Design_Report_20260416.pdf

PREPARED FOR

California Army National Guard

10106 Bear Hollow Drive

Rancho Cordova, California 95670

PREPARED BY

Weaver Consultants Group of California, LLC

1 Technology Drive, Suite C-515

Irvine, California 92618-2327

Project No. 5890-300-01-67

DESIGN REPORT

Main Garrison Wastewater Treatment Plant Modernization

Camp Roberts, California

April 16, 2026

April 16, 2026 Project No. 5890-300-01-67

MAJ Myles Colendich

Construction Project Officer

Facilities and Infrastructure

CALIFORNIA MILITARY DEPARTMENT

10106 Bear Hollow Drive

Rancho Cordova, California 95670

Design Report

Camp Roberts, California

Dear MAJ Colendich:

This report documents the design for modernizing the wastewater treatment plant serving the Main

Garrison at Camp Roberts, California. If you have any questions about the report or require additional information, please do not hesitate to contact the undersigned at (949) 296-0977 or at thunt@wcgrp.com. Weaver Consultants Group of California, LLC (WCG) appreciates the opportunity to be of service to the California Army National Guard.

Respectfully submitted, WEAVER CONSULTANTS GROUP OF CALIFORNIA, LLC

Tim Hunt, P.E.

Senior Project Manager

Signed and Sealed April 16, 2026

TMH:hf

Enclosure cc:

P:\5890_CMD\300_Camp_Roberts\01_67-WWTP Type B Design\Report of Waste Discharge\Report of Waste Discharge_2018-07-05.docx

Main Garrison Wastewater Treatment Plant Page i

Camp Roberts, California April 16, 2026

TABLE OF CONTENTS

Page

LIST OF FIGURES ....................................................................................................................... i

LIST OF ABBREVIATIONS AND ACRONYMS .................................................................... ii

1.0 INTRODUCTION

1.1 BACKGROUND AND HISTORY

1.1.1 Plant Rehabilitation and Denitrifying Upgrades

1.1.2 2014 Permit Requirements

1.2 EXISTING WASTEWATER TREATMENT INFRASTRUCTURE

1.2.1 Headworks - Diversion Chamber

1.2.2 Primary Clarifier

1.2.3 Trickling Filters

1.2.4 Secondary Clarifier

1.2.5 Denitrifying Filter

1.2.6 Sludge Digesters

1.2.7 Percolation Ponds

1.3 WWTP UPGRADE PROGRAM STATUS

1.3.1 Zero and Low Flows

1.3.2 Peak Flows

1.3.3 System Automation

1.3.4 Aging Infrastructure and System Leaks

1.3.5 Lack of Equalization

1.4 REEVALUATION OF THREE-PHASE PLAN

1.5 ENGINEERING FEASIBILITY STUDY REEVALUATION

1.6 PRELIMINARY DESIGN REPORT

1.7 DESIGN EVALUATION

1.8 REPORT ORGANIZATION

2.0 BASIS OF DESIGN

2.1 INFLUENT WASTEWATER QUALITY

2.2 EXPECTED WASTEWATER VOLUME

2.2.1 Zero Flow

2.2.2 Baseline Flow

2.2.3 Weekend Flow

2.2.4 Annual Training Flow

2.2.5 Maximum Design Flow

2.2.6 Emergency Flow

2.3 REGULATORY REQUIREMENTS

3.0 DESIGN

3.1 MEMBRANE BIOREACTOR (MBR) PACKAGE PLANT MODELING

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Page

3.1.1 Plant Configuration

3.1.2 Simulation Results

3.2 PROPOSED DESIGN

3.3 HEADWORKS MODIFICATIONS

3.4 DIVERSION CHAMBER

3.5 DIVERSION MANHOLE AND OVERFLOW MANHOLE MODIFICATIONS

3.6 LOW FLOW WET WELL

3.7 INFLUENT EQUALIZATION

3.7.1 Repurpose Existing Secondary Clarifier as Equalization Tank

3.7.2 MBR Feed Pumps and Piping

3.7.3 Electrical and Controls

3.8 MBR PACKAGE PLANT

3.8.1 Subgrade Preparation

3.8.2 Foundation

3.8.3 MBR Unit and Installation

3.8.4 Electrical and Controls

3.9 SLUDGE HANDLING

3.9.1 Subgrade Preparation

3.9.2 Foundation

3.9.3 Sludge Handling Unit and Installation

3.9.4 Sludge Transfer Piping

3.9.5 Electrical and Controls

3.10 PERMEATE EQUALIZATION PONDS

3.10.1 Grading and Subgrade Preparation

3.10.2 Liner and Anchor Trenches

3.10.3 Liner QA/QC

3.10.4 Transfer Piping

3.10.5 Permeate Retention Pond Pump Station (PRPPS)

3.10.6 Electrical and Controls

3.11 DISCHARGE FROM THE MBR

3.12 OVERVIEW OF SYSTEM CONTROLS AND OPERATING CONDITIONS

3.13 SYSTEM-WIDE ELECTRICAL AND CONTROLS UPGRADES

REFERENCES

FIGURES

APPENDIX A: CCRWQCB WDR ORDER R3-2014-0046

APPENDIX B: SITE PLAN WITH PIPELINE VIDEO LOGGING SUMMARY

APPENDIX C: MEMPAC‐MTM PACKAGE TREATMENT SYSTEM,

MODELING AND SIMULATION REPORT

APPENDIX D: DESIGN DRAWINGS

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LIST OF FIGURES

Figure No. Title

1 Camp Roberts Location Map

2 Site Plan, Current Layout

3 Proposed Site Plan

4 Proposed MBR System Layout

5 Process Flow Diagram, Proposed MBR System

6 Process Flow Diagram, WWTP

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LIST OF ABBREVIATIONS AND ACRONYMS

