Finishing Up: Final Designs

The figures below illustrate the final 3D designs and the 2D dimensions for the 30th Street Station Green Roof. The plants shown in the 3D model are examples of plants provided by the SketchUp program and are not the exact sedum varieties chosen for the roof.

Figure 1

Figure 2

Figure 3

Figure 4

Finishing Up: Calculations and Budget

Calculations: 

Figure 1

Figure 1 shows pie charts detailing the effect the green roof on 30th Street Station would have on the amount of rainwater runoff the station generates. The baseline scenario is the roof in its current state and the "Current Scenario" would be with the green roof added. While the 9% change in runoff is relatively small when compared to other types of stormwater management systems, it should be noted that green roofs are not known for reducing runoff, but holding water. Using the area and the full saturation rate, it was determined that this green roof design could hold 180,840 lbs of water.

Budget: 

Category	Amount	Unit Cost	Total Cost
Rooflite Materials	748.59 ft3	$113	$84,750.00
Green Roof Solutions Roof Protection	508 ft2	$200	$400.00
Delivery	--	$860	$20,640.00
		TOTAL	$105,590.00

The table above shows the estimated costs of the materials that we chose from each company. These costs come directly from quotes that each company provided. In addition to this initial cost, there is an estimated annual maintenance cost of $1,000.

Plant Selection

Over the past few weeks, the team has been working extensively on researching the types of plantations to use in our green roof garden. The roofs of buildings can be a cchallenging condition for plants to grow because of elevated temperatures, wind exposure and high light exposures. In the case of 30th station, this condition is especially true since it does not have any shadings of other high rises over it.

 We then looked into the weather of Philadelphia, especially West Philadelphia:

1. The driest month in Philadelphia is February with 2.74 inches of precipitation, and with 4.39 inches July is the wettest month.
2. Philadelphia's coldest month is January when the average temperature overnight is 25.5°F. In July, the warmest month, the average daytime temperature rises to 85.5°F.

From this information we learned that Philadelphia has a radical climate change over the four seasons, which means our plants need undergo a harsh winter(snow and low temperature) and dry months.

50% of our plants will be all seasons sedum because Sedums and other succulent plants are often used on green roofs because they are tolerant of the dry conditions found on most roofs.(source) We then made a list of particulars for our plants and came up with a plan which we think would be efficient for the garden.

1. Vegetation: minimum 95% coverage ·
1. Fiber/soil base: approximately 1” thick
2. Size: 12”w x 24”l x 2-3”h (2 sq. ft. per tile)
3. Max weight: 5.48 lb./sq. ft. fully saturated
2. Maintenance: Minimal maintenance requirements once established

Excursion to the Free Library roof top

In order to gain a better understanding of green roof installment and plant selection, the team went on a trip to the Free Library of Philadelphia where a semi-intensive green roof was installed in 2008. According to the library website, the garden contains more than 5,400 plants. Sedums include Murale White Stonecrop, Blue Cadet Creeping Sedum, and Blue Spruce Stonecrop along with grasses such as Blue Grama, Feather Reed Grass, Blue Fescue, and Prairie Dropseed. This green roof was the first green roof on a government-owned building in the city of Philadelphia and has a beautiful view of central Philadelphia from the terrace (Figure 1). 

Figure 1

The team was able observe the garden and its drainage system closely(Figure 2). We also talked to the library officials and hope to develop further contact with the lead designer of this garden to gain more insights. 

Figure 2

Preliminary Design

This is a possible design of our green roof(Figure 1), we are still working on the layers and material of the roof. We discovered that the building's roof was enhanced for the landing of aircrafts in a time of emergency. Therefore part of the green roof will be serving as a air purifier as well as an emergency heliport! In our design, the roof will be covered by a layer of extensive green roof and pathways in between. Since the roof has been designed for the landing of aircrafts, it is enhanced with Alabama Limestone. Because of this, we know that the roof will be strong enough to hold a larger coverage of green roof. We also aim to develop the roof into a public area where people could stay and hang out.

Figure 1: Preliminary design of 30th green roof 

Research So Far

As of Week 3, we have decided to create an extensive green roof for 30th Street Station. The area over the main concourse, which we will be redesigning, covers an area of approximately 64,000 square feet.
Here are some of the basic layers of the green roof we will be designing:

• The growing medium supports plant growth and provides for storage of stormwater within voids. The storage capacity is a function of medium depth, surface area, and total void space.
• Filter or separation fabric, or geotextile, prevents migration of soil into the underlying drainage layer of the green roof.
• A drainage layer may incorporate measures to intercept and retain percolated rainfall as it moves through the green roof storage area. Examples include membranes with depressions to hold water and specialized fabrics or mats with high capillary indices.
• Moisture interception layers/root barriers are impermeable liners that protect the underlying roof deck from moisture and plant root intrusion. Some waterproofing materials are inherently root resistant, whereas others require an additional root barrier.
• Underlying roofing systems typically consist of a structural deck, its supporting structures, and a traditional overlying waterproofing system.

We are also going to take our research into the field, where we will look at other green roofs in Philadelphia, specifically the Free Library of Philadelphia and Cira Green Rooftop Park. 

Project Proposal

Cira Green, Philadelphia, PA
An example of a well furnished green rooftop
Completed by the Roofmeadow Studio

As a direct solution to participate in the Philadelphia’s Stormwater Management System and to reduce the negative effects that stormwater runoff brings, this project intends to create a systematic stormwater management program on the rooftop of the 30th Street Station using Green Stormwater Infrastructure (GSI). The motivation for this project is to update the station and lessen its negative impact on the environment. The goal is to decrease the impervious surface, which prohibits water from infiltrating the ground, on stormwater runoff within Philadelphia. The impervious areas lead to a greater problem, which causes increased stormwater runoff and higher stormwater peak flows. Therefore, located on Market Street, the 30th Street Station is chosen as the project site because of its encompassment of a large impervious surface -- 95% of its ground is impervious. The completion of the project aims to turn this area into an environmentally friendly surface which functions to minimize stormwater runoff, and to purify the air of Philadelphia. There are some major technical obstacles such as a steep learning curve for certain computer software and creating a physical model to scale. The major tasks of this project include: literature studies, calculation, computer programing, creating a physical model, and completing the final project report. To complete this project, a pragmatic project must be carried out, which includes a base plan, drainage area map, proposed design plan, sections & profiles of proposed systems, and GSI sizing & runoff calculations.