Atch 02 - FA2523-10-R-0002 Addendum 1 to Final Design Submittal 03 May 2010

US AIR FORCE SPACE COMMAND ADDENDUM #1

THULE AIR BASE, GREENLAND

PROJECT WWCX 30-0035

LANDFILL FACE STABILIZATION

ADDENDUM #1 TO FINAL SUBMITTAL

SPECIFICATIONS

May 03, 2010

ISC Rådgivende Ingeniører ISC Consulting Engineers

Øster Allé 31, DK-2100 København Ø Telephone: +45 35 27 88 00 Fax: +45 35 27 88 44 http:\\www.isc.dk E-mail: info@isc.dk

US AIR FORCE – SPACE COMMAND ADDENDUM #1

THULE AIR BASE, GREENLAND

PROJECT WWCX 30-0035

LANDFILL FACE STABILIZATION

ADDENDUM #1 TO FINAL SUBMITTAL

SPECIFICATIONS

May 03, 2010

ADDENDUM #1

2010.05.03

N/A JKI N/A LDR N/A

FINAL Submittal 2010.01.22

N/A JKI N/A UBP N/A

Draft Submittal 2009.11.27

N/A JKI N/A UBP N/A

QUALITY

CONTROL

USAF

Comments Included

Project Manager

Project Designer

Technical Reviewer

Responsible Partner

ISC Rådgivende Ingeniører ISC Consulting Engineers

WWCX 30-0035

LANDFILL FACE STABILIZATION ADD#1

SPECIFICATIONS, MAY 03, 2010 INDEX-1

ATTACHMENTS:

Attachment No.: 001. Coordinates to ground fix point no. 3490 prepared by Kort- og

Matrikelstyrelsen (National Survey and Cadastre); 2 pages.

002. Site Visit Report October 2003

003. Hydraulic Design Conditions Report, Draft Final Report

DHI Water & Environment, December 2003

END OF INDEX

ATTACHMENTS

ATTACHMENT

NO. 001

Station Nr. 3490

Bredde: 76 32 12.054231 N Længde: -68 50 25.903953 E Ell. H: 18.554 m

MSL. H: 2.73 m

Journalside: Måleår: 2002 Observator: Bo Madsen

Afmærket på foto:

Lodfoto rute billede Skråfoto rute billede

Terr. foto

Etableringsform: Signalering:

Bronzeplade [X] Varde [ ] m

Bolt [X] Pille [ ] m

Boret hul [ ] Stang [ ]

Messingbolt m. gevind [ ] Terrænsignal [ ]

Ingen [ ] Ingen [X]

Anden: Anden:

Naturligt fixpunkt:

Observationer:

Astro [ ] GPS [X] Trig [ ] Baro [ ] Grav [ ] Vandst [X] Niv [X]

Supplerende oplysninger:

REFGR punkt Thule Airbase Højdeforskel 3490 til 3357: +0.073 m (geom.niv.)

GPS navn THX4 Kortreference 76 V1

Se skitse og foto

NO. 002

H:\09152 Landfill Face Stabilization\word\a_Summary of Project Requirements, Draft 27-11-09\Final Att-005\sitevisit.doc

PROJECT WWCX 300025

Landfill Face Stabilization A-E Services

Site visit at Thule Air Base: 01 October to 08 October 2003 By Christian Riis Petersen, ISC Consulting Engineers A/S

Introduction As an element in the development of the design a site visit at Thule Air Base was made.

The weather during the visit was not ideal for outdoor activities, the Storm Season started 15. Sep-tember with frequent Weather Warnings and snowfall. The ground was frozen and partly covered with snow.

Natural & Cultural Resources Management Plan A meeting was held with Environmental Engineer Sten Rybak and Environmental Coordinator Dorte Hansgaard. Reference was made to “Thule Air Base – Natural & Cultural Resources Man-agement Plan, July 2003”, sections 7.14 Quarry and 7.15 Gravel Pits, reading:

“Blasting… of hard rock material… should be limited to the existing quarry at the hillside at North Mountain in order not disturb the existing landscape elsewhere. Environmental impact analysis, according to AFR 32-7061, Environmental Impact Analysis Process and DoD 6050.7, Environ-mental Effects Abroad of Major department of Defense Actions, must be prepared for all activities, which disturb the landscape.”

“Active gravel pits are located south of South River close to the road to D-launch. Inactive pits are scattered over large areas from det-3 to Camp Tuto and P-Mountain. Working of gravel should be limited to active pits in order not to disturb the scarce vegetation existing at the inactive pits.”

TAB 31 TAB 32 Landfill Face and Seabed Material The face of the landfills was inspected. The face appears as described in the F&R report.

The sea was not yet frozen. The beach in front of the landfills consists of stones, gravel and sand.

At TAB 32 stones (hand size) and gravel are found. At TAB 31 stones (20 – 30 mm), gravel and sand are found. The finer material is found in way of the northern part of the landfill, where also the water is more shallow. A representative sample was dug out near the waterline in way of the shoot-ing site. A sieve analysis, designated ‘seabed_1’ was made, see page 5 for grain size distribution.

Collecting sample of seabed material.

H:\09152 Landfill Face Stabilization\word\a_Summary of Project Requirements, Draft 27-11-09\Final Att-005\sitevisit.doc

Quarry at North Mountain The quarry at North Mountain was inspected.

It is estimated that the quarry can yield sufficient quantities for the project, however, more blasting will be required.

View of the quarry, looking east Broken material, scale is 2 m long From the North Mountain road

The rock is basaltic. Samples were taken to the POL-laboratory and the density was determined to be in the range 3.0 to 3.1 t/m3

Gravel pit South Mountain Large amounts of stone/gravel/sand are found at the slopes of South Mountain towards South River.

A sample was chiseled out of a frozen heap of material, and a sieve analysis, designated ‘fill_1’ was made, see page 5 for grain size distribution, the largest stones seen at the surface were excluded from the sample.

Collecting sample of gravel at Overview, gravel pit South Mountain South Mountain.

Observations at Delong pier The pier consists of a rubble mound breakwater and a quay structure of elevated barges. The top elevation of the pier is at 3.96 meter (13 ft) above HWL corresponding to 5.08 meter above Mean Sea Level.

The rubble mound breakwater faces southwest, the size of the armour stones varies very much, the max size is estimated to approx 1 –2 tonnes.

