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Julie2Oregon
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# Posted: 17 Aug 2016 18:20 - Edited by: Julie2Oregon
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I'm math and geometry challenged and have read descriptions of calculating linear feet but it doesn't sink in. Help!
So, On Site emailed me copies of the site eval. application and the approval for standard septic. Says to use a 1,000 gallon septic tank and a 225 LINEAR FOOT drainage area (or whatever you call it) plus have another area ready to go if that drainage area should fail for some reason.
I'm having trouble figuring out what 550 linear feet amounts to, landwise. My parcel is 200 X 150. My cabin will be about 600 sq. ft. Setbacks are 25 ft. from the front and the back prop. lines and 10 ft. from each side.
If I basically put the cabin toward the front of the property and in the middle, the well on one side of the cabin and then the septic tank, trenches, and drain fields (one working and then the same size area set aside) on the other side of the cabin, would I have enough room on that size of a parcel? It's basically 3/4 of an acre.
What would y'all suggest, and what is "linear feet?" Am I thinking in "square feet" and making this too complicated?
***Addendum: I was looking over the previous owners application and approval again and noticed something that may be very pertinent. The size of their septic was based on a 3-bedroom, 2000 sq. ft. home.
So, would my required drain field areas possibly be smaller since I'll be doing a one-bedroom, 600 sq. ft. place?
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Nirky
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# Posted: 17 Aug 2016 20:33
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Linear means line. They are saying you need X number of drainfield feet in total coming off the septic tank. I think the drainfield is sized to the tank and not the size of your cabin.
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bldginsp
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# Posted: 17 Aug 2016 20:48
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Julie- I don't know exactly what 225 linear feet means, and before I speculate I suggest you march into the local health dept. and ask them how they calculate drainfield size. It's done differently by different jurisdictions, in the county where I am they have a booklet that explains it all.
I suspect the 225 linear feet refers to the amount of pipe in gravel they want in your drainfield. But I don't know, and if that is the case, you still don't know how much gravel they want around each section of pipe.
Gravel can be expensive depending on how far you are from a gravel pit, but an alternative to pipe and gravel is the chambers, big U shaped plastic gadgets that you put underground and give the water somewhere to go. I used these, cheaper than gravel and pipe, and they required a different calculation to determine how many to use.
Locating the septic on a small lot can be difficult. Your well has to be 100 ft away from the septic tank and drainfield, on a small lot that doesn't leave you many choices. Also, if your neighbor has a septic close to your property line, your well must be 100 ft from that. The replacement field area is for WHEN the drainfield fails, not IF, but probably not in your lifetime. It's just an unused area, but after the inspectors are gone you could put a garden shed over there.
Generally septic drainfield size is a function of number of bedrooms and the perc test. Slower perc, larger drainfield, faster perc, smaller drainfield, more bedrooms, bigger drainfield, fewer bedrooms less drainfield. But what is a bedroom? "Oh, that's just an office" won't fly. Any room where there could be an expectation of privacy will be considered a bedroom. How many bedrooms will THEY construe that your cabin has?
A 1000 gallon tank is the smallest size and is good for up to I think 3 bedrooms. But you might consider getting a 1250 or 1500 gallon. You are going to have to have the tank pumped when it is half full of "solids". Pumping is expensive. The larger your tank the less frequently you have to have it pumped. UNLESS they require that the tank be pumped every two years, in which case the larger tank doesn't save you pumping fees. But larger tanks are very close in cost to smaller tanks, and a larger tank will better guarantee that your drainfield lasts a long time.
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bldginsp
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# Posted: 17 Aug 2016 20:59
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Quoting: Nirky I think the drainfield is sized to the tank and not the size of your cabin.
Maybe in some places Nirky but in my experience it's done by how many people will live in the cabin. Since that's impossible to tell, they do it by number of bedrooms. Not an accurate way to do it but it's the best they have come up with for predicting the unpredictable. Problem is- what is a bedroom? Where I am a 100 square foot attic is considered a bedroom, a 200 sq ft attic is 2 bedrooms, and a family room with a door to close it off and a closet is considered a bedroom. So, a three bedroom house can quickly become a 6 bedroom house, requiring a YUGE drainfield. Sometimes people design their house with a family room without a door and closet, but then after the inspectors are gone, a door and armoire magically appear. Not that I'm advocating that, of course.......
