EMERGENCY ENGINEERING ASSISTANCE

EMERGENCY ENGINEERING ASSISTANCE POST-HURRICANE MATTHEW RAPID ON-SITE ASSESSMENT RIVIERE GRISE WATER DIVERSION STRUCTURE DUMAY, HAITI FINAL REPORT

December 6, 2016

DISCLAIMER

This publication was produced for review by the United States Agency for International Development. It was prepared by PEREZ, APC.

TO-16-00028 / 04-14-1002-01a Final Assessment Report Page i

EMERGENCY ENGINEERING ASSISTANCE POST-HURRICANE MATTHEW RAPID ON-SITE ASSESSMENT RIVIERE GRISE WATER DIVERSION STRUCTURE DUMAY, HAITI FINAL REPORT

This report was prepared for the United States Agency for International Development, Contract No. AID-OAA-I-15-00051 / AID-OAA-TO-16-00028 / 04-14-1002-01a

Contact Information

Joseph M. Crowley, Project Manager

Perez, A Professional Corporation

317 Burgundy Street, Suite No. 11

New Orleans, LA 70112

The author’s views expressed in this publication do not necessarily reflect the views of the United States Agency for International Development or the United States Government.

TO-16-00028 / 04-14-1002-01a Final Assessment Report Page 1

TABLE OF CONTENTS

1.0 Background ............................................................................................................................................................ 1

2.0 Objective ................................................................................................................................................................ 1

3.0 Introduction .......................................................................................................................................................... 1

4.0 Desk Review ......................................................................................................................................................... 2

5.0 ON-SITE EVALUATION ................................................................................................................................... 6

6.0 FINDINGS ............................................................................................................................................................. 7

6.1 Barrage: .............................................................................................................................................................. 8

6.2 Spurs ................................................................................................................................................................... 9

6.3 Gabion Walls .................................................................................................................................................... 9

6.4 Gate Works ...................................................................................................................................................... 9

6.5 Canal ................................................................................................................................................................. 10

6.6 Mining ............................................................................................................................................................... 10

7.0 Recommendations: ............................................................................................................................................ 11

8.0 List of Documents Provided and Reviewed ................................................................................................ 12

9.0 Additional References ....................................................................................................................................... 16

Annex A – Design Drawings

Annex B – Photographs


1.0 BACKGROUND

The Feed the Future Haiti Chanjé Lavi Plantè (Project) is a USAID-funded project that is implemented over a three year period by Chemonics International in collaboration with CH2MHILL, SSG Advisors and WOCCU. The project is building on results achieved through Feed-the-Future West/ WINNER to sustainably transform the agriculture sector; increase agricultural incomes; and contribute to improve the nutritional status of 60,000 beneficiary households in the Cul-de-Sac and Matheux corridors, as well as in mango production areas.

Access to reliable irrigation water, good seeds and modern techniques are the main bottlenecks to increased agricultural productivity and expanding production. The issue of irrigation water must be addressed in priority, especially in the current context of climatic changes and rampant drought in the country.

A CH2MHill team who led the design of the diversion structure, supervised the construction, and has overseen ongoing maintenance will also be conducting their own assessment of the damages to the structure and recommendations for possible repair.

Following continuous rain associated with from Hurricane Matthew on October 3rd and 4th 2016 and the current rainy season, the Riviere Grise barrage, which was constructed under the Feed-the-Future West / WINNER project and completed in 2015 is substantially damaged. USAID/Haiti, Office of Economic Growth and Agricultural Development (EGAD) and Office of Infrastructure, Engineering, and Energy (OIEE) engaged PEREZ, APC to outline the possible causes of the damage.

2.0 OBJECTIVE

PEREZ, APC conducted a rapid on-site assessment of the performance of the Riviere Grise water diversion structure during Hurricane Matthew and resulting damages, an initial structural assessment of the diversion structure elements, and the compliance by the contractor with the project design parameters and environmental considerations during the design and construction.

The findings of this assessment will provide the basis for USAID/Haiti to decide whether or not to pursue an in-depth structural assessment, analysis of the design, construction, maintenance, and environmental factors that may have contributed to the damages at the site, and remedial actions to be undertaken

3.0 INTRODUCTION

The Riviere Grise barrage is located approximately 12 km east of the Port au Prince airport in the village of Dumay. It consists of an embankment diversion structure with sheet pile wall core (barrage) spanning the river, a series of 8 sheet pile spurs located upstream of the barrage and an intake/canal structure. A rectangular, sheet-pile-supported bulkhead form the right (east) abutment. Gates passing from barrage to canal are at the right abutment. The purpose of the project was to divert river flow to a canal and in turn convey it to nearby agricultural land.

The project suffered damage from several recent storms and most recently suffered substantial damage during the Hurricane Mathew storm in October 2016. The sheet pile wall core breached along 100 meters of its length and six of the eight sheet pile spurs suffered partial collapses. The gate structure was also damaged with one of the two gates pulled from its concrete anchored frame. This left the canal open to storm flow resulting in a substantial amount of sediment being deposited in the canal. In addition, a gabion wall protecting the shore between two of the sheet pile spurs was undercut leading to its partial collapse.

The structural layout and locations are shown on attached 100% Design Drawings C-02 and C-03, prepared by the Designer and provided in Annex A for ease of review of site features. Our site observations are presented in 21 sheets of 42 selected photographs, in Annex B.


4.0 DESK REVIEW

We reviewed the documents provided to us by USAID (desk review) to familiarize ourselves with the Project and specifically for potential insights into possible causes of the breach and associated damage. We therefore focused our review more directly on the technical engineering aspects and Site observations described in the documents rather than aspects ancillary to the structural performance (e.g. administrative documents, meeting minutes, economic analyses, etc.). Since the purpose of our review was for rapid evaluation of potential causes of the damage, we did not review for accuracy of calculations and drawings, facts, typographic and measurement inconsistencies, etc. Based on our review of the provided documents, we noted the following:

1. Initial Analysis of Alternatives: The Designer’s Alternatives Analysis (2011) appeared very concerned about accumulation of sediment and rising riverbed grades. We found no reference to a targeted design (or service) life for the Project in the sources provided, and although the Designer’s Alternatives Analysis (2011) mentions “Life Expectancy before Upgrade or Next Major Work,” it did not describe details of this or other considerations cited. The question of how long the proposed structure was supposed to last is therefore unclear. The report mentions a previously existing concrete barrage, now apparently buried, built in 1963. Our review of aerial photographs on Google Earth appears show the former concrete barrage in 2002 (though we are unsure if it was functioning), but by 2005 it no longer shows up in aerial photographs. The Designers identified 4 potential alternatives, including:

1. Alternative A. No Barrage Canal Gates – In our opinion, this title is a misnomer. This alternative consisted of an embankment barrage with rectangular concrete vault at the canal inlet, with 3 pairs of gates at increasing heights to be activated with increasing sediment infill of the gate approach/diversion channel. The Designers acknowledged the river diversion embankment to be highly erodible during overtopping from “every significant rain storm,” and requiring reconstruction as much as 15 times each year.