H:\09152 Landfill Face Stabilization\word\a_Summary of Project Requirements, Draft 27-11-09\Final Att-005\sitevisit.doc

View along the rubble mound Local damage

Damages are seen locally along the breakwater and at the southwestern corner of the pier head. The armour stones have slid and the core fill has been eroded. The supports of the pipeline running along the breakwater are now very close to the edge.

No signs of wave overtopping were seen.

The northwestern corner of the pier head was repaired in mid 90’, see ACG design and photo.

Northwest corner of pier head. Armour stones, W>400 kg, 2 layers, Size of stones 1 – 1.5 m Thickness 1.2 m. Design by ACG.

Ice conditions Information concerning thickness of sea ice and possible pile-up was sought. There are no re-cordings in the CE-Department. In an air-photo from the winter 2001-2002, pile-up at a distance from breakwater is seen, see page 4. This is believed to be caused by tidal variations. There was no account of the pipeline at the pier ever being damaged by ice pile-up.

H:\09152 Landfill Face Stabilization\word\a_Summary of Project Requirements, Draft 27-11-09\Final Att-005\sitevisit.doc

Photo taken Winter 2001-2002, showing ice pile-up along the pier

H:\09152 Landfill Face Stabilization\word\a_Summary of Project Requirements, Draft 27-11-09\Final Att-005\sitevisit.doc

Sieve Analysis

0,01 0,10 1,00 10,00 100,00

Grain size [mm]

P er c e n ta g e

Seabed1

Fill1

Sieve analysis, material from the beach ‘seabed_1’ and from gravel pit South Mountain‘fill_1’

NO. 003

ISC Consulting Engineers, Copenhagen

Final Report February 2004

Thule Landfill Face Stabilisation, Greenland

Hydraulic Design Conditions

Thule Landfill Face Stabilisation, Greenland

Hydraulic Design Conditions

February 2004

Agern Allé 5 DK-2970 Hørsholm, Denmark

Tel: +45 4516 9200 Fax: +45 4516 9292 e-mail: dhi@dhi.dk Web: www.dhi.dk

Client

ISC Consulting Engineers, Copenhagen

Client�s representative

Mr Uffe Burup Petersen

Project

Thule Landfill Face Stabilisation, Greenland

Project No

03-52536

Date

20 February 2004

Authors

Mogens Hebsgaard Doris Mühlestein René Zorn Approved by

Jesper Fuchs Head of Projects, POT

0 Final Report (final design submittal) RZ/DM/MHE MHE JUF 20.02.04

B Draft Report (90% design submittal) RZ/DM/MHE MHE JUF 18.12.03

A Draft Report (65% design submittal) DM/MHE MHE 06.11.03

Revision Description By Checked Approved Date

Key words

Wind, Wave and Ice Conditions Stability of Coastal Revetment Thule, Greenland

Classification

Open

Internal

Proprietary

Distribution No of copies

ISC Consulting Engineers, Copenhagen:

DHI:

Mr Uffe Burup Petersen

DM � RZ � POT � PHD

PDF

4+PDF

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe//ybr/pot/rapport - 02/04 i DHI Water & Environment

CONTENTS

1 INTRODUCTION

2 WATER LEVEL CONDITIONS

3 WIND CONDITIONS

3.1 Available Data

3.2 Wind Statistics

4 WAVE CONDITIONS

4.1 Offshore Wave Conditions

4.1.1 Available Data

4.1.2 Offshore Wave Statistics

4.2 Nearshore Wave Conditions

4.2.1 Wave Transformation Study

4.2.2 Nearshore Wave Conditions

4.2.3 Design Wave Conditions

5 ICE CONDITIONS

5.1 Sea Ice Climate

5.1.1 Weekly Sea Ice Statistic

5.1.2 Ice Thickness

5.1.3 Ice Observations and Measurements

5.1.4 Ice Thickness based on analytical and heat Flux Estimates

5.2 Ice Interaction with Structures

5.2.1 Driving Forces

5.2.2 Sheet Ice Forces

5.2.3 Remarks

6 RECOMMENDED PROFILES FOR COAST REVETMENT

6.1 Introduction

6.2 Delong Pier

6.3 Recommended Design of the Coast Protection Revetments

6.3.1 Coast Protection Profile, TAB32, Profiles P107-149

6.3.2 Coast Protection Profile, TAB31 South and TAB31 North, Profiles 212-221 and 313-329

7 REFERENCES

APPENDIX A � Set-up of Wave Model, MIKE 21 NSW

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 1 DHI Water & Environment

1 INTRODUCTION

The present report has been prepared for ISC, Consulting Engineers, Copenhagen (ISC) by DHI Water & Environment (DHI). The purpose of the study was to determine the design wave and ice conditions for a coast protection along three stretches off the coast of Thule, TAB32 and TAB31 (TAB31 North and TAB31 South), and to evaluate pro-posals for the coast protection profiles. For the site location, see Fig 1.1.

Fig 1.1 Location plan

This report contains:

• Wind and wave conditions at positions off the coast of Thule as provided from Marine Consultancy Service, the British Met Office, UK

• Wave transformation study, numerical modelling of the wave transformation from offshore to the site

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 2 DHI Water & Environment

• Evaluation of the ice conditions and design ice loads for the protection

• Desk study with evaluation of coast protection profiles with regard to design wave, water level and ice conditions

The contents of the studies are based on the proposal from DHI of 11 July 2003, revised in a letter to ISC dated 20 August 2003. In the revised proposal, the recommended flume model tests for optimisation of the profile were replaced by a desk evaluation of the coast protection. This revised proposal was accepted by ISC in a letter dated 30 September 2003.

Preliminary evaluation of the wave, water level and ice conditions was given in /1/, which also presented preliminary evaluation of the coast protection profile.

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 3 DHI Water & Environment

2 WATER LEVEL CONDITIONS

The water level at the site is mainly governed by the tide. The assessment of the water level conditions has been based on measurements carried out by �Kort & Matrikelstyrel-sen (KMS/National Survey & Cadastre, Denmark)� in the period from 4 September 2001 to 28 September 2002. The results of the measurements and the conclusions on design high water level are described in /2/.

