Well you have the ID as $attach_id
so you can use a function such as wp_get_attachment_url()
where you can pass $attach_id
and get a url returned:
$featured_url = wp_get_attachment_url( $attach_id );
Or if you want more information such as width, height, etc. you can use functions like wp_get_attachment_image_src()
or wp_get_attachment_metadata()
.