Implementation
The two flowcharts below are presented to propose which infrastructure solutions would be ideal under which conditions that exist in different parts of a city, but both flowcharts can be applied to any city. The first tier of conditions considers if land is in the city center or if land is in the periphery. City center land is defined not by population density or radius but by impervious surface area, the percentage of the ground that is paved and which therefore prevents the absorption of water. This will affect the amount of stormwater runoff in the area. The city center is defined to have ≥ 25% impervious surface area, while the periphery has less.[1]
Periphery of City
In the peripheral parts of the city, Terrascope Class of 2024 will look into the potential of transforming abandoned buildings into green spaces, with an emphasis on community rain gardens. For the large plots of devalued lands, we recommend developing them into a park with trails and native plants. However, since this proposal is focused on small scale green infrastructure projects, this topic is outside the scope of the Adaptive Landscaping team’s implementation plan. The group will first evaluate based on the criteria set in the demolition article to determine whether or not an abandoned building will be demolished. In the case where a building is demolished, the land will need to be assessed for contamination before we build upon it. If contamination is found in the soil, bioremediation would be required. After the land has been cleared, it will provide ample space for a community rain garden. The ground will also be repaved with permeable pavers, and the surrounding space will be populated with Type 1 trees (since there’s sufficient living space in the garden) and bioswales. (For more information, please refer to our Green Infrastructure Solutions article.) In the case where a building is not demolished, the group will focus on adding green roofs (extensive for residential and blue-green for commercial) and green walls to the buildings themselves. Additionally, revamping the surrounding area with permeable pavement, Type 2 trees (since there’s less living space here), bioswales, and small-scale rain gardens. Again, these green infrastructures will only be implemented after the group ensures that the soil is clean.
City Center
In city centers, the group recognized the challenge in completely transforming abandoned sites into rain gardens. Since the land value in urban centers is usually very high, there would be more incentive to construct a new building on the reclaimed land than transforming it into a green space. As a result, our plan is to focus on adding small green infrastructure (e.g., permeable pavement, Type 2 trees, bioswales and rain gardens) in the surrounding area of a demolished building, such as the space lining the streets, curbs, and other public spaces. This will also apply to areas near buildings that aren’t demolished. The group plans to set up green roofs and green walls on those buildings as well.
Costs
Looking at the costs can give Terrascope 2024 a better understanding of how the project will be implemented. The costs are split into two parts: demolition and implementation of green infrastructure. The group looked at the different factors that can influence the costs of the project. This helps illustrate the kinds of decisions that will go into the implementation of our plan. After summing up all the costs, the group was able to gain a sense of the scale of our project.
Demolition and Disposal of Wastes
There are many factors that go into determining the total cost of a demolition project. In order to be able to carry out a demolition, a permit is needed from the government (usually the municipality). In the City of Boston, before filing an application for the permit, the group would need to obtain a demolition plan, disconnect all underground utilities, complete pest control work, and obtain approval from the Department of Environmental Protection and the city’s Fire Department, Environmental Services, and Landmarks Commission (which entails that we would need a detailed surveying of the building by a state certified inspector).[2] For this pre-demolition stage, the costs differ drastically based on the location and the size of the building. A large commercial building in a major urban area (such as Boston) can cost as much as $50,000.[3] In the case where hazardous materials, such as asbestos, are found, there would be an additional cost of $2 to $3 per square foot to remove them.[4]
After all the fees are paid, the demolition process begins. Since the type of buildings Terrascope 2024 plans to demolish are buildings that are in extremely poor conditions, we will not be using the deconstruction method (which is where the building is disassembled by hand and parts are salvaged for reuse) even though it is the most environmentally friendly method. However, although we’re not using the demolition method, we will still be able to recycle the wastes at the end of demolition. We plan to use excavators to take down homes and buildings up to 300 feet high.[5] On average, it would cost around $12,000 to demolish a house in the Boston area.[6] As for larger buildings, we will have to resort to the implosion method, which can end up costing hundreds of thousands of dollars.[7],[8]
Lastly, we would have to deal with the disposal of wastes. Around 65% of the construction and demolition, or C&D, wastes (e.g., concrete and steel) will be recycled. The sorting would cost about $10 per ton in Boston.[9] Since most demolition contractors offer reimbursement for salvaged materials, this will help offset the overall cost of the project as well. Some of the wastes will still have to go into landfills. The hauling and landfill fees will add an additional cost of around $140 per ton of debris to the project.[10] It is estimated that demolishing a 2,000 sq. ft. house with a slab foundation will produce around 135 tons of debris.[11] In this case, the recycling costs would be $877.50 and the disposal costs would be $6,615.
| Stage | Costs |
| Pre-demolition | $3,000 |
| Demolition | $12,000 |
| Disposal of Wastes | Recycling: $877.50 Landfill: $6,615 |
| Total | $22,492.50 |
Green Infrastructure
The implementation of green infrastructure generally comes with two costs: installation cost and maintenance cost. Below is a list of the types of green infrastructure we plan on building and their associated costs.
Rain Gardens
For rain gardens, we would need to inspect the soil quality of the land before we plant on it. Generally, soil tests cost about $90.[12] Meanwhile, a percolation test (for evaluating how well the soil absorbs liquid) costs $150, depending on the size of the plot.[13] If the soil is contaminated, bioremediation would be needed. For example, if there is metal contamination, phytoremediation will be used. This would cost up to around $190 for 2,000 square feet of land.[14] Installing a rain garden on a commercial, industrial or institutional site can cost up to $40 per square foot, depending on the complexity of the design, the amount and variety of the landscaping, and how the water is directed into the rain garden.[15] As for maintenance, we estimate to spend around $4 per square foot per year for mulching, weeding, soil tests, etc.