BOD biological oxygen demand

CA ARNG California Army National Guard

CCRWQCB Central Coast Regional Water Quality Control Board

DO dissolved oxygen gpd gallons per day gpm gallons per minute

HDPE high-density polyethylene

LFWW low flow wet well

MBR membrane bioreactor mg/L milligrams per liter mL/L milliliter per liter

M&RP monitoring and reporting program

NH3 ammonia

NO2 nitrite

NO3 nitrate

PFAS polyfluoroalkyl substances

PLC programmable logic controller

PRPPS permeate retention pond pump station

PSI pounds per square inch sNdN simultaneous nitrification and denitrification

TDS total dissolved solids

TSS total suspended solids

WCG Weaver Consultants Group of California, LLC

WDR waste discharge requirements

WSC Water Systems Consulting, Inc.

WWTP wastewater treatment plant

Main Garrison Wastewater Treatment Plant Page 1

1.0 INTRODUCTION

Camp Roberts is an active military training facility located on the central coast of California. It is situated on U.S. Highway 101, about 12 miles north of Paso Robles and about 26 miles east of the

Pacific Ocean. The camp occupies 42,784 acres, or approximately 60 square miles, the majority of which is located west of Highway 101. Nearly one-half of Camp Roberts lies within Monterey

County, with the remainder lying within San Luis Obispo County (Figure 1). The training facility is currently operated and maintained by the California Army National Guard (CA ARNG).

Camp Roberts features two wastewater treatment facilities, the Main Garrison Wastewater

Treatment Plant (WWTP) and the East Garrison WWTP. This Design Report is focused only on proposed upgrades of the Main Garrison WWTP (henceforth referred to as the WWTP). The

WWTP was upgraded in 2016 via rehabilitation of existing (mothballed) treatment structures and the installation of a new denitrifying filter. These upgrades constituted the first phase of a three-phase plan intended to restore the functionality of aging infrastructure and to comply with new effluent limits.

1.1 BACKGROUND AND HISTORY

Camp Roberts was initially constructed in the 1940s as a training facility for troops preparing for combat in the pacific theater during World War II. Records show that the WWTP was designed and constructed in the 1950s to treat wastewater generated at the Main Garrison. The plant was designed to accommodate the wastewater flows expected during full occupancy of the garrison.

At the time, the maximum expected flow was considered to be 2 million gallons per day (mgd).

The original construction included a headworks, two clarifiers, two trickling filter beds, a chlorination chamber, and two sludge digesters.

In or around 1979, the Camp implemented significant modifications to the WWTP. The operation of the plant was scaled back both in overall capacity and in terms of treatment processes. As part of the modifications, one of the clarifiers (the Secondary Clarifier) and a trickling filter (Trickling

Filter 2) were removed from service, eliminating system redundancy and effectively halving the hydraulic capacity of the plant. The chlorination chamber was filled with crushed rock and eliminated from the treatment process. One of the sludge digesters was abandoned in place and the other ended up being used as a sludge holding tank over time. Following the 1979 renovation and until a major permit revision in 2014, the WWTP was typically able to operate within the parameters prescribed by regulation and permit.

1.1.1 Plant Rehabilitation and Denitrifying Upgrades

The Central Coast Regional Quality Control Board (CCRWQCB) issued revised Waste Discharge

Requirements (WDR) Order R3-2004-0106 in 2004 based on site-specific information provided by the CA ARNG. While the effluent nitrate discharge limit prior to this WDR is not known, the

2004 WDR included an effluent nitrate discharge limit of 7.7 milligrams per liter (mg/L).

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Records indicate that while the WWTP was able to achieve the discharge limits for most parameters, there were some issues with effluent sodium, sulfate, and nitrate. While the historical exceedances of sodium and sulfate were less frequent and lower in magnitude, the effluent nitrate was consistently above the effluent limit of 7.7 mg/L. In response to this, the CA ARNG contracted Kennedy/Jenks Consultants (Kennedy/Jenks) in 2010 to assess the condition of the

WWTP and propose any necessary upgrades to modernize the plant and address the nitrate issue.

During a subsequent meeting, the CCRWQCB indicated to Camp Roberts personnel that preparations should be made for more restrictive future WDR conditions. Specifically, future requirements would have more stringent effluent controls, particularly with regard to total nitrogen.

After considering various treatment alternatives, Kennedy/Jenks proposed a series of facility upgrades to be implemented over three phases of construction (Kennedy/Jenks, March 1, 2012).

The phased approach was recommended to allow continuous operation of the plant during construction. The principal elements of Phase 1 were:

• automation of the bar screening at the headworks,

• rehabilitation of the previously abandoned clarifier (the Secondary Clarifier) and

Trickling Filter 2 (thus providing increased capacity and system redundancy), and

• installation of a fluidized bed nitrate reactor (denitrifying filter) to meet a total nitrogen limit of 10 mg/L.

The subsequent phases would include refurbishment of the Primary Clarifier and Trickling Filter 1, installation of additional denitrifying filters, and would address the antiquated sludge handling and digestion equipment.

1.1.2 2014 Permit Requirements

In 2014, in response to a Report of Waste Discharge prepared by Kennedy/Jenks, the CCRWQCB issued new WDR Order R3-2014-0046 for Camp Roberts (Appendix A). The 2014 WDR included new limits for three constituents: five-day biochemical oxygen demand (BOD), total suspended solids (TSS), and total nitrogen, as shown in the table below. Total nitrogen is considered to be the sum of organic nitrogen, ammonia (NH3), nitrite (NO2), and nitrate (NO3). Additional effluent parameters are included but are not considered salient in the context of treatment design.

