Representative photo — not the project site.
Stormwater trash capture
Normal Avenue Trash Capture Device
Designs, calculations, plans, specifications and estimates for a trash capture device on an existing Chico storm drain that discharges into Little Chico Creek.
The project
The Normal Avenue Trash Capture Device is a City of Chico project to install a trash capture device on an existing storm drain pipe that discharges into Little Chico Creek, so litter carried by stormwater is trapped before it reaches the creek.
American Engineering prepared the designs, calculations, plans, specifications and estimates for the City of Chico.
Little Chico Creek rises in the northern Sierra Nevada foothills and runs nearly 16 miles south-west through steep canyons to the Sacramento Valley floor. It then flows about 9 more miles, west through Chico and then south-west, into the braided channels of the Sacramento River's eastern floodplain.
A storm drain carries street runoff, and the litter it picks up, straight to the creek it discharges into. California's Trash Provisions target that pathway. Their main tool is the full capture system: a treatment control, or series of them, that traps all particles 5 mm or larger.
Chico chose the compliance track that relies on full capture systems. Its 2018 Implementation Plan proposed 132 drain-inlet devices and 69 outfall or outlet devices over a 12-year timeframe.
Scope
Our scope
American Engineering prepared the design documents for the City's trash capture device. The work, grouped by phase:
Design the installation
- Preparation of designs for the installation of a trash capture device on an existing storm drain pipe that discharges into Little Chico Creek
Run the calculations
- Calculations
Trash capture calculations typically confirm the flow a device must treat and pass. See stormwater calculations.
Prepare plans, specifications and estimates
- Plans
- Specifications
- Estimates
Plans, specifications and estimates (PS&E) are the standard package for public works bidding. See improvement plans.
Technical highlights
How the work fits together
Two illustrative diagrams: where a trash capture device can sit on a storm drain line, and the tests a full capture system must meet.
Where a trash capture device sits
One common retrofit sets a treatment unit into an existing storm drain line, between the inlets that collect street runoff and the outfall. Flow passes through a screen that holds trash back, and a manhole gives crews access to clean it out. Up to the design storm, all flow must be screened. The diagram shows one common arrangement, not this project's design.
One typical arrangement (profile along the pipe)
Illustrative diagram — not to scale
- Runoff washes street litter into a storm drain inlet.
- A trash capture unit set into the existing pipe, drawn as a neutral box because device types vary. Its screen holds trash 5 mm or larger.
- A manhole gives crews access to inspect the unit and remove trapped trash.
- Only flows above the design storm may pass over the screen; below it, all flow is screened.
- Screened flow continues to the outfall and the creek.
What counts as full capture
California's Trash Provisions define a full capture system by two tests. It must trap all particles 5 mm or larger. Its design treatment capacity must either be at least the peak flow from a one-year, one-hour storm on its subdrainage area, calculated with the Rational Method, or be sized to carry at least the same flows as the storm drain it serves. The State Water Board must certify a system before it is installed.
The two tests for a full capture system
Illustrative diagram — not to scale
Trash size
- Trash 5 mm or larger stays on the upstream side of the screen.
- Water passes through the screen and continues downstream.
Design flow
- At least the peak flow from a one-year, one-hour storm on the subdrainage area: Q (cfs) = C (runoff coefficient) × I (rainfall intensity, in/hr) × A (area, acres).
- Or sized and designed to carry at least the same flows as the storm drain it serves.
Engineering considerations on storm drain trash capture retrofits
- Capacity in an existing pipe
A device added to a working storm drain must treat its design flow, or match the pipe's capacity, without adding head loss that backs water up the line.
- Specifying an approved device
Only systems certified by the State Water Board count toward compliance, so specifications are usually written around certified products, and any "or equal" clause must require certification too.
- Maintenance and leaf litter
Crews need room and openings for vacuum-truck cleanout. Chico's Implementation Plan names leaf litter as a known issue in the City, and heavy leaf fall fills screens faster.
- Depth, space and live flow
Storm drains can run deep under crowded streets, so installing a device or structure on an existing line can mean excavation, shoring and keeping the storm drain flowing, for example by bypass pumping.
Rules & permits
Regulatory context
Public records show the statewide rules and City plans behind trash capture in Chico. They describe the public program, not American Engineering's scope.
-
ISWEBE Plan · Trash Provisions
Statewide trash rules
The State Water Board adopted California's Trash Provisions on April 7, 2015, with a matching Ocean Plan amendment. The Office of Administrative Law approved them on December 2, 2015, and U.S. EPA on January 12, 2016. They apply to MS4 (municipal separate storm sewer system), industrial and construction NPDES permittees.
-
Water Code §13383
Chico's compliance track
On June 1, 2017, the State Water Board ordered traditional Small (Phase II) MS4s, including the City of Chico, to choose a compliance track. The City selected Track 1: installing, operating and maintaining full capture systems on all storm drains that capture runoff from priority land uses.
-
Full capture certification
Only certified systems count
Any trash treatment system installed after December 2, 2015 must be certified by the State Water Board's Executive Director before installation. The Board's list of certified systems was updated in August 2026. A custom-designed, project-specific system goes through the same certification process.
-
Chico Trash Master Plan
The City's plan and deadline
Chico's two-part Trash Master Plan, an Implementation Plan and an Operations & Maintenance Plan, is dated September 2018. It sets final compliance at December 2, 2030, and calls for inspecting each full capture system at least twice a year: once before the wet season and once during it.
Chico is a traditional Small (Phase II) MS4 under the statewide General Permit, Order WQ 2013-0001-DWQ. Its trash requirements came through the State Water Board's June 1, 2017 Water Code §13383 Order; the Small MS4 General Permit will implement the Trash Provisions when it is reissued. Requirements reach each agency through its own order or permit, so compliance tracks, device choices and maintenance schedules differ by agency.
Services used on this project
Sources
Public records and agency pages behind the project context above. The scope section describes American Engineering's own work.
- Statewide Water Quality Control Plans for Trash (State Water Resources Control Board)
- Final Part 1 Trash Provisions of the Inland Surface Waters, Enclosed Bays and Estuaries Plan (PDF) (State Water Resources Control Board)
- Storm Water Trash Implementation Program (State Water Resources Control Board)
- Certified Trash Full Capture Systems Available to the Public, updated August 2026 (PDF) (State Water Resources Control Board)
- Application Requirements for Trash Full Capture System Certification (PDF) (State Water Resources Control Board)
- Phase II Small MS4 Program (State Water Resources Control Board)
- Statewide Trash Amendments Track 1 Implementation Plan, September 2018 (PDF) (City of Chico)
- Statewide Trash Amendments Track 1 Operations & Maintenance Plan, September 2018 (PDF) (City of Chico)
- Storm Water Documents (City of Chico)
- Chico 2030 General Plan Draft EIR, Section 4.9 Hydrology and Water Quality (PDF) (City of Chico)
Last reviewed .