Bioswales
For bioswales between 9 feet and 16 feet wide, the construction cost for a bioswale is around $58 per linear foot in length.[16] The maintenance costs of bioswales include mowing and cleanup tasks. Annual maintenance costs are estimated at $4.31 per linear foot in length.[17]
Green Roofs
Existing roofs need to be inspected prior to installation to ensure that they can support the new structure. This can cost up to $500.[18] Extensive green roofs are the most common in residential homes. Because they don’t require an irrigation system or a tray system to separate the plants from the structure beneath, their installation and maintenance costs would be at the lower end ($15 per square foot to install and $0.75 per square foot annually for maintenance). As for commercial buildings with concrete roofs, irrigation and tray systems are required, so the overall installation and maintenance costs would be at the upper end. Since the goal of our project is to capture stormwater, the best type of green roofs would be the blue-green roofs that are designed for rain storage in cities. They will go above the commercial buildings with concrete roofs. They cost around $30 per square foot to install and $1.50 per square foot annually for maintenance.
Trees
The total preparation, unloading and planting costs in Massachusetts is up to $11.01 per tree.[19] As for maintenance, we are expecting to spend up to $6.84 per tree annually.[20]
Green Walls
Every green wall needs to be custom designed based on the available space and location of the wall. The cost of installing the initial panel system is around $1,000.[21] For a typical 20 by 20 inch panel, the planting cost is around $400, depending on the plants used and their design. Green walls require high maintenance; they need to be fertilized every two weeks and pruned occasionally. This can cost $300 to as much as $1,000 a month. In addition, the plants on the panels need to be replaced every six months.
Permeable Pavement
The most common materials used are porous asphalt and pervious concrete. The typical installation cost for permeable pavement is about $1 per square foot for porous asphalt and $5 per square foot for pervious concrete.[22] However, custom or high end materials can cost more. Maintenance cost would cover vacuuming of the pavement to prevent clogging. This would cost $400 to $500 per year for three to four times of vacuuming in a half-acre parking lot, which is approximately $0.02 per square foot.[23]
| Type of Green infrastructure | Installation Costs | Maintenance Costs |
| Rain Gardens | Soil tests: $90 Percolation test: $150 Bioremediation: $0.09 per square ft Installation: $40 per square ft | $4 per square ft |
| Bioswales | Installation: $58 per linear ft (9 ft-16 ft wide) | $4.31 per linear ft |
| Green Roofs | Inspection: $500 Installation: $15 per square ft (extensive), $30 per square ft (blue-green) | $0.75 to $1.50 per square ft |
| Trees | Installation: $11.01 per tree | $6.84 per tree |
| Permeable Pavement | Installation: $1 per square ft (porous asphalt), $5 per square ft (pervious concrete) | $0.02 per square ft |
| Green Walls | Installation: $1,000 Plants: $400 (20×20 in.) | $7,200 |
Estimated Costs
Terrascope 2024 will specifically target the transformations of the six abandoned sites in Boston below. (For more information, please refer to our Time Investment article.)
21 Custer St, Jamaica Plain, MA 02130
City center – no demolition
Lot size: 6935 sq ft [24]
| Stage / Type of Green Infrastructure | Costs | |
| Rain Gardens | $306,004.15 | |
| Bioswale (12 ft wide) | $36,010 | |
| Trees | $825 | |
| Permeable Pavement | $20,943.70 | |
| Green Roofs | $218,952.50 | |
| Green Walls | $8,600 | |
| Total | $591,335.35 |
5 Boynton St, Jamaica Plain, MA 02130
City center – no demolition
Lot size: 2605 sq ft [25]
| Stage / Type of Green Infrastructure | Costs |
| Rain Gardens | $115,094.45 |
| Bioswale (12 ft wide) | $13,526 |
| Trees | $310 |
| Permeable Pavement | $7,867.10 |
| Green Roofs | $82,557.50 |
| Green Walls | $8,600 |
| Total | $227,955.05 |
79 Jamaica St, Jamaica Plain, MA 02130
City center – no demolition
Lot size: 3049 sq ft [26]
| Stage / Type of Green Infrastructure | Costs |
| Rain Gardens | $134,670.41 |
| Bioswale (12 ft wide) | $15,832 |
| Trees | $362.83 |
| Permeable Pavement | $9,207.98 |
| Green Roofs | $96,543.50 |
| Green Walls | $8,600 |
| Total | $265,216.72 |
42 Cross St, Boston, MA 02113
City center – no demolition
Lot size: 2600 sq ft [27]
| Stage / Type of Green Infrastructure | Costs |
| Rain Gardens | $114,874 |
| Bioswale (12 ft wide) | $13,500.50 |
| Trees | $309.40 |
| Permeable Pavement | $7,852 |
| Green Roofs | $82,400 |
| Green Walls | $8,600 |
| Total | $227,535.90 |
90 Commercial Wharf, Boston, MA 02110
City center – no demolition
Lot size: ~2000 sq ft [28]
| Stage / Type of Green Infrastructure | Costs |
| Rain Gardens | $88,420 |
| Bioswale (12 ft wide) | $10,385 |
| Trees | $238 |
| Permeable Pavement | $6,040 |
| Green Roofs | $63,500 |
| Green Walls | $8,600 |
| Total | $177,183 |
167 Centre St, Boston, MA 02119
Periphery – demolition
Lot size: 97,946 sq ft [29]
| Stage / Type of Green Infrastructure | Costs |
| Demolition | $1,101,525.20 |
| Rain Gardens | $4,318,679.14 |
| Bioswale (12 ft wide) | $508,584.60 |
| Trees | $11,655.57 |
| Permeable Pavement | $295,796.92 |
| Total | $6,236,241.43 |
Final Total Cost Estimate: $7,725,467.45