Technical Memorandum CONDITION ASSESSMENT AND … · Table 5 Alternative 1 - Pros & Cons 14 Table 6 Alternative 2 Summary 15 Table 7 Alternative 2 - Pros & Cons 16 Table 8 Alternative

Texas Board of Professional Engineers No. F-882

El Paso Water Roberto Bustamante Wastewater Treatment Plant Headworks Improvements

Technical Memorandum CONDITION ASSESSMENT AND ALTERNATIVES EVALUATION FINAL | July 2019

El Paso Water Roberto Bustamante Wastewater Treatment Plant Headworks

Improvements

Technical Memorandum

CONDITION ASSESSMENT AND ALTERNATIVES EVALUATION

FINAL | July 2019

TM | ROBERTO BUSTAMANTE WWTP HEADWORKS IMPROVEMENTS | EL PASO WATER

FINAL | JULY 2019 | ii

pw:\\Carollo\Documents\Client/TX/El Paso Water/11292A10/Deliverables\TM_Condition Assessment and Alternatives Evaluation

Contents Section 1 - Introduction 1

1.1 Background 1

Section 2 - Existing Facilities Condition Assessment 2

2.1 Influent Pump Stations (IPS) 2

2.1.1 Influent Pump Station #1 (IPS #1) 2

2.1.2 Influent Pump Station (IPS #2) 2

2.1.3 Screening Facility 4

2.1.4 Grit Removal and Handling Facility 5

2.1.5 Electrical Building 7

2.1.6 Odor Control 8

Section 3 - Design Considerations 11

3.1 Flows and Expansion Requirements 11

3.1.1 Structural Considerations 11

Section 4 - Alternatives Evaluation 12

4.1 Influent Pump Station 12

4.1.1 Alternative 1 12



4.2 Screening Facility 18



4.3 Grit Removal and Handling Facilities 21



4.4 Electrical Building 28

4.5 Odor Control 28

4.5.1 Odor Control Airflow 29

4.5.2 Biotrickling Filters for Odor Control 30

4.5.3 Odor Control Recommendations 31

4.6 Life-Cycle Cost Analysis 31


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4.7 Selected Alternatives 31

Section 5 - Construction Sequencing 33

Appendices Appendix A Cost Estimates for Design Alternatives

Appendix B Life Cycle Cost Estimates for Design Alternatives

Tables Table 1 Existing Odor Control Field Measurements – June 10, 2019 9

Table 2 Additional Hydrogen Sulfide Readings – December 20, 2018 9

Table 3 RBWWTP Headworks Existing and Expansion Flow Summary 11

Table 4 Alternative 1 Summary 12

Table 5 Alternative 1 - Pros & Cons 14










Table 15 Odor Control Airflow 30

Table 16 Total Present-Worth of Each Alternative 31

Table 17 RBWWTP Headworks Selected Alternatives 32


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Figures Figure 1 Existing Site Layout 1

Figure 2 Existing Grit Chamber and Pump Room 5

Figure 3 Proposed IPS #1 Upgrades 13

Figure 4 Proposed IPS #2 Upgrades 13

Figure 5 Proposed IPS #3 for Alternative 2 16

Figure 6 Proposed IPS #3 for Alternative 3 17

Figure 7 Proposed Rehabilitated and Expanded Screening Facility for Alternative 1 19

Figure 8 Proposed New Screening Facility for Alternative 2 20

Figure 9 Existing Grit Removal Facilities 22

Figure 10 Proposed Grit Removal Facilities 23

Figure 11 Potential Bypass Pipe 25

Figure 12 Proposed New Grit Facilities 26

Figure 13 270 Degree Vortex Design Grit Chamber 27


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Abbreviations AADF Annual Average Daily Flow

AWPF Advanced Water Purification Facility

Carollo Carollo Engineers, Inc.

CFD Computation Fluid Dynamics

cfm cubic feet per minute

CMAR Construction Manager at Risk

EPEC El Paso Electric

EPWater El Paso Water

fpm foot per minute

FRP fiberglass reinforced plastic

ft feet

HI Hydraulic Institute

IPS influent pump station

µg/L micrograms per liter

JRWTP Jonathan Rogers Water Treatment Plant

M million

MCC Motor Control Center

mg/L milligrams per liter

mgd million gallons per day

MW megawatts

NFPA National Fire Protection Association

O&M Operating and Maintenance

PER Preliminary Engineering Report

pH potential hydrogen

ppm parts per million

PVC polyvinyl chloride

RBWWTP Roberto Bustamante Wastewater Treatment Plant

SG Switchgear

T Transformer

TEFC Totally Enclosed, Fan-Cooled

VFD Variable Frequency Drive

WERF Water Environment Research Foundation

WWTP wastewater treatment plant


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Section 1

INTRODUCTION

1.1 Background

El Paso Water (EPWater) plans to improve the existing headworks facility at the Roberto Bustamante Wastewater Treatment Plant (RBWWTP). EPWater also plans to expand the entire RBWWTP to accommodate growth within the plant's service area. The RBWWTP was originally constructed in 1988 and the headworks facilities were later modified in 2001. The improved headworks facility must address operational issues that currently exist at the plant and account for the anticipated overall expansion of the plant.

Carollo Engineers, Inc. (Carollo) has performed a condition assessment and alternative evaluation for the headworks facilities at the RBWWTP. The headworks facility consists of the influent pump station, screening facilities, grit facilities (See Figure 1) and associated odor control systems. Carollo conducted multiple inspections and coordinated with RBWWTP plant and operations staff to assess the condition of the facilities as well as identify features and needs at each facility. The results of the condition assessment and alternative evaluation were presented to EPWater staff and upper management during two workshop events held on May 1, 2019. A follow up meeting was held on May 28, 2019 to discuss and finalize an alternative to progress into design. The results of the condition assessment, alternative evaluation and the chosen alternative are documented in this technical memorandum.

Figure 1 Existing Site Layout



Section 2

EXISTING FACILITIES CONDITION ASSESSMENT

2.1 Influent Pump Stations (IPS)

The RBWWTP was originally constructed with an influent pump station (IPS) that consisted of eight submersible pumps in a wet well which will be referred to throughout this technical memorandum as IPS #1. In 2001, a second IPS was constructed which will be referred to as IPS #2 in this technical memorandum. IPS #2 consequently became the IPS at RBWWTP and IPS #1 was modified to serve as a return flows pump station and a septage receiving station. Both IPS #1 and IPS #2 were inspected as part of this condition assessment.

2.1.1 Influent Pump Station #1 (IPS #1)

Visual assessments of IPS #1 were conducted on November 27, 2018 and December 19, 2018. IPS #1 was operational during both site visits. A Go-Pro camera was lowered into the wet well in order to visually observe the interior of the wet well. The visual assessment indicated that IPS #1 is in fair condition. The portion of concrete visible during the assessment appeared to be in good condition. The wet well has a t-lock liner system that was installed as part of the 2001 modification. The seal strips along the liner edges were not present at the time of the inspection. It is unknown if the seal strips were installed during construction or if they have fallen off. It is Carollo's understanding that EPWater intends to decommission this lift station entirely. If IPS #1 does continue to operate, the liner system should be repaired.

2.1.2 Influent Pump Station (IPS #2)

Visual assessments of IPS #2 were conducted on November 27, 2018, December 19, 2018 and February 26, 2018. The first two assessments were conducted by lowering a Go-Pro camera into the structure from the ground surface without entering the wet well. It was not possible to enter the structure because hydrogen sulfide concentrations inside the wet well exceeded 400 parts per million (ppm). The third assessment was conducted while the emergency rehabilitation construction project was underway and a temporary odor control system was put in place that reduced hydrogen sulfide concentration to a safe level of 1 ppm. During the third assessment, a structural engineer certified in confined space entry was able to enter the structure and make visual observations. The following observations were made:

• The exterior face of the concrete masonry unit walls appeared to be in good condition. No corrosion or visible cracks were observed.

• The interior face of the concrete masonry unit walls at the entry way into the wet well of the headworks are experiencing corrosion due to exposure to hydrogen sulfide gases. The existing coating on the concrete masonry unit walls are delaminated and non-existent in some areas. At the doorway and at the bottom portion of the interior face of the concrete masonry walls, severe corrosion and delamination of the coating was visible.



