Exhibit1_Rprt_Alts_Analysis_SAR_Marsh_Tide_Gate.pdf

FINAL REPORT

Produced For Orange County Public Works (OCPW) June 29, 2022

SANTA ANA RIVER MARSH TIDE

GATE

Rehabilitation / Replacement Alternatives Analysis

Tide Gate Rehabilitation / Replacement Alternatives Analysis | OCPW i

Document Verification

Revision Description Issued by Date Checked

00 Draft Report BWC 1/14/22 JCS 1/14/22, MEB 1/17/22

01 Final Report BWC 6/3/22 JCS 6/7/22

Produced by:

Moffatt & Nichol 555 Anton Blvd., Ste. 400 Costa Mesa, CA 92626

(657) 261-2699 www.moffattnichol.com

Client Orange County Public Works

Project name Santa Ana River Marsh Tide Gate

Document title Report

Document sub-title Rehabilitation / Replacement Alternatives Analysis

Status Final Report

Date June 29, 2022

M&N project number 10065-13 ii

Table of Contents Executive Summary ....................................................................................................................................................................... vi

1. Introduction

1.1. Project Site Overview

1.2. Site Hydraulic Conditions

2. Tide Gate Inspection

2.1. Inspection Procedures

2.2. Description Of Structures

2.2.2. Existing Gate Cycle of Operations

2.3. Inspection Results

2.3.1. Tide Gates

2.3.2. Tide Gate Support and Culverts

2.3.3. Trash Rack Condition

3. Remaining Service Life

4. Engineering Assessment: Option 1 Repair and Maintain Existing Tide Gates

4.1. Proposed Service Life Extension Repair Options

4.1.1. Gate Repairs

4.1.2. Culvert Repairs

4.1.3. Trash Rack Repairs

4.1.4. Stoplog Upgrade

4.2. Coatings

4.2.2. Steel Repairs

4.2.3. Environmental Requirements

4.3. Existing Gate Removal

4.3.1. On-Site Laydown Area

4.3.2. Additional Logistics

5. Engineering Assessment: Option 2, Tide Gate Replacement

5.1. Tide Gate Configurations

5.1.1. Level Control Gate

5.1.2. SRT Top-Hinge Gates

5.1.3. SRT Side-Hinge Gates

5.2. Tide Gate Regulator Location

5.2.1. SRT Seaward Side Regulator

5.2.2. SRT Landward Side Regulator

5.3. New Gate Footprint Requirements

5.3.1. Tide Gate Footprint Requirements

5.3.2. Regulator Footprint Requirements

5.4. Tide Gate Adjustability

5.5. Tide Gate Materials

5.5.1. New Level Control Gate Materials

5.5.2. SRT Gate Materials

5.5.3. A690 Mariner Steel

5.5.4. Corrosion

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5.6. Tide Gate Foundations

5.6.1. Level Control Gate Foundation Modifications

5.6.2. Top or Side Hinged Gate Foundation Modifications

6. Cost Estimates

6.1. Repair Option #1 (In-Situ Repair)

6.2. Repair Option #2 (Onsite Repair)

6.3. Repair Option #3 (Offsite Repair)

6.4. Tide Gate Replacement Option (In Kind, Mild Steel)

6.5. Tide Gate Replacement Option (In Kind, Stainless Steel)

6.6. Tide Gate Replacement Option (Alternate Style)

Appendix I: South Gate UT Measurements Appendix II: Epoxy Coating Manufacture Data Sheets Appendix III: Tide Gate Layout, Waterman, and Nehalem Marine Appendix IV: Tide Gate Sequence of Operations Appendix V: Detailed Cost Estimates

List of Figures Figure 1: Area Map of Project Site (Google earth) Figure 2: Project Site Map (Google Earth) Figure 3: Existing Tide Gate Elevation Figure 4: Existing Box Culvert Partial Typical Section Figure 5: Example of Surface Mounted Stoplog System (image courtesy Waterman) Figure 6: Existing Tide Gate, Major Components Figure 7: Nominal Design Weights, Existing Tide Gate

List of Tables Table ES-1: AACE Class 4 Cost Estimates w/ 20% Contingency (2022 Dollars) .................................................................. vi Table 1: Original (1987) Design Conditions of Tide Gates Table 2: Tidal Datums for Specified Tidal Epochs for NOAA CO-OPS 9410580 Table 3: Condition Assessment Ratings (Excerpt of Table 2-14 from ASCE no. 130) Table 4: Description of Cleaning Standards, Excerpts from SSPC Standards Table 5: AACE Class 4 Cost Estimates

Appendices Appendix I: South Gate UT Measurements Appendix II: Epoxy Coating Manufacture Data Sheets Appendix III: Tide Gate Layout, Waterman, and Nehalem Marine Appendix IV: Tide Gate Sequence of Operations Appendix V: Detailed Cost Estimates iv

Disclaimer Moffatt & Nichol devoted effort consistent with (i) the level of diligence ordinarily exercised by competent professionals practicing in the area under the same or similar circumstances, and (ii) the time and budget available for its work, to ensure that the data contained in this report is accurate as of the date of its preparation. This study is based on estimates, assumptions and other information developed by Moffatt & Nichol from its independent research effort, general knowledge of the industry, and information provided by and consultations with the client and the client's representatives. No responsibility is assumed for inaccuracies in reporting by the Client, the Client's agents and representatives, or any third-party data source used in preparing or presenting this study. Moffatt & Nichol assumes no duty to update the information contained herein unless it is separately retained to do so pursuant to a written agreement signed by Moffatt & Nichol and the Client.

