Archaeological Site Mitigation

When Required

If your project will be constructed on or near a significant historic or prehistoric archaeological site, the planning agency (city or county planning department) will likely require that the potential damage to the historic resource be mitigated before construction begins.  Once the mitigation has been completed, they may also require that an archaeologist monitor grading or trenching to insure that significant artifacts and features (not recovered during the mitigation) can be recorded and collected.

Archaeological Research specializes in developing mitigation plans that will allow the project to proceed while preserving the essential nature of the archaeological resource.  We will work closely with your architect and engineer to devise a plan that will protect the resource in the most cost-effective way.

What is Involved

Site Avoidance

Potential damage to archaeological resources can be mitigated in several ways.  The California Environmental Quality Act (CEQA) prefers that significant cultural sites be preserved intact (undisturbed).  This can be accomplished in a couple of ways:

By designing development to incorporate archaeological sites
as part of open space or parklands (deeding such areas to a non-
profit land conservancy group can also provide a nice tax
break).  or

By placing fill soil over the archaeological site and building
atop the fill (the fill must be thick enough to incorporate all
utility, drainage, and footing trenches).  

This is usually the least expensive mitigation alternative and the most frequently used.

Data Recovery

If it is impossible to design the project away from the resource, or if fill placement is not an option (such as in steep slope areas), then CEQA requires that the information contained in the resource be gathered before the damage takes place.

This is called “Data Recovery Mitigation” and involves the archaeological excavation of a sample from the proposed area of disturbance.  The size of the sample depends on the content of the resource.  An archaeological site where only one activity was taking place (such as a quarry site where only stone tool manufacture occurred) may only require a 2% to 3% sample of the area of impact.   A village site where stone tool making, food preparation, housing, and ceremonial activities took place may require an 8% or 10% sample of the area of impact.

Combination Mitigation Plans

Often it is possible to place fill over much of the site, however utility trenches may require that small areas be damaged.  In such cases only those areas where direct damage will take place are sampled.

In the photos at right, 4 homes and 3 duplexes were constructed atop the largest prehistoric village site in Morro Bay.  The top photo shows the placement of fill over the archaeological site.  The lower photo shows the completed project.  Damage to the archaeological site only occurred where water and sewer lines had to connect to existing mains under the street.    In these areas we conducted data recovery excavations before the connection trenches were dug.

Products Produced

Mitigation Plan

Often a planning agency will require a mitigation plan prior to issuing the construction permit.  We will work with your architect and/or engineer to come up with the best mitigation alternative for your project.  We will provide you or your contractor with a PDF file of the Final Mitigation Report (this PDF can be sent to the permitting agency and kept with your permit paperwork).

Final Mitigation Report

Once the archaeological mitigation work is complete and materials have been analyzed, we provide you or your contractor with a PDF file of the Final Mitigation Report (this PDF can be sent to the permitting agency).  In addition, a copy is sent to the California Historical Resource Inventory office so the state files can be updated.

For more information concerning the legal requirements, click the “Services” button above and select the “CEQA Law” item from the drop-down list .