20200560 Ver 1_PCN Response Memo_20200529

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\\ /� TO: Stephanie Goss, NCDWR Lyle Phillips, ACOE
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0 FROM: Dan Clinton, P.E. — itCy of Raleigh
Raleigh DATE: May 29, 2020
MEMO SUBJECT: Lassiter Mill Culvert Cleaning Clarification Memo
Breakdown of Stream and Buffer impacts on Lassiter Mill Culvert Sediment
Removal Project
Point of Clarification
• Buffer zone areas were based upon current conditions for the approved
permanent and temporary access easements (see attached easement map)
• The sediment removal will stop at the downstream face of the culvert. See
attached photo.
Attachments:
• Exhibit 1 — Revised Work Map
• Revised work map shows Sediment Excavation Area, Access Area, and
Buffer Zones.
• Exhibit 2 — Easement Map
• Attachment 1 — Additional photo
Impacts:
Buffer —Temporary impacts (recalculated from previous application)
Zone 1 — 919 Sq Ft (calculated going to the water's edge)
Zone 2 — 312 Sq Ft (included area in the right of way not previously
included)
Stream impacts
114 Linear Feet (75 LF within the culvert — Permanent 39 LF temporary)
Clarification:
Sediment will be removed (leaving a depth of remaining sediment of one foot)
from 2 of the 4 culvert boxes. These boxes are 75 linear feet each. Additionally,
a sediment bar which has formed in front of the two boxes and is now blocking
flow to those boxes. This bar which is beginning to become rooted in with
vegetation will be sloped from one foot above the waters base flow elevation at
the waters edge at a slope of 12:1.
The revised work map shows the location of excavation. All excavated material
will be hauled off site to an approved spoil location. All soil is accumulated
stream bar type sediment.
Best Regards,
Municipal Building
222 West Hargett Street
Raleigh, North Carolina 27601
Dan Clinton, P.E.
One Exchange Plaza
Stormwater Department
1 Exchange Plaza, Suite 1020
Raleigh, North Carolina 27601
City of Raleigh
Post Office Box 590 • Raleigh
North Carolina 27602-0590
(Mailing Address)