Section 31. A public entity, including regional planning agencies, may apply to the division for a planning or a technical assistance grant by the commonwealth for the following purposes: assisting a public entity in developing a comprehensive water pollution abatement plan for the public entity; assisting a public entity in developing an integrated water asset management plan for the public entity; or assisting a public entity identify and plan for green infrastructure opportunities for the public entity. The division may accept and shall give preference to planning and technical grants applied for jointly by 2 or more public entities. Upon approval by said division, the division may grant for such purpose, a sum not to exceed 30 thousand dollars. In no case shall a grant exceed the reasonable and necessary cost of such planning, after subtracting therefrom any federal grant made to such public entity for the same purpose. The division may direct that such planning be undertaken in such manner as to maximize federal reimbursement, or to minimize the cost to the commonwealth, including, in appropriate cases, metropolitan-wide comprehensive planning and programming for co-ordinating activities affecting the development of the area. Planning or technical assistance grants authorized under this section need not be repaid to the commonwealth, and shall be in addition to financial assistance made available under other sections of this chapter.