About 400 trees will be removed to make way for a housing project in Eden Prairie that environmental activists fear will destroy a nearby spring and Riley Creek after the watershed district board narrowly approved the permit Thursday.

The green light from the Riley Purgatory Bluff Creek Watershed District Board came on the heels of city officials signing off on the Noble Hill project of 50 single-family homes to be built by developer Pulte Homes on a Christmas tree farm.

The nearly 28-acre farm has been owned by John and Carol Standal for 44 years. They said they always intended the land to be developed, but the family and the developer have faced strong opposition all summer.

Details of the land sale haven't been disclosed, but the Standals are donating a third of the property to Eden Prairie to be preserved as a natural area around Riley Creek and the Fredrick Miller Spring.

"We've been through hell," said a relieved Carol Standal following the watershed vote. "We've been there for so long and now is the time to sell."

Standal, 72, said activists who believe the development will damage the spring and creek have made the family so fearful that she couldn't stay at her Eden Prairie home when visiting from Florida, where she said her husband is dying in a nursing home.

"This group has threatened me. They have shamed our family. They have attacked my neighbor. They have followed me and tracked me down," she said.

Chesney Engquist, president of the Spring Valley Friends, denied the environmental group had threatened Standal. But the group did submit a petition with 3,000 signatures seeking an Environmental Assessment Worksheet (EAW) for the project with the Minnesota Environmental Quality Board.

City spokeswoman Joyce Lorenz said the quality board left the EAW request up to the city, which the council denied before approving the project, subject to the watershed district's vote.

Spring Valley Friends members have challenged the EAW dismissal. But Eden Prairie City Attorney John Baker said the challenge was thrown out last week by the Minnesota Court of Appeals. Plaintiffs have filed a petition with the state Supreme Court, which will decide whether to review the lower court decision by the end of September.

"Nothing has happened in the case to have kept the parties, the city and [Pulte Homes] from moving forward," Baker said.

Officials with Pulte Homes did not respond to requests for comment. The company applied last winter to build the project, and pending all remaining approvals will begin construction on Noble Hill this year.

Activists say the proposed development is in the midst of a rich ecosystem with endangered species and sandy bluffs susceptible to erosion. New signage from the city near the spring, alongside walking paths of silty soil, acknowledge that the area is rare: "You are overlooking one of the few remaining undisturbed prairies in our region."

Eden Prairie residents in 2015 expressed concern about erosion on Purgatory Creek that threatened homeowners with sinkholes and mudslides. Since then, people frequenting the spring have observed collapsed banks and bridges, raising worries about how much more development the watershed can take before the spring runs out.

Susu Jeffrey, of Minneapolis, who has been fighting to save Minnesota's natural springs for decades, was among a half-dozen residents and activists who addressed the watershed board at recent meetings. They asked the board to allow University of Minnesota civil engineer professor Otto Strack to review the data from a slope stability study.

"If we don't have water, we'll die," Jeffrey said. "One drop becomes a wave."

In his written analysis, Strack told the board that the study inadequately addressed "the dynamics resulting from sudden intense rainstorm events that are a frequent occurrence today." He added that "the complexity and importance of the Noble Hill development warrants the extra effort to carry out a rigorous analysis of the stability of the slopes involved."

Dean Lotter with Pulte Homes told the watershed board that he and the Standals were frustrated with the delays and calls for more review when the city engineer and companies hired by the city had signed off on the project.

Larry Koch, one of the watershed district managers, urged the board to follow Strack's recommendations. "I wholly object to approving this permit at this point," said Koch, who was joined by manager Jill Crafton. "This is such an important project … and it involves a lot of concerns from the public."

But the district's other three managers voted to move ahead with the project because it met industry standards.

Manager Dorothy Pedersen said that while she is "an environmentalist at heart," she had to approve the permit.

"If there was some way that the rules were tougher, that I could say this was a site that needed to be protected, I would be voting that way," she said.

Kim Hyatt • 612-673-4751