Moffatt & Nichol’s findings represent its professional judgment. Neither Moffatt & Nichol nor its respective affiliates, makes any warranty, expressed or implied, with respect to any information or methods disclosed in this document. Any recipient of this document other than the Client, by their acceptance or use of this document, releases Moffatt & Nichol and its affiliates from any liability for direct, indirect, consequential, or special loss or damage whether arising in contract, warranty (express or implied), tort or otherwise, and irrespective of fault, negligence, and strict liability.

This report may not to be used in conjunction with any public or private offering of securities, debt, equity, or other similar purpose where it may be relied upon to any degree by any person other than the Client.

This study may not be used for purposes other than those for which it was prepared or for which prior written consent has been obtained from Moffatt & Nichol.

Possession of this study does not carry with it the right of publication or the right to use the name of "Moffatt & Nichol" in any manner without the prior written consent of Moffatt & Nichol. No party may abstract, excerpt, or summarize this report without the prior written consent of Moffatt & Nichol. Moffatt & Nichol has served solely in the capacity of consultant and has not rendered any expert opinions in connection with the subject matter hereof. Any changes made to the study, or any use of the study not specifically identified in the agreement between the Client and Moffatt & Nichol or otherwise expressly approved in writing by Moffatt & Nichol, shall be at the sole risk of the party making such changes or adopting such use.

This document was prepared solely for the use by the Client. No party may rely on this report except the Client, or a party so authorized by Moffatt & Nichol in writing (including, without limitation, in the form of a reliance letter). Any party who is entitled to rely on this document may do so only on the document in its entirety and not on any excerpt or summary. Entitlement to rely upon this document is conditioned upon the entitled party accepting full responsibility and not holding Moffatt & Nichol liable in any way for any impacts on the forecasts or the earnings from the project resulting from changes in "external" factors such as changes in government policy, in the pricing of commodities and materials, price levels generally, competitive alternatives to the project, the behavior of consumers or competitors and changes in the owners’ policies affecting the operation of their projects.

This document may include “forward-looking statements.” These statements relate to Moffatt & Nichol’s expectations, beliefs, intentions, or strategies regarding the future. These statements may be identified by the use of words like “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “plan,” “project,” “will,” “should,” “seek,” and similar expressions. The forward-looking statements reflect Moffatt & Nichol’s views and assumptions with respect to future events as of the date of this study and are subject to future economic conditions, and other risks and uncertainties. Actual and future results and trends could differ materially from those set forth in such statements due to various factors, including, without limitation, those discussed in this study. These factors are beyond Moffatt & Nichol’s ability to control or predict. Accordingly, Moffatt & Nichol makes no warranty or representation that any of the projected values or results contained in this study will actually be achieved.

This study is qualified in its entirety by, and should be considered in light of, these limitations, conditions, and considerations.

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Glossary AACE Association for the Advancement of Cost Engineering BMP Best Management Practice CCC California Coastal Commission CDFW California Department of Fish and Wildlife CEQA California Environmental Quality Act CL- Chloride ions CSE Confined space entry ft Feet

in. Inch M&N Moffatt & Nichol MHHW Mean higher-high water MHW Mean high water Mil One thousandth of an inch (0.001-in.)

MLLW Mean lower-low water MLW Mean low water MSL Mean sea level MTL Mean tide level NaCl Salt NAVD88 North American Vertical Datum of 1988 OCPW Orange County Department of Public Works OPC California Ocean Protection Council redox Reduction/oxidation SAA Streambed Alteration Agreement SAR Santa Ana River SARWQB Santa Ana Regional Water Quality Board SCAQMD South Coast Air Quality Management District SLR Sea level rise SRT Self-regulating tide (gates) SSPC Society for Protective Coatings STND Station Datum USACE U.S. Army Corps of Engineers USFWS U.S. Fish and Wildlife Services UT Ultrasonic thickness UV Ultraviolet VOC Volatile organic compound WDR Water discharge requirement WOUS Waters of The United States vi

Executive Summary Moffatt & Nichol (M&N) was selected in May 2021 by the Orange County Department of Public Works (OCPW) to develop an alternatives analysis for two tide gates and their accompanying culvert structures located on the southern bank of the Santa Ana River (SAR) in Huntington Beach, CA. In support of this analysis, M&N performed structural inspections on June 1 and October 28, 2021, to assess the condition of the tide gates and accompanying culverts.

Overall, both the north and south tide gates are in similar Fair condition, with isolated elements in Poor condition. The north gate is in slightly better condition with less extensive corrosion than the south. This is most likely due to the higher invert elevation of the north gate, and it being situated approximately 1 mile farther upstream, reducing its saltwater contact. The cast-in-place concrete forming the culvert and tide gate support is typically sound and in Satisfactory condition. The concrete is free of significant cracking, spalling, or other evidence of distress.

The trash racks are in Serious to Critical condition. At the time of inspection, all the trash racks were clogged with debris and there was significant damage to the concrete foundation and steel gratings. The identified damage includes buckling of the steel gratings, displacement of the steel gratings, and pull-out failure of the embedded concrete anchors.

The observable condition of the tide gates is commensurate with their age and the environment to which they are exposed. None of the defects identified warrant emergency action; however, to extend their service life for an additional 10 years, a prioritized repair and maintenance program is considered prudent.

M&N examined three repair options. These repair options primarily differ in the location of where the repairs are to be performed. Options for repairing the gates in-situ, onsite, and offsite were considered. The repairs proposed for the gates include cleaning, patching, and recoating the gate steel with a modern epoxy coating. Additional repairs and modifications to the trash racks and concrete culverts are recommended.

