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July 7, 2023

International Boundary and Water Commission United States Section Engineering Division El Paso, Texas

Subject: South Bay International Treatment Plant SBIWTP: Assessment and Facility Planning Services San Diego County, California

Following is a narrative of the procedures used to complete this project.

Horizontal Survey Control

The Basis of Horizontal Survey Control for this project is the California Coordinate System, North American Datum of 1983, CCSS83, Zone 6, based locally on Record of Survey 14492 filed in the Office of the San Diego County Recorder on March 31, 1994 as File No. 1994-0214720. The following points from Record of Survey 14492 were used to constrain the project:

Point No.

Horizontal Precision Description Location Northing Easting NAVD88 Elevation Combined Scale Factor Document

Point No.

Horizontal Precision Description Location Northing Easting NVD88 Elevation Combined Scale Factor Document

First Order 2" Iron Pipe with Nail in Monument Well Center intersection Monument Road and Hollister Street 1,778,599.98 6,304,614.92 32.46 1.0000525 Record of Survey No. 14492

Second Order Lead & Brass Tag in Concrete Culvert East side Dairy Mart Road, 160 feet South of Servando Ave.

1,783,140.78 6,311,364.44 43.19 1.0000484 Record of Survey No. 14492

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July 7, 2023

Point No.

Horizontal Precision Description Location Northing

Easting NAVD88 Elevation Combined Scale Factor Document

Point No.

Horizontal Precision Description Location Northing Easting NAVD88 Elevation Combined Scale Factor Document

Point No.

Horizontal Precision Description Location Northing Easting NAVD88 Elevation Combined Scale Factor Document

Second Order 2" Iron Pipe & Brass Tag in Pavement Center Monument Road 400 feet South of Dairy Mart Road 1,778,576.28 6,308,620.81 62.41 1.0000510 Record of Survey No. 14492

Second Order 3 / 4" Iron Pipe & Brass Tag in Pavement Center Dairy Mart Road 0.3 miles North of Monument Road 1,778,802.96 6,311,256.61 41.31 1.0000519 Record of Survey No. 14492

Second Order 3/5" Iron Pipe & No Tag in Dirt 42 feet from border fence 0.55 miles from Southeast Monument Road 1,777,406.09 6,314,129.27 46.58 1.0000525 Record of Survey No. 14492

Vertical Survey Control

The Basis of Vertical Survey Control for this project is the North American Vertical Datum of 1988, NAVD88, based locally on Record of Survey 14492 filed in the Office of the San Diego County Recorder on March 31, 1994 as File No. 1994-0214 720. The following points from Record of Survey 14492 were used to constrain the project:

Point No.

Horizontal Precision Description Location Northing Easting NAVD88 Elevation Combined Scale Factor Document

First Order 2" Iron Pipe with Nail in Monument Well Center intersection Monument Road and Hollister Street 1,778,599.98 6,304,614.92 32.46 1.0000525 Record of Survey No. 1449

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Horizontal and Vertical Survey Control Methods

The Basis of Horizontal and Vertical control for this project is based on Point No. 191. RTK GPS was calibrated to Point No. 191 and then was used to locate and verify the locations of Point No.'s 1450, 1451, 1452 & 1457. This calibration was used to set Project Control within the limits of work Once project Control was set using RTK GPS, points were then checked and verified using conventional survey instruments.

Project Horizontal and Vertical Survey Control

Point No.

Description Location Northing Easting NAVD88 Elevation

Point No.

Description Location Northing Easting NAVD88 Elevation

Point No.

Description Location Northing Easting NAVD88 Elevation

Point No.

Description Location Northing Easting NAVD88 Elevation

Point No.

Description Location Northing Easting NAVD88 Elevation

Scribed "X" in Concrete Tank Northwesterly portion of project.

1,778,435.27 6,310.508.79 59.22

Set Brass Disc in Curb Westerly portion of project.

1,778,226.90 6,310,475.87 56.93

Set Brass Disc in Curb Westerly portion of project.

1,778,120.50 6,310,872.94 59.14

Set Brass Disc in Sidewalk Westerly portion of project.

1,778,109.18 6,311,282.98 54.01

Set Brass Disc in Asphalt Northerly portion of project.

1,778,564.98 6,311,300.88 50.38

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Point No.

Description Location Northing Easting NAVD88 Elevation

Point No.

Description Location Northing Easting NAVD88 Elevation

Boundary Survey

Set Brass Disc in Concrete Gutter Pan Easterly portion of project.

