There is a plan to stop cruise ships from going into the San Marco basin and down the Giudecca canal. The goal is to accomplish this by 2019. It is called Vittorio Emanuele Project. In the article below is a very interesting (and shocking) video of pictures of Venice taken from a cruise ship, and also some individual pictures in the article that highlight the problem.
http://nuovavenezia.gelocal.it/venez...rco-1.15316597
The title of the article, "Venezia, dal 2019 grandi navi via da San Marco," Until 2019, giant cruise ships will still go by San Marco."
The reason for the 2019 date is that UNESCO has promised sanctions if Venice doesn't have cruise ships out of San Marco by then. It basically involves dredging a the Vittorio Emanuele canal to make it deep enough to handle cruise ships. The problem is it's off of the chemical factory town of Marghera, and the mud there has extremely high levels of toxins, but they say they can do it. A final decision is supposed to be made by June, but there may be an announcement by Minister Franceschini at the Biennale tomorrow.
Notice the picture of the smoke coming out of the cruise ship. There is a european law concerning the amount of sulfur and particulate matter that is allowed to be in a combustion engine if it is within a certain distance from a shoreline. Cruise ships to Venice ignore this law, and use fuel that has 1,500 times the allowable amount of sulfur. To install the proper filters would actually cost the a pittance, but they have refused to do it. A cruise ship going by emits about the same amount of pollution as 15,000 cars. When a cruise ship docks overnight, they cannot turn the engines off because there is not enough power otherwise available to keep the lights on. So it's like having 15,000 cars parked next to the city, running there motors all night. Venice is considering, "hot landings," meaning supplying an electrical energy source to the docks so that the cruise ships can turn off their engines for the night, but this is a long term plan.
Some are more concerned about pollution than the ships passing by San Marco, because the ships will have to travel an extra 20 miles along Venice to get to the docks. in the 1990's Venice had the cleanest air as almost any city in Italy because there are no cars. Since the cruise ship explosion that started in 1999, Venice now ranks up there with Milan, Rome, Torino, and Florence for the worst air pollution, and lung cancer in Venetians is especially high due to the air pollution.
But it seems as if nothing is going to change, at least until 2019. The pictures in the article linked to above are very sobering.