2. Alternative B. 150 Meter (m) Concrete Barrage – This was similar in location, design and function to the previous, now buried barrage, except about twice as long. It appears in sketches as a low head, Ogee-shaped concrete weir dam with canal along the river to channel water to the current canal location.

3. Alternative C. 300 m Steel Sheet Pile Barrage – The Alternatives Analysis describes this alternative essentially as was built. There is no mention, however, of spurs. The report predicts an overtopping depth of 1 meter over the 300-meter length in their design storm flows of 1200m3/s. This depth assumes a 4 m/s flow velocity.

4. Alternative D. Groundwater Intake – This alternative is based on four, Ranny Industry-type wells.

The report “qualitatively” ranked each of 12 criteria from 1=low to 3=high, totaling the results of the 12 criteria for each alternative. This method of comparison weighs each criterion equally, though this is rarely the case. Results for all alternatives were within 2 of 25 total points (out of a possible 36), and three or fewer points separated the alternatives. Given the highly subjective nature of the analysis, the rankings could be considered virtually the same.

Comparing alternatives 1 and 3, we found, and could conceive, of no explanation for, nor meaningful difference between, susceptibility to scour from overtopping in high flows, yet Alternative 1 was expected to be destroyed by scour/erosion as much as 15 times per year while no mention is made of maintenance for the selected Alternative 3.


2. Hydraulic Analysis Documentation: In our opinion, the hydraulic analyses provided in the documentation are insufficient to draw conclusions on adequacy of hydraulic design:

The Hydraulic and Hydrologic Technical Memorandum (2012), prepared by the Designer, summarizes results of a hydraulic model, performed using HEC-RAS software developed by the United States Army Corps of Engineers (USACE), for a preliminary barrage configuration of shorter length than constructed and without the upstream spurs. We found no hydraulic analysis documentation for the final design configuration, design of the spurs, nor for effects on water flows, elevations, and velocities at the barrage due to the spurs.

The same H&H Technical Memorandum predicts water velocity of 8.8 m/s in the design flood (for configuration without spurs) downstream of the barrage, and recommends that design should consider “the extremely high velocities.” The provided documentation included no further analytical evaluation of river velocities, nor effects of the velocities, with or without the spurs. We suspect that the addition of the spurs would further increase velocities in the middle of the channel compared to without the spurs, and that the increase in velocities would cause mounding and overtopping near the unarmored center of the barrage (where the breach occurred) during moderate and high flows, but would need to confirm by modeling hydraulics further.

The H&H Technical Memorandum predicts a probable hydraulic jump in the vicinity of the barrage and recommends further consideration of the jump during design. We found no documentation of further evaluation of a hydraulic jump nor effects of a hydraulic jump on the river and barrage.

3. Scour/Erosion Evaluation: We found no documentation indicating analytical evaluation of potential localized scour/erosion of the barrage or spurs, nor of river bed scour/erosion caused by either moderate to high flows/velocities or related to potential mining. In their August 2012 Preliminary Design Report, the Designer describes the potential for scour and recommends consideration of scour to be included in design development. Specifically, the Preliminary Design Report states the following:

Similar to deposition, scour may occur, particularly with significant events. There is significant uncertainty associated with scour, both in terms of location and magnitude. Scour conditions could include localized scour, which could remove existing deposition, and scour and erosion immediately downstream of the barrage structure. It is suspected that the portion of the reach downstream of the proposed barrage, where a probable hydraulic jump occurs, may be most likely to encounter scour conditions. Minor floods that cover the floodplain may also be a flow condition that produces scour conditions. Although it is difficult to quantify the scour conditions on the site because of uncertainty about site conditions, the potential for scour should be included in development of the design.

4. Design Changes Adding Spurs: As stated above, we found no analytical design or evaluation of the spurs, nor of their effects. Further, it appears the intent of the spurs was to increase river velocities near the middle of the channel. The Designer’s “Technical Memorandum of Evolution of the Riviere Grise Barrage Design” (2012) and a “Memorandum for Record” (USAID 2013) give some insight to the Designer’s approach to adding the spurs, as described below:

There were concerns with significant sediment deposition at the barrage that was anticipated to occur over time.

The Designer observed significant erosion of the left bank and deposition in the center of the channel following the August 2012 tropical storm Isaac and November 2012 Hurricane Sandy, which prompted addition of the spurs and increased length and number of sheet piles at the left bank.

The Design Evolution referenced above states: “A series of steel sheet pile berms has been added to both sides of the river upstream of the barrage and canal intake gates in an effort to control


the river direction, reduce erosion and help protect the barrage and gate structure. These berms are located and sized to help manage the flow of high velocity water and bed load through the project site.”

The implications of these statements are that the spurs (aka sheet pile berms) were intended to reduce erosion of the left and right banks and to carry bed load (sediment) past the barrage to reduce deposition by focusing higher-velocity flows through the center of the riverbed. To accomplish this, the statements imply that the spurs would confine the high velocity water that causes erosion and carries the bed load to the middle of the channel. This would presumably increase water velocities in the middle of the channel above the velocities predicted by the Designer without the spurs in the H&H Technical Memorandum that the designer characterized as “extremely high.” Despite these implications, we found no analytical evaluation of the hydraulics, bed load transport, or scour/erosion potential caused by higher velocity water likely resulting from the spurs.

5. Hydrologic Evaluation: The Designer’s Hydraulic and Hydrologic Technical Memorandum (2012) used a 300-mm, 100-year, 24-hour design rainfall from another river basin located “approximately 200 km from the project area.” In our opinion, the documentation does not adequately justify the use of this precipitation in design because it is from such great distance from the site. Furthermore, in our opinion, the precipitation of 300 mm appears to be less conservative compared to other recently-published guidelines for Haiti described later herein.

6. Flood Protection: Based on our desk review and observations, the barrage does not, and was not designed to, provide flood mitigation as it has very little storage capacity that could stage water and reduce downstream flows, however, in our opinion breach of the barrage could, in certain flow rates in our opinion, increase downstream flows potentially exacerbating downstream flooding and potentially endangering the public. Further evaluation may be warranted.

