Greenfield Partners wants to add a third level to its parking structure on Wilton Road. The expansion would increase the deck's parking capacity to 130 spaces from its current total of 97.

Adding the third story would raise the facility's height from approximately 15 feet to 24 feet, according William Fitzpatrick, the lawyer for Greenfield Partners. The revamp of the parking deck would also include building new stairs, a ramp to the third level and reconfiguring the plantings in front.

The proposed parking deck expansion has received conditional approval from the Flood and Erosion Control Board. The plan also was approved by the Architectural Review Board, Fitzpatrick said.

Other town boards will scrutinize Greenfield's proposal during the next few weeks. The Conservation Commission will review the plan on Wednesday, while the Zoning Board of Appeals on Jan. 24 has scheduled a hearing on the application from Greenfield for variances related to setback requirements. The proposed expansion would also require site plan approval from the Planning and Zoning Commission.

"My client is excited to work with all of the town boards," Fitzpatrick said. "We're proud of this proposal, and we're looking forward to moving ahead with this process."

The parking deck expansion is one part of Greenfield's plan to redevelop a group of buildings that it owns on the west bank of the Saugatuck River in the town center. The landmark National Hall anchors that complex, and Greenfield plans to move its corporate headquarters to the site.

Greenfield Partners intends to seek the requisite approvals for the parking deck addition before submitting a site plan for National Hall to the P&Z Commission, Fitzpatrick said.

Last October, the P&Z approved a text amendment proposed by Greenfield that allows more office space in the Historic Design District where National Hall District is located. In January 2010, the Representative Town Meeting had overturned a similar text amendment presented by Greenfield.

The Wilton Road structure would provide parking for workers at National Hall and also serve patrons of several restaurants that Greenfield plans to bring to other buildings in the complex, Fitzpatrick said. Increasing the parking structure's capacity would not overburden nearby thoroughfares such as Wilton Road, Post Road West and Riverside Avenue, he added.

"The benefit of the parking is that it will be used at different times throughout the day," Fitzpatrick said. "The peak demand for parking from office workers will not be the same time as the peak demand for restaurant patrons."

To accompany its application for the parking deck expansion, Greenfield Partners will hire a traffic engineer to produce a traffic report for the area surrounding the parking structure, Fitzpatrick said.

The Conservation Commission's review of Greenfield's proposed parking deck expansion is scheduled for a public hearing at 6:45 p.m. Wednesday in the Town Hall auditorium.