Kakaako Waterfront Park has a reputation as a giant, uninviting grassy mound with crumbly walking paths and shade pavilions popular with the homeless. But the state’s biggest park in urban Honolulu would become a grand public recreation destination under a new master plan.

The ambitious state plan published Monday calls for leveling much of the land to create an ocean view from Ala Moana Boulevard and adding attractions that include sand volleyball courts, a gym, children’s play structures, food concessions, a beer garden and an amphitheater rivaling the Waikiki Shell but with a seaside backdrop.

A coconut grove, a water feature, a food-truck court, more restrooms and decentralized parking are also part of the vision for the 47-acre park complex, which reaches Ala Moana Boulevard.

In short, the state aims to transform the somewhat stale and static park, which was built in 1992 to cover a municipal landfill, into a public asset “akin to the world’s best urban parks.”

Carrying out the plan, however, won’t be easy.

The Hawaii Community Development Authority, a state agency that produced the plan with help from local planning firm PBR Hawaii, estimated the project will cost $44.5 million and take 20 years to complete.

“It is an ambitious plan,” said Deepak Neupane, the agency’s director of planning and development.

HCDA projects the additions will generate a modest income to help pay for the work.

The agency projects that $5.7 million in annual revenue can be derived from the food trucks, beer garden, amphitheater and a sports complex with sand volleyball courts, bleachers, a gym and parking. That would cover an estimated $5.3 million in operating expenses and leave a roughly $400,000 annual profit.

Part of the impetus for creating the plan has to do with a lack of resources to maintain the park. HCDA, which developed the park, once owned several large neighboring commercial parcels including a paid parking lot, an office building and a restaurant that the state Legislature gave to the Office of Hawaiian Affairs in 2012. Those parcels previously generated income that HCDA used for park upkeep.

Another impetus was recognizing that the park is fairly unattractive and underused in an area undergoing a population boom as more and more condominium towers rise in Kakaako.

HCDA said the park plus Kewalo Basin Park total 53 acres and represent roughly 90 percent of the public park space in Kakaako. That excludes the city’s Ala Moana Beach park, which is just outside Kakaako and covers about 100 acres including Magic Island.

In recent years HCDA has entertained proposals from private organizations to lease portions of the park for commercial activities but declined the overtures after receiving negative public response that a public asset would be used only by businesses and their paid customers.

Some people are now concerned about whether aspects of the park’s improvement plan would do the same thing.

Neupane said it’s possible that some financing for pieces of the plan might be done in a private-public partnership. Still, PBR, the planning firm, said proposed uses, including the sand volleyball courts, would not be exclusive or restricted.

Michelle Matson, president of the Oahu Island Parks Conservancy, said she has a serious concern about whether the sports areas would be restricted to paying customers.

Matson was otherwise generally supportive of the plan. She called the amphitheater, with lawn seating rising away from an oceanfront stage, spectacular.

“I think the beer garden is going to be very popular,” she added.

HCDA’s plan said the beer garden could function as a satellite, open-air “taproom” for any of Hawaii’s growing breweries or craft beer purveyors.

Matson also endorsed what HCDA envisions as the “great lawn,” which would include new green space in place of the park’s existing parking lot. There are about 500 parking spaces in and near the waterfront park that would be replaced largely on two sides of the park. Another 500 stalls could be part of the sports complex.

Other pieces of the plan include a “beach hale” near the Point Panic and Kewalos surf breaks that could include surfboard storage and maybe a food concession; turning a small existing amphitheater into a grass hill sliding area and possibly rock climbing features or rope courses; and extending a promenade at Kewalo Basin Park so it connects with Ala Moana Beach park.

One uncertain and potentially expensive piece of the plan is cutting down much of the landfill berm, which rises up to 50 feet, so that a clear view to the ocean is possible from Ala Moana Boulevard.

Element Environmental LLC said in a report that landfill material could be used to grade other parts of the project and deposited at an operating Oahu landfill. However, the company said there are risks that the material could be deemed hazardous because details about the landfill’s configuration and buried materials are not recorded.

“The environmental condition of the landfill, in its current configuration, has not been characterized; therefore, current and future risks cannot be adequately evaluated,” the report said.

Element Environmental said it would be cost-prohibitive to remove and ship hazardous waste to a qualified disposal facility on the mainland.

The landfill operated from 1930 to 1977 and mainly contained ash from burned municipal waste and unburned rubbish. Other items suspected of being deposited in the landfill include construction debris, drums of unknown liquids and automobile batteries, the report said.

The landfill was topped with three layers of material including soil and an impermeable membrane when HCDA built the park. A system to collect gas, particularly methane that is still produced, also was installed.

HCDA said re-contouring the landfill mounds is the primary unresolved issue in its plan.

To proceed, the agency will need a variety of approvals, including two from the state Department of Health. A special management area permit also is needed, and HCDA will have to amend its Kakaako Makai Area Plan in a process involving public hearings.

The public may comment through June 22 on the environmental report. For information on how to comment, call the HCDA at 594-0300.