Attachment 12. B&C Evaluation of IOI Report_200503.pdf

EVALUATION OF THE

INTERNATIONAL OUTFALL INTERCEPTOR

FOR THE CITY OF NOGALES, ARIZONA

EVALUATION OF THE

INTERNATIONAL OUTFALL INTERCEPTOR

FOR THE CITY OF NOGALES, ARIZONA

MARCH 2005MARCH 2005

EVALUATION OF THE INTERNATIONAL OUTFALL

INTERCEPTOR FOR THE CITY OF NOGALES

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...............................................................................................................ES-1

1.0 INTRODUCTION....................................................................................................................1-1

1.1 PURPOSE AND SCOPE OF WORK ........................................................................1-1

1.2 INTERNATIONAL OUTFALL INTERCEPTOR SYSTEM BACKGROUND ....1-1

1.3 BACKGROUND INFORMATION...........................................................................1-2

1.3.1 Past Investigations and Programs ...................................................................1-2

1.3.2 Design Parameters and Capacity Calculations...............................................1-3

2.0 INSPECTION OF INTERNATIONAL OUTFALL INTERCEPTOR .................................2-1

2.1 PRIOR INSPECTION REVIEW................................................................................2-1

2.2 PRE-INSPECTION ACTIVITIES..............................................................................2-1

2.3 MANHOLE INSPECTIONS ......................................................................................2-2

2.4 CLOSED CIRCUIT TELEVISION INSPECTIONS ................................................2-5

2.5 SONAR INSPECTIONS.............................................................................................2-7

2.6 OPERATIONAL DEFECT SUMMARY ..................................................................2-8

2.6.1 Debris...............................................................................................................2-8

2.6.2 Infiltration and Inflow.....................................................................................2-9

2.6.3 Root Intrusion............................................................................................... 2-11

2.7 STRUCTURAL DEFECTS ..................................................................................... 2-11

2.7.1 Corrosion ...................................................................................................... 2-11

2.7.2 Cracks ........................................................................................................... 2-12

2.7.3 Broken Pipe/Holes ....................................................................................... 2-12

2.7.4 Invert Erosion ............................................................................................... 2-13

3.0 INFILTRATION AND INFLOW ...........................................................................................3-1

3.1 HISTORICAL GROUNDWATER DATA ANALYSIS ..........................................3-1

3.2 GROUNDWATER MONITORING TUBE INSTALLATION ...............................3-2

3.3 FLOW METERING ....................................................................................................3-3

3.4 OTHER SOURCES OF DATA ..................................................................................3-3

3.5 RESULTS OF ANALYSIS.........................................................................................3-3 p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\toc.doc\3/24/05\sjw i

TABLE OF CONTENTS (Continued)

4.0 CONDITION ASSESSMENT.................................................................................................4-1

4.1 PIPELINE ASSESSMENT.........................................................................................4-1

4.1.1 IOI Pipeline Deposition ..................................................................................4-1

4.1.2 Corrosion in Concrete Pipes ...........................................................................4-2

4.2 INVERT EROSION IN CONCRETE PIPES ............................................................4-3

4.3 MANHOLE CONDITION ASSESSMENT ..............................................................4-5

4.3.1 Manholes 1-16.................................................................................................4-6

4.3.2 Manholes 17-32...............................................................................................4-6

4.3.3 Manholes 33-99...............................................................................................4-7

4.3.4 Manholes 87 and 96-97B................................................................................4-7

5.0 REHABILITATION RECOMMENDATIONS .....................................................................5-1

5.1 MANHOLE REHABILITATION..............................................................................5-1

5.2 PIPELINE REHABILITATION.................................................................................5-5

5.2.1 Option One – Comprehensive Assessment Program.....................................5-5

5.2.2 Option Two – Rehabilitation or Replacement ...............................................5-6

5.2.3 Recommendations ...........................................................................................5-8

6.0 OPERATION AND MAINTENANCE (O&M).....................................................................6-1

6.1 OPERATION AND MAINTENANCE COST..........................................................6-2

LIST OF TABLES

TABLE ES-1 MANHOLE REHABILITATION COSTS.............................................................ES-2 TABLE ES-2 SUMMARY OF SEWER REPLACEMENT AND ...............................................ES-3

REHABILITATION COSTS

TABLE ES-3 INITIAL DEBRIS AND BLOCKAGE REMOVAL COSTS................................ES-3 TABLE 2-1 SUMMARY OF INCOMPLETE CCTV PIPE SEGMENTS...................................2-5 TABLE 2-2 SUMMARY OF LATERAL CONNECTIONS ........................................................2-6 TABLE 2-3 TOTAL FOOTAGE INSPECTED BY SONAR .......................................................2-8 TABLE 2-4 REACHES WITH DEBRIS........................................................................................2-9 TABLE 2-5 REACHES WITH INFILTRATION AND INFLOW............................................ 2-10 TABLE 2-6 REACHES WITH ROOT INTRUSION ................................................................. 2-11 TABLE 2-7 REACHES WITH CORROSION DEFECTS......................................................... 2-12 TABLE 2-8 REACHES WITH CRACKS PRESENT ................................................................ 2-12 TABLE 2-9 REACHES WITH BROKEN PIPE/HOLES........................................................... 2-13 TABLE 3-1 SUMMARY OF ESTIMATED FLOW AT INFLOW AND....................................3-4

INFILTRATION LOCATIONS

TABLE 3-2 AVERAGE FLOW MONITORING ANALYSIS DURING....................................3-6 p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\toc.doc\3/24/05\sjw ii

SEPTEMBER, OCTOBER AND NOVEMBER 2004

TABLE 4-1 SUMMARY OF NUMBER OF MANHOLES PER CONDITION.........................4-6 TABLE 5-1 MANHOLE REHABILITATION SUMMARY .......................................................5-2 TABLE 5-2 MANHOLE REHABILITATION COSTS................................................................5-4 TABLE 5-3 SUMMARY OF SEWER REPLACEMENT AND .................................................5-9

