Design Documentation Report

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Design Documentation Report

Tolna Coulee

Advance MeasuresNelson County, North Dakota

Prepared By

US Army CorpsOf EngineersSt. Paul District / St. Louis District

July 2011 100% Submittal


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Table of Contents

1 Introduction ........................................................................................................................................... 1

1.1 Existing Project Description ......................................................................................................... 1

1.2 Current Conditions of Tolna Coulee ............................................................................................. 1

1.3 Purpose .......................................................................................................................................... 2

1.4 Authorization ................................................................................................................................ 2

2 Project Features ..................................................................................................................................... 2

2.1 Overview ....................................................................................................................................... 2

2.2 Sheet Pile I-Wall ........................................................................................................................... 2

2.3 Embankments ................................................................................................................................ 2

2.3.1 Embankments next to I-wall. ................................................................................................ 2

2.3.2 Embankment north of the Control Structure ......................................................................... 3

2.4 Control Structure ........................................................................................................................... 3

2.5 Riprap Erosion Protection ............................................................................................................. 3

2.6 Access Road .................................................................................................................................. 3

2.7 Cofferdams .................................................................................................................................... 3

2.8 Previously Obtained Data ............................................................................................................. 4

2.8.1 Topographic Data .................................................................................................................. 4

2.8.2 Property Line Data ................................................................................................................ 4

2.8.3 Related Construction Projects ............................................................................................... 4

2.9 Property Acquisitions and Adjacent Properties ............................................................................ 4

3 PERTINENT DATA ............................................................................................................................. 4

3.1 Controlling Elevations .................................................................................................................. 44 PREVIOUS REPORTS ........................................................................................................................ 5

5 Hydrology and Hydraulics .................................................................................................................... 5

5.1 Introduction ................................................................................................................................... 5

5.2 Straight Drop Structure ................................................................................................................. 5

5.3 Stilling Basin ................................................................................................................................. 6

5.4 Composite I-Wall/Embankment ................................................................................................... 6

6 Geotechnical Engineering ..................................................................................................................... 7

6.1 General .......................................................................................................................................... 7

7 Civil Engineering .................................................................................................................................. 77.1 Introduction ................................................................................................................................... 7

7.2 Technical Guidelines and References ........................................................................................... 7

7.3 Source of Data for Existing Topographic Information ................................................................. 8

7.4 Programs and Standards for Design and Drawings ....................................................................... 8

7.5 Design Process and Standards for Civil Features ......................................................................... 8

7.5.1 Geometric Design Criteria Access Road ............................................................................ 8


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7.6 Engineering Drawings for Embankments and Site Work ............................................................. 8

7.7 Phase 1 Environmental Site Assessment....................................................................................... 9

8 Structural Engineering .......................................................................................................................... 9

8.1 General .......................................................................................................................................... 9

8.2 Structure Design ............................................................................................................................ 9

8.2.1 Stoplog Control Structure ..................................................................................................... 9

8.2.2 Retaining Walls and Wing Walls .......................................................................................... 9

8.2.3 Sheet Pile I-wall .................................................................................................................... 9

8.2.4 Walkway ............................................................................................................................. 10

8.2.5 Gantry Crane ....................................................................................................................... 10

8.2.6 Lifting Beam ....................................................................................................................... 10

8.2.7 Stoplogs ............................................................................................................................... 10

8.3 Miscellaneous ............................................................................................................................. 10

8.3.1 Frost Protection ................................................................................................................... 10

9 Mechanical and Electrical Engineering .............................................................................................. 10

9.1 Mechanical Design ...................................................................................................................... 10

9.1.1 Gantry Crane and Hoist Selection ....................................................................................... 10

9.2 Electrical Design ......................................................................................................................... 11

10 Constructability ................................................................................................................................... 11

10.1 Introduction ................................................................................................................................. 11

10.2 Sequence of Construction ........................................................................................................... 11

10.3 Embankments .............................................................................................................................. 11

10.4 Structure ...................................................................................................................................... 11

10.5 Coordination with Other Agencies ............................................................................................. 11

11 Instrumentation ................................................................................................................................... 11

11.1 Monitoring Points ....................................................................................................................... 11

11.2 Construction Monitoring ............................................................................................................. 11

11.3 Long-Term Performance Monitoring .......................................................................................... 11

12 Cost Estimate and Construction Schedule .......................................................................................... 11

12.1 Cost Estimate .............................................................................................................................. 11

12.2 Construction Schedule ................................................................................................................ 12

13 REVIEW DOCUMENTATION ......................................................................................................... 12

13.1 District Quality Control (DQC) Review ..................................................................................... 1213.2 Agency Technical Review (ATR) ............................................................................................... 12

13.3 Independent External Peer Review (IEPR) ................................................................................. 12


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Appendices

Appendix A Plan Set

Appendix B Specifications

Appendix C Hydrology/Hydraulic Appendix

Appendix D Geotechnical Appendix

Appendix E Structural Appendix

Appendix F Mechanical Appendix

Appendix G Quantities

Appendix H Cost Estimate and Construction Schedule

Appendix I Engineering Considerations and Instructions for Field Personnel

Appendix J Phase I Environmental Site Assessment

Appendix K Quality Control Documentation


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1 INTRODUCTION

1.1 Existing Project Description

Devils Lake is a natural lake located south of the City of Devils Lake, located in Ramsey County in the

northeast portion of North Dakota. Since 1940 the lake has risen fifty-two feet, with almost twenty-nine feet of rise since 1993. In March 1993 Devils Lake had a surface area of 44,230 acres. At its

April 30, 2010 elevation (1452.63feet NAVD88) Devils Lake covered about 177,100 acres. During that

same period the volume of water in Devils Lake had grown by more than six times. The current lake

elevation (May 11, 2011) is 1454.0 feet. All elevations in this report are in feet and referenced to

North American Vertical Datum of 1988 (NAVD88) unless specifically stated otherwise. The

conversion from NAVD88 to National Geodetic Vertical Datum of 1929 (NGVD29) in the area of this

project is: NGVD29 = NAVD88 -1.17 feet.

Devils Lake naturally spills into Stump Lake (located east of Devils Lake) at an elevation of

approximately 1447.7. Since water began flowing into Stump Lake in 1999, Stump Lake has now

been filled and has become part of Devils Lake. At its current water levels, Devils Lake has no natural

outlet. At an elevation of 1459.2 the lake overtops the high point in Tolna Coulee and begins to spillthrough the coulee into the Sheyenne River, a tributary of the Red River of the North. Tolna Coulee

is located at the southwest end of what was Stump Lake. Devils Lake has reached its spill elevation

and overflowed into the Sheyenne and Red Rivers at least twice during the past 4,000 years. The

lake last spilled into the Sheyenne River less than 2,000 years ago. At its spill elevation, Devils Lake

covers more than 261,000 acres.

The State of North Dakota completed construction of an outlet to allow water from the West Bay of

Devils Lake to flow into the Sheyenne River in the summer of 2005. The outlet is made up of two

pump stations, a series of buried pipelines and open channels, a sand filter, three siphons, a gated

control structure and a stilling basin. The original pump capacity of the system was 100 cubic feet

per second (cfs). Modifications to increase the pump capacity to 250 cfs were approved by the North

Dakota State Engineer in June 2010. Discharge from the outlet is limited by the 600 cfs channelcapacity of the upper Sheyenne River and the North Dakota Department of Healths maximum

allowed concentration level of 750 milligrams per liter of sulfate at the discharge point in the

Sheyenne River. The West Bay of Devils Lake is located on the other side of Devils Lake from the

Tolna Coulee project and is several miles from Tolna Coulee. This information is provided only for

situational awareness, since it adds flow to the Sheyenne River upstream of the confluence of Tolna

Coulee and the Sheyenne River.

At the time of this project, the State of North Dakota is planning to expand its west end pumped

outlet with an additional capacity of 100 cfs and construct an east end pumped outlet from East

Devils Lakewith a capacity of 350 cfs, which is currently planned to transport water to Tolna Coulee,just downstream of the high point in the coulee. The east end pumped outlet would be located in

the vicinity of the Tolna Coulee project, but would not impact the design of the Tolna Coulee project

since it would discharge into Tolna Coulee downstream of the project.

1.2 Current Conditions of Tolna Coulee

Tolna Coulee is a natural outlet from the Devils Lake basin. There is a significant layer of silts and

organic material with grassy vegetation at the bottom of Tolna Coulee that will have to be removed

before an embankment and/or or structure can be constructed. This layer of silt and organic material

varies in thickness to as much as 14 feet near the middle of the coulee. Under this soft material is a


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layer of sand and boulders, with stiff clay underneath. Due to the high ground water (at or near the

ground surface) and the seepage of groundwater from the sides of the coulee near the toe of the

coulee slopes, dewatering during construction will be required. Due to the rising lake level, a

cofferdam will be constructed on the east side of the project.

1.3 Purpose

The purpose of the Tolna Coulee project is to prevent catastrophic release of flows through Tolna

Coulee into the Sheyenne River. The State of North Dakota has also requested that the Corps of

Engineers include a control structure with the project to allow controlled discharge down to

elevation 1446 feet NGVD29 (1447.2 NAVD88). HQUSACE directed that Measures to control water

elevation or releases above or below 1458 will be borne by the non-Federal sponsor, including

engineering and design. (Note the elevation referenced in the HQ memo is referenced to NGVD29

Datum)

1.4 Authorization

The Tolna Coulee Advance Measures project is authorized under PL84-99, Flood Control and Coastal

Emergencies.

