Selma Estates Raspberry Falls (Gpd) 1 4.2 Gpm for 2Hrs 500 577 423 2 2.1 Gpm for 4Hrs 500 289 211.5 Notes: 1

Raspberry Falls and Selma Estates Community Water Systems Study of Long Term Options

January 2015

Table of Contents Executive Summary ...... 1 1.0 Background ...... 5 1.1 Study Area ...... 5 1.2 Water Sources and Previous Studies ...... 5 1.2.1 Water Supply Sources ...... 5 1.2.2 Previous Studies ...... 9 1.3 General Regulatory Requirements ...... 11 1.3.1 Sampling and Treatment ...... 11 1.3.2 Annual Withdrawal Reporting ...... 12 1.4 Purpose of the Study of Long‐Term Water Supply Options ...... 12 2.0 Water Demands and Supply ...... 15 2.1 Water Connections, Flow Rates, and Total Demand ...... 15 2.2 Comparison of Water Supply Needs and Availability ...... 16 3.0 Water Treatment, Storage and Distribution ...... 19 3.1 Membrane Filtration ...... 19 3.1.1 Membrane Filtration Overview ...... 19 3.1.2 Raspberry Falls / Selma Estates Combined Membrane Facility Concepts ...... 19 3.1.3 Membrane Cleaning ...... 21 3.1.4 Waste Flows ...... 23 3.1.5 Treatment Chemical Requirements ...... 26 3.2 Granular Activated Carbon (GAC) ...... 29 3.2.1 GAC Contactor Configuration...... 29 3.2.2 GAC Contactor Size ...... 29 3.3 Finished Water Storage ...... 30 3.4 Irrigation Storage ...... 33 3.4 Water Distribution ...... 34 3.4.1 Hydraulic Modeling and Design Data ...... 34 3.4.2 Treated Water Distribution ...... 35 3.4.3 Irrigation Water Distribution ...... 39 4.0 Summary of Treatment and Distribution System Concepts ...... 41

4.1 Supply and Treatment Option No. 1: Combined Potable Water Treatment with Separate Irrigation...... 41 4.2 Supply and Treatment Option No. 2: Combined Mixed Use Water Treatment ...... 42 4.3 Preliminary Cost Estimates ...... 43 5.0 Triple‐Bottom Line Sustainability Analysis – Financial, Social and Environmental ...... 45 5.1 Introduction ...... 45 5.2 Criteria, Scoring and Weighting ...... 45 5.3 Evaluation using Economic Criteria ...... 46 5.4 Evaluation using Environmental Criteria ...... 47 5.4.1 Impact on Carbon Emissions ...... 47 5.4.2 Impact on Aquifer Sustainability ...... 48 5.5 Evaluation using Social Criteria ...... 49 5.5.1 Public Health ...... 49 5.5.2 Quality of Life ...... 50 5.6 Summary of Triple Bottom Line Analysis of the Water Supply and Treatment Options ...... 50 5.7 Treatment Option Recommendation ...... 51

List of Tables

Table ES.1: Comparison of Selma Estates Well Capacity to Potable Water Needs ...... p. 2 Table ES.2: Summary of Criteria Scoring for the Two Water Supply and Treatment Options ...... p. 4 Table 1.1: Raspberry Falls Community System: Aquifer Characteristics and Well Construction Records p. 6 Table 1.2: Summary of Raw Water Quality Parameters for Raspberry Falls ...... p. 7 Table 1.3: Aquifer Characteristics and Well Construction Records for Selma Estates ...... p. 8 Table 1.4: Summary of Raw Water Quality Parameters for Selma Estates ...... p. 9 Table 2.1: Supply and Treatment Option 1 ‐ Potable Water Demands for Raspberry Falls and Selma Estates ...... p. 15 Table 2.2: Supply and Treatment Option 1 ‐ Irrigation Demands for Raspberry Falls and Selma Estates ...... p. 16 Table 2.3: Supply and Treatment Option 2 ‐ Mixed Use Water Demands for Raspberry Falls and Selma Estates ...... p. 16 Table 2.4: Comparison of Selma Estates Well Capacity to Potable Water Needs ...... p. 16 Table 3.1: Membrane Sizing Parameters ...... p. 20 Table 3.2: Typical Membrane Cleaning Chemicals ...... p. 22

Table 3.3: Treatment Option 1 Waste Flow Volumes and Rates ...... p. 24 Table 3.4: Treatment Option 2 Waste Flow Volumes and Rates ...... p. 25 Table 3.5: Membrane Cleaning Processes Frequencies and Associated Chemical Constituents ...... p. 26 Table 3.6: Maximum Waste Stream Chemical Loads – Citric Acid ...... p. 27 Table 3.7: Maximum Waste Stream Chemical Loads – Chlorine ...... p. 27 Table 3.8: Maximum Waste Stream Chemical Loads – Caustic ...... p. 28 Table 3.9: Preliminary GAC Design Summary ...... p. 30 Table 3.10: Supply and Treatment Option No. 1 Potable Water Storage Tank Requirements ...... p. 32 Table 3.11: Supply and Treatment Option No. 2 Potable Water Storage Tank Requirements ...... p. 33 Table 3.12: Supply and Treatment Option No. 1 Non‐Potable Water Storage Tank Requirements ...... p. 33 Table 3.13: Supply and Treatment Option 1 Total Potable Water Demands and System Design Criteria ...... p. 34 Table 3.14: Supply and Treatment Option 1 Total Irrigation Demand and System Design Criteria ...... p. 35 Table 3.15: Supply and Treatment Option 2 Mixed Use Water Demands and System Design Criteria . p. 35 Table 3.16: Supply and Treatment Option No. 1 ‐ Irrigation Alternatives ...... p. 39 Table 3.17: Supply and Treatment Option No. 1 ‐ Irrigation Pipe Summary ...... p. 39 Table 3.18: Supply and Treatment Option No. 1 ‐ Irrigation Pump Summary ...... p. 40 Table 4.1: Supply and Treatment Option No. 1 System Capacities ...... p. 41 Table 4.2: Supply and Treatment Option No. 1 ‐ Major Treatment and Distribution Components ...... p. 42 Table 4.3: Supply and Treatment Option No. 2 System Capacity ...... p. 43 Table 4.4: Supply and Treatment Option No. 2 ‐ Major Treatment and Distribution Components ...... p. 43 Table 4.5: Capital Cost Summary ...... p. 44 Table 5.1: Triple Bottom Line Analysis Criteria ...... p. 46 Table 5.2: Table 5.2: Estimated Costs of Water Supply and Treatment Options ...... p. 47 Table 5.3: Estimated Kilograms of Carbon Dioxide Equivalents Generated Annually by Each Option... p. 48 Table 5.4: Summary of Criteria Scoring for the Two Water Supply and Treatment Options ...... p. 51

List of Figures

Figure 1.1: Selma Estates and Raspberry Falls Study Area ...... following p. 6 Figure 1.2: Existing Water Supply Well Locations ...... following p. 8 Figure 2.1: Well Supply for STO2 ...... following p. 18 Figure 2.2: Well Supply for STO1 ...... following p. 18 Figure 3.1: Membrane Treatment Process Schematic ...... following p. 22

iii

Figure 3.2: Supply and Treatment Option No. 1, Performance of Existing Selma Estates Pumps with New VFDs ...... p. 36 Figure 3.3: Supply and Treatment Option No. 2, Performance of Existing Selma Estates Pumps with New VFDs ...... p. 37 Figure 3.4: Supply and Treatment Option No. 1, Performance of New Selma Estates Pumps ...... p. 38 Figure 3.5: Supply and Treatment Option No. 2, Performance of New Selma Estates Pumps ...... p. 38 Figure 4.1: Treatment Option 1 Layout (400 gpd/connection)...... following p. 42 Figure 4.2: Treatment Option 2 Layout Option2 (900 gpd/connection) ...... following p. 44

Abbreviations

American Water Works Association AWWA Annual Water Withdrawal Reporting Regulation AWWR Average Day Demand ADD Backwash BW Below Detection Limit BDL Calcium Carbonate CaCO3 Caustic NaOH Chlorine Gas Cl2 Citric Acid C6H8O7 Clean‐In‐Place CIP Emery & Garrett Groundwater, Inc. EGGI Empty Bed Contact Time EBCT Engineering Design Manual EDM Equivalent Residential Connections ERCs Forward Flush FF Granular Activated Carbon GAC Groundwater Under The Direct Influence Of Surface Water GUDI Hydraulic Grade Line HGL Hydrochloric Acid HCl Hydrogen Peroxide H2O2 Irrigation Storage Tanks IST Loudoun Water Community Systems Department ComSys Maintenance Clean MC Maximum Daily Demand MDD Office Of Public Water Supply OPWS Peak Hour Demand PHR Pounds lbs Preliminary Engineering Report PER Pressure Regulating Valve PRV Raspberry Falls Community System RFCS Secondary Maximum Contaminant Levels SMCL Selma Estates Community System SECS Sodium Hypochlorite NaOCl Supply and Treatment Option 1 STO1 Supply and Treatment Option 2 STO2 Synthetic Organic Compounds SOCs The Insurance Services Office, Inc. ISO Total Dynamic Head TDH Transmembrane Pressure TMP Variable Frequency Drives VFDs Virginia Department Of Environmental VADEQ Virginia Department Of Health VDH Virginia Department Of Health Waterworks Regulations VDHWWR Volatile Organic Compounds VOCs Wastewater Treatment Plant WWTP v

Units

Conductivity mohm/cm Cubic feet Ft3, cf Fahrenheit °F Foot ‘, ft Gallon Gal Gallons per day gpd Gallons per minute Gpm gallons/square foot/day gfd, gal/sf/day Horse power HP Hours Hrs Inch “, in Microgram/liter µg/L Milligram/liter mg/L Minute Min Nephelometric Turbidity Units NTU Pounds lbs Pounds per inch Psi

Raspberry Falls and Selma Estates Study of Long Term Options January 6, 2015

Executive Summary

Study Area and Background The neighboring communities of Raspberry Falls and Selma Estates are located in Loudoun County, VA. Two separate water treatment facilities currently exist to serve each community. Though originally built by developers, both systems are currently owned and operated by Loudoun Water. Raw water for each community is obtained from a series of groundwater wells. Once withdrawn, the raw water is treated and distributed for consumption.

In November of 2010, elevated levels of total coliform and E. coli bacteria were discovered in one of the raw water supply wells (PW‐1) serving Raspberry Falls. As a result of a detailed evaluation, the Virginia Department of Health (VDH) reclassified the well as groundwater under the direct influence of surface water (GUDI). GUDI wells pull from water sources that do not benefit from geological percolation and natural filtration. Treatment standards for GUDI sources require engineered filtration; the Raspberry Falls Water Treatment Facility was not designed to provide GUDI treatment. Therefore, Loudoun Water discontinued the use of the GUDI well and installed a new Raspberry Falls well (Well RSP‐F). The new well serves as a redundant duty well and allows Loudoun Water to maintain a permitted source water supply of over 139,200 gpd.

In October 2013, Selma Well 7E2 was removed from service for a GUDI Evaluation. It was returned to service in December 2013 when VDH concluded that it was not GUDI. During this time, the water demand of the Selma community was met by the remaining wells.

In May and June of 2014, elevated levels of bacteria were detected in multiple wells in both communities, and VDH GUDI evaluations were triggered and initiated for Raspberry Falls Well PW‐2 and Selma Estates Well 7E2 and Well 9F. To date, these GUDI evaluations are ongoing and these wells have not been determined to be GUDI1. However, the detection of elevated levels of bacteria in multiple wells in both communities during the same short timeframe represents a demonstrated risk to the sustainability of the current water treatment practices for both communities.

The 2014 bacteriological presence event spanning both communities triggered Loudoun Water to re‐ evaluate the future long term water treatment needs of the Selma Estates and Raspberry Falls communities. After performing a preliminary screening of potential supply and treatment options, Loudoun Water directed Hazen and Sawyer to further analyze the two most promising options as outlined in the October 10, 2014 Hazen and Sawyer Memorandum that center around providing 900 gpd per connection as historically seen over the past 6 years. These options are:

 Supply and Treatment Option 1: Construct a single water treatment plant at Selma Estates to serve both communities. The combined treatment facility will be sized to treat and supply 400 gpd per connection of potable water for domestic use. This option also includes the construction of two separate irrigation supply systems, one for each community, sized to supply 500 gpd per connection of untreated groundwater for irrigation use only.

 Supply and Treatment Option 2: Construct a single water treatment plant located at Selma Estates to serve all of the water needs of both communities. The plant would be sized based on the maximum usage observed over the past 6 years, i.e., 900 gpd per connection.

1 Well PW‐2 was determined by VDH not to be GUDI in late 2014. 1

The existing Selma Estates treatment facility location was chosen for further development over the Raspberry Falls location as land is available at Selma Estates for the new treatment facility and as the Selma site is more suitable for water distribution since it is located at a higher elevation than Raspberry Falls.

Comparison of Water Supply Sources, Needs and Availability The water supply sources and needs per source differ for each long term supply and treatment option being considered. Under Supply and Treatment Option 1 (STO1), a new potable water system and two new irrigation water systems would be provided. Under Supply and Treatment Option 2 (STO2) only one new potable water system would be provided. Potable water for both long term STOs would be provided to each community via one new water treatment facility located at Selma Estates. Irrigation water for STO1 would be provided via two new irrigation systems, one at each community. In order to develop the design concept for each STO, the ability of the four (4) existing Selma wells to meet the potable and irrigation water demands was considered.

Potable Water The potable water demands projected at build‐out of both communities for STO1 and STO2 are 196,400 gpd and 441,900 gpd, respectively. A comparison of well capacity to potable water needs is summarized in Table ES‐1.

Table ES.1: Comparison of Selma Estates Well Capacity to Selma Estates and Raspberry Falls Potable Water Needs

Combined Long Term Supply Potable Flow Selma Well Treatment Facility Capacity Surplus / and Treatment per connection Supply Available Water Demand Deficit (gpd) Option (gpd) (gpd) (gpd)1 1 400 196,400 280,000 83,600 2 900 441,900 280,000 (161,900) 1. Based on the number of planned connections in the Raspberry Falls (214) and Selma Estates (277) communities at build‐out and the potable water flow per connection.

For STO1, the existing Selma Estates community supply wells are adequate to supply the groundwater needed for the 400 gpd per connection potable water supply scenario.

For STO2, which uses the higher flow rate of 900 gpd per connection to meet all water needs, there is a well capacity deficit of over 160,000 gpd. Multiple options were evaluated to address the supply deficit. The best option is to utilize three (3) of the existing Raspberry Falls community supply wells to augment the Selma Estates wells. These wells are established and have strong yields.

Irrigation Demand Under STO1, raw water is used for irrigation. The raw water demand for the Raspberry Falls irrigation system is approximately 101,500 gpd. This flow rate can be met by using the existing Raspberry Falls community supply wells. The raw water demand for the Selma Estates irrigation system is approximately 138,500 gpd. This demand cannot be met using the existing Selma Estates or Raspberry Falls supply wells as the Selma Estates wells would be used for the combined potable system and the Raspberry Falls wells

would be used for Raspberry Falls’ irrigation needs. Therefore, new Selma Estates supply wells are required. Assuming the new irrigation wells would be operated for 12 to 18 hours per day, a well (or wells) with a well yield of at least 200 gpm would be required to satisfye th irrigation demand. Based on the findings from previous and current groundwater supply evaluations performed by Emery & Garrett Groundwater, Inc., sufficient new wells can be developed within the Selma Estates community to provide the necessary capacity.

STO2 does not include a separate raw water system for irrigation as all water needs will be met by the combined treatment facility.

