St. Paul's Midway Stadium sits on top of several feet of horse manure and that could be a costly problem for developers interested in building on the site, the Pioneer Press reports.
For decades, the land was used as a dumping ground from the state fairgrounds before the Saints ballpark was built in the early 1980s.
"One of the things that was dumped there was horse manure," St. Paul Port Authority President Louis Jambois told the newspaper. "And horse manure doesn't turn into good dirt. It turns into methane and some solids."
If possible, the debris would have to be removed to build on or crews will have to sink deep pillars into bedrock, according to the Pioneer Press. Either way, it will add at least $3 million and as much as $5 million.
The Saints are slated to start playing at their new $54-million Lowertown ballpark in the spring of 2015.