The FHWA has outlined a Laboratory Qualification Program in the Federal-Aid Policy Guide update published as 23 CFR 637 on June 29, 1995. The updated guide has requirements for laboratories performing testing on Federal-Aid highway projects.


In order to avoid an appearance of a conflict of interest, any qualified non-DOT laboratory shall perform only one of the following types of testing on the same project: Verification testing, quality control testing, IA testing, or dispute resolution testing.



The following laboratories are included in the qualification program for all Federal-Aid projects:


Central Materials Laboratory Ready Mix Laboratories

6 District Laboratories PCC Contractor Laboratories

District Area Laboratories HMA Contractor Laboratories

Resident Construction Laboratories* Consultant and Commercial Laboratories *

Aggregate Producer Laboratories City and County Laboratories *

Soils Field Laboratories*

* May be qualified at the time of a project.



A two-level qualification system is required by the FHWA. Laboratories are either accredited or qualified. The accreditation process is more rigorous than the qualification process.


Accredited Laboratory Process

The Central Materials Laboratory and the six District Laboratories will be accredited as outlined in the 23 CFR 637 guide. The Central Materials Laboratory is accredited through the AASHTO Materials Reference Laboratory Program. The District Materials Laboratories will be accredited by using the Central Materials Staff and equipment to check testing and testing procedures and by using the same calibration and training documentation process. Laboratories will be accredited for a two-year period. In addition, an annual review will be made by the Central Office Staff. Appendix A contains the procedures for accrediting the District Materials Laboratories.


Qualified Laboratory Process

The remaining laboratories will be qualified as outlined below:


The District Materials Offices will qualify laboratories. Laboratories will be qualified for a two-year period. In addition, an annual review will be made by District Staff. Appendix B contains the procedures for qualifying materials laboratories.


Four laboratory types will be qualified, aggregate laboratories, PC Concrete laboratories, soils field laboratories, and Hot Mix Asphalt laboratories.


Qualified laboratories will have the following:


1. Current manuals and test methods to perform the qualified testing available


2. A technician certified by the Iowa DOT to perform the qualified testing


3. Proper equipment to perform the qualified testing (calibrated or checked annually according to Appendix B)


4. Satisfactory project and proficiency test results


5. Documentation of equipment calibrations, equipment checks, and proficiency results


The District may elect to accept qualifications, accreditations, or inspections from other government agencies or Laboratory inspection agencies. The AASHTO Materials Reference Laboratory (AMRL) and Cement and Concrete Reference Laboratory are 2 common Laboratory inspection programs. The links are:


Accredited Laboratories for Testing Soil Samples for Contractor Borrow


Laboratories for testing soil samples for contractor borrow shall be accredited for performing the following tests: 

        Atterberg Limits (AASHTO T89 and T90, or ASTM D4318)

        Percent gravel, sand, silt, and clay (AASHTO T88 or ASTM D422)

        Proctor density and optimum moisture (AASHTO T99, ASTM D698)

        Hydrometer particle size analysis of soils (AASHTO T88 or ASTM D422)

The accreditation could be AMRL, A2LA, Army Corp of Engineers, or other acceptable accreditation program.



The Central Materials Laboratory will be responsible for implementation and operation of the Laboratory Qualification Program. The Central Materials Laboratory will accredit the District Laboratories. The District Materials Offices will qualify laboratories.



A laboratory that does not meet the requirements of the IM is subject to elimination from the qualification program.


Disputes concerning calibration and correlation of equipment will be resolved by the office responsible for the qualification. For disputes that cannot be resolved at the District, the Central Materials Laboratory will be the final authority.