rear lot drainage (swales anyone?) 1

[johnhan76]

Picture this: Residential subdivision, houses backed up to one another. The back yard of house #1 drains into the back yard of house #2 and then into the street. I want to put in a swale to catch the water before it goes into yard #2. The developer doesnt want to put this in for the following reasons: 1. says that older neighborhoods dont have this and that they work fine 2. says that the swales will not be maintained. 3. trees will have to be removed, ruining the lot 4. cost

Just wanted to see what everyone else is doing. These are 1/3 acre lots, on a 4% slope, soil type:18" sand above clay.

 

[francesca]

Our local street department has an ordinance that water may not cross two property owners. Your description above, with water originating on one lot, crossing another and then ending in the street would comply and we would not put in the swales.

If, as you say, only the water from lot 1 is draining across lot 2, then, in our area, by the rational method, with a 10-year, 5-minute volume of 7.64 and a runoff coefficient of 0.4, this would be 7.64 x 0.33 x 0.4 = 1.0 cfs and it would sheet flow -- really not a significant amount.

However, you are the designer, not the developer. You have a duty of care to consider cost, but the developer should respect your professional opinion. It's highly unlikely that the developer will know of any problems in older subdivisions without swales as residents will direct their complaints to the street department, not the developer.

Our swales are 5' wide and half a foot deep, with a gentle side slope. It's nonsense that these wouldn't be maintained as they're as easy to mow as the rest of the yard.

It is a valid point about having to remove trees, but rather a small cost now than a lawsuit later.

Check your local drainage ordinance, do some calculations and if you feel the swales are truly warranted, put them in.

 

[LHA]

I would not grade an actual "swale", but definitely create a low "draw". Just a few inches deep and several feet wide, so it could be mowed or landscaped as desired.

1. Swing by and check out those "older neighborhoods" referred to. I'll bet they have this situation.

2. The developer is correct. A deep, steep swale in everyone's backyard will not be maintained, even with an easement. You can put all the O&M notes on the Plans you want. In fact, they are very likely to be filled in and used for something else...like trees.

3. Removing some trees might be necessary to create a draw, but keep all you can. You have to do something, you must provide positive drainage.

4. You job is to balance your client's needs (minimizing costs) while performing due diligence. Costs can't be the only factor, but they certainly are a factor.

5. The 4% slope and 18" of sand are perfect to prevent standing water, but the lots are very small, so you will "ruin the lot" much more by not creating a draw than by cutting some trees down. And with a draw, you can replace the trees. With a swale, you will need an easement, and the agreement will probably say "no landscaping within the easement".

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

 

[ctmtwilliams]

As stated, many counties/cities have regs prohibiting draining into or across adjacencies. Developers crying about cost is no excuse for poor drainage planing.

 

[johnhan76]

I agree, but I want to find a reasonable balance. It is not required here but in some cases I think it is necessary. I think that the "one property" rule francesca spoke of is reasonable although I have a question. Would you need to have recorded easements along the side lots? If not, what keeps the downstream property owner from building a wall to prevent positive drainage?

 

[francesca]

Our planning regulations specify a 5' Public Utility and Drainage Easement along all side lot lines, 10' at the rear and 20' at the front. If your final plats don't include such easements, I recommend that you start to include them because they don't put home owners off, but it makes future utility and drainage problems infinitely easier to resolve.

 

[ctmtwilliams]

I've seen litigation where the property downstream/slope attacked the upstream for damages. I personally wouldn't buy proprety that was graded in such a way, neither up nor down "stream".

 

[francesca]

The law, in Tennessee at least, says that you can't increase flow across a neighboring property -- be it increase in rate, volume or velocity. There's nothing wrong with one property draining across another as long as the amount of water remains constant. It is increadibly common in residential subdivisions for one property to slope onto another. As both lots are platted simultaneously, neither home owner can cry foul play.

ctmtwilliams -- I challenge you to prove that your neighbor's property does not drain across yours in some places, and that all the water falling upon your own property is entirely contained within your own boundary.

