customs and border protection report on border walls crossing washes and streams

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SBI-TI

PF 225 and VF 300

Border Fence Projects

Technical IPT

Final Report

California, Arizona,

New Mexico and Texas

Submitted to:

SBI

And

DEPARTMENT OF ARMY

Fort Worth District Corps of Engineers

Fort Worth, Texas

May 2009Project: IPT

Michael Baker Jr.,Phoenix, Arizona

Not for Constructio

Prepared by

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i

Executive Summary

On the afternoon of July 12, 2008, a severe monsoon resulted in significant flooding inthe area around Lukeville, Arizona. Shortly after the storm, the Associated Press

published an article titled Border Fence Design Gets a Second Look. That articledescribed the flooding in Lukeville and attributed it to the pedestrian fence (PF) recentlybuilt in the area (specifically the PF 225 segment D-2). On August 8, the National ParkService (NPS) issued a memorandum that also attributed the flooding of July 12 to thepedestrian fence, and, in particular, to poor drainage designs.

The U.S. Army Corps of Engineers (USACE), with the collaboration of Michael BakerCorp (Baker), produced an After Action Review (AAR) report that described the floodevent, why it happened, and recommended solutions (see Appendix A for a copy of theAAR). On October 22, 2008, a drainage summit was held at the Border Patrol station inDouglas, Arizona, to discuss the AAR and develop a plan for addressing the drainageissues as well as the resulting erosion and damage to the fencing. The summit alsodeveloped a preliminary approach to locating and correcting all other areas in which thePF 225 or VF (vehicle fence) 300 fence has the potential of creating similar incidents orhaving a high risk of flooding.

As a result of the drainage summit, an Integrated Project Team (IPT) was created toprepare a plan to identify all the areas subject to flooding because of PF 225 fencing andrecommend solutions for mitigating. (Appendix A also includes a copy of the IPTscharter.). This plan does not, and was never intended to, cover the legacy fences.

The IPT found that one of the factors contributing to the flooding was the collection ofdebris at fence sections built within wash areas. The debris builds-up on the fence

obstructed storm water from flowing freely across the fence, causing the water to rise anddivert from its natural flow pattern. In addition to the flooding, the debris build-up, whichsometimes reached a height of 6 feet, caused a water-fall effect on the other side of thefence resulting in major scour and erosion problems, and increasing the likelihood thatthe fence could be damaged or collapse.

The IPT further found that VF 300 fences resulted in no major drainage concerns becauseof obstructions. However, it expressed concern about the scour, erosion, stability, andlongevity of the vehicle fence, and whether it could withstand high-water pressurewithout being washed out. As a result, the IPT concluded that VF 300 also requiredmitigation (Legacy vehicle fences are not included in the analysis and mitigation)

The IPT collected data on all the washes where the PF 225 or VF 300 fence had beenconstructed (Legacy fences not included), and grouped them into three risk categories(high, medium, and low) using hydrologic and hydraulic criteria, such as flow rates,velocities, channel slopes, and water depth. (Appendices B and C present the list of the

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washes and their relative data; while Appendix D shows the locations of the PF 225 andVF 300 washes) The risk categories are defined as follows:

Category 1, Low Risk: There is little or no risk of debris collecting at the fence, orcausing any flooding, scour or erosion problems, or danger to the fence stability.

No action by IPT is anticipated.

Category 2, Medium Risk: There may be a risk of fence failing because offlooding hazards or debris collecting at the fence and causing floods, or scour orerosion problems. Further analysis is required to decide whether a retrofit to thefence is needed or if regular maintenance will suffice.

Category 3, High Risk: There is a high risk of failure because of water pressure,flooding, and scour or erosion problems. Removing or retrofitting the fence andinstalling scour protection are required. This category also includes all of the VF300 crossings located in a FEMA Zone A floodplain.

The IPT team validated the data, visited all the Category 2 and 3 washes (Appendix Eshows photos and site visit forms), and identified the VF washes that needed to bepermanently anchored to the ground, the PF washes that required fence retrofits, thewashes that only required scour protection, and the washes in which regular debrisremoval would suffice. These washes are as follows:

PF 225 crossings needing retrofit:

Segment A2K Washes J1&2 (47+09), J5 (70+50) Segment A2L Washes J6 (23+48), J9 (59+24) Segment D2 Washes E16, W13, E8, W17 Segment D5A Wash 2 (Mariposa) Segment D5B Washes 10 (Las Cuevitas), 44 Segment E2A Wash 5 (Montezuma) Segment E2B Washes M5 (BC Wash), M8 (Gringo wash), M14 (wash

33), M16 (first horseshoe), M21 (second horseshoe) Segment E3 Wash M1 (Christiansen) Wash east of Nogales Port of Entry (POE)

PF 225 crossings needing low water crossings (LWCs) and Rip Rap:

Segment A2A Wash 2 Segment A2D Wash 52+13, 60+57 Segment A2F Wash 5+44 Segment A2J Wash 51+75 Segment A2N Wash 3 Segment D2 Washes E19, E20, E31, E33, W1 Segment D5A Washes 1, 4 Segment D5B Washes 1, 28, 8, 9 (Barranca Honda), 26, 27

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Segment E2A Washes 7, 3, 6 Segment E3 Washes M3, M4, US2, US4, US5 Segment I1A Washes 3, 4 Segment L1 Washes 1, 4, 6

VF 300 crossings needing permanent anchoring system and scour protection(length of vehicle fence to be permanently anchored shown in brackets):

Segment CV2A Wash Y6 (180) Segment DV4B Washes 14 (150), A (240), 6 (270), 8 (70) Segment EV1A Washes 6 (100), 42 (200), 52 (50), 53 (100), 55

(50), 61 (70) Segment EV1B Wash F02 (200) Segment EV2B Wash 102 (240) Segment FV1B Washes C13 (Black draw - 450+200), C14 (hay

Hollow - 40+50+100), C6 (Silver Creek - 300+200). Segment HV3 Wash DA6 (50)

VF 300 crossings needing LWC and Rip Rap:

Segment BV1 Wash 100 (Pinto) Segment CV2 Washes 7, 16 Segment DV1 Washes 6, 12, 14, 17, 18, 19, 21, 22, 23 Segment DV3A Washes 1(San Simon Wash), 4 (Chukut Kuk) Segment DV4A Washes 1, 11 (LWC only), 17, 20, 35 (LWC only), 37,

41, 42 (LWC only), 43, 44, 45, 46 (LWC only), 5, 6 (LWC only), 9 (LWConly)

Segment DV4B Washes 17, 21, 9, 12 Segment DV4C Wash 52

Segment DV7 Washes 17, 35 Segment EV1A Washes 35, 38, 40, 45, 56, 58, 59, 60, 63, 66 Segment EV1B Wash F01 Segment FV1B Washes C17 (Cantina), C24, C4 (LWC only), C45

(LWC only), C50, C52 (LWC only), C10, C21, C5. Segment HV2 Washes 4, 8 Segment HV3 Washes DA1, DA4 Segment IV4 Wash 1 Segment JV3 Wash 1

All other crossings requiring future more frequent debris removal:

Segment A2C Washes 1+37, 16+03, 25+22, 6+95 Segment A2D Washes 36+35, 38+28, 39+02, 48+63 Segment A2F Wash 100 Segment A2g Washes 2, 8, 9 Segment A2I Washes 1+56, 16+29, 41+93, 44+41, 52+67, 7+67

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Segment A2J Washes E29, E30, E6, W2, W22, 3, 29, 31, 32, 40, 43,

43.5, 46, 55, 57, 58, 59, 20a, 25c, 471, 47b, 48a Segment D6 Washes 1, 3, 4 Segment E2A Washes 1, 2, 4

Segment E3 Wash M2B Segment DV1 Washes 7, 15 Segment DV2 Wash F06 Segment DV3A Washes 9, 12 Segment DV4A Washes 14, 15, 19, 29, 32, 33, 49 Segment FV1B Washes C20, C28 Segment HV2 Washes 6, 7, 9, 22 Segment HV4 Washes 3, 9 Segment IV2 Washes F02, F03, F04, F06 Segment JV2 Wash F01 Segment JV1A Wash 1

Segment JV1B Washes 10, 13, 16, 18.

The IPT also developed conceptual designs for pedestrian fence retrofits. These conceptsare provided in Figures F-1, F-2, and F-8 in Appendix F, with Figure F-8 showing therecommended retrofit. Appendix F also includes concepts for anchoring vehicle fences asalternative solutions to removing the fence (see Figures F-5, F-6, and F-7, with Figure F-7 showing the recommended solution).