1,777,721.67 6,312,387.45 55.11

Set Brass Disc in 2" Iron Pipe Easterly portion of project.

1,777,697.81 6,310,617.39 82.21

The boundary survey for the project is based upon the survey of adjacent parcels that bound the subject property.

An Assessors Parcel Number or legal description was not available for the subject property as a whole. Following is how the project boundary was determined.

The boundary to the South is the United States of America/State of California - United Mexican States/State of Baja was determined by the field location of Border Monuments No. 255 and No. 256 per Record of Survey 23034.

No. 255

No. 256

I.E.

Northing Easting

Northing Easting

1,778,117.47 6,322,224.75

1,776,617.18 6,306,124.18 s 84°40'35" w -16,170.32'

The boundary to the West was determined using located monuments per Record of Survey 2742, Record of survey 13207 and Record of Survey 16 778. The Document recorded March 12, 1999 as Doc.No. 1999- 0160092 was also used to determine the property line between Project and Assessor's Parcel Number 665-010-41.

The boundary to the Northwest is the Southeasterly right-of-way for Dairy Mart Road and was determined using located monuments per Record of Survey 16778.

The boundary to the Northeast is the Southwesterly right-of-way for Camino De La Plaza and was determined using located monuments per Map 13372, Map 13747 and Record of Survey 12944. Record of Survey 12944 represents points set for the purpose of tying in a levy, based on coordinates provided by the United States IBWC.

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Aerial Topographic Survey

Vertical Mapping Resources performed aerial imagery collection of the project site at a photo scale of 1"=180'. The imagery was collected using a USGS calibrated RC-30 film camera equipped with forward motion compensation. The resulting imagery has stereo coverage at a minimum of 60% forwardlap and 30% sidelap.

Utilizing this imagery and the ground control data supplied by Alyson Consulting, VMR performed analytical aerotriangulation using Hexagon Geospatial's ImageStation Analytical Triangulation (ISAT) software.

Topographic mapping was collected at a scale of 1" = 20' with 0.5' contours. VMR collected all discernible planimetric and topographic features utilizing ImageStation digital photogrammetric workstations. All mapping meets FGDC accuracy requirements for geospatial data.

VMR also performed digital orthorectification services for this project. Control from the aerotriangulation and ground survey was used to tie the digital images to actual ground coordinates.

The DTM collected from the stereo imagery was used during the digital orthorectification process to adjust each image pixel into its correct position. VMR then used an exponential interpolation algorithm to perform the orthorectification processing.

Additional Topo.:raphic and Utility Location Survey

Additional topography was performed. Critical features where field located where elevations and horizontal locations could not be relied upon using the aerial topography. These features included the tops and edges of concrete tanks, building faces, platforms, tops of curbs, edges of sidewalks, utilities, etc. These topographic features were located using conventional survey instruments. Inverts to drainage catch basins, inlets and storm drain manholes were measured and added to the topographic survey. Inverts of sanitary sewer manholes were also measured, where accessible or where flow was manageable. Invert elevations also added to the topographic survey.

Final Submittal

The final submittal for this project will include the following attachments:

• Record of Survey 14492 in .PDF format

• Complete coordinate list of all surveyed points in a .CSV format

• Complete coordinate list of all surveyed points in a .TXT format

• Complete coordinate list of all surveyed points in a printable format

• Aerial topographic survey with color ortho photo attachment in an AutoCAD .DWG format

• Additional topographic survey in an AutoCAD .DWG format

• .PDF copies of all record documents used to solve the properties and street right-of-ways bounding the project

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Cross-Sections of the Facility

Cross Sections at SO-foot intervals were not performed. Instead we used this task to field locate all building corners, top of curbs, edges of concrete sidewalks, concrete pedestals, tops of sewage storage tanks , etc. Our experience has shown that aerial topographic surveys do not accurately define these types of surfaces horizontally and vertically. Performing this task in this way resulted in more actual field locations than Cross Sections and will provide a more realistic picture of the facility. An AutoCAD file is included in our submittal that contains the locations and linework. CSV files are also included which contain the Point Number, Northing, Easting, Elevation and Description of each point.

Utility Locations

All visible utilities were field located using conventional survey methods (Total Station, Data Collector, Reflector Rod). Within the AutoCAD file and CSV files included for the location of the structures, the located utilities are also included. The invert elevations of the sewer and storm drain manholes and catch basins are included within the AutoCAD files.

Section 2.12.L. Section 14. Additional Survey Requirements

The additional survey requirements that are applicable to this project have been addressed in this narrative.

For any questions or comments regarding this project, please do not hesitate to contact me.

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