This post has been corrected. See note at the bottom for details.

A second medical marijuana initiative has qualified for the Los Angeles ballot, increasing the chances that voters will get to choose whether to keep pot shops open in the city when they go to the polls in May.

The measure would allow any medical marijuana dispensary that meets certain requirements to remain open. The requirements include limited hours, background checks for dispensary staff and operating a specified distance from schools and parks. The measure would also raise taxes on medical marijuana sales by 20% to help pay for city regulation of the industry.

The City Council is required to put the second medical marijuana initiative on the ballot because it involves a change to a tax that was approved by voters. In 2011, voters approved a $50 business tax on every $1,000 of gross receipts for medical marijuana sales. Because the new measure would increase that tax, it must be put to voters, according to Holly Wolcott, in the city clerk’s office.

The initiative's backers, who said they were notified by the city clerk Friday that they had collected the required 41,138 valid signatures, represent a group of dispensaries that opened after a citywide moratorium on pot shops was enacted in 2007. A rival medical cannabis measure, which would allow only those dispensaries that opened before the moratorium, qualified for the ballot earlier this week.

The first medical marijuana initiative, which does not involve a tax increase, will be sent to the City Council, which must decide by the end of the month whether to enact the proposed ordinance, call a special election or place it before voters in the May 21 election.

The City Council will now decide whether to enact the proposed ordinances, call a special election or place it before voters in the May 21 election.

David Welch, an attorney for the group that qualified for the ballot on Friday, said supporters for the initiative had already raised $400,000 for the campaign and were working to raise $500,000 more.

[For the Record, 6:00 p.m. Jan. 4: An earlier version of this post incorrectly said that the City Council would have to decide whether to adopt the second of two ordinances or place it on the ballot. Because that ordinance involves a tax increase, it will have to go to voters.]

RELATED:

L.A. City Council bans medical marijuana dispensaries

L.A. repeals its ban on pot stores

Initiative to keep some L.A. pot shops open qualifies for ballot

-- Kate Linthicum at Los Angeles City Hall

twitter.com/katelinthicum

Photo: Budtender Loren Brazel waits for a patient to decide on what strain of medicinal marijuana would be best to treat his ailment in the dispensary area of the Avalon Wellness Center in Long Beach in March. Credit: Genaro Molina / Los Angeles Times