REHABILITATION COSTS

TABLE 6-1 INITIAL DEBRIS AND BLOCKAGE REMOVAL COSTS...................................6-3 TABLE 6-2 SUMMARY OF OPERATION AND MAINTENANCE COSTS ..........................6-3

THROUGH YEAR 2010

LIST OF FIGURES

FIGURE 1.1 VICINITY MAP.................................................................................. Follows Page 1-1 FIGURE 1.2 LOCATION MAP ............................................................................... Follows Page 1-2 FIGURE 3.1 GROUNDWATER SITE INVENTORY...................................................................3-1

HISTORICAL GROUNDWATER ELEVATION VERSUS TOP OF PIPELINE

FIGURE 3.2 HISTORIC AND MONITORED GROUNDWATER LOCATIONS .....................3-2

FIGURE 3.3 PRIMARY INFILTRATION AND INFLOW LOCATIONS ..................................3-5 FIGURE 4.1 SUMMARY OF OPERATIONAL DEFECTS.................................. Follows Page 4-1 FIGURE 4.2 SUMMARY OF STRUCTURAL DEFECTS ................................... Follows Page 4-1 FIGURE 4.3 SEWER CORROSION CYCLE.................................................................................4-2 FIGURE 4.4 SINGLE ELLIPTICAL CAGE...................................................................................4-4 FIGURE 4.5 DOUBLE CIRCULAR CAGE ...................................................................................4-4

LIST OF PHOTOS

PHOTO 2-1 INFLOW WITHIN MANHOLES IN THE NOGALES WASH..............................2-3

(TYPICAL CONDITION OF MANHOLES 16 THROUGH 33)

PHOTO 2-2 DETERIORATED CAST IRON STEPS WITH VISIBLE DEBRIS,......................2-3

VERIFYING SURCHARGING EVENTS (TYPICAL CONDITION

OF MANHOLES 33, 39, 41-43, 59, 60, 65-69, 71, 72, 81 AND 83-91)

PHOTO 2-3 NO ACCESS TO IOI AT NEW MANHOLE LOCATIONS ...................................2-4

(TYPICAL CONDITION OF MANHOLES 44A-1, 44A, 44B AND 44C)

PHOTO 2-4 CONSTRUCTION DEBRIS IN FLOW PATH (MANHOLE 48) ...........................2-4 PHOTO 2-5 MISSING RING AND FRAME (MANHOLE 51) ...................................................2-4 PHOTO 2-6 INFILTRATION AROUND DEFECTIVE LATERALS .........................................2-4

(TYPICAL CONDITION OF MANHOLES 22, 23 AND 60)

PHOTO 2-7 SAND BAGS AND HEAVY EXPOSED AGGREGATE WITH............................2-4 p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\toc.doc\3/24/05\sjw iii

1/4 INCH PENETRATION (MANHOLES 96)

PHOTO 2-8 EXPOSED AGGREGATE AND SURCHARGED MANHOLES ..........................2-4

(TYPICAL CONDITION OF MANHOLE 96 TO NIWTP)

PHOTO 2-9 EXPOSED AGGREGATE .........................................................................................2-6 PHOTO 2-10 EXPOSED REBAR.....................................................................................................2-6 PHOTO 2-11 ROOT INTRUSION....................................................................................................2-6 PHOTO 2-12 CRACKS......................................................................................................................2-6 PHOTO 2-13 INFILTRATION AND INFLOW...............................................................................2-7 PHOTO 2-14 HOLES.........................................................................................................................2-7 PHOTO 2-15 INVERT EROSION ....................................................................................................2-8 PHOTO 2-16 CORROSION - DEPOSITION...................................................................................2-8

PHOTO 4-1 INVERT EROSION CREATED BY HIGH VELOCITY AND GRIT/SAND .......4-3

PHOTO 4-2 TYPICAL MANHOLE WITHIN NOGALES WASH .............................................4-5 PHOTO 4-3 I/I AROUND LATERAL............................................................................................4-6

APPENDICES

APPENDIX A CALCULATED AS BUILT CAPACITY

APPENDIX B PIPE SHOP DRAWINGS AND STANDARD MANHOLE DETAILS OF

THE ORIGINAL MANHOLES

APPENDIX C MANHOLE INSPECTION SUMMARY TABLE

APPENDIX D DETAILED SUMMARY OF CLOSED CIRCUIT TELEVISION AND

SONAR INVESTIGATIONS

APPENDIX E AVERAGE AND MINIMUM DAILY DRY AND WET WEATHER

FLOW

APPENDIX F REHABILITATED/REPLACED INNER PIPE DIAMETERS AND

CAPACITIES

APPENDIX G PRELIMINARY CONSTRUCTION COST ESTIMATE

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EVALUATION OF THE INTERNATIONAL OUTFALL INTERCEPTOR

FOR THE CITY OF NOGALES

EXECUTIVE SUMMARY

The purpose of this project was to inspect and evaluate approximately 46,600 linear feet of the International Outfall Interceptor (IOI), assess the condition, and develop rehabilitation and/or replacement recommendations. The investigation of the IOI included a comprehensive evaluation using a combination of inspection technologies including manhole assessments, CCTV, sonar, and flow metering.

The results of the investigation identified that the unlined concrete pipe has very little corrosion above the flow line with the exception of the area immediately upstream of the Nogales International Wastewater Treatment Plant and at the discharge of the Rio Rico force main.

However, the invert of the pipeline is experiencing extensive erosion which has compromised the structural integrity of the pipeline.

The recommended rehabilitation and maintenance for the IOI include:

• Manhole rehabilitation to repair structural damage, eliminate inflow and infiltration, and establish pipeline access.

• Pipeline rehabilitation to repair structural damage and eliminate infiltration.

• System maintenance to remove debris and maintain system operation.

A summary of the recommendations is provided in Tables ES-1, ES-2 and ES-3.