• The reinforced concrete floor slab interior landing at the doorway was also experiencing corrosion due to hydrogen sulfide gases. The top portion of the slab has extreme aggregate exposure as a result of the corrosion but there was no visible reinforcing bars exposed.

• The existing coating on the underside of the precast double tee roof panels are delaminating from exposure to hydrogen sulfide gases.

• The concrete beams at the north east, right below the access hatch and above the influent gate of the wet well is extremely corroded with severe aggregate exposure. Spalled concrete and corroded reinforcing bar was visible in one of the beams from exposure to hydrogen sulfide gases.

• All metal conduits, metal electrical supports or hangers, metal pump shafts, metal pipe supports, metal brackets and anchors are severely corroded in the wet well. The stem of the influent gate and accompanying supports including but not limited to concrete and metal brackets are corroding from the hydrogen sulfide environment.

• The existing coating on the reinforced concrete walls, reinforced concrete beams, and reinforced concrete walkway slabs in the wet well are delaminated from exposure to hydrogen sulfide gases.

• All the reinforced concrete stairways providing access into the wet well have severe aggregate exposure and are very brittle and visibly flaking off due to the hydrogen sulfide environment.

• Visible extreme aggregate exposure was noted at the top face of the reinforced concrete walkway slab in the wet well. There were very few minor cracks at the top face of the reinforced concrete walkway slab. The bottom face of the reinforced concrete walkway slab in the wet well appear to be in good condition due to protection by the existing coating.

Given the hydrogen sulfide environment and the corrosion that was observed, as noted above, the following recommendations are proposed:

• The interior face of the concrete masonry unit walls should be cleaned of all laitance and existing coating. A repair mortar and hydrogen sulfide resistant coating should then be applied to the interior face of the walls.

• The reinforced concrete floor slab interior landings should be cleaned of all laitance and a repair mortar and hydrogen sulfide resistant coating applied.

• The underside of all precast double tees at the roof should be cleaned of all laitance and coating prior to the application of a hydrogen sulfide resistant coating.

• The concrete beams at the north east, right below the access hatch and above the influent gate of the wet well should be cleaned and prepared to the appropriate surface profile. A corrosion resistant bonding agent should be applied to the exposed reinforcing and a repair mortar applied to the spalled areas of the beams. The repair mortar should also be applied to the areas of extreme aggregate exposure. The entire beam should be coated with a hydrogen sulfide resistant coating.

• All corroded metal conduits, metal electrical supports or hangers, metal pump shafts, metal pipe supports, metal brackets, anchors, stem of the influent gate and accompanying supports should be coated with a hydrogen sulfide resistant coating where these could be reused or replaced entirely with hydrogen sulfide resistant metals or materials.



• The existing coating on the reinforced concrete walls, reinforced concrete beams and reinforced concrete walkway slabs in the wet well should be removed, the surfaces prepared, and a hydrogen sulfide resistant coating applied.

• All the reinforced concrete stairways should be demolished. The severe aggregate exposure, the brittle nature and visible flaking of the existing concrete will make it extremely difficult to achieve a good surface profile to apply a repair mortar and restore the structural strength and integrity of the stairways. Corrosion resistant metal stairs could be installed should this be desired. If this method is elected, the reinforced concrete landings should be repaired similar to the repair procedure stated earlier for the reinforced concrete floor slab interior landings. If this method is not elected then the reinforced concrete landings could be demolished if needed. Although not recommended, the following can be tried as a short term repair option. Measures can be taken to achieve a good surface profile and substrate prior to applying a repair mortar to restore the structural strength and integrity of the stairways. If this short term repair option is elected prior to a long term repair option, continuous inspection is recommended following the implementation of the short term option.

• The top face of the reinforced concrete walkway slab in the wet well should be cleaned and prepared to the appropriate surface profile. Any visible cracks should be repaired. A repair mortar and hydrogen sulfide resistant coating should be applied following any crack repairs.

Initial interviews conducted with plant operations personnel throughout the evaluation stage indicated that the pumps in IPS #2 have not required excessive repair or maintenance activities. They indicated that the pumps are 17 years old and have been repaired on three occasions. However, routine maintenance of these pumps has been challenging due to the isolation gates in the wet well-being either inaccessible, due to the hazardous environment of the wet well, or inoperable.

During a meeting held on May 28, 2019 to discuss and finalize an alternative to progress into the design stage, plant operators informed Carollo that they have been experiencing issues with the pumps since the emergency rehabilitation project completed initial maintenance activities on all pumps. The discharge cones were removed, the wet well was cleaned, and the pumps were cleaned. The pumps now provide significantly less flow than they did before the maintenance activities were completed.

The main issue raised by operations staff about IPS #2 is the inability to properly maintain the facility because of the single wet well configuration which does not allow for regular shutdown and maintenance activities. Additionally, plant operators reported that the main isolation gate to the wet well is difficult to operate. Once this gate is closed, operators have an approximate 2-hour window to perform any maintenance activities before the sewer system begins to surcharge.

2.1.3 Screening Facility

The existing screening facility consists of a total of five screen channels. Screens are installed in four of the channels. The fifth channel was meant for the installation of an additional screen in the future. All screenings material are transported via a shaftless screw conveyor to a screenings compactor and then discharged to the screenings hopper.



The existing screening facility at the RBWWTP was also included in the condition assessment conducted by Carollo. During the visual assessment conducted on December 19, 2018, the visible portions of concrete and lining of the screening structure was found to be in good condition. However, throughout the evaluation stage while conducting interviews with the operations personnel, operational issues were brought to light. Based on discussions with plant personnel, operational issues include water freezing in the open spaces of the screens that are not in use during low flow conditions in the winter months and no compactor redundancy.

Overall, the screening facility was determined to be in good condition.

2.1.4 Grit Removal and Handling Facility

The original RBWWTP built in 1988 had three grit chambers, two small grit pump rooms and three pre-aeration basins. The grit facilities and pre-aeration basins were modified in 2001. These modifications included abandoning the three original grit chambers and two pump rooms. Pre-aeration basin #1 was abandoned in-place with all mechanical and electrical equipment removed. Pre-aeration basin #2 was converted into a grit pump room and pre-aeration basin #3 was converted into the current grit chamber. An excerpt from the 2001 record drawings highlights these modifications (See Figure 2).

Figure 2 Existing Grit Chamber and Pump Room



The existing grit chamber is a rectangular aerated horizontal flow grit chamber. The flow enters through an influent box on the east side of the chamber and is directed down and into the chamber. The flow then goes across the chamber in a cyclical manner depositing grit and flowing out the top of the opposite side of the chamber and into the effluent channel. The chamber consists of five separate hoppers with grit pumps. The floor is sloped towards the hoppers to assist in grit movement to the pump suction pipe.

The grit removed by the pumps is sent to the grit dewatering room. This room is located above the abandoned grit and pump room. Currently in use are three grit classifiers (WEMCO Hydrogritters), two of which appear to be recently coated. The grit is dewatered and discharged to roll off dumpsters via a grit hopper.

Visual assessments of the existing grit handling facility at the RBWWTP were conducted on November 27, 2018 and December 19, 2018. The initial assessment consisted of lowering a Go-Pro camera into one accessible hatch above the aerated grit chamber. Obvious structural damage was apparent when the video was reviewed. Because of the obvious structural damage, Carollo requested that the remaining hatches be opened and additional investigations take place. Carollo also requested that the area be restricted from access for safety. The second assessment was conducted by lowering a Go-Pro camera into the structure from all of the roof access hatches without entering the structure. It was not possible to enter the structure because it was operational during the assessment. The following observations were made during the assessment:

• The outside of the exterior reinforced concrete walls (not exposed to water) appeared to be in good condition.

• Several tanks, piping and equipment are supported on the reinforced concrete roof. • The reinforced concrete roof is experiencing corrosion from the constant draining/leaks

of liquids from pipes. • The interior surfaces of the exposed reinforced concrete walls above the water line and

the underside of the reinforced concrete roof slab have a t-lock liner system but is deteriorating, especially at the roof access hatch openings.

• The top section of an interior wall at the inlet channel section above the water line is completely corroded resulting in complete section loss of the reinforced concrete wall leaving remnants of very minimal, to no, reinforcing present.

• The exterior wall at the inlet channel section above the water line has severe exposed aggregate with visible corroding reinforcing. At a roof access hatch at this location the supporting reinforced concrete beam and t-lock liner are completely deteriorated with section loss.

