Section 251. County agency

The  board  of  supervisors  may  appoint or
  establish an officer, board  or  body,  or  may  designate  an  existing
  officer,  board or body, or public authority which possesses the express
  power to act as such an agency, to act as a county water, water  quality
  treatment, sewer, wastewater disposal, drainage, refuse or public inland
  lake  protection  and  rehabilitation agency (hereinafter referred to in
  this article as the "agency") having the powers  hereinafter  prescribed
  in  sections  two  hundred  fifty-two,  two  hundred fifty-three and two
  hundred fifty-four, and such other powers and duties  as  the  board  of
  supervisors  may determine necessary to carry into effect the provisions
  of this article. Except in the case of a public  authority,  the  agency
  may  also be designated as the administrative head or body of any county
  district which may be established pursuant to  the  provisions  of  this
  article.  All  matters  relating  to  the  membership  of  such  agency,
  including, but not limited to, numbers,  method  of  selection,  tenure,
  qualifications  and  compensation,  shall  be determined by the board of
  supervisors.