Development of a Green Street LID Selection and Design Guidance Manual
The Green Street LID approach uses hydrologically-functional site design techniques or practices that store, retain, infiltrate, and treat stormwater and dry-weather runoff from local, individualized watersheds or sites that drain onto street corridors. Rather than relying on general design standards to develop and approve Green Street LID systems to meet local MS4 permit requirements, the City of Santa Clarita embarked on developing customized design guidelines to provide site-appropriate guidance that best reflects their diverse landscapes while addressing several other needs. During this presentation, the programmatic planning and criteria for standards will be presented so that session participants can learn what kind of criteria considerations can be employed for their local jurisdictions.
The City of Santa Clarita is the 3rd largest City in Los Angeles County covering 53 square miles consisting of high- and low-density residential, commercial, industrial and institutional development areas, as well as large areas of open space, and resides within the Santa Clara River watershed. Each location brings a unique set of challenges and an off-the-shelf construction-ready drawing was difficult to implement. The City desired continuity in their standards for design for function, aesthetics and maintenance. The customized design manual developed allows the user to determine the type of Green Street LID projects; evaluate specific site characteristics and constraints; and identify the possible solution(s) through a decision-making matrix tool.
The manual was developed specifically to:
• Assist City staff in identifying Green Street LID projects
• Provide a decision–making matrix to help the staff select the appropriate LID
• Assist City Staff in the sizing and design of LIDs
• Ensure standardized design and continuity with landscape and city standards
• Ensure standardized operations and maintenance practices
• Support accurate construction cost estimating and scheduling
The manual and its tool address six major types of LID practices including:
• Bioretention rain gardens
• Bioretention tree box filters
• Rock garden infiltration trenches
• Permeable pavements
• Green space vegetated buffers
• Enhanced open swales
Isometric cross sections of these practices are presented along with a description and list of benefits for each alternative. User-friendly tables guide the reader by defining the site requirements and constraints, as well as several key consideration categories with comparative values for:
• hydrologic functions
• pollutant removal efficiency levels
• cost ranges
• maintenance cost ranges
Perhaps the most important part of the manual is the guidelines it provides for the suitability of each type of solution for various project types. Based on user goals and applications, the manual provides a simple selection process for identifying the most suitable green street LID alternatives. The manual provides case examples which will also be presented during the conference session so attendees can see a demonstration of the manual’s selection tools in practice with real-world and common design scenarios. Fact sheets were developed for the manual to provide specific design principles that must be followed. The manual includes standard detail drawings for the user to adapt to their project site, as well as a dedicated section on maintenance requirements.
This session will provide in-depth detail of the decision-making process that was undertook and methodology for developing key criteria to ensure green street LID systems will be implemented that both operate effectively and add to the aesthetic quality of the community. Several examples and visuals will be presented to illustrate the guideline development process.