Membrane Filtration In order to meet the potable water demands of both communities, the majority of the existing wells must be used. These wells may present a mix of groundwater and GUDI sources depending on future well classifications. GUDI sources that are used in potable water applications must meet treatment standards that are more stringent than groundwater sources. The treatment of groundwater is typically limited to virus inactivation through disinfection; the Code of Virginia requires that any waterworks supplied by a GUDI source must use filtration to reliably achieve 3‐log removal and/or inactivation of Giardia lamblia cysts, 4‐log removal and/or inactivation of viruses, and 2‐log removal of Cryptosporidium. As noted in the October 2014 memo, Raspberry Falls and Selma Estates: Preliminary Assessment of Long‐Term Supply Options, membrane filtration was determined to be the most viable treatment method for treating GUDI source water in Raspberry Falls and Selma Estates. The success of membrane filtration in the treatment of GUDI sources has been proven throughout the Shenandoah Valley in Virginia, as well as throughout the County, for similar user demands. Regardless of current or future Raspberry Falls/Selma Estates well classifications (i.e., groundwater or GUDI), all well water withdrawn for potable use will undergo membrane treatment.

The membrane treatment facility will be comprised of several components, such as pumps, strainers and storage tanks, in addition to the membrane filter units. As the size of each process component depends in part on the total amount of water to be treated, the size of the expanded Selma Estates treatment facility will depend on the STO selected for implementation. However, regardless of the size of combined treatment facility, the overall water treatment sequence will be the same for each option.

Triple Bottom Line Analysis A triple bottom line (TBL) assessment of each option was performed to consider the advantages and disadvantages of each option with respect to economic, social, and environmental impacts. Of the three TBL components the economic element is expected to have the greatest impact on the community given the capital cost of each project compared to the size of the benefiting community. Adverse environmental impacts are expected to be minor due to the limited geographical scope and modest construction activity of the proposed projects. Finally, adverse social impacts are expected to be very minor. Accordingly, the economic criterion was given a weight of 40 percent, each environmental criterion was given a weight of 20 percent, and each social criterion was given a weight of 10 percent. After each criterion was weighted, a simplified scoring approach, with a maximum score of 10, was used to compare the two options.

A summary of the scoring results is provided in Table ES‐2. STO2 scores higher in regards to cost, public health, and quality of life and STO1 scores higher in regards to greenhouse gas emissions and aquifer sustainability. The total score of STO1 is 4 points and the total score of STO2 is 6 points. Based on their

respective scores, STO2 (i.e., combined water treatment for all uses) is recommended over STO1 (i.e., combined water treatment with separate irrigation).

Table ES.2: Summary of Criteria Scoring for the Two Water Supply and Treatment Options

Criterion Scores STO1 ‐ Combined Criterion Type Criterion STO2 ‐ Combined Treatment with Treatment for All Uses Separate Irrigation Economic Lowest Capital Cost 0 4 Lower Greenhouse Gas Environmental Emissions 2 0 Greater Aquifer Environmental Sustainability 2 0 Better Protection of Public Social Health 0 1 Social Better Quality of Life 0 1

Total Score (out of a possible 10 points) 4 6

In regards to the economic criterion, STO2 ranks higher than STO1 as the capital cost of STO2 is expected to be lower than that of STO1.

In regards to the environmental criteria, STO1 ranks higher than STO2 in both categories. Under the greenhouse gas emission criteria, STO1 is expected to generate a lower emissions than STO2. Therefore, STO1 is the preferred option. Under the aquifer sustainability criteria, daily water withdrawals for irrigation under STO1 could be capped without affecting the availability of treated water for all other uses. Therefore, STO1 offers better protection of the aquifer and is the preferred option with respect to the environmental criteria.

In regards to the social criteria, STO2 ranks higher than STO1 in both categories. Under the protection of public health criterion, a risk of exposure to bacteria from contact with untreated irrigation water exists for STO1 that does not exist for STO2. Therefore, STO2 is the preferred option. Under the quality of life criterion, STO2 offers flexibility in how each household can utilize its daily water allotment as well as minimizing homeowner inconveniences during the project installation period.

Treatment Option Recommendation Of the two long term supply and treatment options considered for implementation at Selma Estates and Raspberry Falls, Hazen and Sawyer recommends that Loudoun Water consider proceeding with STO2 for the reasons explained below.

First, with regards to economics, the capital cost of STO1 is expected to be significantly higher (i.e., more than 70% higher) than that of STO2. Second, with regards to social impacts, the implementation of STO2 would result in lower disruptions to everyday life and offer better protection of the public health over the long term. Third, although STO1 ranks higher in both environmental categories, the differences in environmental impacts are small. For example, the difference in carbon emissions is only about 10%.

Raspberry Falls and Selma Estates Study of Long Term Options January 6, 2015

1.0 Background

1.1 Study Area The neighboring communities of Raspberry Falls and Selma Estates are located in Loudoun County, VA to the north of Leesburg, see Figure 1.1. Each community has its own series of groundwater supply wells and onsite water treatment facility. Both facilities achieve virus inactivation through chlorination. Though originally built by developers, both systems are currently owned and operated by Loudoun Water. Both treatment systems are sized to serve the total number of planned residential units for each community at build‐out: Raspberry Falls is 214 equivalent residential connections (ERCs) and Selma Estates is 277 ERCs.

1.2 Water Sources and Previous Studies

1.2.1 Water Supply Sources

Raspberry Falls The existing Raspberry Falls Community System (RFCS) has four (4) offsite groundwater wells – Wells PW‐1, PW‐2, PW‐3, and RSP‐F. Originally, only two wells, PW‐1 and PW‐2, were available to supply water to the RFCS. PW‐3 was never piped to the RFCS because of interference between it and PW‐2; (they are hydraulically linked). The fourth well, RSP‐F, was developed after PW‐1 was classified as groundwater under the direct influence of surface water (GUDI) by the Virginia Department of Health (VDH) in November 2010 and taken out of service by Loudoun Water. Currently only PW‐2 and RSP‐F are actively supplying water to the RFCS.

Table 1.1 provides a summary of the aquifer characteristics and well construction records for the Raspberry Falls wells.

Table 1.1: Raspberry Falls Community System: Aquifer Characteristics and Well Construction Records

Well Parameter PW‐1 PW‐2 PW‐31 RSP‐F Drilled 7/26/1991 5/8/1991 5/13/1991 2/17‐2/19/2008 12” to 110’ 12" to 120', 8" to 12" to 104', 8" to 12" to 104', 8" Hole Size 8” – 110’ to 240’ 350' 405' to 540' 6” – 240’ to 400’ Depth to Bedrock 72' 70' 60 60’ 250' to 255' 145' to 150' and 178‐180’ Water Bearing Zone 125' to 130' and several several other zones other zones Steel Casing 8" to 120' 8" to 104' 8" to 104' 8” to 110’ Pressure grouted to Pressure grouted Pressure Pressure Grouted to Grouting 74' to 100' grouted to 91' 110’ 2/6‐8/97 (48 10/31‐11/12/2010 Safe Yield Date 2/6‐8/97 (48 hours) TBD hours) (281 hours) 44' below ground 56' below ground 60' below 55’ below ground Static Water Level level level ground level level Safe Yield 200 gpm 200 gpm 100 gpm 100 gpm Drawdown 4' 31' TBD 45.8’ No pump 90 gpm @ 75' TDH, 84 gpm @ 88' TDH, 100gpm @ 162' TDH, Pump currently 3 HP at 84' depth 3 HP at 126' depth 7.5 HP at 155’ depth installed 3" galvanized Riser Pipe 3" galvanized steel 3" galvanized steel 3" galvanized steel steel Source Capacity1 160,000 gpd 160,000 gpd TBD 80,000 gpd 1. Well PW‐3 is currently capped. This well will need to be retested and its capacity and safe yield determined.

Well PW‐1 has been determined to be under the direct influence of surface water (GUDI) by VDH and requires treatment via filtration prior to use for potable water. As noted above, Wells PW‐2 and PW‐3 are located in close proximity to each other. A hydraulic influence on Well PW‐2 was previously observed during operation of Well PW‐3. Thus, the use of Well PW‐3 was discontinued. Since the influence on Well PW‐2 is minor, Well PW‐3 could be used for irrigation needs. The total well capacity at Raspberry Falls, excluding PW‐3, is 400,000 gpd. A well study will have to be performed on PW‐3 to determine the well yield capacity.

Water quality data for the Raspberry Falls wells is presented in Table 1.2. The values in Table 1.2 are average values from historical sampling events.

TRONGATE CT

BERKHAMSTEAD PL JAMES MONROE HWY - RTE 15

SELMA LIMESTONE SCHOOL RD FROSTLEAF LA SELMA GARRILAND DR ESTATES

ROCKY MEADOW LA

HUNTER PL

RASPBERRY DR

SELMA LA RASPBERRY FALLS FARM LA

BRIARBERRY PL

SWIFTWATER DR RASPBERRY PLAIN LA

ELK RUN CT

LOCUST HILL LA WHITES FERRY RD

JAMES MONROE HWY ¯ SMARTS MILL LA 0 0.25 0.5 Miles TUTT LA

Selma Estates and Raspberry Falls LTOA

BIG SPRINGS CT

TWIN MAPLE LA Figure 1-1: Selma Estates and Raspberry Falls Study Area

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Table 1.2: Summary of Raw Water Quality Parameters for Raspberry Falls

Iron Alkalinity Hardness Regulated Regulated Temp. Conductivity Turbidit Manganese Well pH (mg/ 5 (mg/L as (mg/L as VOCs SOCs (°F) (mohm/cm) y (NTU) 5 (mg/L) 5 5 L) CaCO3) CaCO3) (mg/L) (mg/L) Below Detection PW‐11 57 7.4 206 0.1 0.11 < .002 92 150 BDL Limit (BDL) PW‐21 57 7.5 192 0.1 ‐‐‐ ‐‐‐ ‐‐‐ ‐‐‐ BDL Detected2 RSP‐F3 59 8.3 244 3.07 0.17 BDL 111 116 BDL BDL 6.5 EPA ‐‐‐ – ‐‐‐ 0.3 0.05 ‐‐‐ ‐‐‐ BDL BDL SMCL 4 8.5 1. Average values over 4 year period, 2007‐2010‐ for Well PW‐1; PW‐2 data is average of data from April 2008 – December 2010. 2. Two SOC and VOC scans were conducted in 2008 and one in Feb 2011. Herbicide “metolachlor”, an unregulated synthetic organic carbon, was detected at very low levels of 0.07 µg/L, 0.09 µg/L, and 0.055 µg/L in May and July of 2008 and February 2011, respectively, at Well PW‐2. 3. Average values of June 2009 and October 2010 (with exception of VOC’s and SOC’s collected in 2008 and in 2011) 4. Secondary Maximum Contaminant Levels (SMCLs) are non‐enforceable water quality standards, established for aesthetic considerations. 5. Finished water data from average of entry point sample collected 9/28/05 and 8/27/2008.

The locations of the Raspberry Falls wells are shown in Figure 1.2.

Selma Estates Four (4) groundwater wells located throughout the community are available to supply water to the Selma Estates Community System (SECS): Wells 1B, 9F, 7E2 and 12E. However, Loudoun Water detected the presence of E. coli in Well 7E2 in October of 2013; additional detections of E. coli occurred in spring and early summer of 2014 in wells 7E2 and 9F. In response, Loudoun Water worked with Hazen and Sawyer to design, permit and install a temporary membrane filtration skid system for enhanced water treatment. The intent was to proactively provide a water treatment technology capable of meeting GUIDI treatment requirements in order to treat water from the Selma Estates wells actively undergoing GUDI evaluations. The intent was also to supplement the potable water supply at Raspberry Falls (when demand necessitated it), while Raspberry Falls well PW‐2 was offline during its GUDI evaluation2.

As of December 2014, Raspberry Falls PW‐1 is the only well determined to be GUDI at Selma Estates and Raspberry Falls. Selma Estates Wells 7E2 and Well 9F are currently undergoing GUDI evaluations.

Table 1.3 provides a summary of the aquifer characteristics and well construction records.

2 It should be noted that the VDH evaluation of Well PW‐2 was completed in 2014. And that Well PW‐2 was found to be GUDI free. 7

Table 1.3: Aquifer Characteristics and Well Construction Records for Selma Estates

Well Parameter 1B 9F 7E2 12E Drilled October 2001 December 2003 October 2001 May 2006 8" to 480', 6" to 8" to 200’, 6" to 12" to 108, 8" to Hole Size 8" to 505' 640' 380’ 715’ Depth to Bedrock 12' 17' 70’ 28’ 385’, 448’, and 90’, 135’, and Water Bearing Zones 340' to 433' 112’ to 140’ several other zones several other zones Steel Casing 8" to 109’ 8" to 108' 8” to 110’ 8” to 108’ Pressure grouted to Pressure grouted to Pressure grouted to Pressure grouted to Grouting 100' 100' 100' 100' 4/19‐23/04 (100 4/19‐25/04 (144 4/19‐23/04 (96 6/26‐29/06 (72 Safe Yield Date hours) hours) hours) hours) 17.5' below ground 50.75' below 35.4’ below ground Static Water Level grade level ground level level Safe Yield 65 gpm 75 gpm 100 gpm 110 gpm Drawdown 198.5' 358.6' 5.88’ 259.5’ 65 gpm @ 420' 75 gpm @ 520' 150 gpm @ 300’ 110 gpm @ 560’ Pump TDH, 10 HP at 300' TDH, 15 HP at 350' TDH, 15 HP at 100’ TDH, 20 HP at 380’ depth depth depth depth Source Capacity1 52,000 gpd 60,000 gpd 80,000 gpd 88,000 gpd

The total well capacity at Selma Estates is 280,000 gpd. Water quality data for the Selma Estates wells is presented in Table 1.4. Values presented in the table are average values from historical sampling events from 2004 ‐ 2010.

Selma Estates WTP 7E2 (! )" (! 12E

(! 9F

1B (!

RSP-F Raspberry (! Falls WTP )" (! PW-2 & PW-3 (! PW-1 ¯ 0 0.25 0.5 Miles

Selma Estates and Raspberry Falls LTOA )" Water Treatment Plant (! Water Supply Well Well Supply Pipe Figure 1-2: Existing Water Supply System Distribution Pipe

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Table 1.4: Summary of Raw Water Quality Parameters for Selma Estates

Alkalinity Hardness Regulated Regulated Temp Conductivity Turbidity Iron Manganese Well pH (mg/L as (mg/L as VOCs SOCs (°F) (mohm/cm) (NTU) (mg/L) (mg/L) CaCO3) CaCO3) (mg/L) (mg/L) 1B 57 7.2 233 7.4 1.1 0.06 108 99 Detected BDL

9F 58 7.7 299 0.1 0.005 BDL 135 146 ‐‐‐‐‐ ‐‐‐‐‐‐ 7E2 56 7.6 220 0.15 0.11 BDL 93 105 ‐‐‐‐‐ ‐‐‐‐‐‐ 12E N/A 8.0 278 1.3 0.3 0.05 122 139 ‐‐‐‐‐ ‐‐‐‐‐‐ 6.5 EPA ‐‐‐ – ‐‐‐ 0.3 0.05 ‐‐‐ ‐‐‐ ‐‐‐‐‐‐ ‐‐‐‐‐‐ SMCL 2 8.5 1. Nine VOC and SOC scans on finished water were conducted between the years 2008 and 2010. Four regulated VOCs were detected at very low levels in a portion of the scans. The compounds detected were ortho‐, meta‐, and paraxylenes, and ethyl benzene. The detected compounds were significantly below (2 to 4 orders of magnitude below) the EPA established Maximum Contaminant Levels. 2. Secondary Maximum Contaminant Levels (SMCLs) nare no ‐enforceable water quality standards, established for aesthetic considerations.