The existing tide gates are “level control” style gates intended to maintain a constant water level regardless of flow conditions, as in an irrigation channel, not mimic the tidal flow of a marsh. M&N investigated replacing the existing gates with newly manufactured self-regulating tide (SRT) gates designed to more closely mimic natural tidal flow. Discussions were held with three gate manufactures (Waterman, Golden Harvest, and Nehalem Marine Manufacturing) to identify differences between the level control gates and the modern SRT gate designs.

M&N investigated replacing the existing gates “in-kind” and replacing the existing level control gates with newly manufactured level control gates.

AACE Class 4 cost estimates (High 35%, Low -25%) were prepared for the three repair options and rough order magnitude estimates were developed to replace the two existing gates.

TABLE ES-1: AACE CLASS 4 COST ESTIMATES W/ 20% CONTINGENCY (2022 DOLLARS)

Option Bid Total Bid Total Including 20% Contingency High (+35%) Low (-25%)

Option #1 (In-situ Repair) $525,746 $630,900 $851,700 $473,200

Option #2 (Onsite Repair) $480,292 $576,400 $778,100 $432,300

Option #3 (Offsite Repair) $480,219 $576,300 $778,000 $432,200

Level Control (Coated Mild Steel) $1,435,880 $1,723,000 $2,326,000 $1,292,000

Level Control (Stainless Steel) $3,352,482 $4,023,000 $5,431,000 $3,017,000

Self-Regulating Tide Gate $1,489,147 $1,798,000 $2,427,000 $1,349,000 ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight

1. Introduction

1.1. Project Site Overview

Tidal water flow to the Santa Ana River Marsh is currently regulated by two “Avio Style” level control gates located on the southern bank of the Santa Ana River (SAR) in Huntington Beach, CA. Both are roughly 14-ft, 7-in. wide and 8-ft, 10-in. tall, per 1991 design drawings from the U.S. Army Corps of Engineers (USACE).

The south gate is located approximately .5 mile upstream from the mouth of the river, with the north gate located an additional 1 mile further upstream.

• South Gate: Latitude: 33°37'51.65"N Longitude: 117°57'23.25"W

• North Gate: Latitude: 33°38'6.39"N, Longitude: 117°57'17.92"W

See Figures 1 and 2 for Project Area and Site Maps, respectively.

FIGURE 1: AREA MAP OF PROJECT SITE (GOOGLE EARTH)

Project North

Project Site ocpwhpineda Highlight ocpwhpineda Highlight

FIGURE 2: PROJECT SITE MAP (GOOGLE EARTH)

A reference “Project North” was established for this project. Project North runs from the Pacific Ocean to the south upstream along the Santa Ana River, with the subject marsh to the east. Tide gate features, such as ballast float faces, are referenced to the nearest cardinal direction of Project North. See Photo 1 for gate orientation reference.

PHOTO 1: GATE FLOAT FACES, DIRECTIONAL REFRENCE (SOUTH GATE SHOWN)

Each gate is regulated by a float and counterweight on the marsh side of the culvert, which raises/lowers the near vertical gate leaf based on the water level within the marsh. The invert for the south gate is shown in design drawings as -4.0 ft, and -1.0 ft for the north gate. Both inverts are relative to mean sea level (MSL) as defined when the initial design was performed. The gates can be adjusted to open and close at different water surface elevations. Design drawings specify a minimum flow area of 38 ft2 for the south gate between elevations -4.0 and +1.0 ft MSL, and a minimum flow area of 18 ft2 for the north gate between elevations -1.0 ft MSL and +2.0 ft MSL. The as-built specifications for the gates were not available at the time of this investigation.

South Face East Face

North Face

East Face

West Face (Hidden)

Top Face

South Gate

Project North

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1.2. Site Hydraulic Conditions

The original site hydraulic conditions, requirements for tide gates, and plan for restoration of the salt marsh were presented in a 1987 report produced by Simons, Li & Associates titled “Marsh Restoration Lower Santa Ana River Channel”. The design conditions are provided in Table 1.

TABLE 1: ORIGINAL (1987) DESIGN CONDITIONS OF TIDE GATES

Condition Specified Value

Gate Closed Equal or greater than 3.5 ft MSL / 6.26 ft MLLW

Gate Open 1.5 ft MSL / 4.26 ft MLLW

Maximum Through-flow 17 acre-ft/hr*

Peak Velocity 3.0 ft/s**

Notes:

*Maximum through-flow determined for the maximum anticipated water level gradient across the tide gate, associated with local storm flooding within the marsh.

**Modeled scenario with no sill at the mouth of SAR

The 1987 design was intended to increase the tidal range at the marsh entrance from 2.1 ft (pre-construction) to 4.3 ft (post-construction). The 1987 design projected that the installation of the tide gates would increase peak velocities at the marsh entrance from 1.3 ft/s to 3.0 ft/s (if no sill is present at the mouth of the SAR). The original design established the invert for the south tide gate (nearest to Pacific Coast Highway) as -4.0 ft MSL and the invert for the north tide gate as -1.0 ft MSL.

The design conditions were specified such that the “gate closed” water surface elevation would leave space within the marsh to accommodate local flooding associated with a 3-hour 100-year storm. Per Simons, Li & Associates (1987):

“In the event that the water level has reached 3.5 MSL and the proposed tidal gates are closed due to riverine floods, the ponding elevation in the marsh may rise to approximately five feet MSL within the three-hour 100-year flood peak. This assumes no interception, infiltration, and diversion of the rainfall within the contributing drainage basin.”