• The interior columns in the facility that are exposed above the water line are visibly corroding and the connection to the underside of the reinforced concrete roof is corroding.

Given the corrosion and deterioration that was observed, as noted above, the following recommendations are proposed:

• The leaks/drains from the pipes at the reinforced concrete slab need to be prevented by ensuring adequate seals.

• Any loads that are not required at the reinforced concrete roof need to be removed.



• The entire facility will need to be drained and inspected to identify any areas of concern below the water line that were not visible during this assessment. These areas will need to be evaluated to see if any additional repairs are needed.

• Repair methods to replace the section loss of structural members at all walls and beams need to be evaluated and restored. Such repair methods could include the use of repair concrete, use of stainless steel members or the use of carbon fiber wrap/fiber reinforced cementitious matrix.

• At all walls where aggregate exposure and corroded reinforcing were observed, repair methods ranging from the use of a repair mortar, coating, or the use of carbon fiber wrap/fiber reinforced cementitious matrix should be evaluated.

• The interior columns will need to be evaluated to determine if further corrosion resistant coating should be applied or if the columns need to be replaced.

• Following the removal of any existing coating/liner, an appropriate coating will need to be applied on all interior surfaces or on all interior surfaces that previously had t-lock liner.

2.1.5 Electrical Building

A visual assessment of the electrical building and equipment was conducted on January 31, 2019. The following observations were made during this assessment:

• Switchgears SG-2, SG-3, and transformers T-9 and T-10 are located approximately 40 feet northeast of the headworks building. Strong smell of hydrogen sulfide was observed at this equipment. SG-3 is an abandoned switchgear and transformer T-9 has been recently replaced. Since hydrogen sulfide smell was observed in this area, there is a strong possibility that switchgear SG-2 and transformer T-10 are damaged and hence, should be inspected, tested and have preventative maintenance performed to ensure that they meet manufacturer’s specifications and industry standards for continued safe and proper operation. Replacement may be needed if the testing shows that the equipment can no longer perform as intended.

• Switchgears SG-4 and SG-5 in the headworks electrical room were damaged from presence of hydrogen sulfide. EPWater is currently having this switchgear replaced. MCC-15, MCC-16, VFDs, and panelboards in headworks electrical room seem to be in good condition from outside. However, considering the damage caused by the presence of hydrogen sulfide inside SG-4 and SG-5 which required their refurbishment, replacement or refurbishment of these MCCs, VFDs, and panels is recommended.

• Bare ends of incoming cables to switchgears SG-4 and SG-5 seemed to be clean and in good condition.

• Exposed conduits at the headworks building roof are severely corroded and should be replaced with PVC coated rigid steel or aluminum conduits.

• Based on the Preliminary Engineering Report (PER) prepared for the Advanced Water Purification Facility (AWPF): Both JRWTP and RBWWTP are supplied power from El Paso Electric Company

(EPEC) from a single overhead 13.8kV, 3-phase, 60 hertz service. This service is backed up by standby generators at each plant.

Maximum demand measured at the main meter is 10 megawatts (10MW). RBWWTP takes approximately 2 MW of total measured demand. JRWTP takes approximately 8 MW of total measured demand.



Expansion plans for JRWTP will add approximately 1.1 MW of loads, for a total main meter demand of 11.1 MW

Maximum capacity of the EPEC feeder, which provides power to both plants, is 17.2 MW.

Approximately 6.1 MW of line capacity on the existing EPEC service line could be available for rehab work and headworks improvements at RBWWTP (this will need to be confirmed with EPEC). This assumes that the AWPF will be supplied power from a separate EPEC service as recommended in the PER.

2.1.5.1 Headworks Electrical Assessment

During the electrical assessment the following additional observations were made around the headworks area:

• All exposed conduits to bar screen control panels are severely corroded. • Exposed spare conduits for future bar screen control panel are severely corroded. • Entrance to electrical room in influent building is partially blocked by the MCC. Need to

move MCC or provide new entrance • Exposed conduits to filter press control panels are in fair condition, however, initial signs

of corrosion are evident. All exposed conduits should be PVC coated rigid steel or aluminum.

• MCC 14 in influent electrical room and exposed conduits entering the MCC from the top are in poor condition with signs of severe rust at various areas.

• Bar screen motors are Totally Enclosed, Fan-Cooled (TEFC) type. These motors must be either explosion proof or listed for use in Class 1, Division 2 if supplied without internal temperature switches.

2.1.6 Odor Control

Existing odor control facilities at the existing headworks facility consist of two twelve-foot diameter wet mist chemical scrubbers manufactured by Calvert Environmental and installed in 1990. Both scrubbers pull air from a common foul air plenum, which is connected to the IPS #2, screening facility, grit facilities and return flow pump station. Each scrubber has a nominal 20,000 cfm fan supplying foul air for a total nominal airflow of 40,000 cfm.

At the Lower Valley Metering Station a supply and exhaust fan send air to a carbon adsorber. It is understood from plant personnel that the carbon in this unit is exhausted. At the junction box adjacent to the metering station, a temporary carbon adsorber is in place to exhaust air from the junction box and connecting interceptors and a permanent 8,000 cfm biotrickling filter is currently being installed.

2.1.6.1 Field Measurements

Field measurements were made on June 10, 2019 to measure airflow and hydrogen sulfide concentrations and are listed in Table 1 below.



Table 1 Existing Odor Control Field Measurements – June 10, 2019

Parameter Scrubber

No. 4 Scrubber

No. 5

Lower Valley Meter Station

Carbon Adsorber

Temporary Carbon Adsorber at Junction Box A

Hydrogen Sulfide Inlet Concentration

62 ppm 48 ppm 72 ppm Over 100 ppm

Hydrogen Sulfide Outlet Concentration

Not measured

48 ppm Not measured Not measured

Calculated Removal Efficiency

n/a 0 percent n/a n/a

Inlet Air Velocity(1) 120 fpm 236 fpm Not measured Not measured

Duct Diameter 48-in. 48-in. Not measured Not measured

Calculated Airflow 1,508 cfm 2,967 cfm n/a n/a Notes: (1) Location available for airflow measurement was immediately downstream of the fan and may not accurately represent

airflow.

Additional data was collected on December 20, 2018 and is shown in Table 2.

Table 2 Additional Hydrogen Sulfide Readings – December 20, 2018

Time Location H2S

Concentration, ppm

07:50 Scrubber No. 4 Inlet 48-69

07:55 Scrubber No. 5 Exhaust 38-48

08:02 Center grit chamber, west air pull point 111

08:05 Hatch near east end of active grit channel where

exposed rebar was observed 50-70

08:10 East suction header, after entry of all incoming

lines, prior to entry into plenum 19-20

08:15 Downstream end of elevated channel connecting

screen structure to grit chamber structure 90-112

08:20 West screen channel outlet, at downstream

isolation gate 80

08:25 Inlet channel – second screen from east 80

08:28 West pump discharge 180-220

08:30 Pump 3 discharge 180-260

08:40 Junction structure upstream of temporary odor

control system pull point; on 60 inch line 230

08:43 Inlet sampling port on FRP duct feeding

temporary carbon adsorber at Junction Box A 100 (varied)



2.1.6.2 Discussion

The existing chemical scrubbers were originally installed as mist scrubbers using sodium hypochlorite as the neutralizing chemicals. Compressed air was used to create finely dispersed droplets in the scrubber tower to neutralize hydrogen sulfide and other odorants.

Currently the compressed air system is not functioning and measured airflow appears to be substantially less than designed (although the duct layout prevents accurate airflow measurement). Based on spot measurements, it appears the system is not removing hydrogen sulfide.



Section 3

DESIGN CONSIDERATIONS

3.1 Flows and Expansion Requirements

Table 3 below summarizes the existing and anticipated expansion flows at the RBWWTP. The improved headworks facility will be designed to accommodate the anticipated expansion flows.