The following water level reference conditions have been used:

Mean Sea Level: MSL = +1.37mCD according to electronic Chart, C-Map �NORTH STAR�

Chart Datum: CD = Low Water Springs according to electronic Chart, C-Map �NORTH STAR�

Design High Water Level: HWL = +1.6m MSL, HWL = +3.0mCD

According to Chart 3130 (from 2001), Chart Datum (CD) is equal to lowest astronomi-cal tide, LAT.

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 4 DHI Water & Environment

3 WIND CONDITIONS

3.1 Available Data

The basis for the assessment of the wind conditions has been wind data processed and provided by �Marine Consultancy Service, the British Met Office, UK (BMO)�. A nu-merical wave hindcast model, �the Global Wave Model�, uses the wind data to predict the wave conditions at specific positions. The wind conditions are available with a time step of six hours. The wave model has been operated since 1994. The grid was changed in May 1999, which implied that the positions of the grid points where data are available were changed at that time. The data from the two closest positions of the former and new grid were assembled for the statistical analysis. For the present analy-sis, wind data from two positions (two sets of positions) were available as follows:

Position A A1: 70.63oW; 76.25oN May 1999 to October 2003 A2: 70.43oW; 76.39oN 1994 to May 1999

Position B B1: 72.1oW; 76.9oN May 1999 to October 2003 B2: 71.9oW; 77.1oN January 1994 to May 1999

The positions are shown in Fig 3.1.

Fig 3.1 Positions A1, A2, B1 and B2

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 5 DHI Water & Environment

The data consist of monthly tables of numbers of events with wind speed in given intervals as function of wind direction.

3.2 Wind Statistics

Tables 3.1 to 3.3 summarise the wind data for positions A and B together (average of A and B). Table 3.1 shows the wind statistics for �all year�, while Tables 3.2 and 3.3 show the wind statistics for the summer months. For the assessment of the design waves, only winds occurring during the summer months were considered as the North Star Bay is covered by ice during the winter months. Two �summer periods� have been consid-ered as follows: June to October (inclusive) and May to November (inclusive). The latter, longer period gives a more conservative estimate of the resulting wave condi-tions, see Section 4.

Table 3.1 Wind occurrences (%) at positions A and B (see Fig 3.1), 1994 to 2003, all year 100% corresponds to the total number of events in the period, all directions

Wind speed

(m/s) 0 30 60 90 120 150 180 210 240 270 300 330

>0 15.5 11.7 8.5 9.0 15.7 14.5 5.1 2.1 1.7 2.0 4.3 10.1

>2 14.3 10.4 7.2 7.6 14.2 13.2 4.1 1.4 1.0 1.1 3.2 8.9

>4 10.8 6.6 3.6 4.1 10.2 9.7 2.3 0.57 0.35 0.38 1.4 6.2

>6 6.9 2.9 0.93 1.5 6.1 6.0 1.2 0.18 0.11 0.094 0.40 3.4

>8 4.0 1.0 0.13 0.51 3.5 3.1 0.48 0.068 0.034 0.019 0.10 1.8

>10 2.1 0.34 0.011 0.12 1.9 1.5 0.20 0.015 0.015 0.0038 0.011 0.74

>12 1.2 0.14 0.023 0.88 0.63 0.079 0.0075 0.0038 0.25

>14 0.54 0.038 0.0038 0.36 0.26 0.0075 0.10

>16 0.17 0.15 0.087 0.038

>18 0.064 0.038 0.042 0.0038

>20 0.0038 0.011 0.015

Wind direction (oN)

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 6 DHI Water & Environment

Table 3.2 Wind occurrences (%) at positions A and B, 1994 to 2003, June to October (inclusive) 100% corresponds to the total number of events in the period of June to October, all directions

Wind speed

(m/s) 0 30 60 90 120 150 180 210 240 270 300 330

>0 14.3 8.1 6.4 7.7 16.1 17.0 6.4 2.6 2.1 2.4 5.4 11.4

>2 12.9 6.8 5.1 6.3 14.5 15.4 5.2 1.7 1.3 1.4 4.1 10.1

>4 9.5 4.2 2.7 3.8 11.2 11.5 3.2 0.82 0.57 0.59 1.7 6.9

>6 6.2 1.8 0.64 1.8 7.4 7.3 1.8 0.27 0.19 0.19 0.47 3.8

>8 3.7 0.63 0.076 0.68 4.6 3.9 0.78 0.12 0.051 0.042 0.16 1.9

>10 1.8 0.29 0.18 2.6 1.7 0.39 0.017 0.017 0.0085 0.017 0.69

>12 1.0 0.14 0.042 1.28 0.67 0.16 0.0085 0.21

>14 0.41 0.025 0.0085 0.60 0.31 0.0085 0.059

>16 0.10 0.22 0.135 0.0085

>18 0.017 0.059 0.085

>20 0.0085 0.034

Wind direction (oN)

Table 3.3 Wind occurrences (%) at positions A and B, 1994 to 2003, May to November (inclusive) 100% corresponds to the total number of events in the period of May to November, all directions

Wind speed

(m/s) 0 30 60 90 120 150 180 210 240 270 300 330

>0 15.0 9.0 6.8 8.0 16.3 16.2 6.2 2.5 2.0 2.2 4.9 10.9

>2 13.7 7.7 5.6 6.7 14.7 14.6 5.1 1.7 1.2 1.3 3.7 9.7

>4 10.2 4.9 3.0 4.0 11.1 10.9 3.1 0.77 0.49 0.49 1.5 6.6

>6 6.9 2.1 0.70 1.7 7.2 6.7 1.7 0.27 0.17 0.14 0.43 3.7

>8 4.1 0.69 0.075 0.65 4.3 3.4 0.72 0.11 0.057 0.031 0.12 1.7

>10 2.0 0.30 0.17 2.4 1.6 0.31 0.025 0.025 0.0063 0.013 0.67

>12 1.1 0.13 0.038 1.2 0.64 0.12 0.013 0.0063 0.19

>14 0.54 0.031 0.0063 0.52 0.28 0.0063 0.044

>16 0.18 0.21 0.11 0.0063

>18 0.075 0.057 0.063

>20 0.0063 0.013 0.025

Wind direction (oN)

It is seen that the strongest winds occur from south-easterly and northerly directions.

However, only winds from directions SSW to NNW contribute to the design wave con-ditions at Thule. Figures 3.2 and 3.3 show graphs of exceedance frequencies of wind speeds for these directions. The markers represent the data shown in Tables 3.2 and 3.3.

