Benching

There  are two type of benching ,simple and multiple.The type of soil determines the horizontal to vertical ratio of the benched side.As a generlal rule the bottom  vertical heightr.. of the trench must not exceed
 4 feet for the first trench.Subsequent benches may be up to a maximum of 5 feet vertical in type.A soil and 4 feet in type  b soil to a total trench depth of 20 feet .All subsequent benches must be below the maximum allowable slope for that soil type .For type B soil the trench excavation is permitted in cohesive siol.                                                                                                                                                e