7. Gabion Design: We found no documentation of gabion analytical design (e.g. design water velocities, stability, etc.).

8. Sheet Pile Design: The Designer’s documentation (2013) indicates the sheet piles were designed for 0.9m (3 ft.) of differential water elevation and 8 or 10 ft. (2.4 to 3m) (discrepancy between two documents) of exposed wall height on the downstream side. The sheet piles do not appear to be designed to resist the scour depths that occurred.

9. Barrage Embankment Slopes: Sheet C-08 of the 100% Design Drawings (2013) shows 10H:1V earth fill embankment slopes to be constructed on the upstream and downstream sides of the barrage sheet piles. We found no specification of erosion protection for these embankment slopes in the documentation.

10. Construction Documentation: The provided documentation did not include reports or other documents from construction, such as construction inspection reports, change orders, material testing reports, QA/QC program, as-built drawings, etc, except one photograph taken at the end of construction. The photograph shows roughly 1 to 2 m of sheet piles exposed above the ground surface on each of upstream and downstream sides along barrage length, which differs from the embankment slopes shown on 100% Design Drawing C-08 (2013).

11. Post-Construction Changes: Photographs and documents between February 2015 and September 2016 indicate progressive erosion of as much as 4 to 5 m occurring downstream of the sheet pile gravel notch. The photographs also generally show a vertical drop at the downstream side of the barrage (exclusive of the notch) that appeared to be a meter or more, from end of construction until September 2016 maintenance when it was filled near the top of the sheet piles. The vertical drop differs from the design drawings and could potentially increase erosion on the downstream side by increasing plunge. The photographs and documents indicate maintenance performed between July and September 2015, in February 2016, and in September 2016, generally consisting of placing rip-rap


downstream of the notch and replacing material along the downstream face of the barrage in attempts to mitigate on-going erosion following flows that overtopped the sheet piles. Numerous documents identify on-going mining downstream of the barrage, lack of mining control, and attribute the erosion to the mining. Failure of one of the intake gates was noted in September 2016.

12. Hurricane Matthew Observations: The CLP October 2016 post-Hurricane Matthew report provides observations after barrage failure. Based on the provided documentation, the times of failure of the barrage, spurs, and gabions, as well as the precipitation, river elevations and flow rates at the times of failure are unknown.

During our review of the provided documentation, some questions arose for which we did not find information in the provided documents. We subsequently preliminarily reviewed additional, outside references for comparison, as follows:

1. Barrage Scour Depth: A preliminary scour estimate at the barrage downstream face (exclusive of the notch) suggests local scour would likely exceed the design unbraced sheet pile height of 2.4 to 3 m (cited above) and likely undermine the 6 m long sheet piles, irrespective of the downstream mining. According to Hydraulic Engineering Circular 23 Vol. 2 Ch. 3 Check Dams/Drop Structures (FHWA 2009), the method predicts 5.5 m of local scour for a 0.3 m vertical water drop, independent of soil grain size, in the stated design flow of 2,640 m3/s. This is regardless of mining, upstream or down.

2. Barrage Overtopping Protection: For the 10H:1V downstream embankment slope of the barrage, we preliminarily estimate rip-rap size would need to be on the order of 800 mm for the stated design flood, according to the method in Overtopping Protection for Dams (FEMA 2014). The barrage design specifies no rip rap on the barrage embankment slopes downstream of sheet piles, suggesting that the embankment slopes may not be adequately protected from erosion. Further, the stated design flood is, in our opinion, likely undersized.

3. River Bed Erosion: For the stated design flood with 8.8 m/s velocity, the river bed could be expected to erode based on particle sizes of cobbles and smaller. According to Geomorphology (Bloom 1998), cobble size particles (between about fist- and basketball-sized) and smaller are shown as erodible at velocities of 4 to 5 m/s and higher, and sand size particles are shown as erodible at velocities of 1 m/s and higher. These particle sizes make up the vast majority of riverbed.

4. Rainfall Design Guidelines: The Government of Haiti Analysis of Multiple Natural Hazards (March 26, 2010) noted lack of reliable, measured, historical data for rainfall and hydrology, and recommended design flood hazards of “Frequent” (200 mm/24 hr), “Rare” (400 mm/24 hr) and “Exceptional” (600 mm/24 hr., for hurricanes). A review of natural disaster history in Haiti reveals, in the last 30 years Haiti was subject to Hurricanes in 1988, 1994, 1998, 2004 (2), 2005 (2), 2008 (3), 2010, and 2016. Many non-hurricane-related floods occurred during that span. In our opinion, hurricanes should be expected during the design life of the barrage, or virtually any “permanent” river structure and, based on this guideline, design rainfall should be higher than 300 mm in 24 hours – perhaps 600 mm/24hr.

5. Hurricane Matthew Rainfall: The rainfall of Hurricane Matthew over the barrage drainage area was less than the 600 mm, 24-hour design guideline for hurricanes. We estimate about 530 mm average precipitation in the barrage upstream drainage from September 28 to October 6, 2016 (NASA 2016). An USAID Fact Sheet (USAID 2016), however, shows roughly between 200 and 250 mm south of Port-au-Prince between September 28 and October 5, 2016. While these precipitations occurred over multiple-days, the resulting peak flows may be roughly similar hydrologically to the design 300 mm, 24-hour precipitation, or less, depending on the precipitation amount and temporal distribution. Most notably, these peak flows would be substantially less than the “Exceptional” flood hazard recommended by the Haiti Government described above.