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TABLE ES-1

MANHOLE REHABILITATION COSTS

PRIORITY

MANHOLE

NUMBER REHABILITATION RECOMMENDATION

TOTAL COST

(rounded to $500)

A 87 Rehabilitate manhole $ 13,500 A 96 Rehabilitate manhole $ 14,000 A 97 Rehabilitate manhole $ 14,000 A 97A Rehabilitate manhole $ 14,000 A 97B Rehabilitate manhole $ 14,000 B 17 Rehab manhole, adjust and seal flood control riser $ 7,500 B 18 Rehab manhole, adjust and seal flood control riser $ 8,500 B 19 Rehab manhole, adjust and seal flood control riser $ 8,000 B 20 Rehab manhole, adjust and seal flood control riser $ 8,500 B 21 Rehab manhole, adjust and seal flood control riser $ 8,000 B 22 Rehab manhole, adjust and seal flood control riser. Spot repair lateral $ 8,500 B 23 Rehab manhole, adjust and seal flood control riser. Spot repair lateral $ 9,000 B 24 Rehab manhole, adjust and seal flood control riser $ 8,500 B 25 Rehab manhole, adjust and seal flood control riser $ 9,500 B 26 Rehab manhole, adjust and seal flood control riser $ 11,500 B 27 Rehab manhole, adjust and seal flood control riser $ 11,500 B 28 Rehab manhole, adjust and seal flood control riser $ 8,000 B 29 Rehab manhole, adjust and seal flood control riser $ 7,500 B 30 Rehab manhole, adjust and seal flood control riser $ 7,000 B 31 Rehab manhole, provide missing flood control riser, provide access $ 6,500 B 32 Rehab manhole, adjust and seal flood control riser $ 6,500 B 51 Provide frame and raise manhole to grade $ 1,000 B 45 Seal defective tap $ 500 B 47 Seal defective tap $ 500 B 60 Seal defective tap $ 500 B 73 Seal defective tap $ 500 C 33A Buried manhole needs to be raised to grade (patch a/c paving) $ 1,500 C 33B Buried manhole needs to be raised to grade (patch a/c paving) $ 1,500 C 34 Raise manhole to grade ( patch a/c paving) $ 1,500 C 35 Raise manhole to grade ( patch a/c paving) $ 1,500 C 36 Raise manhole to grade ( patch a/c paving) $ 1,500 C 40 Raise manhole to grade ( patch a/c paving) $ 1,500 C 50 Buried manhole needs to be raised to grade $ 1,000 C 52-B Buried manhole needs to be raised to grade $ 1,000 C 53 Buried manhole needs to be raised to grade $ 1,000 C 94 Raise manhole to grade $ 1,000 D 44A Provide access to IOI by removing crown $ 1,000 D 44A1 Provide access to IOI by removing crown $ 1,000 D 44 B Provide access to IOI by removing crown $ 1,000 D 44 C Provide access to IOI by removing crown $ 1,000

TOTAL $ 224,000

The costs include:

• $50/square foot for the application of lining, labor and materials and includes the following:

Mobilization/demobilization for each manhole All necessary labor, equipment, materials, overheads, and profit Taxes, insurance, bonds, other indirect costs Preparatory work – this includes the power wash and/or sandblast of the manhole Confined space considerations.

• Grout injection for Manholes 17-32 at an average cost of $1,000.

• $50/manhour to cover labor efforts, equipment, and general conditions

• $4.50/square foot A/C paving p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\executive summary.doc\3/24/2005\sjw ES-2

TABLE ES-2

SUMMARY OF SEWER REPLACEMENT AND REHABILITATION COSTS

PROJECT

NO. LOCATION

TOTAL

LENGTH

(feet)

MINIMUM

PIPE

DIAMETER

(in)

MAXIMUM

PIPE

DIAMETER

(in)

CONSTRUCTION

COST

A1 Near NIWTP, between Manhole 97A and Manhole 99

1,200 42 42 $ 1,086,000

Subtotal 1,200 $ 1,086,000 B1 Open Floodway, between Manhole 16 and

Manhole 33 5,600 30 30 $ 2,592,000

B2 Old Tucson Highway, between Manhole 60 and Manhole 65

2,500 30 30 $ 1,171,000

B3 Nogales Wash, between Manhole 85 and Manhole 96

7,600 30 36 $ 3,648,000

Subtotal 15,700 $ 7,411,000 C1 Outside of Open Floodway, between

Manhole 33 and Manhole 60 13,800 30 30 $ 6,197,000

C2 Old Tucson Highway, between Manhole 69 and Manhole 85

9,100 30 30 $ 4,074,000

Subtotal 22,900 $ 10,271,000 D1 Beneath Covered Floodway, between

Manhole 1 and Manhole 16 4,700 24 30 $ 1,956,000

Subtotal 4,700 $ 1,956,000

TOTAL 44,500 $ 20,724,000

TABLE ES-3

INITIAL DEBRIS AND BLOCKAGE REMOVAL COSTS

UPSTREAM

DOWNSTREAM

MANHOLE

LINEAR

FEET MANHOURS

BASE

COST

CONTINGENCY

(25 percent)

TOTAL

COST

(rounded to $500)

94 96 2,195 $32,925 $8,231 $ 41,500 97B 99 1,050 $15,750 $3,938 $ 20,000 48 N/A 3 $ 150 $ 38 $ 500 96 N/A 8 $ 400 $ 100 $ 500

TOTAL $ 62,500

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1.0 INTRODUCTION

1.1 PURPOSE AND SCOPE OF WORK

The purpose of this project is to inspect and evaluate approximately 46,600 linear feet of the International Outfall Interceptor (IOI), assess the condition, and develop rehabilitation and/or replacement recommendations.

The primary work elements of this project include:

• Collecting and reviewing of past assessments, relevant documentation and records.

• Performing flow monitoring to identify the primary locations of infiltration and inflow (I/I).

• Determining groundwater elevations along the IOI by means of pitot tube installations within manholes and historical groundwater level data from permanent monitoring wells.

• Providing manhole inspections to provide visual identification of infiltration, defects, and the condition of each manhole.

