Guidance on Green Infrastructure: Making LID in the Right-of-Way Standard Practice
Main idea, Purpose & Theme:
By standardizing how LID is placed in the Right-of-way the County has reclaimed valuable space for people to enjoy, turned a burden into a resource, and reduced irrigation demand and stormwater runoff.
The County commissioned a Life Cycle Cost Analysis (LCCA) evaluating the costs for construction, maintenance, rehabilitation, administrative, and salvage costs for seven County roadway types under the 2013 MS4 Permit versus Green Streets principles. The findings of the LCCA showed that over a 20-year life cycle, the Green Streets option reduced overall costs by 35% compared with the conventional 2013 MS4 Permit road widening projects.
The positive results of the Life Cycle Cost Analysis allowed for the County to pursue the next step which was putting together Guidance on Green Infrastructure, with research efforts by the County Development and Construction Section of the Watershed Protection Program on the many Green Streets programs nationwide.
Summary of tools, ideas, and concepts:
As part of its BMP Design Manual the County has published Appendix ‘K’ – Guidance on Green Infrastructure. These tools are to be used to uniformly design, install and maintain LID features in the County’s public Right-of-way for years to come.
Green Streets Guidelines are an outreach tool and are also intended to serve as a companion to the rest of the Green Streets publications. They include an introduction, strategies, procedures and design examples for implementing Green Streets projects. The strategies include tree wells, rain gardens, rock gardens, and permeable pavement. Green Streets Design Criteria lay out general definitions, general policy, and landscape design criteria for Green Infrastructure strategies. Green Streets Design Standard Drawings includes construction details which may be referenced in improvement plans. Green Streets Maintenance Schedules include a list with maintenance tasks, frequency, and time of year for initial, routine, and as-needed maintenance of each strategy. Green Streets Specifications include detailed construction material and installation requirements for strategies including aggregates, geosynthetics, underdrains, permeable pavement, engineered soil media, mulch, overflow risers, check dams, and tree grates.
Preparation was vetted throughout seven large group meetings with different County Departments and divisions, external outreach presentations to Associated General Contractors, Construction Management Association of America, and the local Land Development Industry Group, as well as presentations at an American Public Works Association luncheon and a workshop on BMPs for Public Works Projects at the 2014 CASQA conference. Some County team members made site visits to the Los Angeles and Orange County areas, as well as local sites within the City of San Diego to review recently implemented green street type projects and talked with municipal staff and consultants in order to gather their lessons learned.
The County was the first jurisdiction within the Copermittees to include Guidance on the implementation of Green Streets, which goes above and beyond the Model BMP Design Manual. According to the Life Cycle Cost Analysis, implementing Green Streets would save an average of 35% compared with a conventional Priority Development Project over a 20-year period. The publication of the Guidance on Green Streets was a true collaboration effort between DPW Divisions and across departments with PDS’ participation.
How we intend to engage the audience:
In the past Stormwater treatment has been achieved by placing unsightly basins at the back of developments, out of sight, behind tall walls, or buried under ground. The County of San Diego proposes to bring these facilities front and center.
When LID is integrated with complete street concepts numerous co-benefits strengthen the three pillars of sustainability; the environment, social equity, and the economy.