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Julie2Oregon
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# Posted: 17 Aug 2016 23:03
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I wish I knew how to cut and paste from the PDF to here, grrrr.
Anyhoo, the previous owners stated they would be building a 3-bedroom home on their application and the Oregon formula assumes 2 people per bedroom and each person using 75 gallons per water per day. I read that in some state document.
Which makes sense because the septic approval uses those numbers to calculate the max number of gallons of daily flow, which they stated was 450. (6 people X 75 gallons)
Here's the part I don't understand. It then states 75 linear feet of drainfield line per 150 gallons of flow equals 225 linear feet. OK, I understand the math but how do they come up with the 75?
Bldginsp, this county doesn't seem nutty about seeing potential bedrooms in every corner so I'm not concerned about them trying to add any to my cabin where none exists. Using that formula, I'll have one bedroom=2 people using their 75 gallons per day for a flow of 150 gallons. So, I guess that would mean I'd need 75 linear feet of drainfield line? 
Thanks for the lines and pipe image, Nirky! I can visualize that! 
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bldginsp
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# Posted: 17 Aug 2016 23:46
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The 75 feet per 150 gallons probably comes from a chart that is based on the perc rate of the soil. See if you can talk to the inspector that will be inspecting on your permit. Ask if they will make a courtesy call out to the site to meet you and discuss. He might see things you are unaware of.
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Julie2Oregon
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# Posted: 18 Aug 2016 00:10
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There's a high water table in this area, bldginsp. Might it have something to do with that? Not flood zone high but great well high, lol.
I want to tread lightly and open as few cans of worms as possible. I'm just SO glad it got standard septic approval.
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DaveBell
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# Posted: 18 Aug 2016 01:58 - Edited by: DaveBell
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Linear 225 ft.
= one line 225 ft long
= two lines 113 ft long
= three lines 75 ft long
= four lines 57 feet long
= five lines 45 feet long
= six lines 38 feet long
etc.
Drain field size based on 1 ft wide trench and 6ft spacing between trenches
113 x (2+6)
75 x (3+12) =
57 x (4+18) =
45 x (5+24) = 45 wide x 120 long
38 x (6+30) = 38 wide x 36 long
My code states 4 bedrooms or less, 1000 gal tank.
Absolutely ridiculous for a one bedroom cabin. 
My code allows for a privy (outhouse).
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Steve_S
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# Posted: 18 Aug 2016 08:50
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Julie I have to completely echo what BldgInsp says... This is one of those tricky & potentially seriously nasty areas in home building that you can't mess about with. Every area, region, county is a bit different and you want to ensure your local health dept or whatever it is administering the rules is happy... When they are unhappy, they can make you miserable.
Having said that, it may be possible to get a review / update as your sizing is quite smaller and therefore you don't need such a big system.
One thing to really be certain on... I almost got caught... Distance of septic field & related from well head. Where I am in my region, it is 50 feet. Another property I looked at, the requirement was 75 feet due to soil type & conditions. That info should be readily available from the same folks. PS: I would add extra distance if possible, better safe than sorry and having faith in some shmuck sitting at a desk, I refer to err on caution.
I have to add... why I say shmuck @ desk. I know of a Civil Engineer & Inspector in a Major US City who is responsible for city infrastructure (bridges & the like)... He has all the training & papers so understands the theory, all good and fine. The guy is incapable of finding a stud in a wall or hang a picture on the wall. When he decided to renovate his home, part of it collapsed because he didn't think it needed support when you pull out a load bearing wall. Within the last 3 years, they had 2 civil failure in that city... no one died but he is still doing "his job". I won't say what city but the State is Colorado and NO booze or puffy, he is a Temperance Guy.
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toyota_mdt_tech
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# Posted: 18 Aug 2016 08:55
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Julie, also, remove a door from a bedroom and it can be a study, den etc. I mean just pull the hinge pins.
