6.20     TOPSOIL


The Department's policy for replacement of topsoil is detailed in Section 10A-1 of the Design Manual.


In general, for projects covered by NPDES General Permit No. 2 (effective 10/1/12 to 10/1/17), there should be a minimum of 4 inches of topsoil replacement in all areas not to be covered by concrete, asphalt or gravel.


The areas of stripping, salvaging, and spreading of topsoil should be identified on the plans, special provisions, or right‑of‑way contracts.  These documents should be checked for continuity.  The right‑of‑way contract shall be the controlling document.  The plans will also designate if Contractor-furnished topsoil is anticipated.


Monitoring Topsoil Removal

Acceptable methods of determining topsoil excavation are:

n  Setting stakes at regular intervals at ground elevation as a reference for depth of removal.

n  Removing a scraper width strip at periodic intervals or leaving a narrow strip between scraper paths, thereby obtaining a reference for depth of removal.

n  Grid system elevation checks before and after topsoil removal.

n  Any other method which will result in the assurance that required topsoil is removed within reasonable conformity to the plans and specifications.


Based on a 300 mm (12‑inch) depth of topsoil to be removed and paid for, reasonable conformity will be an average depth over the borrow of 300 mm (12 inches) plus 60 mm (2.4 inches).  If a different depth is specified, it would be that depth plus up to 20% more.


The method of control and adequate field measurements shall be documented in project field books to verify the quantity for payment.  The method of measurement of topsoil removal should be agreed upon at the preconstruction conference.


The specifications state that this item is to be a computed quantity item based on the depth and area involved rather than a measured quantity. On projects where monitoring of the quantity of topsoil removal may be difficult (i.e. urban projects), a plan quantity agreement may be appropriate.


Topsoil on Roadway Cuts and Embankments

Where sand pockets are encountered on backslopes and where sand is used for embankment, every effort is made by the Office of Design to place topsoil on these areas.  Where these situations are overlooked, every effort should be made by the project engineer to obtain topsoil for use as cover for the sand areas.


Cultural Resource Protection

During the topsoil removal phase, or at the start of the excavation operation, you may uncover remains of historical or cultural importance.  This could be bones (human or animal), Indian relics, etc.  If these are found on the project, follow procedures in Construction Manual 6.35.


Payment for Topsoil

As topsoil is removed and stockpiled, the contractor may be paid for one half of the quantity stockpiled.  At the time the topsoil is spread and finish graded, the remaining one half may be paid on a progress estimate.


Consideration should be given to stripping a portion of a borrow at a time to provide erosion control and prevent the stripping of areas which might not be needed.