Liberty Nature Preserve

 

Sewer Water Management

The Septic System

Being located far from city utilities dictates creation of some sort of waste disposal system. Digging a hole in the ground and perching an outhouse above is an option, but not a goal for our project. In fact, before we constructed our 10' X 12' shed for overnight stays, we had no option for bathroom facilities beyond a shovel, a roll of TP, and a hike into the woods. Completion of the shed ushered in significant progress in creature comforts, including a porta-potti.

We call this cozy roost home base at LNP. As a stepping stone to the garage/apartment, it serves the purpose. If you can imagine living like this, you will likely appreciate our excitement when the septic system finally got installed for our garage/apartment project.


Laying out this entire project has been a fine blend of challenge, error, adjust, and reward...all sprinkled with random bits of fun. The septic system followed this format to a "T". Our original plan to place the leach field out in front of the garage/apt (between the structure and the pond) failed miserably when the soils analysis inspector shot us down in flames. It's a long story with a short ending (described in more detail within Design and utility planning; drop down to the "juice, water and waste"section). Suffice to say we suffered the "challenge, error, adjust" portion of our normal engineering process. In the end, with assistance from our septic contractor, we were able to salvage our poor planning by installing a conventional septic system right behind the structure. It isn't an ideal plan, but surely beats the option of pumping to a leach field some 200+ feet away in our meadow area. Moreover, and this is a key point, it is a conventional septic system; no pumps, no extra tanks....the simplest package for waste disposal with no moving parts and minimal maintenance.

Since the date that we received a county approved septic permit, many months passed as we waited for an ideal time to perform the actual installation. Most of this wait was our own doing. We wanted to get all the exterior work completed since the septic installation would tear up the area close to one end of the structure. Since the siding work took much longer than planned, when we finally gave our septic contractor the green light, there was barely 4 months left on the permit before expiration. It's September, we're finally ready, and we have until the end of the year to get the septic system installed and approved. We were assured by our contractor that we were in line with a number of other projects and November/December was likely our time. Well he cut it close, but we snuck in under the wire in mid December.

The master plan...

Mixing dreams with foresight and execution can be a daunting task, but that is exactly where we are. The long range plans for LNP as a DIY retirement home follows this formula, and throws in few more variables....little things like money, mental resolve, and physical stamina. In our lives, this entire LNP project is expected to be the biggest single construction project that we will undertake. We take it very seriously and do our best.

The plan is a series of stepping stones. Building the10 x 12 shed is stone #1. It provides the spartan accommodations and protection we need for long weekends to construct stepping stone #2; the garage-apartment. Upon completion, the gar/apt will serve as our main living quarters, serving as a week-end and vacation get-away. Ultimately, if and when we are actually able to retire, we plan on cashing in our principal residence (our real home) and using the funds to build the final structure at LNP; stepping stone #3....a house. Knowing this, planning for years down the road is important. This planning begins with land allocation; we left a nice spot on the building site. Next is utility electric power, completed by bringing in 400 amps (to split 200 to the gar/apt and 200 to the future home). We have not yet installed our water well, but the plans have been laid and will be addressed in the near future. This leaves waste disposal (septic system), the subject of this LNP chapter.

The garage-apartment is a 2 bedroom, 1-1/2 bath home. Our county health department specifies a 750 gallon tank and a 1200 square foot field. We increase the tank size to 1500 gallons to anticipate the additional load of a 3 bedroom home being added later. We also leave enough room in the field zone to add "fingers" (additional leach field) to meet the increased demand. The tank upgrade from 750 to 1500 gallons is relatively cheap and now is definitely the time to do it. It would be stupid to dig up a smaller tank later. OK, done....but what about the leach field? Why not just go ahead and add the increased capacity right now? The answer is simple; money. Unlike the tank upgrade, installing the leach field is considerable expense and we just plain don't have the funds available. Quite frankly, installing the 1200 sq ft field has already blown the septic budget. We willingly accept the next best plan by leaving the room for more field later and using a distribution box that will allow easy expansion. Here we go.



While we are upstairs bustin' butt to work on the interior framing, our septic contractor is busy plucking out trees at the back edge of our building site.  The area for the septic field will push back a little further than the existing open area, so we have to make some room.  I really hate losing more timber, particularly directly behind the building site, but this is one of those no-brainers that must happen.  Fortunately, most of the trees are smaller and scraggly, so the loss isn't a total heart-breaker.  We tell him to stack them up at the opposite end of the building site in an area that will be suitable for a bonfire; not too close to the garage apartment and not too close to the surrounding forest.  Here is the new footprint.