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Jabberwocky
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# Posted: 18 Aug 2016 09:08 - Edited by: Jabberwocky
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Julie, we just our perk test done about three weeks ago on our property. This is in Oklahoma. We need 300 linear feet. My septic installer has already been selected, but he will be one of the last contractors hired because we don't want other heavy equipment driving over the top of our newly installed septic system - something you may want to keep in mind if you are building something.
Anywho, I'm just reiterating what DaveBell and Bldginsp have presented... Septic tank size is based on number of bedrooms, HOWEVER, in my area and also probably in most others, 1000 gallons is minimum. My thought is, the system really isn't that expensive, at least around here, so unless you are on an absolute shoe-string budget, why not just go for a tank that is all but guaranteed to A) service your home adequately, and B) keep the jurisdiction happy?
Also, lateral drain lines is indeed what your "linear feet" is referring to. This is determined, or SHOULD be determined, by an actual perk test on site, not by some "standard" formula. You probably want to make sure a proper perk test was performed on your property.
Typically, at least for my area, lines are not run more than 100 ft in length, so in my case, we will require 3 lines of 100 ft each. I would imagine you would be getting 3 lines as well in accordance with the math DaveBell provided above.
One more thing: You may have SOME determination on where the lines are buried, but again, this is really based on the perk test. The perk tester normally asks you where the building will be erected, and decides the best spot for the tank/lines based on that information. If you decide to move it somewhere else, the perk test may be invalid because the soil was tested elsewhere. Of course we are talking possibly a few hundred feet difference is all and not likely to alter the results that much, but for my own peace of mind, I would personally want to know that the testing field and the final location were one and the same.
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bldginsp
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# Posted: 18 Aug 2016 09:24
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Quoting: Jabberwocky Also, lateral drain lines is indeed what your "linear feet" is referring to. This is determined, or SHOULD be determined, by an actual perk test on site, not by some "standard" formula. You probably want to make sure a proper perk test was performed on your property.
The number of linear feet of drain line is determined by a standard formula that uses two factors- perc test and number of bedrooms.
For instance- let's say the soil percs at 45 minutes, which means it takes water 45 minutes to drop one inch in the soil when the soil is saturated. The standard formula adopted by that jurisdiction is, let's say, 75 feet of drain line per bedroom at a perc rate of 45 minutes. One bedroom cabin, 75 feet of drain line.
But the lot down the street percs at 35 minutes. The formula states that for 35 minute perc you only need 55 feet of drain. One bedroom cabin, 55 ft, two bedroom, 110 ft. etc.
The formula they use varies depending on the jurisdiction. They will supply you with the chart or calculation they use.
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bldginsp
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# Posted: 18 Aug 2016 09:33
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A lot of people think that the requirements for septic systems is excessive, and they do require larger systems now than they used to. But the last thing you want is a failing system down the road. All drain fields eventually fail- the soil gets clogged up an can no longer drain water. A larger system will take longer to fail.
I put in a 5 bedroom system and 1500 gal. tank for a one bedroom cabin. This is so I can build a house later, or advertise the property as being ready to build a house. But it didn't cost a lot more to put in a larger system, now I know that 30 years from now the system will still be fine.
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Jabberwocky
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# Posted: 18 Aug 2016 09:34 - Edited by: Jabberwocky
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bldginsp
Right, but my point being that without an actual perk test, an accurate formula cannot be obtained. It's like an algebra question with a crucial missing piece.
I probably misread something, but I thought I saw mention of a standard formula and no perk test... or a perk test for the previous land owners? Maybe that was it.
Good point about going larger and forward thinking about future expansion. Our project will be more of a house than cabin. We will have two bedrooms and two baths, with only two people, but the system will be designed for 4 people, which, again, is minimum for this area iirc. This will run us around $3200.00, which, imo, isn't bad considering the overall cost of construction.
As a side point, it is suggested as proper preventative maintenance to pump the tank every 3-5 years regardless if things are backing up or not. Which leads me to my favorite local septic system mottos I've seen painted on their pump trucks: "We're # 1 at taking care of #2!"
"A straight flush beats a full house!"