6. Google Earth Aerial Photographs of Mining: We reviewed Google Earth aerial photography taken over time for evidence of downstream mining. The review indicated mining at 3 downstream locations beginning as early as 2010, which is before the barrage was designed. In our opinion, the


potential for downstream mining could reasonably have been anticipated during design. We noted downstream mine processing and stockpiling as follows:

2000 m on west side: Mining noted on October 2010 aerial photograph, but not July 2010;

1200 m on east side: Mining noted on March 2012 aerial photograph;

1200 m on west side (current location): Mining noted on August 2012 aerial photograph, but not June 2012;

5.0 ON-SITE EVALUATION

The PEREZ, APC Team(Scott Nagel, RG and Robert Stephens, PE, ) mobilized to Port au Prince on Monday 14 November. The team met with USAID/Haiti on Tuesday morning at the U.S. Embassy in Port au Prince. Present for USAID was Robert Helmerick PE, Housing and Settlement Team Manager, Bryan Pittman USAID Washington and Robert MacLeod. USAID expressed their principle interests were:

1. Was the project designed correctly for the site conditions?

2. What led to the failure of the barrage and other components?

3. Should USAID reconstruct the project as per original?

The meeting lasted approximately one hour after which three USAID representatives and the Perez team caravanned to the project site. While the site is not far from the Embassy, the journey required 2 hours to make the 7 plus miles to the site underscoring the challenging conditions of the roads as well as traffic. Upon arrival we gathered at the canal head works located on the right (east) river bank and reviewed what we could see from that vantage point. This included the breached barrage, several of the damaged spurs and the damaged headworks gate. We visited the damaged gate works noting that the gate framework had been pulled from the concrete structure. We walked along as much of the barrage sheet piling as we could from the right (east) side of the river and we walked up river to view damage to the sheet pile spurs and gabions. With the initial site familiarization completed we left the site to Port au Prince in mid-afternoon for the 2-hour journey back.

On Wednesday the Perez team traveled to the site on its own and spent much of the day going over in detail the various project components. In addition to taking measurements and photographs of the components, the team was able to speak to locals about their observations of what happened during the storm. This was valuable anecdotal information. The team was also able to observe the extent and pace of mining downstream of the dam.

Because of time and access constraints, during our two days of site visits, we made most observations from the right (east) side of the river. We photogrammetrically documented our site visits, and selected 42 photographs for inclusion in this report.

The PEREZ, APC team attended two meetings at the Embassy on Thursday. The first was at 11 am and was with the USAID representatives that accompanied the team to the site on Tuesday, and with representatives of the Inspector General. The purpose of the meeting was to briefly review the Team’s findings and preliminary assessments prior to the following meeting with USAID, the Project Owners and attorneys. Both meetings included representatives from USAID and were led by senior USAID employee Rory Donohoe, Chief of the Office of Infrastructure, Energy, and Engineering, USAID/Haiti. Of particular interest to those present was whether the downstream removal of alluvial material had any impact on the performance of the barrage during Hurricane Matthew and aftermath. With our field evaluation and exit brief meetings complete, the Team returned to the U.S. on Friday.


6.0 FINDINGS

In general, our site observations are consistent with those described in the 13 October 2016 Post Hurricane Matthew Preliminary Assessment by Chanjé Lavi Plantè (CLP), though our conclusions and recommendations may differ. We attached more than 40 selected photographs of our site visits, showing structures and features described below.

Our desk review and on-site evaluation revealed highly complex site conditions characterized by a (normally) meandering to braided riverbed. Complex site conditions that merit consideration in design include, but are not necessarily limited to:

High influx of sediment; Relatively steep gradient; Highly erodible bed load (sediment) gradation predominately from fine sand to cobbles, with scattered

boulders; Highly variable precipitation and flows; The potential for hydraulic jump under the expected range of flows; Human factors including:

A lack of reliable nearby river flow and rainfall statistics for analyses and design;

Deforestation and excavation in the drainage area upstream;

Mining of river sediment downstream; and

The likely significant effects on fluvial morphology and river dynamics of the barrage, spurs and walls themselves.

The barrage breached from toppling of core sheet piles. The sheet piles lost support from downstream scour/erosion. The scour/erosion leading to failure may have been caused by any (or combination) of the following:

Locally high flow velocities from overtopping and plunging at the barrage; Globally high velocities from high flows and/or hydraulic jump; and/or Head cut/nick point erosion progressing from, and caused by, downstream mining.

We are concerned that attributing the scour to the single factor of downstream mining (as suggested by some others) may lead to reconstruction under the assumption that the mining may be prevented. We question whether the mining can realistically be regulated. Perhaps more importantly, we doubt that the barrage, as designed, with or without mining, may inadequately address design issues, most notably scour/erosion, in the complex river system, and believe reconstruction in kind is therefore ill-advised.

We conclude the following:

Mining was well known to be taking place within the 100 and 400-meter No Mining Zones, and more significantly 1200 to 2000 meters downstream, during evaluation, design and construction;

It is unlikely that the mining within the 400-meter No Mining Zone, by itself caused the breach. Pending further detailed evaluation as described herein, based on our preliminary evaluation of site

observations and limited available engineering and construction information, it is possible, and perhaps even likely, the breach would have occurred during the flows from Hurricane Matthew without the effects of downstream mining.

The following sections describe our more-detailed findings for respective components, followed by associated recommendations.


6.1 BARRAGE:

The goal of the barrage was to divert water from the riverbed to the canal where it was to be distributed for irrigation. Under low flows, during growing seasons, most of the water would be diverted to the canal by the barrage. In moderate flows the water would be regulated by the canal gates to divert some to irrigation, while the remaining flows would pass through the sheet pile gravel notch described later, about 30 meters wide and located about 45 meters south of the right abutment along the barrage.

The barrage failed (breached) near the middle over a roughly 100-meter-long section, during flows from Hurricane Matthew. The 100-meter-long breach extended from about 20 meters to 120 meters south of the sheet pile gravel notch, along the barrage. The barrage embankment, upstream and downstream of the breach, has been scoured away and sheet piles forming spillway/core toppled from lack of support. Since the sheet piles remained largely in interlock after toppling, they did not wash away and are mostly remaining and serviceable for re-use. If desired, the remaining sheets piles could be used to reconstruct the barrage, supplemented with additional sheets to replace the small percentage now missing.

The detailed sequence of events surrounding breach is currently uncertain, but may be important in determining cause and therefore preventing future similar incidents. We believe the sequence (and cause) may become clear with review of detailed hydrologic and hydraulic modeling of flows (HEC-HMS and HEC-RAS or similar), river/barrage capacity (HEC-RAS or similar), scour and dam breach analyses, as yet unavailable to us. If such analyses remain unavailable, we could develop our own models if requested.

Based on our observations and review of materials provided (list attached), we surmise that the barrage failed due to extensive (perhaps purely local) erosion of the barrage embankment downstream of the sheet piles, which supported the core structural elements (sheet piles). The resulting unbalanced (driving) forces of upstream embankment and water could no longer be resisted. Some length (as yet unknown) of unsupported sheet piles toppled over and a flood wave, on the order of the 3- to 6-meters high, likely erupted from the breach.

Post-hurricane site observations indicated significant erosion up and downstream of the barrage. The magnitude of erosion observed post hurricane may not be indicative of the scour/erosion that caused the breach. Specifically, it is unclear to us whether the magnitude of erosion observed post hurricane caused the breach, or the breach caused the magnitude of erosion observed.