  The above pic is a good illustration of the slope of the grade.  The main soil pipe is going to exit the structure at the right-rear corner, flow about 50 feet away (follow the shadow line), then turn around and feed into the septic field built into this entire area behind the house.  Yeah, it looks like it's gotta flow uphill.  This simple illusion is exactly what made me blow off this area as a likely candidate for a septic field when we started this project.  It is also the same area that made my contractor roll his eyes and shake his head when I admitted that belief.  Let's follow the magic.



Last weekend, the curtain drain was set (aka; perimeter drain).  I did not get any pics of that process, but the explanation is fairly simple.  A curtain drain is a trench about 4 feet deep with a narrow bucket on the backhoe (I'm not sure if it was the 12" or 24" wide bucket; sorry).  A 4" perforated flexible plastic drainage tile pipe is  set into the bottom of the trench (you've seen the stuff; it's black with corrugated walls and rolled up in a big donut).  The next 2 or 3 feet of the trench is filled with rock and the last foot or so is filled with loose soil.  This trench system surrounds the outside of our proposed septic field.  It follows around in an arc behind the septic tank.  Just past the septic tank, the gravel is eliminated and the trench depth lessens as the plastic drainage pipe continues underground to the edge of the pond and exits at the shoreline.  The curtain drain is a french drain that captures and collects all the rain and melting snow that flows along the ground as it heads downhill toward our the septic field.  We want that septic field to stay as dry as possible to leave room in the soil for effluent fluid dissipation.  The captured excess rain/snow water trickles down to the drainage pipe and follows it to the edge of the pond...simple and effective.



Before we even broke ground for the foundation of the building, we knew that we were going to be dealing with digging the septic system into an uphill slope.  This means that we need to start the flow out of the house as high as possible.  Knowing this, we set the 4" soil pipe hole through the foundation inordinately high (a pic of the foundation just before we poured the interior slab):

This location for a main soil pipe is a far cry from ideal under normal circumstances, but we have no choice on this one.  We will have to make it work.  If things had been a bit more ideal, this exit would have occurred about 18" lower.  Having it at this higher elevation will dictate more creativity at the building exterior, particularly since it happens at an area where there will be a walkway to access the entry door.  I already have some whacky ideas floating across the drawing board that I call my mind.  We will address that later. For now, the goal is creating a sewage disposal system.


Last weekend, the 1500 gallon tank arrived and was set. It's level is directly dictated by the height of our main soil pipe as it exits the garage apartment.  The tank is also kind of high within the grade, but ironically it is supposed to be at this level.  The 3 green cleanout caps are to be level with grade.  I questioned this wisdom since all the septic tanks that I have seen were usually buried under at least a foot of soil and the cleanout had to be dug out when the tank was pumped.  Nope, not this tank...the green domes are green for a reason...to blend in with the surrounding yard.  OK, fine. 

 The entry hole for the tank is visible and ready to receive the main soil pipe that exits the garage apartment.  The tank is filled about 1/2 way with pond water pumped in to keep it stable and the surrounding soil is back-filled. 

The following weekend, he comes back with a crew of 2 more helpers and the real digging begins.  First step is to connect the building with the tank.

A cleanout is set about 1/2 way to the tank. It is a bit too tall for my liking, but we can trim it back and re-set the plug once the surrounding yard is finish graded and seeded for grass. At the rate of our progress on this entire project, this is of absolutely no immediate concern.


The soil covering the exit hole of the tank is removed and the next trench is prepared to set a 4" pipe that will lead to the distribution box.


Next leg of our septic journey routes us to the distribution box.  The distribution box is nothing more than a smaller concrete vault with a separate concrete lid.  The box has a bunch of 4" knock-outs in the walls that will receive 4" diameter pipes.  The knockouts are water-tight until they are, well, knocked out.  Each knock-out has a built in rubber gasket that will seal against the outside diameter of a 4" pipe.  This system will require 1 pipe coming in (from the tank), 4 pipes heading out (to each of the leach field fingers), and 2 more possible future pipes (potential expansion of septic field by adding 2 more field fingers).  A total of 5 holes are knocked open for our immediate needs; 2 of the knock-outs are left intact for future use.


All aboard!....next stop; septic field.