2 PROJECT FEATURES

2.1 Overview

The project includes: Construction of a sheet pile I-wall with a top elevation of 1467.2 (NAVD88), a

stoplog control structure with a stoplog crest elevation of 1459.2 and a top of concrete footing

elevation of 1447.2. The stoplog control structure includes concrete piers with 10 foot clear spacing

between them and a catwalk with overhead rail to allow removal of the stoplogs. Construction of

the sheet pile I-wall will require embankment to be constructed upstream and downstream of the I-

wall. The embankment on the west side of the sheet pile I-wall between and the north bank of the

coulee and the north end of the structure will be ramped up to elevation 1467.2 to allow access tothe structure.

2.2 Sheet Pile I-Wall

A sheet pile I-wall will extend from the south side of the structure to the south bank of Tolna Coulee

and from the north side of the structure to the north bank of Tolna Coulee. This I-wall will have a top

elevation of 1467.2 (NAVD88), which includes 4 feet of freeboard to limit wave overtopping to

acceptable levels. The I-wall on the north side of the structure will include an embankment which

ramps up to the same elevation as the sheet pile on the downstream side of the sheetpile to allow

access to the control structure.

2.3 Embankments

Embankment construction and design is consistent with District guidance. Due to winter time

construction, 24 hour operation will be required to reduce the issues with frozen material.

2.3.1

Embankments will be constructed on the upstream and downstream sides of the sheet pile I-wall.

These embankments are intended to reduce the stick-up of the I-wall to acceptable levels and

eliminate the need for a king pile system to support the sheet pile wall. The tops of these

Embankments next to I-wall.


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embankments will be at elevation 1461.2 south of the control structure and elevation 1463.2

north of the control structure.

2.3.2

An embankment will be constructed to elevation 1463.2 on both sides of the sheet pile I-wall. The

fill on the downstream side of the sheet pile will be ramped up to the full height of the sheet pile I-

wall to provide access to the control structure. The embankment on the upstream side of the

sheet pile will have a consistent top elevation of 1463.2.

Embankment north of the Control Structure

2.4 Control Structure

A control structure will be constructed near the middle of the coulee and will use stoplogs to control

water levels in the Devils Lake basin down to elevation 1447.2 (NAVD88). The control structure

includes a concrete footing/sill, concrete abutments and wing walls, 11 concrete piers with 10 foot

clear openings/bays, and a full length catwalk with overhead monorail system to allow removal of

the stoplogs. The catwalk will be designed to allow access with an ATV and a trailer or cart, which is

expected to be used to haul stoplogs off the structure.

2.5 Riprap Erosion ProtectionRiprap erosion protection will be placed both upstream and downstream of the structure. The riprap

on the lake side slopes of the embankment is sized for wave impact from Stump Lake.

2.6 Access Road

A permanent access road will be constructed from 33rd Street NE, down the hill to the structure. The

access road will be for maintenance purposes and to access the structure to remove stop logs. The

access road will have a maximum grade of 6% and it will be 20 wide with ditching along both sides.

Wide construction limits will be provided in the event the contractor wants to widen the road for

hauling materials to the project site.

2.7

Cofferdams

Due to the rising lake level, a cofferdam will be required on the east side (lake side) of the structure.

Since the work is expected to be completed in March, the lake is expected to be frozen for the

majority of the construction period, so riprap for erosion protection of the cofferdam will not be

required. A cofferdam design has been prepared to include in the plans as a suggestion and to assist

with preparation of estimates; however, the specifications will require the Contractor to design their

own cofferdam.

The cofferdam will not be the only line of protection from flows to the Sheyenne River and

downstream, as the existing Tolna Coulee high points will remain in place. Because the cofferdam

will be a non-critical structure, the actual height of the cofferdam will be up to the contractor and

will most likely depend on the contractors equipment protection needs. The contractor will submit a

cofferdam plan for USACE approval before the cofferdam is constructed.

The cofferdam and dewatering provides the dry working area needed to construct the embankments

under proper conditions or as near to proper conditions as can be expected in North Dakota in the

winter.


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2.8 Previously Obtained Data

2.8.1

Existing topographic data utilized for the design and drawings was from LIDAR and field survey

information performed by City of Devils lake when the maintenance excavation in the coulee was

performed. The project area was then surveyed manually by a State of North Dakota survey crewin May 2011. The coordinate system and projection of the topographic mapping data is NAD83

(2007), North Dakota State Plane Coordinate System, North Zone (U.S. Survey Feet). The elevation

datum of the topographic mapping data is NAVD88 (U.S. Survey Feet).

Topographic Data

2.8.2

The deed for the existing city owned property around the project site was supplied by the City of

Devils Lake.

Property Line Data

2.8.3

2.8.3.1 Devils Lake City Embankments, Phase 2B and Phase 3

Related Construction Projects

Levees near and around Devils Lake are being raised to an elevation of 1467.2. These projectsinclude levee raises, pump stations, and road raises and other work associated with protecting

the City of Devils Lake from the rising Lake Level. A design criterion for these projects was that

if a PMF occurred with an initial lake elevation of 1458.0, outflow through Tolna Coulee

(assuming no erosion) would limit the maximum lake elevation at Tolna Coulee to 1461.9. The

Tolna Coulee project must not increase the lake elevation for the PMF.

2.8.3.2 East Devils Lake Outlet

The North Dakota State Water Commission is planning to construct an outlet and channel from

East Devils Lake to Tolna Coulee. The route begins on East Devils Lake, runs east southeast 5-

1/2 miles and outlets into Tolna Coulee. The outlet will discharge into Tolna Coulee

downstream from the control structure. The outlet plan consists of a pumping plant with

several pumps with the total capacity of 350 cubic feet per second (cfs).

2.9 Property Acquisitions and Adjacent Properties

The City of Devils Lake owns the property that this project will be constructed on. All work is being

done within the property owned by the City of Devils Lake.

3 PERTINENT DATA

3.1 Controlling Elevations

The following table lists the finish elevations of key features of the project. All elevations shown

refer to NAVD88.

Table 3 1 Controlling Elevations

DESCRIPTION ELEVATION (NAVD88)

Top of Sheet Pile I-Wall 1467.2

Top of Berm North of Control Structure 1463.2*


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Top of Berm South of Control Structure 1461.2

Top of Sill at Stop Logs 1447.2

Top of Stoplogs 4 Center Bays 1458.2

Top of Stoplogs 8 Remaining Bays 1459.2

*A ramp will be constructed on the north side of the structure on the west side of the sheet pile I-

wall to allow access to the catwalk. The earth ramp will be from elevation 1463.2 to elevation

1467.2.

4 PREVIOUS REPORTS

Tolna Coulee Outlet Erosion Report, Barr Engineering, Inc., For: U.S. Army Corps of Engineers,St. Paul District, 2001.

Project Information Report, Advance Measures, Tolna Coulee, Nelson County North Dakota,U.S. Army Corps of Engineers, St. Paul District, Revised 22 March 2011.

5 HYDROLOGY AND HYDRAULICS

5.1 Introduction

Levees near and around Devils Lake are being raised to an elevation of 1467.2 ft. These projects

include levee raises, pump stations, and road raises and other work associated with protecting the

City of Devils Lake from the rising Lake Level. The top of embankment for these levee designs is

predicated on Tolna Coulee flowing into the Sheyenne River when the lake level at Tolna Coulee

exceeds elevation 1459.2 ft.

The following paragraphs provide a summary of the Hydraulic Design considerations for the Tolna

Coulee Project. Detailed information related to the Hydrology and Hydraulic design of the Tolna

Coulee Project can be found in the Hydrology/Hydraulics Appendix (Appendix C).

5.2 Straight Drop StructureIn consistency with flood protection efforts in the Devils Lake sub-basin, including the City of Devils

Lake Embankments and Roads Acting as Water Barriers, the Tolna Coulee control structure is

designed for a Inflow Design Flood (IDF) of Probable Maximum Flood ( PMF) with the lake starting

at full pool (Elevation 1459.2 ft).

The PMF peak lake elevation at Tolna Coulee for Without Project condition assuming No-

erosion is 1463.2 ft with a peak discharge of approximately 3000 cfs. Design of the City of Devils

Lake Embankments is based on a peak lake level of 1463.2 ft at Tolna Coulee for a PMF inflow with

the lake starting at full pool (Elevation 1459.2 ft).

To cause no impacts to the design of the City of Devils Lake Embankments, the design discharge for

the structure at Tolna Coulee must not result in an increase to the peak still water level elevation

above 1463.2 ft at Tolna Coulee for a PMF inflow to Devils Lake on a starting pool elevation of


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1459.2 ft. This corresponds to a minimum peak discharge of approximately 3000 cfs at a PMF peak

lake elevation of 1463.2 ft. Selection of a design discharge exceeding 3000 cfs would not cause

impacts to the design of the City of Devils Lake Embankments. A target design discharge greater than

approximately 3000 cfs was not pursued, as action is required at downstream communities for flows

less than 3,000 cfs.

Based on the assessment that substantial erosion could precede peak lake elevation for the design

event, the weir structure is sized to pass approximately 3000 cfs under free flow conditions at a peak

lake elevation of 1463.2 ft. Steady state hydraulic modeling and analysis using HEC-RAS version 4.1.0

was conducted to develop rating curves for with and without project conditions assuming No-

Erosion. The PMF inflow of 1.44 million acre-feet was routed on a daily time step using a with

project rating curve to ensure the structure does not result in an increase to the peak water surface

elevation of 1463.2 ft.