• Inspecting the IOI through closed circuit television (CCTV) and sonar.

• Performing a detailed condition assessment.

• Developing rehabilitation and/or replacement recommendations and associated costs to correct problems in the IOI.

• Summarizing operation and maintenance requirements and providing associated costs.

1.2 INTERNATIONAL OUTFALL INTERCEPTOR SYSTEM BACKGROUND

The City of Nogales is located in the south-central portion of Arizona situated on the United States-Mexico border and has a population of approximately 21,000 as illustrated in Figure 1.1.

The IOI serves the cities of Nogales, Arizona and Nogales, Sonora Mexico and conveys wastewater to the Nogales International Wastewater Treatment Plant (NIWTP). The collection of Nogales, Sonora wastewater in Mexico is concentrated at the Mexican outfall near the Nogales p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\chapter 1.doc\3/24/2005\sjw 1-1

Port of Entry where a parshall flume is located to meter flow. As the IOI continues north to the NIWTP, it collects additional wastewater from the cities of Nogales and Rio Rico, Arizona.

The IOI was constructed between 1970 and 1971 and is comprised of 24- to 42-inch diameter unlined reinforced and unlined unreinforced concrete pipe. The pipe joints are tongue and groove or bell and spigot with a gasket, and the manholes are constructed of brick or precast concrete.

The pipeline between Manhole 1 and Manhole 16 was constructed within the concrete lined tunnel that conveys surface water from Mexico north into the United States. The IOI was constructed directly on top of the concrete tunnel floor and encased in 8 inches of concrete. The other sections of pipeline were installed by conventional open-cut construction. The pipeline alignment generally follows the Nogales Wash and the Union Pacific Railroad, as shown on Figure 1.2.

1.3 BACKGROUND INFORMATION

1.3.1 Past Investigations and Programs

The following documents were obtained from the City of Nogales and the U.S International Boundary and Water Commission and reviewed for information:

1. Nogales International Sanitation Project, Outfall Pipeline, September 1969

2. Construction Report, Nogales International Sanitation Project, Nogales, Arizona, 1969-1972, Pollard Rodgers

3. Soils Investigation, Nogales Outfall Pipeline, Nogales, Arizona, December 5,

4. City of Nogales Comprehensive Infiltration/Inflow Evaluation Report Final, CDM, July 1996

5. City of Nogales Flow Monitoring Study, Brown and Caldwell, January 2004.

The information in these documents assisted in developing an understanding of the construction methods, materials, and flow conditions within the IOI.

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1.3.2 Design Parameters and Capacity Calculations

The Construction Report for Nogales International Sanitation Project contains a vast amount of highly detailed and documented information. This report provided the following design parameters for the IOI:

Design Year 2000 Population Served

Nogales, Sonora 100,000 Nogales, Arizona 50,000 Total 150,000

Average Daily Flow (based on 90 gallons/capita/day including industrial and infiltration)

Nogales, Sonora 9.0 mgd Nogales, Arizona 4.5 mgd Total 13.5 mgd

Maximum Hourly Flow (based on a peaking factor of 150 percent of average daily flow)

Nogales, Sonora 13.5 mgd Nogales, Arizona 6.75 mgd Total 20.25 mgd

Appendix A summarizes the calculated capacities for each segment of the IOI based on the original as-built drawings for the pipeline. The capacities were calculated using Mannings equation with an “n” value of 0.014 to reflect the current condition of the pipeline. The limiting capacity of the pipeline varies but ranges from 12.9 million gallons per day (mgd) near the Mexican border to 19.1 mgd immediately prior to the NIWTP.

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Nogales

Tucson

Phoenix

Site Location

FIGURE 1.1

Vicinity Map

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0 20 Miles

LineLine

INTERNATIONAL OUTFALL

INTERCEPTOR

NOGALES INTERNATIONAL

WASTEWATER TREATMENT PLANT

FIGURE 1.2

Location Map

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0 5,000

Feet

2.0 INSPECTION OF INTERNATIONAL OUTFALL INTERCEPTOR

Typically, pipeline inspection can be conducted using conventional CCTV to identify defects above the flow line. However, the conditions within the IOI included full pipe segments and invert erosion, both of which cannot be investigated using CCTV without diverting flow from the pipe. To limit the overall project cost and public impact, a combination of inspection technologies including manhole assessments, CCTV, and sonar were implemented.

The inspections were conducted systematically starting with CCTV at Manhole 1 and continued downstream until the flow conditions in the pipe would no longer allow CCTV to be used. The diurnal flow variations in the IOI allowed CCTV inspection to be carried out only between the hours of 11:30 p.m. and 5:30 a.m. To maximize efficiency of the field crews, manhole inspections were performed after CCTV inspections were completed each day. After all of the CCTV investigations had been completed, sonar investigations were performed on any pipe segment that did not receive a complete CCTV inspection and additional representative locations where invert erosion or deposition was likely.

2.1 PRIOR INSPECTION REVIEW

In 1996, the Comprehensive Infiltration/Inflow Evaluation project included limited CCTV investigation of the IOI. Field work was conducted between February 12 and March 25, 1996 to identify I/I. However, due to the extensive I/I, it was estimated that 65 percent of the interceptor was running at full pipe under low flow conditions. Due to the high flow, only 2.5 miles of the IOI were inspected and a total of 54 defects were noted.

In the spring of 2003, the City of Nogales inspected approximately 600 linear feet of the IOI between Manholes 51 and 52 with CCTV. During this investigation, the CCTV camera accidentally flipped over and was submerged below the water surface. The relatively clear wastewater made it possible to identify that the invert of the pipe had eroded and, in some locations, the rebar reinforcement was exposed.

