Wastewater System Master Plan (Volumes 1 & 2) 2022

City of Hot Springs Utilities Department Wastewater System Master Plan Volumes 1 & 2 2022

Wastewater System Master Plan (WWSMP) Volume 1 May 2022

The Board Report, capturing major elements of the latest regular meeting of the Hot Springs Board of Directors, is part of the City of Hot Springs’ efforts to broaden its communications with the public. City Board meetings are open to the public, and agendas, minutes, and more information can be found at www.cityhs.net/Board or by contacting [email protected]. July 5, 2022 Board adopts Wastewater System Master Plan The Board passed Resolution R-22-114, adopting the 2022 Wastewater System Master Plan prepared by Crist Engineers. A safe and reliable wastewater system is essential to the continued health and growth of the City of Hot Springs and the customers it serves. The City’s wastewater system currently entails 26,828 connections, 2.3 million linear feet of gravity sewer lines, 1.3 million linear feet of force main lines, 12,000 manholes, 3,800 minor lift stations and 84 major lift stations. The system conveys and treats approximately 12.5 million gallons of wastewater per day. The master plan is extensive, having been two years in development and consisting of eight volumes and around 1,000 pages. It covers the complete wastewater system: force mains, gravity mains, lift stations, manholes and both wastewater treatment plants. The plan examines the existing wastewater system to determine current and future needs and develops a Capital Improvements Program (CIP) and operating budgets so the required near-, mid-and long-term improvements can be implemented in a timely fashion. It looks ahead through 2040 and, like the Water Master Plan, is a living document that will be reviewed every five years. Other Board actions Coming Events • Public Meeting • City Manager Bill Burrough and City Attorney Brian Albright will be the presenters; public is invited to attend • 5 p.m. on Wednesday, July 13, the Event Center at 305 Forest Lakes Blvd. (Director Karen Garcia, Dist. 5) • Let Your Light Shine fundraiser • Proceeds from fundraiser will support the pedestrian lighting project along Park Avenue • 5:30 p.m. on Sunday, July 24, at The Vapors (Director Erin Holliday, Dist. 1) • The Board tabled Ordinance O-22-26, which proposes to amend Ordinance No. 6410 regulating short-term residential rental (STR) businesses. It will be on the agenda for the Board’s meeting on Aug. 2. • The Board passed Resolution R-22-115, approving the Community Development Block Grant (CDBG) FYI 2022 Annual Action Plan and authorizing submission of a grant application to the U.S. Department of Housing and Urban Development (HUD) for projects listed in the plan. The Community Development Advisory Committee (CDAC) unanimously approved both the prioritized list of eligible project applications and the action plan. HUD requires that an approved action plan be submitted by July 12. HUD allocates 45 days for review, and approval of the action plan listing a project is no guarantee that the project will take place due to HUD’s environmental review process. • The Board passed Ordinance O-22-27, amending the Zoning Map from Suburban Residential (R-2) to Medium/High Density Residential (R-4) for approximately 10 acres around the 400 block of Shady Grove Road. • The Board passed Resolution R-22-112, awarding a bid from Nabholz Construction Company for construction of a bedroom addition at the Airport Fire Station. This was the only bid received, and at just below $96,000 was close to the projected and budgeted cost. This is phase one of three for the Fire Department’s final such remodel to provide greater privacy for the department’s female firefighters.

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES1 Executive Summary Introduction The City of Hot Springs (CHS) engaged Crist Engineers, Inc. to develop a wastewater system master plan (WWSMP). The master plan is intended to evaluate the infrastructure components that service the customers of the City of Hot Springs and determine if those components can serve as the community continues to grow. Currently, there are 26,828 wastewater connections within the CHS service area. Of those connections approximately 90% are residential type connections. Most of the existing sewer connections (64%) are within city limits. Table ES-1 – Wastewater Connections Summary Connection Type Inside City Limits Outside City Limits Connections Residential 14,709 9,301 24,010 Commercial 2,359 450 2,809 Industrial 3 6 9 Total 17,071 9,757 26,828 Currently, the CHS collects, conveys, and treats approximately 12.5 million gallons of wastewater each day. The result of this treatment is that the WWTPs produce approximately 20,000 wettons (~22,000 wet-cubic yards (CY)) of biosolids annual. To serve the customers there are approximately 2,300,000 LF of gravity sewer lines, 1,300,000 LF of force main lines, 12,000 manholes, 3,800 minor lift stations (2 to 5 hp, grinder stations) and 84 major lift stations.

SOUTHWEST WWTP FAIRWOOD LIFT STATION STOKES LIFT STATION Mazarn Fairwood Southwest SOUTHWEST/ DAVIDSON DRIVE WWTP DRAINAGE BOUNDARY 0 0.75 1.5 3 4.5 6 Miles

HOT SPRINGS CREEK LIFT STATION GULPHA LIFT STATION DAVIDSON DRIVE WWTP Davidson Hot Springs Gulpha Creek CITY LIMITS

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES3 The CHS, with the assistance of RJN Group, Inc. developed a Sewer Evaluation and Capacity Assurance Plan (SECAP) in 2010. This evaluation included the inspection of approximately 12,000 manholes and survey of all 10 inch or larger lines. From those evaluations a series of recommended improvements were developed for the various pump stations, force mains, gravity mains and manholes. Some of the improvements implemented from these studies included the following: • Adding SCADA monitoring to the lift stations and grinder stations. • Adding backup power or backup pumping to the major lift stations. • Rebuilding of major improvements to the Fairwood, Hogan, Molly Springs, and Stokes lift stations. • Rebuilding or rehabilitation of about one third of the system manholes. • Rebuilding miles of existing gravity sewer mains. • Installing new large diameter force mains that extended for miles across the breadth of the city. • Installing new Davidson Drive WWTP Headworks and UV Disinfection. WWSMP Evaluations This master plan was intended to consider the following infrastructure components that comprise the CHS wastewater system: 1. Collection System a. Gravity Sewer b. Force Mains c. Minor Lift Stations (Grinder Stations) d. Major Lift Stations 2. Wastewater Treatment Plants (WWTP) a. Davidson Drive WWTP b. Southwest WWTP 3. Biosolids Management Due to the topography of the CHS service area, the majority of the wastewater is pumped to the treatment plants. The collection system can be subdivided into six (6) basins; 1. Mazarn 2. Hot Springs Creek 3. Fairwood 4. Davidson Drive 5. Gulpha 6. Southwest WWTP

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES4 Due to the extensive evaluation and work completed to date within the collection system, the WWSMP will incorporate the SECAP evaluation and recommendations. These evaluations were focused on gravity collection system, lift stations and force mains. CHS and the ADEQ executed a Consent Administrative Order (CAO) in 2011 (initiated in 2008) which resulted in an investment of approximately $70 million dollars in the wastewater collection system in recent years. The majority of these funds were used to address infrastructure needs minimizing the number and duration of associated gravity sewer overflows (SSO’s). In 2022, ADEQ and CHS executed an amendment to the existing CAO LIS No.: 08-099-002 that addresses Gulpha basin SSO’s. Minor lift station rehabilitation/ replacement is an ongoing and continual process. The evaluation of these stations was not conducted on an individual basis but as a collective. The collective evaluation was to determine the total estimated cost of this system and to determine an estimated annual cost related to the ongoing rehabilitation/ replacement program. In-depth evaluations were completed of the WWTPs, biosolids management and major lift stations for the development of the WWSMP. Crist Engineers, Inc. conducted field evaluations of Davidson Drive, Southwest WWTP and 82 major lift stations to determine the needs of each individual infrastructure item. These field evaluations produced an approximate 300-page report that, in-conjunction with CHS staff, was then used to develop recommended improvements for the capital improvements plan. Biological and hydraulic modeling were utilized in the treatment evaluation of Davidson Drive and Southwest WWTP. Biological modeling consisted of conducting eight (8) alternative simulation scenarios utilizing various flow and loading regimes. Hydraulic modeling was used to develop the 3 planning scenarios (near, mid and long-terms) to ensure storm event flow rates can be properly managed at the WWTPs. In 2022, ADEQ and CHS executed a CAO LIS No. 22-007 related to the Davidson Drive WWTP that addresses discharge permit excursions from this wastewater treatment plant. These CAO related projects focus on conveyance piping, chemical feed system, aeration system, secondary clarification and disinfection related projects. Onsite pumping and conveyances need of main process flows, waste and side streams were also evaluated and considered during the development of the WWSMP. Evaluations at the existing WWTPs also considered the support facility needs associated with the control, laboratory, and maintenance building(s). Biosolids management evaluations focused on Davidson Drive WWTP. Southwest WWTP biosolids are to be conveyed and handled at Davidson Drive WWTP. At Davidson Drive WWTP,