Parameter Value

(mg/L)

Biochemical Oxygen Demand (BOD) 30

Total Suspended Solids (TSS) 30

Total Dissolved Solids (TDS) 1,250

Sodium 340

Chloride 240

Sulfate 250

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Boron 3.5

Total Nitrogen (as N) 10

The order also includes alternative effluent limits for potential emergency conditions at Camp

Roberts. If the facility is required to temporarily (up to 90 days) shelter the public in times of emergency, the following effluent limits may be used in lieu of all those above:

Parameter Value

(mg/L)

Biochemical Oxygen Demand (BOD) 90

Total Suspended Solids (TSS) 90

The order also acknowledges the principal treatment processes as described in the Report of Waste

Discharge prepared by Kennedy/Jenks (March 7, 2014). These are listed as “grit removal, comminution, primary clarification, trickle filtering, and secondary clarification.” Although use of a continuous upflow denitrifying filter is not explicitly prescribed in the order, it is referenced via the Report of Waste Discharge. Furthermore, the annual average daily flows are limited under the conditions of the order in terms of how many denitrifying filters have been installed. The

Phase 1 upgrades were designed for an annual average capacity of 40,000 gallons per day (gpd).

Installation of additional denitrifying filters would increase the permitted annual average capacity to 150,000 and 300,000 gpd (for a total of two and three filters, respectively).

The 2014 WDR Order contains a Monitoring and Reporting Program (M&RP) intended to evaluate compliance with the order. The M&RP includes effectively continuous monitoring of the influent flowrate into the WWTP. Monthly grab samples of wastewater influent must also be collected and analyzed for BOD and TSS, although influent concentrations are not controlled under the

WDR.

The M&RP requires that water quality parameters in the WWTP effluent are evaluated via periodic grab samples. Weekly samples must be collected and analyzed for settleable solids, pH, BOD, and TSS. The remaining general chemistry (including nitrogen) must be analyzed semiannually in March and September, with analysis for selected metals also required annually in September.

Once every five years there is an additional requirement to test the effluent grab samples for volatile organic compounds, polychlorinated biphenyls, and certain pesticides. Based on the requirements of the M&RP described above, compliance with the prescribed total nitrogen limit for plant effluent would only be monitored on a semiannual basis. Regardless of the sampling frequency, it is the intent of both the CCRWQCB and the CA ARNG that the WWTP effluent be in compliance with the limits set forth in the WDR at all times.

1.2 EXISTING WASTEWATER TREATMENT INFRASTRUCTURE

Major construction associated with Phase 1 of the Kennedy/Jenks plan was completed in June

2016, although system leaks prevented operation of some secondary treatment equipment, specifically the rehabilitated Secondary Clarifier and Trickling Filter 2. A site plan showing the

Main Garrison Wastewater Treatment Plant Page 4 current WWTP layout and flow regime is provided in Figure 2, with the major treatment components described below.

1.2.1 Headworks - Diversion Chamber.

Wastewater is transported to the WWTP headworks via the existing collection system serving the Main Garrison (located on the opposite side of Highway 101. The collection system crosses beneath the highway at two locations and approaches the WWTP from both the north and south. After passing through either the north or south grit chamber, influent wastewater combines and passes through the headworks. The headworks provides solids removal via a self-cleaning mechanical bar screen, with 3/8-inch bar spacing, installed during Phase 1 construction. A permanently installed flow meter measures influent flow rate at the headworks using a non-contacting ultrasonic sensor mounted over a 6-inch

Parshall flume. After passing through the headworks, wastewater flow enters the Diversion Chamber, where it can be directed to either the Primary Clarifier, the Secondary

Clarifier, or the Secondary Effluent Pump Station via manhole

(MH-3) by operating slide gates that were installed as part of the Phase 1 upgrades.

1.2.2 Primary Clarifier

The Primary Clarifier remains in use following the completion of Phase 1 and was scheduled for refurbishment during Phase 2. The clarifier is approximately 85 feet in diameter and 12 feet deep, with a volume of approximately 500,000 gallons when full. As is typical for this type of clarifier, it is operated with a rotating skimmer blade to remove scum at the surface. Sludge is removed from the Primary Clarifier via subsurface piping and a sludge pump. Under most current flow conditions, nominal detention time in the

Primary Clarifier is typically upwards of

50 days. The treated water flows over the peripheral weirs associated with the clarifier and into a launder collector trough prior to flowing

(by gravity) into the primary effluent spillway channel that connects to the main wet well.

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1.2.3 Trickling Filters

Trickling Filter 1 remains in use following the completion of Phase 1 and was scheduled for refurbishment during Phase 2.

Trickling Filter 1 is approximately 90 feet in diameter and is filled with random pack plastic media to a depth of approximately 4 feet. Wastewater from the main wet well is pumped to a motorized rotary distributor arm of the trickling filter, continuously spraying over the filter surface, before percolating through the packing media.

Biological treatment is achieved by a population of microorganisms attached to the filter media.

The piping that connects the main well pump to Trickling Filter 1 is a dedicated line without any capability of routing water to Trickling Filter 2.

Trickling Filter 2 has similar dimensions to Trickling Filter 1 and was designed to operate in the same manner. Trickling Filter 2 was rehabilitated in 2015 after being out of service for approximately two decades. The interior was resurfaced and new packing media was installed along with a replacement rotary distributor. As of October 2017, Trickling Filter 2 remains out of service due to subsurface leaks in the associated piping. Similar to Trickling Filter 1, the piping that connects the main well pump to Trickling Filter 2 is a dedicated line without any capability of routing water to Trickling Filter 1.

