 Storm drains are typically  at shallower depths than combined sewers ; because , while storm drains are designed to accept surface runoff from streets, combined sewers were designed to also accept sewage flows from buildings with basements  .
<coherence>  Storm drains are typically  at shallower depths than combined sewers ; because , while storm drains are designed to accept surface runoff from streets, combined sewers were designed to also accept sewage flows from buildings with basements  .
 Storm drains are typically at shallower depths than combined sewers . This is because combined sewers were designed to also accept sewage flows from buildings with basements .