Table 3 RBWWTP Headworks Existing and Expansion Flow Summary

Flow Type Existing Anticipated Expansion

Permitted AADF (mgd) 39 51(1)

Permitted Peaking Factor 1.3 1.3 to 2.5

Permitted Peak 2-Hour Flow (mgd) 51 66 to 125

Current AADF (mgd) 29 NA

Current Peak 2-Hour Flow (mgd) 70 NA

Peak Dry Weather 2-Hour Flow (mgd) 37 NA Notes: (1) Assumes an AADF expansion of 12 mgd from the original 39 mgd will be required

3.1.1 Structural Considerations

3.1.1.1 Carbon Fiber Repair

On January 1, 2019, representatives from Dow-Aksa met with Carollo's structural engineer and others to discuss the use of carbon fiber materials in the grit chamber rehabilitation and repair process. Carbon fiber has the following properties: lightweight, high tensile strength, high stiffness and corrosion-resistant. The carbon fiber from Dow-Aksa has not previously been used in wastewater treatment plant application so there is a lack of historical data to support its use in this type of environment. The Dow-Aksa representatives explained that the carbon fiber system would have to be engineered by Dow-Aksa engineers and their representatives would also be required to install the system during construction. They estimate that the cost of the material is approximately eight times the cost of concrete. The use of carbon fiber will be further analyzed during the design process and in coordination with the Construction Manager at Risk (CMAR).



Section 4

ALTERNATIVES EVALUATION

4.1 Influent Pump Station

4.1.1 Alternative 1

Alternative 1 consists of rehabilitating IPS #2 and increasing its firm capacity from 91.5 to 125 mgd. For this alternative, IPS #2 would remain the primary pump station. In order to provide operational redundancy, IPS #1 would also be modified and upgraded to a firm capacity of 80 mgd. IPS #1 would only serve as a standby pump station when IPS #2 is out of service for maintenance or repairs.

Computation Fluid Dynamics (CFD) modeling was conducted for this alternative to evaluate hydraulic conditions that would exist if existing IPS #2 was upgraded to 125 mgd. Results indicated that hydraulic conditions that would exist using the current wet well configuration would not comply with Hydraulic Institute (HI) standards. Upgrades that would be required to comply with HI standards are included in this evaluation.

Table 4 below summarizes the rehabilitation activities associated with Alternative 1.

Table 4 Alternative 1 Summary

IPS #1 IPS #2

• Remove sand from abandoned portions of the existing wet well

• Demolish concrete dividing walls installed as part of previous 2001 modifications

• Recoat/line wet well • Install 4 new 20 mgd submersible

pumps (no standby) • Install 42 inch discharge pipe to

connect to existing screening influent channel

• Recoat wet well • Replace electrical conduit inside wet

well • Repair concrete damage • Relocate electrical building away

from directly above the wet well • Replace and upgrade ventilation

system • Replace and upgrade odor control

system • Upgrade pump station to a firm

capacity of up to 125 mgd by installing 5 (4+1) 31.25 mgd pumps

• Add prism type baffle in front of each suction pipe in the wet well

• Replace existing 24 inch pump suction elbow with 36 inch x 24 inch reducing elbow and modify the suction pipe in the floor slab as needed

Figures 3 and 4 illustrate the proposed IPS #1 and #2 upgrades.



Figure 3 Proposed IPS #1 Upgrades

Figure 4 Proposed IPS #2 Upgrades



Activities associated with improving the hydraulic conditions in the wet well based on results of the CFD modeling includes installing a sump prism and replacing the existing 24 inch elbows with a 36 inch x 24 inch reducing elbows. The existing suction elbows are encased in the concrete foundation of the IPS. Replacing these elbows would be extremely challenging, expensive, could jeopardize the integrity of the foundation, and would require a structural analysis during design.

Table 5 below summarizes the pros and cons of Alternative 1.

Table 5 Alternative 1 - Pros & Cons

Pros Cons

• Improve reliability and redundancy by providing a standby wet well and pump station for maintenance activities

• Takes advantage of existing infrastructure

• Lowest cost alternative

• No ability to expand the influent pump station in the future

• Maintenance of two wet wells will be required

• Difficult to improve hydraulic conditions within IPS #2

4.1.1.1 Construction Cost Estimate

The estimated construction cost for Alternative 1 is approximately $20M. A detailed breakdown of this cost is included in Appendix A.



4.1.2 Alternative 2

Alternative 2 consists of building a new 80 mgd firm capacity dry weather pump station (IPS #3). IPS #3 would become the primary pump station and would be designed with the intent to expand in the future. IPS #2 would be rehabilitated to operate only during wet weather flows.

Table 6 below summarizes the improvements associated with Alternative 2.


IPS #1 IPS #2 IPS #3

• Continue to operate as return flow pump station or abandon in place

• Recoat wet well • Replace electrical conduits

inside wet well • Repair concrete damage • Relocate electrical building

away from directly above the wet well

• Replace and upgrade ventilation system

• Replace odor control system

• Upgrade pump station to a firm capacity of 91.5 mgd by installing 4 (3+1) 30.5 mgd pumps

• Build new IPS • Install 4 (3+1)

new 26.7 mgd pumps for a firm capacity of 80 mgd

• Allow for future expansion

• Provides dual wet well design when expanded in the future.

Figure 5 illustrates the proposed new 80 mgd firm capacity IPS #3 under Alternative 2.



Figure 5 Proposed IPS #3 for Alternative 2



Pros Cons

• Improve reliability and redundancy by providing a standby wet well and pump station for maintenance activities

• Makes use of existing infrastructure

• Provides ability to expand

• More costly than alternative one • Maintenance of two pump stations

will be required • Extensive structural requirements to

accommodate future expansion • Expensive construction for pump

station expansion in the future • More difficult controls to operate

2 pump stations concurrently

4.1.2.1 Cost Estimate




4.1.3 Alternative 3

Alternative 3 consists of building a new 125 mgd firm capacity pump station.



IPS #1 IPS #2 IPS #3

• Continue to operate as return flow pump station or remove from service

• Remove from service

• Build new IPS • Install 6 (4+2) new

31.25 mgd pumps for a firm capacity of 125 mgd

• Incorporates dual wet well design

• Able to handle wet weather peak flow with one wet well out of service

Figure 6 illustrates the proposed new 125 mgd firm capacity IPS #3 under Alternative 3.

Figure 6 Proposed IPS #3 for Alternative 3





Pros Cons

• Single pump station to operate and maintain

• Provides excess capacity up to 156 mgd

• Provides capability to handle wet weather peak flow with one well out of service

• Most costly alternative



4.2 Screening Facility

Two alternatives were evaluated for the screening facility. The first alternative uses the existing facilities for expansion and rehabilitation. The second alternative would abandon the existing facilities in place and construct a new screening facility. The alternatives are described in detail below and include planning level construction cost estimates.

4.2.1 Alternative 1

Alternative 1 consists of rehabilitating and expanding the existing screening facility to a peak capacity of 125 mgd.

The rehabilitation and expansion activities associated with Alternative 1 include the following:

• Place the existing fifth screen channel into service • Construct 3 additional new screen channels • Convert the first screen channel into a bypass channel • Install 7 new 18 mgd bar screens • Install 2 new screening compactors (1+1) • Relocate the existing hopper

Replace the existing conveyor with a conveyor that extends from the second channel to the hopper.



Figure 7 illustrates the rehabilitated and expanded screening facility.

Figure 7 Proposed Rehabilitated and Expanded Screening Facility for Alternative 1



Pros Cons

• Uses existing infrastructure • Reuses existing hopper • Provides a bypass channel • Provides screenings compactor

redundancy and means for bypassing the compactors

• Less expensive alternative

• Does not improve flow and solids distribution

• Difficult to expand



4.2.2 Alternative 2

Alternative 2 consists of building a new screening facility with a peak capacity of 125 mgd.





Existing Screening Facility New Screening Facility

• Continue to operate existing screening facility until new facility is placed online

• Build new concrete screening facility with flow distribution structure and centered bypass channel

• Install 4 new 42 mgd bar screens (3+1)

• Install 2 new screenings compactors (1+1)

• Provide full isolation capabilities

Figure 8 illustrates the new screening facility.

Figure 8 Proposed New Screening Facility for Alternative 2





Pros Cons

• Improves flow and solids distribution between channels

• Enhanced isolation capabilities • Provides a standby screen • Provides a centered bypass

channel • Provides screenings compactor

redundancy and means to bypass compactors

• Does not use existing infrastructure • More expensive alternative



4.3 Grit Removal and Handling Facilities

Two alternatives are considered for grit removal and handling. The first alternative rehabilitates existing facilities for improved performance and capacity expansion. The second alternative abandons the existing facilities in place and constructs new grit removal and handling facilities. These alternatives are described in detail below and planning level cost estimates are provided.

