ANN ARBOR, MI – Turning the surface of Library Lane’s underground parking lot in downtown Ann Arbor into green space would be expensive and difficult, according to the Downtown Development Authority.
Maura Thomson, acting director of the DDA, offered the DDA’s perspective, based on what engineering consultants advised, at a meeting of the city’s Council of Municipalities on July 7.
The $ 50 million parking lot off Fifth Avenue was built by the DDA ten years ago. It was designed to support a building on top, not a park, Thomson said.
Modernization at this point presents many challenges “and it would be quite expensive,” she told the citizen-led advisory body appointed by city council to help plan a central park downtown.
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The library lot – the above ground parking lot next to the downtown library – is the roof of the underground bridge, and any damage or removal of the surface coating would void the bridge’s waterproof warranty, said Thomson, discussing challenges of adding trees, for example. .
“I don’t think filling it with dirt – you know, like trying to plant grass and trees and have it like a traditional type park, I don’t think the structure can adapt to that. “she said.
Any potential changes to the structure should be assessed for any impacts it might have on the parking lot, she said.
The tree pits currently part of the parking lot landscaping were strategically placed for load purposes during the construction of the bridge, Thomson said, noting that each square pit is five feet wide and four feet deep. . Adding more trees with this depth of soil could exceed the carrying capacity of the bridge and this needs to be evaluated, she said.
“And tree pits also collect rainwater, just like all plant beds,” she said. “There are also underground drains under the paved areas, but they are not sufficient to collect an increase in stormwater if the pavement had to be removed. “
The community debate on transforming the park from the library to an urban park has been going on for many years. Some argue that Liberty Plaza, located in the same block, already functions as an urban park, and not without its fair share of challenges, while the University of Michigan Diag offers a large grassy area filled with trees in the middle of downtown. -city.
But some still have hopes of seeing something along the lines of a town square with some greenery on the library lot.
Before voters approved the Central Park voting proposal initiated by citizens in 2018, the city had agreed to sell the library lot to a Chicago developer for $ 10 million to allow for a 17-year-old skyscraper. floors and a developer-funded plaza, but voters stopped that. plan.
Erica Briggs, City Council Liaison Officer to the Council of Commons, thanked Thomson for the information she shared. But regarding concerns about any puncturing of the concrete surface voiding the bridge’s waterproof warranty, Briggs asked how this was going to be handled with the previous high-rise plan.
“It is clear that the site was intended for redevelopment, so there was a plan in place for that to happen,” Thomson said, adding that she did not know the details. “But what I would suggest is that once you’ve developed plans, we can have those plans evaluated by our engineering company.”
Alice Ralph, a member of the Council of Commons, argued that it would be putting “the cart before the horse” if the group came up with a plan before they learned more about what is technically possible.
“We don’t spend $ 40,000, for example, on a plan in the hope that it could be destroyed because we didn’t know or couldn’t know what the boundaries of the site were, so I still see this conflict in it. run, “she said.
Ralph has stated that she personally dislikes the grass, especially for an urban park, but a patch here and there might be desired.
Council of Commons member Rita Mitchell asked if the DDA could provide more information on where on the ground there is more structural support to add certain elements.
“I have no idea what we’ll put on, but that would be pretty cool to know,” she said.
City administrator Tom Crawford said the city wanted answers to the group’s questions. From an engineering perspective, problems can be fixed with time and money, he said.
Adam Zemke, chairman of the Council of Commons, said it would be helpful for the city to share more detailed information on previous skyscraper development plans, showing how the surface was going to be changed.
“One of the disconnections in my head is trying to figure out what the city was willing to do before and what we’re hearing now,” he said.
The DDA looked for examples of parks built on top of underground parking lots and found Midtown Park in Houston, Texas, but this bridge was designed to accommodate the green space above and the design challenges were resolved before construction, Thomson said.
“They specifically note that there was a real need for a collaborative and integrated design approach, so they have trees that were strategically placed, extensive waterproofing measures were taken, a deep layer of soil was placed. on the concrete slab, then a complex system of drains under the slab were installed, ”she said.
For Midtown Park in Houston, the parking lot and base park footprint cost $ 40 million, and there was a separate $ 8 million fundraising campaign to raise money for park amenities, including water features and art, said Thomson.
“I don’t know how much they collected, but that was the goal for the items they wanted to see in the park,” she said.
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When it comes to planning for Ann Arbor Central Park, the DDA’s top priority is to maintain the structural integrity of the parking lot, Thomson said. The DDA manages the city’s public parking system, including terraces and grounds.
“There are just limits to what can be done on the ground on the surface and we cannot compromise the integrity of the structure,” said Thomson.
The DDA also has an obligation to maintain safe and unhindered access to the parking lot for customers, she said.
As it sits next to the downtown library, security is another issue and it’s important to make sure library patrons feel safe to and from the area, Thomson said.
Who would be responsible for garbage and snow removal and general cleanup is another consideration, she said.
The DDA is developing a memorandum of understanding with the city for the short-term activation of the space to allow the temporary removal of parking on the surface lot while longer-term plans to create a park are explored by the Council of Commons, said Thomson. .
The DDA would still maintain parts of the library lot, including lighting, during the period of short-term activation, but vehicle entry and exit doors would be removed and would have to be replaced with barriers, a she declared.
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There have been questions about access to water for the site, Thomson said, noting that there is no tap on the ground above ground, but there is access to the site. water in a mechanical room on the first underground level of the garage on the Division Street side. And there is a landscaped irrigation system that extends from the mechanical room to the planters in the library lot.
In addition to a water fountain and public toilets, ideas for the space expressed by community members included a large water fountain as a visual element and a play area.
Regarding access to electricity when there are events, there is an outlet near the main elevator lobby on the library lot and an overhead extension could come out of it, Thomson said, noting that the Fifth Avenue light poles also have outlets.
Council of Commons member Sara Hammerschmidt asked if the DDA was interested in partnering for the operation, maintenance and future activities on the library lot.
“We don’t have the staff or the equipment at all to get involved in this,” said Thomson. “I mean, we have no appetite for this.”
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