Tailwater Depth (d2) for the Tolna Coulee structure is assumed to be variable from 5 feet to 17.2 feet

for the design event as Tolna Coulee erodes. Tailwater elevations for structural and geotechnical

analysis of different headwater and tailwater combinations are provided in Appendix C.

5.3 Stilling BasinFor the design water surface elevation of 1463.2 ft, stop-logs at 1458.2 ft and 1459.2 ft are designed

to pass 5 ft and 4 ft of total head respectively. Drop heights from stop logs at elevation 1458.2 ft and

elevation 1459.2 ft are 13.6 ft and 14.6 ft respectively. Stilling basin requirements were determined

by analyzing peak design head at each invert elevation for both high and low tailwater scenarios.

Basin dimensions were calculated using experimental results and design guidelines proposed by

Donnelly and Blaisdell in the technical paper, Straight Drop Spillway Stilling Basin. The floor of the

designed stilling basin is at elevation 1444.6 ft. The required stilling basin is 49.5 feet long with 43.5

feet between the straight drop and the baffle blocks. The 16-inch square baffle blocks occupybetween 50% and 60% of the total stilling basin cross sectional area.

5.4 Composite I-Wall/EmbankmentTo be consistent with the approved Devils Lake Flood Risk Management Project Design Criteria and

Project Considerations Report, a freeboard requirement of the maximum of 3 feet or wind/wave

requirements was adopted for the Tolna Coulee structure.

Wind and wave impacts were analyzed using Coastal Engineering Manual and Shore Protection

Manual methodologies. For the City of Devils Lake Embankments project, wave analysis and design

following Shore Protection Manual methodology required that wave run-up be contained by the

embankments. Because run-up does not apply to vertical structures, guidance for allowable

overtopping from the Coastal Engineering Manual was used.

For a lake level of 1463.2 ft, Wind Setup of 0.4 feet, and significant wave height of 3.3 feet - 4 feet of

freeboard (top of structure elevation of 1467.2 ft) is provided to ensure the structure does not

exceed a No Damage overtopping discharge of 0.1 cfs/ft for the design event.


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Riprap erosion protection is designed for locations on the Composite I-Wall/Embankment and

upstream and downstream of the spillway / stilling basin structure using applicable criteria.

6 GEOTECHNICAL ENGINEERING

6.1 General

This section provides the geotechnical engineering in support of the final design, specifications and

cost estimate for the Tolna Coulee Advance Measures project. The project includes: Construction of a

composite I-wall/embankment with a top elevation of 1467.2 (NAVD88), a stop log control structure

with a stop log crest elevation of 1458.2 for the 4 center bays and 1459.2 for the remainder of the

bays, and a top of concrete footing elevation of 1447.2. Construction of the sheet pile I-wall will

require embankment to be constructed upstream and downstream of the I-wall to limit stickup to

acceptable levels. An embankment with a top elevation of 1463.2 and will be constructed between

the north end of the structure and the north bank of the coulee, with a ramp to 1467.2 to allow

access to the structure. An embankment with a top elevation of 1461.2 and will be constructed

between the south end of the structure and the south bank of the coulee. Detailed information

related to the geotechnical design criteria, design cases, and other information related to

geotechnical design can be found in the Geotechnical Appendix (Appendix D).

7 CIVIL ENGINEERING

7.1 Introduction

This section summarizes the proposed layout, method of analyses, and support for preparation of

the plans, specifications, and cost estimate. The layout attempted to optimize the use of the existing

ground, avoid private property, and meet conditions needed to suit subsurface properties in an

effort to reduce overall cost. In specific, the civil portion of the project involved the design and

layout of embankments, site work, access roads, and site drainage. The embankment was utilized

around the structure and sheetpile to provide access, meet passive and uplift pressures, and

eliminate sliding of the structure. An embankment elevation of 1463.2 was followed on the north

side of the structure and an embankment elevation of 1461.2 was utilized on the south side of the

structure. A half mile long gravel road, turnaround, and parking spaces were designed to provide

access to the structure. In addition a storage yard was included for the storage of stop logs needed to

operate the closure structure. Lastly roadside ditching was utilized to convey drainage along its

natural path.

7.2 Technical Guidelines and References

1. A/E/C CADD Standard, Release 3.0; U.S. Army Engineer Research and Development Center,Vicksburg, MS; September 2006.

2. A/E/C CADD Standard Supplement, Release 6.2.0; U.S. Army Corps of Engineers, St. PaulDistrict; July 2004.

3. A Policy on Geometric Design of Highways and Streets, Fifth Edition; pp. 131-229, 231-234,and 380-389; American Association of State Highway and Transportation Officials

(AASHTO); 2004.


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4. United States National CAD Standard, Version 4.0; National Institute of Building Sciences;July 2009.

5. Guidelines for Geometric Design of Very Low-Volume Local Roads; American Association ofState Highway and Transportation Officials (AASHTO); 2001

7.3

Source of Data for Existing Topographic Information

Existing topographic data utilized for the design and drawings was from topographic LIDAR surveys

and field survey information performed by City of Devils lake. The project area has been surveyed

by a State of North Dakota survey crew in May 2011 and the data is in the process of being converted

for its use in the design. The coordinate system and projection of the topographic mapping data is

NAD83 (2007), North Dakota State Plane Coordinate System, North Zone (U.S. Survey Feet). The

elevation datum of the topographic mapping data is NAVD88 (U.S. Survey Feet).

7.4 Programs and Standards for Design and Drawings

The computer-aided drafting and design (CADD) program used for the drawings utilized MicroStation

V8i (Version 8.11, October 2008) and topographic data with INROADS generated TIN file, profiles,

and cross sections. All drawings adhered to national, Mississippi Valley Division, and St. Paul DistrictCADD standards.

7.5 Design Process and Standards for Civil Features

Roadway design was based on the standards included in AASHTOs 2004 bookA Policy on Geometric

Design of Highways and Streets (Reference 3) ) andAASHTOs 2001 book Guidelines for Geometric

Design of Very Low-Volume Local Roads (Reference 5).

7.5.1

The access road begins 800 feet West from the East edge of section 19 on 33rd Street NE at sta

0+00 and continues to the south through the natural swale to the project site. The alignment is

specifically designed to minimize earthwork and reduce vertical grades to acceptable levels. The

road is classified as a rural minor access road. The road surface consists of gravel at a width of 20

which includes the shoulders. The specific design information to design the horizontal curves are

as follows:

Geometric Design Criteria Access Road

Design speed 20 mph Design Stopping Sight Distance 115 ft Superelevation e=0 Side friction factor f=0.13

The vertical alignment of Tolna Coulee access road navigates a difference of 40 in elevation over

2500 feet in length approximately. The vertical profile of the road is as follows:

Design speed 20 mph Roadway max Slope -6.0% Design Stopping Sight Distance 115 ft Rate of Vertical Curvature, K = 7 for crest curves and K=17 for sag curves

7.6 Engineering Drawings for Embankments and Site Work

Drawings produced for the submittal utilized the following information:

LIDAR Topographic Survey Data


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City of Devils Lake Field Survey Data MicroStation V8i model and sheet seed files Design files including cross-sections, alignment, and TIN files USACE Standards

Civil engineering drawings and plans prepared concurrent with this report are included in AppendixA.

7.7 Phase 1 Environmental Site Assessment

The St. Paul District has performed a Phase I Environmental Site Assessment (ESA) in conformance

with the scope and limitations of American Society for Testing and Materials (ASTM) Practice E 1527-

05. The environmental site assessment has revealed no evidence of recognized environmental

conditions in connection with the subject properties.

8 STRUCTURAL ENGINEERING

8.1 General

The structural design of the Tolna coulee outlet project is comprised of five major components

stoplog control structure, including a walkway, overhead frame and monorail, pickup beam, and

stoplogs; upstream approach walls; downstream wing walls; and left and right bank I-walls. Detailed

information related to the structural design criteria, design loads, load cases, and other information

related to structural design can be found in the Structural Appendix (Appendix E).

8.2 Structure Design

Structural design of hydraulic structures is in accordance with EM 1110-2-2104 and EM 1110-2-2105

for reinforced concrete and structural steel, respectively. A single load factor of 1.7 plus hydraulic

factor of 1.3 are used for reinforced concrete. Structural design for non-hydraulic structures is in

accordance with ACI 318-05. The design of the walkway and other steel structural components are in

accordance with AISC Steel Construction Manual. Design information for the following structures can

be found in the Structural Appendix.

8.2.1

The stoplog control structure is an approximately 66-feet wide, 162-feet long and 26-feet high

reinforced concrete structure. The structure consists of reinforced concrete side walls with a

reinforced concrete slab in between. There are 11 reinforced concrete piers to support the

walkway and stop logs. A sheetpile cutoff is included along the entire perimeter of the slab and is

tied to the adjacent sheetpile I-walls.

Stoplog Control Structure

8.2.2

There are 2 retaining walls on each side of the control structure on the upstream side and two

wing walls on the downstream side of the structure.

Retaining Walls and Wing Walls

8.2.3

The sheet pile I-wall is designed as a cantilevered wall. The top of the sheet pile wall will be cut off

at the design elevation. A cap will not be installed on the sheet pile I-wall. The exposed height of

Sheet Pile I-wall


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the sheet pile on the south embankment is 6 feet. The exposed height of the sheet pile on the

north embankment is 4 feet.

