The pits dug for using their materials in the construction of road embankment or canal banks are known as Borrow pits.
When the amount of soil obtained from cutting is not enough to complete the road embankment or canal bank, extra earth is required. This extra earth is collected from the borrow pits.
Borrow pits are dug to get required earth for the construction of road embankment and canal banks.
Borrow pits in Canal
In case of canal banks, Borrow pits may be constructed out of canal section or within the bed of the canal. Outside pits are not preferred because they can become mosquito breeding centres during rainfalls.
Outside borrow pits should not be deeper than 30 cm, and it should be located at least 5 m away, in case of small canals, and 10 m in case of large canals, from the toe of the bank.
The inside borrow pits may be located at the centre of the canal. The width of the borrow pit should be half of the bed width of the canal. The maximum depth of the inside borrow pits should not be more than 1 m. This type of pit is always preferable.
Borrow pits in Road
In the case of road embankment, these pits are dug just outside the permanent land width. Borrow pits should be dug at least 5 m away from the toe of an embankment.
These are dug to a uniform depth which is limited to 1.5 m. These pits should never be made continuous. Ridges not less than 8m in width should be left at an interval not exceeding 300 m.