Background

The Vancouver Public Library Central Branch has more than just books and information, it has a library garden, or more specifically a rooftop garden. In 1995 the central library in Vancouver was constructed along with the garden (1). While the rooftop garden is maintained by city workers, the British Columbia provincial government will occupy the two floors directly below the garden until 2015. This makes it hard for the city to have complete control around the entire area of the garden (2). The rooftop garden was constructed at a cost of $250,000 (3).

Project Description

The roof of the library itself is 28,000 square feet, with the garden taking up 20,000 square feet of that space. The rooftop garden was created and designed by architect Moshe Safdie, and landscape architect Cornelia Oberlander (1). This rooftop garden is not accessible to the general public, only to maintenance workers who need to be up on the roof. However, it is integrated into the roof of the library, as well as the skyline of the city. The other buildings nearby have an excellent view of the rooftop garden. (4). One of the reasons it isn't available to the pubic, is that the final costs of the library didn't incorporate a public rooftop garden. More funding would have been needed in order to make the rooftop garden safe for the public to visit (5).
VPL_grasses.jpg
Vancouver Public Library Rooftop Garden, Close up of the fescue grasses; reproduced with permission.


In fact, it is very difficult for anyone to get up on the garden at this point in time. First you must begin in the electronic surveillance center of the library. Then you have to go through several doors, and enter an elevator and go up nine floors. Next you need to go through a lobby and enter a small room that has a tall metal ladder. Lastly you must climb up the ladder, open the hatch to the roof, and step over a sill in order to finally get up on the rooftop garden on top of the library. So it is easy to understand how much work needs to be done in order to get the rooftop garden accessible to the general population (6).

The rooftop garden is mainly composed of blue and green fescue bunch grass, as well as kinnickinnick. Fescue is a type of perennial grass (7). Kinnikinnick is a type of bearberry that has beautiful foliage and bright red berries (8). The plants in the rooftop garden are arranged in such a pattern to mimic the flow of the nearby Fraser River (5). These plants were chosen to be used in the garden because they are very easy to maintain, as they don't require very much water or fertilizer in order to thrive. Both species of plants are indigenous to Vancouver (9). A simple irrigation system is also used in order to help the plants during the warmer summer months (4). There are also some Japanese maple trees on the roof, which have grown considerably since first planted in 1995. However, they are not planted in the garden itself, but down one story on a ledge that at onetime was space for an outdoor plaza (6).

The plants in the rooftop garden are planted in a soil depth of 14 inches. They were chosen because of their light weight when wet, which was calculated out to not exceed more than 70 pounds per cubic foot, for this particular roof structure. Any more than that, and there could be serious structural problems for the roof. The pH level of the soil needs to range from 6.0 to 6.5. The soil on the roof is made up of three equal parts of materials. The first third is washed sand, the second third is pumice, and the last third is Humus Builder. Humus builder is made out of entirely organic material, much of it made from local compost (4). The membrane on the roof is a type of rubberized asphalt created by American Hydrotech. The drainage layer is a product called NilexWD15WP, invented by the Nilex Group (10).
VPL_aerial.jpg
Vancouver Public Library Rooftop Garden, aerial view of the garden; reproduced with permission.


Since water adds a large amount of weight to any roof, especially if it stays there over time, like in a rooftop garden, a way for the excess water to be taken off the roof needed to be solved. On the bottom of the roof there are six inch drains. There are eight drains in total on the roof, but only two of them drain the actual rooftop garden area of the roof. These pipes go down towards the ground, near the parking area of the library. These go through two different types of flow meters. Depending on how much water is coming through the meters, there are two possibilities for the water to go. Small amounts of water draining go through the low flow meter to the building's sump, which then pumps it into the city storm system. Large amounts of water go through the large flow meter, and bypass the smaller meter and goes directly to the city storm system (10).

There is also a really interesting weather station installed in the rooftop garden. The HOBO Weather Station was installed in the summer of 2003. It has the ability to monitor and record solar radiation, temperature, soil moisture, gust speed, wind direction, wind speed, humidity, and rainfall. It is located in the southeast corner of the garden, in order to maximize the exposure to wind and rain. It was placed here as the installers felt it would give the most accurate and average data when taking measurements. It registers information in five minute intervals, and is also grounded into the soil in case of lightning strikes (11).

As previously mentioned, control of the two floors directly underneath the rooftop garden will be turned back over to the library, unless the British Columbia provincial government renews its lease on those floors (2). The provincial government rented out those top two floors in 1995, they leased it out at a rate of $1 million in total (12). But, as of now it appears that the city of Vancouver will indeed get control over those floors by that time. This is both a good thing and a bad thing for the city of Vancouver. This is due to the fact that they will now be able to make the garden a public space, but they don't have the money to do so just yet (2).