Each of the recommended concepts needs to be further developed before it can be appliedto specific wash sites. For planning purposes, the IPT proposed the following rough orderof magnitude cost estimates for construction of the recommended solutions:

1. Retrofitting PF 225 fences: $9.5 million to $12.1 million2. Anchoring VF 300 fences: $1.8 million to 2.6 million

3. Building LWC and Riprap for PF 225: $1.2 million to $2.2 million

4. Building LWC and Riprap for VF 300: $2.2 million to $4.3 million.

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PageA

TABLE OF CONTENTS

Executive Summary ................................................................................................................... iSection 1. Introduction ..............................................................................................................1Section 2. Categorizing Washes ................................................................................................1Section 3. Site Visits ...................................................................................................................3Section 4. Considerations ..........................................................................................................5

PF 225 Proposed Solutions ......................................................................................................... 6Installation of Gates at Wash Crossings that can be Opened During Monsoon Season orPrior to Major Storms ............................................................................................................. 6Retrofit Existing Fence at Wash Crossings with Removable Bollards................................... 6

VF 300 Solutions ........................................................................................................................ 7Remove Existing Fence and Replace with Concrete Boulders or Tetra Pods ........................ 7Anchor Normandy Fences to Ground ..................................................................................... 7Remove Existing Fence and Replace with Widely Spaced Bollards ...................................... 8Remove Existing Fence Before Major Flood Events ............................................................. 8Rebuild Post and Rail Fences with Deeper Foundations ........................................................ 8

Section 5. Recommendations.....................................................................................................8PF 225 Recommendations for High-Risk Washes...................................................................... 8VF 300 Recommendations for High-Risk Washes ..................................................................... 9Recommendations for PF 225 Medium-Risk Wash Crossings ................................................. 10Recommendations for Other VF 300 Medium-Risk Wash Crossings ...................................... 11Prioritizing Criteria ................................................................................................................... 13

Section 6. ROM Cost Estimates ..............................................................................................14Retrofitting PF 225 Fences ....................................................................................................... 14Anchoring VF 300 Fences ........................................................................................................ 15Building Scour Protection for 32 PF 225 Crossings ................................................................. 15Building Scour Protection for Approximately 62 VF 300 Crossings ....................................... 15

Appendix A IPT Charter and After Action Review

Appendix B Wash Ranking Tables for PF 225

Appendix C Wash Ranking Tables for VF 300

Appendix D Summary

Appendix E Site Photos and Forms

Appendix F Concepts

Appendix G Rough Order of Magnitude Calculations

Appendix H Hec-Ras Models for Boulders in a Wash

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IPT Report

Project PF 225 AND VF 300Department of the Army

Fort Worth, Corps of Engineers

Forth Worth, Texas

MAY 2009

Section 1. Introduction

Pedestrian fence (PF) 225 D-2 near Lukeville, Arizona, was one of the first fencesegments constructed as part of the PF 225 Program. It was constructed using the design-build approach. Shortly after its completion, a large monsoon storm hit the area on July12, 2008, resulting in major flooding and damages along the border. This incident wasreported in an Associated Press article that indicated the barrier acted like a dam duringflash flood. In addition, the National Park Service (NPS), which manages the Organ

Pipe Memorial Park that is located adjacent to the D-2 segment, raised concerns to theU.S. Army Corps of Engineers (USACE) and U.S. Customs and Border Protection (CBP)that the fence caused the flooding. At CBPs request, USACE conducted a study todetermine whether the fence caused or contributed to the flooding. The results of thatstudy, including recommended solutions, were presented in an After Action Review(AAR) report produced by the USACE. (Appendix A presents a copy of this report.)

Shortly after the AAR was completed, a drainage summit was held at the Border Patrolstation in Douglas, Arizona on October 22, 2008. That summit discussed the AAR anddeveloped a plan for addressing the drainage issues as well as the resulting erosion anddamage to the fencing. It also created a preliminary approach to locate and correct anyother washes in which PF 225 or vehicle fence (VF) 300 was built with a likelihood ofpotentially creating similar issues.

The drainage summit further established an Integrated Project Team (IPT) to develop aplan for identifying all of the washes most likely be subject to flooding and severeerosion because of PF 225 and VF 300 fencing, and recommend solutions for mitigatingthose situations (Appendix A also shows the IPTs charter). This plan does not, and wasnever intended to, cover the situations caused by the legacy fences.

This report describes the steps and methods that the IPT used to identify and categorizethe drainage crossings, identifies potential solutions, and proposes rough order ofmagnitude (ROM) cost estimates to implement the solutions.

Section 2. Categorizing WashesThe first step in identifying the washes most susceptible to flooding and erosion was tocollect and analyze the hydrologic and hydraulic information for the washes in which PF225 and VF 300 fence segments crossed, and group them into the following threecategories:

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Category 1, Low Risk: There is little or no risk of debris collecting at the fence, orcausing any flooding, scour or erosion problems, or danger to the fence stability.No action is anticipated.

Category 2, Medium Risk: There may be a risk of the fence failing because of

flooding hazards, or because of debris collecting at the fence and causing floodsand scour or erosion problems. Further analysis is required to decide whether aretrofit to the fence is needed or if regular maintenance will suffice.

Category 3, High Risk: There is a high risk of failure because of water pressure,flooding, or scour and erosion problems. Removing or retrofitting the fence andinstalling scour protection are required. This category also includes all of the VF300 crossings located in a Federal Emergency Management Agency (FEMA)Zone A floodplain.

When available, the drainage designs and studies prepared for the PF 225 and VF 300projects were thoroughly reviewed for key data pertaining to the hydrology and

hydraulics of the washes. This review covered a 100-year storm event and focused on thefollowing factors:

Flow rate

Flow velocity

Water surface elevation

Flow direction

Channel slopes

Fence type (only for VF-300)

FEMA rating (or zone).

When this information was not available, the IPT conducted a separate hydraulic andhydrologic (H&H) analysis for the 100-year storm event.

In order to assign the drainage crossings to one of the three categories, the IPT used apreliminary set of desk-top criteria. The criteria were selected after analyzing multiplescenarios and consisted of the following factors:

Flow rate: Directly proportional to the risk of flooding (because water will backup) and its capacity to contain sediments and debris. Four thresholds wereselected: 100 cfs, 500 cfs, 1000 cfs, and 3000 cfs.

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Velocity: Directly proportional to scour and erosion and to the size of sedimentsand debris the flow may contain. Three thresholds were selected: 3 fps, 5 fps, and10 fps.

Flow depth: Directly proportional to the amount of debris and sediments the flow

can contain and to the damages that can be caused when flooding. Threethresholds were selected: 1 ft, 3 ft, and 5 ft.

Channel slope: Directly proportional to the turbulence the flow can have, whichleads to more erosion, scour, debris, and sediment transport. Three thresholdswere selected: 0.2 percent, 0.5 percent, and 1 percent.

The closer the factors for each wash were to the higher thresholds, the higher the categoryof the wash. Tables B-2 and C-6 (in Table 1) show how these factors are linked to thecategorization of the wash. All analysis used the 100-year storm event.

The desk-top analysis resulted in a preliminary grouping of the washes into one of thethree categories. Table 1 summarizes the various tables generated as a result of the desk-top analysis.

Table 1. Results of Desk-Top Analysis

Table Title Location

B-1 PF 225 Washes and Data Appendix B

B-2 Criteria Table Used to Categorize Washes Appendix B

B-3 PF 225: List of Category 2 Washes Appendix B

B-4 PF 225: List of Category 3 Washes Appendix B

C-5 VF 300 Washes and Data Appendix C

C-6 Criteria Table Used to Categorize Washes Appendix CC-7 VF 300: List of Category 2 Washes Appendix C

C-8 VF 300: List of Category 3 Washes Appendix C

D-9 Summary of Total Washes per Category andLocation

Appendix D

D-10 Longitude and Latitude of Washes Appendix D

Because the desk-top analysis and subsequent categorization were based primarily onhydraulic considerations, the IPT conducted site visits to confirm that the washes wereproperly categorized and determine if the recommended retrofits and upgrades werewarranted.

Section 3. Site Visits

The desk-top analysis yielded 106 Category 2 PF 225 fence/wash crossings and 21Category 3 PF 225 fence/wash crossings with more than 66 percent located in Arizona.