 

[ctmtwilliams]

Not uncommon, perhaps not in Tenn. but in many places municipalities do try to avoid this situation. Not being uncommon doesn’t mean it doesn’t cause problems. Additionally, I’ve seen this same issue pop up here before so you can’t say it isn’t problematic. The point is, when you put engineering controls in place that causes water to be directed onto another’s property you open yourself to liability. As johnhan76 asked what if the down stream blocks the drainage? To quote from a song by Warren Zevon who said it best: “send lawyers, guns and money, to get me out of this!” Did you see the land slide on TV in La Conchita? How many people were killed? Litigation is underway claiming the cause of the land slide that was potentially exacerbated by drainage from an up slope adjacency. Ok I admit that’s an extreme example, but one should never take drainage and the potential for litigation lightly.

To respond to your challenge: I suppose you could live at the top of a hill and all of your surface water is captured and directed into a county/city maintained system. But typically, is the amount of water that escapes onto an adjacent property significant enough to cause engineering controls to be put in place? Most times not. In actuality, all but perhaps a very, very minor amount (so little in fact, I don’t know how it could be measured, if at all) of my surface water drains into a county maintained stormwater system. The same holds true for all of my neighbors in my hill side community.

I’m not a civil, but from what I’ve seen with new residential subdivisions (as stated in the original posting) stormwater drainage systems are commonly mandated by planning commissions and designed by engineers to prevent such occurrences. Your grading plan would never get through the Ventura County Grading permit process without engineering controls in place preventing encroachment onto adjacencies by surface drainage. The regulations are so stringent that sand bags are commonly placed around the perimeter of construction sites to prevent off-site migration of uncontrolled surface water.

Now, if you are talking about Bubba subdividing the back 40 in some swampland, all bets are off. But let me tell you, around these parts people don’t take kindly to other people draining onto their land, it causes problems.

 

[francesca]

The point is, when you put engineering controls in place that causes water to be directed onto another’s property you open yourself to liability.

Indeed, as I mentioned, it is illegal to increase the flow of water across a neighbor's property. However, the situation involving one phase of a subdivision, with both upstream and downstream lots platted at the same time, sets the status quo and neither owners is harmed.

Furthermore, around here at least, 1/3 acre is large for a subdivision lot (minimum lot size for R-1 here is 16,000 sq ft, or 1/4 acre). The SCS curve number for 1/3 acre is not much greater than that for open space. The amount of water sheet flowing across a 90'-100' wide grassed lot is only significant enough to reach shallow concentrated flow in a very large storm event, and even then it is unlikely to achieve an erosive velocity unless something channels the water (for instance, an engineering control such as a ditch or a pipe).

The most likely problem with sheet flowing one residential lot across another is if there is not positive drainage on the downstream end, causing ponding. Still, if the lots were platted at the same time, the downstream owner will have no legal recourse.

 

[mitchell54]

Gentlemen,

I just finished helping my father with this exact problem. This is a huge legal issue not doubt. Unfortuneatley while you fight this battle with the developer and city engineers years may pass along with thousands of headaches, man hours, and time (which as we all know time is money). This isn't to mention all of the problems that you may have because of the drainage, landscaping damage ect...(the list can go on).

So my suggestion (although I know it isn't the best idea) is to take matters into your own hands!!!! Do what it takes to fix it then if people bitch about it then fight your leagal battle. (You are in the right to begin with so they really can't do much.....they all know this so 99% of the time they won't say a word about what you have down)

As far ar a quick fix....go with a simple french drain set up...it is quick...easy...cheap...and inconspicuous...

Like I said this may not be the PC way of fixing your problem...but it is sure better that dealing with lawyers, developers, and city engineers.....trust me if you fight the legal battle plan on years before you get results!!!!!

 

[chicopee]

Lha may have the right idea.

 

[RJLDesign]

I honestly can not see how you could go without swales. Your local council will argue that you have increased the discharge. Your second problem is legal point of discharge. You may need a small piped system to drain the water to the street.

The neighbour will have the right to go the the council and complaint about sheet flow onto his property even though it was happening in the existing situation. You cannot design for 50 yrs down the track with a job such as this but you can design to make sure that at least till the block is sold and built on that you have done the right thing.

If the new owner does not maintain the swale unfortunately this is the down stream owners problem.

Austdesign
Civil Designer
QANTEC McWILLIAM consulting engineers
Web:-

http://www.qmcw.com.au

 

[roncity]

In most cases the swales or draws are created when the builder installs the building pad for the slab. Francesca stated on 20 Jun 05 a 5' Public Utility and Drainage Easement along all side lot lines, 10' at the rear and 20' at the front would provide a place for future utilities and draiange. These easments also provide a place to borrow material for the slab and create the draw at the same time.