Alpine residents with lots of 11,000 square feet or more could soon build a detached apartment in their backyard, but the city wants to hear from homeowners first.

The Planning Commission holds its final public hearing on the proposed detached accessory dwelling unit ordinance Tuesday, Aug. 18, at 6 p.m. at City Hall, 20 North Main St. After the commission votes on a recommendation, the ordinance moves to the City Council for adoption before a hard Thursday, Oct. 1 state deadline.

Why it's happening now

Utah Senate Bill 284 requires every municipality with more than 5,000 residents to allow detached ADUs on qualifying lots by Oct. 1. Alpine's estimated population of 10,444 puts it squarely under the mandate. Staff first brought draft code language to the commission on Tuesday, Aug. 4 and incorporated feedback into the version now up for a vote.

As we reported Aug. 12, Tuesday's hearing is the last chance for public comment before the council takes up the measure.

What the proposed ordinance says

According to the agenda packet published Aug. 13, the key rules are:

• Minimum lot size: 11,000 square feet (the state-mandated floor).
• Maximum ADU size: 1,200 square feet of living space.
• Owner occupancy: The property owner must live in either the main home or the ADU. A temporary-absence exception of up to three years covers military service, job assignments or care-facility placement.
• Parking: Two on-site spaces for the ADU, in addition to what the primary home requires. (State law caps the requirement at one space for units smaller than 650 square feet.)
• Design: Materials and style must match the main dwelling.
• Setbacks and height: Same as accessory buildings in the applicable zone.
• One per lot: If a property already has an internal ADU, no detached unit is allowed.
• Utilities: The ADU must connect to the same water, gas and electric meter as the main home. If the meter lacks capacity, the ADU is prohibited.

State law also allows Alpine to prohibit short-term rentals of fewer than 90 consecutive days and bars cities from requiring a conditional use permit for ADUs in residential zones.

Infrastructure questions linger

The mandate has drawn concern about Alpine's utility capacity. At the Jan. 27 City Council meeting, city engineer John Schiess of Horrocks Engineers warned that if many ADUs are added, sewer and water capacity would need to be reevaluated. Council member Sarah Blackwell asked whether the city could say detached ADUs "will not work in Alpine." City Administrator Shane Sorensen replied that the city would have to wait and see what came through the legislature.

That bill is now law. The city must comply.

How to weigh in

Residents can attend Tuesday's hearing in person or watch live on the Alpine City YouTube Channel, accessible from alpineut.gov. Written comments can be directed to the City Recorder at 801-756-6347, ext. 3. The full agenda packet and supporting documents are posted at alpineut.gov.

Planning Commission Chair Alan MacDonald will preside over the hearing. The commission will also consider separate text amendments to the Alpine Development Code at the same meeting.