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES5 biosolids processing considered six (6) handling scenarios and five (5) final management options. The final management options considered were: 1. Drying 2. Composting – Windrow 3. Composing – Rotary Drum/ Windrow 4. Land Application 5. Landfill The WWSMP recommended biosolids management approach was to continue windrow composting and landfilling. Biosolids processing also considered four (4) thickening processes, three (3) dewatering technologies and one (1) side stream wash water treatment system during the development of the WWSMP. CHS intends to have the majority of the near-term capital improvements focus on the Gulpha basin and Davidson Drive WWTP wastewater treatment plants (WWTPs) while continuing to rehabilitate the collection system in other areas. WWSMP Growth Growth in wastewater conveyance and treatment needs is indicative of a growing and prosperous community. CHS is projected to continue growth of its water and wastewater system to meet the needs of the community. Similar to the Water Master Plan, developed by Crist Engineers, Inc. in 2018, a 1% growth rate was used to determine future projected influent flow rates. The future year used for projections for the WWSMP was established as 2040 or an approximate 20-year growth period. Table ES-2 – Davidson Drive WWTP Influent Flow Projections Parameters 1992 Design Flow 12 MGD 2018 Average Daily (AD) Flow 12.04 MGD Projected Growth Rate 1 % 2040 Average Day (AD) Projected Flow Rate 14.99 MGD 2040 Average Day (AD) Design Flow Rate 16 MGD 2040 7-Daily Average (DA) Design Flow Rate 20 MGD Peak Day Inflow/ Infiltration (I/I) Design Storm Event 94 MGD

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES6 Table ES-3 – Southwest WWTP Influent Flow Projections Parameters 2008 Design Flow 0.85 MGD 2018 Average Daily (AD) Flow 0.46 MGD Projected Growth Rate 1 % 2040 Average Daily (AD) Projected Flow Rate 0.69 MGD 2040 Design Average Daily (AD) Flow Rate 0.74 MGD 2040 Design 7-Daily Average (DA) Flow Rate 0.925 MGD Peak Day Inflow/ Infiltration I/I Design Storm Event 4.25 MGD To account for the potential under projections, data error or other unknowns, the 2040 design average daily (AD) flow rate was selected as 16 MGD (or an additional 6.7%) for Davidson Drive WWTP and 0.74 MGD for Southwest WWTP. To determine the maximum 7-Daily Average (DA) flow rate, a 1.25 factor was applied to the design AD flow rate. The 1.25 factor was taken from Wastewater Engineering Treatment and Resource Recovery, 5th Edition (Metcalf and Eddy et al.) for wastewater treatment plants of intermediate size. It is anticipated that the wastewater system needs will grow by 25% over the next approximate 20 years.

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES7 Minor Lift Stations The CHS currently has approximately 3,800 minor lift stations that they must rehabilitate, replace and maintain. These small stations are located primarily around Lake Hamilton to provide sanitary sewer service to the associated lake front residences. The CHS currently has an extensive repair and rehabilitation program that continuously addresses the needs of these minor lift stations. Each location and needs are site specific. However, the estimated costs of this program for these lift stations is estimated to be between $5 million to $10 million over the next 20 years. To address this cost, an analysis was completed that includes a 3.5% average annual inflation over a term of 20 years. It is anticipated that an annual rehabilitation/ replacement fund of approximately $500,000 per year should be targeted each year for the repair and rehabilitation program. Table ES-4 – Proposed Minor Lift Stations Estimated Annual Cost Summary Phase Location Annual Cost Summary1 - Minor Lift Stations $500,000.00 Total Cost Summary1 Total $6,669,000.00 1Present worth analysis and completed in 2022 dollars when considering a 3.5% average annual inflation rate. This continual repair and rehabilitation program is intended to replace vital system components associated with the minor lift stations that will result in a more efficient, reliable and resilient wastewater system.

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES8 WWSMP Projects The following projects were identified to meet the regulatory, growth and aged-infrastructure needs within the WWSMP. Table ES-5 – Near Term Projects (CAO) outlines projects specific to needs necessary to address current CAO’s. Table ES-5 – Near-Term Projects (CAO) CAO Projects No.1 Phase Description Basin Location Cost Summary Status Davidson Drive WWTP 1A NearTerm/ CAO Piping Improvements Davidson Drive WWTP $17,664,203.00 Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond 1B NearTerm/ CAO Chemical System Improvements Davidson Drive WWTP Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond 1C NearTerm/ CAO Aeration Basin and Blowers Davidson Drive WWTP Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond 1D NearTerm/ CAO Secondary Clarification Davidson Drive WWTP Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond 1E NearTerm/ CAO UV Disinfection Davidson Drive WWTP Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES9 Table ES-5 – Near-Term Projects (CAO) (cont.) Collection System 2 NearTerm/ CAO Grand Avenue2 Gulpha $286,144.00 Complete – 2022, 2020 Bond 3 NearTerm/ CAO Main Street2 Gulpha $726,975.00 Design – Encumbered 2022 Capital Investment Funds, Construction – Encumbered 2022 Capital Investment Funds 4 NearTerm/ CAO Spring Street Gulpha $3,968,000.00 Design – Encumbered 2020 Bond, Construction – Unencumbered 2020 Bond 7 NearTerm/ CAO Gulpha Interceptor Gulpha $20,124,061.00 Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond 8 NearTerm/ CAO Lakeside Lift Station, MH 5254 to Lakeside Lift Station Mazarn $710,506.00 Planned, Unencumbered 2022 Bond 9 NearTerm/ CAO Ridgeway Street Gulpha $2,556,786.00 Planned, Unencumbered 2022 Bond 10 NearTerm/ CAO Southwest Collection or Gravity Mains Mazarn $282,450.00 Planned, Unencumbered 2022 Bond Force Mains 5 NearTerm/ CAO Gulpha Force Main Gulpha $8,113,000.00 Design – Encumbered 2020 Bond, Construction – Unencumbered 2020 Bond Lift Stations 6 NearTerm/ CAO Gulpha Lift Station Gulpha $6,528,000.00 Design – Encumbered 2020 Bond, Construction – Unencumbered 2022 Bond Total (Items 1-10) $60,960,125.00 - 1Arrangement subgrouping is by wastewater system component and drainage basin. Arrangement is not necessarily a representation of ranking at this time. All projects shown are necessary for compliance with the CAO. 2Actual bid opening cost.

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES10 Table ES-6 – Near-Term Projects (Non-CAO) Non-CAO Projects No.1 Phase Description Basin Location Cost Summary Status Force Mains 12 Near-Term Mazarn Force Main Mazarn $3,950,784.00 Planned, Unencumbered 13 Near-Term Albert Pike Rd Force Main Fairwood $1,039,000.00 Planned, Unencumbered Lift Stations 14 Near-Term Mazarn #6 Mazarn $456,800.00 Planned, Unencumbered 15 Near-Term Mazarn #3 Mazarn $1,024,000.00 Planned, Unencumbered 16 Near-Term Mazarn #4 Mazarn $1,024,000.00 Planned, Unencumbered 17 Near-Term Quail House Mazarn $177,800.00 Planned, Unencumbered 18 Near-Term 70 West #11 Mazarn $149,900.00 Planned, Unencumbered 19 Near-Term South Rogers Mazarn $39,800.00 Planned, Unencumbered 20 Near-Term 70 West #14 Mazarn $633,000.00 Planned, Unencumbered 21 Near-Term Mazarn #1 Mazarn $512,800.00 Planned, Unencumbered 22 Near-Term Highway 270 Hot Springs Creek $956,800.00 Planned, Unencumbered 23 Near-Term Hot Springs #1 Hot Springs Creek $475,400.00 Planned, Unencumbered 24 Near-Term Hot Springs #3 Hot Springs Creek $793,000.00 Planned, Unencumbered 25 Near-Term Hot Springs #4 Hot Springs Creek $793,000.00 Planned, Unencumbered 26 Near-Term Files Road Hot Springs Creek $69,800.00 Planned, Unencumbered 27 Near-Term Malvern Highway Gulpha $442,000.00 Planned, Unencumbered 28 Near-Term Wilson Mill Gulpha $414,400.00 Planned, Unencumbered

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES11 Table ES-6 – Near-Term Projects (Non-CAO) (cont.) Davidson Drive WWTP 29 Near-Term Tertiary Filter No. 1 and 2 Davidson Drive WWTP $6,398,000.00 Complete – 2022, 2015 Bond and 2019/2020 Davidson Drive WWTP Expansion CIP Southwest WWTP 30 Near-Term Chemical Feed Improvements Davidson Drive WWTP $375,000.00 Planned, Unencumbered 31 Near-Term Sequencing Batch Reactor (SBR) Programming Improvements Davidson Drive WWTP $75,000.00 Planned, Unencumbered Biosolids 32 Near-Term Dewatered Biosolids Hauling Trailer (x2)/ Heavy Haul Tractor (x1) Davidson Drive WWTP $149,900.00 Planned, Unencumbered 56 Near-Term Biosolids Handling Davidson Drive WWTP $14,293,000.00 Planned, Unencumbered Total (12-32, 56) $34,243,184.00 - 1Arrangement subgrouping is by wastewater system component and drainage basin. Arrangement is not necessarily a representation of improvement needs, cost, importance, risk or other potential qualifying subgrouping with each phase at this time.

