Opposition parties and environmentalists are stepping up calls for a thorough investigation into President Lee Myung-bak’s four-river project after the state auditor reported last week that it was fraught with flaws threatening water quality, ecosystems and biodiversity.

On Thursday, the Board of Audit and Inspection raised safety issues concerning dams constructed in the Han, Geum, Yeongsan and Nakdong rivers due to substantial defects in design and construction, which would incur huge maintenance costs.

“We have to open a full-scale reinvestigation into the four-river project including a parliamentary probe and hearing to expose the government’s exaggeration and distortion of facts and use of expedients, before taking legal action through an independent counsel,” the main opposition Democratic United Party’s floor leader Park Ki-choon told reporters on Sunday at the National Assembly.

Opposition politicians, academics and civic groups banded together to call for the next government to reexamine the 22.3 trillion won ($21.1 billion) project and shift the nation’s water management from a development-oriented policy to eco-friendly one.

The snowballing controversy poses a challenge to President-elect Park Geun-hye. Her transition committee is already grappling with how to finance her grand health and education pledges in the face of economic uncertainties. Park and her Saenuri Party are also blamed for endorsing the costly river project despite persistent environmental concerns.

Launched in April 2009, the multibillion-dollar plan was the centerpiece of Lee’s “low-carbon, green growth vision” designed to harmonize environmental sustainability and economic revitalization.

Dozens of construction and engineering firms took part in dredging some 900 kilometers of main and tributary streams, and installing weirs, dams, disaster prevention facilities, sewage treatment centers, parks and bike paths.

As most of the core subprograms were completed, the government has been trumpeting its effect on water security, flood prevention and job creation in the regions around the four rivers.

But the BAI concluded that the ambitious initiative has barely lived up to expectations.

“Due to faulty designs, 11 out of 16 dams lack durability, water quality is feared to deteriorate, and excessive maintenance costs will be required due to inefficient dredging,” the report said.

With maintenance bills estimated to top 288 billion won annually, the state auditor urged the government to fix urgent defects of weirs and craft a comprehensive guideline to improve water quality and sustainably manage dredging operations and riverside areas.

While Cheong Wa Dae remains mum, Land, Transport and Maritime Affairs Minister Kwon Do-youp and Environmental Minister Yoo Young-sook held a joint news conference on Friday. They refuted that the weirs have no safety or functional problems, calling the BAI report “mistaken.”

“The project had an effect, such as helping the rivers weather through droughts and four typhoons last year,” Kwon said, adding that extra repair work is already under way.

On water quality, Yoo said that mid- and long-term approaches are needed, given other factors such as weather conditions and changes in pollutants.

She also dismissed concerns over the project’s impact on an unusually acute algae outbreak in August in the Han, Nakdong and other rivers. “Algal blooms are a phenomenon that has existed since long before the four-river program.”

Park, Lee’s intra-party archrival who has been trying to distance herself from the unpopular president, appears to be walking a tightrope to contain a possible fallout on her leadership.

The presidential transition committee appears to be trying not to be involved in the controversy. But if the situation is further escalated, it may cave to mounting pressure and back a fact-finding probe, which will likely strain Park’s relationship with the predecessor.

Lee Jung-hyun, a close aide to Park in charge of political affairs, was quoted as saying on Friday that “the current government ought to resolve the people’s anxiety and suspicion.”

Saenuri floor leader Lee Hahn-koo also called for a stringent review and countermeasures.

“The government must clarify whether the problems are true, and present possible solutions,” he said Friday. “Then we will supplement what is needed and provide necessary parliamentary help.”

Though welcoming its latest assessment, opposition lawmakers lashed out at the BAI for flip-flopping on its conclusion at the end of Lee’s presidency. Merely two years ago, it reported “no particular problems” in sharp contrast with independent analyses pointing to environmental degradation.

The project has hit various snags throughout its three-year construction period. Some municipalities boycotted the work. Some scholars warned that a substantial dredging of the riverbed made some areas even more vulnerable to flooding. Other environmental activists staged rallies against a possible endangerment of local wildlife and ecosystem dynamics.

Another blow came in late 2011 when the state-run Korea Research Institute for Human Settlements calculated river maintenance costs at 612.5 billion won for 2012 alone. The Land Ministry rejected it, arguing 163 billion won would suffice.

In February 2012, a Busan high court ruled that renovation work on the Nakdong River was unconstitutional due to the lack of a preliminary feasibility study required for any government program worth 50 billion won or more.

But the judge dismissed the case, saying “rescinding the whole process that is near completion goes against the public good.” The ministry appealed.

Public uproar intensified after the government was found to have funneled a fortune into a massive advertising campaign and lavish events to promote the project and encourage positive reviews.

“The audit results showed the project was a total failure,” said the Citizens’ Coalition for Economic Justice, a civic group, in a statement.

“The National Assembly and next government should first and foremost revamp related laws and institutions to prevent the repeat of such a failure, and the prosecution should hold those involved accountable through a full-fledged probe.”

Despite plunging approval ratings, the outgoing president pushed ahead with his long-fostered plan.

Critics called it a CEO-turned-president’s ambition to grant a cash cow to his old workplace, Hyundai Engineering & Construction, and other builders grappling with a prolonged slump and cutthroat competition in the local property market.

With Lee quickly falling into lame-duck status as his term nears its end, a series of graft and collusion allegations emerged surrounding the related government agencies and companies.

The Fair Trade Commission has sanctioned almost 20 builders for price rigging, while 12 government officials were found by the BAI to have been implicated in six cases involving unfair contracts, illicit bidding and lax inspection.

By Shin Hyon-hee (heeshin@heraldcorp.com)