The locations of the Selma Estates wells are shown in Figure 1.2.

1.2.2 Previous Studies

Previous groundwater supply and treatment studies performed for the Raspberry Falls and Selma Estates community systems that were reviewed in support of this project are summarized below:

Supply Studies  Groundwater Supply Development Program, Final Hydrogeologic Report, Extended Pumping Tests on Community Supply Wells SEL‐1B, SLX‐9F and SLX‐7E2, by Emery & Garrett Groundwater, Inc., May 2004. o This report outlined the results of extended pumping tests for a number of test wells that were converted into production wells by Emery & Garrett Groundwater, Inc. (EGGI) in support of the phased Selma Estates groundwater supply program. The study indicated that there were a number of high yielding wells in the karst terrain around Selma Estates; however, some of the larger yielding wells, notably 7C and 7C2, failed during development. The mapping contained within the report provided useful information about the location of the various test and production wells and their associated yields, and was used in the conceptualization of groundwater supply options for the long term scenarios described herein. As a result of this report, wells 1B, 9F and 7E2 were selected for use as community supply wells to serve Selma Estates.  Groundwater Supply Development Program, Final Hydrogeologic Report ‐ Addendum, Extended Pumping Tests on Community Supply Wells SEL‐1B, SLX‐9F and SLX‐7E2, by Emery & Garrett Groundwater, Inc., January 2005. o This addendum to the May 2004 report provided additional information 9

regarding the potential for sinkhole development around the Selma Estates wells, as well as the potential impact of pesticide and herbicide application in Raspberry Falls on the quality of the groundwater.  Groundwater Supply Development Program, Hydrogeologic Report, Pumping Test on Supplemental Community Supply Well SLX‐12E, by Emery & Garrett Groundwater, Inc., September 2006. o As recommended in this report, Well 12E was intended to serve as a supplemental well for the Selma Estates community water system.  Preliminary Hydrogeologic Investigation, Assessment of the Potential Availability of Groundwater Resources in the Western Portion of Raspberry Falls Golf &t Hun Club, by Emery & Garrett Groundwater, Inc., September 2008. o This study was undertaken in response to the detection of E. coli in the raw water from Raspberry Falls Wells PW‐1 and PW‐2. This study originally identified five (5) favorable locations for drilling of test wells; however, prior to actual test well drilling and production well development, the number of locations was reduced to four (4) and the locations were revised to include Well RSP‐F.  Yield and Quality Testing of Proposed (Replacement) Community Supply Wells RSP‐F and RASP‐3 for Raspberry Falls Golf & Hunt Club, by Emery & Garrett Groundwater, Inc., June 2009. o This report documented the testing performed on Well RSP‐F as well as the existing irrigation well RASP‐3. The testing showed that either well could be used to replace Well PW‐1 as a community supply well for Raspberry Falls. The report indicated additional wells, including RSP‐C, which could be developed for community water supply in the future if the need arose.

Treatment Studies  Raspberry Falls Water Supply and Treatment Evaluation, Membrane Treatment Facility Preliminary Engineering Report, Hazen and Sawyer, December 2008 o This study was undertaken at the same time as the EGGI alternative groundwater supply source study in response to the detection of E. coli in the groundwater from Wells PW‐1 and PW‐2. The treatment‐related aspects of the evaluation focused on membrane filtration and a Preliminary Engineering Report (PER) was prepared efor th recommended system. This PER was approved by VDH; however, the preferred option to address the potential GUDI determination at Raspberry Falls was to implement Well RSP‐F and avoid the use of any GUDI sources.

 Evaluation of Treatment Options for the Raspberry Falls and Selma Estates Community Systems, Hazen and Sawyer, August 2011.

 Evaluation of Town of Leesburg Water Service Alternatives for the Raspberry Falls Community System, Hazen and Sawyer, August 2011. o Concurrent with the development of Well RSP‐F, Loudoun Water undertook two parallel studies to investigate water supply and treatment options fore th Raspberry Falls and Selma Estates Community Water Systems. These studies

evaluated possible configurations and costs of filtration options to treat all wells to VDH Waterworks Regulations GUDI standards regardless of GUDI status, as well as the possibility and feasibility of connecting to the Town of Leesburg’s surface water system instead of using the existing groundwater wells. While the studies were primarily focused on addressing the GUDI condition at Raspberry Falls, the Selma Estates Community Water System was also considered because several of its wells were developed under the same geological conditions as Well PW‐1. It was thought that a combined treatment facility serving both communities could provide financial and operational benefits. As a result of these studies, it was recommended that the Raspberry Falls water facility be upgraded to include membrane treatment so Well PW‐1 could return to service. No activities were recommended at that time for the Selma Estates system, because there were no known water quality or water quantity issues at that time. Design of a membrane filtration system for Raspberry Falls was started and construction was dependent on a financing source.

 Raspberry Falls and Selma Estates: Preliminary Assessment of Long‐Term Supply Options, Hazen and Sawyer, October 2014. o This memorandum re‐evaluated the findings from the two 2011 studies noted above in the context of 2013 and 2014 E. coli sampling results for both the Raspberry Falls and Selma Estates community system wells. The preliminary assessment recommended a detailed evaluation of two long‐term supply options. The first option entailed construction of a single potable water treatment facility to serve both communities, and separate irrigation supply systems for each community. The second option entailed construction of a single potable water treatment facility to provide both communities with potable and outdoor (irrigation) use water.

1.3 General Regulatory Requirements

A review of the regulations pertaining to the use of groundwater under the direct influence of surface water (GUDI) in potable and non‐potable applications in Virginia was performed as part of the study of long‐term supply options. In instances where written regulations did not exist or could not be located, regulating agencies, such as VDH, were contacted for additional information. The results of the regulatory review are presented below.

1.3.1 Sampling and Treatment

Use of GUDI Wells for Potable Water Supply Regulations pertaining to the sampling and treatment of GUDI for potable use are clearly outlined in the Code of Virginia. Per section 12VAC5‐590‐420 of the Code, any waterworks supplied by GUDI must reliably achieve, through filtration, 3‐log removal and/or inactivation of Giardia lamblia cysts, 4‐log removal and /or inactivation of viruses, and 2‐log removal of Cryptosporidium. Furthermore, any potable use of GUDI water must have a residual disinfectant concentration and that residual cannot drop below 0.2 mg/L entering the distribution system for more than four hours. This residual disinfectant cannot be below detectable concentration in more than 5% of samples each month for two consecutive months.

Use of GUDI Wells for Non‐Potable Water Supply Currently, there are no regulations in the Code of Virginia pertaining to the sampling and treatment of GUDI for non‐potable water uses, such as irrigation. The VADEQ and the VDH also lack regulations pertaining to the use of GUDI for irrigation.

Loudoun County Health Department (LCHD) was also consulted to determine whether local County requirements existed for irrigation with GUDI, and it was determined that the County does not have any ordinance over irrigation. Therefore, testing of GUDI irrigation wells is not required by the County.

Overall, there are no State (VDH ODW, VADEQ OPWS) or County (LCHD) regulations applicable and enforceable pertaining to the use of GUDI wells for irrigation.

1.3.2 Annual Withdrawal Reporting

Regardless of well classification and water use, the volume of well water withdrawn in Virginia must be reported to the VADEQ on an annual basis in accordance with section 9VAC25‐200‐10 of the Code, i.e., the Annual Water Withdrawal Reporting regulation (AWWR). Per discussions with VADEQ, the AWWR requires the annual reporting of surface and groundwater well withdrawals for potable and non‐potable purposes. Withdrawal reports for the previous calendar year are due annually on January 31st and are used to plan for future water needs in Virginia. It is possible that VADEQ may regulate groundwater withdrawals in areas deemed to have supply issues and that these areas may be subsequently designated as Ground Water Management Areas.

Withdrawals for irrigation must be reported for users whose daily average withdrawal exceeds 10,000 gallons per day in a single month. Reporting information includes monthly and annual withdrawal amounts, owner, source, source type, subtype, and category of use. Further instructions on how to report raw water withdrawals for irrigation can be found on the VADEQ website at: http://www.deq.virginia.gov/Programs/Water/WaterSupplyWaterQuantity/WaterSupplyPlannin g/AnnualWaterWithdrawalReporting.aspx.

1.4 Purpose of the Study of Long‐Term Water Supply Options

In November of 2010, elevated levels of total coliform and E. coli bacteria were discovered in one of the raw water supply wells serving Raspberry Falls. As a result of a detailed evaluation, the Virginia Department of Health (VDH) reclassified the well as groundwater under the direct influence of surface water (GUDI). GUDI wells pull from sources that do not benefit from geological percolation. Treatment standards for GUDI sources require filtration; the Raspberry Falls Treatment Facility was not designed to provide GUDI treatment. Therefore, Loudoun Water discontinued the use of the GUDI well and installed a new Raspberry Falls well. Recent (2013 & 2014) raw water tests have triggered VDH GUDI evaluations for multiple wells across both communities. Though no additional wells have been determined to be GUDI, the observed increase in test results that trigger evaluations represents a demonstrated risk to the sustainability of the current water treatment practices for both communities.

The potential for additional VDH well re‐classifications has prompted Loudoun Water to re‐evaluate the future long term water treatment needs of the Selma Estates and Raspberry Falls communities. After performing a preliminary screening of potential supply and treatment options, Loudoun Water directed 12

Hazen and Sawyer to further analyze the two most promising options as outlined in the 2014 Hazen and Sawyer Memorandum Raspberry Falls and Selma Estates: Preliminary Assessment of Long‐Term Supply Options (see, section 1.2.2 for a summary). These options are:

 Supply and Treatment Option 1: Construct ae singl water treatment plant at Selma Estates to serve the potable water needs of both communities. The combined treatment facility will be sized to treat and supply 400 gpd per connection of potable water for domestic use. Construct two separate irrigation supply systems, one for each community, sized to supply 500d gp per connection of untreated groundwater for irrigation use only.

The purpose of this report is to provide a detailed evaluation, including a Triple Bottom Line assessment, of Supply and Treatment Options 1 and 2.

Raspberry Falls and Selma Estates Study of Long Term Options January 6, 2015

2.0 Water Demands and Supply

2.1 Water Connections, Flow Rates, and Total Demand

The community of Raspberry Falls will contain 214 equivalent residential connections (ERCs) for potable water use and 203 connections for residential irrigation use at build‐out. The Selma Estates community will contain 277 ERCs at build‐out, all residential. The difference in the number of connections between potable and irrigation use in Raspberry Falls is because there are several facilities within Raspberry Falls that require potable water supply but not irrigation water supply. These facilities include the Golf Club House and the community pool. These ERC counts are used in conjunction with “per connection” water usage to develop the build‐out water demands for the two communities.

As noted in Section 1.4, the following two long‐term supply and treatment options are being evaluated as part of the study:

 Supply and Treatment Option 1: Construct a single water treatment plant for both communities at Selma Estates, which will be sized to treat and supply 400 gpd per connection of potable water for domestic use. This option also includes the construction of separate non‐potable supply systems, one for each community, sized to supply 500 gpd per connection of untreated groundwater for irrigation only. The flow rate of 400 gpd per connection is equivalent to typical indoor water usage plus an allowance for normal outdoor usage, excluding permanent underground irrigation systems.  Supply and Treatment Option 2: Construct a single water treatment plant located at Selma Estates to serve all of the water needs of both communities. The plant would be sized based on the maximum usage observed over the past 6 years (900 gpd per connection). The maximum daily potable demand and the maximum daily irrigation demand for Option 1 are presented in Tables 2.1 and 2.2 respectively. The maximum daily mixed use demand for Option 2 is presented in Table 2.3

Table 2.1: Supply and Treatment Option 1 ‐ Potable Water Demands for Raspberry Falls and Selma Estates

Maximum Day Equivalent Gallons per Day per Demand Residential Community Connection Connections1 gpd

Raspberry Falls 214 400 85,600 Selma Estates 277 400 100,800

TOTAL 491 400 196,400 Notes: 1. Connections at build‐out of the respective community.

Table 2.2: Supply and Treatment Option 1 ‐ Irrigation Demands for Raspberry Falls and Selma Estates

Maximum Day Equivalent Gallons per Day per Flow Residential Community 1,2 Connection Connections gpd

Raspberry Falls 203 500 101,500 Selma Estates 277 500 138,500

TOTAL 480 500 240,000 Notes: 1. Connections at build‐out of the respective community. 2. The difference between potable water ERCs shown in table 2‐1 and irrigation ERCs shown here is due to Raspberry Falls facilities such as the Golf Course Club House and community pool, which require drinking water, but not irrigation.

Table 2.3: Supply and Treatment Option 2 ‐ Mixed Use Water Demands for Raspberry Falls and Selma Estates Maximum Day Equivalent Gallons per Day per Flow Community Residential 1 Connection Connections gpd

Raspberry Falls 214 900 192,600

Selma Estates 277 900 249,300

TOTAL 491 900 441,900 Notes: 1. Connections at build‐out of the respective community.

2.2 Comparison of Water Supply Needs and Availability

Two separate water treatment facilities currently exist to serve the Selma Estates and Raspberry Falls communities. The long‐term supply and treatment evaluation is considering options that will meet the potable water demands of both communities via one water treatment facility in order to simplify facility operation and maintenance. Once water is withdrawn from the aquifer, it will be treated at the combined facility and distributed to the residents of each community via the existing distribution system. To develop the design concept and associated cost of each option, the ability of the existing Selma Estates community supply wells to meet the build‐out potable water demand was considered. This evaluation is summarized in Table 2‐4.

Table 2.4: Comparison of Selma Estates Well Capacity to Potable Water Needs

Capacity Required Well Supply Available Capacity Surplus / Supply Scenario (gpd) (gpd) Deficit (gpd) Option 1: 400 gpd/ERC 196,400 280,000 83,600 Option 2: 900 gpd/ERC 441,900 280,000 (161,900)

Water for Combined Treatment, Supply and Treatment Option 1 As seen in Table 2.4, the existing Selma Estates community supply wells are more than adequate to supply the groundwater needed for Supply and Treatment Option 1 (i.e., the 400 gpd/ERC potable water supply scenario). The required capacity can be provided by any three of the existing Selma wells allowing the fourth well to serve as a backup. This meets LW’s desire to have a spare well so duty wells can be taken out of service for scheduled maintenance. No additional wells are required to supply source water for STO1.

Water for Combined Treatment, Supply and Treatment Option 2 A deficit of over 160,000 gpd of groundwater exists under Supply and Treatment Option 2, which uses a flow rate of 900 gpd/ERC to meet all community water demands. If the deficit were to be translated into a required well yield, based on VDH water supply well requirements, the well yield needed to meet demand would be 203 gpm. Per Loudoun Water requirements, and good engineering design practices, at least two additional groundwater supply wells need to be provided so that there is always a spare, offline well. This equates to a 160,000 gpd yield capacity.

Multiple options were evaluated to address the STO2 groundwater supply deficit. The best supply option is to utilize the existing Raspberry Falls community wells to augment the Selma wells. Both Wells PW‐1 and PW‐2 have a reported yield of 200 gpm, which means that either of the wells could be used to offset the supply capacity deficit that exists with Option 2. As shown in Table 1‐1, the installed well pumps in Wells PW‐1 and PW‐2 have capacities of 90 and 84 gpm, respectively. These well pumps would need to be replaced with new pumps that take full advantage of the available well yield. Based on discussions with EGGI, additional tests are warranted to confirm that the 200 gpm well yield can still be achieved.

