sewer installed by 都道府県 (todōfuken, “a prefecture”) in order to treat sewage from two or more 市町村 (shichōson, “cities, towns, and villages”)

convenient

not ... at all

even if ...,...cannot

sewer / drainage channel for rainwater etc.

convenience

river basin

very, exceedingly, awfully / (before a negative form) not at all, at all, by no means

improvement / outfitting, being equipped for / service, maintenance

to equip, to provide with / to put in good condition / to service