The lines correspond to the best Weibull fit.

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 7 DHI Water & Environment

June to October

0.00001

0.0001

0.001

0.01

0.1

0 5 10 15 20 25

Wind Speed (m/s)

Ex ce ed an ce P ro ba bi lit y

180degN 210degN 240degN 270degN 300degN 330degN 180degN 210degN 240degN 270degN 300degN 330degN

6h/100seasons (Jun-Oct)

Fig 3.2 Exceedance probabilities (-) for wind speeds at positions A and B, June to October (inclusive), wind directions 180oN to 330oN

May to November

0.00001

0.0001

0.001

0.01

0.1

0 5 10 15 20 25

Wind Speed (m/s)

Ex ce ed an ce P ro ba bi lit y

180degN 210degN 240degN 270degN 300degN 330degN 180degN 210degN 240degN 270degN 300degN 330degN

6h/100seasons (May-Nov)

Fig 3.3 Exceedance probabilities (-) for wind speeds at positions A and B, May to November (inclusive), wind directions 180oN to 330oN

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 8 DHI Water & Environment

Table 3.4 shows the wind speed corresponding to the exceedance probability of 6h/100years found by extrapolation with the best Weibull fit.

Table 3.4 Estimate of wind speeds (m/s) with exceedance probability 6h/100years.

Wind directions 180oN to 330oN

Wind direction Wind speed (m/s) (oN) June to October (inclusive) May to November (inclusive) 180 16.8 16.6 210 13.0 14.2 240 13.1 16.1 270 11.9 11.9 300 13.2 13.1 330 18.1 18.0

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4 WAVE CONDITIONS

4.1 Offshore Wave Conditions

4.1.1 Available Data

The basis for the assessment of the offshore wave conditions is the wave data calculated by the numerical wave hindcast model �the Global Wave Model�. The model calculates the wave conditions based on the variation of the wind fields and air pressure and the fetches. The wave conditions are available with a time step of six hours. The calcula-tions were made by �Marine Consultancy Service, the British Met Office, UK (BMO)�.

The model has been operated since 1994.

For the present analysis, data from position A were used:

Position A A1: 70.63oW; 76.25oN May 1999 to October 2003 A2: 70.43oW; 76.39oN 1994 to May 1999

The positions are shown in Section 3, Fig 3.1.

4.1.2 Offshore Wave Statistics

Offshore waves from the directional interval from SSW through W to NNW reach the coast at Thule. The coast in the North Star Bay will only be exposed to wave action during the summer months, due to ice coverage during winter. Ice observations indicate that ice covers the coastal waters from November to May (inclusive). The offshore wave data have therefore been analysed for the period from June to October (inclusive).

However, the period including also May and November has also been considered in order to evaluate the influence on the wave statistics. Climatic changes, such as green-house effect and global warming, may make it advisable to consider the longer summer period, ranging from May to November (inclusive).

Tables 4.1 and 4.2 show the offshore wave occurrences for the two summer periods.

Waves from directions 180oN (=S) to 330oN ( ≅ NNW) are shown.

Figures 4.1 and 4.2 show graphs of exceedance frequencies of offshore wave heights from these directions for the two periods. The markers represent the data shown in Tables 4.1 and 4.2. The lines correspond to the best Weibull fit.

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 10 DHI Water & Environment

Table 4.1 Offshore Wave occurrences (%) at position A, 1994 to 2003, June to October (inclusive) 100% corresponds to the total number of events in the period of June to October, all directions

Sign. Wave height

Hm0 (m) 180 210 240 270 300 330

>0 4.4 2.0 1.9 2.7 9.5 10.6

>0.6 2.6 1.3 1.1 1.6 7.0 7.3

>1.1 1.6 0.66 0.39 0.63 4.2 3.9

>1.6 0.81 0.37 0.17 0.22 2.2 1.7

>2.1 0.47 0.14 0.034 0.051 0.73 0.78

>2.6 0.19 0.034 0.017 0.12 0.20

>3.1 0.068 0.017 0.051

>3.6 0.017 0.017 0.034

>4.1 0.017

Wave direction (oN)

Table 4.2 Offshore Wave occurrences (%) at position A, 1994 to 2003, May to November (inclusive) 100% corresponds to the total number of events in the period of May to November, all directions

Sign. Wave height

Hm0 (m) 180 210 240 270 300 330

>0 4.0 1.9 1.6 2.2 7.9 9.6

>0.6 2.1 1.1 0.8 1.2 5.6 5.8

>1.1 1.3 0.54 0.31 0.47 3.4 3.2

>1.6 0.62 0.29 0.13 0.16 1.8 1.5

>2.1 0.35 0.10 0.025 0.038 0.67 0.75

>2.6 0.14 0.025 0.013 0.19 0.24

>3.1 0.050 0.013 0.063

>3.6 0.013 0.013 0.025

>4.1 0.013

Wave direction (oN)

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 11 DHI Water & Environment

June to October

0.00001

0.0001

0.001

0.01

0.1

0 1 2 3 4 5 6 7

Significant Wave Height (m)

Ex ce ed an ce P ro ba bi lit y

180degN 210degN 240degN 270degN 300degN 330degN 180degN 210degN 240degN 270degN 300degN 330degN

6h/100seasons (Jun-Oct)

Fig 4.1 Exceedance probabilities (-) for wave heights at position A, June to October (inclusive), directions 180oN to 330oN

Fig 4.2 Exceedance probabilities (-) for wave heights at position A, May to November (inclusive), directions 180oN to 330oN

Table 4.3 shows the significant wave height corresponding to the exceedance probabil-ity of 6h/100years found by extrapolation with the best Weibull fit.

May to November

0.00001

0.0001

0.001

0.01

0.1

0 1 2 3 4 5 6 7

Significant Wave Height (m)

Ex ce ed an ce P ro ba bi lit y

180degN 210degN 240degN 270degN 300degN 330degN 180degN 210degN 240degN 270degN 300degN 330degN

6h/100seasons (May-Nov)

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 12 DHI Water & Environment

Table 4.3 Estimate of offshore wave height, Hm0,i (m), with exceedance probability 6h/100years

Wind direction Wave height, Hm0,i (m) (oN) June to October (inclusive) May to November (inclusive) 180 5.0 5.3 210 4.5 4.5 240 3.0 3.1 270 3.3 3.3 300 3.8 3.9 330 4.5 4.8

4.2 Nearshore Wave Conditions

4.2.1 Wave Transformation Study

When the waves approach the coast, they undergo a transformation due to shoaling, refraction, bottom friction, wave breaking, wind forcing and diffraction.

