HB0030 BOHAI SEA SUBMARINE WORK FOR MV TAI KEYSTONE IN WEST ANCHORAGE OF QINHUANGDAO PORT FROM 0000UTC TO 1100UTC DAILY FROM 4 TO 6 APR. ENTERING AND ANCHORING PROHIBITED WITHIN 0.4 MILES RADIUS OF 39-49.93N/119-38.04E. PASS WITH SLOW SPEED. CAUTION ADVISED. HEBEI MSA CHINA.