8.2.4

A 5 foot wide (clear distance) walkway will be constructed across the entire width of the control

structure, and will be supported by the concrete piers. The walkway is intended to provide access

for inspection and for removal of the stoplogs. It must be wide enough to accommodate an ATV to

facilitate removal of the stoplogs.

Walkway

8.2.5

A gantry crane with V-shaped steel wheels will run on angle iron tracks for the length of the

walkway. The gantry crane will support the hoist and pickup beam.

Gantry Crane

8.2.6

A lifting beam will be required to facilitate removal of the stoplogs. The latching mechanism will

be designed to work with the welded studs on the sides of the stoplogs. The lifting beam and

stoplogs will be specified as a system to minimize chances of the stoplogs and lifting beam not

working properly.

Lifting Beam

8.2.7

The stoplogs will be constructed of steel and will be galvanized. Pickup will be by welded studs on

the sides of the stoplogs or by slots cut in the tops of the stoplogs.

Stoplogs

8.3 Miscellaneous

8.3.1

In general, a minimum of five feet of cover is maintained over the base of foundations for frost

protection.

Frost Protection

9 MECHANICAL AND ELECTRICAL ENGINEERING

9.1 Mechanical Design

Mechanical design for the control structure is limited to the gantry crane and hoist system to be used

for removal of stop logs.

9.1.1

The control structure will be equipped with a gantry crane and hoist system to remove the

stoplogs from the stoplog slots.

Gantry Crane and Hoist Selection

The selected components include a gantry crane, and a manually operated chain hoist. Thegantry crane will ride on steel V-shaped wheels to allow easy travel without electric power. The

gantry crane will include a transverse I-beam to allow the hoist to travel sideways within the

frame since the stoplog slots are off-set from the centerline of the walkway. The manually

operated chain hoist was selected due to the lack of electric power at the site.

Gantry crane and hoist information, including loads used in the structural design and structural

calculations are presented in Appendix E.


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11

9.2 Electrical Design

There is no electrical power at the site and there is no need for electric equipment or lights. The

hoists to be used to remove the stop logs are hand powered and all maintenance work and stop log

removal can be done during daylight hours so there is no need for lighting. If observation is needed

at night, portable light plants can be brought in to provide the necessary light.

10CONSTRUCTABILITYInformation will be added to this section prior to the BCOE submittal.

10.1 Introduction

The compressed schedule for design and construction of the project resulting from the rising lake

levels will require that the majority of this project be constructed in the winter.

10.2 Sequence of Construction

10.3 Embankments

Due to the plan to construct the majority of this project during the winter months, an effort has been

made to minimize earthwork and limit the compaction requirements for embankment. For the

earthwork that is required, 24 hour operation during construction will be required to minimize issues

with freezing of the fill between lifts.

10.4 Structure

10.5 Coordination with Other Agencies

11INSTRUMENTATION

Information will be added to this section prior to the BCOE submittal.

11.1 Monitoring Points

11.2 Construction Monitoring

11.3 Long-Term Performance Monitoring

12COST ESTIMATE AND CONSTRUCTION SCHEDULE

12.1 Cost Estimate

The cost estimate was prepared using MCACES Second Generation (MII) software, version 3.1, Build2. The cost estimate is based on the acquisition plan, which includes the use of an IFB restricted to

small businesses. As such, it includes a subcontracting plan and prime contractor overhead rate that

would be likely for a small business. Productivity was adjusted within the estimate for certain items

to account for the impacts of cold weather and snow due to the requirement to complete the

majority of this project during the winter months. Contingencies were developed using the

abbreviated risk analysis spreadsheets developed by the Corps of Engineers Cost DX.


16/317

12

12.2 Construction ScheduleA construction schedule was developed for the project that shows that the project can be

constructed by March 12, 2012, assuming a NTP of 7 October 2011. This schedule, however, does

not include time for weather days, meaning that the Contractor will be expected to work through the

winter weather and make accommodations to their operations and planning to account for the

expected severe weather. The schedule also shows that multiple crews will be required to completethe project on time.

13REVIEW DOCUMENTATION

13.1 District Quality Control (DQC) Review

Documentation will be added after the DQC review has been completed.

13.2 Agency Technical Review (ATR)

Documentation will be added after the ATR has been completed.

13.3 Independent External Peer Review (IEPR)

Documentation will be added after the IEPR has been completed.


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Appendix A

Plan Set

---

Provided Under

Separate Cover


18/317

Appendix B

Specifications

---

Provided Under

Separate Cover


19/317

Appendix C

Hydrology/Hydraulic Appendix


20/317


21/317

Tolna Coulee: H&H Appendix Page 2

TolnaCouleeControlStructure

FunctionoftheTolnaCouleeStructure:

Apreliminaryanalysis,TolnaCouleeOutletErosion(BARREngineering,2001)(Reference1),examined

both

the

hydraulic

and

the

geotechnical

parameters

of

Tolna

Coulee.

The

preliminary

analysis

indicates

thatgiventhenatureofthesoils,thereisahighpotentialforsevereerosiontooccur. Erosioncould

significantlyincreasetheoutflowthroughthecouleeintheeventofanaturaloverflowduetothelarge

volumeofwaterstoredinthelake. Ananalysiswasdoneonthepotentialoutflowassociatedwiththe

ProbableMaximumFlood(PMF). Theanalysisassumesaninitialfullpoollakeelevationof1459.2

ft. Table1comparesthepeakandsustainedoutflowsforthePMFassumingnoerosionofthecoulee,

andwitherosion.

Table1a:TolnaCouleeNaturalCondition(NoProject)OutflowComparison

SummaryStatistic NoErosion Erosion

PeakElevation 1463.2 1462.7

Peak

Outflow

(cfs)

3,000

14,000

Daysabove2,500cfs 51 136

Daysabove12,000cfs 0 19

Volumeinfirst180days(acreft.) 592,000 1,833,000

Volumeinfirst365days(acreft.) 982,000 2,379,000

Assumptions:

a)StartingWSEL=1459.2ft

b)Inflowvolume=1/2ProbableMaximumFlood(PMF)(1,440,000acreft.)

Table1ashowsuncontrolledflowsassociatedwitherosioncouldexceed12,000cfsforapproximately19

dayswithapeakoutflownear~14,000cfsinTolnaCoulee.

ThestructuredescribedinthisdocumentistobelocatedupstreamofthenaturalhighpointofTolna

CouleenearStumpLake(Figure1b). Shouldthedownstreamhighpointerode,causingacapacityofthe

highpointtoexceedapproximately3000cfsattheProbableMaximumFlood(PMF)lakeelevation

of1463.2ft,thecontrolstructurerestrictspeakflowstolessthanwouldhaveoccurrednaturally. Stop

logsareincludedinthestructuretoallowforacontrolledloweringofthelake. Stoplogswouldbe

removedtomatchnaturaldownstreamerosiontoamaximumflowrateofapproximately3000cfs. The

samevolumeofwaterthatwouldevacuatethelakewithouttheprojectshouldbeallowedtoevacuate

thelakeoveralongerduration.

ASAFTypestraightdropstillingbasin,inaccordancewithdesignguidelinesproposedbyDonnellyand

Blaisdell(1954),hasbeendesignedforenergydissipationimmediatelydownstreamofthestructure.

Forthe

SAF

straight

drop

spillway

stilling

basin,

Water

falling

over

the

spillway

crest

falls

onto

aflat

apron. Thenappeisbrokenupbyfloorblocks,whichalsopreventdamagingscourofthedownstream

channelbanks. Scourofthedownstreamchannelbedispreventedbyanendsill. Flaringwingwalls,

triangularinelevation,preventerosionofthedamfill(Reference2).


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0 10000 20000 30000 40000 50000 60000 1340

1360

1380

1400

1420

1440

1460

1480

Channel Distance (ft)

Elevation

(NAVD

1988)(ft)

Highway

15

TolnaDam

RailroadEmbankment

CountyR

oad24

98thAvenueNE

CountyR

oad4

3 2 n d S t r e

e t N E

Sheyenne River

Natural High

Figure 1b: Tolna Coulee Profile - Devils Lake to the Sheyenne River


23/317


StructureType:

DesignoftheDevilsLakeTolnaCouleecontrolstructurefollowstheguidelinesforaSaintAnthony

Falls(SAF)StraightDropStructureoutlinedinthearticleStraightDropSpillwayStillingBasinby

DonnellyandBlaisdell(Reference2). TheSAFstructurewasselectedinlieuofaCaliforniaInstituteof

Technology(CIT)structure(Reference3),asthemaximumdesigndropheight/criticaldepthvalueof

5.5fortheTolnaCouleestructureliesoutsideofexperimentallytestedvaluesforaCITstructure

(Reference4). TheSAFstillingbasincanbeusedforawiderangeofdischarge,headonthecrest,crest

length,heightofdrop,anddownstreamtailwaterlevel[s](Reference1). Historyofhighlyvariablelake

levels,potentialforerosionofthenaturalhighpointdownstreamofthestructure,andintended

operationmakeitcriticalthatthestructurebeabletoperformoverawiderangeofscenarios.

SelectionofInflowDesignFlood(IDF):

InconsistencywithfloodprotectioneffortsintheDevilsLakesubbasin,includingtheCityofDevilsLake

EmbankmentsandRoadsActingasWaterBarriers,theTolnaCouleecontrolstructureisdesignedfora

InflowDesignFlood(IDF)ofProbableMaximumFlood(PMF)withthelakestartingatfullpool

(Elevation1459.2

ft).