The transformation of the offshore waves to the coast at the Thule Air Base landfill areas has been assessed using DHI�s numerical nearshore spectral wind-wave model, MIKE 21 NSW. This model is a directional steady-state wave model capable of taking into account the effects of shoaling, refraction, bottom friction, wave breaking and wind forcing. Diffraction effects are not included.

The model output gives the integrated wave parameters such as the significant wave height, the mean wave period and the mean wave direction.

The main input to the model consists in the following parameters:

• bathymetry conditions

• offshore wave conditions at the model boundary (significant wave height, mean wave period and wave direction)

• wind conditions in the model area

The model set-up is described in Appendix A. This appendix shows also the applied model parameters.

Simulation Programme Wave transformation simulations have been carried out for the six mean wave directions 180oN, 210oN, 240oN, 270oN, 300oN and 330oN. For each of these directions, the events corresponding to exceedance frequencies 6h/year, 6h/10years and 6h/100years have been simulated. The corresponding input parameters for offshore wind and wave conditions are shown in Appendix A. All wave simulations were carried out with design high water level (+1.6m MSL = +3.0mCD).

4.2.2 Nearshore Wave Conditions

Figures 4.3 to 4.4 show simulated wave fields in the North Star Bay. The 6h/100years events for all six directions are shown.

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Fig 4.3 Extract of simulated wave fields, offshore wave directions 180oN, 210oN and 240oN. The colours indicate the significant wave height, the arrows indicate the mean wave direction

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 14 DHI Water & Environment

Fig 4.4 Extract of simulated wave fields, offshore wave directions 270oN, 300oN and 330oN. The colours indicate the significant wave height, the arrows indicate the mean wave direction

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The calculated wave conditions have been extracted at eight positions in front of the Thule Air Base landfill areas TAB32 and TAB31 South as follows:

• Positions A to E at water depths �10mCD

• Positions G to I at water depths �5mCD

The positions are shown in Fig 4.5.

Fig 4.5 Local bathymetry and Positions A � I, depths relative to CD (CD = ~LAT)

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Figures 4.6 and 4.7 show the calculated significant wave heights as function of the estimated exceedance frequency.

A

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m

0 ( m

B

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m

0 ( m

C

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m

0 ( m

D

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m

0 ( m

E

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m

0 ( m

Figure 4.6 Calculated significant wave heights in front of the Thule Air Base landfill areas TAB32 and TAB31, at �10mCD in positions A-E. The positions are shown on Fig 4.4.

The three exceedance probabilities correspond to 6h/year, 6h/10years and 6h/100years respectively.

The statistics are based on the summer period covering June to October (inclusive).

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G

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m 0 ( m

H

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100

Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m 0 ( m

I

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0001 0.001 0.01 0.1 1 10 100 Exceedance probability (%)

Si gn ifi ca nt W av e

H ei gh t, H m 0 ( m

Fig 4.7 Calculated significant wave heights in front of the Thule Air Base landfill areas TAB32 and TAB31, at �5mCD. The positions are shown on Fig 4.4.

The three exceedance probabilities correspond to 6h/year, 6h/10years and 6h/100years respectively.

The statistics are based on the summer period covering June to October (inclusive).

The results show that:

• waves from 300oN govern the design wave conditions at the landfill areas TAB32 and TAB31

• no clear pattern is seen for wave climate changes from the northern part to the southern part of the coastline at TAB32 and TAB31

• wave heights are not reduced from �10mCD to �5mCD

The above results lead to a wave height in front of the revetment of Hm0 = ~2.5m for an exceedance probability of 6h/100years (= 3h/50years).

If the offshore wave statistics including May and November are used, this wave height would be increased to Hm0 = 2.6-2.7m.

4.2.3 Design Wave Conditions

Based on the offshore wave statistics and the results of the wave transformation study, it is recommended to use a design wave height of

Hm0 = 2.7m with Tp = 9-10s.

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5 ICE CONDITIONS

5.1 Sea Ice Climate

First-year ice is the predominant ice type at Thule with a small percentage of multi-year ice occurring, originating mainly from Smith Sound. The harbour is frozen from the end of October to the beginning of July. During calm weather conditions, the ice can occur from the middle of September. In the beginning of November, there is normally a belt of first-year ice along the coastline, which reaches its maximum thickness of about 1.8m in the month of April, and in the beginning of May the first-year ice breaks.

5.1.1 Weekly Sea Ice Statistic

The Canadian Ice Service (CIS) has produced weekly digitised �Composite Ice Charts� including the area just South of Thule (Baffin Bay) from end of May until end of November for the period 1959�1980. Knowing the Canadian sea ice grid definition, Danish Meteorological Institute (DMI) has digitised Ice Charts for the period 1981� 1995.

For a number of individual grid points, a number of physical parameters were analysed statistically for the 37-year period, /3/. The results are given in Table 5.1 for a grid point South of Thule (Lat 75.8, Long 65), the �mean ice concentration� in tenths and �ice free� in percent of time.

Table 5.1 Weekly �Mean Ice Concentration� and �Ice Free�, /3/

Month and date Mean [1/10] Ice Free [%] Month and date Mean [1/10] Ice Free [%] May 21 10 0 September 3 0.7 86 June 4 8.2 11 September 10 0.8 86

June 11 7.9 10 September 17 1.2 81 June 18 8.7 3 September 24 1 86 June 25 8.1 9 October 1 1.7 76 July 2 7.1 16 October 8 2.6 62 July 9 6.2 11 October 15 4.4 47

July 16 6 17 October 22 5.8 32 July 23 4.9 29 October 29 7.8 15 July 30 4 35 November 5 9.3 0

August 6 4.1 43 November 12 9.3 0 August 13 3.4 50 November 19 9.6 0 August 20 2.7 53 November 26 9.6 0 August 27 1.1 75

Table 5.1 shows that �ice free� periods only occur in the months from June to October.