Steps to remodel the rooftop garden are underway. The city would like to create a public place out of the garden, something that everyone could enjoy. To do this, several things would need to be changed in the garden. First, a walkway system would need to be installed. Also, guard rails would need to be installed to keep people within the garden, preventing them from wandering too close to the edge of the building. Lastly, either an escalator or an elevator would need to be installed as now there are only maintenance entrances to the rooftop garden. Most likely it will be up to the taxpayers of Vancouver to foot the bill of the remodeling process (2). A cobblestone walkway was originally intended to be the main means of transportation in and around the garden, as well as a well shaped out and defined sitting area would have been on the western side of the garden. Both of these additions were scrapped when funding for the rooftop garden started to decline, and only essential aspects of the original design were included (12).
VPL_in_the_garden.jpg
Vancouver Public Library Rooftop Garden, View from the garden; reproduced with permission.


Some funding has already been obtained for the process, $250,000, from a Vancouver philanthropist named Yosef Wosk (13). Cornelia Oberlander, the original landscape architect who worked on the project, is already helping out for the redesign, as is Mose Safdie the architect who helped create the garden (6). The entire city would like to see this site become accessible to everyone who wants to enjoy it. This will help get out the message on why the rooftop garden was built in the first place, by educating the public that rooftop gardens help improve air quality, absorb heat, and also help to lower the temperature of the area around it (14). It is hoped that the redesigned rooftop garden will be open to the public by 2015, the same year that the lease currently held by the British Columbia provincial government on the top two floors of the library will expire (6).

Links

Vancouver Public Library Green Roof Monitoring Project
Garden in the Sky
Rooftop gardening
A field of waves on the Vancouver skyline
Sitelines - Library Square
VPL Rooftop garden in jeopardy
Flickr - "Up on the roof"
Does the central library have a rooftop garden?
Vancouver Public Library

References

(1) Johnston, Chris and Kathryn McCreary, and Cheryl Nelms. “Vancouver Public Library Green Roof Monitoring Project”. <http://kwl.bc.ca/docs/GreenRoofPaper04-0430FINAL.PDF>. Page 1.
(2) "VPL Rooftop garden in jeopardy". <http://www.blundellblossoms.ca/blog/news-vpl-rooftop-garden-in-jeopardy/>.
(3) Hobbs, Heather. 4 Apr. 2002. “Rooftop gardening”. <http://lifecyclesproject.ca/resources/downloads/Rooftop_Gardening_Hobbs.pdf>.
(4) Johnston, Chris and Kathryn McCreary, and Cheryl Nelms. “Vancouver Public Library Green Roof Monitoring Project”. <http://kwl.bc.ca/docs/GreenRoofPaper04-0430FINAL.PDF>. Page 2.
(5) Vancouver Public Library - Branch Locations & Hours. "Does the Central Library have a rooftop garden." <http://www.vpl.vancouver.bc.ca/branches/generic/central_library_faq#garden>.
(6) National Post. 24 July 2006. “A field of waves on the Vancouver skyline”. <http://www.canada.com/nationalpost/columnists/story.html?id=e9c72a4f-02c8-4aa5-98ef-417c4eede748&k=2453&p=1>. Page 1.
(7) Fescue. (2010). In Merriam-Webster Online Dictionary. Retrieved May 2, 2010, from <http://www.merriam-webster.com/dictionary/fescue>.
(8) Bearberry. (2010). In Merriam-Webster Online Dictionary. Retrieved May 2, 2010, from <http://www.merriam-webster.com/dictionary/bearberry>.
(9) Dudfield, Travis. 31 July 2009. Vancouver Courier. “Garden in the Sky”. <http://www2.canada.com/vancouvercourier/news/story.html?id=3e5dc38b-e69e-48bf-92bb-af4383527a5b&p=1>. Page 4.
(10) Johnston, Chris and Kathryn McCreary, and Cheryl Nelms. “Vancouver Public Library Green Roof Monitoring Project”. <http://kwl.bc.ca/docs/GreenRoofPaper04-0430FINAL.PDF>. Page 3.
(11) Ibid. Page 5.
(12) Dudfield, Travis. 31 July 2009. Vancouver Courier. “Garden in the Sky”. <http://www2.canada.com/vancouvercourier/news/story.html?id=3e5dc38b-e69e-48bf-92bb-af4383527a5b&p=1>. Page 1.
(13) Dudfield, Travis. 31 July 2009. Vancouver Courier. “Garden in the Sky”. <http://www2.canada.com/vancouvercourier/news/story.html?id=3e5dc38b-e69e-48bf-92bb-af4383527a5b&p=1>. Page 2.
(14) Sitelines - A web atlas of landscape architecture in British Columbia. <http://sitelines.org/webatlas/vandowntown/vpl.html>.