The well supply concept evaluated utilizes wells PW‐1, PW‐2 and RSP‐F in conjunction with the existing potable water storage and booster pump infrastructure to convey the raw groundwater from Raspberry Falls to the Selma Estates treatment facility. All three of the wells would be operated as they are today. Meaning that they will pump groundwater from the aquifer to the existing water storage tank. The existing chemical feed practices at Raspberry Falls would be discontinued. The existing booster pumps would pump the raw groundwater from the existing water storage tank up to the expanded Selma Estates treatment facility via a new raw water transmission pipeline. This raw water transmission pipeline is proposed to be routed behind the Raspberry Falls development to avoid impacts to the existing household frontages and streets. This overall concept is depicted in Figure 2.1.

Water for Irrigation, Supply and Treatment Option 1 As the four (4) existing Selma Estates wells are being used to supply water to the combined treatment facility under STO1, irrigation water for Selma Estates and Raspberry Falls will need to be supplied by other sources such as the existing Raspberry Falls wells or other, newly constructed wells.

Raspberry Falls As indicated in Table 2.2, the groundwater supply required for the Raspberry Falls non‐potable system is approximately 101,500 gpd. This need can readily be met using the existing Raspberry Falls community supply wells.

Selma Estates Table 2.2 highlights that 138,500 gpd is needed for supplying the Selma Estates irrigation system. Assuming the irrigation supply wells would be operated between 12 and 18 hours per day, a well (or )wells

with a well yield of at least 200 gpm would be required to satisfy the Selma Estates irrigation need. Based on the findings from previous and current groundwater supply evaluations performed by EGGI, sufficient new wells can be developed within the Selma Estates community to provide the necessary capacity. This concept is depicted in Figure 2.2. It should be noted that, unlike the potable water supply wells, redundant wells are not required.

Selma Estates WTP 7E2 (! )" (! 12E

(! 9F

1B (!

RSP-F (! Raspberry Falls Storage Tank )" (! PW-2 & PW-3 (! PW-1 ¯ 0 0.25 0.5 Miles

Selma Estates and Raspberry Falls LTOA )" Water Treatment Plant (! Water Supply Well Well Supply Pipe Figure 2.1: Well Supply for STO2 Distribution Pipe New Supply Line to Selma Estates

This page intentionally left blank. Selma Estates WTP 7E2 (! )" (! 12E

(! 9F

1B (!

Two Wells on Selma Site for Irrigation Pump House Storage Tank

RSP-F (!

(! PW-2 & PW-3 (! PW-1 ¯ 0 0.25 0.5 Miles

Selma Estates and Raspberry Falls LTOA )" Water Treatment Plant (! Water Supply Well Well Supply Pipe Figure 2.2: Well Supply for STO1 Distribution Pipe

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3.0 Water Treatment, Storage and Distribution

3.1 Membrane Filtration

Due to the limestone geology, there is always a potential that any of the current wells can be classified as GUDI in the future. Under the Code of Virginia, GUDI sources must meet the same treatment standards as surface water sources. This includes 3‐log removal and/or inactivation of Giardia lamblia cysts, 4‐log removal and /or inactivation of viruses, and 2‐log removal of Cryptosporidium. The majority of Giardia and Cryptosporidium removal must be accomplished via filtration.

There are many types of filtration technologies available. These include gravity media filtration, pressure filtration, and membrane filtration. Several of these technologies were examined in depth via previous treatment studies conducted on behalf of Loudoun Water. Membrane filtration was selected as the GUDI treatment method of choice for a number of reasons. First, membrane filtration accomplishes the required filtration treatment by providing an absolute barrier to particle passage, including bacteria and pathogenic organisms such as Cryptosporidium. Second, the compact footprint of the membrane filtration units and lower chemical requirements (as compared to conventional treatment processes) help to reduce the size of the treatment facility needed. This will in turn reduce the overall cost to construct the project compared to other filtration technologies. Finally, membrane filtration is a proven technology for treating GUDI source waters in Virginia, having been installed in 32 of the 35 systems with GUDI source waters under the purview of VDH’s Abingdon and Lexington ODW Field Offices.

3.1.1 Membrane Filtration Overview

In a pressurized membrane system, raw water is fed under pressure into a series of membrane modules, each of which contains thousands of hollow fiber membranes. The water in each module passes through the membrane fibers pores into the interior membrane chamber. All particles larger than 0.1 micron in diameter are left on the outside of the membrane fibers in the reject water. Thus, the membrane fibers essentially “strain” the particles out of the water, and provide an absolute barrier to particle passage, including bacteria and pathogenic organisms such as Cryptosporidium and Giardia.

3.1.2 Raspberry Falls / Selma Estates Combined Membrane Facility Concepts

The membrane treatment facility will be comprised of several components, such as pumps, strainers and storage tanks, in addition to the membrane filter units. The size of each process component will depend in part on the total amount of water to be treated and stored. However, regardless of the size of combined treatment facility to be constructed at Selma, the overall water treatment sequence will be the same for both options. A general schematic of the overall membrane treatment process and its main components is presented in Figure 3.1.

First, water is obtained from the aquifer via a series of groundwater wells and pumps (as discussed in Section 2). From there it is sent to a break tank which serves as the water supply reservoir for the water treatment process. The break tank also provides a hydraulic break between the well supply system and water treatment system. Next, the membrane feed pumps pull water from the break tank and through a pre‐treatment strainer. The strainer serves to remove relatively large particles from the treatment process thereby protecting and prolonging the service life of the 19

membranes. The membrane feed pumps then send the strained flow into the actual membrane filtration units for treatment. Filtered water (called the filtrate) is then disinfected and treated with fluoride and a corrosion inhibitor. From there treated water enters into a storage tank where it is held until it is needed. Finally, treated water is removed from the storage tank and pumped in the distribution system for domestic use. If GAC contactors are required in the future they would be inserted into the process train downstream of the membrane filtration units and upstream of disinfection.

Membrane Treatment System Capacity Three important factors in membrane sizing are water demand, membrane flux rate (i.e., the rate at which water permeates the membrane) and membrane recovery rate (i.e., the amount of water that can be produced for consumption per gallon of water fed to the membrane3).

The total water demand for Supply and Treatment Options 1 and 2 are set by the maximum number of system connections and the desired flowrate per connection. In this case, 196,400 gpd for STO1 and 441,900 gpd for supply and treatment option 2. Membrane flux and recovery rates vary by membrane manufacturer and may also differ depending on the process safety factor desired. Therefore, a conservative membrane flux rate of 25.6 gallons/square foot/day (gfd) and a recovery rate of 90% were selected for the purpose of preliminary sizing. The membrane sizing parameters are summarized in the table 3.1.

Table 3.1: Membrane Sizing Parameters

Total Flow per Total # of Flow Average Option Connection Flow connections Adjusted1 (gal/sf/day) (gal/day) (gal/day) (gal/day)

1 400 491 196,400 218,222 25.60

2 900 491 441,900 491,000 25.60

Notes: 1. Assumes a 90% recovery rate.

Based on the values chosen, the combined membrane treatment system is sized to process 218,000 gpd for Supply and Treatment Option 1 and 491,000 gpd for Supply and Treatment Option 2.

3 Some of the water produced by the membrane is then used to clean the membrane. Therefore, not all of the filtrate is distributed for consumption. 20

Break Tank The design concept for the combined treatment facility involves the provision of a hydraulic break between the well supply system and the membrane treatment system. A hydraulic break between the two systems allows for operational flexibility and fosters system stability (as in the case of well supply disruptions for example). The hydraulic break at Selma will be created through the use of a break tank. This tank is basically an intermediate water storage vessel located between the water supply source and the water treatment process. In some instances break tanks can also be used to provide pre‐treatment such as allowing ferrous precipitants to settle prior to entering the membrane filtration system.

The size of the combined treatment facility break tank will vary depending on the supply and treatment option. However, each break tank is sized to limit the time between well pump starts (i.e., well pump cycle time). For purposes of analysis the minimum pump cycle time was assumed to be 15 minutes and all contributing supply wells were assumed to operate (i.e., to turn on/off) in unison. It was also assumed that well pumps would operate for 720 minutes a day to allow for aquifer recovery and that the break tank would operate at levels between 50% and 100% full. Based on these assumptions, break tanks of 2,100 gallons and 4,600 gallons are required for Supply and Treatment Option Nos. 1 and 2, respectively. These assumptions can be adjusted during the preliminary engineering design process if different operational sequencing of the supply wells is desired.

3.1.3 Membrane Cleaning

In order for the membrane filters to function properly, they must be periodically cleaned. Light membrane cleaning is accomplished daily by reversing the flow through the membrane filter (i.e., backwashing the filter), whereas heavy membrane cleaning occurs periodically after the membranes have become heavily soiled or at predetermined intervals. There are three types of membrane cleaning processes. They are membrane backwash (BW), maintenance clean (MC), and clean‐in‐place (CIP). These processes are described in detail in the sections below and depicted graphically in Figure 3.1

Backwash (BW) The membrane BW process is designed to remove particles that have accumulated on the membrane surface. Backwashes are typically initiated automatically, at set intervals, or when the transmembrane pressure (TMP) rises to a preset level. The first step in the BW process involves scrubbing the membrane with air. Low pressure air is injected into the feed side of the membrane module for approximately one minute. At the same time, membrane filtrate (which has been collected in the BW/CIP tank) is pumped in the reverse direction through the module and then over to the process drain. Air and reverse flows are then stopped. At this point, most of the accumulated membrane debris has been removed. To complete the BW cycle, a forward flush is implemented. During this flush feed water is circulated from the feed tank to the feed side of the membrane at high velocity. This part of the BW process serves to further dislodge and remove any remaining membrane debris. Flush water from this part of the process is eventually discharged to the process drain.

Typically, membrane BW is fully automated and a backwash cycle is initiated automatically every 20 minutes for a duration of three minutes. During the BW, membrane filtration is suspended. Ideally, the backwash process restores the transmembrane pressure (TMP) to its baseline level. 21

However, most membranes exhibit a gradual increase in the TMP over the course of several backwash cycles. This gradual increase indicates the accumulation of foulants that cannot be removed via the backwash process alone. Chemical cleaning is eventually required to remove the accumulated foulants (MC or CIP).

Maintenance CleanC) (M Membrane maintenance cleaning (MC) chemically removes foulants created by inorganic scaling and other organic processes. As with backwashing, the membrane system is off‐line during chemical cleaning. The objective of chemical maintenance cleaning is to restore the TMP of the system to its baseline level.

There are a variety of different chemicals that may be used for membrane cleaning, and each is generally targeted to remove a specific constituent. For example, citric acid is commonly used to dissolve inorganic scaling. Strong bases, such as caustic, are typically employed to dissolve organic material. Detergents and surfactants may also be used to remove organic and particulate foulants, particularly those that are difficult to dissolve. Chemical cleaning may also utilize concentrated disinfectants, such as a strong chlorine solutions, to control biofouling. As a variety of foulants may be present on the membrane surface, it is often necessary to use a combination of different chemicals in series to remove them. The various types of chemical cleaning agents used are summarized in Table 3.2.

Table 3.2: Typical Membrane Cleaning Chemicals

Typical Target Chemical Category Commonly Used Chemicals Contaminant(s)

Citric Acid (C6H8O7) Acid Inorganic scale Hydrochloric Acid (HCl) Base Organics Caustic (NaOH) Sodium Hypochlorite (NaOCl)

Oxidants/Disinfectants Organics; Biofilms Chlorine Gas (Cl2)

Hydrogen Peroxide (H2O2) Surfactants Organics; Inert particles Various

The chemical cleaning regimen may be specified by the manufacturer or identified based on site‐ specific testing and analysis of the source water to identify likely foulants.

Clean‐in‐Place (CIP) The membrane CIP process is similar to that of the MC process, except that it occurs less frequently and is a more intensive than maintenance cleaning. The CIP process generally involves recirculating a cleaning solution through the membrane system at a high velocities and at an elevated temperature. A soak cycle follows the recirculation phase. After the soak cycle is completed, the membrane system is flushed to remove residual traces of the cleaning solution(s). The process may be repeated using different cleaning solutions to target different types of foulants until the membranes have been successfully cleaned.

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While backwashing is usually conducted at regular intervals, chemical cleaning is typically conducted only when necessary. A chemical clean is generally necessary for MF systems when the ability of periodic backwashing to restore system productivity (i.e., high membrane flux and low TMP) reaches a point of diminishing returns. Delaying necessary chemical cleaning can accelerate irreversible membrane fouling, reduce membrane production capacity, and shorten membrane life. A benchmark of 30 days has been suggested by the EPA as the minimum required interval between chemical cleanings for MF systems. However, it is not uncommon for a system to operate for much longer between cleanings, particularly in cases where the source water has a low foulant potential as is the case at Selma Estates.

Isolating the cleaning chemicals from the treated water is an important consideration for membrane filtration systems. In addition, it is important to properly flush the membrane unit after the cleaning process and before restarting the filtration cycle. The flushed water should be diverted to waste until filtrate water quality parameters return to normal production mode levels.

Due to the low frequency of CIP operation, the cleaning system controls are semi‐automated requiring some operator intervention for start‐up. The CIP process is initiated every 30 days (or as determined by the facility operating conditions) for approximately five hours. During this time period, membrane filters do not generate forward filtrate flow.

3.1.4 Waste Flows

As with most water treatment processes, the membrane filtration treatment process will generate waste products. In this case, waste flows are generated by the membrane cleaning processes described in Section 3.1.3. Waste flow rates can vary but are typically between 2% and 15% of the of the treatment system’s design flow. Therefore, addressing waste flow disposal is a key aspect in the design of a membrane filtration plant. The waste flows associated with the two treatment options will be sent to the Rasberry Falls Wastewater Treatment Plant via the existing sewer system. It should be noted that surface discharge and ground injection waste disposal options were investigated and eliminated via a previous Loudoun Water Study. Waste Flows for each STO are described in the sections below.

Supply and Treatment Option No. 1 Waste Flows The waste flows for Supply and Treatment Option No. 1 will be generated via the CIP, MC and BW cleaning activities. For the purpose of waste analysis, CIPs were assumed to occur once per month, MCs were assumed to occur twice per month, and regular BWs were assumed to occur three times per hour. Table 3.3 presents the total anticipated volume of all waste streams associated with the membrane system.

Table 3.3: Treatment Option 1 Waste Flow Volumes and Rates

Condition/Parameter Volume (gal) BW Volume, Monthly1 180,000 MC Volume, Monthly2 2,500 CIP Volume, Monthly3 7,500 Total Waste Volume, Monthly 190,000 Total Waste Volume, Annual 2,280,000 Flow Stream Flowrate (gpm) Average Waste Flow Rate during CIP4 35 Max Instantaneous Flow Rate during BW5 250 1. Assumes BW cleans every 20 min (188 gallons per clean per skid) 2. Assumes 2 MC cleans per month (650 gallons per clean per skid) 3. Assumes 1 CIP clean per month (3,800 gallons per clean per skid). 4. CIP duration is assumed to be 5 hours. One skid is in CIP while the other maintains regular BW cycle 5. Based on peak flow rate through the unit during the forward flush stage of the backwash process.

As presented in Table 3.3, backwashing could potentially generate up to 180,000 gallons per month; however, this estimate is conservative for normal operating conditions. The actual operating membrane flux will be significantly less than the maximum design flux of 25.6 gfd. Therefore, membrane backwashes will likely be spaced out much wider than every 20 minutes, which will result in lower waste volumes.

Currently, waste flows from the existing Selma Estates treatment facility are conveyed to the Selma Estates community sanitary sewer collection system via a 4‐inch diameter sewer line. The sewer flows in the Selma Estates community are collected and conveyed by gravity to the Selma Sanitary Sewer Pump Station, which lifts the sewer flow from the Selma Estates collection system into the Raspberry Falls collection system. From the point of entry into the Raspberry Falls system, the Selma Estates sanitary wastes are conveyed by gravity to the Raspberry Falls Wastewater Treatment Plant (WWTP) for ultimate processing and disposal.