We considered the possibility of head cut/nick point erosion from mining downstream. Based on our review of the little H&H information available to us, and our observation of the erosion and mining, we consider it just as likely that entrainment from high local velocities overtopping the barrage or plunging into the downstream embankment, and/or from the anticipated hydraulic jump downstream, could cause the breach irrespective of mining. In our desk review we noted concerns for flow velocities and scour in significantly lesser flows than the design flow. It is plausible that local factors (overtopping of the barrage in relatively lesser flows) caused localized scour downstream leading to breach and the resulting flood wave. This flood wave would likely cause significant additional erosion adjacent to and downstream of, the barrage, widening the breach. As the rush of water accelerated through the breach and out of the barrage impoundment, it would have entrained and carried sediment from upstream, as can be seen in the new cut banks and deepened channel. These new cut banks range in height from about 1.5 meters near the barrage, tapering to zero about 200 meters upstream of spur 1E.

The eroded cut bank and channel scour would have progressed downstream as well. From our observations, we estimate new downstream cut banks to be greater than 3 meters near the mining operations about 1200 meters downstream of the barrage.

The downstream cellular bulkhead portion of the sheet pile gravel notch, a spillway feature not included in the design, was added during construction. Its inclusion, and discussion surrounding it, are evidence that


the designer acknowledged potential for, and/or occurrence of, ground erosion downstream of the notch during overtopping, apparently after observations of erosion from flows before or during construction. Since both the notch and full length of barrage are designed to be overtopped, we question why the Designer concluded to place rip rap only around the notch after observing downstream erosion from flows overtopping the notch.

A complicating factor in barrage overtopping in moderate flows, as shown in the December 2015 CLP report, and we believe during higher flows of hurricane Matthew, may be the sediment deposition. Specifically, we suspect that sediment transport and deposition upstream led to obstruction of low areas near the gates and/or sheet pile gravel notch as alluded to in the CLP report. The high flow velocities, channeled by the spurs, focused and mounded flows elsewhere along the barrage, causing overtopping away from the notch, leading to scour. At high flows, such scour might lead to breach. Without the computer models, it remains uncertain.

The abundance of factors, some described above, complicate design and merit evaluation by computer modelling for cause of breach if reconstruction or alternative designs are considered.

6.2 SPURS

Because of time and access constraints, we made most observations from the east side of the river. We therefore observed Spurs 2W through 5W up close, while observations of 1W through 4W were made remotely from the east side of the river. In general, all spurs require some measure of maintenance/repair in the form of backfill and regrading. Six of the eight (2W, 3W, 4W, 2E, 3E and 4E) suffered more extensive damage including end collapse, misalignment and settlement. Theses spurs will likely require recovery and re-driving of some or even the majority of their sheet piles, and regrading. The high cut bank bounding the braided stream valley eroded near Spurs 2E and 4E and additional sheet piles and or other considerations may be needed.

Spur 4E and the adjacent gabion wall were significantly undermined, apparently scoured by the reversing flow of a backwater eddy formed immediately upstream of Spur 4E.

Review of spur design was considered as part of our scope of work, with review of available design and analyses, of which we found little in the documentation. For good or bad, they appear to be designed to focus flow to the middle of the braided stream channel valley, significantly away from the sheet pile gravel notch. We were not availed of the operative computer models needed for evaluation of design. It is clear, however, that the spurs impact the river dynamics greatly, and should be evaluated for their effects, positive and negative, on project outcome if further project evaluation is performed.

6.3 GABION WALLS

We received no documentation of the basis for and analyses of the gabion wall design. As was mentioned, the project gabion walls survived well, except for the 70-meter section upstream of Spur 4E, which was apparently undermined by the reversing flow of a backwater eddy formed immediately upstream of Spur 4E. River scour caused cut banks that approach and potentially threaten undermining additional sections of the gabion walls, and should be evaluated and addressed during repair/reconstruction if pursued.

6.4 GATE WORKS

The gate works are serviceable with relatively minor repairs. The abundance of sediment, as shown in the photographs, causes concern over the hydraulic function of the canal, and the resulting effects on gate operations. Based on our desk review, the gates were damaged in previous flooding, as the gate framework


had been pulled from the concrete structure. This damage was the result of improperly securing the gate frame during construction and, in our judgement is easily repaired.

The design is simple, consisting of a steel plate connected to frame at the bottom by a hinge, with the operating mechanism a cable/roller system. The gates are attached to the downstream side of the gate works, and therefore use water pressure to assist in opening, We question, given the location of the roller high above, if the gates can be fully closed with water pressure acting on them, and if this was assumed in design.

6.5 CANAL

We observed the canal from the Dumay Bridge to the gates. The canal remains in good condition, but is choked with sediment. A footbridge with canal gates exists about 50 meters upstream of the Dumay Bridge, and about 20 meters upstream of the footbridge is a side channel spill that returns canal flow to the river (see attached 100% Design Drawings C-02 and C-03). The footbridge is not shown on the drawings, but can be seen in the photographs (attached). The upstream sides of the footbridge is equipped with channels, ostensibly for stoplogs. The channels are unserviceable and need repair.

6.6 MINING

Mining of river alluvium for construction materials is a fact of life in Haiti and is an important part of local economies. The Riviere Grise is mined principally for sand and gravel. The coarsest material, including cobbles and boulders, is crushed locally for concrete aggregate.

Removal of material in close proximity to the barrage was recognized by the Designer as a potential destabilizing hazard. The Designer has asserted that the failure of the barrage was in large part due to illegal mining of alluvium downstream of the barrage. Exclusion zones were established within 10 meters and 100 meters downstream in design. After design, presumably during construction, the Designer/owner established a new No Mining Zone within 400 meters downstream and a steel marker (an h-pile, presumably the same as the ones used to anchor the right barrage abutment bulkhead) was installed on the left river bank to identify the exclusion zone boundary. However, the Team’s inquiries revealed that there appears to be no effective mechanisms for enforcement of these exclusions zones. The mining continues as observed during the Team’s time on site.

Based on our observations and estimates, we cannot account for the barrage failure and erosion (the volumes of materials scoured) simply from mining in the 400-meter No Mining Zone.

Mining observed within the 400-meter No Mining Zone consisted of hand loading cobbles and small boulders into single-axle, five yard dump trucks. Given the typical height of the load in the trucks, we estimate about 5 m3 per load. Based on our observations, we estimated about 2 trucks per hour during our two days on site – it took approximately 1 hour to load each truck. Our interviews with locals revealed that this work is carried out roughly 10 hours a day and 7 days a week. If these numbers are representative, and we believe they likely are, then the mining within the 400 meter downstream exclusion zone is insufficient to account for the observed volume of scour.