4.3.1 Alternative 1

Alternative 1 utilizes existing facilities and proposes the following:

• Converts existing pre-aeration basin into a second aerated grit chamber similar to the current aerated grit chamber

• Rehabilitates the existing aerated grit chamber and associated systems • The existing grit dewatering units would be replaced with new units that use similar

dewatering technology

The existing grit facilities are described in detail in Section 2.1.4. A depiction of the current facilities is shown in Figure 9.



Figure 9 Existing Grit Removal Facilities

Currently, there is only one grit chamber with no ability to remove grit if it is out of service. If maintenance is required it must be done while the chamber is in service. A second chamber provides redundancy and allows for repairs or maintenance without bypassing grit removal. The existing grit chamber dimensions are approximately 76 feet long by 25 feet wide with a water depth of 12 feet. Two grit chambers of this size with a peak hydraulic flow of 125 mgd would provide over 3.5 minutes of detention time. This detention time is within the typical 3-5 minute design criteria used for such facilities. Alternative 1 provides the second aerated grit chamber chamber by converting the remaining pre-aeration basin into a grit chamber. The associated grit pumps will be located in the existing grit pump room. Alternative 1 is illustrated in Figure 10.



Figure 10 Proposed Grit Removal Facilities

4.3.1.1 Grit Chamber 1 – Existing Rehabilitation

Based on the condition assessment, the following rehabilitation activities are recommended:

• Bypass (discussed below, drain and cleanout of chamber) • Structural repairs of deteriorated concrete walls and slabs • Demolish and reconstruct structurally deficient portions of influent box, recoat

surfaces • Remove and replace existing baffles • Add additional baffle to help direct air flow • Replace mechanical components including existing pumps and piping • Replace and possibly upsize air and water piping



4.3.1.2 Pre-aeration Basin Conversion to Grit Chamber No. 2

Converting the pre-aeration basin into a grit chamber will include the following:

• Remove and dispose of existing mechanical equipment items and debris • Structural modifications

Floor cutting and construction of hopper Concrete fill to slope floor towards hopper Construction of an influent box to direct flow entering new Grit Chamber No. 2 Various patching and cutting of new openings for pipes and gates

• Installation of interior baffles • New mechanical equipment including pumps, aeration blowers, grit and air piping,

corresponding electrical, instrumentation controls and piping

4.3.1.3 Grit Handling Facilities

The existing grit handling facilities would be upgraded to replace the existing 3 grit classifiers. Two grit classifiers will be replaced with larger capacity grit classifiers. The existing room does not allow for all three grit classifiers to be upsized due to layout and size constraints. The third new grit classifier would be sized similarly to the existing units.

During discussions with plant staff, bridging of the grit in the hopper has been an issue in the past. Increasing the side slope of the existing hopper could help alleviate this issue.

4.3.1.4 Bypass

Due to the structural deterioration discussed in the existing grit chamber, it is not recommended to empty chamber 1 while the influent channel is in use.

A bypass of the existing chamber is needed. Such bypass could include installing a bypass pipe into the influent channel that will allow the section of the influent channel adjacent to chamber 1 to be drained so that structural repairs at chamber 1, particularly at the shared wall with the influent channel, can be completed safely. The proposed bypass pipe is illustrated in Figure 11.



Figure 11 Potential Bypass Pipe

The channel dimensions restrict the size of pipe that can fit in the channel. The pipe size may be limited to 66 inches and is estimated to handle a maximum flow of 75 mgd. This should be sufficient to handle the current dry weather flow received at the RBWWTP. It is recommended that this bypass option occur during the lowest flow months.

Installation of the pipe would require removal of an existing gate and removal of portions of the top of the existing channel.

4.3.1.5 Grit Pumps

The grit pumps at this planning level stage are estimated to be 10 HP heavy duty recessed impeller pumps. Five new pumps would be added for the converted chamber and the existing five pumps would be replaced with similar pumps. This will update the mechanical equipment and provide a single type of pump which is advantageous for replacement parts and maintenance.

4.3.1.6 Blowers

Currently, air is supplied to the aerated grit chamber by the blowers serving the secondary treatment process. It is proposed to install two dedicated 40 HP blowers for the grit facility. The blowers could potentially be located near the grit chambers in one of the locations under the existing grit handling facility.



4.3.1.7 Pros and Cons



Pros Cons

• Provides hydraulic redundancy • Uses existing infrastructure • Less expensive alternative

• Does not implement newer technologies

• Bypass required during construction • Limited expansion options • High odor control requirements


The estimated planning level construction cost of Alternative 1 is $18 million. A detailed breakdown of this cost is included in Appendix A.

4.3.2 Alternative 2

Alternative 2 includes construction of a new grit facility and abandoning the current grit facilities in place. A preliminary layout of the facility is shown in Figure 12.

Figure 12 Proposed New Grit Facilities



4.3.2.1 Grit Chambers

In Alternative 2, 270 degree design, sloped-bottom vortex grit chambers are proposed. In this type of chamber, flow enters through a tangential inlet channel, makes a 270-degree turn in the chamber and then exits to an outlet channel. The grit is trapped in the chamber and captured at the bottom in the hopper. It is then pumped out using grit pumps. A plan and section of a typical 270-degree vortex grit chamber is shown in Figure 13. Four vortex grit chambers would be needed to treat a peak flow of 125 mgd, each chamber is rated for 32 mgd hydraulically. The peak flow would be able to pass through 3 chambers (with a redundant level of treatment). This would allow for redundancy and the ability to isolate and take a chamber offline for repairs or maintenance.

Figure 13 270 Degree Vortex Design Grit Chamber

The grit removal system would include the following:

• Vortex grit chamber • Grit chamber inlet and outlet gates • Mixers • Fluidizing systems • Scour systems • Channel level monitoring system

The system would also include the current best practices followed in the industry for grit removal as well as some of the newest technologies.

4.3.2.2 Bypass

No flow bypass will be required for this alternative. The new grit chambers would be constructed separately and connected when completed. The existing facilities could then be isolated and abandoned or demolished without interruption to the plant operation.



4.3.2.3 Grit Mechanical

The grit pump station is proposed to be located directly underneath the elevated chambers. It is proposed to have one pump per chamber, for a total of four pumps. The pumps will then discharge to a new grit handling area with four new grit classifiers. The proposed pump area will not be enclosed, eliminating the need for a mechanical ventilation system.

Grit pipe plugging is a common issue due to the nature of grit. In order to minimize plugging each chamber will have its associated grit pump and grit washer. The grit piping will be designed to minimize connections and sharp bends. Flushing connections will be provided to flush grit piping as necessary. A dedicated water fluidizing system will also be provided at each grit chamber hopper to inject fluidization water into the bottom of the grit hopper before each pumping cycle starts.

4.3.2.4 Pros and Cons



Pros Cons

• Provides standby unit • Provides redundancy • Implements newer technologies • Reduced air usage and

associated energy cost • No bypass required during

construction (existing facilities remain in use)

• Does not reuse existing infrastructure • Higher cost alternative


The estimated planning level construction cost of Alternative 2 is $28 million. A detailed breakdown of this cost is included in Appendix A.

4.4 Electrical Building Based on the need to replace switchgears SG-4 and SG-5 due to hydrogen sulfide damage and the presence of hydrogen sulfide odor inside and in the proximity of the existing headworks building, relocation of headworks electrical building to a new location further away from hydrogen sulfide sources is recommended. The new Switchgears SG-4 and SG-5 can be relocated to the new electrical building. However equipment such as MCC-15, MCC-16, VFDs (i.e. VFD-1510, VFD-1520, VFD-1530, VFD-1550) and their active harmonic filters, and panels PP-B and PP-C should be replaced with new equipment in the new headworks electrical building.

The estimated relocation of equipment and construction cost for a new electrical building is approximately $1.4M.

4.5 Odor Control

Odor control alternatives were evaluated for Junction Box A, Lower Valley Meter Station, the new IPS, the expanded screening facility and the expanded grit facility.



4.5.1 Odor Control Airflow

There are a variety of ways to contain foul air. In collection systems, the conveyance pipe itself serves as the containment and transport structure and foul air is pulled from the gravity sewer’s headspace. In lift stations and treatment plants, channels, process tanks, and equipment should be covered to contain odors using corrosion resistant materials.