It is noted that sea levels have risen since the gates were first installed in the mid-1990s. Tidal datums used in the original design are most likely based on the 1960-1978 tidal epoch. Tidal datums at the nearest NOAA tide measuring station (NOAA CO-OPS No. 9410580 at Newport Beach, CA) for the last two tidal epochs (1960-1978) and (1983-2001) are shown in Table 2. Differences in tidal elevation between epochs indicate that MSL has increased by roughly 0.2 ft. Since the previous epoch ended in 2001, MSL has likely increased an additional 0.2 ft. This suggests that the water level thresholds currently used for the tidal gates are slightly lower than the elevations intended in the original design due to sea level rise (SLR). This change is small but expected to increase as SLR continues.

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TABLE 2: TIDAL DATUMS FOR SPECIFIED TIDAL EPOCHS FOR NOAA CO-OPS 9410580

Tidal Datum Acronym 1960-1978 1983-2001

Mean Higher-High Water MHHW 8.53 ft 8.74 ft

Mean High Water MHW 7.78 ft 8.01 ft

Mean Tide Level MTL 5.93 ft 6.13 ft

Mean Sea Level MSL 5.90 ft 6.11 ft

Mean Low Water MLW 4.07 ft 4.25 ft

Mean Lower-Low Water MLLW 3.14 ft 3.33 ft

North American Vertical Datum of 1988 NAVD88 --- 3.51 ft

Station Datum STND 0.00 ft 0.00 ft Note: the elevation for NAVD88 for the 1960-1978 tidal epoch was not published.

For comparison, MSL at Los Angeles, CA is projected to increase between 1.6 ft (low risk aversion1) and

3.6 ft (medium-high risk aversion2) by 2080 when compared to the baseline year of 2000, as defined in the low emissions scenario (OPC 2018). For the high emissions scenario, sea levels are projected to increase between 2.2 ft (low risk aversion) and 4.3 ft (medium-high risk aversion) by 2080. This suggests that tidal water levels can be conservatively expected to increase by 1.6 ft at the mouth of the SAR over the course of the next 50 to 60 years. The anticipated design life for most new structures installed in a marine environment is 50 years.

As SLR continues, the existing gates will begin to close at a point sooner into the tide cycle and at a lower relative elevation of the tide cycle. By 2080 the existing tide gates are anticipated to close at El. +1.7-ft MSL (3.5 ft - 0.2 ft - 1.6 ft) versus their design elevation of +3.5-ft MSL. The low tide may become truncated by the sill (sediment shoal) at the mouth of the SAR, this sill is anticipated to rise commensurate with any increase in MSL. The end result of current tide gate elevations and SLR will result in a reduced tidal range, less tidal influence, and tidal flushing in the marsh. Consequently, the regulating mechanism of the tide gate itself must be able to be easily adjusted by field staff to ensure appropriate water levels and circulation in the Santa Ana River Marsh. Additionally, further consideration should be given to flood protection as the initial intent of the automatic gates was to prevent the SAR from flooding the residential areas south of the marsh.

Under the current conditions, high tide in the marsh is controlled by the closure elevation of the tide gates.

The marsh low tide is controlled by the water level in the SAR, which in turn is controlled by the sill at the river mouth.

Sources:

California Ocean Protection Council (OPC), 2018. State of California: Sea Level Rise Guidance. Technical Report.

1 “Low risk aversion” values indicate that there is approximately a 17% probability that SLR will meet or exceed the provided value.

2 “Medium-high risk aversion” values indicate that there is a 0.5% probability that SLR will meet or exceed the provided value.

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2. Tide Gate Inspection Moffatt & Nichol (M&N) was selected in May 2021 to support the Orange County Department of Public Works (OCPW) in the inspection and assessment of two tide gates and the accompanying culvert structures. This report section addresses Task 2 of the scope of work - Tide Gates Inspection.

Task 2 includes the following subtasks:

• Assess the overall condition of the tide gates. This includes a Level I (visual/tactile) inspection as defined by ASCE Manuals and Reports on Engineering Practice No. 130, Waterfront Facilities Inspection and Assessment (ASCE No.130).

• Quantitatively evaluate local section loss of steel components due to damage or deterioration (corrosion). This includes ultrasonic thickness (UT) measurements of steel elements at critical locations (float, arm) where possible.

• Assess the overall condition of the tide gates’ appurtenances – concrete foundations/culverts and steel trash racks. This includes a Level I (visual/tactile) inspection as defined by ASCE No.130.

• Qualitatively evaluate the integrity and functionality of the gates and surrounding structures considering observed damage and/or deterioration.

• Document details of defects and components to be repaired.

2.1. Inspection Procedures

The initial field inspection was performed on June 1, 2021, with a subsequent confined space inspection on October 28, 2021. Both inspections were conducted by the same 3-member M&N inspection team assisted by OCPW field crews.

The above water inspection included both a Level I visual inspection effort over 100% of the structure and targeted Level III efforts per ASCE No.130.

• A Level I inspection effort is a general visual and/or tactile inspection of components, without the removal of marine growth. Level I inspections are intended to observe the existing overall conditions and to note any gross discontinuities or obvious damage.

• A Level III inspection effort of steel components includes non-destructive testing with a UT gauge (Cygnus Instruments Dive) to measure the remaining steel thickness. Locations for Level III inspection were selected based on the observations of the Level I inspection.

Major components of the tide gate system were given Condition Assessment Ratings using the descriptions and guidelines provided in Table 2-14 of ASCE No. 130, see Table 3. The Condition Assessment Ratings are intended to provide a qualitative description of the condition for each component.

