HomeMy WebLinkAbout2906_DavidsonMSWLF_RockBlastReport_DIN26162_20160602
June 2, 2016
Mr. Perry Sugg, P.G.
Permitting Hydrogeologist
NC DEQ Division of Waste Management
1646 Mail Service Center
Raleigh, North Carolina 27699-1646
RE: Davidson County MSW Landfill
Phase 2 Area 2 Cell 2 - Rock Blasting Documentation
Dear Mr. Sugg:
On behalf of Davidson County and based on our earlier correspondence, Smith Gardner, Inc.
(S+G) presents this letter to document rock blasting performed recently during construction
of Phase 2 Area 2 Cell 2 of the County’s municipal solid waste (MSW) landfill. A rock blasting
plan was submitted April 8, 2016 and was approved by North Carolina Department of
Environmental Quality (NCDEQ) Division of Waste Management (DWM) on April 11, 2016. This
report documents the blasting events and provides vibration water level monitoring results
as requested by the DWM.
Blasting Events
The blasting was performed National Quarry Services, Inc. (NQS), under subcontract to
Shamrock Environmental Corp. who is the general contractor for the project. Personnel
from S+G were also present during blasting procedures. Blasting was conducted during
daylight hours on April 27 and May 4, 2016. The drill hole pattern, charge weights, and
delays were selected to minimize the amount of energy which may impact the underlying
rock. The planned peak particle velocities at blast monitoring locations were designed to be
<1 inch/sec. The attached figure presents the approximate blast locations.
Blasting procedures were executed in general accordance with the approved blasting plan
from NQS.
Blast Monitoring
During blasting, seismographs were used to monitor three locations (one adjacent to Area 2
- Cell 1; one north of Cell 2 and between Monitoring Well 2 to the west and Monitoring Wells
10S and 10D (aka PZ-37S and PZ-37D) to the east; and one adjacent to the leachate storage
tank facility) for each blast. Locations were selected based on closest proximity to the area
that may be affected by the blasting. Measurements were collected for peak particle
velocity, frequency, and sound level. Table 1 presents the data retrieved from each
seismograph during each blast event. The peak velocities recorded were well below the
generally accepted criterion of 1 in/sec. Blasting records are included in Attachment 1.
Mr. Perry Sugg, P.G.
June 2, 2016
Page 2 of 2
In addition to the use of seismographs, S+G personnel measured water levels in Monitoring
Wells 2, 10S, and 10D both before each blast and immediately after the all-clear signal was
given. No changes in water levels were noted.
Rock Removal Quantities
As you know, initial estimates projected removal of up to approximately 20,000 CY of rock to
install Area 2 Cell 2. Calculations after blasting indicate approximately 840 CY of rock were
removed during the 2 blasting events and which included several large boulders. This was
due to the successful ripping of overlying material which turned out to be mostly weathered
rock. Rock quantities removed from individual blast areas are summarized below. Rock was
removed to 4 feet below subgrade elevations at both locations.
4/27/16: 736 CY removed; and
5/4/16: 104 CY removed.
Conclusion
The blasting that was performed in Area 2 Cell 2 appears to have met the rules and
requirements of the DWM. Based on the generally low velocities generated and the lack of
changes in water levels pre- and post-blast, no changes to the groundwater flow regime are
expected and no modifications to the water quality monitoring plan are proposed at this time.
A copy of this blasting summary letter will also be included in the construction quality
assurance (CQA) report for the project. Please contact us with any questions or concerns at
(919) 828- 0577 or by email below.
Sincerely,
SMITH GARDNER, INC.
Joan A. Smyth, P.G. Pieter K. Scheer, P.E.
Vice President, Senior Hydrogeologist Vice President, Senior Engineer
joan@smithgardnerinc.com pieter@smithgardnerinc.com
Attachments: Figure1- Site Map with Blast Locations
Table 1 - Seismograph Data
Attachment 1- Blast Reports
cc: Steven Sink, Davidson County
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Attachment 1
Blasting Reports
Rock Blasting Documentation
Davidson County MSWLF - Phase 2 Area 2 Cell 2
Davidson County, North Carolina
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