1.2.4 Secondary Clarifier

The Secondary Clarifier has similar dimensions to the Primary Clarifier and was designed to operate in the same manner to provide secondary clarification. The Secondary Clarifier was rehabilitated in 2015 after approximately two decades out of service. The interior was resurfaced and new mechanical equipment was installed. As of October 2017, the Secondary Clarifier remains out of service due to subsurface leaks in the associated piping. When operational, the treated water flows over the peripheral weirs and into a launder collector trough prior to flowing into the Secondary Clarifier spillway channel and into the secondary effluent pump station by gravity.

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1.2.5 Denitrifying Filter

Phase 1 improvements included the installation of a fluidized bed nitrate reactor, typically referred to as a denitrifying filter. The denitrifying filter uses a continuous backwash sand filter with suspended biofilm in the sand media. The biological microorganisms suspended in the filter are capable of removing nitrate from wastewater. The denitrifying filter was installed downstream of the existing clarifiers and trickling filters (Figure 2). By this point in the treatment process, the ammonia in the raw effluent will have undergone nitrification and converted to nitrate.

Partially treated water from the secondary effluent pump station is pumped to the denitrifying filter using pumps with variable frequency drives. The normal operating range for the denitrifying filter is between 20 and 70 gallons per minute (gpm) (28,800 and

100,800 gpd). At flows lower than 20 gpm, the sand media in the filter is prone to cementing (which requires cleaning and prevents efficient operation of the equipment). Given that flows of less than 20 gpm are not uncommon at the WWTP, denitrifying filter effluent is frequently recirculated to the headworks. This recirculation can be shut off once sufficient wastewater flows are entering the WWTP from the collection system, however this is a manual process and not automated. At flows greater than 70 gpm, the filter is unable to operate hydraulically (risk of blowout) and cannot reliably remove nitrogen to the required effluent limit.

The denitrifying filter can accommodate typical wastewater flows (with recirculation) but is unable to handle the high flows and rapid changes in flow associated with the erratic troop population at

Camp Roberts (Section 2.2). The flows experienced during training periods exceed not only the capacity of the filter to treat for nitrate, but also the recommended hydraulic capacity of the filter.

Treated water from the denitrifying filter is continuously monitored for nitrate, nitrite, and ammonia using an online analyzer, and treated water that satisfies the required total nitrogen limit of 10 mg/L is discharged into percolation ponds via Manhole MH-1. Flows greater than the normal operating range of the denitrifying filter overflow from the secondary effluent pump station to the percolation ponds via Manhole MH-1, thus bypassing the denitrifying filter (Figure 2).

1.2.6 Sludge Digesters

Two existing sludge digester tanks are located at the WWTP, originally designed to accommodate the sludge generated from the primary and secondary clarifiers. Each digester is approximately

40 feet in diameter with a side water depth of 15 feet. They were originally sized to handle the sludge produced in treating up to 2 mgd of wastewater from the Main Garrison. As such, the current WWTP influent flow rates are too low to generate sufficient sludge for even a single digester to function without an external power source (Kennedy/Jenks, June 25, 2013).

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Based on the available information, the two existing sludge digester tanks have not been used as originally intended for anaerobic digestion since after the rehabilitation in 1979. The vessel to the southeast has been effectively sealed and abandoned in place, and the vessel to the northwest is primarily used as a sludge holding tank. The structural integrity of the tanks and associated piping is questionable and not well understood.

The sludge accumulated in the active tank is periodically pumped to the sludge drying beds. Dried sludge is then disposed of at an approved facility.

1.2.7 Percolation Ponds

WWTP system effluent discharges to one of three existing percolation ponds (Figure 2). These ponds are not used for treatment as of the completion of Phase 1.

1.3 WWTP UPGRADE PROGRAM STATUS

Avocet Environmental, Inc. (Avocet) and Water Systems Consulting, Inc. (WSC) were contracted by the CA ARNG during Phase 1 of construction to serve as commissioning agents. In this capacity, Avocet and WSC were required to verify that the upgrades were installed correctly and that the upgraded WWTP would be able to consistently meet the operational requirements of the new permit. During the construction and commissioning process, Avocet and WSC identified a series of design and operational issues. Several concerns were addressed and rectified during the

Phase 1 construction project; however, there are several remaining issues impacting the operation of the WWTP, as discussed below.

1.3.1 Zero and Low Flows

As noted above, the WWTP was originally designed to operate with a hydraulic capacity of 2 mgd.

This capacity provided for maximum occupancy of the Main Garrison at that time (on the order of

10,000 troops) and also for expansion of the facility or flows during an emergency condition. In practice, average daily flows between 2009 and 2016 were approximately 24,000 gpd. If training events are excluded from the data set, average daily flows were closer to 10,000 gpd. Furthermore, when considering losses (leaks and evaporation) at the plant, the net flow rate can easily be zero or negative. This is especially true at night during periods when no active training is taking place on post. At these times, there is unlikely to be any wastewater generated at the Main Garrison.

After reviewing the Phase 1 plans prior to construction, Avocet queried Kennedy/Jenks on its proposed denitrifying filter operation under these low flow conditions (i.e., flows lower than

20 gpm, the minimum required by the denitrifying filter). Kennedy/Jenks agreed that recirculation was necessary to maintain the function of the denitrifying filter and modified their design to include recirculation capability from the denitrifying wet well to the plant headworks.