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(Appendixes B and C summarize the PF 225 and VF 300 Category 2 and 3 washcrossings.)

All Category 2 and 3 fence/wash crossings were validated through on-site visits for thefollowing purposes:

Obtain a better idea of the watershed makeup upstream of the wash crossing

Collect basic data concerning the as-built conditions of the fence and grates

Collect bed load data

Determine the likely long-term maintenance requirements following a majorstorm event and or at the end of the monsoon season

Asses the validity of the proposed concept recommendations.

The IPT did not visit the following washes:

All those in Category 1

All crossings associated with segment A-1 because this segment was still underdesign

All Category 2 PF 225 crossings with flow rates below 100 cfs or velocity below2 fps; these crossing were assumed to have no major flooding anticipated.

The site visits were conducted in the following order:1. The washes in New Mexico and Texas (specifically PF 225 Segments I-1A and L-

1) were visited in the early stages of the fence design phase and prior toconstruction; no additional site visits were warranted.

2. Naco to Douglas, Arizona, corridor (PF 225 E and F segments); these visitswere conducted on January 23, 2009; all the crossings within that corridor wereobserved.

3. Lukeville to Nogales, Arizona, corridor (PF 225 D segments); these visits wereconducted on January 30, 2009; all crossings within that corridor were observed.

4. San Diego, California, A-2 segments; these segments were observed on February12, 2009; all crossings of concern were visited and evaluated.

5. All vehicle fences that the IPT initially recommended be removed due toregulatory concerns were visited in 2008 and re-visited recently, as needed.

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To facilitate the field observations, a standard data collection form was prepared for eachcrossing and pre-populated with existing information, and then supplemented in the fieldwith additional information obtained during the site visit (such as specific grate designs

and fence type). The IPT also took photographs of each crossing visited. (Appendix Eprovides copies of the data collection forms and photographs.)

Section 4. Considerations

PF 225 fencing obstructs drainage flow every time a wash is crossed. With additionaldebris build-up, the International Boundary Water Commissions (IBWCs) criteria forrise in water surface elevations (set at 6 in rural areas and 3 in urban areas) can quicklybe exceeded. Proposed solutions for PF 225 fence projects focus on reducing thedestructive effects of debris at fence drainage crossings. The proposed solutions wouldenable drainage flow to cross the fence while minimizing the risk of flooding, scouring,

and structural failure. Those solutions also need to meet IBWC criteria. In California,Arizona, and New Mexico, PF 225 were built outside FEMAs floodplains, so FEMAcriteria did not apply. Some PF 225 segments in Texas, however, were planned to beconstructed in the tributary crossings of the Rio Grande and will be in FEMA floodplains.The collection of debris in those wash crossings and their impacts on the Rio GrandeFEMA floodplains are addressed in other drainage documents and beyond the scope ofthis report.

Given that the rise in water surface elevation (WSE) after the placement of VF 300fencing typically meets IBWCs criteria (described above), VF 300 fencing was allowedto be constructed in FEMA floodplains. During high-flood events (monsoon season),

however, the VF 300 fence in FEMA floodplains were to be removed and relocated to anoff-site staging area. Given the low rise in WSE, VF-300 fences were allowed to remainin place at all wash crossings permanently without violating IBWC criteria. That policyof leaving the VF 300 fence in floodplains was not considered during the original designphase of the fence project because of the time required to comply with FEMAsrequirements. The IPT was further tasked to assess the flood risks associated with leavingthe VF 300 fence in FEMA floodplains during flood events. Most of the VF 300 fenceplaced in drainage crossings was Normandy style fencing (VF-2), which is set on theground without a foundation. Few VF 300 segments with rail on post fencing (VF-1),with 6-foot deep post foundations were constructed in the floodplains. Both style fencestypically present minimal impacts and pose a very low flood risk. Giving the lack of

schedule constraints, FEMA compliance may be achieved while keeping the VF 300fence in the floodplains and will be addressed under a separate cover. The primaryconcern with the VF 300 drainage crossings is the stability and longevity of the VF-2fence and its ability to withstand flooding. Proposed solutions for VF-2 fencing willaddress maintaining the current fencing against high pressures from the water flowing at

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high velocities. For the remaining VF 300 fencing with foundations, the IPT consideredsolutions similar to those for the PF 225.

During weekly meetings, the IPT discussed multiple potential solutions to mitigate debris

build-up along PF 225 and VF 300 fence projects. The goal of those solutions was toalleviate debris build-up at the fence and the potential for scour and erosion during majorstorm events. The solutions are briefly discussed in the following subsections.

PF 225 Proposed Solutions

Installation of Gates at Wash Crossings that can be Opened DuringMonsoon Season or Prior to Major Storms

Multiple gate options were considered including swing, sluice, slide, and

retractable. The IPT compared the various types of gates using the followingfactors: drainage efficiency, ease of gate operation, visual deterrence, long-termmaintenance requirements, construction and life-cycle costs, and location (seeTable F-11 in Appendix F). It concluded that retrofitting the existing fence atwash crossings with a sluice gate (sliding vertically) was the best solution. Thisconcept would require the removal of existing grating or fencing, and retrofittingwith one or more vertical gates similar to the concept design depicted in Figure F-8 in Appendix F.

The required height of the gate openings was estimated to be 4 to 9 feet, andwould be a function of the flood water elevation and wash geometry of the

applicable wash. The required width and number of gates would also be afunction of each crossings characteristics. When the required number of gateopenings was known, a customized vertical gate system would be fabricated andinstalled at each crossing. The gates would be opened prior to monsoon or stormevents, thus providing a clear opening for the storm water and debris to flowthrough the fence with minimal obstruction. Following the monsoon or stormevents, the gates would be closed. For low-to-moderate storm events, the gatescould remain in the closed position.

Retrofit Existing Fence at Wash Crossings with Removable Bollards

This concept would require retrofitting the existing fence to allow only a portionof the fence bollards to be removable. By minimizing the height of the bollards tobe removable, operation and maintenance costs would be reduced and heavyequipment would not be required during installation. The required height of theremovable bollards (estimated at 4 to 9 feet) would be a function of the floodwater elevation and wash geometry. Prior to installing the removable bollards, all

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existing grates would be removed. If the fence has no grate, then another retrofitwould be required to replace the bollard fence with a frame similar to a fence withgrates so that there would be clear openings behind the removable bollards. Thebollards would be removed before monsoon or storm events, thus providing a

clear opening for the storm water and debris to flow through the fence withminimal obstruction. Following the monsoon or storm event, the bollards wouldbe reinstalled. For low-to-moderate storm events, the removable bollards wouldremain in the closed position. The bollards would not need to be removed forevery storm event, only those with the potential for major precipitation. Theconcept design is presented in Figures F-1 and F-2 in Appendix F. This optionwas not as promising as the previous gate option because of the need to find aplace to store after removal and to haul the bollards.

VF 300 Solutions

Remove Existing Fence and Replace with Concrete Boulders or TetraPods

These structures would be large concrete blocks strategically placed in the bed ofthe main wash to stop vehicles from crossing. The IPT performed preliminarycalculations to estimate the size of a concrete cubes required to resist hydrostaticsliding forces. Those calculations showed that each of these structures would needto be between 8 to 12 feet, depending on the velocity of the flow. (Appendix Fshows typical images of similar structures and the IPTs calculations.)

To determine the order of magnitude impact that the concrete blocks or boulderswould have on a water surface elevation, the IPT created a Hec-Ras Model fortwo typical washes: the Cantina Wash (Segment FV-1B Wash C17) and HayHollow Wash (Segment FV-1B wash C14). An analysis showed that installingsuch an obstruction would cause the water surface elevation to rise to a levelhigher than the limit set by IBWC (see Appendix H). In addition, the obstructionswould need to meet FEMAs requirements and regulations for building in afloodplain. For the above reason, the IPT does not recommend this solution.

Anchor Normandy Fences to Ground

This solution calls for installing deep concrete drilled shafts or deep embeddedmetal columns connected to the existing Normandy fence. This approach wouldanchor the fence in place even when it is subjected to the high pressures of stormflows. Details of the Normandy fence and the anchoring system are shown inFigures F-6 and F-7 in Appendix F. The IPT recommends this solution.

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Remove Existing Fence and Replace with Widely Spaced Bollards

The bollards would need to be clearly separated from each other, but not morethan 4 feet in order to stop vehicles from crossing. The bollards would also need

to be embedded into the ground to sustain the forces of the flow and the scourdepth. The footings for these bollards would likely be concrete drilled shafts toestimated depths of 25 to 30 feet. Figure F-5 in Appendix F shows the details ofsuch a fence. For hydraulic and scour reasons this solution is not recommendedfor high-flow Category 3 washes, but may be considered for lower Category 3washes. This option is not operationally desirable because of the open spacebetween bollards.

