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Layout for an Accessory Dwelling Unit Septic System | San Diego County

Septic System for an Accessory Dwelling Unit

Hey, Brian Freeman, Freeman’s Construction. Hey, I’m out here on a property in Escondido. We are helping a homeowner here that wants to get an ADU on their property. They already got a primary dwelling. It has a septic system in. They have probably three quarters of an acre, so it’s a smaller lot and it’s very, very tight as far as being able to fit the septic in for the primary dwelling that’s already here, plus the eight new required leach fields for the accessory dwelling unit. We’ve been working through a process number of steps here to actually do a leach line locate on their existing septic system and then working with a septic engineer in order to get to get a system designed. And then we’re working with them to figure out the actual footprint of the home, the ADU that can actually be built here. So, I wanted to walk you on the property here. Walk you through on the property to give you an idea of what we’re looking at. So, I’ll take you through now. 

Building an ADU with Leach Fields

All right, we’re here on the driveway. You can see the slope going down. And this is actually the only spot on this lot that we can get an ADU in here and it’s probably gonna have to be on a stem wall foundation subfloor in order to make this fit. So, we have about a 30 foot wide area that we can actually fit it in, in order to have enough area for our leach field. So, this particular area does not allow a seepage pit ’cause the perc rate is not good enough and we have some issues with the groundwater in the area. So, we weren’t able to condense that area. And we don’t wanna install an advanced treatment system just ’cause of the cost. So, we’re working around that and then we’re showing the reserve area as an advanced treatment system.

Where to Place the Accessory Dwelling Unit?

I’m gonna walk you down here. You can see the road out here. We have a front yard setback 60 feet from the center line to that road, so that really limits the space that we actually have here. If you turn around, we have to be well into those plants over there before we can actually start building, just because of the front yard building setback. And then that tree is our limit as far as where we can build to that ADU, and we have to state if they get a garage in here, so it’ll probably come 10 feet off this wall or that driveway, and then put the garage and then it’ll sit back otherwise see if you have room to turn around.

Marking the Leach Lines 

So, if we walk down here you can actually see where the excavator here, these leach lines were a little deeper than a water pro could get to, so the excavator used, just did a little pawing around here and found the end of these lines just to make sure there’s no more leach lines in this end. And these are the markers of how our septic contractor marked the end of the leach lines. And you can see that they’re 10 feet apart. And there’s three rows of leach lines right here. And they just follow the contour of the land and they run over here.

Leach Fields for an Accessory Dwelling Unit (ADU) 

We were able to get a general idea of where these were at by checking with the County of San Diego and getting an as-built from the prior septic contractor that was drawn up. And then we went out with a water pro and we were able to locate these. So, we’re gonna try to save as much of this as we can and then we’re gonna have to add on to these. And you can just follow these as they go and they keep- all over this direction. Now this area down below, we’re gonna actually, this’ll be what we use to install all the new leach field that is required. And then the leach field that we actually have to remove in order to fit this house in here, the new ADU. So, we are able to go into that building setback which allows us to get closer to the road. So these leach lines at 10 feet apart is typical insulation. You can see how they hug that bank up there as well.

Advanced Treatment System for an ADU 

Now, I’m gonna take you up top and I’m gonna show you an area where we’re gonna put an advanced treatment reserve area and that’s gonna be done with an advanced treatment system. All right, so we’re up here on the driveway now, up near the house. And you can see, this is the mini-excavator we used to actually locate some of those deeper leach lines that we couldn’t get to with the water pro. And this area that’s nice and flat on the side of the house here, this is gonna be used, we’re gonna show this on our septic layout that we’re gonna send to the county. We’re gonna show this as our reserve area. And it’s gonna be done with an alternative septic system. An advanced treatment system. Those are actually only about six inches deep, so nothing will be done here unless the primary system was to fail.

Building an ADU on Small Areas of Land 

So, now we’re gonna walk back down here to see the lay of the land again. That home is gonna sit on the side here, right along that driveway. That accessory dwelling unit. So, that’s really about it. So, I hope that was helpful and you can get an idea of partially what’s required. Each lot’s a little different as far as getting an ADU septic in and making sure it’s feasible. But that’s definitely the first thing you wanna do before you start designing plans. You gotta make sure that it’ll fit, especially from a really small lot, half acre, three quarters of an acre. A big concern. You also gotta make sure that you’re 100 feet away from a well. So, all right. Thanks for listening and we’ll talk to you again soon.

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