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TABLE 3: CONDITION ASSESSMENT RATINGS (EXCERPT OF TABLE 2-14 FROM ASCE NO. 130)

The initial inspection on June 1, 2021 found the interior spaces of both the north and south gate floats were filled with sand and sandbags. The sand and sandbags act as the ballast weight to balance the gate.

Standing water was observed in the south gate float, and the ballast sand in the north gate was damp. In coordination with OCPW, the M&N team returned for a second inspection day and performed a confined space entry (CSE) inspection of the south gate’s float. OCPW used a vacuum truck to remove the sand, allowing M&N engineers access inside the float. The CSE inspection included both Level I and Level III efforts internal to the float.

2.2. Description Of Structures

The existing tide gate system was conceptually developed in the late 1980s and installed in the early to mid-1990s. The gate system consists of mechanical tide gates, concrete culverts, and an earthen levee.

Inspection, assessment, and recommendations for the earthen levee are outside the scope of this project.

The existing tide gates are based on “constant downstream level control gates” manufactured by Waterman Valve. Level control gates are typically used to maintain a constant water level regardless of flow rate and do not regulate or mimic tidal flow. This style of gate utilizes a counterweight/float box (float) to control the water level from the marsh side of the levee. The floats are surrounded on the bottom and sides by an immovable steel “float shield” to protect the float from debris strikes. The float is connected to the gate leaf by a pivoting connection arm mounted on two bearings.

Per the original design drawings, the south gate has a lower invert elevation at -4.0-ft MSL compared to -1.0-ft MSL of the north gate. See Figure 3 and Photos 2 and 3 for typical gate configurations.

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FIGURE 3: EXISTING TIDE GATE ELEVATION

To Santa Ana River To Marsh

PHOTO 2: TYPICAL TIDE GATE FLOAT, SOUTH GATE SHOWN

PHOTO 3: TYPICAL TIDE GATE LEAF, SOUTH GATE SHOWN

Float

Float Shield

Connection Arm

Pivot

Gate Leaf

Connection Arm

Counter Weight

The tide gates control water flow through the concrete box culvert passing through the earthen levee. The two culverts are the primary connection between the Santa Ana River and the upland marsh. Each culvert is a cast-in-place reinforced concrete box culvert. The culverts are approximately 14.5-ft-wide with a 9-ft vertical opening. See Figure 4 and Photo 4.

On the east side of the earthen levee the box culvert transitions smoothly into the support foundation for the tide gate. The tide gate foundation and the box culvert appear to be monolithic, cast as one structure with no defined boundary separating the culvert and gate foundation. The weight of the tide gate is supported by a large central axle and a pair of bearings, which in turn are supported on the cast-in-place concrete walls of the foundation. See Photo 5 for a typical gate support bearing.

FIGURE 4: EXISTING BOX CULVERT PARTIAL TYPICAL SECTION

PHOTO 4: TYPICAL BOX CULVERT INTERIOR, NORTH GATE SHOWN

PHOTO 5: TYPICAL TIDE GATE BEARING SUPPORT, SOUTH GATE SHOWN

2.2.1.1. Trash Racks

The entrance of each culvert is protected from water born debris by stainless-steel gratings – trash racks.

Each trash rack is secured to the concrete wingwalls of the culvert using embedded stainless steel expansion anchors. See Photo 6 for a typical trash rack.

PHOTO 6: TYPICAL TIDE GATE TRASH RACK, SOUTH GATE SHOWN

2.2.2. Existing Gate Cycle of Operations

The water level in the marsh rises on an incoming tide and moves the float upward, causing the gate leaf on the opposite side of the pivot to descend. The descending gate leaf restricts the size of the culvert opening, reducing water flow into the marsh. A properly balanced gate will completely seal the culvert when the float reaches its highest point of travel. When the water level in the marsh drops, the float descends, raising the leaf and allowing water to flow through the culvert again. Aside from secondary leakage, there is no mechanism to allow water to drain from the marsh when the level control gate is fully closed. This configuration requires the additional “flap” tide style gates adjacent to the main gate to allow water a path to escape the marsh. See Photo 7.

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PHOTO 7: FLAP STYLE GATES, ADJCENT TO SOUTH GATE

The nominal water level in the marsh is determined by the geometry of the tide gate and the weight of the float. Because the geometry of the gate is fixed, the water level in the marsh is directly controlled by the weight of the float. The gate mechanism is sensitive to the buoyancy of the float and requires the system to be correctly balanced. The heavier the float, the higher the water level in the marsh will need to rise before the gate leaf descends. The float may become incorrectly weighted due to several factors, such as improper balancing, steel loss from corrosion, or water infiltration into the float. Improper balancing and water infiltration are assumed to be the largest contributors affecting the buoyancy of the float. Weight changes due to steel section loss from corrosion are assumed to be minimal. See Section 2.3.1.2 for additional discussion on water infiltration into the float.

2.3. Inspection Results

2.3.1. Tide Gates

Overall, both the north and south tide gates are in similar Fair condition. The north gate is in slightly better condition with less extensive corrosion than the south. This is most likely due to the higher invert elevation of the north gate, and it being situated approximately 1 mile farther upstream. As a result, the north gate will experience less inundation during high tide events and is exposed to water with reduced salt content.

2.3.1.1. Gate Exterior

The exterior of both the north and south gates is in Fair condition. The applied protective coating is beginning to fail, exposing the steel to the brackish water of the marsh. The loss of coating has led to widespread surface corrosion, particularly on the floats. This is expected because the floats are generally the only functional component of the tide gate that routinely contacts the water, subjecting them to continuous wet / dry cycles. At isolated locations the corrosion has advanced beyond surface corrosion, resulting in deeper pitting of the steel, particularly on the south and east float faces. The pitting is generally ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight deepest and most noticeable on the top float face, most likely due to standing water from rain or other flooding events.