Based on our observations of rate, between March 2015 and October 2016 we estimate about 12,000 truckloads hauling a total volume of about 60,000m3 within the scoured area of the 400-meter No Mining Zone. Assuming the average depth of scour of about 1.7 meters over the zone as we observed, we estimate a mined area of about 35,000m2, or an equivalent square area less than 200 meters on each side. By comparison, we estimate area scoured by hurricane flow and barrage breach, solely within the 400-meter No Mining Zone, to be on the order of 136,000m2, and eroded volume to be about 230,000m3.


The scour area and volume exceed the estimates of mining by a factor of about 4 within the No Mining Zone.

Viewed another way, assuming no influx of additional sediment to the 400-meter No Mining Zone over the 20-month period March 2015 to October 2016 (a false, but very conservative assumption), we can account for less than 0.3 meters of material loss (average depth) due to mining within the No Mining Zone, while erosion from Hurricane flows appear to have caused on the order of 1.5 to 2 meters of erosion within the same zone at the new cut banks, and perhaps significantly more in the middle where failure occurred. Our review of structural calculations indicates the Designer assumed stability of the sheet piling for 2.5 to 3 meters of scour, meaning a loss of 0.3 meters should not threaten the barrage.

We observed other mining, about 1200 meters downstream of the barrage, taking place using two excavators, each separately loading one truck at a time. Mining downstream of the 400-meter No Mining Zone appears to be limited less by the productivity of the excavators than by the availability of trucks to haul the material. We estimate, based on our brief observations that these limitations result in a rate of truck hauling, at operations about 1200 meters downstream, on the order of twice that of the hand-operation upstream. With the higher-volume, tandem-axle trucks used at this location, this may result in roughly three times the rate of material removed as within the 400 meter No Mining Zone. More detailed evaluation of this may be warranted.

It is important to note that the materials removed are, to some degree, being replaced by alluvium transported from further upstream and significantly, by alluvium brought into the Riviere Grise channel from the large tributary on the left (south) bank immediately downstream of the barrage. To what degree the incoming alluvium replaces that which is removed is unknown and deserves a more detailed analysis. Based on the CLP reports and other’s photographs, relatively high flows during 2015 and 2016 brought significant amounts of additional sediment, both from upstream, and from the tributary immediately downstream on the west side forming a sizable alluvial fan. At least some of the upstream sediment settled at or upstream of the barrage. Much of this and the tributary alluvial fan were also scoured away by Hurricane Matthew.

7.0 RECOMMENDATIONS:

Given the information available to date, we cannot, at this time, recommend permanent (longer-term) reconstruction. If investment for permanent (longer-term) or temporary (short term) solution is still desired, or assignment of cause and/or blame, we recommend full examination of the details of design and construction, combined with a new alternatives/decision analysis.

We suspect that computer modelling would show that, even without mining, the structure as designed may be inadequate for the design considerations of this complex and dynamic riverine system. For example, we believe adequately addressing sediment deposition, flow velocities, riverbed scour, and hydraulic jump would require significant deviation from the current approach, possibly resulting in much higher cost. Temporary reconstruction in kind should be undertaken only in full consideration that the structure may breach again in the very near future.

For further consideration, we envision four major approaches, with possible associated subtasks:

1. Abandon project goals and site;

2. Reconstruct in kind:

a. Re-examine design details, including all design input and computer models;


b. Reconsider goals, effects and viability of spurs;

c. Conduct a multi-day assessment of mining operations in proximity to the barrage to better quantify the amount of material removed. This assessment should include interviews with those involved in the mining including diggers, truck drivers and crusher plant personnel; and

d. Further evaluate failure causes, as described below in 4, to reduce risk of reconstruction resulting the same failure.

3. Reconsider/consider alternate approaches in light of the potentially significant costs to make the current approach viable, including the following;

a. Concrete aqueduct (elevated canal, perhaps of precast, segmental concrete) possibly secured to the bedrock riverbed upstream at the former (abandoned) intake works, supported on drilled shafts or other deep foundations, or on deep, bulkhead cells created with the existing sheet piles, and running along the east cut bank to the existing gate works.

b. Temporary approaches (seasonal cofferdams) composed of the existing sheeting, gabions, super sacks or modular, precast concrete elements, etc., or combinations thereof; and/or

4. Further evaluate failure causes for use in reconstruction, redesign, or to establish fault:

a. Evaluate H&H computer models and revise or prepare anew as necessary; and

b. See 2.c., above.

8.0 LIST OF DOCUMENTS PROVIDED AND REVIEWED


CH2MHill (2011), "Alternatives Analysis for Riviere Gris Canal Intake," October 4, 2011

CH2MHill (2012), "Dynamic Lateral Earth Pressures, Mononobe-Okabe, AASHTO (2010)," February 23, 2012

CH2MHill (2012), "Test Pit Log," nos. TP-01, -02, -2.5, -03, -Weir, April 3, 2012

CH2MHill (2012), "Technical Memorandum, Hydraulic and Hydrologic Modeling, Riviere Grise Barrage, Haiti," July 25, 2012.

CH2MHill (2012), "Basis of Estimate, Haiti Diversion & Intake Structure," prepared for USAID, July 30, 2012.

CH2MHill (2012), "Draft Barrage à Bassin General pour le Perimetre Irrigue de la Rivière Grise, Croix des Bouquets, Haiti, Preliminary Design Report" August 2012.

CH2MHill (2012), "Draft Preliminary Geotechnical Investigation Report, Barrage à Bassin General pour le Perimetre Irrigue de la Riviere Grise, Croix des Bouquets, Haiti," August 2012.

CH2MHill (2012), "Appendix B Preliminary Design Drawings," July 2012, 12 sheets.

"Appendix C Basis of Cost," 1 cover page

"Economic Analysis for Design of the BARRAGE à BASSIN GENERAL POUR LE PERIMETRE IRRIGUE DE LA RIVIERE GRISE, CROIX DES BOUQUETS, HAITI," August 3, 2012, preparer not identified

CH2MHill (2012), "Appendix D Economic Evaluation Tables," August 3, 2012.

CH2MHill (2012), "Draft Barrage à Bassin General pour le Perimetre Irrigue de la Rivière Grise, Croix des Bouquets, Haiti, Preliminary Design Report" August 2012.