Once containment has been achieved, foul air is withdrawn from the contained area using FRP or other corrosion resistant duct and corrosion resistant foul air fans. It is usually more cost effective to only pull only the air flow necessary to maintain a slight vacuum on the covered area (compared to allowing fresh “sweep” air under the covered area). Covering concrete structures will contain hydrogen sulfide and other odorants, but it will also accelerate microbially induced corrosion. To protect structures from damage, exposed surfaces should be coated or lined with a suitable corrosion resistant material unless they are inherently corrosion resistant.

In collection systems, gravity sewer headspaces can serve as a duct; where slopes are uniform and headspaces are continuous, mechanical ventilation can sometimes maintain a measurable vacuum in a pipe headspace for well over a mile from the exhaust point.

Determination of airflow rate is specific to the area where air is withdrawn. Generally, the intent is to provide a slight vacuum in the headspace to prevent odorous air from escaping through gaps or openings in the covers. To prevent untreated air from escaping, a capture velocity of 200 fpm is targeted for openings in accordance with ASHRAE® and ACIGH® recommendations for industrial ventilation. For the openings that are covered, such as for enclosed screens, a reduction in the capture velocity is taken into account for the impact of the covers.

For covered areas, publications from the Water Environment Research Foundation (WERF®) recommend airflows based on the square footage of the covered area. A typical range of 0.2 to 2.0 cfm/ft2 is given and the actual value should be based on the “tightness” of the cover system. The value selected should consider future conditions such as leakage from thermal expansion and contraction as well as the ageing of gaskets and sealants. Experience has shown that using a value of 1 cfm/ft2 provides adequate capture airflow for the life of the installation in most cases.

Although useful for comparison purposes, the number of air changes per hour is usually not a determining factor in the odor control airflow unless necessary for meeting National Fire Protection Association (NFPA®) 820 electrical classification requirements. Airflow rates for odor control are not necessarily to provide a safe working atmosphere; additional supply air and careful attention to ventilation and fresh air supply is needed if spaces are to be occupied by personnel.

Table 15 provides preliminary calculated airflow for each of the selected alternatives provided in Sections 4.1 through 4.3.



Table 15 Odor Control Airflow

Location Total Airflow, cfm

New Influent Pump Station Wetwell 10,000

Existing Headworks Wetwell 12,000

Pump Discharge and Screens 11,000

Aerated Grit Chambers 9,000

Grit Handling Room 7,800

Return Flow Pump Station 7,000

Junction Box A and Lower Valley Meter Station 11,000

Total 60,000

4.5.2 Biotrickling Filters for Odor Control

Biotrickling filters (or bioscrubbers) are biological treatment systems that usually consist of a tower filled with inorganic media, an irrigation system and a recirculation pump for pH control, and a leachate drain. Normally reclaimed water is used for irrigation and to provide nutrients for the microorganisms but potable water can be used with suitable adjustments to the system. Excessively chlorinated water (over 3 mg/l) may create operational problems and should be avoided. If needed, chlorine can be removed from the water supply with a filter.

Foul air enters the unit though a corrosion resistant blower at the bottom of the tower and discharges through an opening in the top. Irrigation and recirculation water are sprayed down (counter current to airflow) on top of each stage and collect in the sump area. Foul air is passed through a wetted media where the microorganisms that are naturally present grow and consume hydrogen sulfide and other compounds and produce dilute sulfuric acid and elemental sulfur. Water is either recirculated or discharged depending on the specific process intent. Makeup water is added to control the pH and replace water lost to evaporation or drained.

Biotrickling filers typically perform best when airflows and odor concentrations do not fluctuate excessively. When hydrogen sulfide concentrations fluctuate rapidly, it has been observed that higher than normal concentrations will be exhausted from the biotrickling filter until the microbiology becomes acclimated to the higher concentrations. Peaking factors of 3 to 1 are not uncommon; in these cases the removal efficiency may decrease for a brief period. Carbon polishing units can capture any “blow through” that may occur. In areas where off-site complaints are not common, the carbon polishing step may not be necessary.

Biotrickling filters can effectively remove hydrogen sulfide to high efficiencies but vary in their removal of other reduced sulfur compounds. They can be optimized to reduce the concentrations of some non-hydrogen sulfide compounds by adjusting the irrigation supply to target a pH level favorable to the microbes that consume these compounds. Manufacturers typically offer media warranties and performance guarantees. Empty bed residence times vary by application; shorter residence times on the order of 6 to 8 seconds target hydrogen sulfide while longer residence times of up to 12 to 14 seconds are used to target non-hydrogen sulfide compounds. High concentrations of ammonia in the airstream should be avoided as this is detrimental to organism growth.



4.5.3 Odor Control Recommendations

Biotrickling filters for odor control are generally most cost effective for moderate to high hydrogen sulfide concentrations such as those seen in Section 2.1.6.1 and are recommended for the current headworks improvements. Other alternatives can be considered if desired. Additional field testing should be conducted to determine design values for hydrogen sulfide concentrations but it is anticipated that a total of six biotrickling filters will be used. Due to the distance from the other facilities, a separate odor control facility for Junction Box A and the Lower Valley Meter Station should be considered.

An 8,000 cfm biotrickling filter is currently being installed at Junction Box A. Although slightly lower than the calculated airflow for this area, it is recommended that a reassessment be conducted after startup of this unit to determine if odor control objectives are being achieved.

4.6 Life-Cycle Cost Analysis

A life-cycle cost analysis was conducted for each individual alternative. The alternatives were evaluated over a 20 year life cycle period. For this analysis, the construction year was assumed to be 2021 and the first year of operation is estimated to be 2023. Each respective life-cycle cost analysis includes capital project costs and operating and maintenance (O&M) expenses. The O&M expenses for each alternative were calculated by estimating electrical costs, miscellaneous maintenance costs, and operational personnel costs. The total annual operating cost was then escalated annually based on an assumed inflation rate of 3 percent. A total present worth cost in 2019 dollars was calculated for each alternative, which are summarized below in Table 16. All estimates are based on an annual average daily flow of 51 mgd.

Table 16 Total Present-Worth of Each Alternative

Design Package Annual Estimated O&M Cost in 2019

Total Present-Worth Cost in 2019

Influent Pump Station Alternative 1 Alternative 2 Alternative 3

$464,000 $503,00

$550,000

$28,623,000 $42,403,000 $50,300,000

Screening Facility Alternative 1 Alternative 2

$175,000 $160,000

$22,308,000 $31,076,000

Grit Handling Facility Alternative 1 Alternative 2

$173,000 $135,000

$21,266,000 $30,616,000

Notes: (1) A more detailed description of these estimates can be found in Appendix B.

4.7 Selected Alternatives

On May 23, 2019 EPWater provided a letter to Carollo to document their decisions for improvements to the RBWWTP headworks. A follow up meeting was held on May 28, 2019 to discuss details of the decisions. During this meeting it was decided to overturn several of the decisions listed in the letter. The decision to move forward IPS Alternative #3 which includes the design of a new dual wet well pump station and abandon IPS #1 and #2 was made because of its superiority in ease of operation and maintenance compared to the alternatives. EPWater has elected to proceed with the alternatives shown in Table 17 below which overturn the EPWater decision letter dated May 23, 2019.



Table 17 RBWWTP Headworks Selected Alternatives

Title Selected

Alternative Alternative Summary

Estimated Construction Cost

Influent Pump Station

3

New dual wet well IPS, no pre-screening before pumps,

no future expansion, decommission IPS #2

$40M

Screening Facility 1 Rehabilitate and expand

existing infrastructure $19M

Grit Facility 1 Rehabilitate and expand

existing infrastructure $18M

Total Estimated Construction Cost $77M



Section 5

CONSTRUCTION SEQUENCING

Construction of the selected alternatives should be executed in a manner that minimizes impacts to plant operation. The following only represents a preliminary sequencing plan that will be further refined as the design progresses and with coordination with the CMAR contractor.

• The following activities can be performed while the plant continues normal operations: Construct new IPS #3 Construct expanded portions of the screening facility Remove existing odor control system prior to aerated grit chamber retrofit activities Drain and clean remaining pre-aeration basin Retrofit remaining pre-aeration basin into new aerated grit chamber Construction of the new odor control bio trickling filters and associated foul air

ducting • After new IPS #3 is constructed and ready to be placed into operation, bypass piping will

be installed from IPS #2 to the screening facility while the new pump station is tied-in to the existing screening influent channel.

• Once the expanded portions of the screening facility are complete and ready to be placed into operation, bulkheads will be installed while the new screening facility is tied into the system.

