Case Study: Award-Winning LID Design
Posted by J.R. at 10:41 AM
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Our guest blogger, Mikel Wilkins, PE, ENV SP, from Freese and Nichols Dallas, describes how their design team used Envision to develop an award-winning LID design. Mr. Wilkins leads Freese and Nichols in-house Sustainable Design Technical Excellence Program. He also serves on the national education committee for the Institute for Sustainable Infrastructure. Mr. Wilkins has 18 years of project experience in water resources and site civil design. His recent experience includes evaluation of sustainable practices for the design and planning of major water transmission projects for communities in the North Texas region. Mikel is one of the first professionals in the country to receive the Envision SP credential and he is also an ISI Verifier.
The Freese and Nichols design team of Lane Wheetley, PE, Ben McWhorter, EIT, and Todd Buckingham, EIT, ENV SP, recently won the North Texas Land/Water Sustainability Forum Low Impact Design (LID) competition by going a step beyond employing LID strategies and considered the project's overall sustainable performance over its expected lifespan. The competition featured a roadway retrofit of South Lamar Street in Dallas, TX. The primary objective of the competition was to prepare conceptual plans for the design of the retrofit using LID strategies that would meet the new stormwater management requirements soon to be implemented in Dallas. The existing roadway bordered by fully developed residential properties on one side and industrial recycling facilities on the other presented additional challenges due to the surrounding land use and the condition of the existing infrastructure systems.
Design teams were required to meet the roadway retrofit design challenge while keeping construction and long term maintenance costs below that of traditional design methods. The Freese and Nichols LID design had an initial cost savings of 8% over the standard design and a 17% savings each year throughout the project's life cycle. The 8% savings for construction were from reducing the amount of pavement and pipe materials by utilizing green infrastructure for storm water management. The 17% annual O&M savings were from reduced future maintenance of the pavement due to moisture treatment of subgrade, lower energy costs for LED lighting and the use of low maintenance landscape materials within green infrastructure zones.
Buckingham, a credentialed Envision Sustainability Professional (ENV SP), assisted the team by leading a review of the Envision Checklist during a design charrette. The brief overview of the Envision rating system led into a brainstorming session where the project team listed design ideas that would boost the project's contributions to sustainability and therefore increasing the project's Envision rating system score.
Some of the key features of the winning design included:
- A roadway that would last 35 years before any replacement would be required (LD3.3 Extend Useful Life)
- Recycled concrete, recycled crushed concrete base, milled and reused asphalt bonding layer, and moisture treated subgrade (RA1.3 Use Recycled Materials)
- The proposed concrete roadway with an SRI greater than 29 and the adjacent landscaped areas help reduce heat-producing surfaces (CR2.5 Manage Heat Island Effects)
- Complete streets design featuring shared travel lanes, on-street parking and wider sidewalks (QL2.4 Improve Community Mobility and Access; QL2.5 Encourage Alternative Modes of Transportation; QL2.6 Improve Site Accessibility, Safety and Wayfinding)
- Bioretention cells landscaped with drought-tolerant plants to treat stormwater runoff (NW2.3 Prevent Surface and Groundwater Contamination)
- Local landscaped areas adjacent to the roadway help to reduce the overall impervious cover (NW2.1 Manage Stormwater)
- The irrigation system that will distribute water to the local landscaping will use a smart controller and an integral weather station to tailor the watering schedules with a smart controller. (RA3.2 Reduce Potable Water Consumption)
- New pedestrian amenities including bus stations, benches, shade trees, bike share stations and colorful landscaping (QL2.5 Encourage Alternative Modes of Transportation)
- Transit station kiosks highlighting neighborhood history and providing maps showing clear connection points to surrounding neighborhoods, parks, hike and bike trails and other nearby destinations. (QL3.1 Preserve Historic and Cultural Resources; QL2.6 Improve Site Accessibility, Safety and Wayfinding)
- LED Street Lighting with directional control to decrease light pollution and dimming, and motion sensing capability to decrease energy usage. (QL2.3 Minimize Light Pollution; RA2.1 Reduce Energy Consumption)
Thoughts on Using Envision
With the increased implementation of LID design practices we often see projects that disregard other important factors of sustainability by focusing solely on stormwater management components. The Envision rating system allowed the project team to craft the project for maximum sustainable performance by taking advantage of the objective and subjective criteria brought forth by the system. This assured that the project would not be singularly focused on just LID design criteria but would implement concepts that ultimately increased quality of life and economic indicators within the project's impact area.