Unconfined abrasive blasting is essentially abrasive blasting conducted outdoors. Visible emissions from permissible unconfined abrasive blasting are limited to the 40% opacity standard. Additional requirements are in place when preparing surfaces for pavement markings and blasting stucco and concrete.
Unconfined abrasive blasting is permissible if the following conditions are met:
- Steel or iron shot/grit is used exclusively; OR
- The item to be blasted exceeds eight feet in any dimension or is situated at its permanent location. Blasting is to be conducted by any of the following methods:
- Wet abrasive blasting: using compressed air as the propelling force and water to minimize visible emissions.
- Hydro blasting: using high-pressure liquid as the propelling force.
- Vacuum blasting: a vacuum device immediately collects the spent abrasive, surface material, and dust.
- Dry abrasive blasting using abrasives certified by the Air Resources Board
Pertaining to surface preparation for raised traffic delineating markers and pavement marking removal using abrasive blasting. The performance standards are defined in §92510 and require:
- Using wet abrasive blasting, hydro blasting, or vacuum blasting; OR
- Dry abrasive blasting for removing or preparing the surface for immediate application of pavement markings of less than 1,000 square feet or for preparing the surface for raised traffic delineating markers using ARB Certified Abrasives.
Stucco and Concrete
The performance standards are defined in §92520 and requires using wet abrasive blasting, hydro blasting, or vacuum blasting. However, the regulation allows for dry abrasive blasting using ARB Certified Abrasives for:
- Window and door returns and frames
- Eaves, overhangs, and ceilings
- Sweep abrasive blasting of concrete. Sweep abrasive blasting is method of cleanup performed in order to achieve surface uniformity or impurity removal after wet blasting, hydro blasting, or vacuum blasting. This performance standard does not apply to stucco surfaces.
- Completely shrouded structures and blast areas that effectively control emissions. This requirement also applies to concrete swimming pools.
- Abrasive cleaning operations. This does not apply to aggregate exposure or paint removal related to new concrete construction or repair activity.