The Anne Arundel County Council passed a bill Monday that will require developers to allocate a portion of new units for moderate-income residents and create more diverse housing types in certain areas, in spite of environmental concerns raised by community members.

Known as the Housing Attainability Act, the bill would require new housing developments with 20 or more units to designate 10% of for-sale units and 15% of rental units to be affordable. It will also add now-missing housing types, such as triplexes, fourplexes and stacked town houses, to the county’s zoning ordinance.

The revamped legislation passed in a 4-3 vote along party lines — Allison Pickard, Julie Hummer, Lisa Rodvien and Pete Smith, all Democrats who sponsored the bill, voted to approve it. The changes will take effect July 1.

“Our county is highly attractive; we have a lot to offer, including a great, robust job market, yet, we have a low affordability score due to housing scarcity,” said Pickard, a Glen Burnie Democrat. “This bill will allow us to use our remaining available land more efficiently and [provide] a variety of dwelling types — we [have] options for the newly launched young folks and the downsizing aging population and everyone in between.”

This is not the first time the county has tried to expand affordable housing. Last year, the council introduced similar legislation, which failed to pass. Pickard, one of four council members who voted against the bill in December, said at the time she felt it fell short and didn’t amend parts of the code that would let parcels reach their maximum allowable density.

While County Executive Steuart Pittman supports the updated legislation, he and others raised concerns about how the number of developable sites on a piece of land is calculated.

“My understanding was that the change in how density is calculated — using the gross parcel acreage rather than the net after removing acreage that is not developable due to sensitive environmental features — and the amendments to bulk regulations, were intended to facilitate more [moderately priced dwelling units],” he said in written testimony. “It was not until very recently that I was made aware that the bill is drafted in a way that they also apply to parcels exempt from the [moderately priced dwelling unit] requirements, specifically developments with fewer than ten homes.”

In some situations, developments with 10 to 19 units could make a contribution to the Housing Trust Special Revenue Fund, the revenue from which goes toward providing affordable housing for low- to moderate-income county and Annapolis residents, instead of setting aside affordable units. Housing developments with nine or fewer units do not have to offer affordable units.

The legislation also includes adjustments to bulk requirements to allow more flexibility in site design, as well as a tiered system to provide a density bonus for developments that build affordable housing units, allowing additional units to be developed.

Pittman said his preference would be to move the legislation forward with an amendment tying bulk regulation and density calculation changes to properties subject to the moderately priced dwelling unit program and then try to “consider changes to county development regulations to encourage missing middle housing in a subsequent bill.”

But if the bill passed as written, Pittman said, he would sign it and “immediately” convene interested parties to make recommendations to improve the bill before it takes effect next summer.

In both written and in-person testimony, nearly three dozen residents voiced worries about the legislation potentially incentivizing sprawl and affecting remaining green spaces throughout the county.

Matt Johnston, executive director of the Arundel Rivers Federation, acknowledged the need for both affordable housing and environmental protections and asked the council to consider amendments or hold the bill.

“We believe that if you change the net density everywhere, especially on those acres that have floodplain, wetlands and steep slopes, you will increase the likelihood of greenfield development,” he said. “And if you want to do that and deliver [moderately priced dwelling units], that’s flexible, that’s targeted, but this bill does not do that — that net density is everywhere, all at once, regardless of where and how the development occurs.”

Hummer, a Laurel Democrat, emphasized that the legislation is a good starting point, calling it “one tool in the toolbox.”

“This is not going to usher in a landslide of development,” she said. “That’s not how development works, that’s not how the provisions in the code work to do this, but it’s going to open some doors and give us some more options.”

Pickard said the bill did not decrease or weaken any of the county’s environmental policies.

“Being allowed to take some lot sizes and a little bulk [regulations], a little nip and tuck here, is going to get to the scarcity of housing inventory in this county at every price point,” she said.