The limiting sewer system segment in the existing gravity sewer system extending from the existing Selma Estates treatment facility to the Selma Sewer Pump Station has a maximum capacity of 325 gpm. Instantaneous waste peak flows would consume approximately 75% of the available sewer capacity in these limiting sections. As the existing sanitary flows from the homes in Selma Estates must also be conveyed through the sanitary sewer collection system, it is recommended that a waste equalization tank be installed to limit the discharge flow rate to the sanitary sewer.

The equalization capacity required to minimize the treatment waste discharge rate to the sanitary sewer was evaluated based on various combinations of sanitary sewer flows and tank volumes.

The optimum equalization tank capacity for Supply and Treatment Option No. 1 is approximately 10,000 gallons. This capacity will provide sufficient volume to attenuate the membrane treatment waste streams such that the maximum discharge rate to the sanitary sewer will be 50gpm. As this rate is only 15 percent of the capacity in the most limiting sewer system segment, sufficient capacity is maintained in the sewer line for other, existing Selma Estates sanitary sewer flows.

In addition to waste volume equalization, the proposed tank will also provide a convenient location for neutralization of cleaning process wastes. This is explained ein mor detail in Section 3.1.5.

Supply and Treatment Option No.2 Waste Flows The waste flows for Supply and Treatment Option No. 2 will also be generated by CIP, MC and BW cleaning activities. The same frequencies for the three types of cleaning procedures were used here as were used for Supply and Treatment Option No. 1. Table 3.4 presents the total anticipated volume of all waste streams associated with the membrane system.

Table 3.4: Treatment Option 2 Waste Flow Volumes and Rates

Condition/Parameter Value BW Volume, Monthly (gals)1 360,000 MC Volume, Monthly (gals)2 5,000 CIP Volume, Monthly (gals)3 15,000 Total Waste Volume, Monthly (gals) 380,000 Total Waste Volume, Annual (gals) 4,560,000 Flow Stream Flowrate (gpm) Average Waste Flow Rate during CIP (gpm)4 70 Max Instantaneous Flow Rate during BW (gpm)5 500 1. Assumes BW cleans every 20 min (377 gallons per clean per skid) 2. Assumes 2 MC cleans per month (1,300 gallons per clean per skid) 3. Assumes 1 CIP clean per month (7,700 gallons per clean per skid). 4. CIP duration is assumed to be 5 hours. One skid is in CIP while the other maintains regular BW cycle 5. Based on peak flow rate through the unit during the forward flush stage of the backwash process.

As presented in Table 3.4, backwashing could potentially generate up to 360,000 gallons per month; however, this estimate is conservative for normal operating conditions. Similar to Supply and Treatment Option No. 1, the actual operating membrane flux will be significantly less than the maximum design flux of 25.6 gfd. Therefore, membrane backwashes will likely be spaced out much wider than every 20 minutes, which will result in lower waste volumes.

As previously discussed, the limiting capacity in the gravity sewer system extending from the Selma Estates treatment facility to the Selma Sewer Pump Station is approximately 325 gpm. Instantaneous waste peak flows under this option would consume 150% of the available sewer capacity. Therefore, it is imperative that a waste equalization tank be installed to limit the discharge flow rate to the sanitary sewer. The equalization tank for this supply and treatment 25

option needs to be approximately 20,000 gallons, which will limit the maximum discharge rate to the sanitary sewer to 30 percent of the limiting capacity (or approximately 100 gpm).

3.1.5 Treatment Chemical Requirements

Membrane process waste may contain solids from the BW process as well as a variety of membrane cleaning chemicals. The wastewater that is discharged into the sanitary sewer near the new Selma facility will ultimately be treated at the Raspberry Falls WWTP. Therefore, the potential effect of the wastewater constituents one th RF WWTP are taken into consideration as part of the supply and treatment option analysis.

The acids used in membrane cleaning can significantly lower wastewater pH which may in turn inhibit the biological processes used to treat wastewater at the RFWWTP. In order to prevent low pH water from being discharged into the sewer system the chemicals in the waste stream should be neutralized. The equalization tank (EQT), previously discussed in section 3.1.4, can be used to facilitate neutralization.

The EQ tank allows the waste streams from all of the membrane cleaning processes (i.e., BW, MC, CIP) to be collected in one place. As not all of the cleaning processes are acids, the non‐acidic and/or the caustic waste streams can be used to neutralize low pH waste. Once the various waste streams have had sufficient time to interact, the neutralized wastewater can be gradually discharged into the sewer system.

There are a variety of different chemicals that may be used for membrane cleaning. The cleaning chemical may be specified by the membrane manufacturer or identified based on characteristics of the source water. A summary of the membrane cleaning processes frequencies and commonly associated chemicals is given in Table 3.5.

Table 3.5: Membrane Cleaning Processes Frequencies and Associated Chemical Constituents

Type of Membrane Cleaning Process Process Parameter Backwash Maintenance Clean Clean‐in‐Place

Frequency 20 minutes Biweekly Monthly Duration 30 seconds 30 minutes 5 hours Chemical Quantity of Chemical Required Citric Acid ‐ 2,000 mg/L 20,000 mg/L Caustic ‐ ‐ 500 mg/L Chlorine ‐ 100 mg/L 500 mg/L

After each membrane cleaning process, there membrane modules undergo a rinse cycle to flush out any residual cleaning chemicals. Total cleaning and rinse cycle waste flows are estimated to be 10,000 gallons per month for treatment option 1 and 20,000 gallons per month for treatment option 2. The total wastes volumes and anticipated chemical loads can be found in Tables 3.6 through 3‐8.

Table 3.6: Maximum Waste Stream Chemical Loads ‐ Citric Acid

Citric Acid2 Loading/ Total Monthly Cleaning Waste Volume Frequency Treatment Event (lbs) Loading (lbs) Option Process (gal/event) (#/month)1

1 MC 1,280 2 0.7 1.4 CIP 7,680 1 44 44 Total Per Unit 45.4 2 MC 2,560 2 1.5 3 CIP 15,360 1 88 88 Total Per Unit 91 1. CIP cleans were assumed to occur once per month, and MC cleans twice per month. While a total waste volume per event of 1,280 gallons is shown for maintenance cleans, 800 gallons of the total is flush water (no chemicals). Only 400 gallons of the waste contains chemicals. Similarly, the CIP’s waste stream’s approximately one third of the total volume will contain chemicals and the remaining volume is flush water (no chemicals). 2. It is assumed that approximately 30% percent of the citric acid will be consumed during the cleaning process

Table 3.7: Maximum Waste Stream Chemical Loads – Chlorine

Chlorine2 Loading/ Total Monthly Treatment Cleaning Waste Volume Frequency Event (lbs) Loading (lbs) Option Process (gal/event) (#/month)1

1 MC 1,280 2 0.2 0.4 CIP 7,680 1 4.6 4.6 Total Per Unit 5 2 MC 2,560 2 0.3 0.6 CIP 15,360 1 9.2 9.2 Total Per Unit 9.8 1. CIP cleans were assumed to occur once per month, and MC cleans twice per month. While a total waste volume per event of 1,280 gallons is shown for maintenance cleans, 800 gallons of the total is flush water (no chemicals). Only 400 gallons of the waste contains chemicals. Similarly, the CIP’s waste stream’s approximately one third of the total volume will contain chemicals and the remaining volume is flush water (no chemicals). 2. It is assumed that approximately 85% percent of the chlorine will be consumed during the cleaning process.

Table 3.8: Maximum Waste Stream Chemical Loads – Caustic

Caustic2 Loading/ Total Monthly Treatment Cleaning Waste Volume Frequency Event (lbs) Loading (lbs) Option Process (gal/event) (#/month)1

1 MC 1,280 2 ‐ ‐ CIP 7,680 1 11 11 Total Per Unit 11 2 MC 2,560 2 ‐ ‐ CIP 15,360 1 22 22

Total Per Unit 22 1. CIP cleans were assumed to occur once per month, and MC cleans twice per month. While a total waste volume per event of 1,280 gallons is shown for maintenance cleans, 800 gallons of the total is flush water (no chemicals). Only 400 gallons of the waste contains chemicals. Similarly, the CIP’s waste stream’s approximately one third of the total volume will contain chemicals and the remaining volume is flush water (no chemicals). 2. Caustic is not expected to be consumed during the cleaning process.

It is expected that some of the cleaning chemicals will be consumed during the cleaning process or diluted by the membrane rinse water. Therefore, cleaning chemical concentrations in the waste stream are expected to be much lower than those provided in Tables 3.6 through 3.8 (see Appendix A for expected waste loads). It is estimated that about 30% of the citric acid and 85% of the chlorine will be consumed during cleaning.

As stated previously, the membrane waste will be collected in an equalization basin. This will allow for the dilution of chemicals and neutralization of the different components of the cleaning cycles. The waste stream will have diluted levels of those constituents; combined, these constituents will neutralize each other (i.e., citric acid neutralization with caustic and chlorine). Under the maximum waste load condition, the waste stream is expected to have a pH of 5.5 and 4.7 for the MC and CIP cleaning processes, respectively (as calculated by Visual MINTEQ, see Appendix A). The MC waste is within the allowable pH of 5.0‐12.0 that can be discharged into the sewer system in Loudoun County. The CIP waste will be neutralized by the addition of caustic as necessary. However, it should be noted that after the consumption of the chemicals during cleaning, the waste is expected to have a pH of 6.8 and 5.9 for the MC and CIP cleaning processes, respectively (calculated by Visual MINTEQ). Therefore, it is not expected to have any needs for the neutralization of the waste even after CIP cleaning. Moreover, any residual chlorine will be quenched prior to discharge and thus, the waste can be safely discharged to community sewer system. The waste generated from the membrane treatment system will be conveyed to Raspberry Falls WWTP. The ability to collect and neutralize the large instantaneous flow and to discharge it at a low manageable rate will allow membrane cleaning procedures to be coordinated with wastewater treatment plant operations. As membrane wastes are often disposed of into the sanitary sewer for ultimate treatment at a WWTP, the disposal method proposed is considered a “tried‐and‐true” method of dealing with membrane wastes.

3.2 Granular Activated Carbon (GAC)

Though membrane treatment was selected to provide treatment of GUDI, some consideration has been given to the removal of synthetic organic compounds (SOCs) as extremely low concentrations SOCs were previously detected in in some of the supply wells. SOCs include a variety of chemicals, such as aromatic hydrocarbons, pesticides, herbicides, and dyes. Many SOCs are currently regulated by the Environmental Protection Agency in drinking water systems because of their inherent toxicity. While the SOC concentrations observed to date are well below established limits (i.e., two to four orders of magnitude below their regulatory limits), future spikes could be encountered due to the nature of the local groundwater system.

SOCs such as pesticides can enter the groundwater through surface runoff. The karst terrain in and around the study area is sometimes unable to provide significant retardation or dilution of SOCs between their sources and the supply wells. The most effective way to remove SOCs is by activated carbon adsorption. Therefore, the future addition of a Granular Activated Carbon (GAC) system in the water treatment process is presented for consideration as part of the study.

Source water characteristics and GAC contactor placement in the water treatment train are important things to consider when designing a GAC system. Reactor configuration, size and backwash requirements are important items to consider as well. These item are discussed below.

3.2.1 GAC Contactor Configuration

Two important factors to consider when configuring a GAC system include flow type and direction. Flow to the contactor may be driven by pressure or gravity and flow through the contactor may be either upwards or downwards. The preliminary membrane treatment design includes a pressurized membrane skid that discharges to a water storage tank. To accommodate a GAC contactor between the membranes and the tank, a pressurized vessel is be required. For this application, a downflow orientation is recommended as an upflow orientation would allow the media bed to expand, which could lead to premature SOC breakthrough.

3.2.2 GAC Contactor Size

Proper sizing of the GAC contactors is essential for efficient operation. Empty bed contact time (EBCT) is generally used as a preliminary design criterion for these GAC systems. The EBCT represents the hydraulic residence time in the media bed if the media bed were empty. The EBCT for GAC contactors can range from 5 minutes to several hours with a typical range being 5 to 30 minutes. In general, a longer EBCT will lead to longer carbon replacement intervals. Because the SOC concentrations are likely to remain very low in the Raspberry Falls and Selma Estates groundwater sources, the preliminary designT EBC was considered to be approximately 15 minutes. More detailed design evaluations, including bench and pilot scale tests for contaminant breakthrough modeling, are generally recommended to design full‐scale contactors.

During operation, any SOCs present in the groundwater supply will be adsorbed to the activated carbon starting at the influentd en of the contactor. As the carbon at the influent end of the contactor becomes exhausted, the adsorption zone will move slowly towards the discharge end until the contaminants breakthrough. Backwashing in this scenario is not recommended because

the bed will expand during a backwash cycle. Bed expansion will mix the exhausted carbon with the fresh carbon and result in premature breakthrough of the SOCs.

Several manufacturers offer skid mounted GAC systems. A standard design offered by the manufacturers for the design flows in this application consists of 20,000 pounds of activated carbon per reactor. Table 3.9: provides a design summary of the 20,000‐pound units.

Table 3.9: Preliminary GAC Design Summary

Parameter Design Value Configuration Two parallel pressure vessels Flow Direction Downflow Approx. System Footprint 15 ft x 30 ft Max. Pressure 20 psi Design Flow per Reactor 305 gpm Approx. Headloss @ Design Flow 2 psi Vessel Diameter 10 ft Media Height 8 ft Media Volume per Reactor 628 ft3 Media Weight per Reactor 20,000 lb EBCT (5‐30 min. typ.) 15.4 min Filtration rate (2‐5 gpm/ft2 typ.) 3.9 gpm/ft2

Based on historical source water monitoring, treatment for removal of SOCs is not required and it is not recommended that GAC contactors be installed at this time. However, for facility planning purposes during development of the long‐term supply and treatment options, space has been allotted on the combined treatment facility site for future addition of these treatment units. This space is depicted on Figures 3.2 and 3.3 for Supply and Treatment Option Nos. 1 and 2, respectively.

3.3 Finished Water Storage

The demand for water fluctuates throughout the day, while water is produced at a constant rate. Therefore, there may be instances where more water is produced than required, or vice versa. Storage tanks help minimize the effects of demand fluctuations on the treatment process by providing a ready reservoir of treated water to pull from. Essentially, the water storage tanks act like a buffer between to allow treatment of water to remain relatively constant while the system demands fluctuate.

Water storage tank capacity requirements are typically determined by evaluating the regulatory, equalization, fire flow, and emergency requirements. Each of these factors is described further below. Efforts have been made to keep or enhance the current level of service at Selma Estates and Raspberry Falls. Currently Selma receives a combined pumping capacity of 750 gpm (500 gpm fire flow and 250 gpm peak demand) while Raspberry receives a combined pumping capacity of 264 gpm.

Functional Category 1, Regulatory Requirements This category represents the storage volume required by applicable statutes, such as the Virginia Administrative Code. The Commonwealth of Virginia Department of Health has responsibility of

regulating waterworks under Chapter 590. Section 690 of Chapter 590 stipulates the minimum required waterworks capacity.

The Virginia Department of Health Waterworks Regulations (VDHWWR) require a minimum water storage of 200 gallons per equivalent residential connection (ERC). An ERC is defined as a demand of 400 GPD. For example, a system water demand of 400,000 GPD equates to 1,000 ERC’s regardless of the actual number service connections.

Functional Category 2, Equalization Requirements This category represents the storage volume required to provide water to the distribution system when the demand for water exceeds the rate of supply from the treatment facility. Equalizing storage allows water production and pumping facilities to be sized for maximum daily demand (MDD), rather than peak hour demand, and allows them to operate at a relatively constant rate. Equalizing storage is calculated by analyzing daily demand fluctuations and operational time. The new Selma Estates combined treatment facility would be designed to receive source water for 800 min per day facilitate sustainable aquifer management. Therefore, under this operation scenario, the equalization volume must be capable of stabilizing system operation and supplying water during peak demands while the well pumps are out of service.

