Several workers trudging down a dimly lit subway tunnel.
Workers going down a tunnel headed to the dig sight
Workers in a tunnel are not necessarily headed to a dig site.  For example, they could be maintenance workers performing work on equipment in the tunnel, such as tracks.
exists e1 s1 s2 s3 x1 x2 x3.(a_down(s3) & Manner(e1,s3) & Theme(e1,x2) & Actor(e1,x1) & v_trudge(e1) & n_tunnel(x2) & of(x2,x3) & n_subway(x3) & a_lit(s2) & Theme(s2,x2) & r_dimly(x2) & n_worker(x1) & a_several(s1) & Theme(s1,x1))
exists e1 e2 s1 x1 x2 x3 x4 x5 x6.(n_sight(x5) & of(x5,x6) & n_dig(x6) & a_topic(x1) & a_down(s1) & Manner(e2,s1) & Theme(e2,x3) & Actor(e2,x2) & v_go(e2) & to(e1,x5) & Theme(e1,x4) & v_head(e1) & (x3 = x4) & n_tunnel(x3) & (x1 = x2) & n_worker(x1))