!. !. !. !. !. !. !. !. !. !. !. "/"/ SOUTHWEST WWTP FAIRWOOD LIFT STATION STOKES LIFT STATION Mazarn Fairwood Southwest 24 25 22 21 15 14 17 19 18 20 16 13 3 11 30 31 12 SOUTHWEST/ DAVIDSON DRIVE WWTP DRAINAGE BOUNDARY 0 0.75 1.5 3 4.5 6 Miles

!. !. !. !. !. !. "/"/"/"/ HOT SPRINGS CREEK LIFT STATION GULPHA LIFT STATION DAVIDSON DRIVE WWTP Davidson Hot Springs Gulpha Creek 6 23 8 27 28 26 5 2 9 7 4 8 1 29 32 56 CITY LIMITS

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES13 Table ES-7 – Mid-Term Projects No.1 Phase Description Basin Location Cost Summary Collection System 33 Mid-Term Adams St Realignment Hot Springs Creek $378,000.00 34 Mid-Term Malvern Ave Point Repair Gulpha $73,300.00 35 Mid-Term Forest View Court Capacity Enhancement Hot Springs Creek $258,500.00 36 Mid-Term Carpenter Dam Rd Capacity Enhancement Davidson Drive WWTP $1,494,500.00 Lift Stations 37 Mid-Term Mazarn #2 Mazarn $456,800.00 38 Mid-Term 70 West #9 Mazarn $1,024,000.00 39 Mid-Term 70 West #13 Mazarn $1,024,000.00 40 Mid-Term Houston Drive #11 Fairwood $177,800.00 41 Mid-Term Anderson Drive Fairwood $149,900.00 42 Mid-Term Beach Haven #7 Fairwood $39,800.00 43 Mid-Term Grand B Fairwood $633,000.00 44 Mid-Term Riverview Paradise Fairwood $512,800.00 45 Mid-Term Emerson Hot Springs Creek $956,800.00 46 Mid-Term Hot Springs Creek Hot Springs Creek $475,400.00 47 Mid-Term Hot Springs #2 Hot Springs Creek $793,000.00 48 Mid-Term Creekview Hot Springs Creek $793,000.00 49 Mid-Term Pet Cemetery Hot Springs Creek $69,800.00 50 Mid-Term Belevedere Hot Springs Creek $442,000.00 51 Mid-Term Red Oak Davidson Drive WWTP $414,400.00 52 Mid-Term Catherine Heights Davidson Drive WWTP $414,400.00 53 Mid-Term Chad Drive Gulpha $414,400.00 Davidson Drive WWTP 54 Mid-Term Return Activated Sludge (RAS) Pumping Improvements Davidson Drive WWTP $1,099,000.00 55 Mid-Term Sidestream Treatment System - Suspended Air Flotation No. 1 Davidson Drive WWTP $837,000.00 Biosolids 57 Mid-Term Thickened Solids Receiving Station at Davidson Drive WWTP Davidson Drive WWTP $464,000.00 Total $13,395,600.00 1Arrangement subgrouping is by wastewater system component and drainage basin. Arrangement is not necessarily a representation of ranking with each phase at this time. Recommendations were made to revisit and conduct additional inflow/ infiltration (I/I) investigations within the Hot Springs Creek and Stokes Tributaries. These investigations may result in the development of additional mid-term collection system projects.

!. !. !. !. !. !. !. !. !. !. SOUTHWEST WWTP FAIRWOOD LIFT STATION STOKES LIFT STATION Mazarn Fairwood Southwest 41 42 45 40 37 48 38 39 43 44 SOUTHWEST/ DAVIDSON DRIVE WWTP DRAINAGE BOUNDARY 0 0.75 1.5 3 4.5 6 Miles

!( !( !. !. !. !. !. !. !. "/"/"/ HOT SPRINGS CREEK LIFT STATION GULPHA LIFT STATION DAVIDSON DRIVE WWTP Davidson Hot Springs Gulpha Creek 46 50 52 53 47 49 51 35 36 33 34 54 55 57 CITY LIMITS

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES15 Table ES-8 – Long-Term Projects No.1 Phase Description Basin Location Cost Summary Collection System 58 Long-Term Hot Springs Creek Interceptor Hot Springs Creek $9,229,500.00 Lift Stations 59 Long-Term 70 West #2 Mazarn $149,900.00 60 Long-Term Tanglewood Mazarn $47,300.00 61 Long-Term Highway 290 Mazarn $138,500.00 62 Long-Term Farr Shores Mazarn $477,800.00 63 Long-Term Island #5 Mazarn $396,800.00 64 Long-Term Island #6 Mazarn $394,400.00 65 Long-Term Mount Carmel Mazarn $147,300.00 66 Long-Term Mazarn #5 Mazarn $26,800.00 67 Long-Term Caroline Acres Mazarn $42,800.00 68 Long-Term Housley Mazarn $24,400.00 69 Long-Term Glen Carin Mazarn $48,500.00 70 Long-Term Hogan Creek Mazarn $64,800.00 71 Long-Term Forrest Hill Mazarn $64,000.00 72 Long-Term Murphy Liquor Fairwood $373,400.00 73 Long-Term Sundance #2 Fairwood $64,000.00 74 Long-Term Rockefeller Fairwood $57,800.00 75 Long-Term Shore Acres Fairwood $52,800.00 76 Long-Term Mountain View Drive Fairwood $18,000.00 77 Long-Term Bayside Fairwood $52,800.00 78 Long-Term Cajun Boiler Fairwood $44,000.00 79 Long-Term Black Snake Fairwood $25,000.00 80 Long-Term Houston Drive #12 Fairwood $18,000.00 81 Long-Term Fairwood Fairwood $564,000.00

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES16 Table ES-9 – Long-Term Projects (cont.) 82 Long-Term Mid America Fairwood $126,400.00 83 Long-Term Sundance #1 Fairwood $150,000.00 84 Long-Term Beach Haven #9 Fairwood $33,800.00 85 Long-Term Houston Drive #10 Fairwood $41,800.00 86 Long-Term Thornton Ferry Fairwood $33,800.00 87 Long-Term Molly Creek Hot Springs Creek $18,000.00 88 Long-Term Fountain Lake Hot Springs Creek $184,000.00 89 Long-Term Stokes Hot Springs Creek $752,000.00 90 Long-Term Port-Au-Prince Hot Springs Creek $457,800.00 91 Long-Term Brown Drive Hot Springs Creek $574,400.00 92 Long-Term Highway 88 Hot Springs Creek $437,800.00 93 Long-Term Lazy Lane Hot Springs Creek $414,400.00 94 Long-Term Halteria Hot Springs Creek $408,000.00 95 Long-Term Moonlight Bay Hot Springs Creek $367,000.00 96 Long-Term Harold Drive Hot Springs Creek $416,800.00 97 Long-Term Scully Point Hot Springs Creek $374,800.00 98 Long-Term East Reed Hot Springs Creek $437,800.00 99 Long-Term Buena Vista Hot Springs Creek $394,400.00 100 Long-Term Carpenter Dam Davidson Drive WWTP $367,000.00 101 Long-Term Matthews Lane Davidson Drive WWTP $118,400.00 102 Long-Term RV City Davidson Drive WWTP $21,500.00 103 Long-Term Humphreys Davidson Drive WWTP $21,500.00 104 Long-Term Cedar Creek Gulpha $434,400.00 105 Long-Term Fairgrounds Gulpha $149,400.00 106 Long-Term Rock Creek Southwest WWTP $664,800.00 107 Long-Term Winkler Southwest WWTP $40,000.00

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES17 Table ES-10 – Long-Term Projects (cont.) Davidson Drive WWTP 108 Long-Term Secondary Clarifier No. 6 Davidson Drive WWTP $2,605,000.00 109 Long-Term Secondary Clarifier No. 3 Rehabilitation Davidson Drive WWTP $2,018,000.00 110 Long-Term Secondary Clarifier No. 4 Rehabilitation Davidson Drive WWTP $1,933,000.00 111 Long-Term Secondary Clarifier No. 1 Rehabilitation Davidson Drive WWTP $1,933,000.00 112 Long-Term Secondary Clarifier No. 2 Rehabilitation Davidson Drive WWTP $1,933,000.00 113 Long-Term Headworks Screen No. 3 Davidson Drive WWTP $1,129,000.00 114 Long-Term Headworks Grit Removal No. 3 Davidson Drive WWTP $1,987,000.00 115 Long-Term Tertiary Filter No. 3 Davidson Drive WWTP $4,938,000.00 116 Long-Term Equalization Pond Davidson Drive WWTP $4,452,000.00 117 Long-Term Operations and Maintenance Facility Davidson Drive. WWTP $6,644,000.00 Total $49,534,600.00 1Arrangement subgrouping is by wastewater system component and drainage basin. Arrangement is not necessarily a representation of ranking with each phase at this time.

!. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. !. SOUTHWEST WWTP FAIRWOOD LIFT STATION STOKES LIFT STATION Mazarn Fairwood Southwest 89 77 91 98 81 94 96 92 63 6 93 95 90 97 84 67 69 68 61 82 87 106 75 60 107 59 66 79 78 85 80 76 74 83 86 73 71 SOUTHWEST/ DAVIDSON DRIVE WWTP DRAINAGE BOUNDARY 0 0.75 1.5 3 4.5 6 Miles

!. !. !. !. !. !. !. !. !. !. !. HOT SPRINGS CREEK LIFT STATION GULPHA LIFT STATION DAVIDSON DRIVE WWTP Davidson Hot Springs Gulpha Creek 99 100 62 64 105 88 101 65 102 103 58 CITY LIMITS

Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. ES19 The majority of the WWSMP costs are associated with Davidson Drive WWTP. Collection system and lift stations account for over 45% of the planned costs. Table ES-11 – Projects Type Summary Distribution Table ES-12 – Projects Phase Summary Distribution Collection System 25.4% Force Mains 8.3% Lift Stations 21.5% Davidson Dr. WWTP 35.1% SW WWTP 0.3% Biosolids 9.4% Near-Term Mid-Term 60.2% 8.5% Long-Term 31.3%

Page 1 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. TABLE OF CONTENTS Chapter 1 – Project Objectives and Goals.............................................................................................................................13 Section 1.1 - Introduction ................................................................................................................................................13 Section 1.2 - Discussion....................................................................................................................................................14 Section 1.3 – Conclusion ..................................................................................................................................................14 Chapter 2 – Initial Planning and Evaluation Criteria .............................................................................................................15 Section 2.1 – Introduction................................................................................................................................................15 Table 2.1 – Wastewater Connections Summary (2022).......................................................................................15 Figure 2.1 – 2040 CHS Growth Service Area.........................................................................................................16 Section 2.2 - Discussion....................................................................................................................................................17 2.2.1 Effluent Limits...................................................................................................................................................17 Table 2.2 – SW WWTP NPDES Effluent Limit Summary........................................................................................18 Table 2.3 – SW WWTP NPDES Effluent Active Permit Periods.............................................................................19 Table 2.4 – Davidson Dr. WWTP NPDES Effluent Limit Summary ........................................................................20 Table 2.5 – Davidson Dr. WWTP NPDES Effluent Active Permit Periods..............................................................20 2.2.2 Influent Quality.................................................................................................................................................21 Table 2.6 – Influent Parameters...........................................................................................................................21 2.2.3 Influent Flow.....................................................................................................................................................22 Table 2.7 – SW WWTP Influent Flow Summary....................................................................................................22 Table 2.8 – Davidson Dr. WWTP Influent Flow Summary ....................................................................................22 2.2.4 Service Area......................................................................................................................................................22 2.2.5 Planning Area....................................................................................................................................................23 2.2.6 Planning Period.................................................................................................................................................23 2.2.7 Modeling Parameters.......................................................................................................................................23 Table 2.9 – Davidson Dr. WWTP Biosolids Production.........................................................................................24 Table 2.10 – Davidson Dr. WWTP Estimated Biosolids Disposal Costs Range......................................................24 2.2.8 Process Capacities ............................................................................................................................................25 Table 2.11 – Davidson Dr. WWTP Treatment Processes and Capacities..............................................................25 Table 2.12 – Davidson Dr. WWTP Treatment Processes and Capacities Cont. ....................................................26 2.2.9 Collection System .............................................................................................................................................26 Section 2.3 - Conclusion...................................................................................................................................................26

Page 2 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 2.13 – WWSMP Initial Near-Term CIP.........................................................................................................28 Chapter 3 – Biological and Hydraulic Modeling....................................................................................................................29 Section 3.1 - Introduction ................................................................................................................................................29 3.1.1 Process Flow Diagrams.....................................................................................................................................29 Figure 3.1 – Existing Davidson Dr. WWTP Simplified Process Flow Diagram – Liquid Treatment .......................30 Figure 3.2 – Existing Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment...................31 Figure 3.3 - Existing Southwest (SW) WWTP Simplified Process Flow Diagram – Liquid Treatment...................32 Figure 3.4 - Existing SWWWTP Simplified Process Flow Diagram – Biosolids Treatment....................................32 3.1.2 Influent Characteristics.....................................................................................................................................33 Table 3.1 - Davidson Dr. WWTP Influent Flow Projections ..................................................................................33 Table 3.2 - SW WWTP Influent Flow Projections..................................................................................................34 Table 3.3 - Davidson Dr. Influent Characteristics Projections..............................................................................36 Table 3.4 - SW WWTP Influent Characteristics Projections..................................................................................37 Table 3.5 – Davidson Dr. WWTP NPDES Effluent Limit Summary ........................................................................39 Table 3.6 – Southwest WWTP NPDES Effluent Limit Summary............................................................................40 3.1.3 Stoichiometric Discussions...............................................................................................................................41 3.1.3.1 Biological cBOD Utilization Process...............................................................................................................41 Figure 3.5 – Glucose Utilization Biochemical Reaction ........................................................................................42 Figure 3.6 – Biomass Production Represented as a Biochemical Reaction..........................................................42 Figure 3.7 – Biomass Growth Phases with cBOD Utilization ................................................................................42 Table 3.7 – High Rate, Conventional and Extended Aeration Operational Modes Comparison..........................43 3.1.3.2 Biological Ammonia Utilization Process........................................................................................................44 Figure 3.8 – Ammonia to Nitrite Biochemical Reaction .......................................................................................44 Figure 3.9 – Nitrite to Nitrate Biochemical Reaction............................................................................................44 3.1.3.3 Biological Phosphorus Utilization Process.....................................................................................................45 Section 3.2 – Discussion...................................................................................................................................................48 3.2.1 Influent Water Temperature ............................................................................................................................48 3.2.1.1 November 1 to March 31 Ammonia (NH-3 as N) ..........................................................................................48 3.2.1.2 April 1 – 30 Ammonia (NH-3 as N).................................................................................................................48 Table 3.8 – Corresponding Air and Water Temperatures ....................................................................................50 3.2.2 Primary Clarification/ Primary Sludge/ Anaerobic Digestion ...........................................................................51 Table 3.9 – Aerobic Digester vs. Aerated Sludge Storage.....................................................................................53 3.2.3 Biological Modeling Calibration........................................................................................................................54

Page 3 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 3.10 - Davidson Dr. Calibration Scenario Biological Simulator Configuration...........................................55 Figure 3.11 - SWWWTP Calibration Scenario Biological Simulator Configuration ...............................................56 Table 3.10 - Davidson Dr WWTP Biological Simulation Calibration Results.........................................................58 Table 3.11 - SWWWTP Biological Simulation Calibration Results........................................................................59 3.2.4 Biological Simulator..........................................................................................................................................60 3.2.4.1 Davidson Dr. WWTP ......................................................................................................................................61 3.2.4.1.1 Scenario 1 ...................................................................................................................................................61 Table 3.12 - Davidson Dr. Alkalinity Accounting...................................................................................................62 Figure 3.12 – Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Liquid Treatment (Near-Term CIP)........................................................................................................................................................................63 Figure 3.13 – Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment (NearTerm CIP) ..............................................................................................................................................................64 Figure 3.14 - Proposed Davidson Dr. WWTP Scenario 1A, 1B, 1C Simulator Configuration ................................65 Table 3.13 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 1A .......................................................67 Table 3.14 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 1B .......................................................70 Table 3.15 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 1C .......................................................73 3.2.4.1.2 Scenario 2 ...................................................................................................................................................75 Figure 3.15 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment (Mid-Term CIP)........................................................................................................................................................................76 Figure 3.16 – Proposed Davidson Dr. WWTP Scenario 2A, 2B, 2C Simulator Configuration................................77 Figure 3.17 - Proposed Davidson Dr. WWTP Scenario 2A1, 2B1, 2C1 Simulator Configuration ..........................78 Table 3.16 – Davidson Dr. WWTP Projected Dewatering and Non-Dewatering Operation Per Week – Scenario 2A/ Scenario 2A1 ..................................................................................................................................................80 Table 3.17 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2A – Operational Non-Dewatering.....81 Table 3.18 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2A1 – Operational Dewatering ..........82 Table 3.19 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2A Aggregate – Operational and NonOperational Dewatering .......................................................................................................................................83 Table 3.20 – Davidson Dr. WWTP Projected Effluent Quality and T-P Removal Example Analysis .....................84 Table 3.21 – Davidson Dr. WWTP Projected Dewatering and Non-Dewatering Operation Per Week – Scenario 2B/ Scenario 2B1...................................................................................................................................................86 Table 3.22 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2B – Operational Non-Dewatering.....87 Table 3.23 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2B1 – Operational Dewatering...........88 Table 3.24 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2B Aggregate – Operational and NonOperational Dewatering .......................................................................................................................................89

