Septic System - November 2014

The planning for the septic started just after we purchased our land.  It was actually the first project we encountered after purchasing the property.  Every building lot must be approved for a septic system, and although we purchased an "approved building lot" we needed to retest our soil for septic since the testing was done in the 80's when the building lot was established.  Three test pits had to be dug as well as a hole for the percolation test.  The test pits for the soil testing were dug with the Kubota, and we dug the hole for the perc test by hand (these were about 2' deep x 6"wide).  The town sanitarian came out to the site to do the testing, which consisted of a soil evaluation in the three test pits, and the perk test in the deep hole(s).  For the perk test, the sanitarian fills the hole with water, and measures how much the water drops in 30 minutes.  The results of both tests indicate whether or not you can have a septic, and if you need an engineered septic system.  When we got the results, we celebrated because we did NOT need an engineered septic system!

Digging the test pits - March 2012

The next phase of the septic design comes when the site plan is developed.  The site plan includes the layout of the building lot including the house, garage, well, geothermal and septic.  The engineer who did our site plan was able to provide the specifications required for our septic system based on the information we provided from the sanitarian and our house design.  The specifications were indicated on the site plan.     

Site Plan showing septic system in relation to the house.

We had initially planned to hire a contractor to do our septic, however, after looking at the plan, talking with the town, and doing some research, we decided that this was a project that could be done ourselves.

Since we had to learn all about how a septic system works (at least I did), I thought I would share this information as part of the blog for those of you who are interested.  

The septic system consist of two basic parts - the septic tank and the soil absorption areas.    

The septic goes from the wastewater pipe in the house, to the septic tank, then out of the tank to the distribution box and into the drain field.

The septic tank is a watertight box made of either concrete, fiberglass or polyethylene (plastic).  (We purchased a plastic septic tank).  The septic tank treats the wastewater naturally by holding it in the tank long enough for solids and liquids to separate.  The wastewater forms three layers in the tank.  Solids lighter than water (oils, grease) float to the top creating the scum layer.  Solids heavier than water sink to the bottom to form the sludge layer.  This leaves a middle layer of partially clarified wastewater.  A bacteria naturally forms in the layers of scum and sludge which naturally breaks down the solids.  The solids that are not able to break down are eventually removed by pumping the tank.  

The liquid layer flows out of the tank to the distribution box that helps to equally distribute the water into the drain field.  Below is a photo of our septic tank and distribution box:

The most time consuming part of installing the septic system, was the leach field.  Our leach field consists of two sections of double infiltrators.  Each section is 42' long and had to be exactly at the proper height as specified by the engineer.  A traditional leach field is made up of stone and pipe.  The infiltrator systems seem to be the current standard; they have a smaller footprint and are much easier to install.  The infiltrators are plastic chambers open on the bottom, with sidewall louvers that allow the water to drain from both the bottom and sides of the chamber.  

Both trenches needed to be at a specific elevation as determined by the engineer.  This was achieved by using the transit during excavation to get the correct elevations.  The trenches also had to be level and raked out so that the infiltrators could be installed.  A laser level was utilized to ensure that the trenches were level.  

Prepared trench with infiltrators ready to be installed.

The infiltrators were installed in two rows as shown in our design below.  Once the infiltrators were in place, they are covered with stone, followed by fabric, and then backfilled.

Below is a photo of the all the infiltrators in the drain field after installation.  At this point, we were ready for the first inspection, which is done by the local health district, and not the town.  For the first inspection, the drain field, tank, and pipes are inspected.

THE DAY OF INSPECTION

The day of the septic inspection was a torrential downpour.  I was onsite for the inspection, and although everything looked fine initially, we didn't realize until during the inspection that the septic trenches had caved in due to the rain that day, leaving piles of dirt, mud and water covering the edges of all the infiltrators.

Despite the status of the trench, the inspection went relatively well.  A transit was utilized during the inspection to make sure that the system was built at the proper elevation, and that everything was level.  The inspector seemed impressed that the system was within a 1/2" of being perfectly level, and within a few inches of the exact elevation specified.

When the inspector went to check out the tank, he had a bit of a surprise… he stepped on the tank, and then realized that the tank was floating!  The water from the rain storm had drained into the hole, and filled up enough to make the tank float.  Luckily, it didn't seem to be a big deal, and he would just check that the tank was level when he came out for the second part of the inspection.

With the caved in trenches and a floating tank, we had a lot of work to do later that day when the rain died down.  We were also rushed because a snow storm was predicted, which meant that we needed to somehow finish the septic with only one day left of work.  I spent the rest of the afternoon digging out the infiltrators and unburying them the best I could, until it got dark, which was at about 4:30 or so.  When Steve got out of work, he came out and we used the sump pump to pump out the water in the tank hole.  It doesn't look like a lot of water from the photo, but we pumped out a LOT of water!    Luckily, the tank was still perfectly level once the water was drained.  All the hard work paid off because the next day, the infiltrators were ready to be covered with the septic stone.

Half of the trench was able to be covered with stone using the backhoe, however the back half of the trench could not be accessed due to the soft ground.  So, the rest of the stone had to be moved with wheel barrows.  The material was dumped directly into the wheel barrows to make it a little bit easier.

Below is a photo of the back portion of the septic covered with stone.

The final step before backfilling was to cover the system with an approved septic filter fabric.  It's basically a fancy version of landscaping fabric.  The fabric keeps sediment and dirt out of the infiltrators, helping to keep the septic flowing freely.

The inspector was able to come out that day for a final inspection, and gave us the approval so that we could backfill the system.  Steve spent the rest of the afternoon and early evening backfilling, and it was covered before the snow came!  Later, we celebrated this milestone of finishing all the major in-ground work for the house!  The septic was finished two days before Thanksgiving!

Septic system backfilled.