The City of Ottawa has hit a snag in its plans to redevelop Lansdowne Park.

The Ontario Heritage Trust has written to the city, expressing concerns about how the Horticulture Building on the property will be impacted.

The adjacent Aberdeen Pavilion is already under what's known as a conservation easement, so any alteration to that building or its sightlines needs the approval of the trust.

The OHT says it will seek similar protection for the Horticulture Building, and warns the city to leave the structure where it is.

Three of the five design concepts unveiled last week would move the building to make way for a commercial complex.

In a memo to council, city manager Kent Kirkpatrick said staff will clarify the OHT's concerns and discuss how to address them.

The five design proposals are part of a competition focusing on the section of the park bordering the Rideau Canal, toward the southeast. The competition area does not include the northwest section of the park along Bank Street.

City council voted last November to start negotiating a private-public partnership with the Ottawa Sports and Entertainment Group to redevelop Lansdowne Park.

The controversial development plan includes construction of a cluster of shops, cinemas, condominiums and townhouses, and the revamping of the existing stadium.

The price tags for the designs range from $33 million to $88 million. The city has allocated $5 million for the first phase, but one team estimated that asphalt removal alone would cost $1.3 million.

A seven-member jury led by urban designer George Dark will pick the winning concept on June 4. The design will then have to be approved by city council, the National Capital Commission and Parks Canada.