Grading of Property Next to Slope 1

[dynamics5]

If there are 4 lots arranged 2 X 2 (each lot shares 2 sides with 2 contiguous lot) and one homeowner wants to build a retaining wall around 3 sides of his property (2 sides and the back of the property), then elevate his property by filling it with soil such that it is 2 feet higher than the other 3 properties, is it possible to do so without changing the drainage pattern for the 4 lots? This is because the HOA does not permit changing drainage patterns because the area is a runoff for water as the 4 lots are at the foothill of slopes. If it is possible to retain the same drainage pattern, would it entail installing drains of some kind (French drains?) all around 3 sides of the property?

 

[beej67]

Depends on the topo of the other lots.

Post a topo survey and we can answer your question.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[dynamics5]

Don't have topo! The 4 lots are pretty flat, the one lot is simply around 2 feet higher than the other 3 with the retaining wall and added soil. Question is what, if anything, can be done to preserve original drainage pattern

 

[jgailla]

One way is to provide a diversion swale around the perimeter of the elevated lot in those locations where there is currently sheet flow across the property. Without topographic, it would be hard to say. You should be very careful with this project. If the other lots flood, someone's going to get sued.

 

[beej67]

"Pretty flat" doesn't cut it. If you don't have survey, then you don't know the original drainage pattern, so you don't know what you need to do to preserve it.

If the lot in question is where the other lots drain to, then you can't raise it without changing the drainage pattern. If the lot in question is higher than the other lots, then you can put your wall in without affecting the original drainage pattern at all.

I wouldn't make an engineering recommendation unless I knew what the original drainage pattern was. If it's obvious, you might not need a survey, just a few photos. If it's all so flat that you can't tell by visual inspection, you need to figure it out.

Go to the lot in question and turn on a garden hose for an hour, see where the water goes. Then go to an adjacent lot, turn another garden hose on, and see where that water goes. Wait until a big rainfall and stand out there with an umbrella and see where the water goes. Etc.

In my experience, these things very very often turn into lawsuits. Cross your Ts and dot your Is. They may not want to pay you for a survey, but if not, make sure you have some other way to document your findings.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[dynamics5]

The water now drains to the back of each of the lots, ie. down the middle of the 4 lots that are situated 2x2.

 

[brandonbw]

What does the water drain into down the middle of the 4 lots? Does this middle portion have a drainage easement? How you drain to that depends on what's going on there in regards to swales, easements, etc.

I am thinking if you raise the lot by 2 feet, you can either sheet flow the property from back to front into the street. Which a lot of cities we work with here in SoCal prefer over keeping the original drainage pattern. Or you can catch all the water in the back into a dispersal wall and flow over that wall into the middle of the lots.

Though you can't really do anything without a survey.

B+W Engineering and Design
Los Angeles Civil and Structural Engineering

http://bwengr.com