See Photos 8 and 9 for examples of external steel corrosion. Additional discussion of internal float corrosion is presented in Section 2.3.1.2.

The bottom and lower 1/3 of each float was mostly obscured for exterior visual inspection due an immovable steel shield that surrounds the float. However, the bottom of the north float was visible through a small gap in the float shield. The portions of float that could be inspected through this gap were in good condition with no significant defects noted. See Photo 10. A similar gap was not present in the float shield of the south gate; therefore, a visual inspection of any portions of the exterior was not possible.

PHOTO 8: ISOLATED CORROSION ON PIVOT ARM, SOUTH GATE

PHOTO 9: EAST FACE ADVANCED CORROSION, SOUTH GATE

PHOTO 10: BOTTOM FACE OF FLOAT (INDICATED YELLOW), NORTH GATE

The mechanical elements of the tide gate appeared to be in Satisfactory condition. Due to time restrictions, the tide gates were not observed through a complete natural cycle of operations. However, during the M&N site visit, OCPW used electrical winches to manipulate the gate through the open and closed positions to facilitate the inspection. No significant bypass water flow around the leaf was noted when OCPW manually shut the gates. No evidence of sticking or grinding of the mechanisms was noted. The internal condition of the roller bearing could not be determined, but externally the roller bearing shroud appear in Good condition with minimal corrosion.

The tide gates’ leaves are in Good condition with no significant defects noted. See Photos 11 through 14 for typical gate mechanism photos.

PHOTO 11: TYPICAL ROLLER BEARING SHROUD CONDITION, SOUTH GATE

PHOTO 12: FLOAT TO PIVIOT ARM CONNECTION, SOUTH GATE

PHOTO 13: TIDE GATE LEAF, NORTH GATE

PHOTO 14: TIDE GATE LEAF, SOUTH GATE

2.3.1.2. Tide Gate Floats, Interior Inspection

The interior of both the north and south floats are in Satisfactory condition. The M&N inspection team noted a significant amount of moisture in the interiors of both floats during the June 1 inspection. The north float was damp and dripping with condensation. There was approximately 2 in. of standing water inside the south float. The inspection team did not find evidence of holes to allow water ingress in either float. It is suspected that the any moisture inside the float is due to either seepage under the hatch or atmospheric condensation.

The presence of moisture is a potentially significant issue because it was most likely not accounted for when balancing the tide gate. See Photos 15 and 16 for typical interior photos taken during the June 1 inspection.

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PHOTO 15: DAMP SAND & CONDENSATION, NORTH GATE

PHOTO 16: APPROXIMATELY 2 IN. OF STANDING WATER, SOUTH GATE

Based on discussions with OCPW, only the interior of the south gate was selected for the additional CSE inspection. Photos 17 through 22 show the typical interior condition of the south gate float. In addition to the visual inspection, the inspection team recorded UT measurements on each interior face of the float.

See Appendix I for detailed interior UT measurements.

The coating on the interior of the floats appears to be a two-stage coating system. The coating system appears generally intact, but the top coating is beginning to fail in isolated areas. The yellow arrow in Photo 18 indicates the top black coating over the grey undercoat.

Despite the moisture, the interior steel of both floats is generally free of significant corrosion and the protective coating appears mostly intact. The interior surfaces of the float are likely protected from corrosion because the ballast sand and the semi-sealed nature of the float helps reduce free oxygen exchange with the atmosphere. Where thin steel was noted, it is due to exterior steel pitting. The interior steel surface is flat and unpitted except in isolated locations. Photo 23 compares the same area of the float, from both the inside and outside. The exterior steel is heavily pitted, but the interior steel is flat with well adhered coating.

There is 3 to 4 in. of sand in the bottom of the float that could not be removed by the vac-truck. The sand obscured the bottom plate of the float from a general visual inspection. Using an inspection hammer, the team was able to probe through the sand. The floor of the float appeared sound with no holes or significant pitting detected. Steel support ribs have been welded to the floor of the float, providing additional strength and stiffness to support the internal ballast. These ribs are well attached and in good condition. In addition to the sand, pieces of scrap steel were placed in the float to act as ballast. One such piece is indicated with a yellow arrow in Photo 21.

The steel surrounding the hatch on the top face is in Poor condition, see Photos 24 and 25. There is clear evidence of corrosion and section loss on both the interior and exterior surfaces. This advanced corrosion is most likely due to heat sensitization of the steel or protective coating damage when the hatch flange was welded in place. Inside the float, away from the welded hatch, the steel was in good condition.

PHOTO 17: INTERIOR OF SOUTH GATE, NORTH FACE, UT COUPLANT GEL INDICATED RED

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PHOTO 18: INTERIOR SOUTH GATE, SOUTH FACE

PHOTO 19: INTERIOR SOUTH GATE MINOR SURFACE CORRSION INDICATED, EAST FACE

PHOTO 20: INTERIOR SOUTH GATE WEST FACE

PHOTO 21: INTERIOR SOUTH GATE (SUPPORT RIB INDICATED RED), BOTTOM FACE

PHOTO 22: INTERIOR SOUTH GATE CLEAN STEEL, TOP FACE

PHOTO 23: EAST FACE INTERIOR / EXTERIOR COMPARISON

PHOTO 24: INTERIOR SOUTH GATE HATCH DELAMINATION, EAST SIDE OF TOP FACE

PHOTO 25: EXTERIOR SOUTH GATE HATCH DELAMINATION, TOP FACE

2.3.2. Tide Gate Support and Culverts

The cast-in-place concrete forming the culvert and tide gate support is typically sound and in Satisfactory condition. The concrete is free of significant cracking, spalling, or other evidence of distress. When sounded, the interior walls and ceiling of both culverts was firm with no indication of spalling or concrete delamination. The supporting foundations for the culverts were obscured by the earthen levee and were inaccessible during the inspection. There is no evidence such as differential settlement or structural cracks, which indicates that the foundations are in Satisfactory condition.

