Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
Horticulture
Non Technical Summary
One only needs to visit any `big box' store on the urban strip to view acres of asphalt covering soil that had previously allowed rain and snow to replenish the water table and support vegetation that cooled the air. These large asphalt parking lots are ubiquitous in every community and there is every reason to believe that they will only increase in number as commercial development occurs. Concomitant with large expanses of asphalt comes tremendous heating of the air (more than 10C warmer in the parking lot), a reduction of water filtration and recharge into the water table and the added expense of putting in storm drainage to carry precipitation into storm sewers. It may be possible, however, to combine the use of porous asphalt, structural soil, grass and trees to create parking lots that absorb rainwater, cool the urban core and are less expensive to build than conventional parking lots with storm drainage. This new green technology will address environmental problems caused by development by reducing flooding and the need for costly drainage infrastructure, purifying water as it recharges the water table and cooling the air while absorbing carbon dioxide. This will provide new business opportunities and change the way development is carried out by both public and private agencies. Structural soil is a medium developed at Cornell University's Urban Horticulture Institute to meet engineers' specifications for a compacted, load-bearing surface beneath pavement while simultaneously allowing tree roots to grow through it. Prior to the development of structural soil, soil compaction was so severe under pavement that tree roots were often restricted in their growth resulting in a stunted tree and early tree mortality. By combining structural soil with porous asphalt, the requirements of a drivable surface can be met while allowing trees to grow under the pavement. Wear-tolerant grasses have also been shown to grow in structural soil. It may be possible to plant certain wear tolerant grasses on structural soil to handle less frequently used areas of the parking lot that receive moderate traffic while using trees planted in structural soil with a porous asphalt surface in higher use areas. The city of Ithaca, NY is interested in testing the combined features of structural soil, porous asphalt, grass and trees to develop a thoroughly green parking lot that significantly reduces storm drainage and cools the environment. The first phase of the research will be to design and test variations of a green parking lot using different depths and configurations of structural soil under grass and porous asphalt with trees planted directly into the structural soil. Different species of grasses will be tested for wear tolerance under car traffic. The parking lots will be designed to accommodate the 100 year storm and tested with instruments that measure the water table and rate of draw down. Much of this can be done in field plots. Subsequently the best design will be constructed in Ithaca. Environmental effects and economic costs will be compared between traditional and new green parking lot models.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Structural soil is a medium developed at Cornell to meet engineers' specifications for a compacted, load-bearing surface beneath pavement while simultaneously allowing tree roots to grow through it. By combining structural soil with porous asphalt, the requirements of a drivable surface can be met while allowing trees to grow under the pavement. Wear-tolerant grasses have also been shown to grow in structural soil. It may be possible to plant certain wear-tolerant grasses on structural soil to handle less frequently used areas of the parking lot while using trees planted in structural soil with a porous asphalt surface in higher use areas. If successful, the development of this project will reduce the need for costly storm drainage infrastructure, reduce flooding, provide water purification and recharge into the water table, cool the urban heat island and increase carbon sequestration. The goals of the proposed research are to combine the technologies of structural soil with porous asphalt in parking lots to decrease air temperature and allow water recharge and filtering. Specifically we plan to measure the growth and transpiration of trees and turf as a substitution for asphalt in porous parking lots to determine the effect they have on water table draw down, to compare the effects of grass as a substitute for asphalt and its impact on the reduction of heat generated by asphalt, to determine the best spacing and design of trees in porous parking lots to optimize pavement and car shading and to test the growth and wear tolerance of different turf grasses grown in structural soil under simulated vehicular traffic. In addition, we will compare hydroseeding vs. sod establishment by cost, timing and weed control as a substitution for asphalt, to compare regular vs. infrequent mowing effects on wear tolerance and to compare carbon sequestration and carbon emitted using grass, trees and pavement both during establishment and maintenance of the site. We intend to partner with a municipality or state agency to implement porous parking lot technology in New York. Specifically we want to work with municipal and state agency engineers to develop guidelines and designs and to develop a manual detailing how to design and construct a porous, green parking lot as a guide for other communities and developers.
Project Methods
The city of Ithaca, NY is interested in testing the combined features of structural soil, porous asphalt, trees and turf to develop a thoroughly green parking lot that significantly reduces storm drainage and cools the environment. We intend to test these features in combination and evaluate their effects and costs. The first year of the research will be to design and test variations of a green parking lot using different depths and configurations of structural soil under grass and porous asphalt with trees planted directly into the structural soil in field plots that have already been developed for this purpose. Different species of grasses will be tested for wear tolerance under car traffic. Turf-type tall fescue (Festuca arundinacea) is a wear-tolerant cool season turf grass species that is widely used in high traffic sports turf situations, including horse track surfaces and is able to tolerate the abrasion and compaction associated with weight-bearing stress. Preliminary research has demonstrated the success of using turf-type tall fescue sod transplanted directly on the surface of the structural soil. However, contractors might find the use of sod to be cost prohibitive in the short term and therefore an alternative means of establishing tall fescue is required. The process of hydraulic seeding consists of mixing mulch, seed, fertilizer, soil activators and glues, and then spraying these onto the soil creating a seeding mat which, when watered several times a day, keeps moisture next to the seed for quick germination. We will investigate two establishment methods using hydraulic seeding and two seeding rates of tall fescue. 1. Hydraulic seeding directly on the surface of the structural soil. 2. Apply a 0.5cm layer of sandy loam soil and hydraulic seeding on the surface of the soil. In addition, two seeding rates of tall fescue will be used to determine which develops the most rapid wear -tolerant turf. 1. Normal lawn seeding rate of 250 kg ha-1. 2. High seeding rate 500 kg ha-1. Sod establishment will be compared to hydroseeding as an establishment method on top of structural soil. The parking lot plots will be designed to accommodate the 100 year storm of 6 inches of rain in 24 hours, and tested with instruments that measure the water table level and rates of transpiration of trees and turf. Subsequently, during the next year, the best turf and tree establishment practices will be constructed by the City of Ithaca and a design manual documenting best practices will be created. During the subsequent 2 years, the durability of turf and porous asphalt with trees planted into structural soil will be evaluated. Growth, water uptake, turf wear resilience will be measured periodically over the year. Environmental effects on temperature and storm water runoff and storm water filtration will simultaneously be measured. The economic costs of establishment and maintenance will be compared between traditional and new green parking lot models.