City of Temecula LittaTrap™ Retrofit

City of Temecula – Catch Basin Retrofit Case Study

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Location: City of Temecula, California

Program: Phase II MS4, Track 1 Implementation Plan

Engineer: CASC Engineering

Devices: 124 × LittaTrap™ systems installed (10% were custom engineered solutions)

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Project Overview:

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As part of its Phase II MS4 Track 1 Implementation Plan, the City of Temecula delivered a large-scale retrofit programme targeting 124 existing inlets across its stormwater network.

Following detailed hydraulic assessment, it was identified that ~10% of inlets exceeded standard trash capture flow capacity, requiring customised engineering solutions.

The upgraded system was tested under a 10-year storm, successfully maintaining performance with no operational failure.

This project was driven by the need to improve durability, maintenance efficiency, and full regulatory compliance for trash capture across a wide range of inlet types and site conditions.

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Project Objectives:

The City required a solution that would:

• Deliver long-term durability across varied infrastructure
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• Enable hand or vactor maintenance from ground level
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• Eliminate confined space entry requirements
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• Meet full trash capture flow rate compliance across all sites

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Engineering Assessment & Site Analysis:

Working alongside CASC Consultants, each catchment was analysed to determine flow rates, contributing areas, and inlet conditions.

Using site data, measurements, and imagery, tailored configurations were developed to ensure each inlet met performance requirements—particularly those with higher hydraulic demand.

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Customised Design Approach:

To address higher flow conditions and varying geometries, several engineered solutions were implemented:

• Double basket systems to increase capture capacity and improve bypass performance
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• Modified trough angles to optimise hydraulic behaviour
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• Additional baskets for high-load locations
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• Flexible design adaptations for non-standard inlet geometries
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• These adjustments ensured compliance without compromising safe, ground-level maintenance access.

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Maintenance Strategy & GIS Integration:

The project extended beyond installation to long-term asset management. Inlets with specific maintenance needs were integrated into the City’s GIS system, enabling:

• Prioritised hand maintenance where practical
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• Reduced reliance on vactor trucks
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• Improved maintenance scheduling and lifecycle planning
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Proven Performance in the Field:

During a significant storm event, the retrofitted systems demonstrated:

• Effective capture of trash and debris at source
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• Adequate bypass capacity for high-flow conditions
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• Reliable performance with no system failure
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Configurations Utilised:

A range of LittaTrap configurations were installed to suit site-specific needs, including:

• LittaTrap™ EMMA

• Custom flange LittaTrap™ units

• High Capacity LittaTrap™ systems

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Summary:

The City of Temecula retrofit demonstrates how engineering-led design, adaptable solutions, and strong municipal collaboration can deliver compliant, high-performing stormwater outcomes at scale.

By upgrading 124 inlets with a combination of standard and customised LittaTrap™ systems, the City is improving water quality, increasing maintenance safety, and achieving long-term operational efficiency—without the need for confined space entry.

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Testimonial on site after maintenance presentation:
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