery fun when we start the sanitary. On Friday our lift-station sub completed their install and the lowest invert is 16' down. I think at this rate we should hire commercial divers.