(1) A plan will be prepared for each basin by the planning agencies having authority within that basin. Each agency will plan only for that area for which it has authority or for other areas by agreement.

(2) Within each basin a single agency or committee will be responsible for coordination of the water pollution control and abatement planning efforts. Where possible, such agency or committee will also be responsible for the preparation and implementation of the water pollution control and abatement plan.

(3) To facilitate covering a logical planning area, a single agency may be made responsible for more than one basin.

(4) A single planning document may be proposed in which more than one basin is included, providing the basins are clearly designated.

(5) Any municipality may prepare and submit a separate service area plan through the basin plan coordinating agency or committee to ecology.

(6) The basin plan-coordinating agency or committee should be agreed upon by, but not limited to, ecology and county, municipal, metropolitan, regional and special purpose agencies having authority within the basin.

(7) Such agreement will be formalized by contract as provided for in chapter 39.34 RCW, the Interlocal Cooperation Act, when legally possible.

(8) Ecology shall assume the responsibility for preparation and coordination of the sewage drainage basin plans or will designate a plan-coordinating agency from among those agencies having jurisdiction within the basin.