Information

related

to

the

accepted

PMF

event

at

Devils

Lake

is

contained

in

the

DevilsLakeFloodRiskManagementProjectDesignCriteriaandProjectConsiderationsReport

(Reference5).

DesignDischarge:

Thedesignwatersurfaceelevationof1464.2ftfortheCityofDevilsLakeEmbankmentsisbasedona

PMFinflowvolumeof1.44MillionAcreFeetwithafullpoolstartinglakeelevationof1459.2ft. The

PMFpeaklakeelevationatTolnaCouleeassumingnoerosionis1463.2ftwithanapproximatepeak

dischargeof3000cfs. ThedesignwatersurfacefortheCityofDevilsLakeEmbankmentsassumes1

footoflakeslopefromtheCityofDevilsLakeEmbankmentstotheoutflowatTolnaCoulee.

TocausenoimpactstothedesignoftheCityofDevilsLakeEmbankments,thedesigndischargeforthe

structureatTolnaCouleemustnotresultinanincreasetothepeakstillwaterlevelelevationabove

1463.2ftatTolnaCouleeforaPMFinflowtoDevilsLakeonastartingpoolelevationof1459.2ft. This

correspondstoaminimumpeakdischargeofapproximately3000cfsatthePMFpeaklakeelevation

of1463.2ft. Selectionofadesigndischargeexceeding3000cfswouldnotcauseimpactstothedesign

oftheCityofDevilsLakeEmbankments. Atargetdesigndischargegreaterthanapproximately3000cfs

wasnotpursued,asactionisrequiredatdownstreamcommunitiesforflowslessthan3,000cfs.

ThereportTolnaCouleeOutletErosion(Reference1)describeserosionofTolnaCouleeinitiatingat

thedownstreamslopeofthenaturalhighpointandprogressingupstreamtowardthelake. Forthe

designevent,hydraulicroutingusingsedimenttransportanalysismethodsproposedbyColby

(Reference1)showsDevilsLakereachingpeakelevationafterthecouleehassubstantiallyeroded.Hydraulicroutinganderosionanalysiswascomputedonadailytimestepusingthespreadsheet

Devils_Lake_Run_ESO.xls.

Basedontheassessmentthatsubstantialerosioncouldprecedepeaklakeelevationforthedesign

event,theweirstructurewassizedtopassapproximately3000cfsunderfreeflowconditionsatalake

elevationof1463.2ft.


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StraightDropStructure:

Severalcombinationsofstartingstoplogelevationswithweiropeningsizeswereevaluatedthatwould

achieveadesigndischargeofapproximately3000cfs. Basedonprojectsponsorpreference,starting

stoplogelevationsbetween1458.2ftand1459.2ftwereselectedtocloselymatchexistinggradeofthe

highpointthalweg. Astartingelevationof1458.2ftfor4of12totalstoplogbaysensuresthatwateris

notinhibitedfrommovingtooroverthehighpointbetweenelevation1458.2ftand1459.2ftifallowed

byexistinggrade.

Usingtheweirflowequation(Equation1)andacoefficientofC=3.0(Reference3),acombinedweir

lengthof40feetat1458.2ftand80feetat1459.2ftresultsinaflowrateofapproximately3000cfsata

lakeelevationof1463.2ft.

1 Q C L H

QMF 3.080ft1463.2 ft 1459.2 ft

3.040ft1463.2 ft 1458.2 ft

3262 cfs 3000 cfsWeirlength,discharge,andassociatedratingcurvesweredeterminedusingthe

FreeFlow_RatingCurve_CalculatortaboftheUpstream_Structure_Analysisdesignspreadsheet.

Aratingcurvefortheweirstructureunderfreeflowconditions,anticipatedgivensufficienterosionof

thecoulee,isshowninTable2. TheratingcurveforthestructurefortheNoErosionorPreErosion

scenarioisshowninTable3. TheNoErosionratingcurveshowninTable3wasinterpolatedfrom

watersurfaceprofilesthatweredevelopedusingTolnaCoulee_Upstream_Structure_12gates.g07

(Plan:TolnaCoulee_12_Gates)

from

the

HEC

RAS

model

TolnaCoulee.

Profiles

were

developed

using

steadyflowanalysisinHECRASversion4.1.0.

Table2: StructureFreeFlowRatingCurve Table3:StructureNoErosionRatingCurve


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HECRASModelandNoErosionAnalysis:

ThegeometryfileTolnaCoulee_Upstream_Structure_12gates.g07(Plan:TolnaCoulee_12_Gates)from

theHECRASversion4.1.0ModelTolnaCouleewasusedtoanalyzetheweirstructure. Steadystate

modelresultswereusedtoverifythatthestructuredoesnotresultinanincreasetothepeakStillWater

Level(SWL)of1463.2ftatTolnaCouleeforthePMFeventusedtodesigntheCityofDevilsLake

embankments.

TheTolnaCouleecontrolstructurewasmodeledasanInlineStructurewithtwelve10footoverflow

gates(InvertElevations:8at1459.2ft,4at1458.2ft)havingaweircoefficientofC=3.0. Overflowgates

areseparatedby2footpiers. Ineffectiveareasassumeexpansionandcontractionratiosof1:1.

Contractionandexpansioncoefficientsaresetto0.3and0.5respectivelyforcrosssectionsadjacentto

thestructuretorepresentcontractionofflowfromthewiderlakecrosssectionstothenarrowercontrol

structure. AcrosssectionviewofthestructureisshowninFigure4.

Figure4:CrossSectionViewofTolnaCouleeStructureModeledUsingHECRAS

WatersurfaceprofilesfortheweirstructureassumingNoErosionweredevelopedusingtheHECRAS

model. AratingcurvefortheweirstructureassumingNoErosionwasinterpolatedat1footelevation

intervalsfromwatersurfaceprofilesattheupstream(DevilsLake/StumpLake)endofthemodel. The

PMF

inflow

event

on

a

starting

lake

elevation

of

1459.2

ft

was

routed

through

the

interpolated

rating

curve(Table3)onadailytimestepusingthespreadsheetDevils_Lake_Run_ESO. Figure5onthe

followingpageshowslakeelevationvs.timeforwithandwithoutprojectconditionsforthedesign

eventassumingNoErosion.

RoutingthedesigneventassumingNoErosiondoesnotresultinasignificantincreasetothePMF

designwatersurfaceelevationof1463.2ftatTolnaCoulee. ForaPMFpeaklakelevelof1463.2ftat

TolnaCoulee,assuming1footoflakeslopefromTolnaCouleetotheCityofDevilsLakeEmbankments,

thedesigneventpeakwatersurfaceremains1464.2ftfortheCityofDevilsLakeEmbankments.


26/317

1,462

1,463

1,464

n(NAVD

1988Ft)

TolnaCouleeElevations(NAVD1988ft)forthe1/2PMF

NoErosion W.S.WithProject

NoErosion W.S.WithoutProject

Summ

NoEroPeakWWithPr

Withou

1,459

1,460

1,461

0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570

Elevati

DaysMar

Apr

May

Jul

Jun

Aug

Sept

Oct

Nov

Jan

Dec

Feb

May

Jul

Jun

Aug

Sept

Oct

Figure 5: Tolna Coulee Water Surface Elevations for the 1


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StillingBasinDesign

Forthedesignwatersurfaceelevationof1463.2ft,stoplogbaysat1458.2ftand1459.2ftareexpected

tooperateunder5feetand4feetoftotalheadrespectively. SAFstillingbasindimensionsare

dependentuponcriticaldepthanddropheight. Astillingbasinwassizedforbothstartingstoplog

elevations,withtherecommendedbasindimensionsselectedforthemostseverecase.

DesignguidancefortheSAFstructurestatesthatthestillingbasinlengthcomputedforaminimum

tailwaterlevelrequiredforgoodperformancemaybeinadequateathighertailwaterlevels. Dangerous

scourofthedownstreamchannelmayoccurifthenappeissupportedsufficientlybyhightailwaterso

thatitlandsbeyondtheendofthestillingbasin(Reference2).

Becausetailwaterisanticipatedtobevariableforthedesignevent,fromabovetheweirinverttobelow

theinvert,stillingbasindesignwasconductedforbothhightailwater(1463.2ft)andlowtailwater

(1451.2ft)scenarios. Stillingbasindesignwasconductedusingthedesignspreadsheet

SAF_StraightDrop_Design.xlsx. Designdimensionsthatwillperformforhigh,low,andintermediate

tailwaterscenarioswereselected. CriticalhydraulicdimensionsforthestillingbasinareshowninTable

6. Baffleblocksarespacedtoensurethatbetween50% 60%ofthebasincrosssectionalareaisblocked,asrecommendedinthedocumentStraightDropSpillwayStillingBasin(Reference2).

ThetoeoftherequiredIWall/Embankmentcompositesystemextendsfurtherdownstreamthanthe

endofthestillingbasinandwingwallsrequiredforhydraulicperformance. Lengtheningthestilling

basinbymovingtheendsillfurtherdownstream andchangingthewingwallslopetogradewere

requiredtofacilitatesitelayoutandensurethewingwallsretainallembankmentfill. Lengtheningthe

stillingbasinwasconductedinaccordancewithStraightDropSpillwayStillingBasin(Reference2).

Modificationstothewingwallsfollowthethedesignguidelinesoutlinedin,HydraulicDesignoftheBox

InletDropSpillway(Reference17).


28/317


Table6:DesignDimensionsforTolnaCouleeSAFTypeStructure

DesignrecommendationsforSAFstructuresprovidedbyRiceandKadavy(Reference15)suggestadding

aradiustransitionfromtheheadwalltotheweir. Addingtheradiustransitionreducesflow

concentrationatthecenteroftheweir,resultinginlesslocalizedscourdownstreamofthebasin.

