A memorial park "would honor and remember the six dead while providing a reflective and calming oasis in the center of a dense business district," Nancy Winkler, Bryan's mother and cochair of the committee, said in a statement.
Winkler, the city treasurer, created an online petition to promote the proposal in September. It has gathered more than 6,000 signatures.
"The committee recognizes the potential of this relatively small but important memorial park to help individuals and the community heal in the aftermath of this horrific, entirely avoidable event," Winkler said.
A four-story brick wall of a building being demolished at 2138 Market St. crashed on top of the one-story Salvation Army store next door, killing four shoppers and two employees.
The Salvation Army owned the building that housed its store. Much of the rest of the block is controlled by developer Richard Basciano through the company STB Investments.
A chain-link fence now cordons off the site.
John White, a committee cochair and chairman of PFM Group, a municipal investment advisory firm, said the group hopes to work with the city and Salvation Army "to find an approach to permanently restrict development on the site so that a memorial park is forever dedicated to memorializing the victims and the memory of the event."
Mayor Nutter, he said, is "fully supportive" and has assigned Deputy Mayor Michael DiBerardinis to serve as liaison to the group.
Thomas Decker, a committee member and vice chairman of Cozen O'Connor law firm, said the group has reached out to the Salvation Army about a temporary memorial park.
"We've asked them to join with the committee to do something on a temporary basis," Decker said.
Eric Weiss, an attorney representing the Salvation Army, said in statement issued Wednesday morning that the organization had "received a communication from the Memorial Committee and is in the process of addressing numerous community needs arising out of the Market Street tragedy."
" When all the concerns and options are weighed, it is The Salvation Army's intent to continue to provide assistance and support for those in need, which includes those impacted by the events of June 5, 2013," he said. "At this moment in time no decisions have been made but The Salvation Army will respond as the path to fulfill its Charitable Mission becomes clear."
The Pennsylvania Horticultural Society has established a tax-exempt fund for the public to make contributions for the memorial park.
Online donations may be made at www.pennhort.net/memorial.