CH2MHill (2012), "Technical Memorandum, Evolution of the Riviere Grise Barrage Design," December 11, 2012

CH2MHill (2013), "Riviere Grise Control Gate Structure" calculations by A. Firth, January 2013

CH2MHill (2013), "Cul de Sac Canal Diversion Riviere Grise, USAID, Dumay, Haiti," 100% Design Drawings, 27 sheets, February 2013.

CH2MHill (2013), "Barrage Plan & Profile STA B0+250 to STA B0+500," Drawing C-07, February 2013, Addendum A

CH2MHill (2013), "Canal Plan & Profile STA C0+80 to STA C0+350," Drawing C-09, February 2013, Addendum A

CH2MHill (2013), "Canal Plan & Profile STA C0+350 to STA C0+620," Drawing C-10, February 2013, Addendum A

CH2MHill (2013), "Control Gates Plan," Drawing C-12, February 2013, Addendum A

CH2MHill (2013), "Control Gates Details & Sections," Drawing C-13, February 2013, Addendum A


CH2MHill (2013), "Details," Drawing D-01, February 2013, Addendum A

USAID/WINNER (2013), "Bidder's Conference for the Barrage on the Irrigated Perimeter of the Rivière Grise," February 28, 2013, Project Presentation and Site Visit.

CH2MHill (2013), "Addendum A to the Contract Documents," March 12, 2013

CH2MHill (2013), "Haiti Riviere Grise, Diversion Ret Structure, Anchor Case 1," calculations, March 27, 2013



USAID (2013), "Environmental Assessment for Riviere Grise Irrigation System Critical Infrastructure Rehabilitation," Contract No. EPP-I-0404-000400-00, May 2013.

"Attachment G, Construction contractor related PRELIMINARY mitigation measures," undated, preparer not identified

"Table 1. Economic Analysis for Design of the Barrage à Bassin General pour le Perimetre Irrigue de la Riviere Grise, Croix des Bouquets, Haiti," updated May 15, 2013, preparer not identified.

CH2MHill (2013), "Summary of Calculations/Attached" by D. Dailer, July 30, 2013

CH2MHill (2013), "Haiti Riviere Grise, Diversion Ret Structure, Cantilever Wall Barrage Section, CANT CASE 1," calculations, July 30, 2013

CH2MHill (2013), "Haiti Riviere Grise, Diversion Ret Structure, Cantilever Wall Barrage Section, CANT CASE 2," calculations, July 30, 2013

CH2MHill (2013), "Service Case Results, Normal High Water" calculations by Alex Firth, July 30, 2013

CH2MHill (2013), "Service Case Results, Dead plus 100 psf Live" calculations by Alex Firth, July 30, 2013

USACE (2013) "USACE Assessment Comments Barrage on Riviere Grise St. Croix des Bouquets, Haiti," September 18, 2013

CH2MHill (2013) "Memorandum, Meeting Minutes from September 20, 2013 Teleconference Discussing Responses to USACE Assessment," October 3, 2013

CH2MHill (2013) "Memorandum, Meeting Minutes from September 20, 2013 Teleconference Discussing Responses to USACE Assessment," October 3, 2013

USAID (2013) "Memorandum for Record, Comments to USACE's Analysis," undated but after September 30, 3013

USACE (2013) "Memorandum of Record, USACE Conclusion Assessment Comments Barrage on Riviere Grise St. Croix des Bouquets, Haiti," October 24, 2013


USAID (2013), "Action Memorandum for the Assistant Administrator for the Latin America and the Carribbean (LAC) Bureau," To Elizabeth Hogan, Acting Assistant Administrator, From John Groarke, Mission Director, November 7, 2013

Romain, F. (2015), Letter to Chemonics Foundation Haiti from SOTECH, "Ref.: USAID Prime Contract no EPP-I-04-04-00020-00. Fixed Price Subcontract No. FFP152," October 6, 2015.

Untitled, undated, preparer not identified, showing photos dated between February and October, 2015.

Kennedy, J. (2015), "USAID Mail - Barrage sur la Riviere Grise," 6 messages, October 27, 2015

Chanje Lavi Plantè (2015), "Rivière Grise Diversion Structure, Assessment Following the Rainfall of 12-1-2015," undated, but after December 3, 2015.

Kennedy, J. (2015a), "USAID Mail - Meeting at the MARNDR," December 10, 2015

Kennedy, J. (2015b), "USAID Mail - Meeting at the MARNDR," December 10, 2015.

Chanje Lavi Plantè (2016), "Rivière Grise Building Report," February 3, 2016.

"Background on the Riviere Grise Dam," undated, preparer not identified, file name dated February 11, 2016.

CH2MHill (2016), "Technical Report, Riviere Grise Barrage Conditions," March, 2016.

Chanje Lavi Plantè (2016), "Rivière Grise Diversion Structure, Report," September 13, 2016.

"Riviere Grise update," September 23, 2016, preparer not identified

Chanje Lavi Plantè (2016), "Post-Hurricane Matthew Preliminary assessment of Rivière Grise and Rivière Blanche irrigation systems," October 13, 2016.

"Emergency Engineering Assistance Statement of Work," undated, preparer not identified

"Economic Cost-Benefit Analysis," undated, preparer not identified

"Rivière Grise Deflector Spur Design Concept," undated, preparer not identified

Untitled, Undated, preparere not identified. Apparent computer software output. PDF File Name "DeepXcav Summary."

CH2MHill, "Haiti Riviere Grise, Lpile Analysis," calculations, undated

"Unit Price Bid Schedule (including Lump Sum) (in U.S. Dollars)," undated, preparer not identified.

"Economic Cost-Benefit Analysis," undated, preparer not identified

"Items Requested by USACE," prepared by USAID, undated.

"Comments to USACE's Analysis, Preparations of Meeting Minutes," undated, preparer not identified.

