Building Homes or Extensions/Residential construction adjacent to stormwater channel
Sorry for disturbing again.
My previous query:
I have constructed home Adjacent to stormwater channel(around 3 feet distance).The dimenstions of channel is 7 feet wide, 6 feet depth. Build up area of house is 1100 sqft, RCC roofed column design.There are two floors (Ground floor and first floor).
My fear is that whether leakage of the waste water flowing in channel (especially in rainy season) into column footings of building or leakage into foundation of building will affect seriously. Will my home collapse?
There are 12 Columns with footings of 5 feet depth (4 feet x 4 feet) each. Kindly suggest any precautions or corrections if it affects the building.Please find the attached my residential plan
ANSWER: Hi Rama, you didn't mention whether the drainage channel was concrete or some other impervious surface but I am going to assume that it is. As long as your column pads were placed on solid compacted earth or a rock bed you should be okay. Most footings can hold up to ground water as long as the ground water is static. The drainage ditch will help keep the ground water static if it is concrete and mostly contained. A series of sheet pilings installed around the perimeter of the house may act as a deterrent to horizontally moving ground water but it can be expensive. Also a french drain around the perimeter accompanied by a sump pump could help keep ground water levels to a minimum, however monsoon rains could overpower such a system after a while and it would probably reach a point where it couldn't keep up with the amount of water dumped by a torrential downpour lasting several days. Sand bags placed around your structure will help keep the rushing canal water contained if it over tops the bank or for a more permanent form of rip rap can be bags of concrete /cement stacked in an overlapping bond with rebar rods driven through them and then wetted down to activate the cement inside. If this proposed method is utilized you can put erosion fabric down first and then the rip rap. I'm not sure how much elevation you have to your first floor or how available any of the products I have mentioned are. Feel free to write again regarding this or other matters, sincerely Bruce Johnson
MY NEXT QUESTION:
I am not able to upload my .jpg file.The bottom of the channel was built with 5 inch thick concrete bed. And side walls were built with size stones of 6 feet depth. There is no special sturcture surrounding the house like sheet piles or sand bags etc as you mentioned. Ony there are 12 columns with 9 inch thick footings each. Area of each footings ~16 sqft. The distance between channel side wall and adjacent columns is ~2 feet. The structure or elevation of first floor is similar to ground floor.
Please let me know whether the channel structure is suffice to protect the column footings.
Hi again Rama, as I mentioned before I am not privy to your soil conditions, how the column pads were prepared before they were poured, what grade concrete and reinforcement was used in the pads, what kind of engineering went into the project and a host of other pertinent information. A geotechnical /hydrologic expert familiar with your area may be able to determine how much movement you can expect from moving ground water during intense storms. I cannot. If your columns and the rest of the structure is engineered properly to withstand lateral forces then I don't foresee your structure collapsing, however it is possible that it may shift or settle if your soil is unstable or if you have moving groundwater undermining your footings. Personally I would have probably have built a house this close to your location on pilings driven deep enough to bear on solid rock. Hindsight is always 20/20 however and I know this doesn't do much to alleviate your anxiety but surely somebody took into consideration your conditions before designing this structure for this location. Aren't there any building authorities to monitor construction practices where you live? Sincerely Bruce