2.2 PRE-INSPECTION ACTIVITIES

Prior to performing any manhole or pipeline inspections, a field reconnaissance was performed to locate all manholes associated with the IOI. During the reconnaissance, ten manholes were identified that were added to the IOI after its completion in 1971. These added manholes are referenced throughout the study by a manhole number referenced to the upstream manhole with a subsequent alpha character (i.e. Manhole 44-A would indicate a new manhole downstream of Manhole 44 and upstream of Manhole 45). With exception of Manholes 33A and 33B, which were installed during the original IOI construction, eight manholes were found to be p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\chapter 2.doc\3/24/2005\sjw 2-1 inaccessible. Manholes 33A, 33B, 35, 40, 52B and 53 were buried and Manholes 6A and 31 were welded or bolted shut. Inspections were not performed on these eight manholes.

Specifications were developed to identify the required equipment and inspection techniques to be used for the project during field investigations. The following requirements were included in the specification to ensure quality data:

• Health and Safety Requirements

• Equipment Capabilities

• Inspection Procedures

• Documentation Requirements

• Data Storage

• Defect Coding and Photographs.

Health and Safety Plans for all field work were completed by CCTV/sonar inspection subcontractors. A field work safety plan was generated by Brown and Caldwell and acknowledged by subcontractors performing field inspections. These plans are required for compliance with Federal and State of Arizona requirements.

Quality control was provided by Brown and Caldwell personnel during the CCTV and sonar inspections. Each pipe inspection was supervised during the investigation to provide a “first hand” look at the pipe and to work with the CCTV and sonar operators to ensure adherence to the specifications and techniques. At each feature, defect or change in pipe condition the camera was paused to view the defect and the complete sewer circumference at that location.

Additionally, a photo was taken at each location. The latest National Association of Sewer Service Companies (NASSCO) defect codes were used to record defects identified during CCTV and sonar inspections.

Traffic control was provided by City of Nogales personnel at each location where inspection work involved setup in a street.

2.3 MANHOLE INSPECTIONS

An inspection log was prepared to record the manhole number, materials used in construction, condition of the manhole wall, condition of access steps, condition of manhole invert, potential for I/I, and accessibility. Trained personnel performed confined space entries at every manhole to gather detailed information. Digital photos of each manhole access point, inside condition, and condition of influent and effluent pipes were taken. The photos and inspection log data was submitted to Border Environment Cooperation Commission under separate cover. A total of 103 manholes were inspected.

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The configuration and materials of the manholes varied depending on the location. The standard manhole details for the original manholes are included in Appendix B and summarized as follows:

• Manholes 33 to 99 are concrete with medium or heavy duty standard covers and frames.

• Manholes 17 to 32 are constructed within the Nogales Wash and are made of brick with heavy duty/watertight covers and frames.

• Manholes 13 to 16 consist of medium duty/watertight covers and frames cast directly into the encasement in the Nogales Wash.

• Manholes 1 to 12 consist of medium duty/watertight covers and frames cast directly into the encasement in Nogales Wash and within the enclosed tunnel. A second manhole frame and cover is located at the street level to provide access to the frame and cover within the tunnel.

During manhole inspection, the hydrogen sulfide readings were negligible except for Manhole 96 where there was a reading of 3 parts per million. Observations made during inspections are illustrated in Photo 2-1 through 2-8.

PHOTO 2-2

DETERIORATED CAST IRON STEPS WITH VISIBLE

DEBRIS, VERIFYING SURCHARGING EVENTS

(TYPICAL CONDITION OF MANHOLES 33, 39, 41-43, 59,

60, 65-69, 71, 72, 81 AND 83-91)

PHOTO 2-1

INFLOW WITHIN MANHOLES IN THE NOGALES WASH

(TYPICAL CONDITION OF MANHOLES 16 THROUGH 33)

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PHOTO 2-4

CONSTRUCTION DEBRIS IN FLOW PATH

(MANHOLE 48)

NO ACCESS T

LOCATIONS

MANHOLES

MISSIN

SAND BAGS AND H

WITH 1/4

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PHOTO 2-3

O IOI AT NEW MANHOLE

(TYPICAL CONDITION OF

44A-1, 44A, 44B AND 44C)

PHOTO 2-5

G RING AND FRAME

MANHOLE 51) INFILTRATION A

(TYPICAL CONDITI

EXPOSED AG

MAN

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PHOTO 2-6

ROUND DEFECTIVE LATERALS

ON OF MANHOLES 22, 23 AND 60)

PHOTO 2-8

GREGATE AND SURCHARGED

S (TYPICAL CONDITION OF

HOLES 96 TO NIWTP)

PHOTO 2-7

EAVY EXPOSED AGGREGATE

INCH PENETRATION

MANHOLE 96)

2-4

A summary table including manhole number, manhole condition, comments and lateral summary of all manholes inspected is included in Appendix C.

2.4 CLOSED CIRCUIT TELEVISION INSPECTIONS

CCTV inspections were performed to investigate the existing condition of the IOI and to provide a video record. The CCTV system consisted of a camera and lights mounted on a platform which was floated between manholes. The latest NASSCO defect codes were used to list problems observed by the CCTV operator. Data was collected using the CCTV data acquisition system and stored digitally.

CCTV investigation of the IOI was conducted between September 20 and October 8, 2004. All inspections were performed during the very early morning hours to take advantage of the lowest flow conditions. This maximized the area of pipeline visible during the CCTV investigations, thereby increasing the total footage that could be inspected. The pipe was inspected from the south to north until less than 50 percent of the pipe was visible. CCTV was completed from Manhole 1 through Manhole 96, except for the reaches summarized in Table 2-1.

TABLE 2-1

SUMMARY OF INCOMPLETE CCTV PIPE SEGMENTS

DOWNSTREAM

MANHOLE

LENGTH

(feet) COMMENTS

16 17 362 Manhole 16 is a 5-foot drop manhole 23 24 516 Survey abandoned at 233 feet due to high water level 28 29 499 Survey abandoned at 54 feet due to high water level 64 65 1452 Survey abandoned at 1,004 feet due to high water level 65 66 1454 Survey abandoned at 551 feet due to high water level 75 76 1027 Survey abandoned at 207 feet due to high water level 95 96 1060 Survey abandoned at 776 feet due to high water level

A summary of all lateral connections observed between manholes during the CCTV inspections is provided in Table 2-2. A listing of the lateral connections made at manholes is included in the Manhole Inspection Summary Table provided in Appendix C.

