Thursday, August 9, 2012

Overland Summer drainage

One of the local counties only permits overland summer drainage on road allowances. So what does one do with winter sump pump flows? Well apparently, there are not to be any within the county. So the county is trying to regulate nature? Good Luck county. Now what does one do? Build a glacier in the back yard, where it slopes to county land, so they can get a big melt in the spring, and comply with there overland summer drainage? Oh well, more government waste to tax money.

This is about like the Indiana State legislature in 19th defining the value of pi exactly, for "palatability." Or Pierre  E idiot Trudeau ramming french on western Canada. It just ain't gonna work.

Friday, August 3, 2012

Frost Heave

Frost heave is a process during freezing that causes ice lenses to be formed. Water is drawn to the freezing front. This process required three conditions; a slowly advancing freezing front, a soil that is permeable enough, yet has capillary rise, and a water table within the capillary rise. It is even worse it freezing occurs below the water table. This is all extra to the simple phase change volume increase.

Simple phase change can cause volume changes of 4 percent of the freezing depth; however, 2 percent is more typical. Frost heaves on the other hand can much large, often 150 mms to 300 mms on rural roads, and similar earth structures. Note that the frost penetration is much less in ice lens as the energy loss required to freeze water is greater. Normal soil has no laden heat, and its thermal capacity is only 10 to 15 percent of water, but the soil density is 1.5 to 2.2 time that of water, so a unit volume of soil has typically 15 to 20 percent thermal capacity plus that of contained water. For this reason, frost penetration is greater in dry soil, and typically greater in sand than clay due to the water retention properties of clays.

Silt sized material, with fine sand and small amount of clays is about the worst material for frost heave. This is usually delta sorted material or river settlements. These frequently occur in low land where water is also found. Road fills also reduce the likelihood of frost penetration, which is one thing that can help. Insulation under the pavement structure can also help.

Frost heaves, in the City's, where no frost heave has previously occurred are often indicators of water leaks, as these provide a source of water.  When opening these to expore the cause in clay tills, frequently, a water bearing crevasse infilling sand seam in east Edmonton / Sherwood Park area.  

Thursday, August 2, 2012

Positive Drainage

Drainage away from your house and buildings is critical, and may require maintenance. Backfill against basements, grade beams and frost walls settle, removing drainage. Water will only run down a slope. Yup. A fellow engineer even forgot that. Oh well. The whole building drains to the elevator shaft, and the sump is just below basement floor level over one metre above the elevator shaft elevation.

The ABC building code requires a 150 millimetre vertical separation between any untreated wood and soil. This is essential to prevent rot, mould, from moisture wicking into the wood. In addition the first 1.5 metre away should drop another 150 millimetres. In new construction, we recommend 300 mms in 3 metres to allow for some settlement. Two percent is recommended beyond.

Now what do we do if there is not sufficient grade for drainage? Well, we weight for wet basements and insurance claims. Exterior sumps can be installed, usually to some depth below the weeping tile, and it may have weeping tile attached to pick up any surface ponding. These exterior sumps are high maintenance, as in this country, these pumps need to pulled out in the fall, and reinstalled in the spring, to control freezing conditions. The alternative is heat tape, insulation, and dealing with water in the winter, unless the sump goes dry. Now what about spring, when we have daily cycles of melting and thawing.

The simple solution is to allow enough grade for drainage.

Housing has become a commodity in some areas, rather than a life time investment. Many people have become detached from the care and maintenance of there houses.