Leeching field flooding/redirecting flow... 1

[phppounder]

Goodmorning,

Here in the northwest we have been having abnormal amounts of rain (yes, even for us .

My home is situated at the bottom of a small valley, right beside a small lake. Recently we received 2 months worth of rain in about 3 days and my leeching field and drainage system has been overwhelmed with large amounts of water being supplied from the 7 houses situated above me.

This problem has existed in the past, to a smaller degree. My initial solution was to install a sump (3' x 4') between the leeching field and the septic tank. A 1/4 horse sump pump would then channel the water into the perimeter drainage along side the house, which would then eventually reach the common drain.

It has worked successfully for many years. Except this one. I have since upgraded my sump pump to a 7000 gph model, which quickly saturated the drainage along the sides of my home. I have since redirected the flow of the sump pump to give my perimeter drainage a break. Stop gap at best...

I went and spoke with the City's engineering department, and they suggested building a French drain along the perimeter at the highest point of my backyard, and then tying that drain into the common drain.

He did a quicky drawing, which I then transcribed to an even more primitive drawing which can be viewed at:

http://www.islandnet.com/~smartensen/drainage.pdf

Please excuse the "crappyness" of the drawing. I write code for a living ...

Good idea? Any other suggestion.

Thanks in advance,

"Waterlogged in BC"

Stig.

 

[bltseattle]

Intercepting off-site runoff at the perimeter is a great idea for sub-surface flow. A ditch would suffice for surface flow. A French drain may help to draw down the water table which could help your leachfield.

BUT make sure that you understand the downstream condition, especially if your site is somewhat topographically flat. Your drawing shows a ditch that receives water. Is this ditch already full? Is the water level in the ditch backing up your system? If yes, then the perimeter drain might not help you too much, you need to draw down the ditch to lower the water table.

 

[phppounder]

Thanks for the reply Bltseattle,

Luckily the common drainage ditch is never full. It always has good flow, even now. The river of water I have sent its way over the past week has never caused it to overflow.

My lot slopes downward, pretty consistently front to back 2 to 3 degrees. The common drainage ditch slopes down at about the same degree, starting at the end of my property.

The engineer recommended going down about 4 feet, which is the same depth as my sump. Placing a small amount of drainage rock down, then perforated 4" PVC (holes down), and a doing a final burial with drainage rock. Sound about right?

Thanks again.

 

[cvg]

you may want to check out the following threads for some other opinions on how to do a french drain right

thread158-162089
thread158-154653

 

[phppounder]

Thanks cvg.