ExperimentaltestresultspresentedinRiprapDesignDownstreamofStraightDropSpillways(Reference15)recommendaradiusofatleast3dctorealizemaximumbenefitsoftheradiustransition.

Basedondc(criticaldepth)of3.3feetforstoplogbaysatelevation1458.2ft,a10footradiustransition

fromtheabutmentstotheweirwasincorporatedintothedesignoftheconcretestructure.

TailwaterAssumptionsandLoadCaseDetermination

TailwaterDepth(d2)fortheTolnaCouleestructureisassumedtobevariablefrom5feetto17.2feetfor

thedesigneventasTolnaCouleeprogressivelyerodes. Thefollowingtailwaterelevationswere

providedforanalysisandloadcaseformulation:

TailwaterElevation:

1451.8

ft

Atailwaterelevationof1451.8ftcorrespondstoanerodedTolnaCouleechannelhavingathalwegat

elevation1447.2ft. ThedepthwasdeterminedusingManningsequationforuniformflowwithsomeof

theerosionassumptionsoutlinedinthereportTolnaCouleeOutletErosionbyBARREngineering

(Reference1). ParametersusedforanalysisareshowninTable7.


29/317


Table7:ManningsEquationParameters

Tailwater Analysis Parameters

Channel Slope (ft/ft) 0.00126

Channel Bottom Width (ft) 150

Manning's Roughness (n) 0.035

Channel Side SlopesHorizontal 1.5

Vertical 1

TailwaterElevation:1448.4ft

Atailwaterelevationof1448.4correspondsto3000cfsflowingatcriticaldepth(dc)overthe142foot

wideendsillofthestillingbasin. Thiswasassumedtobethelowestreasonabletailwaterfor3000cfs

passingoverthestructure. Theelevationwasdeterminedusingtheequationforcriticaldepththrough

arectangularchannel(Equation2):

2 d Q

d

./ =2.4feet

TailwaterDepth=EndSillElevation+dc1446ft+2.4feet= 1448.4ft

TailwaterElevation:1450.8ft

Thecontrolstructurewasanalyzedforaheadwaterelevationequaltothetopofthewallelevationof

1447.2ft. Forthiscase,morethan3000cfswouldbepassingoverthestoplogs. Usingtheweir

equationwithaweircoefficientofC=3.0calculatesthat8,671cfspassesoverthestructure. Aflowrateof8,671cfsatcriticaldepthoverthe142footwideendsillofthestillingbasincorrespondstoa

tailwaterelevationof1450.8ft. Theelevationwasdeterminedusingtheequationforcriticaldepth

througharectangularchannel(Equation2):

2 d Q

d

./ =4.87feet

TailwaterDepth=EndSillElevation+dc1446ft+4.8feet= 1450.8ft


30/317


WindandWaveAnalysis

DesignWind

DesignwindspeedswereadoptedfromapproveddesigndocumentationfortheDevilsLakePhase3

Embankments. Thedesignwindanalysisusestenyearsofwinddata,fromJune1985to1995.Astudy

byBaker(Reference6)concludedthattenyearsofrecordisamplewhenlookingforwindpatterns.Theaverageofthemaximumannualwindspeedsovertenyearswasadoptedforeachwinddirection(Table

8).ThesearethesamewindspeedsadoptedfortheexistingCityofDevilsLakeembankments,which

havewithstoodthewindandwaveforcessinceconstructionin2004withoutanyissues. Awindrose

illustratingprevalentwinddirectionforthe1985to1995periodisshowninFigure9.

Table8:DevilsLakeAverageofMaximumAnnualWindSpeeds(mph)(19851995)

Figure9:WindRoseDevilsLakeAverageofMaximumAnnualWindSpeeds(mph) (19851995)


31/317


WindSetup

WindsetupbasedonaJuly2006MemorandumforRecord(Reference7).Windsetupascomputedby

theformulapresentedintheCEMishighlydependentonwaterdepth,makingtheassumedwater

depthcriticaltotheresultingwindsetupvalue. Foreaseofcomputation,themethodologycurrentlyin

usebytheStPaulDistrictatthelocksanddamsistoassumeaonetenthriseinthewatersurfacefor

everytenmilesperhourofwindspeed. Whilethismayseemoverlysimplistic,ithasworkedwellatthelocksanddamsandhasthebenefitofnotbeingwaterdepthdependant. Thismethodwasalsousedin

theapproveddesignoftheDevilsLakePhase3Embankments. Windsetupof0.4ftwasusedforthe

TolnaCouleecontrolstructure.

FetchLength,CriticalWindDirection,andWaveGeneration

Theeffectivefetchlengthwasdeterminedbymethodsdiscussedin339oftheShoreProtectionManual

(SPM)(Reference8). Fetchvectors,perpendicularwiththestructurealignmentandat3degreeoffsets

wereanalyzed. Theperpendiculardistancefromthestructuretotheupstreamshorelineis0.6Miles.

Theaveragefetchlengthof9radialsspacedat3degreesisapproximately1.8miles.Themaximumfetch

vectoris5milesandtheminimumfetchvectoris0.1miles. Afetchlengthof5mileswasselectedfor

design.

A

map

of

Stump

Lake

with

wind

fetch

vectors

is

shown

in

Figure

10.

Criticalfetchlengthsforthestructurecorrespondtowinddirectionsbetween45degreesand135

degrees. Awindof27.2MPHOverlandEastwasusedfordesign. Thecriticaldesignwindresultsin

WaveHeight(H)=3.3ft,WavePeriod(T)=3.5seconds,andWavelength(L)=62Ft. Designformulas

andcalculationsrelatedtoWind/Wavedeterminationsarecontainedinthespreadsheet

TolnaCoulee_WindWave.xlsx.

FreeboardRequirements

Typically,DamSafetyCriteriaER111082(FR)(Reference9)requires5feetoffreeboardfor

embankmentdams. TobeconsistentwiththeapprovedDevilsLakeFloodRiskManagementProject

DesignCriteriaandProjectConsiderationsReport(Reference5),afreeboardrequirementofthe

maximumof3feetorwind/waverequirementswasadoptedfortheTolnaCouleestructure.

FortheCityofDevilsLakeEmbankmentsproject,waveanalysisanddesignfollowingShoreProtection

Manualmethodologyrequiredthatwaverunupbecontainedbytheembankments. Becauserunup

doesnotapplytoverticalstructures,guidanceforallowableovertoppingfromtheCoastalEngineering

Manualwasused.

TheIWall/EmbankmentcompositestructurewasanalyzedusingtheovertoppingformulabyFrancoand

Franco(1999)fromTableVI513oftheCoastalEngineeringManual. Foralakelevelof1463.2ft,Wind

Setupof0.4feet,andsignificantwaveheightof3.3feet:

OvertoppingDischarge(q) 0.1cfs/ft foratopofsheetpileelevationof1467.2ft.

Elevation1467.2ftis4feetabovetheStillWaterLevel(SWL)of1463.2ftforthedesignevent.

TableVI56:CriticalValuesofAverageOvertoppingDischargesfromtheCoastalEngineeringManual

(Reference10)showsthatq 0.1cfs/ftfallswithinthestructuralsafetylimitsfor"NoDamage"for

GrassSeaDikes. Anyadditionalerosionresistancetowaveovertoppingprovidedbyrockonthe

downstreamslopeoftheembankmentwasnotconsideredindeterminationoftheappropriate"No

Damage"threshold.


32/317

5

4.9

4.6

0.6

0.4

0.1

Map Legend

Perpendecular Fetch Vector

Fetch Vectors

Lake Extent at 1459.2 ft (NAVD 1988)

Lake Extent at 1463.2 ft (NAVD 1988)

Tolna Coulee : Control Structure - Wind / Wave Impacts

/0 1 20.5 1.5 Miles

Perpend icular Fetch Lengt h: 0.6 Miles

Average Fetch Length ( SPM) : 1.8 M iles

Maxim um Fetch Length : 5 Miles

ure 10: Stump Lake Fetch Map


33/317


IceImpacts

AmajorityofDevilsLakeinflowandassociatedlakeriseoccursinthelatespringandsummer(April

July). Icejammingisnotanticipatedtobeamajorproblemduringthemajorityoftheinfloweventdue

towarmweatherconditions. Forthe4monthPMFdesignevent,iceisnotanticipatedtorestrictor

preventflowfromleavingthelakeforadurationthatwouldresultinasignificantincreasetothedesign

watersurface

elevation

of

1463.2

ft.

The

structure

is

designed

for

ice

loading

where

applicable.

Piers

aredesignedassumingicecouldpotentiallybridgebetweenpiersthusincreasingiceload. Stoplogsare

designedforiceloadswhenbridgingisnotoccurring.RiprapDesign

Gradations

RiprapgradationsthatwereestablishedfortheCityofDevilsLakeEmbankmentswereadoptedforthe

TolnaCouleestructure. Thesegradationswereadopted,astheyhavealreadybeendevelopedandwill

beinuseintheareaaroundthetimeofconstruction. Summarystatisticsforeachofthegradations

selectedfor

the

project

are

shown

in

Table

11.

Further

information

related

to

graded

riprap

and

beddingcanbefoundinthespecificationsandgeotechnicaldesigndocumentation.

