City construction caused a crack or leak in sewer system causing property issues. What do I do?

The first thing is obvious- keep regular photos and document the damage.

Report to your Condo Manager, who should at least put this issue on a Board Meeting Agenda for a vote or consideration of Condo members.  Report to your the City Commission, and the Department that caused the damage.  And see if you can get local paper to do some reporting.  

Since its nor "your" property, you likely do not have standing to sue directly, but te Condo should take action of its impacting the Condo's property. 

This is an unfortunately common scenario when municipal utility work occurs adjacent to condominium property, and I'm sorry you're dealing with unresolved sewage gas exposure, which can pose real health and habitability concerns.

Generally speaking, two separate avenues of potential responsibility may exist here, and they are not mutually exclusive.

First, as to the condominium association: under Florida law, associations are typically responsible for maintaining, repairing, and replacing the common elements of the building. Shared plumbing components — including vent branches that serve more than one unit — are often classified as common elements under the declaration of condominium (the governing document that defines what the association maintains versus what unit owners maintain). If the damaged vent branch is a common element, the association generally cannot avoid its maintenance and repair obligation simply because a third party caused the damage. Florida courts have recognized that an association's statutory duty to maintain the common elements is what is called "non-delegable," meaning the association remains responsible to unit owners even when the underlying cause originated elsewhere. The association may have its own claim against the responsible party, but that is generally the association's problem to pursue — not a reason to leave an owner exposed to sewage gases.

Second, as to the City of Venice: municipalities in Florida can be held liable for property damage caused by negligent construction work, though claims against government entities involve special procedural requirements. Florida's sovereign immunity statute requires written pre-suit notice to the government entity within a specific timeframe, and there are caps on recoverable damages. These deadlines are strict, so time matters. If the City used a private contractor for the lift station project, the contractor may also bear responsibility, and claims against private contractors may not be subject to the same sovereign immunity limitations.

Practical steps owners in this situation often consider include: reviewing the declaration of condominium to determine whether the vent branch is a common element or part of the unit; documenting the damage and conditions in writing (photos, plumber reports, air quality concerns); making a written demand on the association identifying the specific maintenance obligation; and requesting the City's project records, which are generally available through a public records request.

Because your situation involves overlapping claims, governing documents, and government pre-suit notice deadlines, I would strongly encourage you to consult a Florida attorney experienced in condominium and construction-damage litigation promptly so your rights are evaluated and preserved. Please note this is general legal information, not legal advice, and no attorney-client relationship is created by this response.