PHOTO 26: INTERIOR OF CULVERT, SOUTH GATE

PHOTO 27: INTERIOR OF CULVERT, NORTH GATE

There is sand accumulation inside both culverts. The entirety of the south culvert floor and a significant portion of the north culvert floor is obstructed by the sand and could not be viewed or inspected by the M&N team. The accumulated sand on the culvert floors ranged from a few inches to several feet deep.

The amount of sand in the south culvert has accumulated to a point that there is potential for it to interfere with normal operations of the gate, possibly preventing it from fully closing even at elevated tides. This condition could not be verified by the M&N inspection team because the mechanical winches used to secure the gate open or closed while the inspection team was in the culvert left an approximately 6-in. gap between the gate and the bottom of the culvert. Photos 28 and 29 show the extent of sand accumulation in the south culvert.

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PHOTO 28: SAND ACCUMULATION, SOUTH GATE

PHOTO 29:SAND ACCUMULATION, SOUTH GATE

Seaward

Closure Plane

Marsh

Sand Mounds Upward ~30-in.-high

2.3.2.1. Tide Gate Steel Insert

As noted in Section 2.2, a steel insert was cast into the concrete foundation to form a seat for the gate leaf.

In the north culvert, portions of the steel insert floor are visible and accessible through the sand. Where accessible for inspection, the steel insert is heavily pitted, and soft and flexible where probed. This indicates there is a gap between the steel insert and the concrete foundation. The design drawings do not indicate a steel thickness for this portion of the insert, but UT measurements of 0.390 in. were recorded on adjacent clean flat steel. UT measurements as low as 0.145 in. (approximately 60 to 65 percent section loss) were recorded inside corrosion pits.

Additionally, near the gate opening on the east end, a hole in the steel insert was identified. This hole was approximately 12-in.-long by 3-in.-wide by 2 to 3-in.-deep and was most likely caused by corrosion. This hole is a potential pathway for water to exit the culvert where it is not intended. This could potentially create sinkholes or otherwise disturb the stability of the foundation. The inspection team did not observe any indication of sinkholes, settlement, or instability in, around, or above the box culvert. Photos 30 through 32 show the steel deterioration of the north culvert.

PHOTO 30: STEEL INSERT, NORTH GATE

PHOTO 31: POTENTIAL CORROSION HOLE IN FLOOR OF STEEL INSERT, NORTH GATE (INDICATED YELLOW)

PHOTO 32: THIN SPOT IN FLOOR OF STEEL INSERT (LOOKING DOWN), NORTH GATE

Inspection Hammer (~12-in.-long)

UT ~0.145in.

2.3.3. Trash Rack Condition

The trash racks are in Serious to Critical condition. At the time of inspection, all the trash racks were clogged with debris and had significant damage to the concrete foundation and steel gratings. The identified damage includes buckling of the steel gratings, displacement of the steel gratings, and pull-out failure of the embedded concrete anchors.

The damage to the trash racks is most likely caused by debris becoming trapped against and clogging the grating during tidal swings. When clogged, the flow of water through the trash rack is restricted, increasing the hydrostatic pressure on the grating. The increased hydrostatic pressure is large enough to cause significant damage to the trash racks. The gratings have all failed / buckled inward toward the upland marsh, indicating that the damage is caused by debris carried in from the SAR on the incoming tide and not from upland marsh debris. Photos 33 through 36 show the typical condition of the trash racks.

PHOTO 33: SAR SIDE TRASH RACK, NORTH GATE

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PHOTO 34: MARSH SIDE TRASH RACK, NORTH GATE

PHOTO 35: SAR SIDE TRASH RACK, SOUTH GATE

Displaced Trash Rack

Failed Anchor

PHOTO 36: MARSH SIDE TRASH RACK, SOUTH GATE

Failed Anchors

3. Remaining Service Life The observable condition of the tide gates is commensurate with their age and the environment to which they are exposed. The tide gate and culvert structures were built and installed in the early to mid-1990s, making them nearly 30 years old. The conditions noted during the inspection, detailed above, are most likely due to the aggressive marine environment and not from operational use, overstress, or abuse.

Waterfront structures designed and built in the late 20th century were typically designed to have a 40 to 50-year service life. The concept of remaining service life, as it pertains to existing waterfront infrastructure, is often misunderstood. Service life can be defined as the length of time that a structure, in this case the tide gates, can be used economically before emergent damage causes increasing interruptions in operations or becomes a threat to public health and safety. The damage affecting individual components does not typically degrade so as to cause sudden "catastrophic failure," but the damage can continue to decay until a series of less dramatic occurrences make the limitations of the component obvious.

The service life for structural steel in the marine environment is generally determined by how well corrosion of the steel is managed. Corrosion of mild steel is due to a reduction / oxidation (redox) reaction between the base metal, atmospheric oxygen, and water. Any salt (NaCl) that is present increases the electrical conductivity through the water, thereby increasing the reaction rate. The byproduct of this redox reaction is the formation of the reddish-brown layer iron oxide, rust, on the surface of the steel. Iron oxide is not tightly adhered to the base metal and readily flakes off, exposing a fresh steel layer allowing the cycle to continue.