It appears that this approach has been successful in terms of hydraulic operation of the denitrifying filter. However, the continual recirculation of treated water raises potential problems with the efficacy of the treatment equipment. The biological processes in the trickling filters and the

Main Garrison Wastewater Treatment Plant Page 8 denitrifying filter are dependent on untreated influent wastewater as a food and nitrate source for the microorganisms contained therein. As recirculated (treated) water dilutes the plant influent, the microorganisms in the trickling filters and the denitrifying filter are effectively starved and, consequently, their populations tend to reduce significantly. Thus, when the Main Garrison does generate large wastewater flows, the biological processes are prone to an extended response time as bacteria populations are reestablished, possibly resulting in noncompliance for effluent total nitrogen and/or BOD.

Under these conditions, the likelihood of effluent BOD exceeding the discharge limit of 30 mg/L is higher because of the higher dosage of carbon source that may be added to the denitrifying filter to stimulate the microbial populations and provide the required carbon source in the carbon-depleted, recirculated water. The denitrifying filter monitors the total nitrogen and has the capability of recirculating noncompliant treated water to the Headworks if the total nitrogen in the effluent exceeds 10 mg/L. However, there is no real-time monitoring for effluent BOD

(measurement requires five-day laboratory analysis).

1.3.2 Peak Flows

As described in greater detail in Section 2.2, the WWTP experiences a wide range of influent wastewater flow conditions. As a baseline condition, daily flows are generally very low (less than

10,000 gpd) when Camp Roberts is only occupied by permanent staff. Weekend training activities are frequent and typically generate average daily flows on the order of 40,000 gpd. Larger-scale annual training events (two or three times a year) represent Camp Roberts as fully occupied in terms of wastewater production and typically generate average daily flows of approximately

150,000 gpd. It is noted that there is also significant diurnal peaking under all of these flow scenarios.

Both diurnal and seasonal peaking pose a significant problem for consistent treatment at the

WWTP, particularly with respect to the existing denitrifying filter. The average design flow for the denitrifying filter is approximately 28 gpm (40,000 gpd) and the maximum design flow is

70 gpm (100,000 gpd) (Kennedy/Jenks Contract Specifications, August 2013). When the flow rate exceeds this maximum capacity, the water flows through the denitrifying filter faster than it can be treated, reducing the filter’s treatment efficiency. It is also noted that flows in excess of

70 gpm tend to cause blowout of the denitrifying filter, making it unfeasible from a hydraulic perspective.

High flows (in excess of 70 gpm) put the plant at risk of exceeding the total nitrogen limit prescribed under the WDR. In a technical paper published by the Water Environmental Federation

(2010) focusing on modeling the effects of changing hydraulic and loading rates to an upflow continuous backwash denitrifying filter, modeling results show that as the flow rate increases toward the design maximum flow rate, the denitrification potential in the filter drops until the influent and effluent total nitrogen concentrations are the same. There is a concern at the Main

Garrison WWTP that as the flows into the plant increase during annual training events and eventually exceed the maximum design flow rate of the filter, the denitrification potential of the

Main Garrison Wastewater Treatment Plant Page 9 filter could drop significantly, resulting in effluent total nitrogen that could exceed the WDR limits.

This supports the concept that as the flow rate at the Main Garrison WWTP increases toward, and exceeds, the maximum design flow rate, the denitrification potential drops significantly. In fact, based on observations made during the filter operation in 2017, it was noted that the filter has a consistently high treatment efficiency when a steady flow of about 30 gpm (close to the average design flow) is maintained. Flows above 30 gpm or frequently varying flows tend to cause a disruption in the filter performance, reduce the treatment efficiency, and increase the probability of exceeding the total nitrogen and/or BOD discharge limits.

Even assuming the overall filter capacity is not exceeded, the rapid increase of loading to the denitrifying filter during annual training events is still problematic. As a biological system, the denitrifying filter operates most efficiently with constant flows and loads. When the flows rapidly increase, the nitrate loading is higher than the filter can effectively treat, causing a shock loading.

The filter can slowly adjust to the higher nitrate loading but it may take several days, and in that time, discharge from the WWTP is prone to exceed the total nitrogen effluent limit prescribed in the WDR. This problem is exacerbated by the long periods of very low flow (requiring recirculation) experienced at the WWTP.

WSC used the Hydromantis GPS-X wastewater treatment process modeling software to model the performance of the existing denitrifying filter using the anticipated flow rates and water quality.

Based on the modeling results, it is evident that as the flow rate rapidly increases, the effluent total nitrogen would also spike. The effluent total nitrogen would slowly decrease after the initial shock as the denitrifying filter adjusts to the higher loading but could take up to 10 to 15 days to reduce total nitrogen below the effluent limit.

1.3.3 System Automation

The design intent for the new denitrifying filter was such that the influent flow rate through the filter would be automatically adjusted based on water level in the secondary effluent pump station

(flow passing through the WWTP) and real-time measurements of nitrite, nitrate, and ammonia.

In practice, the need for a near-constant recirculation flow of approximately 30 gpm and the lack of connectivity between the nitrogen analyzer and the filter controls means that automatic operation of the system is currently impractical.

1.3.4 Aging Infrastructure and System Leaks

Prior to implementation of Phase 1, the majority of the WWTP improvements dated back to the

1950s construction. The major features (clarifiers, trickling filters, the Main Wet Well, the

Diversion Chamber) were constructed using reinforced concrete. System piping also appears to be reinforced concrete pipe below ground and typically steel above ground. Based on observations made during construction, most of the subsurface piping appears to be encased in concrete.

Manholes are observed to be constructed using brick.