LOL
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PA_Bound
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# Posted: 18 Aug 2016 09:44
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One additional thought to add... although you are only building a 1BR place, they still may require that you size the septic and drain field for at least 3 BR's. The prevailing attitude is often that someone's 1BR cabin today will be another persons 3-4 BR house tomorrow.
I'm not saying that's right... but that has been my experience.
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sparky30_06
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# Posted: 18 Aug 2016 11:27
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Will they allow you to do an aerobic septic system??
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bldginsp
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# Posted: 18 Aug 2016 14:34 - Edited by: bldginsp
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Quoting: Jabberwocky my point being that without an actual perk test, an accurate formula cannot be obtained. It's like an algebra question with a crucial missing piece.
Right, I figured you knew that but the way you put it could have been misleading to some. I just want to leave people with a complete picture of how it works. Anyway.
And yes, it's a good idea to pump more frequently, but if you wait until it backs up you have just messed up the drainfield. If solids get to the drainfield they begin to clog it up. You can measure the depth of settled solids by opening the tank and sticking a stick in there. Cabins that get infrequent use might go 10 years before getting the tank half full, but a cabin with two people living there constantly could probably fill a 1000 gallon tank to half way in less than two years.
PAbound- good point, which goes to heart of the enforcement situation here, which is that the number of people living in a house is unregulated, just like electrical amperage use is unregulated. With an electrical service you can stick a 200 amp breaker on there to prevent people using too much current and burning up the wiring, but how do you prevent people misusing a septic system? In the past septic system regulation in many places was minimal if not non-existent, and many places are paying for that now with failing systems and all the fun that entails. Yuck. So, the current thought seems to be to get people to build the largest system possible, within reasonable limits.
Honesty might be the best policy, but policy is the worst honesty, and many people are probably forced to do more than they will ever actually use by policies that err on the side of caution. You can say, well, we are better off with bigger systems that will last longer, but size of system is not the only factor that causes the demise of a drainfield. So probably a fair number of oversized drainfields will never use their full capacity, and the extra cost of their installation is wasted. But I suppose that is better, overall, than a lot of undersized systems failing early because they were over-used. But now I sound like a policymaker.....
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bldginsp
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# Posted: 18 Aug 2016 15:32 - Edited by: bldginsp
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Just for grins and giggles, here's a picture of what happens when a septic system fails. The water can't go down, so, it goes up! And brings the gooey biomat with it! (Hurl) Definite proof that **** sometimes flows uphill.
CAUTION- not for the squeamish
Bubblin' up through the lawn.....
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NorthRick
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# Posted: 18 Aug 2016 17:52
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Quoting: Jabberwocky Which leads me to my favorite local septic system mottos I've seen painted on their pump trucks: "We're # 1 at taking care of #2!""A straight flush beats a full house!"
We have a local truck with "Turdinator" painted on the side.
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Julie2Oregon
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# Posted: 18 Aug 2016 18:37
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Thanks for the explanations, guys!
As for sizing the system and looking down the road, I think that can be rather location and site-based, especially since, in regard to codes and regulations, septic is only one part of the picture.
For instance, where I'm going, the subdivisions were developed back in the day with seemingly an eye toward vacation cottages even though the zoning is Rural Residential. Today's septic codes didn't exist, obviously, and the individual lots are TINY -- some just 4,000 sq. ft.!
Many people have a couple contiguous lots as their parcel. Mine consists of two parcels just over a third-acre each. But some poor souls do have only an individual lot that's .11 or .12 acres -- they can't do anything with them now except camp on them in the summer, I guess, so they're empty.
In my search for land, I saw one of these lots listed and it had shared well and septic agreements with another smallish lot next door. These lots used to have cottages on them but they're gone now. I guess that's the way it was done, back in the day -- a well and septic system for a couple of lots with expenses shared. But that doesn't fly now and these little lots aren't big enough to sustain their own septic systems on their own.
But, septic aside, in a resort area like this one in which most folks have buildable parcels about 3/4 or an acre in size, when you add in all of the other regs regarding property line setbacks and easements, distances from the well to other things, AND the septic requirements, there's no way you can build a big, honking house or consider whether future owners will want to add on to yours (which I wouldn't do, anyway.) Not to say that some people haven't bought several lots totaling over an acre and built large and beautiful but many haven't. People tend to do what they want initially with what's there and what's possible, I think, in an area like this one.
