Avoiding a Dam Midlife Crisis

swimminghersheyΠολεοδομικά Έργα

25 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

50 εμφανίσεις

www.KleinschmidtUSA.com

B
Y
: J
EFF

C
OFFIN
, P.E.

S
R
. C
IVIL

E
NGINEER
/H
YDROLOGIST

K
LEINSCHMIDT

A
SSOCIATES

M
IDLIFE

C
RISIS

What causes a midlife crisis for a dam...







...and what can happen as a result?


www.KleinschmidtUSA.com

M
IDLIFE

C
RISIS
!

Symptoms:




old, tired feeling



in a rut



may seek new
partner

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T
OOLS
...

Can’t monitor dam’s mental/emotional health,
so need to focus on physical health.

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C
ONGESTIVE

D
AM

F
AILURE

Want to avoid this type of
midlife (or young
-
age)
crisis.

www.KleinschmidtUSA.com

W
HY

BE

C
ONCERNED
? C
ONSEQUENCE
:


Owner
: Lose
ability to generate
power



Others
: Lose
water supply,
navigation,
recreation benefits

www.KleinschmidtUSA.com

C
ONSEQUENCE

(
CONT
.):


Downstream
: Can be heavily impacted

www.KleinschmidtUSA.com

D
AM
-
S
AFETY

C
HECKUP



B
ASIC

A
PPROACH

1.
Hazard Potential

2.
Regular Inspections/Evaluations

3.
PFMA / DSSMP

www.KleinschmidtUSA.com

1. H
AZARD

P
OTENTIAL

D
ETERMINATION

Based on Consequence of Failure
:



High
: Loss of life possible due to breach



Significant
: No loss of life, but major
property damage



Low
: No significant impacts

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2. R
EGULAR

I
NSPECTION
/E
NGINEERING

E
VALUATION


Yearly by FERC engr.


Every 5 years by IC



Protocol:


Visual inspection to assess condition


Analysis (or review) of:


Spillway adequacy


Structural stability


Review of S&M data



Single most important inspection tool?

www.KleinschmidtUSA.com

T
HE

M
OST

I
MPORTANT

D
AM

I
NSPECTION

T
OOL
:

The Eyes!

www.KleinschmidtUSA.com

(thanks to Kim de
Rubertis
)

3. P
OTENTIAL

F
AILURE

M
ODE

A
NALYSIS


Multi
-
disciplinary team


Review background info.


Identify PFMs


Classify PFMs (priority)


Focus DSSMP on PFMs

www.KleinschmidtUSA.com

T
WO

R
ECENT

D
AM

M
IDLIFE

“I
NCIDENTS


1.

Embankment Dam with boils at toe
after 9+ year drought


2.

Gravity Dam hit by piece of rock
from abutment

www.KleinschmidtUSA.com

1.

E
MBANKMENT

D
AM



N
EBRASKA


Constructed 1937
-
41 (age 70) / 163 ft high, 3.1 mi long


Earth foundation,
sheetpile

cutoff wall


Drought in CO
-
WY
-
NE: reservoir failed to fill 2002
-
2009


High 2010
precip
., raised res. 25 ft higher than prior 7 years


Boils at toe


raised concern, prompted investigation

www.KleinschmidtUSA.com

1.

E
MBANKMENT

D
AM

(
CONT
.)


Boils noted in toe drains


lateral and longitudinal
drainage ditches at toe of
dam


Investigation:


Review of current and historical
data (seepage flows, piezometer
levels)


Site visit


Preliminary seepage analysis


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1.

E
MBANKMENT

D
AM

(
CONT
.)


Findings:


Boils present historically (e.g.
1987)



2010 boils similar to 1987 but
smaller



No evidence of transport of soil



Current seepage flows and
piezometer levels were within
historical ranges (data since 1953)



Vert. hydraulic gradient estimated to
be approximately 0.5
-
1.0 ft/ft (boils
gen. result from 0.5
-
0.8)

www.KleinschmidtUSA.com

1.

E
MBANKMENT

D
AM

(
CONT
.)


Recommendations:


Continue monitoring:


Visual monitoring of boils


Toe drain flows


Piezometer levels



Install 2 nested
piezometers

to verify vert. gradients



Evaluate in detail during
next Part 12D inspection
(2011
-
12)

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2.

G
RAVITY

D
AM



M
ONTANA


Rock
-
filled timber crib construction


Constructed 1905
-
07 (age 104)


38.5 ft high, 257 ft long


3
-
ft thick reinforced concrete overlay
with post
-
tensioned anchors added in
1989

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2.

G
RAVITY

D
AM

(
CONT
.)


Rock bolts
added in 1974
to stabilize left
abutment cliff

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2.

G
RAVITY

D
AM

(
CONT
.)


POOP HAPPENS:
August 2010


piece of
rock cliff fell from left
abutment onto dam


Piece estimated at 205
tons: 32’ L x 11’ H x 2
-
17’ W


Damage to steel
superstructure and gates,
relatively minor apparent
damage to dam crest

www.KleinschmidtUSA.com

2.

G
RAVITY

D
AM

(
CONT
.)


Findings and follow
-
up:


PFM
ID’d

in 2005 PFMA (PFM No.
1, Cat. II)


est. up to 285
-
ton
rock could fall


Rock fall came from formation to
left of that stabilized in 1974


Reservoir lowered to aid damage
inspection/repair


Detailed inspection of rock face
and rock bolts by
geotech
. engr.


Repairs to gates and
superstructure planned


Further stabilization of rock cliff
planned

www.KleinschmidtUSA.com

R
E
-
C
AP
: T
O

A
VOID

D
AM

M
IDLIFE

C
RISIS

1.
Know Dam’s Hazard Potential

2.
Regular Inspections/Evaluations (Eyes!)

3.
PFMA


to ID & Prioritize PFMs

4.
DSSMP


focused on PFMs

www.KleinschmidtUSA.com

L
ET

S

K
EEP

O
UR

D
AMS

H
EALTHY

& H
APPY
, W
ITH

L
ONG

L
IVES

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