Page 4 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 3.25 – Davidson Dr. WWTP Projected Dewatering and Non-Dewatering Operation Per Week – Scenario 2C/ Scenario 2C1...................................................................................................................................................91 Table 3.26 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2C – Operational Non-Dewatering.....92 Table 3.27 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2C1 – Operational Dewatering...........93 Table 3.28 – Davidson Dr. WWTP Projected Effluent Quality – Scenario 2C Aggregate – Operational and NonOperational Dewatering .......................................................................................................................................94 3.2.4.1.3 Scenario 3 - Beyond the Planning Period – Davidson Dr. WWTP...............................................................96 Figure 3.18 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Liquid Treatment – Beyond Planning Period (Long-Term CIP)..........................................................................................................................98 Figure 3.19 - Proposed Davidson Dr. WWTP Beyond the Planning Period – 24 MGD – IFAS ..............................99 Table 3.29 – Davidson Dr. WWTP Projected Effluent Quality – Beyond the Planning Period – 24 MGD – IFAS (Operational Dewatering)...................................................................................................................................101 3.2.4.2 Southwest (SW) WWTP ...............................................................................................................................102 3.2.4.2.1 Scenario 1 .................................................................................................................................................102 Table 3.30 - SWWWTP Alkalinity Accounting.....................................................................................................103 Figure 3.20 - Proposed SWWWTP Simplified Process Flow Diagram – Liquid Treatment (Near-Term CIP) ......104 Figure 3.21 - Proposed SWWWTP Simplified Process Flow Diagram – Biosolids Treatment (Near-Term CIP)..104 Figure 3.22 - SWWWTP Scenario 1A, 1B, 1C Simulator Configuration...............................................................105 Figure 3.23 - Proposed SWWWTP Simplified Process Flow Diagram – Biosolids Treatment (Mid-Term CIP) ...107 Table 3.31 – SWWWTP Projected Effluent Quality – Scenario 1A .....................................................................108 Table 3.32 – SWWWTP Projected Effluent Quality – Scenario 1B......................................................................110 Table 3.33 – SWWWTP Projected Effluent Quality – Scenario 1C......................................................................112 3.2.5 Hydraulic Simulator........................................................................................................................................113 3.2.5.1 Hydraulic Modeling Calibration...................................................................................................................113 3.2.5.2 Davidson Dr. WWTP ....................................................................................................................................114 Figure 3.24 - Davidson Dr. Calibration Scenario Hydraulic Simulator Configuration – Upper Reach.................116 Figure 3.25 - Davidson Dr. Calibration Scenario Hydraulic Simulator Configuration – Middle Reach ...............117 Figure 3.26 - Davidson Dr. Calibration Scenario Hydraulic Simulator Configuration – Lower Reach.................118 3.2.5.3 SWWWTP.....................................................................................................................................................119 Figure 3.27 – SWWWTP Calibration Scenario Hydraulic Simulator Configuration – Upper Reach....................120 Figure 3.28 - SWWWTP Calibration Scenario Hydraulic Simulator Configuration – Middle Reach 1.................120 Figure 3.29 - SWWWTP Calibration Scenario Hydraulic Simulator Configuration – Middle Reach 2.................121 Figure 3.30 - SWWWTP Calibration Scenario Hydraulic Simulator Configuration – Lower Reach.....................121 3.2.5.4 Davidson Dr. WWTP Hydraulic Modeling Results .......................................................................................122

Page 5 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 3.31 - Davidson Dr. Existing and Proposed Simplified Process Flow Diagram – Hydraulic Improvements – Overall.................................................................................................................................................................124 Figure 3.32 - Davidson Dr. Existing and Proposed Simplified Process Flow Diagram – Hydraulic Improvements – Area 1..................................................................................................................................................................125 Figure 3.33 - Davidson Dr. Existing and Proposed Simplified Process Flow Diagram – Hydraulic Improvements – Area 2..................................................................................................................................................................128 Figure 3.34 - Davidson Dr. Existing and Proposed Simplified Process Flow Diagram – Hydraulic Improvements – Area 3..................................................................................................................................................................130 Figure 3.35 - Davidson Dr. Existing and Proposed Simplified Process Flow Diagram – Hydraulic Improvements – Area 4..................................................................................................................................................................132 Figure 3.36 - Davidson Dr. Proposed Hydraulic Simulator Configuration – Upper Reach..................................134 Figure 3.37 - Davidson Dr. Proposed Hydraulic Simulator Configuration – Middle Reach 1 .............................135 Figure 3.38 – Davidson Dr. Proposed Hydraulic Simulator Configuration – Middle Reach 2.............................136 Figure 3.39 - Davidson Dr. Proposed Hydraulic Simulator Configuration – Lower Reach..................................137 3.2.5.5 SWWWTP Hydraulic Modeling Results........................................................................................................138 Section 3.3 – Conclusion ................................................................................................................................................139 3.3.1 Capital Improvements Plan Summary ............................................................................................................139 3.3.1.1 Davidson Dr. WWTP ....................................................................................................................................139 Table 3.34 - Proposed Davidson Dr. WWTP Estimated Cost Summary – Near-Term.........................................142 Table 3.35 - Proposed Davidson Dr. WWTP Estimated Cost Summary – Mid-Term..........................................142 Table 3.36 – Proposed Davidson Dr. WWTP Estimated Cost Summary – Long-Term........................................143 Table 3.37 - Proposed Davidson Dr. WWTP Estimated Cost Summary – Long-Term (Beyond Planning Period) ............................................................................................................................................................................144 Table 3.38 – Proposed Davidson Dr. WWTP Estimated Cost Summary - Near, Mid and Long-Terms Total......145 Table 3.39 - Proposed Davidson Dr. WWTP Estimated Cost Summary – Long-Term (Beyond Planning Period) Total....................................................................................................................................................................145 3.3.1.2 SWWWTP.....................................................................................................................................................146 Table 3.40 – Proposed SWWWTP Estimated Cost Summary – Near-Term........................................................147 Table 3.41 – Proposed SWWWTP Estimated Cost Summary – Mid-Term .........................................................147 Table 3.42 – Proposed SWWWTP Estimated Cost Summary - Total ..................................................................148 Chapter 4 – WWTP Unit Process Evaluation.......................................................................................................................149 Section 4.1 – Introduction..............................................................................................................................................149 Section 4.2 – Discussion.................................................................................................................................................150 4.2.1 Davidson Dr. WWTP .......................................................................................................................................150

Page 6 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 4.1 - Existing Davidson Dr. WWTP Simplified Process Flow Diagram – Liquid Treatment......................151 Figure 4.2 - Existing Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment..................152 4.2.1.1 Equalization Pond........................................................................................................................................153 4.2.1.2 Screening .....................................................................................................................................................155 Figure 4.3 – Davidson Dr. WWTP Headworks Screens.......................................................................................155 4.2.1.3 Grit Removal................................................................................................................................................156 Figure 4.4 – Davidson Dr. WWTP Headworks Grit Removal System..................................................................157 4.2.1.4 Primary Clarification ....................................................................................................................................158 Figure 4.5 – Davidson Dr. WWTP Primary Clarifiers...........................................................................................159 4.2.1.5 Aeration.......................................................................................................................................................160 Figure 4.6 – Davidson Dr. WWTP Aeration Basins..............................................................................................160 4.2.1.6 Secondary Clarification................................................................................................................................161 Figure 4.7 – Davidson Dr. WWTP Secondary Clarifiers.......................................................................................162 4.2.1.7 Tertiary Filtration.........................................................................................................................................163 Figure 4.8 – Davidson Dr. WWTP Tertiary Filters...............................................................................................164 4.2.1.8 UV Disinfection............................................................................................................................................165 Figure 4.9 – Davidson Dr. WWTP UV Disinfection..............................................................................................166 4.2.1.9 Gravity Thickening .......................................................................................................................................166 Figure 4.10 – Davidson Dr. WWTP Gravity Thickening.......................................................................................167 4.2.1.10 Anaerobic Digestion ..................................................................................................................................167 Figure 4.11 – Davidson Dr. WWTP Anaerobic Digestion ....................................................................................168 4.2.1.11 Belt Filter Press Dewatering ......................................................................................................................169 Figure 4.12 – Davidson Dr. WWTP Belt Filter Press............................................................................................170 4.2.1.12 Solids Disposal to Landfill or Compost ......................................................................................................171 Figure 4.13 – Davidson Dr. WWTP Biosolids Disposal........................................................................................171 4.2.2 Southwest (SW) WWTP ..................................................................................................................................172 Figure 4.14 - Existing Southwest (SW) WWTP Simplified Process Flow Diagram – Liquid Treatment...............173 Figure 4.15 - Existing SWWWTP Simplified Process Flow Diagram – Biosolids Treatment................................173 4.2.2.1 Screening .....................................................................................................................................................174 Figure 4.16 – SWWWTP Headworks Screen.......................................................................................................174 4.2.2.2 Sequencing Batch Reactor...........................................................................................................................175 Figure 4.17 – SWWWTP Sequencing Batch Reactor...........................................................................................175 4.2.2.3 Tertiary Filtration.........................................................................................................................................176