To cover every amount of green space one legally can with building would be pointless and anathema to the types of people who live and are going to the places at which most of us are building our cabins. So sizing the septic system according to future owners' desires wouldn't make sense for me.
It seems like the formulas build in an ample cushion. I know I don't use 75 gallons of water, and there's only one of me, as well, for that bedroom, not two people. So building a septic system for a 2-bedroom place would be way more than generous.
I can definitely see the advantages of putting in a 1250-gallon septic tank, though.
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bldginsp
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# Posted: 18 Aug 2016 20:05
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Julie- yes the formulas build in cushion. A two bedroom system will serve you fine.
If you have two adjacent lots, consider combining them into one lot. That eliminates the setbacks down the middle and gives you many more design alternatives. Generally combining lots is lots easier than subdividing (pun intended).
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Julie2Oregon
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# Posted: 19 Aug 2016 00:26
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bldginsp
LOL!
Do you know how that's done, typically? Not sure whom I'd even call. I've noticed on the tax map that some folks have their names on a couple of contiguous lots and others have one large parcel. I've also seen houses straddling contiguous lot boundaries so perhaps it doesn't matter if it's the same owner?
Incidentally, the gent I'm buying the land from is a retired builder/developer who is apparently looking forward to meeting me and helping in any way he can with advice and recommendations. He told the Realtor to tell me he cut up some firewood and he'd leave me some, and he's got an eye on a great clearing for my cabin. I'm getting really stoked. Just a few more weeks!
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bldginsp
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# Posted: 19 Aug 2016 14:30 - Edited by: bldginsp
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Wow! A local retired developer willing to help! Take him to lunch, and order extra beer and BBQ sauce. Bake him pies, wash his car! No seriously, he knows the local ins and outs, and could really help you. Make a long list of questions and a big bowl of guacamole.
Consider hiring him to manage your project, if he's good and willing. He knows Fred with a backhoe, Jim with a dozer, Jeb with a trencher and Buster who's a general handy man to take care of loose ends.
To do any kind of lot line change, start with the planning dept. A good planner should be able to fill you in on the process. And your retired friend can then fill you in on the details that the planner can't, or won't, tell you, like how to get around the rules. Legally, of course. Usually.
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ChuckDynasty
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# Posted: 19 Aug 2016 15:28
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Ask if taxes would be less if you join them.
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Littlecooner
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# Posted: 19 Aug 2016 20:55
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Julie, you have receive some great advice here on this one. It is kind of like the value of land is three factors, location, location and then location. You must address this question with the local authority. There are some generics that apply across the country (lower 48). The 1000 gallon septic tank is somewhat accepted as a minimum. I will not go again over why, as that has been addressed above.
Linear feet is just that, the length of line needed in the old standard of perforated pipe in gravel. Most of this is considered a 24 inch wide trench. You can shorten this by using 36 inch wide trench as it really is a function of the square footage of the trench, ie, if you needed 300 foot of 24 inch trench, then 200 feet of 36 inch trench is the same. Most everyone does not go past 100 feet in length as the standard is to have a cross over between trenches every 100 feet. sounds confusing now? Then we get into the new modern technology of the plastic dome product that does not require gravel ( read - a lot cheaper to install and works far better than the old technology). In my part of the world ( that is why you have to talk to the locals), you can reduce the required linear footage by 40 % by using the new technology product. Then the "number of bed rooms" that is used to calculate the volume of water (effluent ) entering the system, could be your local people will see what you are building ( you may need to furnish house plans) that it is truly a one bed room and not the three bedrooms the other owner was planning on building, which could be on 1/3 the amount of field lines. In some places where I attempted to use the one bed room size for a client, the health department saw thru the "BS" from the owner and said we are sizing for 2 bedrooms. Then I have obtained permits for what you are doing on true one bedroom units. See, it is all about your exact spot on the planet and your house plans and the personality of the permitting health department. You can catch more fly's with sugar that vinegar. O, and on linier footage, in my part of the world, under 25 % slope, the separation of centerline to centerline is 8 feet per run, this changes with slope.
