Guam lawmakers debate ADU bill; agencies warn of risks to aquifer, letters added to committee report

Senator Christopher M. Duenas introduced Bill 57-38 COR on the floor, asking that the measure be placed on third reading and describing it as an effort "to strengthen housing options by adding a new sub-article 3 to article 1 of chapter 61, title 21" to authorize accessory dwelling units, or ADUs, in residential zones.

The bill's author, Senator Christopher M. Duenas, said he and cosponsors modeled the proposal on ADU laws in other jurisdictions and had added technical amendments after receiving late written testimony from regulatory agencies. "It's very durable," Duenas said, and he described multiple changes: clarifying that ADUs must comply with Guam building and utility codes; replacing references to covenants with deeds for land-management filings; and making building permits the controlling permit type for ADU construction.

Why it matters: debate focused on whether the bill would increase housing density over Guam's sole-source aquifer and how to limit contamination risk. Senators and agency witnesses raised concerns about nitrates, PFAS and other contaminants moving from septic systems into the Northern Guam Lens Aquifer (NGLA).

Key provisions and amendments discussed

Duenas read an amendment he proposed that would restrict ADUs on unsewered lots within the groundwater protection zone. Under the amendment as described on the floor, an ADU proposed within the groundwater protection zone and within 200 feet of a sewer main would be permitted only if both the primary residence and the ADU were connected to sewer; for properties islandwide within 50 feet of a sewer main the amendment would likewise require sewer connection. The author also described a minimum-lot-size rule for ADUs over the groundwater protection zone: a lot must be at least 19,200 square feet (commonly referenced locally as a half acre) and both the primary and ADU would be required to be served by an advanced, "type 4" nitrogen-reduction on-site sewage system unless connected to sewer.

Those technical changes were the focus of extended floor debate. Duenas told colleagues the language responded to agency concerns and to a letter from a former CCU chair, Joey Duenas, urging protections for the NGLA.

Agency warnings appended to committee report

A senator read Guam Waterworks Authority's written testimony into the record and moved to append three letters'from GWA (dated March 25, 2025), Guam Environmental Protection Agency (dated March 24, 2025) and a letter from Joey Duenas (dated Feb. 10, 2025)'to the committee report. The motion to append the letters carried with no objection.

The GWA letter, as read into the record and signed by Miguel C. Berdallo, general manager of the Guam Waterworks Authority, stated that "GWA does not support the bill as amended" and said the amendments "do little to address GWA's previously stated concerns" about increased discharge from septic systems and the inability of even advanced on-site systems to remove PFAS and other emerging contaminants. The letter warned the agency is already incurring significant costs to address PFAS and rising nitrate levels and said increased treatment and monitoring would lead to higher water and sewer bills for GWA customers.

Points of contention in floor debate

- Lot size and density: Several senators questioned whether allowing ADUs on lots as small as a half acre would effectively increase residential density in unsewered areas and thereby increase contaminant load to the aquifer. One senator cited GWA figures (relayed on the floor by the bill's author) that roughly 1,250 households in the northern area are within 200 feet of a sewer main and that as many as 2,000 islandwide are within 50 feet of sewer mains.

- Type 4 systems vs. sewer connection: Senator Mosse proffered an amendment to replace a proposed requirement that lots be served by a "type 4" advanced nitrogen-reduction system with a requirement that they be connected to sewer. That amendment was objected to on procedural grounds and the motion to adopt it failed on the floor after members were asked to indicate support by voice/hand.

- Limit on number of ADUs per lot: Lawmakers agreed, without recorded objection, to an amendment to subsection 21 specifying that a maximum of one ADU could be created on a qualifying lot in the groundwater protection zone; the sponsor and others characterized that change as intended to limit density where the aquifer is at risk.

Outcome and next steps

On the floor the body appended the three agency and stakeholder letters to the committee report. Several amendments were debated; at least one proposed substitution (changing "type 4" to "sewer") failed after an objection and an informal hand-raise. Lawmakers later recessed the session and planned to resume consideration of the pending amendments and the substitute language at 2 p.m. The bill remained under active amendment at the time of recess.

What lawmakers said

"If you want an ADU, you need to hook up to the sewer," Senator Christopher M. Duenas said as he described the amended language proposing mandatory sewer connection near mains. By contrast, a senator from Barrigada raised concerns that requiring sewer hookups for homeowners on remote half-acre lots effectively denies those residents the option to build ADUs until sewer infrastructure arrives.

Ending note

Senators left the floor to reconvene later in the day to resolve outstanding statutory language and finalize whether sewer connection, type 4 systems or minimum-lot requirements would control ADU permitting in groundwater-protection areas.