Remove Existing Fence Before Major Flood Events

In this solution, the Normandy fence would be modified to facilitate easy and

quick removal with heavy machinery. The VF would be removed from the mainchannel of the wash prior to the monsoon season or a major storm event. Thisoption is not operationally desirable because of the need to find a place to storethe fence after removal and the need to haul the fence, both actions are labor andcost prohibitive.

Rebuild Post and Rail Fences with Deeper Foundations

This solution is less tamper proof then the recommended option, so it is notoperationally desirable.

Section 5. Recommendations

PF 225 Recommendations for High-Risk Washes

The IPT recommends that the existing drainage grates be removed and retrofittedwith vertical slides gate, concrete apron, and rip rap similar to the concept designdepicted in Figure F-8 in Appendix F. Table 2 summarizes the recommendedactions by order of priority.

Table 2. Recommendations: PF 225 High-Risk Washes

Fence ID Wash IDs Category Fence typeFlow

direction

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Fence ID Wash IDs Category Fence typeFlow

direction

NogalesPOE

Approx 500 feetEast of Nogales

POE 3 Bollards N

D-2

E-16 3 Mesh with grates S

W13 3 Mesh with grates S

E8 2 Mesh with grates S

W17 2 Mesh with grates S

E3 M1 (Christiansen) 3 Bollards with grates N

D-5B10 (Las Cuevita) 3 Bollards N

44 3 Bollards N

D-5A 2 (Mariposa) 3 Bollards N

E2A 5 (Montezuma) 3 Bollards with grates S

E2B

M5 (BC Wash) 2 Staggered bollards N

M8 (gringo Wash) 3 Staggered bollards S

M14 (Wash 33) 2 Staggered bollards N

M16 (1st

Horseshoe) 3 Staggered bollards N

M21 (2nd

horseshoe) 2 Staggered bollards N

A2L J6 3 Bollards with grates N

J9 3 Bollards with grates N

A2K J-1&2 (47+09) 3 Bollards with grates S

J-5 (70+50) 3 Bollards with grates N

VF 300 Recommendations for High-Risk Washes

For the very few washes with rail-on-post fence that are in high risk washes, theIPT recommends removing the existing post foundation, post, and rail and replacethem with deep concrete shaft foundations, new posts with removable rails,concrete aprons, and rip rap.

For the washes with Normandy fence, the IPT further recommends that the fencebe anchored as shown in Figure F-7 in Appendix F, adding concrete aprons andRipRap. Table 3 lists the washes to be retrofitted in order of priority.

Table 3. Recommendations: VF 300 High-Risk Washes

Segment Crossing CategoryApproximate

fence length to beanchored (ft)

FEMAcrossing

FV-1B C6 Silver Creek 3 300+200 Zone A

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Segment Crossing CategoryApproximate

fence length to beanchored (ft)

FEMAcrossing

C13 Black Draw 3 450+200 Zone A

C14 Hay Hollow 3 40+50+100 Zone A

EV2B 102 3 240 Zone A

EV1A

6 3 100 Zone D

42 3 200 Zone D

52 2 50 Zone D

53 3 100 Zone D

55 2 50 Zone D

61 3 70 Zone D

DV4B

14 3 150 Zone D

A 3 240 Zone D

6 3 270 Zone D

8 2 70 Zone D

EV1B F023 200

Zone BHV-3 DA6 2 50 Zone X

CV2A Y6 2 180 Zone DNote: Short definitions of FEMA zones: Zone A = area with 1 percent annual

chance floodplain; Zone C = areas outside the 1 percent annual chance floodplain; Zone D = areaswhere flood hazards are possible, but undetermined; Zone X = areas outside the 1 percent annualchance floodplain.

Recommendations for PF 225 Medium-Risk Wash Crossings

For PF 225 fence wash crossings that do not warrant retrofitting with the sluicebollard gate concept design but are subjected to scour and erosion problems, the

IPT recommends the installation of Low Water Crossings (LWC) and rip rap.Figure F-3 and F-4 in Appendix F provide details of the LWC and Rip Rap foreach flow direction.

The PF 225 fence segments and their associated wash crossings that should haveLWC and rip rap installed are summarized by order of priority in Table 4.

Table 4. Recommendations: PF 225 Medium-Risk Washes

Fence ID Wash IDs Fence typeFlow

direction

A2A 2 Bollards SA2D 52+13 Bollards with grates S

E2A 3 Bollards with grates SA2J 51+75 Bollards with grates N

A2E 5+44 Bollards with grates SA2D 60+57 Bollards with grates SD5B 27 Bollards N

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Fence ID Wash IDs Fence typeFlow

direction

D5A 4 Bollards ND5B 28 Bollards with grates S

D2 E31 Mesh with grates S

E2A 7 Bollards with grates SD2 W1 Mesh with grates S

D5B 9 (Barranca Honda) Bollards ND5A 1 Bollards N

A2N 3 Bollards with grates ND2 E33 Mesh with grates S

E3 US4 Bollards with grates SE3 US2 Bollards S

E3 M4 Bollards with grates ND5B 8 Bollards with grates NE3 US5 Bollards S

E2A 6 Bollards with grates SL1 4 Bollards S

D2 E20 Mesh with grates SL1 1 Bollards S

D5B 1 Bollards ND5B 26 Bollards N

L1 6 Bollards SE3 M3 Bollards with grates ND2 E19 Mesh with grates S

I1A Subbasin 3 Bollards SI1A Subbasin 4 Bollards S

Recommendations for Other VF 300 Medium-Risk Wash Crossings

The remaining vehicle fence segments and their associated wash crossings thatshould have LWC and rip rap installed are summarized in Table 5 by order ofpriority.

Table 5. Recommendations: VF 300 Medium-Risk Washes

Segment CrossingRequired

installationFence type

Flowdirection

FEMAcrossing

BV-1 100 (Pinto) LWC & RipRap Normandy N Zone A

JV3 1 LWC & RipRap Normandy S Zone X

DV-3A 1 (San Simon) LWC & RipRap Rail on post S Zone D

DV-3A 4 (Chukut kuk) LWC & RipRap Rail on post S Zone D

HV-2 8 LWC & RipRap Normandy N Zone X

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Flowdirection

FEMAcrossing

DV-7 35 LWC & RipRap Rail and post S Zone DFV-1B C5 LWC & RipRap Rail and post S Zone X

EV-1A 63 LWC & RipRap Normandy S Zone D

DV-4B 12 LWC & RipRap Rail and post S Zone D

DV-7 17 LWC & RipRap Rail and post S Zone DDV-4A Basin 11 LWC Only Normandy S Zone D

FV-1B C21 LWC & RipRap Rail and post S Zone X

HV-3 DA1 LWC & RipRap Normandy N Zone X

FV-1B C17 (Cantina) LWC & RipRap Normandy S Zone X

DV-4A Basin 42 LWC Only Normandy S Zone D



FV-1B C50 LWC & RipRap Normandy S Zone XHV-2 4 LWC & RipRap Normandy N Zone X


FV-1B C4 LWC Only Normandy N Zone D


EV-1B EV-1B_F-01 LWC & RipRap Normandy S Zone D

DV-4A Basin 1 LWC & RipRap Normandy S Zone D

FV-1B C24 LWC & RipRap Normandy N Zone X


DV-1 18 LWC & RipRap Normandy S Zone D



DV-4A Basin 46 LWC Only Normandy S Zone DDV-4A Basin 17 LWC & RipRap Normandy S Zone D


HV-3 DA4 LWC & RipRap Normandy S Zone X







FV-1B C52 LWC Only Normandy S Zone X

CV-2 16 LWC & RipRap Normandy S Zone DDV-4B 21 LWC & RipRap Rail and post S Zone D


CV-2 7 LWC & RipRap Rail on post S Zone D



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Flowdirection

FEMAcrossing


FV-1B C45 LWC Only Normandy S Zone X

DV-4C Basin 52 LWC & RipRap Normandy S Zone D










FV-1B C10 LWC & RipRap Normandy S Zone XDV-1 6 LWC & RipRap Normandy S Zone D


IV4 1 LWC & RipRap Rail on post S Zone X

Note: Zones A, C, D, and Z are as defined in Table 3.

