ACFT DAMAGED AS L WING LEADING EDGE DEVICES IMPACT SNOW BERM IN A NIGHT OP.

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WHILE TAXIING WBOUND ON TXWY E ENRTE TO RWY 13 AT MDT; THE L WING OF OUR B-727 CONTACTED THE UPPER PORTION OF A SNOW BANK THAT HAD NOT BEEN PROPERLY CLRED AWAY FROM THE TAXI AREA. CONDITIONS (WX) WERE NIGHT TIME AND WX BETTER THAN 5000 FT AND 5 MI. WHILE TAXIING FROM THE CARGO RAMP TO RWY 13 AT MDT I NOTICED THAT THERE WAS VERY LITTLE SNOW AT THE BEGINNING OF TXWY E. AS WE PROGRESSED ABOUT ANOTHER MI DOWN THE TXWY ON THE TXWY CTRLINE; I NOTICED THAT A SNOW BANK WAS AHEAD AND THAT A SIGNIFICANT PORTION OF THIS SNOW BANK PROTRUDED INTO TXWY E. TRAVELING WBOUND; FROM THE TXWY CTRLINE SOUTHWARD; IT APPEARED THAT STAYING STRICTLY ON THE TXWY CTRLINE WOULD PLACE US UNCOMFORTABLY CLOSE TO THIS UNCLRED SNOW BANK. I THEREFORE ADJUSTED MY PATH 15 FT TO THE R (N) TO ALLOW EXTRA CLRNC. THE AREA TO THE R OF THE TXWY CTRLINE IS DARK; UNLIT; AND UNMARKED (BLACKTOP). 15 FT R OF CTRLINE IS AS FAR AS I FELT COMFORTABLE BEING DISPLACED FROM THE CTRLINE. THIS ADDITIONAL DISPLACEMENT WAS NOT ENOUGH AS OUR L WING IMPACTED THE SNOW/ICE BANK DAMAGING #1 AND #2 LEADING EDGE DEVICES. THE ACFT WAS RETURNED TO THE GATE FOR INSPECTION WITHOUT FURTHER INCIDENT. THIS MISHAP OCCURRED BECAUSE THE MDT AUTHORITY DID NOT CLR THE TXWY SUFFICIENTLY OF SNOW AND ICE SUCH THAT NORMAL TAXI WOULD BE SAFE OR POSSIBLE. SUPPLEMENTAL INFO FROM ACN 264595: THE TKOF CHK WAS COMPLETED DOWN TO THE CAPT BRIEF. AS THE CAPT WAS BRIEFING THE TKOF AND DEP; #1 AND #2 L LEADING EDGE SLATS IMPACTED A SNOW BANK WHICH MEASURED 8 FT IN HT. IT IS WORTH NOTING THAT THE SAME ACFT WITH THE SAME CREW HAD ARRIVED EARLIER THAT MORNING AND TAXIED TO THE RAMP USING THE SAME RTE AFTER LNDG ON RWY 31. HOWEVER; 2 FACTORS WERE DIFFERENT -- THE LEADS HAD BEEN RETRACTED AFTER ARR. THE DEP WT (180000 LBS) WAS MUCH HEAVIER THAN THE ARR WT (124000 LBS). THE UNEVENTFUL ARR; COUPLED WITH THE UNUSUAL HT OF THE SNOWBANK; RESULTED IN A 'BAITED TRAP;' WHICH WE UNFORTUNATELY FELL INTO.