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TABLE 2-2

SUMMARY OF LATERAL CONNECTIONS

DOWNSTREAM

MANHOLE

LATERAL LOCATION

AND POSITION FROM

UPSTREAM MANHOLE COMMENTS

2 3 351.1 feet at 1 o'clock 4-inch diameter 36 37 180 feet at 12 o'clock 4-inch diameter

12.2 feet at 10 o'clock 4-inch diameter

155.50 feet at 12 o'clock 4-inch diameter (capped)

39 40

162.90 feet at 2 o'clock 4-inch diameter 51 52 407.7 feet at 12 o'clock 4-inch diameter 52-A 53 276.70 feet at 12 o'clock 4-inch diameter

The total footage inspected was 41,488 feet, which is 89 percent of the entire IOI which far surpassed the originally expected percentage of 75 percent. Major primary defects identified are illustrated in Photos 2-9 through 2-14.

PHOTO 2-9

EXPOSED AGGREGATE

PHOTO 2-10

EXPOSED REBAR

PHOTO 2-12

CRACKS

PHOTO 2-11

ROOT INTRUSION

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A detailed summary of the CCTV investigations is included in Appendix D.

PHOTO 2-13

INFILTRATION AND INFLOW

PHOTO 2-14

HOLES

2.5 SONAR INSPECTIONS

After the CCTV work was complete, sonar investigations were conducted at locations where CCTV inspection was incomplete (as identified in Table 2-1) or not possible due to high water levels in the pipe. Additional investigations were conducted throughout the system to characterize the presence and extent of invert erosion or solids deposition. Locations were selected based on the overall potential for erosion and deposition including pipeline geometry and velocity.

Sonar technology involves the emission of sound waves through water and the reception of the pulse echo. Similar to CCTV, the camera and sonar equipment are mounted on a platform with lights, lowered into a manhole, and floated downstream to the next manhole.

Sonar investigations were conducted between October 12 and October 21, 2004. All inspections were performed during high flow periods in order to maximize the amount of pipeline visible below the waterline. The completed sonar inspection included 40 pipe segments between Manhole 2 and the NIWTP totaling 19,987 linear feet. The total footage inspected is summarized by pipe size in Table 2-3. A complete listing of the segments investigated and a summary of the sonar investigation results is included in Appendix D.

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TABLE 2-3

TOTAL FOOTAGE INSPECTED BY SONAR

PIPE SIZE (inches) FOOTAGE INSPECTED (feet)

24 1,120 30 15,329 36 2,488 42 1,050

The results of the sonar investigation identified both operational and structural defects. The defects identified in the IOI by sonar included invert erosion, crown corrosion, and deposition as illustrated in Photos 2-15 and 2-16.

PHOTO 2-15

INVERT EROSION

PHOTO 2-16

CORROSION - DEPOSITION

2.6 OPERATIONAL DEFECT SUMMARY

The operational defects found in the IOI included debris, I/I and root intrusion. The occurrences of these defects as identified by the CCTV and Sonar inspections are summarized in the following sections.

2.6.1 Debris

Accumulations of debris can lead to loss of hydraulic capacity and a potential for sewer backups, blockages and overflows. Most of the IOI operates with extremely high velocities due to the grade of the pipeline. In these locations, the velocities typically exceed 5 to 8 feet per second on a daily basis, thus only very large and heavy debris can be deposited. However, between Manholes 94 and 99, the pipeline is flatter and the velocities are reduced. In these reaches, there was substantial deposition. Table 2-4 lists reaches with debris accumulations found during the investigations.

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TABLE 2-4

REACHES WITH DEBRIS

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

OPERATIONAL

DEFECTS COMMENTS

23 24 30 518 10/15/2004 Object/debris at 223.3 feet, water level appears to fluctuate

65 66 30 1,447 10/18/2004 Heavy object identified at 1,434 feet

90 91 30 232 10/13/2004 Object/debris at 134 feet, water level appears to fluctuate

94 95 36 1,166 10/14/2004 Isolated debris identified throughout reach, water level appears to fluctuate

95 96 36 1,029 10/15/2004 Heavy debris identified throughout reach, water level appears to fluctuate

97 98 42 835 10/18/2004 Heavy debris identified throughout reach, surcharged pipe

98 99 42 300 10/19/2004 Heavy debris identified throughout reach, surcharged pipe

2.6.2 Infiltration and Inflow

Excessive I/I reduce the available hydraulic capacity of sewer systems and the ability of the treatment facilities to treat wastewater. Table 2-5 identifies reaches where I/I was observed during CCTV inspections. Sonar inspections will not detect I/I.

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TABLE 2-5

REACHES WITH INFILTRATION AND INFLOW

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

OPERATIONAL

DEFECTS COMMENTS

17 18 30 184 9/30/2004 I/I at Manhole 17 from surface and at Manhole 18 Dome Riser not attached to original manhole allowing groundwater to enter

19 20 30 400 9/30/2004 I/I at Manhole 20 Dome Riser not attached to original manhole allowing groundwater to enter

20 21 30 389 9/30/2004 I/I at joint at 62 feet, 192 feet at Manhole 21

Dome Riser not attached to original manhole allowing groundwater to enter

21 22 30 199 9/30/2004 I/I at joint at 27.5 feet, 111 feet, 165 feet and within Manhole 22

Heavy I/I around 12-inch lateral within Manhole 22;

Dome Riser not attached to original manhole, allowing groundwater to enter

22 23 30 235 9/30/2004 I/I through core drill at 8 feet, heavy I/I at Manhole 23

Heavy I/I around 12-inch lateral within Manhole 23;

Dome Riser not attached to original manhole allowing groundwater to enter

23 24 30 517 9/30/2004 I/I at Manhole 24 Dome Riser not attached to original manhole allowing groundwater to enter

24 25 30 438 9/30/2004 I/I at joint at 31.9 feet Dome Riser not attached to original manhole allowing groundwater to enter