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5.1.2 Ice Thickness

General The growth of sea ice in Baffin Bay is repeatedly interrupted in its initial stages due to weather and wave activity. However, from early winter the thickness of the sea ice will increase and continue to increase throughout the winter and early spring until it reaches its maximum in April. The average annual maximum appears from Fig 5.1, based on many years of reconnaissance and computations, but very few measurements. It ranges from about 0.75m off the West Coast of Greenland at 70°N (off Disko) to about 1.5m in the northern part of Baffin Bay and 1.75m just North of Thule.

Fig 5.1 Average annual maximum of ice thickness (cm), 1953-78, /4/

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5.1.3 Ice Observations and Measurements

Very few observations of ice thickness from the area around Thule Harbour (Pituffik) are available. The results are listed in Table 5.2, /5/ and /6/.

Table 5.2 Thickness [m] of fast ice observed and measured, /5/ and /6/

Wolstenholme Fjord

End of Jan Feb Mar Apr May Oct Nov Dec

1916/17 max. about 1.5

Thule / Dundas

1957 1.30 "good" 1952 1.35 1.49 1.79 1.78 1.10 1951 1.06 1.35 1950 "new ice" "fast ice" "good ice" 1949 1.19 1.47 1.72 1.79 1.83 "young ice" "fine ice" 1948 "thick" "good" "good" "good" "good" "good"

New Thule / Qaanaaq

1968 0.8-1.2 1963 0.93 1.06 1.14 1.26 1.24 1961 0.59 0.38 0.59 1.02

5.1.4 Ice Thickness based on analytical and heat Flux Estimates Obviously, there is a strong relation between the cumulated number of freezing degree-days and the thickness of the ice, and various researchers have attempted to formulate the relations and some of these are described below.

Sea ice in the eastern Baffin Bay appears in two �forms� � as moving drift ice and sta-tionary land fast ice, called fast ice. In the winter months, fast ice forms near the coast.

Outside this fast ice zone, fast ice can be formed from consolidated drift ice. Thickness of drift ice and fast ice can be estimated from empirical relations, analytical relations and numerical models.

Field studies have shown that the thickness, h, of young ice and thin first-year ice is closely related to the cumulative number of freezing degree-days, θ:

( ) dtTT as∫ −=θ here, Ts is the freezing point of water and Ta is the air temperature at height 2m.

Anderson�s formula is valid for ice thickness less than 80cm and no snow cover:

θ=+ 7.61.52 AA hh with the physical solution

[ ]cmhA 2

8.26261.5 θ++−

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Zubov�s formula θ=+ 8502 zz hh with the physical solution

[ ]cmhz 2 32250050 θ++− and Lebedev�s formula

58.033.1 θ=Lh [cm] are valid under �average� snow conditions. The behaviour of these expressions as func-tion of the cumulative number of freezing degree-days is shown in Tables 5.3 and 5.4 below.

Estimates of Ice Thickness at End of Freeze-up Season, 1981-86 The ice thickness formulas (including the thermodynamic model) were tested on data from the synoptic weather station, Upernavik, from the period 1981 to 1986. Unfortu-nately, some data are missing for periods of 1-3 days, and data do not cover night-time observations. Anyway, the calculations below are expected to be valid because only small differences between day and night are expected for the winter period.

Table 5.3 Estimates of freezing degree-days of each month and the total number of freezing degree-days for the winter, /3/

Winter Oct Nov Dec Jan Feb Mar Apr Total, Winter

1981-82 32 146 200 337 600 515 305 2165 1982-83 70 220 433 873 670 750 400 3396 1983-84 125 250 426 705 844 620 465 3435 1984-85 60 222 392 364 533 527 255 2333 1985-86 64 140 168 308 188 610 328 1808

Table 5.4 Calculated ice thickness (h [cm]) from the total number of freezing degree-days for the winter (total from Table 5.3) by the empirical formulas developed by Anderson, Zubov and Lebedev, /3/

Winter hA hz hL

1981-82 118 109 114 1982-83 146 142 148 1983-84 147 143 150 1984-85 123 114 119 1985-86 108 98 103

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The maximum ice thickness is thus expected to be:

mild winter: 1.0-1.2m normal winter: 1.1-1.4m severe winter: 1.2-1.5m

The thickness does not include rafting, hummocks and ridges. The thickness of fast ice at the end of the freeze-up season close to the coast in Melville Bay is expected to be:

1.3-1.8m

Ice Growth during Freeze-up Season Reference /4/ describes the average ice growth at two stations during the freeze-up season.

Table 5.5 Average thickness (cm) of sea ice according to /4/

Station Late Nov Late Dec Late Jan Late Feb Late Mar Late Apr Upernavik 38 63 89 112 130 145 Kap York 63 91 120 140 155 170

Utilising the information given in Table 5.3, the ice thickness growth during the freeze-up season can be estimated. By means of the empirical formulas developed by Ander-son, Zubov and Lebedev, and from the accumulated number of freezing degree-days month by month (Table 5.3), the growth of ice thickness throughout the winter period can be estimated. The results are given in Tables 5.6 through 5.8 and Figs 5.2 through

5.4 below.

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Table 5.6 Accumulated ice thickness (Anderson)

Year/Month Oct Nov Dec Jan Feb Mar Apr 1981/82 12.3 32.1 47.8 66.7 91.3 108.2 117.1 1982/83 19.3 41.6 67.1 100.9 120.7 139.6 148.8 1983/84 26.5 47.6 70.8 97.9 123.0 138.5 149.2 1984/85 17.7 41.0 64.7 84.8 103.3 118.8 125.7 1985/86 18.3 34.5 47.4 65.0 73.8 97.0 107.5

Month

Ic e

Th ic kn es s (c m

1981/82 1982/83 1983/84 1984/85 1985/86

Oct Nov Dec Jan Feb Mar Apr May

Fig 5.2 Accumulated ice thickness (Anderson)

Table 5.7 Accumulated ice thickness (Zubov)

Year/Month Oct Nov Dec Jan Feb Mar Apr 1981/82 4.7 20.3 35.4 54.7 80.6 98.6 108.1 1982/83 9.4 29.3 55.1 90.7 111.9 132.3 142.2 1983/84 15.3 35.2 58.9 87.6 114.4 131.2 142.6 1984/85 8.2 28.7 52.6 73.6 93.3 109.9 117.3 1985/86 8.7 22.5 35.0 52.9 62.0 86.6 97.8

Month

Ic e

Th ic kn es s (c m

1981/82 1982/83 1983/84 1984/85 1985/86

Oct Nov Dec Jan Feb Mar Apr May

Fig 5.3 Accumulated ice thickness (Zubov)

