Air carrier pilot reported damage to the bottom of the engine cowl and IDG occurred during taxi in an area of plowed berms of snow that had not been adequately cleared.

Narrative

The aircraft was parked at the South Ramp next to the FBO; where large piles of snow had accumulated and subsequently turned into ice. We both carefully reviewed the NOTAMs and agreed upon the taxi instructions provided by ATC prior to taxi. The only two NOTAMS (see attached release) that applied to our taxi route were:**NEW** PHL Day 0-Day 1PHL TWY ALL FICON (Field Conditions) PATCHY COMPACTED SN 4FT BERMSPHL RWY 35 TWY DIRECTION SIGN AT TWY D LGT U/S (Unserviceable)During taxi; we observed several taxiways with residual snow and ice on the surface; as well as berms of snow and ice along taxiway edges. We maintained the taxiway centerline at all times and the taxi appeared uneventful. On taxiway Sierra; the crew received an alert for ELEC IDG 1 (Integrated Drive Generator) Low Pressure. The FO immediately advised Ground Control of the situation and requested permission to stop the aircraft. ATC approved the aircraft to stop and we ran the procedures. With the procedures complete; we advised Operations; MX (Maintenance) Control; and advised Ground our intent to return to the South Ramp. We entered the South Ramp from taxiway Delta; thus avoiding (unbeknownst to us) the protruding frozen snow at the intersection of Alpha and Delta. After the aircraft was parked; maintenance personnel conducted an external inspection of the #1 engine and discovered damage to the bottom rear of the inlet cowl and IDG. We immediately notified Ground Control of the damage and requested an inspection of the taxiways used during the taxi operation to check for debris and/or oil contamination. Airport Operations sent a vehicle which repeatedly drove the taxi route and was unable to find anything. After sunrise provided better visibility conditions; Airport Operations was able to locate the event site. The inspection revealed snow and ice protruding significantly onto the taxiway surface; extending well beyond the taxiway edge referenced in the NOTAMs.Suggestions: The northeast (GA) side of the airfield did not receive the same level of snow removal service as the commercial terminal side. While NOTAMs were active for compacted snow and 4-foot berms; the actual snow and ice intrusion extended well beyond these parameters and protruded significantly into the taxiway surface area.NOTAMs definitions for COMPACTED SN and BERMS were not followed by Airport Operations in their ATC reporting. Airport Operations admitted to the protrusion or frozen snow and swept it clear. Interestingly; before it was found; the comment was made that the NOTAM for BERMS covered protrusions; which it does not. There are very specific reporting requirements when the usable width of taxiways is reduced; which does include intersections. To prevent this happening in the future; we should either bias towards parking our aircraft where other heavy jet operators park. If unable to do that; the taxi route should be verified by airport personnel prior to taxi; at least to a point used by mainline aircraft.