A temporary but longstanding moratorium against small-lot development around Lake Whatcom could be passed one of two ways at the Whatcom County Council meeting, Tuesday, Jan. 15.

A moratorium on development on lots smaller than five acres in the Lake Whatcom watershed has been in effect since 2005, council member Sam Crawford said. The temporary ban must be renewed by council every six months.

The moratorium is intended to contain the amount of pollution caused by runoff from developed lots. Lake Whatcom provides drinking water to about 100,000 Bellingham-area residents.

This time, Crawford proposes an alternative to the standard moratorium, creating an exception for "clustered" lots on land zoned for one home on five acres. A clustered development could have homes on one-acre lots, but no more than would be allowed by the five-acre zoning. A 10-acre parcel, for example, could have two houses on one-acre lots with eight acres of open space.

Clustering benefits the lake, Crawford said, because it reduces the amount of "impervious surfaces" such as driveways. Impervious surfaces increase runoff - a major source of phosphorus pollution - into the lake.

Public hearings will be held on both Crawford's moratorium and the standard ordinance, which would not allow any construction on lots smaller than five acres, including clustered lots. The council is expected to approve one of the moratoriums on Tuesday; the meeting starts at 7 p.m. at council chambers, 311 Grand Ave., Bellingham.

The clustering approach has at least one detractor. Wendy Harris, a Lake Whatcom watershed resident who is active in conservation groups, said Crawford's proposal would increase runoff, not reduce it, by encouraging development.

It also could lead to less effective treatment of runoff, she said. Smaller lots will be exempted from strict stormwater rules the council is about to pass for Lake Whatcom. These clustered homes could qualify for the exemption, Harris said.

The council is not considering an exemption for lots as large as one acre, Crawford said.

Reach Ralph Schwartz at 360-715-2289 or ralph.schwartz@bellinghamherald.com. Read his politics blog at blogs.bellinghamherald.com/politics or follow him on Twitter at @bhamheraldpolitics.