Functional Category 3, Fire Flow Requirements This category represents the storage volume of water required to be held in reserve for firefighting. Fire flow volume is calculated using a fire flow rate multiplied by a fire duration. The Insurance Services Office, Inc. (ISO), Loudoun Water, and the American Water Works Association (AWWA) all offer guidelines for estimatinge fir flow rate and/or duration.

 Fire flow. In general, ISO requirements for fire flow capability in residential communities depend on its population density. A flow rate of 500 gpm was used for purposes of design as Selma Estates and Raspberry Falls are considered to be rural communities. Fire flow capability is one of the items considered in ISO’s Fire Suppression Rating Schedule, which establishes fire insurance rates. A fire flow rate of 500 gpm falls within the accepted values of the ISO.

 Fire Duration. A fire flow duration of two hours was used for this evaluation based on AWWA manual M31. M31 recommends a two fire flow duration for fire flows less than 2,500 GPM.

Functional Category 4, Emergency Requirements This category represents the storage volume required to provide water during an emergency, such as the loss of a supply well or a transmission line break between a well and the treatment plant. Emergency storage requirements vary by utility but are typically based on a few key factors such as system reliability/redundancy, emergency type, and typical emergency frequency and duration. For example, if a system has more than one source of water and emergency power, less emergency storage may be required; whereas if a system only has a single source of water and no emergency power, greater emergency storage may be required. For purpose of analysis, emergency storage was calculated based on the assumption that two production wells were out of service for 24 hours.

Based on the requirements outlined above, the recommended design storage tank volume for Supply and Treatment Option No. 1 is 220,950 gallons and 323,930 gallons for Supply and Treatment Option No. 2. For the first option, the storage requirement based on locally accepted design standards for Community 31

Water System storage tanks governed the capacity of the potable water storage tank. For the second option, the recommended storage volume was selected based on providing storage equivalent to the equalization and emergency storage needs. The sum of volumes for these two categories was greater than the regulatory requirement. Summaries of the water demands and the storage volumes associated with each functional category are presented in Tables 3.10 and 3.11.

Table 3.10: Supply and Treatment Option No. 1 Potable Water Storage Tank Requirements

Water Demands1 Storage Requirements (gallons) Total Peak Fire Min. Parameter Avg. Day Max. Day Regulatory Equalization4 Emergency Hour Flow Tank Volume gallons 70,704 196,400 98,2002 72,013 60,000 4,400 220,950 gpm 49 136 332 220,9503 1. Based on 491 residential connections at 400 gpd/connection. 2. VDH‐ Regulations (pending amendment calls for a minimum of 1/2 max day demand). 3. Locally accepted design standard for Community Water System storage tanks. 4. Equalization storage is based on 12‐hour supply pumping.

Table 3.11: Supply and Treatment Option No. 2 Potable Water Storage Tank Requirements

Water Demands1 Storage Requirements (gallons) Total Peak Fire Min. Parameter Avg. Day Max. Day Regulatory Equalization4 Emergency Hour Flow Tank Volume gallons 159,084 441,900 220,9502 162,030 60,000 161,900 323,930 gpm 110 307 516 220,9503 1. Based on 491 residential connections at 900 gpd/connection. 2. VDH‐ Regulations (pending amendment calls for a minimum of 1/2 max day demand). 3. Locally accepted design standard for Community Water System storage tanks. 4. Equalization storage is based on 12‐hour supply pumping.

The existing Selma Estates potable water storage tank is a glass‐lined, bolted steel tank consisting of a stack of steel “rings”, with an operating storage capacity of 150,000 gallons. However, the useable capacity of the tank will be reduced in the near future in order to maintain system storage fora Giardi lamblia inactivation. The capacity of these style tanks can typically be expanded by providing additional rings; however, based on discussions with the tank manufacturer, only one additional ring can be provided. Therefore, the existing storage tank must be replaced with a new storage tank under both supply and treatment options. The new storage tank will be sized properly to account for both communities

3.4 Irrigation Storage

The proposed Supply and Treatment Option No. 1 requires two new irrigation systems to be installed at Selma Estates and Raspberry Falls. The components of each irrigation system include wells, pumps, storage tanks, and distribution piping. Dedicated groundwater wells will serve as the supply source for each system and will provide untreated groundwater directly to each storage tank. Booster pumps will be used to provide water at the necessary flows and pressures to the irrigation piping networks.

A total of two irrigation storage tanks (IST) will be provided; one at Selma and one at Raspberry Falls. The size of each IST was based on providing one day of irrigation storage plus a reserve volume. Table 3.10 provides a summary of the irrigation storage requirements. The IST volumes for the Selma and Raspberry Falls systems are 173,125 gallons and 126,875 gallons, respectively.

Table 3.12: Supply and Treatment Option No. 1 Non‐Potable Water Storage Tank Requirements

Water Demands1 Storage Requirements (gallons)

Daily Water Usage Minimum Water Reserve Total Min. Tank Area Connections (GPD) Storage Storage2 Volume

Selma 277 138,500 138,500 34,625 173,125 Raspberry Falls 203 101,500 101,500 25,375 126,875 Total 300,000 1. Based on 500 gpd/connection demand 2. Reserve storage is based on 25% of the daily water usage 33

3.4 Water Distribution

A combination of pumps and pipes are used to transport raw water from its source, through treatment and storage, and out to the end user. The hydraulic characteristics of the distribution system dictate the pump and pipe sizes required transport water from one location to another.

3.4.1 Hydraulic Modeling and Design Data

An existing hydraulic model with the Selma Estates and Raspberry Falls distribution systems combined was provided to Hazen and Sawyer (H&S) by Loudoun Water for use in the study. Upon inspection, the model was found to include information on the existing hydraulic infrastructure such as pumps, pipes, valves, and water storage tanks. In order to determine the size of the hydraulic infrastructure (i.e., pumps and pipes) required to convey water from supply through treatment, the existing hydraulic model was updated to reflect anticipated flow demands under long‐term Supply and Treatment Option Nos. 1 and 2. Potable and irrigation demands were assigned to each node in the model as follows:

 Supply and Treatment Option No. 1: Combined Potable Water Treatment with Separate Irrigation o Potable Water: 184 gpd/connection (average day4) and 400 gpd/connection (maximum day) o Irrigation Only: 500 gpd/connection

 Supply and Treatment Option No. 2: Combined Mixed Use Water Treatment o Mixed Use Water (Potable Water and Irrigation): 484 gpd/connection (average day) and 900 gpd/connection (maximum day) The potable and irrigation water demands and associated hydraulic design criteria for Supply and Treatment Option No. 1 are summarized in in Tables 3.13 and 3.14, respectively. The total water demand and associated hydraulic design criteria for Supply and Treatment Option No. 2 are summarized in in Table 3.15.

Table 3.13: Supply and Treatment Option 1 Total Potable Water Demands and System Design Criteria

Total Flow Minimum Pressure Demand Parameter Demand (gpm) (psi) Average Day (ADD) 63 40 Maximum Day (MDD) 136 40 Peak Hour (PHR) 333 40 Maximum Day (MDD) + Fire Flow 636 20 Peak Hour (PHR) + Fire Flow 833 20

4 All average daily flow values presented herein are taken from the Recommended Demand Management Program developed for Loudoun water by Malcolm Pirnie in October of 2008. 34

Table 3.14: Supply and Treatment Option 1 Total Irrigation Demand and System Design Criteria

Minimum Irrigation Maximum Irrigation Number or Flow per Total Flow (gpd) System Pressure System Pressure Connections connection (psi) (psi (gpd) Selma Raspberry Selma Raspberry Selma Raspberry Selma Raspberry Estates Falls Estates Falls Estates Falls Estates Falls 138,50 50 50 165 165 500 277 203 101,500 0 Note: 1. A minimum pressure of 50 psi is required for rotary sprinklers (associated with in ground irrigation systems) to perform.

Table 3.15: Supply and Treatment Option 2 Mixed Use Water Demands and System Design Criteria

Total Flow Minimum Pressure Demand Parameter Demand (gpm) (psi) Average Day (ADD) 165 40 Maximum Day (MDD) 307 40 Peak Hour (PHR) 516 40 Maximum Day (MDD) + Fire Flow 807 20 Peak Hour (PHR) + Fire Flow 1016 20

3.4.2 Treated Water Distribution

After the new flow demands were entered into the hydraulic model, the model was run for each supply and treatment option to determine whether or not the existing distribution infrastructure could be re‐used. Maps of system pressures and available fire flow for the various scenarios analyzed can be found in Appendix A.

Pipelines and Pressure Regulating Valves Per the initial model results, the existing pipelines are sufficiently sized to convey treated water to each resident. However, it should be noted that model predicts low pressures (i.e., less than 40 psi) in some parts of the system due to the setting on some of the existing pressure regulating valves (PRV). Many of these low pressure areas can be eliminated by adjusting the valve settings. Of the three existing PRVs, for example, the Selma and Frostleaf PRVs are set at a hydraulic grade line (HGL) of 515 ft. To maintain system pressures above 40 psi, these PRV settings would need to be changed to a HGL of 530 ft. This change would increase the maximum pressures in the lower Selma zone from 101 psi to 109 psi.

Pumps Per the initial model results, the existing constant speed booster pumps at the Selma Estates treatment facility were able to provide the required flow but at a pressure exceeding 150 psi for average and maximum day demands. Therefore additional model runs were performed to assess 35

whether the existing Selma Estates booster pumps could be re‐used by performing design modifications. One design modification analyzed was the use of variable frequency drives (VFDs). Unlike pumps with constant speed drives, which are set to perform at one set flow and pressure, pumps with VFDs can be adjusted to perform over a range of flows and pressures. The hydraulic model was re‐run assuming that VFDs could be added to the existing Selma Estates booster pumps. While model results predict that pump performance would improve overall, there would still be demand scenarios where pump performance would be questionable. Existing booster pump performance with VFDs under Supply and Treatment Option Nos. 1 and 2 is illustrated in Figures 3.2 and 3.3, respectively.

Figure 3.2: Supply and Treatment Option No. 1, Performance of Existing Selma Estates Pumps with New VFDs

Per Figure 3.2, the pump operating points for Maximum Day Demand (MDD), Maximum Day Demand with fire flow (MDD + 500 gpm fire flow) and Peak Hour (PHR) Demand fall near the middle of the pump curve which is desired for optimal pump performance. The operating point for Average Day Demand (ADD) falls on the left end of the curve and the operating point for Peak Hour demand with fire flow (PHR + 500 gpm fire) falls on the right end of the curve. In general, a pump operating at either end of its curve tends to have shorter useful lifespans and higher maintenance costs. Based on this analysis, even if the existing Selma Estates booster pumps were retrofitted with VFDs, they would still be insufficient to address the anticipated average day and peak hour plus fire flow operating conditions under this long‐term option.

Figure 3.3: Supply and Treatment Option No. 2, Performance of Existing Selma Estates Pumps with New VFDs

Per Figure 3.3, the pump operating points for ADD, MDD + 500 gpm fire and PHR fall near the middle of the pump curve, which is desired for optimal pump performance. The operating point for Peak Hour demand with fire flow (PHR + 500 gpm fire) is no longer on the pump curve. In general, a pump operating at either end of its curve tends to have shorter useful life and higher maintenance costs. Based on this analysis, even if the existing Selma Estates booster pumps were retrofitted with VFDs, they would still be insufficient to address the anticipated peak hour plus fire flow operating condition under this long‐term option.

As the hydraulic model predicted that the existing Selma Estates booster pumps would not be able to meet the flow demand under some conditions (despite the addition of VFDs), the model was re‐run with the assumption that new booster pumps would be installed as part of the overall facility modifications at Selma Estates. A total of five (5) new pumps (4 duty, 1 spare) are required to meet the range of flow demands. Three large main pumps (2 duty, 1 spare) would be used to meet the majority of the flow demands, while two small jockey pumps would be used to meet the average and minimum system demands.

Despite the addition of new pumps, it should be noted that some distribution system locations will only receive a minimum fire flow of 300 gpm at 20 psi (instead of the desired minimum of 500 gpm at 20 psi). This is due to conveyance limitations inherent in the existing distribution system piping. This limitation aside, the model results indicate that the new pumps would be able to perform over the entire range of flow demands for both treatment options. Figures 3.4 and 3.5 present the operating points for the new pump for each the flow demands.

Figure 3.4: Supply and Treatment Option No. 1 ‐ Performance of New Selma Estates Pumps

Figure 3.5: Supply and Treatment Option No. 2, Performance of New Selma Estates Pumps

3.4.3 Irrigation Water Distribution

Under Supply and Treatment Option No. 1, untreated groundwater will be used for outdoor (irrigation) use at Selma Estates and Raspberry Falls. New distribution piping is needed in each community to facilitate this option. The non‐potable distribution system for each community was initially sized based on the total number of irrigation connections (i.e., 203 at raspberry and 277 at Selma) and the maximum irrigation flow per connection (i.e., 500 gpd/connection). However, preliminary hydraulic analyses indicated that relatively large pipes would be required to simultaneously convey the maximum irrigation flow to each connection.

In general, the larger the pipe the more expensive it is to procure and install. In addition, larger pipes tend to require larger excavations. Therefore, in order to minimize capital costs and community disruption, smaller diameter irrigation systems were investigated.

Additional hydraulic analyses revealed that small diameter irrigation systems could be used in each community if each community is broken into two irrigation zones. Under this approach, each zone would be irrigated for 2 or 4 hours at different times. A summary of the irrigation alternatives are presented in Table 3.16 below.

Table 3.16: Supply and Treatment Option No. 1 ‐ Irrigation Alternatives

Total Flow per Required Irrigation Pump Flow (gpm) Irrigation Alternative Connection Alternative1 Description Selma Estates Raspberry Falls (gpd) 1 4.2 gpm for 2hrs 500 577 423 2 2.1 gpm for 4hrs 500 289 211.5 Notes: 1. Each alternative assumes that only one zone in each community will be irrigated at a time. For Selma Estates, a maximum of 139 connections would be irrigated at a given time. For Raspberry Falls, a maximum of 102 connections would be irrigated at a given time. The minimum pressure goal for each connection was 50 psi.

Based on the revised non‐potable water supply concept (staggered irrigation), one new irrigation system, consisting of 3, 4 and 6‐inch diameter pipes, would be installed in each community, parallel to the existing water distribution system. New irrigation pumps would also be installed to distribute irrigation water flow through the system. The total length of irrigation pipe by diameter is presented in Table 3.17. Irrigation pump requirements are summarized in Table 3.18.

Table 3.17: Supply and Treatment Option No. 1 ‐ Irrigation Pipe Summary

Irrigation Pipe Pipe Length Diameter (in) (ft) 3 57,592 4 13,296 6 7,091 Total 77,979

Table 3.18: Supply and Treatment Option No. 1 ‐ Irrigation Pump Summary

Irrigation Alternative Irrigation Pump Parameters Community Alternative1 Description Flow (gpm) Head (ft) Selma 577 323 1 4.2 gpm for 2hrs Raspberry 423 229 Selma 289 245 2 2.1 gpm for 4hrs Raspberry 212 194 Note: 1. One pump is used to provide iteration flow for each community under each irrigation alternative; no back‐up irrigation pumps are provided.