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As construction was nearing completion for Phase 1, the contractor began hydraulic testing of the

Secondary Clarifier and Trickling Filter 2. Unsurprisingly, subsurface elements that have been in place for over 60 years were found to be cracked and/or leaking in several locations. Cracks in the piping, dislocations at the ends of pipes, and improperly sealed joints were all observed during these inspections. The construction of Phase 1 was modified to include the resealing of joints and provide localized patches where cracks or damage were identified via video survey. The contract modification also included the rehabilitation of several valves and gates that had rusted or otherwise become locked in a fixed position. In spite of these fixes, it became apparent at the time of commissioning the WWTP Phase 1 rehabilitation that a significant quantity of water was still being lost beneath the Secondary Clarifier, either from the pipes connecting the clarifier to

Trickling Filter 2 and/or the Diversion Chamber or along the joint between the Secondary Clarifier sidewall and base. Significant water loss was also observed in the subsurface piping between the main wet well pump and Trickling Filter 2. To date, it has not been possible to commission the rehabilitated secondary treatment equipment in accordance with Phase 1 objectives because of these continued leaks. It is noted that many of the subsurface lines were inspected via video logging during construction and no obvious major cracks or pipe dislocations were noted. This means that potential leaks were missed during the inspection or that the leaks were likely caused during or after construction, specifically the reloading of equipment left dormant for many years.

A site plan with a summary of the video logging conducted by the contractor during the Phase 1 upgrades is provided in Appendix B. In 2024, WCG performed additional video logging and a hydrostatic test of the subsurface connection piping between the Secondary Clarifier and the

Diversion Chamber and Trickling Filter 2. The results of the test indicated no apparent leaks within the Secondary Clarifier along the joint between the sidewall and base. However, significant water loss was observed from the influent pipes from the Diversion Chamber and Trickling Filter

2.

1.3.5 Lack of Equalization

In contrast to most modern wastewater treatment facilities, the Camp Roberts WWTP does not have system equalization anywhere in the treatment process. In this context, system equalization would constitute a storage tank or storage pond that could hold wastewater during peak flows and release it back at a rate suited to the treatment equipment. Given the relatively uncommon flow profile of the plant (diurnal and seasonal peaking), the lack of equalization is a fundamental flaw in the current wastewater treatment strategy that relies heavily on biological processes.

At any time that influent flows exceed the maximum hydraulic rate of the denitrifying filter, the plant effluent will be a mixture of partially treated wastewater (overflowing from the secondary effluent pump station) and fully treated wastewater (from the denitrifying filter). During these periods there is a high probability that the WWTP will discharge effluent out of compliance with the WDR limits for BOD, total nitrogen, or both.

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1.4 REEVALUATION OF THREE-PHASE PLAN

Phase 1 of construction at the WWTP was substantially completed in June 2016. Prior to proceeding with a detailed design for Phase 2 per the Kennedy/Jenks plan, the CA ARNG decided to reevaluate treatment options for the WWTP. This decision was made in consideration of the issues described above, particularly the suitability of the denitrifying filter installed during Phase 1.

1.5 ENGINEERING FEASIBILITY STUDY REEVALUATION

Reevaluation of the treatment alternatives took the form of a feasibility study performed by Avocet and WSC and documented in a Design Evaluation Report (Avocet, December 2017). The objective of the feasibility study was to evaluate all available treatment alternatives for wastewater at Camp Roberts WWTP and select a preferred alternative. Prior to the feasibility study, Avocet and WSC identified seven potential treatment alternatives for consideration:

• Alternative 1 - Original Phase 2 Upgrades

• Alternative 1a - Original Phase 2 Upgrades and Blend with Groundwater to

Accommodate Low Flows

• Alternative 2 - Smaller Additional Denitrifying Filter

• Alternative 3 - Downflow Denitrifying filter to Accommodate Low Flows

• Alternative 4 - Oxidation Ditch

• Alternative 5 - Membrane Bioreactor (MBR) Package Plant

• Alternative 6 - Sequencing Batch Reactor Field Constructed Plant

To thoroughly assess each of the alternatives, Avocet, WSC, and the CA ARNG established and developed a system of weighted screening criteria with which to rank the proposed technologies.

The final criteria and weighting are summarized in the table below.

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Screening Criteria Weighting

(1 = min, 5 = max)

Construction Cost 5

Life Cycle Costs 5

Ability to Consistently Produce Compliant Effluent 4

Incorporates Existing Facilities 4

Project Delivery 2

System Robustness 3

Permitting Uncertainty/Complexity 1

Ability to Handle Anticipated High and Low Flows 2

Ability to Meet Future Permit Revisions 1

Effluent Quality for Reuse 4

Avocet consulted informally with CA ARNG Facilities and Engineering personnel throughout the design evaluation and feasibility study for the WWTP. When development of the treatment alternatives was completed, Avocet held two design briefings with the CA ARNG to summarize the design challenges and refine the screening criteria and weighting. Avocet engineers met with

SFC Herbert Kendall, LTC Craig Sandman, and MAJ Lorren Deakin in May 2017. The three preferred alternatives were presented to BG Frank Emanuel, the Director of Facilities and

Engineering, in a briefing on June 28, 2017. The consensus of this briefing was that the highest ranked alternative, the MBR package plant, was the final preferred alternative and that conceptual design for this alternative should proceed as soon as practical.

Final selection of the MBR system was the recommendation of Avocet and WSC under the criteria and weighting outlined in the Design Evaluation Report (Avocet, December 2017).

1.6 PRELIMINARY DESIGN REPORT

Avocet prepared a Preliminary Design Report that outlined a conceptual design for the selected alternative described above (Avocet, March 23, 2018). In brief, the main components of the conceptual design were to include the following:

• An MBR wastewater treatment package plant configured to operate between zero and 250,000 gpd.

• A 60,000-gallon wastewater equalization tank regulating flow to the MBR.

• A (minimum) 840,000-gallon permeate retention pond (or ponds) to regulate noncompliant effluent.