Prioritizing Criteria

The risks facing the PF 225 and VF 300 fences have the following order ofpriority:

1. Obstruction to the flow

2. Risking the structural integrity of VFs

3. Scour and erosion.

To mitigate these risks, the IPT recommends implementing the following fourprojects listed in their order of priorities:

1. Retrofit PF with a sluice bollard gate and add scour protection

2. Anchor the VF and add scour protection

3. Add low-water crossings to washes with PFs

4. Add low-water crossings to washes with VFs.

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14

Each of these projects has several segments, which are listed below in priorityorder:

Highest priority: Washes falling in FEMA Zone A

Higher priority: Washes with high velocity and high-flow depth

High priority: Washes with lower velocity.

Section 6. ROM Cost Estimates

The IPT calculated unit costs to install a sluice Bollard gate, anchor a vehiclefence, and scour protection. Appendix G shows the details of the costs presentedin this section.

Retrofitting PF 225 Fences

Retrofitting approximately 160 gates into a fence with no grates:

Min:Max:

Retrofitting approximately 359 gates into a fence with grates:

Min:Max:

Scour protection for approximately 3,800 to 4,000 feet:

Min:Max:

Mobilization/demobilization and contingency:

Min: 3% + 15% = 18%Max: 5% + 20% = 25%

Total approximate PF 225 retrofit cost:

Min:Max

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15

Anchoring VF 300 Fences

Anchoring approximately 3,310 feet of Normandy fence:

Number of anchors = 3310/16 = 207Min:Max:

Scour protection for approximately 5,500 to 6,000 feet:

Min:Max:


Min: 3% + 15% = 18%Max: 5% + 20% = 25%

Total approximate VF 300 retrofit cost:

Min:Max:

Building Scour Protection for 32 PF 225 Crossings

Low-water crossings length:

Min length: 32 x 150 = 4,800Max length: 32 x 250 = 8,000


Min: 3% + 15% = 18%Max: 5% + 20% = 25%

Total approximate PF 225 crossings scour protection cost:

Min:Max:

Building Scour Protection for Approximately 62 VF 300 Crossings

Low -water crossings length:

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16

Min length: 62 x 150 = 9,300Max length: 62 x 250 = 15,500


Min: 3% + 15% = 18%Max: 5% + 20% = 25%

Total approximate VF 300 crossings scour protection cost:

Min:Max:

Table 6 summarizes the costs for these recommendations.

Table 6. Summary of Costs

Min MaxRetrofitPF225fenceAnchorVF300fenceScourprotectionforPF225crossingsScourprotectionforVF300crossingsTotal

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IPT Report

APPENDIX A

IPT Charter & After Action Review

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Project Name

SBI-TIPF-225 and VF-300 Border Fence projectsTechnical IPT

Understanding of the Need

The major factor impacting the drainage across the fence is the debris. At wash crossings, the debris starts tobuild up, clogging the fence openings and changing the hydraulics of the flow. This has a direct impact tohigher scour and erosion problems, as well as increase in water surface elevation due to the backwater effect.Controlling the Debris during and after the storm event is needed in order to keep the flooding under control.

Another factor include the high pressure of the flow carrying heavy debris (i.e. waterbed rocks) and causingthe removal of the bollards from the ground and transported with the flow downstream, causing high safetyissues. The bollard fence need to have a special structural and foundation design or it must be removed fromthe wash during monsoon seasons.

Deliverables/Objectives

To address the long term and short term solutions that will mitigate the drainage issues described above,and coming up with a maintenance program to sustain the fence and the different alternatives.

Deliverables include design details of the different solutions, locations where these solutions need to beimplemented and when, requirements for a maintenance program.

Preliminary Statement of Work

The following steps describe the method used to reach a solution. Additional steps may be added pendingmeeting outcomes.Step 1: Collect all the crossings and group them into three flooding risk categories: Low, Intermediate andHigh. This step include coming up with criteria and thresholds that will be used to group these crossings.Step 2: Divide the intermediate risk crossings into two categories: High priority (currently under construction)and Low priority (Constructed or Soon to be under construction). This step Assumes that the Low riskcrossings dont require any action, and at high risk crossings will use a temporary fence that will be removedduring the monsoon seasonStep 3: Provide a short term solution for the high priority crossings. Find a strategy or a way to implement thissolution, with its impact on the budget and construction schedule.Step 4: Provide a long term solution for the high and low priority crossing. Find a strategy or a way toimplement this solution, with its impact on the budget and schedule of the incoming construction.Step 5: Provide maintenance requirements for all three flooding risk categories

In Scope

- Review of hydrologic and hydraulic analysis produced for each report

-Produce criteria (non scientific) and have it approved by the IPT team. These criteria will set thethresholds.

- Produce a typical detail for each solution.- Include the pros and cons for each detail- Preliminary cost estimate- Produce meeting minutes

Known Risks- Fences soon to be constructed may not include the proposed solutions in order to meet the deadlines- The proposed solutions may have to be implemented after the fence is constructed (alteration to the

fence already installed)

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After Action Review (AAR)

The Monsoon Flooding Event on 12 July 2008 in

Lukeville, Arizona

AndThe Effects of the International Boundary Fence

23 September 2008

US Army Corps of Engineers

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After Action Review (AAR)The Monsoon Flooding Event on 12 July 2008 in Lukeville, Arizona

And

The Effects of the International Boundary Fence23 September 2008

PurposeThe purpose of this After Action Review is to determine the cause of the flooding inLukeville, Arizona on July 12, 2008 and to determine the implications of the D-2

Lukeville border fence on drainage and environmental conditions.

Introduction

On the afternoon of July 12, 2008, a severe monsoon event created flooding in the

Lukeville, Arizona area. During this event, the Organ Pipe Cactus National Monument

(OPCNM) recorded 1.99 inches of rainfall over a ninety (90) minute period. This eventwas the first significant rainfall of the summer. Of the area along the fence involved in

the flooding, three noted locations of concern are the Lukeville Port of Entry (POE), the

Gringo Pass Store and the Sonoyta, Sonora, Mexican Port of Entry.

List of Documentation and References1. Request For Proposal, D-2:AJO 3.1 Miles East to 2.1 Miles West of Lukeville, AZ

POE2. Letter: Gringo Pass, Inc. July 14, 2008 to Lee Baiza, Superintendent: Organ Pipe

Cactus National Monument

3. U.S. Border Patrol:Monsoon Storm Flooding in Lukeville, Arizona Area4. National Park Service, Effects if the International Boundary Pedestrian Fence in the

Vicinity of Lukeville, Arizona, on Drainage Systems and Infrastructure, Organ Pipe

Cactus National MonumentAugust 20085. Kiewit/HNTB. Project D-2 AJO 3.1 Miles East to 2.1 Miles West of Lukeville, AZ

Poe Design Complete package: Drainage Report February 2008.6. U.S. Border Patrol, Tucson Sector. Final Environmental Assessment for the proposed

installation, operation, and maintenance of primary pedestrian fence near Lukeville,

Arizona February 20087. National Weather Service Advanced Hydrologic Prediction Service Precipitation

Analysis

Review of Documentation

The following sections are summaries of the documentation reviewed for this report.

The Request for Proposal (RFP) for D-2, Section 1.9.4. Drainage Report and itsaccompanying technical appendix (Ref. 1) detailed the requirements for the contractor,

Kiewit Western Co., under Contract W912BV-07-D-2022, CQ02. The RFP had a

preliminary drainage report and a list of minimum requirements for the contractor toperform which included 1) review of existing drainage and field verify existing wash

locations, 2) provide delineation maps, 3) determine local drainage runoff and sheet flow

conditions as they cross the fence location, 4) provide final hydraulics calculations by

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Figure 1: Watershed Delineation by Contractor (Ref. 5)

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determining velocities associated with select fence type and rise in water surface

elevation, 5) provide final calculations on scour and/or long term degradation, 6) provide

details for fence wash crossing which satisfies rise in water surface elevation, 7) providedetails for protection against scour and long-term degradation, 8) show that cut fill

operation do not adversely affect the natural drainage patterns, 9) provide hydraulicdesign and details for any other site drainage improvements, 10) provide final drainagereport and 11) coordinate with all applicable reviewing agencies. The included

preliminary report by Michael Baker Inc. shows a preliminary hydrologic analysis but no

analysis regarding hydraulics or scour.