Raspberry Falls and Selma Estates Study of Long Term Options January 6, 2015

4.0 Summary of Treatment and Distribution System Concepts

4.1 Supply and Treatment Option No. 1: Combined Potable Water Treatment with Separate Irrigation

Under this long‐term supply and treatment option, one new membrane treatment facility would be constructed to treat and supply potable water for the communities of Selma Estates and Raspberry Falls. The new combined treatment facility would be constructed on the site of the existing Selma Estates treatment facility. In addition to the combined treatment facility two new irrigation systems would be constructed to provide untreated groundwater to each community for irrigation use. Water for potable use would be supplied via the existing Selma Estates wells, while non‐potable irrigation water would be provided via two (2) new Selma Estates wells and via the existing Raspberry Falls wells. The design capacity of the potable and non‐potable systems for this option is presented in Table 4.1.

Table 4.1: Supply and Treatment Option No. 1 System Capacities

System Capacity (gpm) Irrigation Irrigation System Description Potable Alternative 11 Alternative 21 Combined Membrane Treatment 136 ‐ ‐ Irrigation System 1 ‐ Selma ‐ 577 289 Irrigation System 2 ‐ Raspberry ‐ 423 212 Note: 1. Based on irrigation pump flow rate and dependent on irrigation alternative chosen, see section 3.4.3.

As previously discussed, the membrane treatment process is comprised of a number of different components such as the membranes, pumps, strainers and storage tanks. An overview of the membrane treatment process train was previously discussed in Section 3.1.2. This supply and treatment option also requires the construction of a non‐potable distribution network within each community, as well as new non‐potable supply infrastructure (tank and pumps) for Selma Estates. The number and size of each major component required under this option is summarized in Table 4.2 below.

Table 4.2: Supply and Treatment Option No. 1 ‐ Major Treatment and Distribution Components

Process Component Number of Units Size (Each) Combined treatment Facility Break Tank (7 ft diameter) 1 2,050 gallons Membrane Filtration Unit 2 10, 800 sf Equalization Tank 1 10,000 gallons Potable Water Storage Tank 1 220,950 Booster Pumps, main 3 425 gpm@ 238 TDH Booster Pumps, jockey 2 65 gpm@ 218 TDH Irrigation Systems Irrigation Water Storage Tank, 1 173,125 gallons Selma Estates Irrigation Pump1, Selma 577 gpm@ 323 TDH or 1 Estates 289 gpm@ 245 TDH Irrigation Water Storage Tank, 1 126,875 gallons Raspberry Falls Irrigation Supply Pump1, 1 423 gpm@ 229 TDH or Raspberry Falls 212 gpm@ 194 TDH Non‐Potable Distribution 1 77,979 linear feet Network Note: 1. Pump size depends on irrigation alternative chosen, see section 3.4.3.

Membrane Treatment Facility Layout The new membrane treatment facility would be built on the site of the existing Selma Estates Treatment plant. The current treatment building would be expanded by 1200 square feet to house the new membrane filtration equipment and associated appearances. The existing storage tank would be demolished and a new storage tank built to provide the required storage capacity. The existing driveway would also be enlarged to provide access to the new facility. A layout of the proposed facility is presented in Figure 4.1.

Irrigation Infrastructure Under this alternative water for irrigation would be provided to the residents of Selma and Raspberry Falls via two new irrigation systems. One new irrigation system consisting of 3, 4 and 6‐ inch diameter pipes would be installed in Selma Estates, parallel to the existing water distribution system. Similarly, one new irrigation system consisting of 3, 4 and 6‐ inch diameter pipes would be installed in Raspberry Falls, parallel to the existing water distribution system.

4.2 Supply and Treatment Option No. 2: Combined Mixed Use Water Treatment

Under this supply and treatment option, one new membrane treatment facility would be constructed to treat and supply potable water for mixed use (i.e., potable and outdoor use) to the communities of Selma Estates and Raspberry Falls. The new combined treatment facility would be constructed on the site of the existing Selma Estates treatment facility. Under this option water for mixed use would be obtained from a combination of existing Selma Estates and Raspberry

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Falls wells. Under this option flows from the three existing Raspberry Falls wells would be sent to the existing Raspberry Falls Storage tank and then pumped to Selma Estates for treatment. The design capacity of the treatment system is presented in Table 4.3.

Table 4.3: Supply and Treatment .Option No 2 System Capacity

Total Demand (gpd) Process Description Mixed Use Combined Membrane Treatment 441,900

Table 4.4: Supply and Treatment Option No. 2 ‐ Major Treatment and Distribution Components

Process Component Number of units Size Break Tank (10 ft diameter) 1 4,600 gallons Membrane Filtration Unit 2 24,340 sf Equalization Tank 1 20,000 gallons Potable Water Storage Tank 1 323,930 Booster Pumps, main 3 500 gpm@ 181 TDH Booster Pumps, jockey 2 165 gpm@ 189 TDH

Membrane Treatment Facility Layout The new membrane treatment facility would be built on the site of the existing Selma Estates Treatment plant. The current treatment building would be expanded by 1400 square feet to house the new membrane filtration equipment and associated appearances. The existing storage tank would be demolished and a new storage tank built to provide the required storage capacity. The existing driveway would also be enlarged to provide access to the new facility. A layout of the proposed facility is presented in Figure 4.2.

Irrigation Infrastructure Under this alternative water for irrigation would be provided to the residents of Selma and Raspberry Falls via the existing water distribution piping. No new irrigation facilities are required.

4.3 Preliminary Cost Estimates

A preliminary capital cost estimate was developed for each water supply and treatment option. As the project is in the conceptual design phase it falls within Class 4 of the estimate classes set forth by the Association for the Advancement of Cost Engineering (AACE). Class 4 estimates have a typical accuracy of ‐15% to ‐30% on the low side and +20% to +50% on the high side. For the purposes of this study ‐15% was used as the lower boundary and +30% was used as the higher boundary. The estimates are based on a combination of estimated equipment quantities and anticipated site activities. Engineering judgment was used for some project components such as the Electrical, HVAC, and 43

fire protection systems. Budget quotes from manufacturers were used for major equipment items, such as the storage tanks, pumps, and membrane systems. Other unit cost data was obtained from RS Means.

All costs are in 2014 dollars (ENR November 2014) and include markups of 7% for general conditions (i.e., indirect costs such as mobilization, permitting, etc.), 21% for contractor overhead and profit and a 30% contingency (reflective of the current preliminary‐engineering level design). A summary of the estimated range of capital costs by alternative is presented in Table 4.5 below. Detailed cost estimates for each alternative are contained in Appendix B of this report.

Table 4.5: Capital Cost Summary

Supply and Description Capital Cost (millions) 1 Treatment Option Combined Treatment with Separate 1 $9.7 to $14.8 Irrigation Systems 2 Combine treatment for Mixed Water use $5.5 to $8.4 Note: (1) Costs rounded to the nearest $100 thousand.

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5.0 Triple‐Bottom Line Sustainability Analysis – Financial, Social and Environmental

5.1 Introduction

A triple bottom line (TBL) evaluation framework was used to compare the two water supply and treatment options under consideration. A TBL framework differs from a conventional financial analysis in that it takes social and environmental impacts into account during the selection of a preferred option. Under a TBL analysis, dthe costs an benefits of the options as they relate to economic, environmental, and social impact criteria are estimated and compared. Examples of economic criteria include present value of costs and the impact of an investment in creating jobs and income. Examples of environmental criteria include air and water quality impacts and regulatory compliance. Examples of social criteria include impacts to public health and safety and the distribution of benefits and costs among sub‐populations. Of the three TBL components the economic element is expected to have the greatest impact on the community given the capital cost of each project compared to the size of the benefiting community. Adverse environmental impacts are expected to be minor due to the limited geographical scope and modest construction activity of the proposed projects. Finally, adverse social impacts are expected to be very minor.

The TBL criteria are traditionally measured using metrics that differ from one another. For example, economic criteria may be measured in monetary units while environmental criteria may be measured in pollutant concentrations. In contrast, social criteria can be purely qualitative. Sometimes, non‐economic criteria may be more important to decision makers. For example, large and land intensive infrastructure projects (e.g., dams or highways) usually result in greater environmental and social impacts than physically smaller and less intrusive projects (e.g., schools, hospitals). Hence the TBL evaluation may require a greater weighting of or emphasis on environmental and/or social impacts relative to the financial costs and benefits.

There are various methodologies to normalize and weight the different criteria so that they can be compared on a similar (i.e., “apples to apples”) basis. These include scale‐based scoring systems (1‐10 point scores) for subjective or qualitative criteria, and data‐based scores, for criteria based on numerical data that are transformed to a scale‐based score.

5.2 Criteria, Scoring and Weighting

The TBL analysis contained herein examines two proposed water supply and treatment options that will occupy a small geographic area and affect a relatively small population. The two options were evaluated with respect to the five evaluation criteria listed in Table 5.1, which also presents the scoring used for each TBL criteria. The scoring and weighting system assigns points to an option only if it is preferred to the other option under the same criterion. The preferred option for the economic criterion received a score of “4”, while the preferred option for the environmental and social criteria received scores of “2” and a “1”, respectively. Hence, a maximum score of 10 was possible if one treatment supply option was preferable to the other option for all criteria evaluated. The number of points assigned to each criterion was based on allocating a higher weight (40 percent) to economic considerations and lower weights to each environmental (20 percent) and social factor (10 percent).

Table 5.1: Triple Bottom Line Analysis Criteria 45

Economic Environmental Social Lowest Greenhouse Gas Emissions Better Protection of Public Health (Score = 2) (Score = 1) Lowest Capital Cost (Score = 4) Greater Aquifer Sustainability Better Quality of Life (Score = 1) (Score = 2)

Criteria selection for the economic, environmental and social categories is discussed in the evaluation sections below.

5.3 Evaluation using Economic Criteria

Total annualized cost was selected as the sole economic criterion because the project is too small to generate other measureable economic impacts such as long‐term employment or additional business or tax revenue. In this evaluation, the option’s cost is the only relevant economic discriminator. The total annualized economic cost of a water treatment system consists of two components:

 Cost to construct the water treatment system (Capital Cost); and  Cost to operate and maintain the water treatment system (O&M Cost).

Capital cost estimates, for STO1 and STO2 are presented in Table 5.2. To account for uncertainty in final design requirements, the study developed a range of capital costs to encompass a lower bound estimate that is 85 percent of the estimated total itemized cost and an upper bound estimate that is 130 percent of the estimated total itemized cost. The last two columns of the table provide the range of cost differences between STO1 and STO2.

The estimated capital cost of STO1 ranges from $9.7 million to $14.8 million. For STO2, the estimated capital cost ranges from $5.5 million to $8.4 million. STO1’s estimated capital cost is $4.2 million to $6.4 million greater than the estimated capital cost of STO2. Most of this capital cost difference is due to the need to install an irrigation water distribution system in each community under STO1.

Table 5.2: Estimated Capital Costs of Water Supply and Treatment Options

STO1 – Combined Cost Difference Between STO2 ‐ Combined Cost Item Treatment, Separate STO1 and STO2 (STO1 ‐ Treatment, All Uses Irrigation STO2) Low High Low High Low High Capital Cost $9,659,392 $14,773,187 $5,523,658 $8,447,947 $4,135,734 $6,325,240 Annualized Capital Cost (a) $357,027 $546,042 $204,164 $312,250 $152,864 $233,791 (a) The capital cost was amortized over 30 years at an inflation‐free interest rate of 0.68 percent. This calculation is also the annual debt service in 2014 dollars.

O&M costs should also be included, especially if these costs are large and if there are significant O&M cost disparities between the two options. This study did not quantify the O&M costs because there are too many unknowns at this time regarding operational strategy to quantify and differentiate O&M costs for the two options. Instead, a qualitative assessment of the operational requirements was performed which indicated that for both options O&M costs would be a small fraction of the annualized capital costs. Hence, even if there was an O&M cost advantage for STO1, it would unlikely overcome the large capital cost disadvantage it bears compared to STO2.

Therefore, based on the economic criterion, STO2 is preferable to STO1 because its cost is significantly lower. Using the scoring method developed for this criterion, STO2, the preferred option, receives 4 points.

5.4 Evaluation using Environmental Criteria

The construction and operation of the proposed water treatment system would not result in major adverse environmental impacts as neither option would generate hazardous wastes, emit toxic air pollutants, nor damage sensitive environments. However, both options require energy inputs to operate and have a “Carbon Footprint” which can be measured. Secondly, both options withdraw water from the same aquifer but could have a differential impact on its long‐term sustainability. Hence, the two options were compared based on their impact on Carbon Dioxide (CO2) emissions and the sustainability of the aquifer.

5.4.1 Impact on Carbon Emissions

Table 5.3 presents estimated kilograms of carbon dioxide equivalent (CO2e) generated during the production and transmission of electricity used by the treatment plant and from the production and transportation of chemicals used at the plant under both options. Most of the generated CO2e is attributable to electricity use by the plant. As would be expected, STO1 produces lower quantities of CO2e than does STO2 because less water is being treated under STO1. STO1 is expected to produce an estimated 322,000 kg of CO2e annually while STO2 is expected to produce 341,000 kg of CO2e. Using this criterion, STO1 is the preferred alternative because it produces 19,000 kg (5.6 percent) fewer CO2e emissions per year than STO2. Therefore, under the scoring system developed for this criterion, STO1 receives 2 points.

Table 5.3: Estimated Kilograms of Carbon Dioxide Equivalents Generated Annually by Each Option

kg CO2e Electricity Option Chemical Chemical Production and Total Transport Production Transport STO1 ‐ Separate Irrigation 321,000 189 931 322,120 Water Supply

STO2 ‐ Combined Irrigation 339,000 417 1,860 341,277 and Indoor Water Supply

Difference between STO1 ‐18,000 ‐228 ‐929 ‐19,157 and STO2

To put these emission levels into perspective, this study used a methodology developed by the United States Government Interagency Working Group that has been used to estimate the social cost of carbon (SCC) for regulatory impact analysis. The most recent report states that, “The SCC is meant to be a comprehensive estimate of climate change damages and includes, but is not limited to, changes in net agricultural productivity, human health, and property damages from increased flood risk.” 5 For the year 2014 and using a 3 percent annual discount rate, this value in 2014 dollars is $35.62 per metric ton of CO2 reduction. Applied to the 19,157 kg reduction in CO2e or 19.157 metric tons per year, the annual avoided social cost associated with choosing STO1 over STO2 is $682 per year.

5.4.2 Impact on Aquifer Sustainability

Both options would provide residents with a total of 900 gallons of water per household per day. The primary difference is that under STO1, 500 gallons of this total would be provided using a separate distribution system and the water would be provided for irrigation use only. Ostensibly, aquifer drawdown rates would be identical for both options.

STO2, however, could potentially result in a higher drawdown and a more rapid depletion of the aquifer. The reason for this difference is that under STO2, the system would provide water on demand for both indoor and outdoor uses. Hence, if the communities’ households cumulatively exceed their daily use of 900 gal/day/household, the system will continue to pump water from the aquifer to refill the treatment tanks and maintain system pressure. In contrast, under STO1, excessive use of the irrigation water beyond the system’s design capacity would not result in further groundwater drawdown because the system would shut down once the daily irrigation water allotted has been consumed. The system would restart when the next 24‐hour cycle commenced. In short, under STO1 there is a true cap on the daily provision of irrigation water.

Under STO1, the water would also be provided on demand. However, it is less likely that community daily overuse would occur because the potable water would be distributed for internal household and minor outdoor use only (e.g., clothes and dish washing, drinking, cooking, car washing, and potted plants). It would be unlikely that households would divert large amounts

5 http://www.epa.gov/climatechange/EPAactivities/economics/scc.html 48

of potable water for lawn irrigation. The difference in the amount of water consumed under STO1 versus STO2 is not known.

Based on the potential impact to aquifer sustainability, STO1 is preferred option and receives 2 points.

5.5 Evaluation using Social Criteria

The two social criteria chosen for this evaluation were impacts to public health and to quality of life as described below.

