The city is moving forward on plans to shore up a portion of the crumbling sea wall that protects Kapiolani Park between the Queen’s Surf groin and the Waikiki Aquarium.

Waves attack the sea wall, topping the structure and pooling water behind it, according to a recent report.

The city portion of the sea wall, which last underwent major repairs in 1987, has problems with its foundation, damage to its concrete cap, missing and loose rocks, and cracks in its retaining walls, the report said. Repairing the wall could cost $1.8 to $3.1 million.

Honolulu engineering company Oceanit, the city’s consultant, said in a draft environmental assessment (which can be viewed at 808ne.ws/Queenssurfseawall) that the sea wall’s mass and multiple repairs have kept it from collapsing so far. However, more extensive repairs are needed to keep it from collapsing, the report said.

“Failure of the sea wall will result in extreme erosion of land side back fill, runoff into the ocean, potential damage to the promenade and increase the likelihood of accidents and injuries,” Oceanit said.

Oceanit recommends that the city spend approximately $2 million to repair the sea wall by adding a form-lined concrete wall on the makai side and concrete support on the land side. Three other Oceanit proposals up for review range from various sea wall repairs to replacing a 460-foot stretch of the wall:

>> The least expensive option would cost nearly $1.81 million to repair the sea wall by adding rock revetment at its base and installing concrete support on its land side.

>> Another option, repairing the sea wall with permeation grouting and soil reinforcements, would cost just over $1.84 million.

>> Reconstructing the sea wall and adding soil reinforcement would cost $3.1 million.

The city Department of Design and Construction said in the draft that it anticipates a finding of no significant environmental impacts. A 30-day public-comment period follows the assessment’s Thursday publication in the state Department of Health’s Environmental Notice.

According to the draft, serious defects in different parts of the wall were detected during field investigations in 2015 and 2016 and geotechnical explorations in 2011 and 2014.

Oceanit said its recommended alternative could drain water from overtopping waves and stormwater runoff. The additional wall, which would blend with the current structure, could be anchored to the concrete along the land side of the sea wall or supported by vertical reinforcing bars embedded near the foundation.

Oceanit’s scope included a 900-foot section of the 1,270-foot sea wall between the Queen’s Surf Groin and the Waikiki Aquarium. A crumbling 370-foot section fronting the Waikiki Natatorium was not included because it falls under state jurisdiction.

The state and the Waikiki Beach Improvement District Association are exploring alternatives for beach improvements in Waikiki, including the Queen’s Surf area, said Sam Lemmo, administrator for the state Department of Land and Natural Resources’ Office of Conservation and Coastal Lands, in a letter to Oceanit included in the draft.

“We invite the city and concerned stakeholders to join this new effort to develop more stable and resilient beach configurations at Waikiki while limiting environmental impacts,” Lemmo said. “Over the coming decades, climate change and sea level rise will increase the vulnerability of the Waikiki shoreline to erosion and over wash from high waves and high water levels.”