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Table 5.8 Accumulated ice thickness (Lebedev)

Year/Month Oct Nov Dec Jan Feb Mar Apr 1981/82 9.9 26.9 41.6 60.2 85.7 103.8 113.5 1982/83 15.6 35.6 60.6 95.9 117.5 138.7 149.0 1983/84 21.9 41.4 64.3 92.7 120.0 137.4 149.5 1984/85 14.3 35.1 58.1 78.8 98.4 115.4 123.0 1985/86 14.8 29.1 41.2 58.4 67.3 91.7 103.0

Month

Ic e

Th ic kn es s (c m

1981/82 1982/83 1983/84 1984/85 1985/86

Oct Nov Dec Jan Feb Mar Apr May

Fig 5.4 Accumulated ice thickness (Lebedev)

In the tables and figures above, it can be seen that the sea ice increases from about 0.2m in October to about 1.5m in April.

5.2 Ice Interaction with Structures

5.2.1 Driving Forces

As an ice-sheet approaches a sloping structure, the ice begins to crush at first contact at the interface. As the driving forces increase, the ice continues to crush and the magni-tude of the applied forces increases. The interaction force, acting normal to the face of the sloping structure, has a vertical and a horizontal component; the vertical component produces bending in the ice-sheet. The ice will fail in bending when the vertical com-ponent increases to a certain level. After the local failure of an ice-sheet, the small pieces of ice are pushed by the approaching ice-sheet and begin to ride up the face of the structure. This causes a larger interaction force to be generated, since additional force is required to push the broken pieces of ice up the structure.

In addition to the predominant mode of bending failure, it is also necessary to consider the additional freeze forces that may arise if an ice-sheet has developed a bond with the structure during period of no-ice movement.

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The horizontal driving force on the floe can be calculated as, /7/:

F = Fwind + Fwater

Fwind = 0.003 ρa V2 Aair

Fwater = 0.005 ρw u2 Awater

Assuming:

Aair = top surface area of ice floe = 10,000m x 1m Awater = bottom surface area of ice floe = 5,000m x 1m V = wind speed (10m above the floe) = 20m/s u = current speed (1m below the floe) = 0.5m/s ρa & ρw = density of air and water = 1.3 x 10-3t/m3 & 1.03t/m3

The horizontal forces reach the magnitude at 20.7kN/m. This is regarded as a conser-vative value, as a wind speed of 20m/s, a current speed of 0.5m/s and directions towards the shore will occur with very low frequencies.

5.2.2 Sheet Ice Forces

At the instant of first contact with ice, the interaction forces (using a two-dimensional (2D) analysis model) for ice interaction with sloping structure, /8/, the interaction forces are as follows:

H = N sinα + µN cosα and

V = N cosα - µN sinα or

H = VC

where:

C = (sinα + µcosα)/( cosα - µsinα) α is the angle of the slope = 26.6° µ is the friction coefficient, values of 0.1 and 0.2 have been used in the evaluation

H and V are the horizontal and vertical components of the normal force N, see Fig 5.5.

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Fig 5.5 Interaction between ice and a sloping structure, /9/

When the moment capacity of the ice-sheet is related to the corresponding vertical force required to initiate the failure, the horizontal force per unit width of structure is given by:

H/D = 0.68 σf (ρw g h5/E)0.25 C where:

D = width of structure σf = bending strength of ice = 700kN/m2 ρw g = weight density of water h = ice thickness E = elastic modulus of ice = 107kN/m2

This gives the theoretical horizontal force, which is necessary to mobilise at the instance of the first failure of the ice. This force is shown relative to the ice thickness in Fig 5.6.

0.0 0.5 1.0 1.5 2.0

Ice Thickness (h) m

H or iz on ta l f or ce p er u ni t ( H

/D ) k

N /m µ = 0.1 µ = 0.2

Fig 5.6 Ice thickness (h) vs horizontal force per unit (H/D) required for failure

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Once the ice has failed, the broken pieces start to ride up the face of the structure, and an additional force is experienced by the structure.

The corresponding total horizontal force per unit width experienced by the structure is:

H/D = C1σf (ρw g h5/E)0.25 + z h ρi g C2 where:

C1 = 0.68 C C2 = C (sinα + µcosα) + ( sinα + µcosα) / tan α z is the maximum ride-up height ρi g is the weight density of ice

The theoretical ride-up value, z, for a given ice thickness has been calculated and is shown in Fig 5.7.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0.0 0.5 1.0 1.5 2.0

Ice Thickness (h) m

Ri de

-u p

(z ) m µ = 0.1 µ = 0.2

Fig 5.7 Ice thickness (h) vs ride-up level (z)

5.2.3 Remarks

Figure 5.6 shows that the generated horizontal force can provoke failure of ice up to about 1.5m thick, but Fig 5.7 shows that no ride-up for this ice thickness will occur.

Ride-up up to 2m can occur with an ice thickness of 0.5m and ride-up to 4m can occur with an ice thickness of 0.3m. This ice thickness only occurs in the months of October and November.

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The history shows that apparently no damage due to ice ride-up has taken place to the installations on the Delong Pier, and only small ridges have been observed along the coast, see Fig 5.8.

Fig 5.8 Small ridges along the coast and pier (Photo: Jack Stephens)

The ice ride-up conditions evaluated in this report are regarded conservative. This, together with the fact that no damage to the pier installations (Delong Pier) has been observed, makes that it is not expected that major damage will take place to the armour layer due to ice ride-up and ice piling-up. It is instead recommended especially to con-centrate on the design of the slope between the beach and the toe.

At the toe of the structure, some damage can be expected due to ice pressure. The grounded ice will tend to flatten the slope by displacing some of the upper stones in the toe protection. From this point of view, it would be preferable to trench the entire toe protection into the seabed. However, such a structure would be rather expensive to con-struct, and instead it is proposed to construct the profile with a relatively wide toe pro-tection, which may allow some relocations of stones without endangering the overall stability of the structure. The filter layer, however, is recommended trenched, espe-cially for the shallow water sections.

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6 RECOMMENDED PROFILES FOR COAST REVETMENT

6.1 Introduction

The recommended revetment profiles have been developed based on the wave and ice conditions established in the present study. Furthermore, the present conditions of the Delong Pier have been included in the considerations.

