Making way for increased production of hydro-electric power
Document type: Case Study

Making Way for Increased Production of
 Hydroelectric Power in Southern Vermont

Project Summary
PROVIDE FOR MORE PRODUCTION OF
ELECTRICITY WHILE KEEPING IMPORTANT LOCAL
RECREATION ALIVE
DynoConsult, Dyno Nobel’s specialty consulting division,
helped this hydroelectric power station in southern
Vermont solve unique construction challenges to
increase electric production and efficiency for the town.

Background
INEFFICIENT POWER GENERATION WAS THE mechanical rock breaking techniques. In addition, the
STATUS QUO FOR THIS HYDROELECTRIC STATION rock needed to be excavated without excessive vibration
Originally built to power a marble producing plant, the damage to the existing electrical substation or the 100-
site was purchased by regional power company who year-old concrete dam. decided to continue generating electrical power for their
manufacturing and support the surrounding town. Technology Applied
The project required rehabilitation of the water intake,
including the removal of approximately 250 cubic yards DigiShot® ELECTRONIC INITIATION SYSTEM
of rock, allowing enough water flow to operate an ALLOWS FOR ACCURATE DECK TIMING TO
additional two turbines. CONTROL VIBRATIONS
Because the dam and intake was built in the early The initial blasting required a cut of 15 feet of rock to be
1900’s, there were additional challenges of working blasted. The decision was made to use three explosive
around an electrical substation (built within 40 feet of decks per hole. 2ms delay timing was used between
where rock excavation is required) and the original decks with 18ms used between holes, providing 1 deck
concrete dam (within 20 feet of the excavation point). per 8ms delay.

y timing was used between
where rock excavation is required) and the original decks with 18ms used between holes, providing 1 deck
concrete dam (within 20 feet of the excavation point). per 8ms delay. A seismograph reading recorded at the substation 40
 Project Goals feet from the blast site were 0.21 inches per second. Blast event ground vibration readings on the dam, which
EXCAVATE ROCK WITHOUT EXCESSIVE was located 20 feet from the blast site, were less than
VIBRATION DAMAGE OR MECHANICAL ROCK the allowable 2 inches per second as recorded by a third
BREAKING party seismograph monitoring company. Well within the
 vibration specifications established for this project
The team set out to drill and blast as much rock as
possible to avoid the use of time consuming and costly

Making Way for Increased Production of
 Hydroelectric Power in Southern Vermont

Seismograph geophone secured to the concrete foundation on the
100-year old concrete dam

DIGISHOT® PROVED TO BE A VITAL TOOL IN
 Value Added
SAFE REMOVAL OF ROCK WITH SIGNIFICANT
COST SAVINGS AND MINIMIZING BLAST RISK
The customer was able to meet excavation schedules in
a cost effective manner by using electronic detonators
verses more costly mechanical means. A new dam gate
assembly was put in place to regulate water flow into the
turbines. A 15 foot rock cut was blasted and excavated
to allow water flow to the new gate system.
Rock excavation was within 15 feet of the new
excavation and construction. Rock was removed in 5
foot lifts using two explosive decks per hole. The pattern
was laid out 3ft x 3ft x 5ft deep. Primer was a 0.75 pound
cast booster charge was used in each deck yielding 0.9
pounds per cubic yards powder factor. Two rows of 4
holes were used with 1ms between decks, 4ms between
holes and 6ms between rows.
The initial blast generated a reading of 0.5 ppv on the
dam gate. Subsequent closer blasts developed readings
between 1.4 ppv and 5.2 ppv which were deemed
acceptable by project engineer. By properly engineering
and executing blast designs, using precise and accurate
initiation technology, and properly covering the blasts,
the material could be safely excavated, making way for
the extra water to increase hydroelectrically production.

Disclaimer This case study is provided for informational purposes only. No representation or warranty is made or intended by DYNO NOBEL INC. /
DYNO NOBEL ASIA PACIFIC PTY LIMITED or its affiliates as to the applicability of any procedures to any particular situation or circumstance or as to
the completeness or accuracy of any information contained herein. User assumes sole responsibility for all results and consequences.

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