Table11:RiprapSummaryStatisticsforTolnaCouleeGradations

UpstreamEmbankmentProtection

RockprotectionontheupstreamslopeandcrownoftheembankmentwasdeterminedusingEquation

216:ArmorUnitStabilityfromEM111021614(Reference11). Designcalculationsarecontainedin

thespreadsheetTolnaCoulee_WindWave.xls.

ThestabilitycoefficientusedincalculationofstonesizewasadoptedfromSpiritLake(DevilsLake),

NorthDakota,Phase2EvaluationofExistingRoads(Reference12). Accordingtothatdocument,StabilitycoefficientsforavariousarmorunitsareshownintheSPM. Astabilitycoefficientfora

graded,roundedripraphasneverbeendetermined. Foratriplelayerofsmoothroundedstone,the

stabilitycoefficient

is

3.2.

For

adouble

layer,

its

2.4.

Continuing

with

this

thought,

avalue

of

1.6

was

assumedforasinglelayerofagradedriprap.

Stonesizecalculationfortheupstreamembankmentslopeandcrownassumesasinglelayerofrounded

riprapwithaunitweightof165poundspercubicfoot(pcf)andaspecificgravityof2.65. Calculated

minimumW50fortheupstreamslopeandcrownoftheIWall/Embankmentcompositesystemsisshown

inTable12.


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Table12:MinimumD50SizeforTolnaCouleeLakesideEmbankmentSlope RoundGradedRiprap

Slope of Embankment ( _H:1V) 3.5

Minimum W50 Rock Weight (lbs): 228

BasedonthecalculatedminimumW50size,Gradation4wasselectedforuseontheupstreamslopeand

crownoftheIWall/Embankmentcompositesystem.

DownstreamEmbankmentProtection

Establishingandmaintaininggrasscoveronthedownstreamslopeandcrownoftheembankment

presentschallenges,astheembankmentwillbeunderwaterforlakeelevationsabove~1453ftpriorto

anyerosionofthenaturalhighpoint. ThedownstreamcrestandslopeofthecompositeIWall/

Embankmentstructurewillbeprotectedwithrockinplaceofgrasstoeasemaintenanceofthe

structure.

Determinationof

appropriate

rock

gradation

is

based

on

the

Minnesota

PCA

Technical

Criteria

Riprap

CriteriaforStabilizationPonds(Reference16). Theguidancewasdevelopedbecause,grasscannot

usuallybeestablishedinoneseasontoadequatelyprotect[stabilizationpond]dikesfromerosion. The

fluctuatingwaterlevelsinapondsoperationarenotconducivetogoodgrassgrowth(Reference16).

TheriprapgradationrecommendedintheMinnesotaPCAdocumentissimilartoandslightlysmaller

thanGradation1.

Gradation1wasselectedforthedownstreamslopeandcrownoftheIWall/Embankmentcomposite

system. Additionalerosionresistancetowaveovertoppingprovidedbytherockwasnotconsideredin

determinationoftheappropriate"NoDamage"threshold.

RockDownstreamofEndSill

RiprapW50sizedeterminedforrockdesignimmediatelydownstreamofthestillingbasinisbasedon

experimentallyderivedguidancepresentedintheASAEpublication,RiprapDesignDownstreamof

StraightDropSpillways(Reference15).

DesignformulascalculateaminimumW50rocksizeasafunctionofcriticaldepth,dropheight,tailwater

depth,andabutmenttype. Becausethetailwaterdepthdownstreamofthestructureisexpectedtobe

variableforthedesigneventasthecouleeerodes,thecriticaldepth,dropheight,andtailwater

combinationyieldingthelargestminimumW50sizewasusedforrockdesign. DesignbasedontheASAE

guidancewasconductedusingthespreadsheetRiprapDesign_StraightDropSpillways.xlsx.

BasedonacalculatedminimumW50of61lb,Gradation3riprapwasselectedforscourprotection

immediatelydownstreamofthestillingbasinendsill.

RiprapDesignDownstreamofStraightDropSpillwaysrecommendsriprapprotectionofappropriate

sizebecontinuedaminimumdistanceof5dc(roundedabutments)to8dc(squareabutments)

downstreamoftheendsill. Thiscorrespondstoadistanceof16.5ftto26.5ftdownstreamoftheend


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sill. Hightailwaterelevationscancausescour[to]occurinthedownstreamchannelifthebedmaterial

iseasilyerodible,indicatingprovidedriprapprotectionshouldexceedminimumrequirements.

EM111021602(Reference14)recommendsthatriprapextenddownstreamforadistanceof10d2fromtheupstreamendofthestillingbasin. TailwaterDepth(d2)fortheTolnaCouleestructureis

assumedtobevariablefrom~5feetto~17.2feetforthedesigneventasTolnaCouleeerodes. Design

basedon

d2suggestsappropriatelysizedriprapprotectionbeplaced50172feetdownstreamofthe

startofthestillingbasin.

RiprapprotectionfortheTolnaCouleestructureisprovidedforatotalof100feetdownstreamofthe

stillingbasinexit. RiprapGradation3willbeplacedfor50feetdownstreamoftheendsillandaround

thewingwallstoresistlocalscour.

Gradation1riprapwillbeplacedfor50feetdownstreamofthelargerGradation3riprap. Transition

fromlargerocktoasmallerrockpriortotransitioningtothenaturalstreambedreduceslocallyhigh

boundaryturbulencethatwouldresultfromimmediatetransitionfromlargerocktothenaturalchannel

(Reference13). The50feetofsmallerrockalsoprovidesadditionalprotectionfromunderminingshould

downstreamerosion

progress

to

the

riprap

blanket.

Additional

rock

at

the

downstream

riprap

end

protectionsectionallowsforthesloughingofrockintoareasinneedofunderminingprotection.

Topelevationofthedownstreamriprapblanketwillbeat1444.6ft. Thiselevationislowerthanthetop

oftheendsillelevationof1446fttohelppreventbackrollersfrompullingrockintothebasinwhichcan

causeconcreteabrasiondamage. ThisisrecommendedinaccordancewithguidanceprovidedinEM

111021602(Reference14).

OperatingPlan

AfinaloperatingplanistobeprovidedbytheNorthDakotaStateWaterCommission(NDSWC)and

reviewedtoensurecompliancewithapplicableguidelinesandregulations. Generaloperatingplanrules

havebeendevelopedbytheNDSWCtoserveassummaryguidelinesforthefinaloperationplan.

1) Undernocircumstanceswillanystoplogsbeplacedaboveanelevationof1459.2feet.

2) Initiallythestoplogswillbeplacedapproximately1footbelowthewatersurface.

3) Asthewaterlevelincreasesstoplogswillbeaddedtomaintaintheapproximate1footlevelbelow

thewatersurfaceelevationuntilthetopofthestoplogsareatanelevationof1457.2feet.

4) Thetopofthestoplogswillremainat1457.2feetuntilwaterbeginstoflowoverthedivideatwhich

timethestoplogsinbays5through8willbeplacedtoelevation1458.2ftandbays14and912will

beplaceduptoelevation1459.2feet.

5) PriortoerosionofthedividebetweenStumpLakeandTolnaCoulee,thestoplogswillremainin

placeasdescribedin1.4,withtheintentthattheexistingtopography,notthecontrolstructurewill

controlthe

discharge.

6) Ifandwhenerosionoccurs,stoplogswillberemovedtotheerodedhighpointelevationwiththe

maximumlakedischargelimitedto3,000cfs.

7) Stoplogswillberemovedtothenewelevationthatexistsaftererosionhasoccurred. Thiswillbe

conductedinamannernottoexceedadischargeof3,000cfs.

8) Onatleastamonthlybasis,thesitewillbevisitedtoobserveactualconditionsandverifythat

projectisbeingoperatedwithintheparametersofthisOperatingPlan.


36/317


References

1. BarrEngineering,TolnaCouleeOutletErosion,PreparedfortheU.S.ArmyCorpsofEngineers;2001.

2. Donnelly&Blaisdell.TechnicalPaperNo.15,SeriesB.StraightDropSpillwayStillingBasin. St.

Anthony

Falls

Hydraulic

Laboratory,

University

of

Minnesota;

1954

3. HydraulicDesignCriteria623to624.1. SubcriticalOpenChannelFlowDropStructures,Hydraulic

DesignChart623CITTypeStructure;January1968

4. NRCSStreamRestorationHandbook.TechnicalSupplement14G,GradeStabilizationTechniques,NRCS.

August2007.

5. DevilsLakeFloodRiskManagementProject.DesignCriteriaandProjectConsiderationsReport,U.S.

ArmyCorpsofEngineers;21December2009

6. Baker,D.G.ClimateofMinnesota:Part14,WindClimatologyandWindPower,TechnicalBulletinADTB

1955,AgriculturalExperimentStation,UniversityofMinnesota;1983.

7. MemorandumforRecordWaveRunuponDevilsLake,U.S.ArmyCorpsofEngineers,St.PaulDistrict;

July

2006.

8. ShoreProtectionManual,WaterwaysExperimentStation,U.S.ArmyCorpsofEngineers,Coastal

EngineeringResearchCenter;1984.

9. ER111082(FR),InflowDesignFloodsForDamsandReservoirs,U.S.ArmyCorpsofEngineers,

WashingtonDC;1March1991.

10. EM111021100,CoastalEngineeringManual,U.S.ArmyCorpsofEngineers,WashingtonDC;1August

2008.

11. EM111021614,DesignofCoastalRevetments,Seawalls,andBulkheads,U.S.ArmyCorpsof

Engineers,WashingtonDC;30June1995.