A letter supplied by of Gringo Pass Inc to Lee Baiza, Superintendent of the

Organ Pipe Cactus National Monument (Ref. 2) stated that the July 12 storm flooded the

entire Gringo Pass Store. A flood occurred last year which flooded the back of the store.It was stated that Border Patrol vehicles were getting stuck in mud and debris.

A report by the Office of Border Patrol (OBP) on Monsoon Storm Flooding in Lukeville,Az. (Ref. 3) details three flooding issues: 1) the Lukeville POE, 2) the Gringo Pass store

and 3) the Mexican POE. The Lukeville POE contains an atrium in the center of the

building with a dry well system that drains into a 2.5 inch dry well that takes water out of

the building proper. Contributing factors of flooding stated in the report are the buildingfoundation at equal grade as the atrium and the end of the drain having been covered with

earth. It was stated that the Gringo Pass store flooding was due to a combination of

construction on low elevation, obstruction of flow from vegetation on the fence gate,concrete rubble south of the fence in the wash, the amount of rain and its intensity, and

the vegetative ground cover spread (mulch) within the drainage location. The mulchmaterial was removed vegetation from the placement of the border fence that was given

to the OPCNM to grind into mulch and place in the watershed. Flooding at the Mexican

Port of Entry is attributed to the structure, which is 1 ft below the existing grade, beingbuilt in the flood plain. The contractor, the Corps of Engineers (USACE) and OBP

personnel met on site to discuss possible causes. Elevation surveys of the areas were

performed to determine the Gringo Pass store and the Mexican POE were in thefloodplain. Also, it was reasoned that the first flood of the season would produce most of

the debris. The recommendations made were 1) placement of a pressure release system

in the fence on the west side of the wash, 2) insure that the washes are channeled properly

and that debris does not build up against the fence and 3) retrofit sections of the existingfence with a hybrid 4 bollard design to facilitate maximum water flow.

A report from the Organ Pipe Cactus National Monument (OPCNM) of the Nation ParkService (NPS) (Ref. 4) documents the July 12 th event and the performance of the fence

during a flash food and the effects on the floodplains and channel morphology. The July

12 event recorded 1.99 inches of within 90 minutes based on a climate station for theNational Atmospheric Deposition Program operated by the Nation Park Service. The

location of this measurement was at the OPCNM headquarters. Another rain gage

located 1.5 miles west-northwest of the Lukeville measured 1.25 inches in 105 minutes.The radar rainfall estimate for that day from the National Oceanic and Atmospheric

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Administration (NOAA) shows the thunderstorm centered north of Lukeville, in thevicinity of the OPCNM headquarters, with a very small region receiving rain in excess of

2.5 inches. The NPS states that the July 12 th storm occurs regularly within OPCNM,

placing the reoccurrence between once every 3-5 years. NPS states that the drainageareas delineated by the Contractor are for W13 or Victoria Wash and E31 or Estes

wash are undersized because OPCNM delineations are more accurate. United StatesGeographic Survey (USGS) equations used were not applicable in areas under 1730 ft inelevation. Mainstream flood flows were contained in flow reaching the fence however

a combination of debris flow blockage and subsurface sediment flow impeded by the

foundation of the fence contributed to the flooding. Documentation of water levels was

up to 7 ft above the foundation wall at W13. Blockages caused lateral flows at the fencewill a) cause scour and b) cause flow to enter different washes. The blockages at

Headquarters Wash (W1) were the cause of the Gringo Store and Lukeville POE

flooding. Ponding of water was not noticed at the fence for the July 12th

storm, howeverit was noticed upstream of the fence where patrol road elevations are above natural

surface elevations; in turn, vegetation change is expected in locations where water pools.

The conclusion that a) the accelerated scour will comprise the integrity of the fence b)lateral flows will erode the patrol road and the pedestrian fence. c) Vegetation will

change which will change rainfall retention, d) riparian vegetation will change due to the

increase of sedimentation, and e) channel morphology will change over time where

channelized water will gully.

The design of the pedestrian fence was accomplishment by Kiewit with the drainage

report by HNTB (Ref. 5). The report requirements were as detailed in the RFP. Also,design criteria included the United States International Boundary and Water Commission

(USIBWC) limit of the water surface elevation rise due to the fence for a 100-yearfrequency event to 6 inches in rural areas. Security criteria includes a maximum 6 gap

between vertical members used if there are no horizontal members are used and a

maximum clear opening that would prevent someone from being able to create a 2 by 2gap in the fence within a 15- minute timeframe if both vertical and horizontal members

are used for the fence. The contractors precipitation calculations were based on NOAA

Atlas 14 Point Precipitation Frequency Estimates at the approximate location of theLukeville POE. Wash crossings were determined from available topography, mapping,

and detailed site visits. Drainage area calculations were based on USGS topology,

although it was not specific on what topology was used. The 100-year peak discharge for

the washes were determined in 2 ways: 1) for sub area greater than 10 square miles,USGS Regression equations for Arizona Region 13 were used, 2) for regions under 10

square miles, the National Resources Conservation Service NRCS method was used. The

hydraulics were performed in two parts, 1) HEC-RAS and Bentleys FlowMasterprogram was used to determine the water surface elevation of the wash prior to the gate

and 2) The head loss equation used was the USACE equation for vertical racks to

determine the increase in the water surface elevation when the flow reaches the gate. Thewater surface elevation results were added to the head loss to achieve a final water

surface elevation. Light Detection and Ranging (LIDAR) contour mapping, aerial

photography and field surveys were used to determine wash characteristics and to modelthe wash crossings. The two boundary conditions used were the 100-year peak flow rate

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determined in the hydrology analysis and normal depth. It was assumed that the gateswould be cleared prior to a flood event and no debris would be capture on the fence

which would create blockage. High Performance Turf Reinforce Mats (HPTRM) was

set downstream of the border fence to prevent scour on locations where the modeledvelocity was greater than 4 fps. The HPTRM is expected to hold up to velocities of 10

fps.

The Final Environmental Assessment (EA) for the proposed installation, operation, and

maintenance of primary pedestrian fence near Lukeville, Arizona February 2008 (Ref. 6)

states that Furthermore, in most washes or arroyos, the primary pedestrian fence would

be designed and constructed to ensure proper conveyance of floodwaters and to eliminatethe potential to cause backwater flooding on either side of the U.S.-Mexico border. CBP

(U.S. Customs and Border Protection) will remove debris from the fence within

washes/arroyos immediately after rain events to ensure that no backwater floodingoccurs.

Site VisitA site visit of the D-2 border fence occurred on September 3, 2008. The site visit

reviewed the fence 1 mile West and 3.1 miles East from the Lukeville Port of Entry.

There had been a storm on August 26th, and the fence had not been maintained since the

storm. It was reported that there was no flooding in the Lukeville POE or Gringo PassStore during the August 26th storms. Three days of radar satellite imagery from NOAA

are shown in Figures 4-6. The W1 border fence location showed large debris captured at

the grate (Fig. 7), sedimentation on the approach to the fence (Fig. 8) and the HPTRMdownstream of the fence was wrapped around the post-and-rail (Fig. 9). Sedimentation

was shown just upstream of the fence (Fig. 10). Standing water was seen justdownstream on the Mexican side of the wash. Large obstructions exist just downstream

on the Mexican side (Fig. 11) W4 had a small amount of debris build up (Fig.12). The

W5 fence crossing had a pool of water at the fence (Fig 13). The fence crossings at W7,W9 and W10 were free of debris. The fence crossing at W11 had a standing pool of

water (Fig 14). The fence crossing at W13 had debris, sedimentation and erosion

downstream of the fence with HPTRM wrapped around the downstream post-and-rail(Fig 15-17).

Due to the reported flooded at the Lukeville POE, the AAR team investigated the

buildings office atrium. The atrium drains the roof and all of the water captured withinthe atrium into three floor drains located within the atrium (Fig 18). The water drains to a

location near fence crossing E1. The end of the drain was reportedly covered at the time

of the July 12th

flood but was daylighted before the site visit. The E1 fence crossing wasclean of debris during the site visit. Crossings E2-E7 were either clean of debris or had a

relatively small amount of debris. The E8 crossing, which has a tributary drainage area of

14.7 sq. mi., collected significant debris and sediment at the crossing (Fig. 19-21). Thesoil was eroded around the downstream post-and-rail foundation (Fig. 22). Erosion was

seen east of the E8 fence crossing, along the upstream toe of the fence (Fig. 23). Debris

was shown at the fence crossing at E9 (Fig 24, 25). The fence crossing at E13, which has

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Figure 4. NOAA Radar Satellite for Aug 26


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Figure 7. W1 crossing.