Page 7 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 4.18 – SWWWTP Tertiary Filtration.........................................................................................................177 4.2.2.4 Step Aeration...............................................................................................................................................177 Figure 4.19 – SWWWTP Step Aeration...............................................................................................................178 4.2.2.5 UV Disinfection............................................................................................................................................178 Figure 4.20 – SWWWTP UV Disinfection............................................................................................................179 4.2.2.6 Step Aeration...............................................................................................................................................179 4.2.2.7 Aerobic Digestion ........................................................................................................................................180 Figure 4.21 – SWWWTP Aerobic Digestion ........................................................................................................181 4.2.2.8 Solids Disposal to Collection System of Davidson Dr. WWTP .....................................................................181 Section 4.3 - Conclusion.................................................................................................................................................182 Chapter 5 – Biosolids Management Evaluation..................................................................................................................183 Section 5.1 – Introduction..............................................................................................................................................183 Figure 5.1 - Existing Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment..................184 Table 5.1 - Existing Davidson Dr. Biosolids – Composting Facility Processing and Storage Capacity.................185 Table 5.2 - Existing Davidson Dr. Biosolids – Composting Facility Cost Analysis................................................186 Table 5.3 - Existing Davidson Dr. Biosolids – Volume and Weight to Landfill ....................................................186 Table 5.4 - Existing Davidson Dr. Biosolids – Landfill Transportation and Tipping Costs...................................186 Section 5.2 – Discussion.................................................................................................................................................188 5.2.1 Final Disposal Options ....................................................................................................................................188 Table 5.5 - Processes that Significantly Reduce Pathogens (PSRP) ....................................................................188 Table 5.6 - Vector Attraction Reduction (VAR) Requirements...........................................................................189 5.2.1.1 Anaerobic Digestion ....................................................................................................................................189 5.2.1.2 Aerobic Digestion ........................................................................................................................................192 Table 5.7 - Davidson Dr. WWTP Aerobic Sludge Handling Biological Performance ...........................................192 5.2.1.3 Alkaline Stabilization ...................................................................................................................................192 Table 5.8 - Processes to Further Reduce Pathogens (PFRP)...............................................................................193 Table 5.9 - Land Application Restrictions for Class B Biosolids...........................................................................195 5.2.2 Alternatives Considered for Disposal .............................................................................................................196 Table 5.10 - Biosolids Disposal Alternatives for Hot Springs WWTPs.................................................................196 Table 5.11 - Biosolids Disposal Alternatives Comparison for Davidson Dr. WWTP – Drying .............................197 Table 5.12 - Biosolids Disposal Alternatives Comparison for Davidson Dr. WWTP – Composting ....................198 Table 5.13 - Biosolids Disposal Alternatives Comparison for Davidson Dr. WWTP – Land Application.............199 Table 5.14 - Biosolids Disposal Alternatives Comparison for Davidson Dr. WWTP – Landfill ............................200

Page 8 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 5.2 – Hot Springs, AR Surrounding Arial Google Image...........................................................................203 Figure 5.3 – Active Class 1 and Class 4 Landfills in Arkansas (2019v).................................................................205 5.2.3 Davidson Dr. WWTP Analysis .........................................................................................................................206 5.2.3.1 Scenario 1A..................................................................................................................................................206 Figure 5.4 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Solids Treatment (Near-Term CIP)......................................................................................................................................................................208 Table 5.15 – Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Near-Term – Scenario 1A ............................................................................................................................................................................209 5.2.3.1.1 Drying .......................................................................................................................................................210 5.2.3.1.2 Composting...............................................................................................................................................210 Table 5.16 - Proposed Davidson Dr. Biosolids – Scenario 1A – Existing Composting Costs Analysis.................210 5.2.3.1.3 Land Application.......................................................................................................................................210 5.2.3.1.4 Landfill ......................................................................................................................................................211 Figure 5.5 – 20 CY Trailer and Heavy Haul Tractor Example ..............................................................................211 Table 5.17 - Proposed Davidson Dr. Biosolids – Scenario 1A – Landfill Costs Analysis......................................212 5.2.3.2 Scenario 1A (Alternative A) .........................................................................................................................213 Figure 5.6 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Biosolids Treatment (Near-Term CIP) – Scenario 1A (Alternative A) .....................................................................................................................214 Table 5.18 – Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Near-Term – Scenario 1A (Alternative A).....................................................................................................................................................215 5.2.3.2.1 Drying .......................................................................................................................................................216 5.2.3.2.2 Composting...............................................................................................................................................216 Table 5.19 - Proposed Davidson Dr. Biosolids – Scenario 1A (Alternative A)– Existing Composting Costs Analysis ............................................................................................................................................................................216 5.2.3.2.3 Land Application.......................................................................................................................................216 5.2.3.2.4 Landfill ......................................................................................................................................................217 Table 5.20 - Proposed Davidson Dr. Biosolids – Scenario 1A (Alternative A)– Landfill Costs Analysis...............217 5.2.3.3 Scenario 2A1................................................................................................................................................218 Figure 5.7 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Mid-Term – Scenario 2A1......220 Table 5.21 - Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Mid-Term – Scenario 2A1 ............................................................................................................................................................................221 5.2.3.4 Scenario 2A1 (Alternative B)........................................................................................................................222 Figure 5.8 - Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Mid-Term – Scenario 2A1 (Alternative B).....................................................................................................................................................224 5.2.3.4.1 Drying .......................................................................................................................................................225

Page 9 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 5.9 – Municipal Biosolids Dryer Example 1..............................................................................................225 Figure 5.10 – Municipal Biosolids Dryer Example 2............................................................................................226 Table 5.22 – Proposed Davidson Dr. Biosolids – Scenario 2A1 (Alternative B)– Drying Costs Analysis.............227 5.2.3.4.2 Composting...............................................................................................................................................227 Figure 5.11 – Compost Windrow Turner Example..............................................................................................228 Table 5.23 - Proposed Davidson Dr. Biosolids – Scenario 2A1 – Compost (Windrow) Impervious Area Calculations.........................................................................................................................................................229 Table 5.24 - Proposed Davidson Dr. Biosolids – Scenario 2A1 – Composting (Windrow) Costs Analysis..........230 Figure 5.12 – Rotary Drum In-Vessel Compost Example....................................................................................231 Table 5.25 - Proposed Davidson Dr. Biosolids – Scenario 2A1 – Compost (Rotary Drum/ Windrow) Impervious Area Calculations................................................................................................................................................232 Table 5.26 - Proposed Davidson Dr. Biosolids – Scenario 2A1 – Composting (Rotary Drum/ Windrow) Costs Analysis...............................................................................................................................................................233 5.2.3.5 Scenario 2A1 (Alternative C)........................................................................................................................234 Figure 5.13 – Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Mid-Term – Scenario 2A1 (Alternative C) – Aerobic Digestion ....................................................................................................................236 Table 5.27 – Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Mid-Term – Scenario 2A1 (Alternative C) – Aerobic Digestion .............................................................................................................237 5.2.3.5.1 Land Application.......................................................................................................................................238 Figure 5.14 – Agricultural Corn T-N Uptake Example.........................................................................................239 Table 5.28 – Proposed Davidson Dr. WWTP Biosolids Land Application Area...................................................240 Figure 5.15 – Front End Loader Example............................................................................................................241 Figure 5.16 – Biosolids Loading Conveyor, Farm Tractor and Spreader Example..............................................242 Table 5.29 – Proposed Davidson Dr. Biosolids – Scenario 2A1 (Alternative C) – Land Application Costs Analysis ............................................................................................................................................................................243 5.2.3.5.2 Landfill ......................................................................................................................................................243 Table 5.30 – Proposed Davidson Dr. Biosolids – Scenario 2A1 – Landfill Costs Analysis ...................................244 Table 5.31 – Proposed Davidson Dr. WWTP Biosolids Estimated Cost Unit Quick Summary ............................244 5.2.3.6 Scenario 3A..................................................................................................................................................245 Figure 5.17 – Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Beyond Planning Period – Long-Term – Scenario 3A.................................................................................................................................248 Table 5.32 – Proposed Davidson Dr. WWTP Biosolids Production Planning Summary – Beyond Planning Period – Long-Term – Scenario 3A.................................................................................................................................249 Table 5.33 – Proposed Davidson Dr. WWTP Biosolids Estimated Cost Summary..............................................251 Table 5.33 – Proposed Davidson Dr. WWTP Biosolids Estimated Cost Summary (cont.) ..................................252