"Dumay Dam "Moving Forward" Memo," undated, preparer not identified


Untitled, undated, preparere not identified (file name: Summary for discussion on USACE's analysis)

9.0 ADDITIONAL REFERENCES

Google Earth 2016

Bloom, A.L. (1998) Geomorphology, 3rd Edition

US Department of Transportation, Federal Highway Administration (FHWA) (2009), "Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance - Third Edition," Hydraulic Engineering Circular 23, Publication No. FHWA-NHI-09-112, Volume 2, September 2009;

Government of Haiti (2010), "Analysis of Multiple Natural Hazards in Haiti (NATHAT)," March 26, 2010;

Federal Emergency Management Agency (2014) "Technical Manual: Overtopping Protection for Dams," FEMA P-1015, May 2014;

USAID (2016), "Preliminary Impacts of Hurricane Matthew," October 9, 2016, accessed at https://www.usaid.gov/matthew/fy01/fs02 on November 21, 2016;

National Aeronautics and Space Administration (NASA) Earth Observatory (2016), "Hurricane Matthew Soaks Haiti," accessed at http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=88893 on November 21, 2016;

National Aeronautics and Space Administration (NASA) (2016),“Multi-Satellite precipitation estimate with climatological gauge calibration – Late Run,” precipitation data, accessed at http://giovanni.gsfc.nasa.gov on November 21, 2016;

Annex A

Annex B

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JET November 30, 2016 Select Photographs

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Rivière Grise Barrage

Dumay, Haiti

RSS November 30, 2016

Photo No. 1 Description:Barrage from right abutment showing stream flowing through ~100m breach (failure).

11/16/2016

Photo No. 2 Description: Barrage showing sheet pile gravel notch, enhanced during construcion with the

downstream sheet pile wall. Locals mine sand and collect river debris upstream11/16/2016

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Photo No. 4 Description: Barrage sheet pile gravel notch showing sand infill within sheetpile cell and upstream

of main Barrage. Note downstream erosion along bank.11/16/2016


Photo No. 3 Description: Barrage right abutment from downstream riverbed showing about 3-4 meters of

erosion.11/16/2016


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Photo No. 5 Description: Barrage Breach - about 100m long in center of broad stream valley - viewed from left

end of sheet pile gravel notch. Note truck within 100m.11/16/2016

Photo No. 6 Description: Barrage Breach - right end. Note eroded bank showing sloped berm of original

construction with mantle of 1-4m of subsequent river material above.11/16/2016

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Photo No. 7 Description: Construction Evidence - eroded bank showing sloped berm of original construction

with mantle of 1-4m of subsequent river material above.11/16/2016

Photo No. 8 Description: Right abutment showing canal Intake (gates), vehicle access and canal channel bank

downstream of sheet piles11/16/2016

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Photo No. 9 Description:Canal

11/16/2016

Photo No. 10 Description: Abutment approach and canal just downstream of barrage abutment, showing

showing about 1m of sedimentation. 11/16/2016

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Photo No. 11 Description: Canal from Dumay Bridge showing gated footbridge. Not in design drawings -

apparently added to facilitate flow from canal to side channel spill outlet.11/16/2016

Photo No. 12 Description: Canal upstream from gated footbridge showing side channel spill outlet to river. Note

accumulated sediment from footbridge to sediment basin.11/16/2016

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Photo No. 13 Description: Canal Intake gates viewed from above on downstream side. Left gate (right in photo)

was not secured in accordance with design, and subsequently failed.11/15/2016

Photo No. 14 Description: Canal Intake gates viewed from upstream. Left gate failed, apparently in previous

flooding from lack of securing according to design.11/15/2016

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Photo No. 15 Description: Mining within 400m Downstream. A team of hand laborers, typically 4 to 10, hurls

cobble-sized stones into the bed of a single-axle dump truck.11/16/2016

Photo No. 16 Description: Mining within 400m Downstream. A single-axle dump truck (typical) loaded with

riverbed cobbles - about 5m3 typical load.11/16/2016

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Photo No. 17 Description: Mining on the order of 1200m Downstream of barrage. Note stockpile on left bank,

and equipment-supported mining activity in riverbed.11/16/2016

Photo No. 18 Description: Mining on the order of 1200m Downstream of barrage. Note tandem-axle dump truck

loaded by excavator.11/16/2016

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Photo No. 19 Description: Mining within 400m Downstream. Note steel H-pile at left across river marking the

downstream extent of 400m No Mining Zone. Laborers load trucks within zone.11/16/2016

Photo No. 20 Description: Gabion downstream training wall left of (supporting) right abutment and approach

road.11/16/2016

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Photo No. 22 Description: Wall failed between spurs 3E and 4E from erosion to and beneath wall and Spur 4E,

likely due to upstream swirl of backflow eddy during high flow.11/16/2016


Photo No. 21 Description: Gabion Wall between spurs 4E and 5E. Stream channel erosion has not reached the

toe of the wall, and wall remains servicable.11/16/2016


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JET November 30, 2016 Representative Photographs

Photo No. 24 Description: Panaroma, Standing Between Spurs 4E and 3E. Note failed gabion wall, and lack of soil embankment supporting spur sheet

piles.11/16/2016


Photo No. 23 Description:Panaroma, Standing Between Spurs 2E and 3E. Note slope failure scars at left in gorge at head of braided valley.

11/16/2016

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Photo No. 25 Description:Spur 1W

11/16/2016

Photo No. 26 Description:End of Spur 2E in foreground left; Spur 1W in background right

11/16/2016

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Photo No. 27 Description:Spur 2W background and Spur 2E foreground left

11/16/2016


11/16/2016

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Photo No. 29 Description:Spur 3W background and Spur 3E foreground

11/16/2016

Photo No. 30 Description:Spur 3W background and Spur 3E foreground

11/16/2016

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11/16/2016


11/16/2016

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Photo No. 33 Description: Spur 5 (aka 2E). Erosion of the riverbank progressed to the outboard end of the spur

at contact with the cut bank escarpment. 11/16/2016

Photo No. 34 Description:Spur 2E. Erosion caused loss of soil support.

11/16/2016

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Photo No. 36 Description:Spur 3E foreground. Note upstream erosion of river bank threatening loss of support.

11/16/2016


Photo No. 35 Description:Spur 2E failed, submerged end inundated by river braid.

11/16/2016


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Photo No. 37 Description: Spur 4E showing extensive upstream erosion and failed spur and gabion wall likely

due to upstream swirl of backflow eddy during high flow11/16/2016

Photo No. 38 Description: Spur 4E. Note toppling upstream from extensive erosion, leading to erosion on

upstream side as well.11/16/2016

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Photo No. 39 Description:Spur 4E background and Spur 5E foreground

11/16/2016

Photo No. 40 Description:Spur 5E. Note erosion.

11/16/2016

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Photo No. 41 Description: Upstream gorge: slope failure scars or escarpments mark the gorge walls upstream

of the braided streambed where the Barrage is located.11/16/2016

Photo No. 42 Description: Gorge upstream of the Barrage shows the dipping beds of parent rocks - source of the

riverbed sediment in the broad, braided section at the Barrage.11/16/2016

USAID/Haiti