• A sludge handling system with holding tank and solids press.

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• Reconfiguration of the existing infrastructure to convey wastewater through the above-listed components.

To support the conceptual design, Avocet implemented engineering studies to verify existing influent wastewater volume and quality. Specifically, Avocet collected supplemental wastewater flow volume data and supplemental influent water quality data. In brief, the results of the flow study confirmed the extreme variability in wastewater flows, ranging from near-zero conditions to peak flows exceeding 200,000 gpd during training events. The results of the additional influent analytical data collection provided a set of comprehensive, recent, representative data to be used in the design of the MBR package plant. Further details regarding the results of these studies are included in the Preliminary Design Report (Avocet, March 23, 2018).

1.7 DESIGN EVALUATION

Following the preparation and submission of the Preliminary Design Report and accompanying design drawings in 2018, which detailed the 35 percent conceptual design, the continuation of the design of the proposed WWTP upgrades was put on hold due to an uncertainty in contracting mechanisms. The project was revived in 2023 and Avocet subsequently prepared a Design

Evaluation Report to assess advancements in municipal wastewater treatment technologies, regulatory code and design guidance changes, and estimated construction cost changes since the development of the 35 percent conceptual design in 2018. The result of the evaluation generated a weighted score for each alternative based on costs, treatment effectiveness, existing infrastructure reuse, quickness of construction, permitting uncertainty, ability to accommodate anticipated flow range, and possibility of beneficial effluent reuse, with the MBR package plant alternative receiving the highest weighted score and remaining as the preferred alternative (Avocet, August 10, 2023).

1.8 REPORT ORGANIZATION

This section serves as an introduction to the report and provides relevant background information.

Section 2.0 summarizes the basis of design and regulatory requirements. Section 3.0 describes the principal elements of the design.

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2.0 BASIS OF DESIGN

The design of the WWTP upgrades has been performed using a set of criteria developed from permit requirements, historical wastewater information, and the engineering studies described in the Preliminary Design Report (Avocet, March 23, 2018). The design criteria can be summarized into three categories: influent wastewater quality, influent wastewater volume, and plant effluent limits.

2.1 INFLUENT WASTEWATER QUALITY

As discussed previously, the water quality parameters likely to cause effluent non-compliance are

BOD, TSS and total nitrogen. Substantial WWTP influent analytical data exist for these parameters. The basis of design parameters were developed from historical average BOD, TSS, and total nitrogen influent concentrations and maximum observed concentrations. The design influent concentrations developed by Kennedy/Jenks in their Preliminary Design Services for

Main Garrison Wastewater Treatment were confirmed as suitable design parameters for the proposed upgrades. This confirmation was based on the influent water quality monitoring and sampling conducted by Avocet between June and September 2017 as described in the Preliminary

Design Report.

The following table summarizes the influent wastewater quality data used in the proposed design.

The monthly maximum concentrations typically correspond to increased flow scenarios (Weekend

Flow, Annual Training Flow).

Parameter

Average

Concentration

(mg/L)

Monthly Maximum

Concentration

(mg/L)

BOD5 120 320

TSS 180 375

Total Nitrogen (as N) 45 80

Ammonia 25 65

2.2 EXPECTED WASTEWATER VOLUME

The variation of wastewater flows received at the Camp Roberts Main Garrison WWTP is greater than that experienced at a typical treatment facility. The camp population fluctuates substantially depending on the level of training activity taking place at a given time. Although the diurnal peak hour factor varies significantly, it has been modeled as up to 3.5 for the nonemergency flows at the WWTP. This peaking factor was determined through an analysis of flow data from June through August 2017 and through consideration of the unusual wastewater conditions at Camp

Roberts. As a military training facility, concentrated demand of washing and cooking facilities at a specific time of day can cause an atypically high concentration of wastewater during these periods. Although it is not anticipated that the WWTP will experience a peak hour factor as high

Main Garrison Wastewater Treatment Plant Page 15 as 3.5, this value has been used as a “stress-test” for the system to ensure that sufficient equalization capacity is provided. As such, it is considered extremely conservative for the design

(Kennedy/Jenks typically used a factor of 2.5 in its Evaluation Design Repair of Wastewater

Treatment Plants at Camp Roberts, California, March 1, 2012, a value which is itself already high).

The different potential flow scenarios that are considered in the proposed design are summarized in the table below. A brief explanation of each potential flow scenario is summarized in this section.

Flow Scenario

Average

Daily Flow

(gpd)

Peak

Hour Flow

(gpd)

Zero Flow 0 0

Baseline Flow 5,000 17,500

Weekend Flow 40,0001 105,000

Annual Training Flow 150,000 525,000

Maximum Design Flow 250,000 875,000

Emergency Flow2 2,000,000 5,000,000

2.2.1 Zero Flow

The proposed design considers how a period with no influent could be handled by the system.

Although unlikely to be a frequent event, it may be advantageous to the CA ARNG to suspend all flow to the WWTP to complete repairs, maintenance, etc.

2.2.2 Baseline Flow

The typical weekday flow when no training event is in progress is considered as the Baseline Flow.

It represents the wastewater volume generated by the Camp Roberts permanent staff and from the main dining facility, although it is noted that the baseline flow can vary depending on the time of year and staff levels at the facility. The baseline flow for the proposed design has been modeled with an average daily flow of 5,000 gpd and a peak hour flow of 17,500 gpd.

The chart on the following page shows the daily average flows during March and April of 2016 when no large-scale training was taking place at Camp Roberts. The flow was recorded using the dedicated headworks flow meter at the WWTP. It is noted that this flow meter has a tendency to underestimate flows at the lower end of its range. This should be considered a degree of

1 Average daily flow was adjusted to 40,000 gpd while the corresponding peak hour flow was calculated based on an earlier estimate of 30,000 gpd. These values are not direct constraints on system design and will be adjusted for consistency in the detailed design phase.