Page 10 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 5.33 – Proposed Davidson Dr. WWTP Biosolids Estimated Cost Summary (cont.) ..................................253 5.2.4 SWWWTP Analysis..........................................................................................................................................254 5.2.4.1 Scenario 1A..................................................................................................................................................254 Figure 5.18 – Proposed SWWWTP Simplified Process Flow Diagram – Solids Treatment (Near-Term CIP)......255 Figure 5.19 – Proposed SWWWTP Simplified Process Flow Diagram – Solids Treatment (Mid-Term CIP) .......255 Table 5.34 – Proposed SWWWTP Biosolids Production Planning Summary – Near/ Mid-Term – Scenario 1A.256 Table 5.35 – Proposed SWWWTP Biosolids – Scenario 1A – Davidson Dr. WWTP Disposal Costs Analysis......257 5.2.5 Biosolids Processing – Thickening ..................................................................................................................258 5.2.5.1 Gravity Thickener.........................................................................................................................................259 Figure 5.20 – Gravity Thickener..........................................................................................................................259 5.2.5.2 Floatation Thickening ..................................................................................................................................259 Figure 5.21 – Floatation Thickener.....................................................................................................................260 5.2.5.3 Gravity Belt Thickening................................................................................................................................261 Figure 5.22 – Gravity Belt Thickener...................................................................................................................261 5.2.5.4 Rotary Drum Thickening ..............................................................................................................................262 Figure 5.23 – Rotary Drum Thickening ...............................................................................................................262 5.2.5.5 Centrifugal Thickening.................................................................................................................................263 Figure 5.24 – Centrifugal Thickener....................................................................................................................263 5.2.5.6 Aerated Sludge Storage...............................................................................................................................264 Figure 5.25 – Decanter .......................................................................................................................................265 5.2.6 Biosolids Processing –Dewatering..................................................................................................................266 5.2.6.1 Belt Filter Press............................................................................................................................................266 Figure 5.26 – Belt Filter Press Dewatering .........................................................................................................267 5.2.6.2 Screw Press..................................................................................................................................................267 Figure 5.27 – Screw Press Dewatering ...............................................................................................................268 5.2.6.3 Centrifugal Dewatering................................................................................................................................268 Figure 5.28 – Centrifugal Dewatering.................................................................................................................269 5.2.7 Biosolids Processing Sidestream Treatment ..................................................................................................269 Table 5.36 – Davidson Dr. WWTP Projected Effluent Quality and T-P Removal Example Analysis ...................270 Figure 5.29 – Suspended Air Flotation (SAF) ......................................................................................................272 Figure 5.30 – Proposed Davidson Dr. WWTP Simplified Process Flow Diagram – Mid-Term – Scenario 2A1 – Zoomed In...........................................................................................................................................................273 Table 5.37 – Davidson Dr. WWTP Sidestream Treatment System Cost Analysis...............................................274

Page 11 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Section 5.3 – Conclusion ................................................................................................................................................275 5.3.1 Davidson Dr. WWTP .......................................................................................................................................275 5.3.2 SWWWTP........................................................................................................................................................276 Chapter 6 – Control Environmental Laboratory and Maintenance Building(s) Evaluation ................................................277 Section 6.1 - Introduction ..............................................................................................................................................277 Section 6.2 – Discussion.................................................................................................................................................278 6.2.1 Davidson Dr. WWTP .......................................................................................................................................278 6.2.2 Southwest (SW) WWTP ..................................................................................................................................278 Section 6.3 - Conclusion.................................................................................................................................................279 Chapter 7 – Major Lift Stations and Force Mains Evaluation .............................................................................................280 Section 7.1 – Introduction..............................................................................................................................................280 Section 7.2 – Discussion.................................................................................................................................................281 7.2.1 Evaluations .....................................................................................................................................................281 7.2.2 Improvements ................................................................................................................................................281 7.2.3 Consolidation and Elimination........................................................................................................................282 7.2.4 Rating..............................................................................................................................................................283 7.2.5 Force Mains....................................................................................................................................................283 Section 7.3 – Conclusion ................................................................................................................................................284 Table 7.1 – City of Hot Springs Force Mains – Cost Summary............................................................................284 Table 7.2 – City of Hot Springs Major Lift Stations – Cost Summary..................................................................284 Chapter 8 – Collection System and Minor Lift Stations......................................................................................................286 Section 8.1 – Introduction..............................................................................................................................................286 Section 8.2 – Discussion.................................................................................................................................................287 SECAP.......................................................................................................................................................................287 Section 8.3 – Conclusion ................................................................................................................................................288 8.3.1 Lift Stations and Force Mains.........................................................................................................................288 8.3.2 Gravity Mains and Manholes..........................................................................................................................289 Table 8.1 – Proposed Collection System Estimated Cost Summary – Near-Term..............................................289 Table 8.2 – Proposed Collection System Estimated Cost Summary – Mid-Term...............................................290 Table 8.3 – Proposed Collection System Estimated Cost Summary – Long-Term..............................................290 Table 8.4 – City of Hot Springs Collection System – Cost Summary...................................................................290 8.3.3 Minor Lift Stations..........................................................................................................................................291 Table 8.5 – Proposed Minor Lift Stations Estimated Annual Cost Summary......................................................291

Page 12 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Appendices in Volume 2 1 – AR0033880 Davidson Plant 1a – 1923 Preliminary Discharge Limits 20190823 2 – AR0050148 SWWWTP 3 – Davidson Drive WWTP Master Plan 4 – Hot Springs Draft Flow Monitoring Report 5 – Tech Memo – Hot Springs Future Growth 6 – Tech Memo – Hot Springs Sewerage Master Plan 7 – Tech Memo – Hot Springs Sewerage Master Plan, Additional Analysis 8 – Chelsea Street Flow Monitoring Final Report 9 – Hot Springs Creek Flow Monitoring Final Report 10 – City of Hot Springs Typical Lift Station Details 11 – 2018 (2) HP Duplex Pump Stations 12 – 2018 (5-10) HP Duplex Pump Stations 13 – City of Hot Springs 2010 SECAP Status Update 14 – Tech Memo – Update on SECAP Projects for SSO Removal 15 – Tech Memo – Hot Springs Rainfall Monitoring along with SSO Comparison 16 – Tech Memo – System Wide Flow Monitoring, Model Calibration, and Model Update

Page 13 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. WASTEWATER SYSTEM MASTER PLAN City of Hot Springs, Arkansas May 2022 CHAPTER 1 – PROJECT OBJECTIVES AND GOALS SECTION 1.1 - INTRODUCTION Hot Springs is the 11th largest city in Arkansas and covers more than 22,000 acres (35 square miles). The City has a wastewater service area limited to mostly within the city limits but does provide service outside the city limits on the South and West sides of Lake Hamilton. The Utilities Department is responsible for collection and treatment of wastewater generated by the service area. The existing wastewater collection and treatment system consists of approximately 874 miles of collection system piping, access manholes, major lift stations, minor lift stations, one equalization basin, two (2) Arkansas Department of Energy and Environment (ADEE), formally Arkansas Department of Environmental Quality, permitted wastewater treatment plants with their corresponding outfalls, and one (1) biosolids composting facility. CHS and the ADEE executed a Consent Administrative Order (CAO) in 2011 (initiated in 2008) which resulted in an investment of approximately $70 million dollars in the wastewater collection system in recent years. The majority of these funds were used to address infrastructure needs that minimized the number and duration of associated sanitary sewer overflows (SSOs). In 2022 the ADEE and CHS executed an amendment to these existing CAO that addresses Gulpha basin SSOs. Also in 2022 ADEE and CHS executed a CAO related to the Davidson Dr. WWTP that addresses discharge permit excursions from this wastewater treatment plant. CHS intends to have the majority of the near-term capital improvements focus on the Gulpha basin and Davidson Dr. WWTP while continuing to rehabilitate the collection system in other areas. Through initial investigations and discussions conducted since 2019, Crist Engineers, Inc. agrees with this approach. Initial discussions with staff indicate minimal needed improvement at the Southwest (SW) WWTP. The SW WWTP current estimated average annual flow rate is 0.404 MGD which is approximately 47% of the original design treatment capacity of 0.85 MGD. However, biosolids handling was not installed during original construction. Also, there are operational concerns related to alkalinity adjustment to ensure proper nitrification during treatment. The SW WWTP construction was completed in 2012. Davidson Dr. WWTP current estimated average annual flow rate is 12.04 MGD or 100% of the original design treatment capacity. Major capital improvements were completed in 2018 to the screening, grit removal and UV disinfection. Another major capital improvement was completed in 2022 that installed new tertiary filters. Challenges currently exist with the chemical addition and biosolids management process. Other issues have arisen with the diffused aeration and blowers related to the aeration basin. Chemical additional, specifically

Page 14 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. the lime feed system, is also in need of repair. The last major complete upgrade to the Davidson Dr. WWTP was completed in 1992. SECTION 1.2 - DISCUSSION Crist Engineers, Inc. was tasked with development of the CHS Wastewater System Master Plan (WWSMP). Some of the tasks that were completed during this initial phase are identified as follows: 1. An initial table of contents for the final WWSMP was developed to assist in the expectations of the WWSMP. 2. Progress meetings were held monthly with minutes distributed to each attendee thereafter. 3. Facility tours were held to determine the initial needs of the Southwest and Davidson Dr. WWTPs. SECTION 1.3 – CONCLUSION This phase of the WWSMP and corresponding technical memorandum assembled by the project team, reviewed pertinent reports, conducted initial asset investigations, and developed the initial WWSMP expectations.