• After the new aerated grit chamber is complete and ready to be placed into service, flow will be diverted to the new aerated grit chamber via the bypass pipe discussed in Section 4.

• Bypass pumping for a short period of time, will be required to install the new bypass pipe that will allow for rehabilitation activities to commence in the existing aerated grit chamber.

• Once the existing aerated grit chamber is rehabilitated the bypass pipe can be removed. This may require bypass pumping or may be performed during a temporary shutdown if time permits.


FINAL | JULY 2019

Appendix A COST ESTIMATES FOR DESIGN ALTERNATIVES

PROJECT SUMMARY Estimate Class: 5Project: Roberto Bustamante Headworks Improvements PIC: SV

Client: EPWater PM: SVLocation: El Paso, TX Date: April 19, 2019

Zip Code: 79927 By: JB/HVP

Carollo Job # 11292A10 Reviewed: SV

NO. DESCRIPTION TOTAL

01 General Conditions $1,555,421

02 Pump Station No. 1 Rehab $315,833


04 Mechanical $5,781,257

05 Civil $55,016

06 Electrical $2,267,189

07 Instrumentation and Controls $867,189

08 Odor Control $1,300,000

09 HVAC $306,537

TOTAL DIRECT COST $12,890,654

Contingency 30.0% $3,867,196

Subtotal $16,757,850

General Contractor Overhead, Profit & Risk 10.0% $1,675,785


Escalation to Mid-Point 9.2% $1,695,894


Sales Tax 0.0% $0


Bid Market Allowance 0.0% $0

TOTAL ESTIMATED CONSTRUCTION COST $20,000,000

Engineering, Legal & Administration Fees 10.0% $2,000,000

Owner's Reserve for Change Orders 0.0% $0

TOTAL ESTIMATED PROJECT COST $22,000,000

RBWWTP Headworks Cost Estimate for Influent Pump Station Alternative 1

The cost estimate herein is based on our perception of current conditions at the project location. This estimate reflects our professional opinion of accurate costs at this time and is subject to change as the project design matures. Carollo Engineers have no control over variances in the cost of labor,

materials, equipment; nor services provided by others, contractor's means and methods of executing the work or of determining prices, competitive bidding or market conditions, practices or bidding strategies. Carollo Engineers cannot and does not warrant or guarantee that proposals, bids or actual

construction costs will not vary from the costs presented as shown.







02 New Dry Weather Pump Station $3,598,674



05 Civil $916,705


07 Instrumentation and Controls $1,411,651

08 HVAC $200,000



Contingency 30.0% $5,289,690






Sales Tax 0.0% $0


Bid Market Allowance* $3,500,000






The cost estimate herein is based on our perception of current conditions at the project location. This estimate reflects our professional opinion of accurate costs at this time and is subject to change as the project design matures. Carollo Engineers have no control over variances in the cost of

labor, materials, equipment; nor services provided by others, contractor's means and methods of executing the work or of determining prices, competitive bidding or market conditions, practices or bidding strategies. Carollo Engineers cannot and does not warrant or guarantee that

proposals, bids or actual construction costs will not vary from the costs presented as shown.







02 New Pump Station $3,923,928


04 Civil $1,706,506




08 HVAC $236,899


Contingency 30.0% $5,979,128






Sales Tax 0.0% $0


Bid Market Allowance* $7,000,000





*A bid market allowance has been added due to the deep excavation that will be required fot the construction of the IPS








Carollo Job # 11292A10 Reviewed: WK/SV



02 Rehab Screens Facility $1,072,008


04 Civil $76,717




08 HVAC $0


Contingency 30.0% $3,475,311




Payment and Performance Bond 1.0% $150,597




Sales Tax 0.0% $0







RBWWTP Headworks Cost Estimate for Screening Facility Alternative 1

The cost estimate herein is based on our perception of current conditions at the project location. This estimate reflects our professional opinion of accurate costs at this time and is subject to change as the project design matures. Carollo Engineers have no control over variances in the cost of labor, materials, equipment; nor services provided by others, contractor's means and methods of executing the work or of determining prices, competitive bidding or market conditions, practices or bidding strategies. Carollo Engineers cannot and does not warrant or guarantee

that proposals, bids or actual construction costs will not vary from the costs presented as shown.







02 New Screens Facility $3,929,841


04 Civil $107,493




08 HVAC $0


Contingency 30.0% $5,093,303




Payment and Performance Bond 1.0% $220,710




Sales Tax 0.0% $0







RBWWTP Headworks Cost Estimate for Screening Facility Alternative 2






Zip Code: 79927 By: CS



01 Aeration Chamber Conversion $2,091,879

02 Existing Chamber Rehab $773,181

03 Bypass $506,466

04 HVAC and Odor Control $3,005,090


06 Blower Equipment Addition $247,227

07 Odor Control Demolition $194,314

08 Hydraulic Conveyance Imp $2,650,000


Contingency 30.0% $3,440,447






Sales Tax 0.0% $0







RBWWTP Headworks Cost Estimate for Grit Facility Alternative 1






Zip Code: 79927 By: CS




02 New Grit Facility $3,851,764


04 Civil $302,564





Contingency 30.0% $5,344,126






Sales Tax 0.0% $0







RBWWTP Headworks Cost Estimate for Grit Facility Alternative 2





FINAL | JULY 2019

Appendix B LIFE CYCLE COST ESTIMATES FOR DESIGN ALTERNATIVES

2019 Electricity Cost: 0.09 $/kWh

Equipment Operating Units HP per Unit Total HP kW

Annual

Operation

(days)

Operation

Time (hr/day)kWh/year

Annual Power

Cost

Pumps

New IPS #2 Pumps 2 300 600 447.6 335 24 3,598,704 $323,883

Standby IPS #1 Pumps 3 300 900 671.4 30 24 483,408 $43,507

Bio-Trickling Filter 1 50 50 37.3 24 326,748 $29,407

1156 TOTAL ANNUAL ELECTRICAL COST: $396,797

Influent Pump Stations $10,000.00

Odor Control $5,000.00

Annual Miscellaneous Maintenance Costs $15,000.00

Burdened Per Labor Hour Cost $40 (average all personnel)

Hours per year 1239 (3hr/day maintanance, 40hr/year/wetwell, 8hr/year/pump maintanance)

Annual Personnel Costs (2019): $49,560


Hours per year 50 (50 hr/filter/year)


TOTAL ANNUAL OPERATING COST (2019): $464,000

RBWWTP Headworks O&M Cost Estimate for Influent Pump Station Alternative 1

Electricity

TOTAL POWER CONSUMPTION (kW):

Odor Control

Pumps

Operations Personnel

Miscellaneous Maintenance

Odor Control

Life Cycle Period (years): 20

Construction Year: 2021

Begin Operating: 2023

Last Year of Analysis: 2043

Discount Rate: 4%

Inflation Rate: 3%

Base Cost Year: 2019

Design Costs $2,000,000

Total Capital Cost $20,000,000

Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $1,000,000 $1,000,000 $10,000,000 $10,000,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0

Operating & Maintenance Expenses $0 $0 $0 $0 $522,236 $537,903 $554,040 $570,661 $587,781 $605,415 $623,577 $642,285 $661,553 $681,400 $701,842 $722,897 $744,584 $766,921 $789,929 $813,627 $838,036

Total Cost $1,000,000 $1,000,000 $10,000,000 $10,000,000 $522,236 $537,903 $554,040 $570,661 $587,781 $605,415 $623,577 $642,285 $661,553 $681,400 $701,842 $722,897 $744,584 $766,921 $789,929 $813,627 $838,036

Discounted Cost $1,000,000 $961,538 $9,245,562 $8,889,964 $446,410 $442,117 $437,866 $433,656 $429,486 $425,356 $421,266 $417,216 $413,204 $409,231 $405,296 $401,399 $397,539 $393,717 $389,931 $386,182 $382,469

Total Present-Worth Cost in 2019: $28,623,000


Life Cycle Criteria



Annual

Operation

(days)

Operation

Time

(hr/day)

kWh/yearAnnual Power

Cost

New IPS #3 Pumps 2 350 700 522.2 335 24 4,198,488 $377,864

Wet Weather IPS #2 Pumps 2 300 600 447.6 30 24 322,272 $29,004













Pumps

Electricity


TOTAL POWER CONSUMPTION (kW)