25 26 30 110 9/30/2004 I/I at joint at 47.4 feet and around lateral within Manhole 26

Dome Riser not attached to original manhole allowing groundwater to enter

27 28 30 439 10/1/2004 I/I at joint at 170 feet Dome Riser not attached to original manhole allowing groundwater to enter

64 65 30 1,452 9/24/04, Incomplete

I/I at joints at 424.5 feet,

533.7 feet, heavy I/I at

481.1 feet

65 66 30 1,454 10/1/04 Incomplete

Heavy I/I from hole at 196 feet

66 67 30 305 9/24/2004 I/I at 269.6 feet 67 68 30 415 9/24/2004 I/I at 17.3 feet, 295.2 feet 85 86 30 1,064 10/7/2004 Infiltration from joint at

726 feet

88 89 30 156 10/8/2004 Infiltration from joints at

124.6 feet, 125.6 feet, 139 feet

89 90 30 1,272 10/8/2004 Infiltration from joints at 473 feet, 789 feet, 849.6 feet, 1,264 feet

90 91 30 231 10/7/2004 Infiltration at core drill, at hole, from joint at 227 feet

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2.6.3 Root Intrusion

Root intrusion was found to be only a minor operational concern within the IOI. However, root intrusion does identify potential locations that may provide for I/I through the same path. The locations exhibiting root intrusion are summarized in Table 2-6.

TABLE 2-6

REACHES WITH ROOT INTRUSION

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

OPERATIONAL

DEFECTS COMMENTS

50 51 30 900.37 9/22/2004 Root intrusion at joint at

184.7 feet

55 56 30 247.82 9/24/2004 Root intrusion at joint at

30.5 feet

56 57 30 249.88 9/23/2004 Root intrusion at joint at

205.1 feet

58 59 30 572.82 9/23/2004 Root intrusions at 2 feet,

19.6 feet, 21.9 feet, 23.5 feet, 61.7 feet, 254.6 feet

69 70 30 1,565.91 9/30/2004 Root intrusion at joints at 853 feet, 893.9 feet, 902 feet

75 76 30 1,027.00 10/06/04 Incomplete

Root intrusion at joint at 156 feet

84 85 30 1,296.68 10/6/2004 Root intrusion at

18.1 feet, 79.2 feet,

195.5 feet

94 95 36 1,166.00 10/8/2004 Root intrusion at 180.2 feet, 267.6 feet, 289 feet

2.7 STRUCTURAL DEFECTS

CCTV and sonar inspections revealed a number of localized structural problems in the IOI.

Above the flow line the most predominant structural defects was corrosion and below the flow line was invert erosion.

2.7.1 Corrosion

Evidence of some corrosion was observed in all 97 reaches inspected by CCTV. Minor to heavy exposed aggregate was found to be a continuous defect throughout the IOI with the most severe corrosion being observed by sonar between Manhole 97 and Manhole 98. Table 2-7 identifies the more severe corrosion defects identified during the CCTV investigation.

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TABLE 2-7

REACHES WITH CORROSION DEFECTS

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

CORROSION

DEFECTS COMMENTS

6 7 30 450.00 9/27/04 Exposed and Corroded

Rebar

7 8 24 300.00 9/28/2004 Corroded Rebar 18 19 30 399.79 9/30/2004 Rebar Ripples 19 20 30 400.00 9/30/2004 Exposed Rebar and Rebar

Ripples

57 58 30 254.96 9/23/2004 Exposed Rebar 58 59 30 572.82 9/23/2004 Rebar Ripples 76 77 30 1,016.49 10/6/2004 Rebar Ripples 80 81 30 1,315.28 10/6/2004 Exposed Rebar 81 82 30 275.23 10/6/2004 Exposed Rebar 84 85 30 1,296.68 10/6/2004 Exposed Rebar 85 86 30 1,064.37 10/7/2004 Exposed Rebar and Rebar

Ripples

88 89 30 156.14 10/8/2004 Rebar Ripples 90 91 30 231.00 10/7/2004 Exposed Rebar 92 93 30 238.10 10/7/2004 Exposed Rebar 93 94 30 1,165.74 10/7/2004 Rebar Ripples 94 95 36 1,166.00 10/8/2004 Rebar Ripples

2.7.2 Cracks

Cracks may be the result of poor installation, damage from other construction activities in the vicinity of the pipeline, or external loads. Even though cracks were identified at a number of locations, the pipe appeared to still be structurally sound. Table 2-8 summarizes the cracks observed during CCTV inspection.

TABLE 2-8

REACHES WITH CRACKS PRESENT

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

STRUCTURAL

DEFECTS COMMENTS

4 5 30 450.00 9/28/2004 Crack at joint at 319 feet 5 6 30 450.00 9/27/2004 Crack at joint at 13.6 feet 9 10 24 550.00 9/28/2004 Cracked pipe at 72.6 feet 58 59 30 572.82 9/23/2004 Cracked pipe at 19.6 feet 94 95 36 1,166.00 10/8/2004 Numerous cracked sections from 239 feet to Manhole 95

Pipe is adjacent to railroad and this may be the cause of the cracks throughout the pipe

2.7.3 Broken Pipe/Holes

Holes in the pipe wall may be the result of corrosion, poor installation, abandoned connections, drill holes, or improperly prepared test borings. In areas with high groundwater, these holes can p:\bc - tucson\border environmentcc\26460 - nogales ioi\deliverables\reports\eval ioi\pdf files\final pdf report\chapter 2.doc\3/24/2005\sjw 2-12 also contribute to I/I. Table 2-9 summarizes the locations where holes were observed during CCTV inspections.