2 The Emergency Flow scenario assumes that existing traditional treatment equipment would be returned to service.

Main Garrison Wastewater Treatment Plant Page 16 conservatism in the proposed design, as the baseline flow essentially defines the lowest expected flows to the plant.

2.2.3 Weekend Flow

The flow generated during a normal weekend training event is considered as the Weekend Flow.

It represents the wastewater flow generated by weekend training activities at the post. The weekend flow for the proposed design has been modeled with an average daily flow of 40,000 gpd and a peak hour flow of 105,000 gpd. The instances of increased flow in the chart above typically correspond to weekend training events. As can be seen from this example period, there remains significant variation in the volume of wastewater generated during any given weekend training event.

2.2.4 Annual Training Flow

At present, Camp Roberts accommodates up to three large-scale CA ARNG training events on post per year. During these training events, the camp population significantly increases and, consequently, wastewater flow from barracks and mess halls is also increased. The annual training flow for the proposed design has been modeled with an average daily flow of 150,000 gpd and a peak hour flow of 525,000 gpd. It was assumed that the maximum duration of increased flow associated with an annual training event was three weeks.

20,000

40,000

60,000

80,000

100,000

In fl u e n t

W a st e w a te r

(g a ll o n s)

Date

Camp Roberts Occupancy and Wastewater Flows

March - April 2016

Headworks Flow

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The chart shown below focuses on the 20-day period between July 7 and July 27, 2017, during which time Camp Roberts was accommodating the maximum allowable troop load (or close to it).

As described in Section 2.1, the flow was recorded using a dedicated flow meter installed directly upstream of the plant. Calibration of the temporary meter was tested and verified by a flow meter technician prior to and following its use. The chart includes a trendline at 150,000 gallons, representing the median flow rate as recorded by the temporary flow meter throughout the annual training period.

2.2.5 Maximum Design Flow

The maximum design flow is the theoretical flow resulting from permanent maximum occupancy of the Camp Roberts training facility. Based on information provided by the CA ARNG, there are approximately 4,800 barracks spaces available at the camp. Sizing of treatment equipment at the

WWTP assumes that permanent full occupancy of the 4,800 beds, along with a corresponding increase in mess hall facilities, represents the maximum sustained volume of wastewater the plant could expect in a nonemergency scenario. Using the data incorporated in the graphs above, Avocet observed that the maximum observed flows were at or around 200,000 gpd. The maximum design flow incorporates a 1.25 factor of safety and has been modeled with a sustained average daily flow of 250,000 gpd and a peak hour flow of 875,000 gpd.

40000

80000

120000

160000

200000

240000

280000

1,000

2,000

3,000

4,000

5,000

6,000

7,000

07/02/17 07/07/17 07/12/17 07/17/17 07/22/17 07/27/17

In fl u e n t

W a st e w a te r

(g a ll o n s)

O cc u p a n cy p e o p le

Date

Camp Roberts Occupancy and Wastewater Flows

Annual Training Event

Occupancy

Flowmeter

Main Garrison Wastewater Treatment Plant Page 18

2.2.6 Emergency Flow

Under the existing WDR, an allowance for emergency flow is made when Camp Roberts is

“occupied by people displaced in response to natural disasters or other emergency conditions.”

The allowable average daily flow (when annualized) is 2,000,000 gpd for a period of 90 days. The emergency peak hour flow has been assumed to be 5,000,000 gpd.

The proposed upgrades to the WWTP have been designed to accommodate the zero flow, baseline flow, weekend flow, annual training flow, and the maximum design flow scenarios. In addition to operating under these flow scenarios, the proposed design also considers the time needed for the biological treatment processes to adjust from baseline flow to annual training flow. Wastewater and permeate equalization ponds have been sized accordingly to allow the treatment equipment to adjust to higher flow rates.

The design also provides hydraulic capacity for continuous operation under the emergency flow scenario. In this scenario the existing traditional treatment equipment (Primary Clarifier and

Trickling Filter 1) could be utilized to handle the extreme flow.

2.3 REGULATORY REQUIREMENTS

In 2014, in response to a Report of Waste Discharge prepared by Kennedy/Jenks, the CCRWQCB issued new WDR Order No. R3-2014-0046 for Camp Roberts. The 2014 WDR included new limits for three constituents: BOD, TSS, and total nitrogen, as shown in the table below. Total nitrogen is considered to be the sum of organic nitrogen, ammonia, nitrite, and nitrate.

Parameter Value

(mg/L)

Biochemical Oxygen Demand (BOD) 30

Total Suspended Solids (TSS) 30

Total Nitrogen (as N) 10

WCG concurs with previous assessments that these parameters govern design of the system to achieve compliance. The complete list of effluent limits can be found in the WDR and is reproduced in Section 1.1.2.

The 2020 WDRs include the following effluent limitations, though more stringent, site-specific effluent limits may be imposed upon incorporation of the WWTP into the new WDRs and issuance of a new monitoring reporting program.

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Parameter Units 30-Day Average 7-Day Average Sample

Maximum

BOD mg/L 30 45 N/A

TSS mg/L 30 45 N/A

Settleable Solids mL/L 0.1 0.3 0.5 pH N/A 6.5 – 8.4 N/A N/A

In addition to the effluent limitations above, the 2020 WDRs include effluent limits for total dissolved solids (TDS), chloride, sulfate, boron, sodium, and total nitrogen based on the discharger’s groundwater basin and sub-basin.