Northern Virginia’s regional parks authority is proposing to add a new “lazy river,” dog park and community park to the Cameron Run site in exchange for a 40-year lease. Above, Connor Maguder, 24, loads up with tubes in June 2016 to float at the Great Waves Waterpark in Alexandria. (Linda Davidson/The Washington Post)

Northern Virginia’s regional parks authority, which last year faced the potential loss of the highly popular Great Waves Waterpark when Alexandria officials considered not renewing its land lease, is offering to add a new “lazy river,” dog park and community park there in exchange for a 40-year lease.

Paul Gilbert, executive director of Nova Parks, as the authority is known, proposed $7.5 million in improvements at the Cameron Run site in a letter Thursday to the City Council.

“This offers a lot of new users and benefits and long-term investment, and at no cost to the city,” except for the long-term lease, Gilbert said in an interview. “Right now, it’s a great park for the general public and you don’t have to be a member of a league or a team to use it. You can just show up.”

Council members last summer objected to Nova Parks’ previous lease-extension proposal, which the parks authority had tied to the purchase of a historic house in Old Town. The city ended up buying the historic house, using grants from the state’s land conservation foundation, the Virginia Outdoors Foundation and the homeowner.

But the fate of the water park’s lease was unresolved as the city sought public input about the best use of the 26-acre, southwest Alexandria site.

The park authority’s proposal spells out the addition of a “lazy river” pool north of the existing water park entrance, a neighborhood “pocket park” to be built on the east side of the man-made lake, a fenced dog park next to the existing animal shelter, trail additions and improvements and a reconfiguration to the existing parking lot to add more spaces. Within 15 years after those changes are made, the authority said it would redevelop the water play area next to the wave pool. The only existing feature to be removed would be one of the two picnic shelters, Gilbert said.

Mayor Allison Silberberg (D) was reluctant to immediately respond to the proposal, noting that a consultant has been organizing and compiling ideas from the public. That summary will go to the local parks and recreation advisory commission in June or July, along with the proposal by Nova Parks. The commission’s recommendation will go to the council in September.

“It’s an important discussion and it’s ongoing,” Silberberg said. “I want to read through the consultant’s report and hear from the community and the parks department, and consult with colleagues.”

Last year, soccer advocates called for more ballfields, which could be used nearly year-round.

The water park is open only during the summer, drawing about 105,000 people per season. Another 49,000 use the batting cages and 10,000 play mini-golf there throughout the year; uncounted numbers of people fish in the man-made lake and use picnic areas. Great Waves is the authority’s third-biggest revenue-generating site, Gilbert said.

Nova Parks is funded by three cities and three counties, at $4.43 per resident, and anyone from the counties of Fairfax, Arlington and Loudoun, and the cities of Alexandria, Falls Church and Fairfax can use any park. Cameron Run Regional Park users also pay a sliding-rate fee to use the park, with 1,000 free tickets available for youths. In 2015, the entire park netted $506,000 for the nonprofit Nova Parks, money which pays for less-popular sites such as Alexandria’s historic Carlyle House. The city leases the park authority the land for a nominal sum; Gilbert said that since the water park was established, the park authority has invested $10.5 million into the property.

The park authority’s current lease with the city expires in 2021, but if the new proposal wins the council’s favor, it would be canceled and a new 40-year lease would start this year.