Corrosion of mild steel exposed to the marine environment may be slowed using either sacrificial anodes or protective coatings.

The service life of reinforced concrete elements in the marine environment is generally determined by how well steel reinforcement is protected from corrosion. Corrosion of the steel reinforcement causes a large volumetric expansion of the steel, resulting in internal stresses on the surrounding concrete. The internal stresses often exceed the tensile strength of the concrete, resulting in cracking and spalling of the concrete cover material. With cracking comes greater exposure to the marine environment, resulting in increased corrosion. Loss of concrete section due to spalling, combined with loss of competent steel in the reinforcement due to corrosion, leads to losses in section properties and rapid decreases in capacity.

Corrosion of the underlining reinforcing steel is typically initiated when the concentration of chloride ions (CL-) reaches 500 ppm.

The in-situ concentration of CL- of the culvert and support foundations is unknown. No concrete core samples were taken from the tide gate culverts, so a direct measurement of the CL- concentration was not obtained. The absence of corrosion cracking and spalling indicate that the concrete is sound and in generally good condition.

When considering the future of a marine structure that is approaching the end of its service life, an owner is presented with some options, which can be classified as follows:

• Null or “do nothing” option: While always an option, it is not recommended for this project. The tide gates are required to prevent upland flooding during high tide and storm events, these events are only expected to increase with SLR. It may be possible to defer maintenance and repairs because, based on the inspection results, most of the identified conditions do not require immediate attention and the gates appear to be capable of performing their intended function. It needs to be considered that the deterioration of marine structures generally advances at an exponential rather than a linear rate. This means that once the deterioration of a structures has started, it can very quickly advance because protective elements are no longer functioning. This can lead to significantly increasing future repair scope of work and project costs.

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• Rehabilitation: This alternative presents an owner with two paths short of full replacement. An owner may choose to embark on a progressive repair program, where the minimum repairs are performed on a cyclic basis to support limited function of a facility. Or the owner may embark on a more aggressive program, which involves preserving and supplementing salvageable components of the facility and replacement of significantly deteriorated aspects of a facility.

See Engineering Assessment: Option 1 Repair and Maintain Existing Tide Gates for additional discussion on repairing and rehabilitating the tide gates.

• Replacement: An owner may choose to replace a facility when the cost/benefit analysis indicates that rehabilitation and maintenance over a select service life period is exceedingly costly when compared to construction of a new facility. New facilities may be designed to better fit projected use case.

See Engineering Assessment: Option 2, Tide Gate Replacement for additional discussion on replacing the tide gates ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight ocpwhpineda Highlight

4. Engineering Assessment: Option 1 Repair and Maintain Existing Tide Gates

The tide gates themselves are in overall Fair condition, with some individual elements in Poor condition.

The associated culverts and foundations are in Satisfactory condition. The trash racks are in Serious to Critical condition. None of the defects identified during the inspection warrant emergency action. However, the defects identified do warrant a prioritized repair and maintenance program in order to extend their service life for another 10 years.

The general steps required to repair and maintain the existing gates are as follows:

1. Clean the gates of marine growth, corrosion, and loose paint.

a. See Section 4.2.1.2 for discussion on cleaning requirements.

2. After cleaning, identify thin areas of steel or any cracked welds. Fabricate and weld steel patches to cover sections of thin steel on existing gate. If practical, inspect main bearings and other critical wearing surfaces for degradation, replace as necessary.

3. Recoat tide gates with epoxy coating to prevent further corrosion.

a. See Section 4.2 for discussion of epoxy coatings.

4. Repair or replace trash racks as appropriate.

5. Repair north gate steel insert.

6. Rebalance tide gates after repairs are made. During gate rebalancing, it is recommended that an alternate ballast material be considered. Preferably materials with less porosity that are less suspectable to moisture accumulation than sand. Waterman recommends lengths of rebar cut to fit inside the ballast box. Steel rebar is fabricated from relatively corrosion resistant steel and may be cut in the field to achieve the precision required to balance the gate. Waterman states even minor changes of the ballast weight can have a significant impact on the operation of the gate.

4.1. Proposed Service Life Extension Repair Options

4.1.1. Gate Repairs

Gate Repair Option 1: In-Situ Rehabilitation

It is possible to repair the tide gates in-situ without removing them from their foundations. Cleaning and recoating steel in-situ is a common practice on marine structures, and most marine contractors have experience working in the water and around tide cycles. The primary benefit of performing the working in-situ is not having to remove the gate from active service. However, in-situ repairs would need to comply with all environmental and regulatory requirements. Performing any repair work in-situ would be at the discretion of the regulatory agencies. Additional effort may be needed to secure permits and develop and execute additional Best Management Practices (BMPs) to mitigate environmental hazards.

• Pros:

− No additional expenses for crane or trucking operations to remove tide gates.

− Gates remain in service during repairs, particularly during welding and recoating operations because crews may work around tide cycle.

− Cleaning requirements would be reduced from SP-6 to SP-3 or SP-11. See Section 4.2.1.2 for discussion of cleaning requirements.

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• Cons:

− Additional environmental regulations for working in and around the SAR.

− Cleaning operations require further discussion with regulatory agencies to determine appropriate BMPs to prevent water contamination. BMPs required to prevent debris from entering water.

− In-situ work may require temporary containment structures such as steel sheet pile cofferdams to prevent environmental contamination.

− Portions of the tide gates, particularly the lower portion of the floats, are not fully accessible.

− Quality and life span of coating likely reduced due to reduced…