Page 15 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. CHAPTER 2 – INITIAL PLANNING AND EVALUATION CRITERIA SECTION 2.1 – INTRODUCTION The development of the City of Hot Springs (CHS) Wastewater System Master Plan (WWSMP) is intended to establish criteria to be used as the basis for the proposed Capital Improvements Plan (CIP). These benchmarks impact project execution (risk, scope, budget, and schedule) and success. It is critical to develop planning and evaluation criteria initially while still being able to revisit these parameters as information becomes available and is analyzed. It is critical to develop initial criteria related to service area, planning period, flows, loadings, capacities, and other identified parameters. Currently, as of 2022, there are 26,828 wastewater connections within the CHS service area. Of those connections approximately 90% are residential type connections. The majority of existing sewer connections (64%) are within city limits. Table 2.1 – Wastewater Connections Summary (2022) Connection Type Inside City Limits Outside City Limits Connections Residential 14,709 9,301 24,010 Commercial 2,359 450 2,809 Industrial 3 6 9 Total 17,071 9,757 26,828 Similar to the Water Master Plan, developed by Crist Engineers, Inc., it was proposed to utilize a 1% growth rate for determination of future projected influent flow rates. The proposed growth service area was established by RJN Group, Inc. in 2016 and presented in Appendix 6.

Page 16 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Figure 2.1 – 2040 CHS Growth Service Area The areas that were expected to experience most of the sewer growth by 2040 are region 8, 13, 15, 16 and 21. The combined total of these 5 regions are anticipated to represent over 57% of the sewer connection growth. The remaining sewer connection growth (~43%) is anticipated to be approximately distributed equally among the 16 regions.

Page 17 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. SECTION 2.2 - DISCUSSION Crist Engineers contacted the ADEE to ascertain future water quality standards and projections related to the NPDES Discharge Permits for Southwest (SW) and Davidson Dr. Wastewater Treatment Plants (WWTP). A preliminary effluent discharge determination for Davidson Dr. WWTP is included as an attachment in the Appendix 1a. SW WWTP is currently in the process of a permit renewal. It appears that T-P effluent limitation will not be included in the next NPDES permit term and will include no modifications to the existing effluent limitations. 2.2.1 EFFLUENT LIMITS The NPDES effluent limitations for SW WWTP are presented in Table 2.2. The critical parameter for design consideration is April ammonia limits. SW WWTP experiences low water temperatures reducing biological activity while the effluent ammonia is reduced by 13%. For the information currently available for April, only 13 total data points exist. Additional ammonia information will be collected and developed as the WWSMP project continues.

Page 18 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 2.2 – SW WWTP NPDES Effluent Limit Summary 2015 to 2020 Permit Limits 2020 to 2025 Permit Limits Planning Permit Limits cBOD (mg/L) May to October 5 5 5 November to March 10 10 10 TSS (mg/L) 15 15 15 Ammonia (as N) (mg/L) April 5.2 5.2 5.2 May to October 2 2 2 November to March 6 6 6 Total P (as-P) (mg/L) - - - Nitrate (as-N) (mg/L) - - - Nitrite (as-N) (mg/L) - - - Nitrate + Nitrite (asN) (mg/L) - - pH 6 6 6 Dissolved Oxygen (mg/L) May to October 7 7 7 November to March 6 6 6 Fecal Coliform (colonies/ 100 mL) May to September 200 200 200 October to April 1000 1000 1000 The complete SW WWTP NPDES permit (AR0050148) provided within Appendix 2.

Page 19 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 2.3 – SW WWTP NPDES Effluent Active Permit Periods Active Permit Periods Renewal Year Lead Up June 1, 2020 to May 31, 2025 2024 June 1, 2025 to May 31, 2030 2029 June 1, 2030 to May 31, 2035 2034 June 1, 2035 to May 31, 2040 2039 June 1, 2040 to May 31, 2045 2044 If the daily discharge flow from Davidson Dr. WWTP is in excess of 16 MGD Entergy may impose a fine to CHS in accordance with their agreement. The limit has created flow balancing and discharge challenges for Regional WWTP during high flow time periods which have led to unnecessary operational modifications that impact effluent quality. It has been proposed that the Entergy agreement be updated to more accurately reflect the quality limits (mass/ concentration) imposed by the NPDES Permit (as currently referenced in that agreement) in lieu of flow which is not regulated by ADEE. CHS and Entergy discussions will be held to address this agreement in the near future. In the interim, CHS directed Crist Engineers to continue the WWSMP and corresponding evaluation as if this limitation will not be an issue into the future. The NPDES effluent limitations for Davidson Dr. WWTP are presented in Table 2.4. The critical parameter for design considerations is April ammonia limits. As with SW WWTP, this is when Davidson Dr. WWTP experiences low water temperatures and the effluent ammonia is reduced by 64%.

Page 20 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. Table 2.4 – Davidson Dr. WWTP NPDES Effluent Limit Summary 2018 to 2023 Permit Limits Planning Permit Limits cBOD (mg/L) 10 10 TSS (mg/L) 15 15 Ammonia (as N) (mg/L) April 3.6 4.1 May to October 3.6 3.6 November to March 10 10 Total P (as-P) (mg/L) 1 0.7 Nitrate (as-N) (mg/L) - - Nitrite (as-N) (mg/L) - - Nitrate + Nitrite (as-N) (mg/L) - - pH 6 6 Dissolved Oxygen (mg/L) January to December 5 - May to October - 5 November to March - 5.6 Fecal Coliform (colonies/ 100 mL) May to September 200 200 October to April 1000 1000 The complete Davidson Dr. WWTP NPDES permit (AR0033880) provided within Appendix 1. Table 2.5 – Davidson Dr. WWTP NPDES Effluent Active Permit Periods Active Permit Periods Renewal Year Lead Up September 1, 2018 to August 31, 2023 2022 September 1, 2023 to August 31, 2028 2027 September 1, 2028 to August 31, 2033 2032 September 1, 2033 to August 31, 2038 2037 September 1, 2038 to August 31, 2043 2042

Page 21 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. 2.2.2 INFLUENT QUALITY Limited information exists related to SW WWTP influent quality. However, it is believed that the influent quality is similar to Davidson Dr WWTP. However, it is suspected that the influent ammonia may have peaks of ammonia into the 40 to 60 mg/L range. Additionally, it appears that influent alkalinity can be low at times. Additional testing and information will be gathered to expand the data set. A summary of the influent parameters is identified in Table 2.6. Table 2.6 – Influent Parameters Parameters 2019 Average Annual 2015 Max Month 2015 Average Month 1992 Design 2040 Design mg/L cBOD 164 165 166 122 164 VSS 120.581 114.1 114.1 103.6 120.58 TSS 172.26 163 163 148 172.26 TKN 21.821 18.79 20.76 14.99 21.82 Ammonia (as N) 14.4 12.4 13.7 9.89 14.4 Total P (as-P) 3.8 3.2 3.7 4.99 3.8 Nitrate (as-N) 0 0 0 0 0 pH 6.57 6.57 6.57 6.57 6.57 Alkalinity 1251 125 125 125 162.52 Calcium 30 30 30 30 30 Magnesium 10 10 10 10 13 Dissolved Oxygen 0 0 0 0 0 1 Limited information available, engineering judgement used to develop values. These values will be confirmed with future testing. 2 Supplemental alkalinity is likely needed, additional testing to confirm. As discussed, April effluent ammonia is the critical design parameter. Influent ammonia must be known for proposed biological modeling which results may suggest possible upgrades. As of 2019 for Davidson Dr. WWTP, only 15 total data points exist for April. Historically, Davidson Dr. WWTP has taken weekly samples. Sampling frequency has been proposed to increase and is recommended to increase to daily during the month of April. Additional ammonia information will be collected and developed as the WWSMP project continues. Throughout this ongoing process it is important to develop initial criteria related to service area, planning period, flows, loadings, capacities, and other identified parameters.

Page 22 of 291 Wastewater System Master Plan (WWSMP) – Hot Springs, Arkansas | Crist Engineers, Inc. 2.2.3 INFLUENT FLOW The current estimated flow rate is based on 2018 end of the year flow rate. The estimated SW WWTP influent flows are presented in Table 2.7. Table 2.7 – SW WWTP Influent Flow Summary Parameters 2010 Design Flow 0.85 MGD Current Est. Average Daily Flow 0.404 2025 Average Day Flow (1% growth rate; end of year) 0.433 2040 Average Day Flow (1% growth rate; end of year) 0.503 2040 Design Flow (Preliminary) 0.85 Unless significant development occurs within the drainage base for SW WWTP, it is anticipated that the 2040 influent flow rate will be approximately 59% of the design capacity. The estimated Davidson Dr. WWTP influent flows are presented in Table 2.8. Table 2.8 – Davidson Dr. WWTP Influent Flow Summary Parameters 1992 Design Flow 12 MGD Current Est. Average Daily Flow 12.04 2040 Average Day Flow (2015 Report) 14.5 2040 Design Flow (2015 Report) 23.1 2025 Average Day Flow 12.9 2025 Design Flow 14 2040 Average Day Flow (1% growth rate) 14.98 2040 Design Flow (Preliminary) 16.26 CHS has recently completed extensive collection system work that will have an impact on influent flows. It is recommended that additional influent flow data be collected, evaluated and updated through 2025 to be used for flow projections through 2040. This new updated information can be used to develop the peak day hydraulic needs of Davidson Dr. and SW WWTPs. 2.2.4 SERVICE AREA The existing service area was identified in the 2016 Technical Memorandum and presented in Appendix 6 developed by RJN Group, Inc. There are no current identified plans to update or modify the existing service area.