TABLE 2-9

REACHES WITH BROKEN PIPE/HOLES

DOWNSTREAM

MANHOLE

DIAMETER

(inches)

PIPE

LENGTH

(feet)

INSPECTION

DATE

STRUCTURAL

DEFECTS COMMENTS

17 18 30 183.43 9/30/2004 Core drill at 7 feet 49 50 30 1,412.32 9/22/2004 Core drill at 11.7 feet 51 52 30 896.59 9/22/2004 Defective lateral break at

407.7 feet, annular space not filled

62 63 30 149.07 9/24/2004 Core drill at 14 feet 65 66 30 1,454.11 10/1/04

Incomplete Hole in pipe at joint at 196 feet

89 90 30 1,271.71 10/8/2004 Possible hole at 535 feet appears to be broken joint

90 91 30 231.00 10/7/2004 Defective core drill at 14 feet, hole with roots at 20 feet

2.7.4 Invert Erosion

Sonar inspections were performed on representative areas of the IOI to categorize the various conditions within the IOI. These areas were chosen based on slope, diameter and location. The investigation identified that 0.5 to 1.5 inches of invert erosion is present throughout most of the IOI with the exception of Manholes 96 to 99 where deposition is occurring. Based on this representative sample, it is reasonable to expect that all of the pipe segments between Manhole 1 and Manhole 96 are experiencing invert erosion due to high velocities and the associated high volume of debris in the pipeline.

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3.0 INFILTRATION AND INFLOW

I/I can be a major issue contributing to operational failures within a collection system. I/I is created by either inflow of surface water or infiltration of groundwater. Substantial quantities of I/I can overload treatment plants and pipeline capacities. In the most severe cases, permit violations can occur due to the discharge of treated wastewater that does not meet regulatory permit requirements or sanitary sewer overflows.

Historical groundwater data collection, sewer flow metering, and groundwater monitoring were conducted in addition to the CCTV and manhole inspections to identify the primary areas where I/I is occurring. The purpose of this analysis was not to quantify the amount of flow but to gain a general understanding of where I/I is occurring.

3.1 HISTORICAL GROUNDWATER DATA ANALYSIS

The Ground Water Site Inventory database is maintained by the Arizona Department of Water Resources (ADWR) and includes statewide groundwater and well data. The data is used to conduct investigations regarding Arizona’s water supply and consists of field data collected, verified and maintained by ADWR’s Basic Data Unit or the U.S. Geological Survey.

Ninety-one well sites were found in the database that could be used to estimate groundwater elevations in the general vicinity of the IOI alignment. The water elevations were single point elevations for each well site between the years of 1994 and 2004. To identify areas with high I/I potential, the groundwater elevations were compared to the top of pipe elevation based on IOI as-built drawings. Figure 3.1 illustrates the approximate groundwater elevation (shown in blue) versus the top of pipe.

3450.00

3500.00

3550.00

3600.00

3650.00

3700.00

3750.00

3800.00

3850.00

0.00 5000.00 10000.00 15000.00 20000.00 25000.00 30000.00 35000.00 40000.00 45000.00 50000.00

Station (ft)

El ev at io n (ft

Top of Pipe Elev. (ft.)

Estimated Historical Groundwater Elevation

MH 17

MH 33

MH 40

MH 48

MH 64

MH 68

MH 77

MH 81

MH 94

MH 99

MH 85

MH 1

MH 10

MH 23

MH 29

MH 37

MH 44

MH 52

MH 56

MH 73

MH 89

FIGURE 3.1

GROUNDWATER SITE INVENTORY

HISTORICAL GROUNDWATER ELEVATION VERSUS TOP OF PIPELINE

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In addition, the construction report from the IOI installation also provided several locations where groundwater was encountered during construction. Those reaches included Manholes 16 to 33, 60 to 68, and 84 to 96.

3.2 GROUNDWATER MONITORING TUBE INSTALLATION

During manhole inspections, man entries were conducted to install groundwater monitoring tubes. A 3/4-inch diameter hole was drilled through the manhole wall and into the surrounding earth immediately above the manhole base. A 1/2-inch clear tubing was installed through the opening and extended to a point just below the top of the manhole. The tubes were monitored to identify the presence of groundwater periodically during the IOI investigation between September and November 2004.

Tubes were not installed between Manholes 1 and 16 as these manholes are encased in concrete and are above the ground surface. In addition, tubes were not installed in Manholes 17 to 32 since it was noted during the manhole inspections (see Table 2-5) that substantial infiltration was occurring which indicated that groundwater was present.

Of the manholes monitored, nine locations were identified to have groundwater during the investigation period and are shown in red font on Figure 3.2. As illustrated, the location where groundwater was detected in the monitoring tube and the historical groundwater investigation correlate exceptionally well.

3450.00

3500.00

3550.00

3600.00

3650.00

3700.00

3750.00

3800.00

3850.00

0.00 5000.00 10000.00 15000.00 20000.00 25000.00 30000.00 35000.00 40000.00 45000.00 50000.00

Station (ft)

El ev at io n (f t)

Top of Pipe Elev. (ft.)

Estimated Historical Groundw ater Elevation

MH 17

MH 33

MH 40

MH 48

MH 64

MH 68

MH 77

MH 81

MH 94

MH 99

MH 85

MH 1

MH 10

MH 23

MH 29

MH 37

MH 44

MH 52

MH 56

MH 73

MH 89

MH 47

MH 60, 61

MH 66

MH 80

MH 90, 91, 92, 93

FIGURE 3.2

HISTORIC AND MONITORED GROUNDWATER LOCATIONS

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3.3 FLOW METERING

Flow metering was performed to assist in identifying primary locations of dry and wet weather I/I. Flow meters coupled with area/velocity sensors were installed at five locations approximately 1 mile apart along the IOI between September 16 and November 23, 2004. The flow meter locations included Manholes 36, 48, 56, 84 and 90. Additional data was collected at Manhole 15 using a flow meter previously installed (prior to September 16, 2004).

American Sigma 910 Flow Meters coupled with Submerged Area/Velocity Sensors were used to measure and record flow data. The Submerged Area/Velocity Sensor measures the water surface level in conjunction with the Doppler method of velocity measurement to calculate flow. The small sensor, containing a pressure transducer and a velocity sensor, was placed into the flow stream at the invert of the influent pipe.