Material Plant Quality Program

The Material Plant Quality Program (MPQP) provides procedures to approve proportioning material plants that produce materials for Caltrans construction projects according to the MPQP Manual and Caltrans specifications.

The following material plants require approval (but are not limited to):

  • HMA batch and continuous
  • Asphalt rubber binder
  • Portland cement concrete batch
  • Precast batch
  • Cement treated base
  • Volumetric mixers (such as for polyester concrete, rapid strength concrete, slurry seal)

All weighing devices (for example, truck scales, weigh bridges, hopper scales) shall be mounted on concrete slabs in accordance with Caltrans specifications.

All safety guards, rails, fire extinguishers, eye wash stations, and other implements shall be in place and functioning in accordance with Caltrans specifications.

Obtaining Plant Certification

MPQP Certification for Active Projects

To request for plant MPQP certification when there is an active project with Caltrans, contact the appropriate Caltrans district weights and measures coordinator (WMC) to inquire about approval requirements for your plant and schedule an appointment at least 2 weeks prior to the requested date. For a detailed process please see “MPQP Certification Procedure” below. Priority will go to those proportioning material plants producing materials for a Caltrans project.

MPQP Pre-qualification Program

The MPQP Pre-qualification Program has been developed to provide contractors the ability to submit their request to certify/recertify their material plants when no active project is defined, or no active project Expense Activity (EA) is available. The objective of this program is to reduce costs and delays for contractors’ future projects with Caltrans that also allows Caltrans to achieve the goal of developing additional project delivery efficiencies as specified in SB 1. For such requests, please refer to “MPQP Certification Procedure” below.

MPQP Certification Procedure

Requests for MPQP certification should be submitted to district WMC. To connect with a WMC in your district, check the WMC contact list. If you are unable to find a WMC in your district, please send an email to Caltrans Headquarters (HQ) MPQP Coordinator at: The general steps to certify material plants are as follows:

  1. Contact an appointed Caltrans WMC in the district where the material plant will be located and request for MPQP certification (Project-specific or Pre-qualification). If you need assistance to find assigned WMCs for your district, send an email to
  2. The WMC will assist with your request (requirements for material plant certification are provided in California MPQP Manual listed in MPQP Resources section.)

  3. A date will be scheduled with a WMC to inspect and potentially certify the material plant. Producers must ensure their plants are ready for inspection and will meet all the requirements.
  4. The WMC will witness the calibration of the proportioning material plant and approve it if deemed compliant with Caltrans requirements. A scale company (Registered Service Agency) is required when calibrating.

California certified traceable masses shall be present with enough mass to prove the scales. The county WMC may be contacted to prove the scales for the county at the same time.

Please note that MPQP certification priority will go to those proportioning material plants producing materials for a Caltrans project with an active project Expense Authority (EA).

Certified Material Plants

The list of all material plants that are currently certified and active in the State are provided as follows.

Note: If you cannot find your certified plant on the list, contact HQ at

MPQP Resources

External Resources

For any additional questions contact the HQ MPQP Coordinator at