What is a Precast Concrete Catch Basin?
Catch basins are a critical element in a stormwater drainage system to help catch and direct stormwater to prevent flooding.
A precast concrete catch basin is a straightforward structure, typically round or box-shaped. It typically has an opening in the top covered by a slotted or perforated metal grate. These structures commonly find their place in parking lots or alongside street curbs, efficiently managing rainwater runoff from paved surfaces. These structures are often located in parking lots or along street curbs where rainwater runs off a paved surface.
Catch basins are generally installed as a series of structures, using gravity and downward-sloping gradient to ultimately convey the stormwater to its final destination.
- Specific site use requirements and special constraints
- Stormwater runoff rates based upon storm event recurrence
- Sediment volume, density, and re-suspension
- Anticipated surcharge loading on the structure
- Soil bearing capacity below the structure
Precast Concrete Advantages – For Designers
- Unmatched durability and strength
- High quality concrete mix designs
- Documented QA/QC programs
- Easily customizable to meet project needs
Catch Basin Sizing
Determine proper catch basin size using the anticipated stormwater runoff rate and the required storage volume of water.
The stormwater runoff rate is generally calculated using the Rational Method which can be used for drainage areas of less than 200 acres. The Rational Method calculates the total runoff rate based upon the rainfall intensity, the area of the drainage zone and the coefficient of runoff (i.e. the surface over which the stormwater is flowing).
Once the stormwater runoff rate is determined, the designer can calculate the volume of water which the catch basin must accommodate. Each municipality will have specific regulations on the amount of water that can be passed into the stormwater system. The difference between the regulated amount and the amount entering the catch basin will determine the required capacity and ultimately the overall size.
In addition to calculating the overall size of the catch basin required, the designer must evaluate the size requirements of the inlet and outlet pipes. Again, the size of the required pipe is a function of the volume of water which it must convey.
All of these calculations ultimately determine the overall makeup of the stormwater system that includes the catch basins and the pipes that connect them.
State, City and Municipality Requirements
Each state Department of Transportation, city and even municipality may have different requirements and regulations that govern catch basins.
ASTM C913-21 Standard Specification for Precast Concrete Water and Wastewater Structures
This specification covers the recommended design requirements and manufacturing practices for monolithic or sectional precast concrete water and wastewater structures with the exception of concrete pipe, box culverts, utility structures, septic tanks, grease interceptor tanks, and items included under the scope of Specification C478/C478M.
Glossary of Terms
The rate of rise or fall along the length of the road with respect to the horizontal.
A component at the top of a catch basin that allows storm water to run into the basin while preventing larger debris from falling in.
A component within a catch basin that retains floatable debris, including floatable oil, grease, and petroleum hydrocarbons, at the water surface within the sump of the catch basin.
Casting concrete in a reusable mold or “form” which is then cured in a controlled environment, transported to the construction site and maneuvered into place.
The Rational Method
Calculates the total runoff rate based upon the rainfall intensity, the area of the drainage zone and the coefficient of runoff (i.e. the surface over which the stormwater is flowing).
Soil bearing capacity
The capacity of soil to support the loads that are applied to the ground above.
The result of objects on the surface that add loading to the protective system.