Odor Control

Pumps



Odor Control





Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $1,650,000 $1,650,000 $16,500,000 $16,500,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $1,650,000 $1,650,000 $16,500,000 $16,500,000 $566,131 $583,115 $600,608 $618,627 $637,185 $656,301 $675,990 $696,270 $717,158 $738,672 $760,833 $783,658 $807,167 $831,382 $856,324 $882,014 $908,474

Discounted Cost $1,650,000 $1,586,538 $15,255,178 $14,668,440 $483,931 $479,278 $474,669 $470,105 $465,585 $461,108 $456,675 $452,283 $447,935 $443,628 $439,362 $435,137 $430,953 $426,809 $422,706 $418,641 $414,616



Life Cycle Criteria



Annual

Operation

(days)

Operation

Time

(hr/day)

kWh/year Annual Power

Cost

New IPS #3 Pumps 2 400 800 596.8 365 24 5,227,968 $470,517













Pumps

Electricity



Odor Control

Pumps



Odor Control





Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $2,000,000 $2,000,000 $20,000,000 $20,000,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $2,000,000 $2,000,000 $20,000,000 $20,000,000 $619,030 $637,601 $656,729 $676,431 $696,724 $717,625 $739,154 $761,329 $784,168 $807,694 $831,924 $856,882 $882,589 $909,066 $936,338 $964,428 $993,361

Discounted Cost $2,000,000 $1,923,077 $18,491,124 $17,779,927 $529,149 $524,061 $519,022 $514,032 $509,089 $504,194 $499,346 $494,545 $489,789 $485,080 $480,416 $475,796 $471,221 $466,690 $462,203 $457,759 $453,357



Life Cycle Criteria

Electricity


Equipment Units HP per Unit Total HP kW

Annual

Operation

(days)

Operation

Time

(hr/day)

kWh/yearAnnual Power

Cost

Screens

Screens 7 5 35 26.11 365 24 228,724 $20,585

Conveyor Belt 1 10 10 7.46 365 24 65,350 $5,881

Compactor 2 15 30 22.38 365 24 196,049 $17,644

Odor Control




Screening Facility $10,000.00





Hours per year 1198 (50 hr/screen/year, 50 hr/belt/year, 50 hr/compactor/year)






Screens

Odor Control


RBWWTP Headworks O&M Cost Estimate for Screening Facility Alternative 1





Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $950,000 $950,000 $9,500,000 $9,500,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $950,000 $950,000 $9,500,000 $9,500,000 $196,964 $202,873 $208,959 $215,228 $221,685 $228,335 $235,185 $242,241 $249,508 $256,993 $264,703 $272,644 $280,824 $289,248 $297,926 $306,864 $316,069

Discounted Cost $950,000 $913,462 $8,783,284 $8,445,465 $168,366 $166,747 $165,143 $163,556 $161,983 $160,425 $158,883 $157,355 $155,842 $154,344 $152,860 $151,390 $149,934 $148,492 $147,065 $145,650 $144,250


RBWWTP Headworks Life Cycle Cost Analysis for Screening Facility Alternative 1

Life Cycle Criteria



Annual

Operation

(days)

Operation

Time (hr/day)kWh/year

Annual Power

Cost

Screens 4 5 20 14.92 365 24 130,699 $11,763

Conveyor Belt 1 10 10 7.46 365 24 65,350 $5,881

Compactor 2 15 30 22.38 365 24 196,049 $17,644



Screening Facility $10,000.00




Hours per year 1042 (50 hr/screen/year, 50 hr/belt/year, 50 hr/compactor/year)







Odor Control

Screens

RBWWTP Headworks O&M Cost Estimate for Screening Facility Alternative 2

Electricity

Screens

Odor Control







Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $1,400,000 $1,400,000 $14,000,000 $14,000,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $1,400,000 $1,400,000 $14,000,000 $14,000,000 $180,081 $185,484 $191,048 $196,780 $202,683 $208,764 $215,027 $221,477 $228,122 $234,965 $242,014 $249,275 $256,753 $264,456 $272,389 $280,561 $288,978

Discounted Cost $1,400,000 $1,346,154 $12,943,787 $12,445,949 $153,934 $152,454 $150,988 $149,536 $148,099 $146,675 $145,264 $143,868 $142,484 $141,114 $139,757 $138,413 $137,083 $135,764 $134,459 $133,166 $131,886


RBWWTP Headworks Life Cycle Cost Analysis for Screening Facility Alternative 2

Life Cycle Criteria



Annual

Operation

(days)

Operation

Time

(hr/day)


Cost

New Pumps (3 cycling @ 10 HP per chamber) 3 10 30 22.38 365 8 65,350 $5,881

New Pumps (2 cycling @ 10 HP per chamber) 2 10 20 14.92 365 8.4 45,745 $4,117

Centrifugal Fans 4 10 40 29.84 365 24 261,398 $23,526

Blowers 1 40 40 29.84 365 12 130,699 $11,763

Sump Pumps 1 3 3 2.238 183 1 408 $37

Mechanical Slide Gates 5 1 5 3.73 52 0.17 33 $3

High Pressure Washers 1 6 6 4.476 365 1 1,634 $147

Motorized Valves 15 1 8 5.595 365 0.13 265 $24

Roll-Up Doors 2 1 2 1.492 365 1 545 $49

Motorized Jib Cranes 1 1 1 0.746 365 1 272 $25

Monorail 2 10 20 14.92 365 1 5,446 $490

Grit Cyclone and Classifier (per Wemco) large 1 2 2 1.492 360 24 12,891 $1,160

Grit Cyclone and Classifier (per Wemco) small 1 2 2 1.492 10 24 358 $32

Add 5% for Miscellaneous Small Loads 1 0 0 0 $2,363






Hours per year 2162








Grit Chamber

Odor Control

RBWWTP Headworks O&M Cost Estimate for Grit Facility Alternative 1

Electricity

Grit Basin

Odor Control






Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $900,000 $900,000 $9,000,000 $9,000,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $900,000 $900,000 $9,000,000 $9,000,000 $194,713 $200,554 $206,571 $212,768 $219,151 $225,726 $232,498 $239,472 $246,657 $254,056 $261,678 $269,528 $277,614 $285,943 $294,521 $303,357 $312,457

Discounted Cost $900,000 $865,385 $8,321,006 $8,000,967 $166,442 $164,841 $163,256 $161,686 $160,132 $158,592 $157,067 $155,557 $154,061 $152,580 $151,113 $149,660 $148,220 $146,795 $145,384 $143,986 $142,601



Life Cycle Criteria



Annual

Operation

(days)

Operation

Time

(hr/day)


Cost

New Pumps 2 15 30 22.38 365 6 49,012 $4,411

Sump Pumps 1 3 3 2.238 183 1 408 $37

Mechanical Slide Gates 8 1 8 5.968 52 0.17 53 $5

High Pressure Washers 1 6 6 4.476 365 1 1,634 $147

Motorized Valves 10 1 5 3.73 365 0.17 231 $21

Motorized Jib Cranes 1 1 1 0.746 365 1 272 $25

Monorail 1 10 10 7.46 365 1 2,723 $245

Grit Cyclone and Classifier (per Wemco) large 2 2 4 2.984 365 24 26,140 $2,353

Grit Cyclone and Classifier (per Wemco) small 2 3 6 4.476 365 24 39,210 $3,529

Add 5% for Miscellaneous Small Loads 1 0 0 0 $539






Hours per year 2177








Grit Chamber

Odor Control


Electricity

Grit Chamber

Odor Control






Discount Rate: 4%

Inflation Rate: 3%




Calendar Year 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039

Model Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Capital Costs $1,400,000 $1,400,000 $14,000,000 $14,000,000 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0 $0


Total Cost $1,400,000 $1,400,000 $14,000,000 $14,000,000 $151,944 $156,502 $161,197 $166,033 $171,014 $176,144 $181,429 $186,872 $192,478 $198,252 $204,200 $210,326 $216,635 $223,134 $229,828 $236,723 $243,825

Discounted Cost $1,400,000 $1,346,154 $12,943,787 $12,445,949 $129,882 $128,633 $127,396 $126,171 $124,958 $123,757 $122,567 $121,388 $120,221 $119,065 $117,920 $116,786 $115,663 $114,551 $113,450 $112,359 $111,279


RBWWTP Headworks O&M Cost Estimate for Grit Handling Facility Alternative 2

Life Cycle Criteria