12. SpiritLake(DevilsLake)NorthDakotaPhase2EvaluationofExistingRoads,U.S.ArmyCorpsof

Engineers,

2005.

13. EM111021601,EngineeringandDesignHydraulicDesignofFloodControlChannels,U.S.Army

CorpsofEngineers,WashingtonDC;30June1994.

14. EM111021602,EngineeringandDesignHydraulicDesignofReservoirOutletWorks,U.S.Army

CorpsofEngineers,WashingtonDC;15October1980

15. Rice,C.E.andKadavy,K.C.,RiprapDesignDownstreamofStraightDropSpillways,AmericanSocietyof

AgriculturalandBiologicalEngineers,JulyAugust1991.

16.MPCATechnicalCriteria,RiprapCriteriaforStabilizationPonds,MinnesotaPollutionControlAgency,

May1991

17.Donnelly&Blaisdell. SCSTechnicalPaper106. HydraulicDesignoftheBoxInletDropSpillway. Soil

ConservationService

Research,

Washington

25,

DC;

July

1951


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AccessRoadDitches InteriorFloodControlAnalysis

TheproposedTolnaCouleeaccessroadalignmentandthetwodelineatedsubwatershedsareshownin

Figure13onthefollowingpage.Thedrainageareasforthewestandeastsubbasinsweremeasured

usingtheArcMapGISprogramandweredeterminedtobe6.5and3.9acres,respectively.

AHEC

HMS

model

was

set

up

to

calculate

the

1percent

event

hydrographs

for

the

two

sub

basins.

The

modelparametersareshowninTable14. Curvenumbersweredeterminedusingavailablelanduseand

soilsmapping.SoilsinthewestsubbasinaremostlyfromHydrologicSoilGroupB,withverysmallareas

ofHSGAandC/D. TheeastsubbasinismostlyHSGB,withasmallareaofHSGAatthesouthend. The

calculatedcurvenumbersare59inthewestsubbasinand58intheeastsubbasin.

TimeofconcentrationwasdeterminedbasedonmethodspresentedinTR55(Reference18). Lagtime

wasassumedtobesixtypercentofthecalculatedtimeofconcentration. Noimperviousareawas

assumedineithersubbasin.

Table14

HECHMSModelParameters

SubArea CurveNumber TimeofConcentration(min) LagTime(min)

West 59 45 27

East 58 34 20

Theprecipitationeventusedintheanalyseswasthe100year,10daystorm. Thisisthesameevent

usedinpumpstationmodelingfortheCityofDevilsLakeEmbankmentsproject. Theaccessroadditch

subbasinsarerelativelysmallanddonothavedefineddrainagepatterns,sobaseflowwasnot

considered. TheHECHMSmodelpeakdischargesforthewestandeastsubareaswere8.3and6.5cfs,

respectively. Aculvertcrossesundertheaccessroad,carryingflowfromtheeastditchtothewest

ditch.Downstream

of

the

culvert

outlet,

the

peak

discharge

is

14.2

cfs.

This

is

slightly

less

than

the

sum

ofthepeaksforthewestandeastsubbasinsbecauseofthedifferentlagtimesbeingused.

AHECRASmodelwasdevelopedforthedrainageditchesoneithersideoftheaccessroadbasedonthe

crosssectionsincludedintheTolnaCouleeconstructionplans.Theditcheseachhaveabottomwidthof

fivefeetand3H:1Vsideslopes. Thewestditchhasanaverageslopeofapproximately4.3percent. The

eastditchhasanaverageslopeofapproximately4.6percent.Theculvertcrossingundertheaccessroad

thatcarriesflowfromtheeastditchtothewestditchwasmodeledasa55footlong,24inchdiameter

corrugatedmetalpipe(CMP)projectingfromfill(i.e.noheadwall).

Forthedesignstorm,themaximumflowvelocityintheeastditchis3.1feetpersecond(fps). The

maximumvelocityinthewestditchupstreamoftheculvertis3.4fps. Maximumvelocityinthewest

ditchdownstreamoftheculvertis3.7fps. Forslopeslessthan5%,thegeneralruleisthatthemaximumpermissiblevelocityinagrassedditchisbetween4fps(foreasilyerodedsoils)and5fps(erosion

resistantsoils). Basedonthemodelvelocities,theditchesdonotrequireriprapifgrasscanbewell

established.

Theculvert,asmodeled,isappropriatelysized. Maximumoutletvelocityforthedesignstormis4.5fps.

Gradation1riprapshouldbeplacedattheupstreamanddownstreamendsoftheculverttoprevent

erosionandscourfromoccurringduringhighflowevents.


38/317Figure 13: Tolna Coulee Access Road Drainage

Legend

East ditch drainage area

West ditch drainage area

Access Road 0 100 200 300 400 500Fee


39/317


References18.UrbanHydrologyforSmallWatersheds,U.S.DepartmentofAgriculture,SoilConservationService,

TechnicalRelease55(TR55),June1986.

19.Soil

Survey

Staff,

Natural

Resources

Conservation

Service,

United

States

Department

of

Agriculture.

WebSoilSurvey.Availableonlineathttp://websoilsurvey.nrcs.usda.gov/accessedJune30,2011.


40/317

Appendix D

Geotechnical Appendix


41/317

Design Documentation Report Tolna Coulee Advance Measures D-i

100% Final Document Geotechnical Design and Geology

Tolna Coulee Advance Measures

Nelson County, North Dakota

Appendix D

Geotechnical Design and Geology

Table of ContentsD.1 INTRODUCTION ................................................................................................ D-1D.2 REGIONAL GEOLOGY ...................................................................................... D-1

D.2.1 Physiography and Topography ........................................................................... D-1

D.2.2 General Geology ................................................................................................. D-1

D.2.3 Structure.............................................................................................................. D-2

D.2.4 Site Hydrogeology .............................................................................................. D-2

D.2.5 Seismic Risk and Earthquake History ................................................................ D-2D.3 SUBSURFACE INVESTIGATION ..................................................................... D-3

D.3.1 Site Specific Geology ......................................................................................... D-3D.3.2 Laboratory Testing ............................................................................................. D-4D.3.3 Selection of Design Parameters .......................................................................... D-4

D.4 GEOTECHNICAL DESIGN ................................................................................ D-6

D.4.1 Introduction ........................................................................................................ D-6

D.4.2 Horizontal and Vertical Datums ......................................................................... D-6

D.4.3 Design Methodology .......................................................................................... D-7

D.4.4 Cofferdam ........................................................................................................... D-7

D.4.5 Dewatering and Groundwater Control ............................................................. D-10D.4.6 Temporary Excavation Slopes .......................................................................... D-11

D.4.7 Stoplog Structure and Retaining Walls ............................................................ D-12

D.4.8 I-Wall/Embankment Composite System .......................................................... D-14D.5 PHASE I ENVIRONMENTAL SITE ASSESSMENT ...................................... D-22

D.6 SLOPE PROTECTION ...................................................................................... D-22

D.7 SOURCES OF CONSTRUCTION MATERIALS ............................................. D-23D.7.1 Impervious Fill ................................................................................................. D-23

D.7.2 Geotextile Fabric .............................................................................................. D-23

D.7.3 Stoplog Structure Subdrainage Material........................................................... D-24

D.7.4 Concrete Aggregate, Riprap, and Bedding ....................................................... D-25

D.8 INSTRUMENTATION ...................................................................................... D-25

D.8.1 Construction Monitoring .................................................................................. D-26

D.8.2 Long-Term Performance Monitoring ............................................................... D-26D.9

REVIEWS ........................................................................................................... D-27

D.9.1 District Quality Control .................................................................................... D-27

D.9.2 Agency Technical Review ................................................................................ D-27D.9.3 Independent External Peer Review ................................................................... D-27

REFERENCES ................................................................................................................... D-28


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Design Documentation Report Tolna Coulee Advance Measures D-ii

100% Final Document Geotechnical Design and Geology

Index of TablesTable D- 1: Summary of Tolna Coulee Soil Parameters ...................................................... D-5

Table D- 2: Horizontal and Vertical Datums ........................................................................ D-6Table D- 3: Cofferdam Required Factor of Safety ............................................................... D-7

Table D- 4: National Weather Service Devils Lake peak forecast levels for 2011. ............. D-8

Table D- 5: Cofferdam Seepage and Stability Results ......................................................... D-9Table D- 6: Temporary Excavation Required Factor of Safety .......................................... D-11

Table D- 7: Temporary Excavation Stability Results ......................................................... D-12

Table D- 8: Stoplog Structure Uplift/Seepage Load Cases ................................................ D-13

Table D- 9: Retaining Wall Monolith 1 Stability Analysis ................................................ D-14Table D- 10: Configuration of I-Wall//Embankment Composite System .......................... D-15

Table D- 11: Seepage Loading Conditions and Minimum Factors of Safety ..................... D-17

Table D- 12: Global Stability Loading Conditions and Minimum Factors of Safety ......... D-19Table D- 13: Factor of Safety against Piping ...................................................................... D-20

Table D- 14: Results of Global Stability Analysis.............................................................. D-21

Table D- 15: Riprap Gradation ........................................................................................... D-22

Table D- 16: Bedding Gradations ....................................................................................... D-23Table D- 17: Impervious Fill Requirements ....................................................................... D-23

Table D- 18: Geotextile Fabric Requirements .................................................................... D-24

Table D- 19: Sand Gradation Requirements ....................................................................... D-24Table D- 20: Pervious Material Gradation Requirement

Documents

Design Documentation Report