6.2 Delong Pier

According to drawings received from ISC, the armour layer of the Delong Pier was con-structed using rocks with a minimum weight of 400kg sloping 1:1.25. From photos taken in October 2003, it is seen that the armour layer has suffered serious damage at certain locations. The upper part of the armour layer in the profile has been totally damaged at three locations, and the armour layer rock is mixed with the filter layer.

Scour is observed around and under some of the foundation elements for the pipes at the crest causing a potential risk of undermining the foundations.

The width of the crown is reduced a couple of meters at one location (estimated from the photos). The overtopping is deemed to be limited, as no damage seems to have occurred to the pipes.

It is estimated that the damage to the armour layer has been caused by wave action and not by ice ride-up. Assuming that the armour layer is consisting of 0.4�0.8t basalt stones (W50≅0.6t) with density of 3.0t/m3, it is found that the design wave conditions would be Hm0=1.2�1.9m depending on the applied stability coefficient (KD=1-4). The lower value corresponds to initiation of damage, while the upper value corresponds to some damage to the structure (5 to 10 percent). Assuming that the structure has been constructed according to the specifications, and assuming a mean weight of 0.6t for the stones, it is concluded that the breakwater has been exposed to wave heights in the upper end of the mentioned interval or even higher. It is thus concluded that the design wave height for the breakwater should be larger than 1.9m, which is in good agreement with the findings of the present study.

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6.3 Recommended Design of the Coast Protection Revetments

An evaluation of recommended revetment profiles has been performed for coast protec-tion sections at TAB32 and TAB31 (South and North).

6.3.1 Coast Protection Profile, TAB32, Profiles P107-149

The seabed at TAB32 is assumed to be sloping 1:10.

Main Armour Layer The recommendation for the profiles for the coast protection has been based on the following design parameters:

− Wave height, Hm0=2.7m (see Section 4) − High water level =+1.6m MSL − Rock material for the armour layer, basalt with a density of 3.0t/m3

− Slope of armour layer 1:2

The necessary rock sizes for the armour layer are determined by means of Hudson�s stability formula:

ρ ρ⋅ ρ⋅= w s D sm aK

HW

where

W = mean rock weight (t) Hm0 = significant wave height (m) ρs = density of rock material (t/m3), a value of 3.0t/m3 has been used ρw = density of water (t/m3), a value of 1.03t/m3 has been used KD = dimensionless stability factor a = slope of the armour layer = 2

KD is the stability factor, which for breaking waves should not exceed a value of 1.5-2.

This leads to a mean rock size in the armour layer of W≅2.1-2.7t. A rock gradation of 1.7-3.4t (W50=2.4t) is accordingly proposed. This corresponds to typical rock dimen-sions of 0.9-1.1m.

The top level of the armour stones is recommended to correspond to 2.5m (≅design wave height) above the design high water level, or minimum +4.1m MSL.

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Filter Thompson and Shuttler�s filter criteria state:

d15,a/d85,f ≤ 4 d50,a/d50,f ≤ 7 d15,a/d15,f ≤ 7 d15,f > 0.15m d50,f > 0.20m d85,f > 0.30m

It is proposed to use a gradation of 5-250kg (W50 ≅ 25-50kg) as filter layer under the armour layer. It is proposed to use this gradation (possibly 1-250kg) also as core mate-rial. Using this gradation, which includes rather small stones, some loss of material through the armour layer has to be expected, though.

Toe of Structure The toe of the structure should be designed in a way giving a safe and stable basis for the primary armour. Generally, it will not be possible to avoid a certain scouring and damage at the toe of the structure. This means that the amount of rock in the toe should be sufficient to allow for a certain damage to or relocation of the toe material. As this damage will be initiated/concentrated at the edge of the structure, it is important that the dimensions of this toe structure are so large that a certain damage can be accepted here, but without reaching and endangering the base of the primary armour on the slope.

Two different layouts of the toe protection were considered initially as follows:

Layout 1 This layout is proposed with the toe protection placed directly on the existing seabed.

The toe protection is proposed consisting of a 4m wide berm of armour stones placed on a 1m thick layer of filter stones. Under the filter layer, a suitable geotextile should be placed.

Layout 2 This layout is proposed with the toe protection trenched into the seabed. The toe pro-tection is proposed consisting of a berm of 0.8-1.5t stones placed on a 1m thick layer of filter stones. Under the filter layer, a suitable geotextile should be placed.

The toe parts of the two layouts are shown in Fig 6.1.

Layout 2 is preferred from a hydraulic point of view. The toe will be better protected against wave forces and ice forces. It is expected that the relocation of rock in the berm will be much less for Layout 2 than for Layout 1. However, the excavation work will be comprehensive in Layout 2, and therefore a combination of Layouts 1 and 2 is sug-gested. For the deepest located profiles, ie with a water depth of 3m or more relative to MSL at the toe, Layout 1 is recommended with the lower main armour berm at level +1.0m. For water depths at the toe between 2m and 3m, it is recommended to use the

52536 Thule Landfill Face Stabilisation-Final/dm/rz/mhe/ybr/pot/rapport - 02/04 32 DHI Water & Environment same profile, ie a lower berm level at +1.0m. This will imply that the filter layer will be trenched partly or fully into the seabed. The stretch with water depths less than 2m is relatively short and may be constructed with the same profile. Alternatively, the profile should be constructed following the seabed, with trenching of the toe only. As the seabed slope varies, it is generally recommended to construct the profiles horizontally at level +1.0m. This is recommended in order that the structure appears uniformly along the coastline.

Fig 6.1 Sketch of toe parts for the two layouts (upper: Layout 1, lower: Layout 2)

Upper Part of Structure The upper part of the structure (about +4.1m MSL) can be constructed using smaller stones. It is recommended to apply a stone size of W50≅600kg. A rock gradation of 0.25-1.7t is recommended.

The recommended layout alternatives are enclosed as sketched in Fig 6.2. The layout is shown for three different water levels at the toe of the structure. The slope of the upper part of the structure is in the figures shown to be 1:2, however, it will be possible to construct this part with a steeper slope. A steepness of up to 1:1.5 may be applied.

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Fig 6.2 Sketch of layout recommendations for coast profiles Upper: water depth at toe larger than 3m MSL Middle: water depth at toe between 2 and 3m MSL Lower: water depth at toe less than 2m MSL

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