20200546 Ver 1_Kenilworth Road Percussive Activities Memo_2020-04-23_20200423

NoWithersRavene[
Our People. Your Success.
MEMORANDUM
To: Troy Beasley
From: Randall D. Hintz, P.E.
Date: April 23, 2020
Project: City of Asheville - Kenilworth Road Culvert Replacement
Subject: Percussive Rock Removal
The replacement of the subject culvert under Kenilworth Road will involve the excavation of the existing
culverts and replacement with a new culvert which has been properly sized to accommodate the hydraulic
conditions. During this installation, open trench installation techniques will be utilized to excavated the soil
materials over the culverts, beginning at the road level. Because this project involves the replacement of
existing infrastructure in the same location, it is anticipated that the overlying soil materials are backfill from
the original installation, and will not include any rock excavation requiring percussive equipment to reach
grade of the existing pipes. However, the new infrastructure is designed to be installed at a slightly lower
elevation than the existing culvert on the downstream end. As such, it will be necessary to excavate slightly
below the grade of the existing system. Based on observed site conditions, it is anticipated that the
degradation of the inverts of the existing piping has resulted in stormwater escaping the system through the
bottom of the pipes resulting in erosion of the soil materials under the existing piping. This is evidenced
through the significant settlement of the existing pipes on the downstream side of the system and water
freely moving under those pipes. Therefore, it is likely that no percussive rock removal will be necessary in
reaching the final grade of the new piping. However, the need for some degree of rock removal cannot be
ruled out as part of this installation. The necessity and/or degree of this activity will only be known once
the system is excavated. If percussive rock removal is required, it is anticipated that these activities would
be completed via pneumatic jackhammer and last no more than 4-hours in duration within a single day.
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