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Figure 8. Sedimentation in the approach wash for W1

Figure 9. HPTRM wrapped around the downstream post and rail

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Figure 10: W1. Sedimentation just upstream of the fence.

Figure 11. Site W1: Pool downstream of the fence

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Figure 12. Debris at W4

Figure 13. Ponding at the W5 crossing

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Figure 14. W11 fence crossing, upstream side

Figure 15. W13 crossing, upstream side

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Figure 16. W13 crossing

Figure 17 HPTRM rapped around the fence post-and-rail downstream of fence W13

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Figure 18. Center drain at Lukeville POE building atrium

Figure 19. Debris build up at E8

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Figure 20. A closer look at the debris build up at E8

Figure 21. Sedimentation at E8

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Figure 22. Erosion at downstream side of the E8 fence crossing

Figure 23. Erosion at upstream side of the of E8/E9 crossing

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Figure 24.Sediment at E9

Figure 25. Debris at E9

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a tributary drainage area of 0.6 sq. mi., did not have any debris build up (Fig 26). E16,which has a tributary drainage of 14.7 sq. mi., had significant debris and scour

downstream of the fence (Fig. 27-29). Gabbions and K-Rail, presumably used to support

the post and rail, were exposed by the 3-4 foot downstream scour hole. Sedimentationwas evident on the patrol road. Wash crossing E29, which has a drainage of 0.6 sq mi,

had debris build up of tree branches, vegetative material and sedimentation (Fig. 30). Thefence crossing the E30 wash shows significant erosion on its west side on the upstreamside of the fence likely due to lateral flow along the fence (Fig. 31). Debris clogging is

also evident. E31 captured debris at the wash crossing and west along the wire mesh of

the fence (Fig. 32,33)

Analysis

As stated, the July 12th storm accumulated 1.99 in of rain within 90 minutes. This

amount of rain for that short of duration according to NOAA 14 point precipitationfrequency estimates for the Organ Pipe National Monument classifies it between 10-year

and a 25-year storm. The highest volume of recent rainfall for a day is approximately the

2.5 inches which occurred from 0500 26 August to 0500 27 August, Mountain StandardTime (MST). This amount can be substantiated by the gage recording at the Organ Pipe

Cactus Nation Monument rain gage, which preliminary records show 2.62 inches 24 hour

period ending 27 August 2008. NOAA 1- Day Precipitation for 12 July 2008 0500 MST

to 13 July 2008 500 MST are shown in Figure 34. The design for the pedestrian fence isbased on a 100-year, 24-hour frequency storm. The contractor used an adequate data

source to determine 100-year 24-hour storm.

Under the conditions of these two storms, the border fence is shown ineffective to allow

large debris material to pass. Even after the clearing of first flush debris of thewatershed on July 12th, there was still significant amount of debris found on the wash

crossings with large tributary drainage areas from the storm on August 26th. With the

large debris in the fence, sediments and vegetation are less likely to pass through, and inturn, can accumulate with large debris and clog the lower portion of the fence (see figure

19). The obstruction can cause backwater effects, lateral flows along the fence,

flows flowing over the crest of the debris which may cause significant vortex forces atthe downstream footing of fence, which would lead to scour, endangering the structural

integrity of the fence. The backwater can cause sediment and vegetation to settle out of

the flow before the fence. Lateral flows can cause scour along the upstream side of the

fence, and allow flow to pass the fence at another wash location.

The contractor, in the design of the fence, considers the obstruction of the fence in the

wash contributing to head loss of a 100-year storm, however, does not include debriscollected during the storm in their calculation of the rise of the water surface elevation

due to the fence. The design addresses this on page 10 of the Design Complete package

Drainage Report: Kiewit HNTB:

The fence design permits the passage of flows with minimal effects upstream of the

International Boundary resulting from flows backing up behind the fence. This is true

with the assumption that and debris caught on the fence during a storm event will be

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Figure 26. E13 Wash Crossing

Figure 27. Downstream scour at E16 crossing.

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Figure 28. Debris captured at E16

Figure 29. Debris captured at E16

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Figure 30. Debris at Wash E29 Crossing

Figure 31. Erosion east of E30 wash crossing

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Figure 32. Debris at E31

Figure 33. Debris remaining west of E31 crossing

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Figure 34. NOAA observed precipitation on July 12th

rainstorm

cleared by the Border Portal or designated maintenance personnel within a reasonable

timeframe. Debris left in place causing significant blockage of flow area could cause an

eventual backwater rise beyond those calculated in this report. The RFP drainage

report does not explicitly state that debris calculations will be performed or considered

when determining the rise in elevation due to the placement of the fence.

It does not appear that the vegetative material collected at the fence was mulch. There is

no confirmation on the report by the Office of Border Patrol stating the vegetative

material from the construction of the border fence was turned into mulch and depositedwithin the watershed.

The HPTRM showed to be ineffective at the fence crossing W1 and W13. Both are large

washes where respective tributary drainage areas are greater than 1 sq. mi. The HPTRM

was caught in the downstream post-and-rail fence and likely add to the obstruction offlow and backwater effects. It is unknown whether the failure was due to poor installation

or unanticipated flow conditions. There is scour on the downstream side of W13, E8, and

E16.

Scour at the footing on the upstream side of the fence can be seen through inspection at

E8 and E30. Scour at those sites likely incurred due to significant lateral flows. Lateralflows traveled beyond the grate design area and into areas which only contained meshwire, as shown at fence crossing E30 and E31, which indicates the design did not account

for flows within that area (Fig 30, 32).

The OPCNM Report has stated that the flows on July 12 th at fence crossing at W13

reached up to 7 feet from the toe of the fence. According to Contractors report, the 100-

year storm at W13 will reach 4.59 feet above the toe.

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There were some instances of pooling of water in some site west of Lukeville (W1, W5,

W11). The pooling of water can be attributed to a difference in grade between the

downstream Mexican and border fence. It is unknown where this difference existed inthe past and pooling was common in these areas. Requirements by the RFP state that the

contractor will provide details for preventing ponding of water at the fence.

The memo prepared by for Gringo Pass Inc. stated that this years flooding in

the store was worst than last year. It is presumed that the post-and-rail fence was the only

erected obstruction last year. No information is available on the volume and duration of

last years storm. The Gringo Store is close to the fence crossing wash W1, and thepedestrian fence was likely responsible for capturing more debris at the crossing than in

years past. The comparable storm on August 26th did not cause the same flooding in the

in the region. One important change was 120 feet of the east side W1 berm was raised 3feet to protect the store from flooding. The store did not incur flooding on August 26 th. It

is unknown if a 25-year storm alone would have flooded the area in the same manner; the

Gringo Pass Store does lie in the 100-year flood plain, but it is unknown if it lies in a 25-year or 10-year floodplain.

The Lukeville POE flooding on July 12th could have been caused in part by the W1

backwater effects. The blockage of the atrium drain was responsible for the buildingsinternal flooding. The subsequent storm on August 26th did not cause flooding in the

area. It is assumed that the berm as well as the clearance of the drain prevented flooding.

The language in the Final EA states Furthermore, in most washes or arroyos, the

primary pedestrian fence would be designed ad constructed to ensure proper conveyanceof floodwaters and to eliminate the potential to cause backwater flooding on either side of

the U.S.-Mexico border. CBP will remove debris from the fence within washes/arroyos

immediately after rain events to ensure that no backwater flooding occurs. Most of themajor washes here, according to the contractors HEC-RAS simulation, are subcritical

flows, therefore, an increase in height at the fence is propagated upstream. Under the

USIBWC, the fence can increase the water surface elevation at the fence at 3 inches inurban area and 6 inches for rural areas. Conceivably, these 3 and 6 inch criteria may not

cause backwater effects if it does not cause the flow to enter the floodplain. If the flow is

out of the floodplain, then the 3 and 6 inches increase at the fence may increase the

flooding. Therefore, under certain conditions, the 3-6 inch allowable criteria are contraryto the EA criterion of no backwater flooding.

Conclusion

It is unknown whether the fence was a major factor impacting the flooding at the Gringo

Pass Store and the Lukeville POE. Under the conditions of the August 26th

storm theGringo Pass Store did not flood. The three foot rise of the berm on the east side of W1

likely helped prevent the flooding from occurring. The Lukeville POE, with the berm

being raised and the end of the atrium drain being cleared helped the building from beingflooded.

