LID Practices at Northwood High School
Rainscapes
Initiative
Update
May 2007

Background

Friends of Sligo Creek and Neighbors of Northwest Branch members can help the creek and branch by using sustainable (environmentally beneficial) landscaping on their property, schoolyards, church grounds, etc. Sustainable landscaping practices like rain gardens are a form of Low Impact Development (LID). LID (also sometimes called rainwater harvesting, or green infrastructure), uses a wide array of innovative methods to retain, detain, filter stormwater close to its source, and to encourage ground water recharge. Instead of managing stormwater with large expensive centralized systems, stormwater passes through numerous small-scale decentralized controls.

The goal of LID is to restore important ecological functions in a watershed, such as filtering polluted water and recharging groundwater sources and stream "baseflows" (dry weather flows), while reducing stormwater runoff. To provide the most all-around benefits, LID practices typically also use vegetation - plants, shrubs, and trees - to clean pollutants (fertilizers, hydrocarbons, heavy metals, etc.) from stormwater runoff.

The overarching goal of the Northwood High School Sustainable Landscaping Plan is to undertake joint conservation landscaping projects on the Northwood High School property and in the surrounding communities. These joint projects are intended to bring students, parents, faculty and staff, and community partners together. Working together as a team, we will create a showcase of on-site rain gardens and other landscape features on the Northwood grounds that infiltrate rainwater, decrease stormwater runoff pollution, and provide focal points of beauty and wildlife habitat. As these projects will be student and teacher-led and community-supported, they will integrate with the MCPS curriculum and provide educational and career training, and service opportunities for the students.

The Goals of the Northwood High School Sustainable Landscaping Plan include:

  1. To reduce the negative environmental impacts of unchecked stormwater run-off and to boost the environmental contributions that can be made through sustainable landscaping at the Northwood High School site.
  2. To educate students, parents, and the community at large about the problems of stormwater runoff and about the benefits of Sustainable Landscaping (i.e. Bayscaping, Rainscaping) and other LID practices for both public and private facilities and back yards. Educational opportunities will include incorporating landscaping into the school curriculum, holding school and community work events, and installing educational signage.
  3. To enhance the appearance and interest of the schoolyard through high quality landscaping at the site. To show the community that LID and use of native plants can be a beautiful solution to stormwater runoff.
  4. To use this partnership and its resultant landscaping (including the proposed rain garden) as a model for other schools and other private and public institutions in the region.
  5. To provide experience and a showcase for designing and installing environmentally sensitive landscaping by horticulture students at Northwood High School.
  6. Once the students become proficient in environmentally sensitive landscaping, they will help implement these practices in the surrounding schools by mentoring other students and some will be inspired by their Northwood experience to go forward into a broad range of new environmental careers, including the growing new field of Sustainable Landscape Design..

By partnering with the Northwood High School, we hope to recruit volunteers who would not normally be involved with LID and watershed restoration projects. We hope to educate the public and instill a sense of participation in the restoration of the local streams and the Chesapeake Bay. One of the goals is that the workday participants and the parents of students will learn what they can do in their own yards to help improve water quality.

In summary there are many benefits to implementing Environmentally Beneficial Landscaping at Northwood High School, including:

The sustainable landscaping plan was part of a larger effort to manage stormwater at the site using LID practices. Other techniques include a pilot green roof, rain barrels, and pervious pavement.



Northwood Site Map

Implementing the Landscaping Plan

In the fall of 2006, the first phase of the Landscaping Plan was developed and implemented for the schoolyard. The plan called for the installation of one rain garden at the northeast corner of the building and two rain gardens in the enclosed courtyard (by the Montgomery County Department of Environmental Protection).

The Rain Gardens

The First Proposed Rain Garden Site at Northwood


The existing conditions of the first rain garden location: A rainleader discharged runoff from the roof directly on to the schoolyard lawn. The concentrated runoff eroded the compacted lawn. This was contributing to sediment in the Northwest Branch. The downspout also contributed to the flooding in the nearby parking lot.

Installing rain gardens at the schoolyard would not only provide a visible and high profile location, but also address the stormwater runoff problem mentioned above. Too often, property owners treat stormwater as a problem to be addressed by moving it off their property as quickly as possible, causing localized flooding and environmental damage to the nearby steams. Instead of treating rainwater as a problem to be removed, it will be used as a resource to enhance the schoolyard. It will be used to create colorful and interesting landscaping, while also creating a wildlife habitat and greatly increasing groundwater recharge.

On October 14, 2006, we had our first formal Rain Garden Workday. Before the formal workday, the students and teachers at Northwood prepared the site by excavating the clayey soil creating a basin. About 25 enthusiastic students, parents, teachers and members of Friends of Sligo Creek and Neighbors of Northwest Branch participated in this first workday.

Student and Community Volunteers on the October 14, 2006 Rain Garden Workday





Green Roof

Greenroofs are lightweight, low-maintenance vegetated roof systems used as a cost-efficient, eco-sensitive alternative to conventional roofing. Greenroofing offers an attractive alternative to the barren deserts of tar, gravel and asphalt usually seen from urban windows. In addition to reducing stormwater runoff, green roofs significantly reduce roof temperatures (and energy use), provide wildlife habitat, and extend the life of the roof. There is a long and successful use of green roofs in Europe. The science teachers in the school have integrated the green roof into their curriculum.

In August 2005, MCPS installed a pilot green roof at Northwood High School. The pilot green roof is 600 square feet and is expected to reduce runoff by 50%. The green roof uses 2" of soil (extensive green roof). This pilot green roof is the first one installed on a Montgomery County Public School. The MCPS Design and Construction Division is monitoring the roof's performance. This green roof was made possible in part by a $15,000 grant by the Chesapeake Bay Trust. After one year the green roof has done well. The plants (sedums) have survived periodic droughts that occurred all year long. There have been no reported leaks. An interesting story was told about the green roof soon after it was installed. Soon after installation, there was heavy rain. The teacher responsible for obtaining the green roof was notified that the green roof was leaking. When she investigated the situation, she found leaks everywhere in the school, except under the green roof. The green roof was about the only roof that had no leak problems.

For more information about the pilot green roof, Click here.

Pervious Pavement.

A standard parking lot sheds 16 times the amount of water that a meadow does. To reduce the amount of runoff, pervious pavement can be used. Pervious Pavement is hard surface that allows rainwater to seep through the paved surface and into the soil as nature intended. This process can greatly reduce or eliminate the need and the cost of expensive stormwater drainage systems and retention areas. The pavement is comprised of a special blend of Portland Cement, coarse aggregate rock, and water. Once dried, the pavement has a porous texture that allows water to drain through it.

Porous asphalt pavement consists of standard bituminous asphalt in which the aggregate fines (small particles) have been screened and reduced, allowing water to pass through the asphalt. Underneath the pavement is placed a bed of uniformly graded and clean-washed aggregate with a void space of 40%. Stormwater drains through the asphalt, is held in the stone bed, and slowly infiltrates into the soil.

In addition to the environmental benefits of reduced stormwater runoff, another advantage to pervious pavement is safety. There is no standing water on pervious pavement. During cold weather, therefore, ice does not readily cover sidewalks and parking lots.

Photos of pilot pervious sidewalk and parking lot near the southeast corner of the schoolyard.
MCPS is using the pilot pervious parking lot and sidewalk to test the effectiveness of these techniques.