Post on 21-Jan-2018
Mount Rainier National Park –Upper Nisqually Protection and Stabilization Project
Ingo Kuchta - Project Manager/EngineerBrian Bennett - EngineerMarty Ereth - BiologistRob Wenman - Planner
Pierce County Surface Water Management
November 17, 2017
. .
Problem Statement: Reoccurring damage to the existing levee structure during high flows.
– Location – Nisqually River: Right Bank
(near Nisqually gate main entrance to Mt. Rainier National Park)
– What is at Risk? – Mount Rainier National Park access and utility infrastructure. Nisqually Park Subdivision
– Proposed Project or Action - Construct a series of 28 rock deflectors
Project Overview
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Why is protection and stabilization necessary?
To protect critical infrastructure and maintain access to the Mount Rainier National Park
Protect the Nisqually Park Subdivision downstream
Substantially reduce reoccurring repair costs associated with damaging floods
Project Overview
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Maintenance Costs
11/17/2017
Note:
Costs do not factor in
today’s costs
MRNP– Upper Nisqually Protection and Stabilization Project
YEAR PIERCE COUNTY USACE
1991 $ 74,610
1992 $142,718
1993 $217,000
1995 $ 50,000* $200,000
1996 $ 50,000* $200,000
2003 $122,500
2004 $203,000
2005 $131,000
2006 $900,760
2010 $529,500
2011 $185,629* $752,529
2012 $652,655
2017 $243,440* 973,800
Subtotal $3502,812 $2,126,329
TOTAL $5,629,141
* County share is typically min. 20% of total cost
Levee/Revetment
Repair Costs
Since 1990
Reach Characterization – Glacial Fed
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Project
Site
Reach Characterization - continued
11/17/2017
• Contributing basin is 65 square miles
• Mostly within Mt. Rainier National Park
• Relatively undeveloped
• 80 inches of rain annually (avg.)
• Short duration runoff/steep gradient
• Large amounts of sediment transport
• Sediment drives channel thalweg.
MRNP– Upper Nisqually Protection and Stabilization Project
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Nisqually Levee
Na
tio
na
l P
ark
Bo
un
da
ry
Reach Characterization - continued
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Braided river
channel
High bench
terraced
floodplain
Lahar deposit/
old growth
forest
Levee
structure
Mt. Rainier
National Park
Sunshine Point
Campground
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Reach Characterization
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
2006 flood event
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
2006 flood event
11/17/2017
• Sunshine Point Campground and entrance road to Mt Rainier National Park washed out.
• Major damage to roadways, buildings and infrastructure.
MRNP– Upper Nisqually Protection and Stabilization Project
Source: MNRP
2006 flood event
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Source: MNRP
2006 flood event
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Source: MNRP
2006 flood event
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
2006 flood event
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Ongoing repairs 2006- present
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
2011
Repair
USACE
Ongoing repairs 2006- present
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
2012 Repair
(Pierce County)
River Diversion Plan - 2012
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Existing Conditions – flow velocity
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Existing Conditions 9580 cfs
ELJ Proposed Alternative
11/17/2017
• Construct a series instream engineered logjam structures (ELJ) to encourage sediment deposition in the washout area and lower water velocities. Additional deflector structures could be built along the revetment face as part of a second phase.
• Desired effect was to encourage the thalweg to move away from the revetment.
• Reduce water velocity around the logjam and revetment face encouraging sediment deposition.
MRNP– Upper Nisqually Protection and Stabilization Project
ELJ Alternative
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
ELJs
Mt. Rainier
National Park
Flow Velocities with ELJs
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Conditions After ELJs Construction 9580 cfs
ELJs
ELJs in updated flow model
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
ELJs
Deflector alternative
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Deflector
structures
• 4,760 feet of levee treated
• 28 structures
• Sized: approx. 80 ft. x 30 ft P
ark
boundary
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Deflector alternative – plan view
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Deflector alternative – x-section
Flows- Existing vs Deflector alternative
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Deflector alternative – Flow Model
11/17/2017 MRNP– Upper Nisqually Protection and Stabilization Project
Deflector alternative – Flow Model
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Deflector alternative – flow model
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Permits:• Pierce County – Shoreline conditional use permit, SEPA review
(submitted Jun. 2017)
• WDFW – Hydraulic Permit (HPA) (Jan. 2018)
• Ecology – Section 401 Water Quality Cert. (Jan. 2018)
• USACE – Section 404 Individual Permit (Jan. 2018)
• National Park Service – Construction Permit, NEPA review
Deflector alternative
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
Deflector alternative
9/15/2015
Questions?
MRNP– Upper Nisqually Protection and Stabilization Project
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017
MRNP– Upper Nisqually Protection and Stabilization Project11/17/2017