He let since face-up to fixed then waist-high of gravel .
(ROOT_0 (S_0 (ATS_3 (NP_1 (PRP_0 He)) (VP_4 (VBD_2 let) (S_2 (NP_1 (IN_2 since) (NN_3 face-up)) (VP_0 (TO_0 to) (VP_1 (ATVP_3 (VBD_1 fixed) (ADJP_0 (RB_0 then) (JJ_0 waist-high))) (PP_0 (IN_1 of) (NP_2 (NN_3 gravel)))))))) (DOT_0 .)))