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(b) (6)


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The larger washes, where the tributary drainage area at the fence crossing is greater than

1 sq. mi., showed many instances of debris, sediment and vegetation being captured in

the border fence. The debris at W13 is likely causing an increase in the water surfaceelevation at the fence which is greater than the 100-year elevation. Therefore, the rise in

the water surface elevation is possibly greater than the 6 inches permitted by theUSIBWC design criteria. Another possibility of the unexpected rise of the water surfaceelevation at the fence could be in the discrepancy in the tributary drainage area between

the results from the Contractor and the NPS report. The Contractor estimate of 2,839

acres is 774 acres less than NPS estimate of 3,613 acres. There is not enough data at the

other sites which experienced significant debris blockage to determine if those sites didnot meet the USIBWC criteria.

The contractor did not consider blockage of the debris in calculations of the rise in watersurface elevation from existing to proposed conditions, which, depending on the severity,

can increase the water surface elevation at the location of the fence. Instead the contractor

assumed that any debris would be cleared before the next storm and no debris wouldbuild during the storm. There was no explicit guidance or requirement in the RFP to

consider debris, however, the contractor should have assumed that debris would have

built up against the fence and blocked the small openings available for flow to pass.

The blockage of the fence due to debris is likely adding to downstream scour due to water

flowing over the crest of the blockage and causing significant vortices at the downstream

footing of the fence, dislodging HPTRM and creating scour at the downstream side of thefence. There are instances on the upstream portion of the fence where lateral flows are

causing scour. Erosion is seen in locations where the pedestrian fence does not have thegrate portion, but simply the wire mesh, hence the floodplain cast by the storm is greater

than the expected design 100-year floodplain. The requirements of the RFP states that the

contractor will provide details for protection of scour and/or long term degradation alongwith preventing ponding of water at the fence location, however, the scour and ponding

still occurred, therefore, the contractor seemingly did not meet the design and RFP

requirements.

Given the criteria for both the USIBWC and RFP requirements, it would appear the fence

is not performing as originally intended. Debris will accumulate on the fence given the

tolerances required to keep people out. In addition, continuous maintenance after everyflood event is required to clear debris from the openings.

Recommendations

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(b) (5)


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001078

(b) (5)


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IPT Report

APPENDIX B

Wash Ranking Tables for PF 225

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Project: SBI - TI , Technical IPT

Title: Table B-1: PF 225 washes and data

Date: 4/23/09

Segment CrossingQ

(cfs)

V

(ft/s)

Normal

Depth

(ft)

Flow

Direction (N

/ S)

Bed

Load

Slope

(%)Notes

FEMA

Crossing

Estimated

Construction

Start Date

RANK

A-1 1 7554 34.530 6.61 18.000

Final dranage report not received.

Preliminary Analysis done for two major

wash Zone D 2009 3

A-1 2 7028 35.800 7.86 16.000

Final dranage report not received.

Preliminary Analysis done for two major

wash Zone D 2009 3

A-2A 2 2124 2.870 11.49 S 5.300 Proposed Conditon HEC-RAS Data Zone X 8-Nov-08 2

A-2B 100 0.000 Crossing was not identified Zone X 15-Nov-08 1

A-2C 1+37 13 7.880 0.38 S 13.000 Flow Master Data Zone X 1-Dec-08 2




A-2D 36+35 9 6.770 0.28 S 16.000 Flow Master Data Zone X 16-Dec-08 2






A-2E 5+87 7 4.380 0.38 S 4.000 Flow Master Data Zone X 18-Dec-08 1

A-2E 5+44 95 20.440 0.84 S 37.000 Flow Master Data Zone X 18-Dec-08 2

A-2F 100 7 8.730 1.38 S 50.000 Culvert Data Zone X 8-Nov-08 2A-2G 8 206 1.930 5.41 S 5.000 Proposed Conditon HEC-RAS Data Zone X 10-Dec-08 2

A-2G 2 8 7.850 1.49 N 50.000 Culvert Data Zone X 10-Dec-08 2

A-2G 9 5.40 6.900 1.19 N 50.000 Culvert Data Zone X 10-Dec-08 2

A-2I 0+79 0.78 4.240 0.49 S 9.300 Flow Master Data Zone D 2-Nov-08 1

A-2J 52+67 15.53 8.16 0.58 S 8.040 Flow Master Data Zone D 2-Nov-08 2

A-2J 51+75 174.00 13.17 3.67 N 5.124 Flow Master Data Zone D 2-Nov-08 2


A-2I 40+00 1.52 6.000 0.60 N 15.700 Flow Master Data Zone D 2-Nov-08 2







A-2K J-1 (48+50) 1 1.000 1.00 S 0.700 Drainage Report Zone D 17-Dec-08 1

A-2K J-1&J-2 (47+09) 6300 7.000 6.00 S 1.100 Drainage Report Zone D 17-Dec-08 3



A-2K J-5 (70+50) 6400 8.00 5.50 N 2.600 Drainage Report Zone D 17-Dec-08 3

A-2L J-6 (23+48) 17234 4.000 6.00 N 2.500 Drainage Report Zone D 17-Dec-08 3A-2L J-7 (55+12) 19 1.750 0.10 N 1.200 Drainage Report Zone D 17-Dec-08 1

A-2L J-8 (59+24) 71 1.600 0.20 N 1.700 Drainage Report Zone D 17-Dec-08 1

A-2L J-9 (66+39) 1164 5.270 1.58 N 1.200 Drainage Report Zone D 17-Dec-08 2

A-2N 3 334 7.650 1.35 N 5.100 HEC-RAS Data Zone D 1-Nov-08 2

A-2N 4 96 2.610 0.67 N 10.000 HEC-RAS Data Zone D 1-Nov-08 1

B2 1 50 0.000 Final Drainage Report not Available Zone X not awarded 1







B4 1 0 0.000

H&H was not done in the fi nal drainage

report Zone X 1

B4 2 0 0.000


report Zone X 1

B4 3 0 0.000


report Zone X 1

B4 4 1515 0.000


report Zone A 1

B4 6 270 0.000


report Zone X 1

B4 5 212 0.000


report Zone X 1

B4 7 0 0.000


report Zone X 1

V:\PROJECTS\DHS\112319_PF225 Phase 2\IPT meetings- debris\IPT r eport revised May 2009\Appendix B\Table 1- PF225 washes and data.xls

001080


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Project: SBI - TI , Technical IPT

Title: Table B-1: PF 225 washes and data

Date: 4/23/09

Segment CrossingQ

(cfs)

V

(ft/s)

Normal

Depth

(ft)

Flow

Direction (N

/ S)

Bed

Load

Slope

(%)Notes

FEMA

Crossing

Estimated

Construction

Start Date

RANK

B4 8 0 0.000

H&H was not done in the final drainage

report Zone X 1

B4 9 0 0.000


report Zone X 1

B5A 1 220 0.000 Drainage Report Missing Zone D 1

B5B 1 11 0.000


report (San Dune Area) Zone D 1

B5B 2 5 0.000



B5B 3 1 0.000



C-1 22 21 1.990 0.49 0.500 HEC-RAS Data, All other wash are small Zone X 1

D2 W22 18 9.300 0.83 S 22.000 Flow Master Data Zone X Completed 2








D2 W14 810 5.250 2.72 S 1.100 HEC-RAS Data Zone X Completed 2D2 W13 2605 8.650 4.00 S 1.660 HEC-RAS Data Zone X Completed 3









D2 W4 164 1.380 1.51 S 0.890 HEC-RAS Data Zone X Completed 1



D2 W1 2796 4.960 5.94 S 0.980 HEC-RAS Data Zone A Completed 2

D2 E1 55 2.330 0.78 S 1.000 HEC-RAS Data Zone X Completed 1

D2 E2 12 1.640 0.46 S 2.670 Flow Master Data Zone X Completed 1





D2 E7 6 1.160 0.15 S 0.420 Flow Master Data Zone X Completed 1D2 E8 5875 2.650 6.56 S 0.900 HEC-RAS Data Zone X Completed 2











D2 E19 45 2.530 3.01 S 1.010 HEC-RAS Zone X Completed 2

D2 E20 2335 2.530 3.01 S 1.010 HEC-RAS Zone X Completed 2







D2 E27 2 1.520 0.14 S 3.000 Flow Master Data Zone X Completed 1D2 E28 36 1.730 0.54 S 0.700 Flow Master Data Zone X Completed 1








V:\PROJEC

customs and border protection report on border walls crossing washes and streams

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