Went a long way to say what your may be looking at for a one bedroom could be some area of roughly 20' wide by 60 foot long. If they let you size for one bed room, could be a lot smaller and we did not even discuss the separation of the washer and kitchen line from the other lines. Have a dedicated place to replace the field lines upon possible failure is a nation wide standard to my knowledge.
Quit worrying and seeking information again, just call the local health department environmentalist and tell him what you plan and ask questions. they will provide the answers and yes, once they do tell you what they require, I am sorry, you will have to do what they say or else stay in Texas. Those are the only two choices here.
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Julie2Oregon
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# Posted: 19 Aug 2016 21:01
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ChuckDynasty
Yeah, that's what I was wondering, too!
Interesting that when I was researching the properties before making an offer and called the county, the clerk told me there was an attached covenant. I thought, "Uh-oh." But it was only that the two properties must be sold together.
As I previously wrote, individually at a third-acre each, the lots wouldn't be worth anything because you couldn't install septic so the covenant actually protects the owner and makes the property more valuable. But I wonder if keeping them as individual lots that can be developed together has tax advantages? I'll have to find out.
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ChuckDynasty
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# Posted: 20 Aug 2016 11:31
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Looked at a banked owned prop recently. Sounds like a similar type of area as yours but in MA. Mostly built in 60's summer homes, many now converted to year round and mainly .24ac lots when built. Cess pool for septic.
MA has a requirement called Title 5. An owner must have septic inspected every two years, three if cleaned every year and it needs to pass inspection. If an owner can't provide a passing title 5 at time of sale the new owner has 6 months to obtain a passing title 5. If they cannot...new septic (no cess pool) needs to be installed. The number of bedrooms dictates septic size. I was told by a health official .25ac lots can't be built on for new construction, period. Many owners buy small adjoining props cheap to increase the area for septic if ever needed.
Health official told me no composting toilets allowed. State of Mass says approved ones are and will reduce the size of the septic area needed as well as an approved grey water system. Black water goes to septic. All need to be engineered design.
I asked this health official for a ballpark cost for septic systems in area and was told 35-150k. The smaller the lot the higher the cost.
A 700 square foot year round cottage without approved title 5 may sell for 30k and the one next door 160k...The one next door has a new modern septic system.
The bank owned props price started at about 25k and sold for under 12k. Sound shape but needed complete renovation. As temped as I was, I passed.
Many small lakes in the area and I would guess a high water table.
Thought this was interesting and a similar type of community as yours.
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Julie2Oregon
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# Posted: 20 Aug 2016 22:10
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Littlecooner
I'm so sorry! Your post didn't show up for me when I responded to ChuckDynasty and I'm only now just seeing it!
I'm not worrying -- just trying to visualize and get an idea of where to put the drain fields on the property and how to draw it on my application for the site plan review for the building department. It just has to be a simple sketch but indicate the number of feet of things and the setbacks, etc.
What pipe would you recommend? Does cold affect how the drain field works? Our frost line is 24 inches.
I know the septic people will design it but I'd like a bit of working knowledge, and I'm going to submit the request for the site plan eval. from here before I move so that by the time I get there, the review will be just days away. The Planning Director said it takes about 2 weeks to get the actual eval done and the building permit once the app is submitted. We're heading into September so my priority is to get the septic and foundation done ASAP!
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bldginsp
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# Posted: 20 Aug 2016 23:09
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One thing that really amazed me about typical septic installations, and approved materials, was the thin wall pipe they use for the drainfield and piping from the septic tank to the drainfield. I forget what the type is, but it's so flimsy you could break it by stepping on it (when above ground). Underground of course it's protected, but if anything messes with it its going to break. You must use 4" diameter for all the drain pipe after the septic tank, I used heavy wall SDR 21 4" and ABS. Better for the long haul, or maybe excessive overkill.
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Julie2Oregon
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# Posted: 21 Aug 2016 02:30
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Thanks for pointing that out, bldginsp. I don't think that's overkill, especially in seismic country. I will ask about it!
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