The leach field is a series of trenches that are dug 3 feet wide.  The depth of these trenches are such that they can be filled with a layer of stone (about 12" deep) surrounding the 4" perforated field pipe.  The trench depth is dictated by the continuning slope as it leaves the distribution box.  Everything must head downhill, if even by fractions of an inch.  I our case, since we are digging the field into a hill and putting it lower than a normal system, the downhill trajectory is extremely minimal.  From the point that the soil pipe leaves the house, we are using the lowest amount of downhill slope possible.  Even at this minimal elevation drop, the deepest field finger is still a couple feet below grade. 

The first finger is trenched and the pipe is set.  This finger is the furthest away from the garage apartment.  Since the fingers are spaced about 10 feet apart, and the excavator needs firm ground to work upon, the fingers are excavated, plumbed, and backfilled; one finger at a time. 

The foreground is the pipe leading away from the 1500 gallon tank.  The first right turn is where the first finger begins and runs for another 100 feet.  The two black holes visible on this side of the distribution box are not holes at all.  They are the intact knock-outs for the 5th and 6th fingers that may be installed some years in the future for field expansion.


Here's a couple of shots to illustrate the basics.  After the finger trench is dug, the perforated pipe is laid in at a very specific level to maintain the slightly downhill slope.  Then, a layer of septic gravel (nothing more than 1" river rock) is dumped into the trench to cover and surround the pipe.  Then, a layer of permeable fabric is laid atop the gravel bed to keep the soil cover from infiltrating the stone and clogging up the field that was just created.  The idea is really simple.  The effluent fluid that runs out into this leach field will dribble out of the perforated pipe and fill in the gazzillion tiny gaps between the stones.  This creates a very large holding area for a lot of fluid as it slowly dissipates and absorbs into the surrounding soil.

  


Since all the mechanics of this system rely on a consistent and accurate downhill slope, digging and pipe elevations are very important.  To get this done correctly, 3 major players are utilized:  a laser level strategically located on the site, a laser reader attached to the digging arm of the excavator, and adjustable pipe supports.  Here's the deal...

The laser level sends out a beam in all directions that can be picked up anywhere on the jobsite in the line of sight.  There is a neat little laser receiver that is attached to the digging arm of the backhoe.  It has a strong magnet and is manually adjusted by sticking it to the metal of the backhoe arm.  When this laser receiver raises or lowers to the elevation that is even with the laser level beam, it sounds a loud tone.  The backhoe operator uses this signal to know how deep the bucket is digging, relative to the overall project.  This allows him to keep the trenches at a consistent depth.  The pipe will be adjusted for the downhill slope, and since this slope is extremely minimal, it really never even comes close to the bottom of the trench.  OK, this sets the trench depth....how is the pipe elevation set?


These shots are the fourth and final leach field finger. 

I think you get it.  Those metal pipe supports are adjustable.  Their only purpose is to raise the perforated pipe to the correct elevation to maintain slope.  The slope is measured by using a rod with a laser receiver; 2 guys move along pretty quickly, adjusting each section as it is glued onto the previous pipe section.  When the entire finger (in our case, 100 feet of pipe per finger) is set, the rock is carefully dumped in a little bit at a time by the backhoe's front end loader and worked around the bottom of the pipe with shovels until it is firmly supported by the gravel bed.  Then, the pipe supports are pulled out and the rest of the gravel bed is dumped in to cover the pipe and create the leach field.  Finally, fabric, dirt, and done.


Like clockwork, the county health inspector arrives right at sunset.  Although I'm a bit nervous, I am riding a higher level of confidence.  You see, this same inspector had been out here about a year ago by request of my septic contractor.  He was invited to provide opinion and upfront approval of installing the system that just got completed.  In other words, his visit today is nothing more than sealing the plan that he laid out a year ago.  As expected, we get the green light.  He does spend a few quality moments with me to discuss the unusually high main soil pipe as it leaves the structure.  He admits that he wasn't crazy about this part of the plan, but completely understands and agrees with our reasoning to do it this way.  He offers the suggestion that we will possibly (likely?) have freezing issues with a pipe that is virtually exposed, noting that any trickle like a slowly leaking toilet valve will create a continuously freezing river that will raise in elevation as it freezes over time.  This, in turn, will create a frozen dam inside the pipe; not good.  He wants us to add a heat tape to the bottom exterior of the pipe for about the first 15 feet.  I agree to his request and he hands me the inspection approval document. 



Timing is everything, and our septic contractor plays it very close. The next day, much colder temps set in, as does a bit of snow.  The resulting lumpy mess is of little concern and will be smoothed over in the coming months.  In the meantime, let the poop flow!

 

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