It’s a detail that may have slipped some voters’ minds, but the Bend Park & Recreation District has said from the beginning that while all property owners will pick up the tab for the basics covered by its bond measure approved last fall, donors will provide the money to bring several projects in the measure to fulfillment.

Thus the Bend Paddle Trail Alliance likely will raise money for completion of the proposed whitewater park on the Deschutes at the Colorado Avenue bridge; skateboarders and pickleball players will be expected to add funds for new facilities for their sports, and soccer groups will contribute for more soccer fields.

That’s not a new approach for the district. Sports groups have long helped shape and pay for facilities that their members want to use, and there is no reason to stop now.

What there is reason to do, however, is to spell out as carefully and in as much detail as possible the relationship between private contributors and the public park district itself.

One need only think about the current tensions between the district and the United Senior Citizens of Bend to understand how critical that is. The district and the seniors have been at odds for months over just who agreed to what when the two came together to build the district’s Senior Center on Reed Market Road.

The seniors’ group contributed money to that project and moved into the center when it opened in 2001. Things worked well for a time, but, dissatisfied with changes in the way the center was being run, the group moved out in 2011.

The seniors believe the agreement has been breached; the district argues that changing needs among its patrons have dictated changes in programs at the center, changes it has always had the right to make.

Going into a series of new agreements with new groups, district officials should keep their problems with United Senior Citizens in front of them. A good agreement is one that makes clear the obligations and expectations of all parties to it.