Sitting on the Diamond Head bank of Kapalama Canal, Mayor Kirk Caldwell signed a bill Wednesday that adds more pressure on the persistent homeless encampment by making it illegal to put anything into the already fetid and littered drainage canal.

More than 30 homeless tents and tarps went back up Wednesday just 24 hours after a city crew cleaned up the encampment.

Caldwell and Ross Sasamura, director and chief engineer of the city Department of Facility Maintenance, also announced that a 4-foot-high, mile-long chain-link fence will be erected on both sides of the canal between Olomea Street and Kalani Street by the end of the year.

The $240,000 fence project will be put out to bid and the winning contractor will have 90 days to install it, Sasamura said. While keeping out campsites along the canal, the fence also will mean that dozens of vehicles will no longer be able to park on the Diamond Head side of Kapalama Canal directly across Kokea Street from Honolulu Community College.

Caldwell’s signature on City Council Bill 46 means “anything other than rainwater is illegal” in Kapalama Canal, Sasamura said.

On Tuesday, city crews were pulling from the canal pallets and other materials left by homeless people.

The new law applies to any human activity along any city stream, drainage canal or river, but clearly is aimed at the high-profile Kapalama Canal homeless encampment in Kalihi.

Each violation is a petty misdemeanor, punishable by up to 30 days in jail and a $1,000 fine.

On Tuesday, following a 24-hour notice that the area would be swept, more than two dozen homeless people cleared out as the city’s enforcement team moved along the canal and picked up dozens of discarded pallets used as structures, along with garbage and debris.

The enforcement team costs the city $15,000 a week in salary and operational costs, Sasamura said, and collects 5 to 8 tons of homeless belongings in an average week.

By Wednesday morning, however, there were even more tents and tarps back along the newly cleaned ewa-side canal bank than in the days before the sweep was announced, providing a backdrop to Caldwell’s press conference.

Then with a second signature Wednesday, Caldwell vetoed an expansion of the city’s “sit-lie” ban, saying it would not survive a court challenge because it could not be proved to protect business interests. Further, Caldwell said the bill could jeopardize the city’s efforts to clamp down on homeless encampments.

Unlike the city’s current sit-lie bans in Waikiki, Chinatown and downtown, the proposed expansion of the law to College Walk Mall, Kila Kalikimaka Mall, Union Mall and Fort Street Mall would not occur during business hours — or in some cases would not even apply to business areas, Caldwell said.

In a letter to the City Council, Caldwell reiterated that the Department of Corporation Counsel said Bill 44 “contains legal deficiencies” that “make it more likely that the city will be subjected to unnecessary legal challenges” that could result in taxpayers picking up the costs for challengers’ legal fees.

Caldwell said he was “gravely concerned” that a successful court challenge to Bill 44 could also lead to the dismantling of city policies that work, such as clearing out illegal structures on city sidewalks that occurs every day.

City Council Chairman Ernie Martin said he is inclined to place Caldwell’s veto on the agenda of the September Council meeting for an override vote, although he wants to first speak with the bill’s author, Councilwoman Carol Fukunaga.

“More than any other member on the Council, her district has really been overwhelmed by this particular issue,” Martin said. “She’s been very diligent in seeking potential solutions to this (homeless) issue, not just expanding the sit-lie measure.”

Martin said he expects there would be the six votes needed to override Caldwell’s veto, because the bill passed 7-2.

He said he was disappointed that Caldwell has spoken repeatedly about cooperating with the Council, but “he made no attempt to either contact the member of the district or the subject matter chair of the (Zoning and Planning) committee prior to exercising his veto.”

Martin added: “He cannot … ask us to accept everything he proposes to the Council and then contrastingly reject everything the Council offers to him.”

Fukunaga, who introduced Bill 44, said it’s clear to her that the office buildings abutting College Walk Mall and Kila Kalikimaka Mall are businesses that are affected by the homeless.

“I can appreciate where those business people have been coming from,” Fukunaga said. “They totally believe in housing people. It’s just that if they’re going to be vandalizing or otherwise impacting their operations, they gotta worry about how they stay afloat.”

City attorneys have argued that the sit-lie law cannot apply at College Walk Mall and Kila Kalikimaka Mall because they are not in areas zoned for business use.

Fukunaga argues they are part of a commercial area.

Councilman Joey Manahan, who introduced the bill related to streams, canals and rivers, expressed satisfaction that Caldwell signed it into law.

Manahan said he introduced the bill after Caldwell’s veto of Bill 6 called into question the constitutionality of applying the sit-lie law along streams and rivers.

Manahan also applauded the administration for planning to fence Kapalama Canal.