5.5.1 Public Health

Under STO2, the mixed‐use distribution system would deliver treated potable water to households for indoor and outdoor uses (including irrigation). The quality and safety of the potable water delivered under this option would be continuously monitored and therefore the public health risk would be the same as for any centralized water treatment system. The same level of risk would apply to the potable water system under STO1.

Under STO1, irrigation water would be obtained from groundwater wells and delivered untreated for irrigation use as neither State nor Federal law requires monitoring of irrigation water quality. In the event that the well water quality becomes contaminated with pathogenic organisms, humans and pets exposed to the irrigation water could become ill, particularly if the water is ingested. Young children playing in the sprinklers or on a recently irrigated lawn would be the most likely scenarios of human exposure to water borne pathogens if the aquifer were to become contaminated.

The degree to which STO1 poses an elevated health risk would depend on contamination levels of the well water, the time elapsed between contamination and detection, and the demographics of the households. While the public health risk would be small, it is a risk that is associated only with STO1 and therefore accounted for in the TBL evaluation.

Backflow events may provide another human pathogen exposure pathway as they involve the introduction of water from uncontrolled sources into the main water supply. Backflow events occur when the pressure in the water supply system drops and water from external sources, such as a hose bib, is allowed to flow back into the main water supply system. System pressure drops typically occur due to infrastructure failure (e.g., pipeline breaks) or overuse (e.g., unusually high water demands).

The risk of a backflow event due to infrastructure failure is comparable for STO1 and STO2 as both options would use the existing water distribution system infrastructure. The risk of a backflow event due to overuse is slightly higher for STO2 than that of STO1 as there is no way to cap the amount of water that is used for irrigation under the combined system. If the irrigation demand spikes beyond the total water allotment (i.e., 900gpm/connection) overuse of the system could occur. It is possible, but unlikely that the potable system under STO2 would experience demand spikes resulting in system pressure losses and backflows. The pathogen exposure risk due to backflows can be reduced to comparable levels for STO1 and STO2 through the installation of backflow prevention devices all connections to the main water supply system. 49

STO2 is preferable to STO1 in regards to potential for public health risk due to untreated irrigation water and receives 1 point for this criterion.

5.5.2 Quality of Life

The physical configuration of the two options differ in ways that could affect quality of life for community residents. STO1 requires the installation of irrigation water distribution pipelines throughout each community with daily limits on the total amount of water that would be available from this system each day. These features could adversely affect resident daily life, especially during system installation.

The options also differ in terms of the flexibility that households would have in using the 900 gallons per household per day provided by each option. With a combined system it would be easier for the household to allocate water use between indoor uses and irrigation as needed. Because all of the delivered water would be potable, it would be totally fungible and the household could use it for any purpose, both indoors and for irrigation. If, for example, a household desired to allocate less water to lawn irrigation and more to laundry and showering activities they could do so. For some households, especially with larger families, this flexibility would be welcomed. In contrast, STO1 is designed to deliver only 400 gallons per day of potable water to the household and none of the irrigation water would be available to supplement indoor water use demands. In short, STO2 would allow the homeowner greater flexibility to allocate water in a manner that best suits the individual household’s needs.

Hence, regarding quality of life, STO2 is preferable to STO1 and receives 1 point for this criterion.

5.6 Summary of Triple Bottom Line Analysis of the Water Supply and Treatment Options

Under the Triple Bottom Line analysis, STO2 (combined treatment for all uses) is recommended over STO1 (combined treatment with separate irrigation). A summary of the scoring is provided in Table 5.4. The total score of STO1 is 4 points and the total score of STO2 is 6 points out of am maximu possible score of 10 points. STO2 has the higher score because it is the preferred option when cost, public health, and quality of life are considered. STO1 is the preferred option when greenhouse gas emissions and aquifer sustainability are considered.

Table 5.4: Summary of Criteria Scoring for the Two Water Supply and Treatment Options

Criterion Scores STO1 ‐ Combined Criterion Type Criterion STO2 ‐ Combined Treatment, Treatment, All Uses Separate Irrigation Economic Lowest Capital Cost 0 4 Lower Greenhouse Gas Environmental Emissions 2 0 Greater Aquifer Environmental Sustainability 2 0 Better Protection of Public Social Health 0 1 Social Better Quality of Life 0 1

Total Score (out of a possible 10 points) 4 6

The most significant difference between the two options is cost. The capital cost of STO1 is estimated to be $4.2 million to $6.4 million greater than the capital cost of STO2. Regardless of which option is selected, the installed option would result in minor environmental and social impacts. STO1 appears to confer minor advantages over STO2 in regards to the environmental criteria, while STO2 is marginally preferable to STO1 based on the social criteria.

Under the greenhouse gas emission criteria, STO1 is expected to generate about 19,000 kg per year less of carbon dioxide equivalent when compared to STO2. However, this amount would save only $683 per year in climate change damages. Under the aquifer sustainability criteria, STO1 could result in lower total groundwater pumpage than STO2 but the difference in pumpage between the two options resulting from the cap on daily irrigation water supply is not known.

Under the public health criterion, the potential incidence of illness from contact with contaminated irrigation water under STO1 and STO2 is expected to be small but comparable. Under the quality of life criterion, households might experience greater inconvenience during the installation phase of STO1, but the extent and duration of the anticipated disruptions are minor when put in the context of a system that would operate for many decades.

5.7 Treatment Option Recommendation

Of the two long term supply and treatment options considered for implementation at Selma Estates and Raspberry Falls, Hazen and Sawyer recommends that Loudoun Water consider proceeding with STO2 for the reasons explained below.

This page intentionally left blank. List of Appendices Appendix A: Calculations Appendix B: Cost Estimates

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APPENDIX A: Calculations

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Last Updated: 11.6.14 Design Info

Flow (consumer demand flow only)

Flow per # of Connectio Option connectio Total Flow (gal/day) n ns (gal/day) 1 - 1 membrane plant to serve Selma and Raspberry; separate irrigation system 400 491 196,400 2 - 1 plant to serve Selma & Raspberry; irrigation water included in membr. treatment 900 491 441,900

Flux Rate from to DESIGN Average 35 40 gal/ft^2/day (gfd) DESIGN Peak 50 gal/ft^2/day (gfd)

Temperature Average 20 oC Min 8.6 oC

Viscosity Viscosity of water at average - 20oC 1 CP Viscosity of water at min - 8.6oC 1.366 CP

Membrane Operating Time Membrane operating time =filtering time + maintenance time Membrane filtering time is the time that the membrane is producing useable water Membrane maintenance time is the time that the membrane is being cleaned

20 min. Membrane Operating time Filtering time 17 min Maintenance Cycle Air scrub duration 1 min Forward Flush 2 min Backwash 1.5 min total 4.5 min

Total minutes in a day 1,440 Minutes on Maintenance per cycle 4.5 Membrane cycles/day 67 Total Maintenance Time 301.40 Membrane integrity test (min/day) 5.00 Total Filtering Time 1,134 min (A)

A. Temperature Corrected Flux Temperature Adjusted Flux = (Viscosity of water at average,20oC/Viscosity of water at min,8.6oC) x normalized flux

Flux Rate from to DESIGN Average 25.62 29.28 gfd DESIGN Max 36.60 gfd

B. Adjusted Flow Rate Adjusted flow to include the consumer demand flow and the flow needed for membrane cleaning

Membrane Area Required (sf) = System Flow Rate (Q, gpd) /Actual Flux (gfd)

Two methods to estimate adjusted (i.e. total system) flow rate and resulting membrane area Method 1 - based on recovery rate Method 2 - based on filtering time Use the larger of the two to be conservative

Method 1 - Recovery rate Assume a 90% recovery rate. Manufacturer's claim 92-96%, assume 90% to be conservative.

Flow/recovery rate= system flow Option 1 Option 2 Flow (consumer demand) 196,400 441,900 gal/day Recovery rate 0.9 0.9 Adjusted System flow 218,222 491,000 gal/day (B1) Method 2 - Backwash Water Option 1 Option 2 Backwash water per cycle 188 377 gallons 188 gal/1.5 min every 35 min OR 377 gal/1.5 min every 35 min Cycles per day 67 67 **Backwash occur every 35 but membrane cycle time is 20 min, use 20 min Total backwash water per day 12,592 25,250 gal/day

Adjusted System flow Option 1 Option 2 Flow (consumer demand) 196,400 441,900 gal/day Backwash Flow 12,592 25,250 gal/day Adjusted System flow 208,992 467,150 gal/day (B2)

Flow by Method summary Option 1 Option 2 Method 1 218,222 491,000 gal/day Method 2 208,992 467,150 gal/day

Method Selection Method 1 Method 1 choose method that produces highest flows

C. Membrane Area Required

Option 1 Option 2 Method 1: Membrane System Feed flow (B1/A) 192.5 433.1 gpm/day 277,204 623,710 gpd

Method 2: Membrane System Feed flow (B2/A) 184.4 412.1 gpm/day 265,479 593,414 gpd

Membrane area = total flow/temp. corrected flux

Option 1 Option 2 Method 1 membrane area 10,819 24,342 sf Method 2 membrane area 10,361 23,160 sf Waste Load from Cleaning Processes

Option 1 Option 2 MC CIP MC CIP

Citric Acid Rinse Citric Acid Rinse Citric Acid Conc. = 2,000 mg/L 20,000 mg/L 2,000 mg/L 20,000 mg/L Duration =0.2 hr 1.0 hr 0.2 hr 1.0 hr Rate =1.07 gpm/mod 1.07 gpm/mod 1.07 gpm/mod 1.07 gpm/mod Total Flow =21 gpm 21 gpm 43 gpm 43 gpm Total Vol. =213 gal 1,280 gal 427 gal 2,560 gal 50% Citric Acid density =1.24 g/mL 1.24 g/mL 1.24 g/mL 1.24 g/mL Citric Acid Vol. @ 50% =0.7 gal/MC 41.3 gal/CIP 1.4 gal/MC 82.6 gal/CIP Annual Volume =8.3 gal 495.5 gal 33.0 gal 991.0 gal Maximum Waste Load (lbs) =0.7 lbs 44.0 lbs 1.5 lbs 88.0 lbs Consumption during Cleaning = 30% 30% 30% 30% Expected Waste Load (lbs) =0.5 lbs 30.8 lbs 1.0 lbs 61.6 lbs

Sodium Hypochlorite Sodium Hypochlorite NaClO Conc. =100 mg/L as CL2 500 mg/L as CL2 100 mg/L as CL2 500 mg/L as CL2 Duration =0.2 hr 1.0 hr 0.2 hr 1.0 hr Rate =1.07 gpm/mod 1.07 gpm/mod 1.07 gpm/mod 1.07 gpm/mod Total Flow =21 gpm 21 gpm 43 gpm 43 gpm Total Vol. =213 gal 1,280 gal 427 gal 2,560 gal 12.5% NaClO density =1.21 g/mL 1.21 g/mL 1.21 g/mL 1.21 g/mL Vol. 12.5% NaClO =0.1 gal/MC 4.4 gal/CIP 0.3 gal/MC 8.9 gal/CIP Annual Volume =3.5 gal 53.2 gal 7.1 gal 106.5 gal Maximum Waste Load (lbs) =0.2 lbs 4.6 lbs 0.3 lbs 9.2 lbs Consumption during Cleaning = 85% 85% 85% 85% Expected Waste Load (lbs) =0.0 lbs 0.7 lbs 0.0 lbs 1.4 lbs

Sodium Hydroxide Sodium Hydroxide NaOH Conc. = ‐ 500 mg/L ‐ 500 mg/L Duration = ‐ 1.0 hr ‐ 1.0 hr Rate = ‐ 1.07 gpm/mod ‐ 1.07 gpm/mod Total Flow = ‐ 21 gpm ‐ 43 gpm Total Vol. = ‐ 1,280 gal ‐ 2,560 gal 12.5% NaOH Vol. = ‐ 33.5 gal/CIP ‐ 66.9 gal/CIP Annual Volume = ‐ 401.6 gal ‐ 803.1 gal Waste Load (lbs) = ‐ 11.0 lbs ‐ 22.0 lbs Consumption during Cleaning = ‐ 0% ‐ 0% Expected Waste Load (lbs) = ‐ 11.0 lbs ‐ 22.0 lbs

Dechlorination Dechlorination Chlorine Consumption = 85% 85% 85% 85% Expected Chlorine Residual =15 mg/L as CL2 75 mg/L as CL2 15 mg/L as CL2 75 mg/L as CL2 Sodium Bisulfite req'd =1.34 lbs/100kgal/1mg/L 1.34 lbs/100kgal/1mg/L 1.34 lbs/100kgal/1mg/L 1.34 lbs/100kgal/1mg/L Sodium Bisulfite =0.0 lbs 1.3 lbs 0.1 lbs 2.6 lbs 40% Solution Density =11.0 lbs/gal 11.0 lbs/gal 11.0 lbs/gal 11.0 lbs/gal 40% Solution Req'd =0.0 gal/CIP 0.3 gal/CIP 0.0 gal/CIP 0.6 gal/CIP Annual Volume =0.2 gal 3.5 gal 0.5 gal 7.0 gal

Expected Waste Volumes Expected Waste Volumes Chemical Waste Volume =427 gal 2,560 gal 853 gal 5,120 gal Flush Water Volume =853 gal 5,120 gal 1,707 gal 10,240 gal Total Waste Volume =1,280 gal 7,680 gal 2,560 gal 15,360 gal

pH of Waste from Maintenance Cleaning (Options 1&2)

Input:

Output:

Notes: 1. pH of the waste stream was calculated using the software “Visual MINTEQ”. 2. The waste is expected to be mixed in the equalization basin. 3. Chemicals consumptions during cleaning procedure is not incorporated to the calculations.

pH of Waste from Clean‐in‐Place (Options 1&2)

Input:

Output:

Pump Data Sheet - Patterson 60 Hz Pumps

Company: Raspberry Irr 2 Hr Duplex Rev2 Name: Date: 11/19/2014

Pump: Search Criteria: Size: 2.5x2x8A HES Flow: 212 US gpm Head: 227 ft Type: EndSuction Speed: 3500 rpm Fluid: Synch speed: 3600 rpm Dia: 7.75 in Water Temperature: 60 °F Curve: A05-82851-6 Impeller: C05-83412 SG: 1 Vapor pressure: 0.2563 psi a Specific Speeds: Ns: --- Viscosity: 1.105 cP Atm pressure: 14.7 psi a Nss: --- NPSHa: --- Dimensions: Suction: --- Discharge: --- Motor: Standard: NEMA Size: 25 hp Pump Limits: Enclosure: TEFC Speed: 3600 Temperature: --- Power: --- Frame: 284TS Pressure: --- Eye area: --- Sizing criteria: Max Power on Design Curve Sphere size: 0.4375 in

8 in 55 60 ---- Data Point ---- 65 70 Flow: 212 US gpm 250 7.75 in Head: 233 ft 73.8 Eff: 70.5% 70 Power: 17.6 hp 200 65 NPSHr: 11.7 ft

---- Design Curve ---- 150 6 in 60 Shutoff head: 247 ft 55

Shutoff dP: 107 psi Head - ft 60 Min flow: --- 100

BEP: 73.8% @ 269 US gpm 60 NOL power: 24.1 hp @ 400 US gpm 50

-- Max Curve --

Max power: 0 50 100 150 200 250 300 350 400 27.7 hp @ 400 US gpm 60

20 NPSHr - ft 0 50 100 150 200 250 300 350 400 30

Power - hp 50 100 150 200 250 300 350 400 US gpm In accordance with the Hydraulic Institute Standards, pump is guaranteed for one set of conditions. Performance guarantees are based on shop test and when handling clear, cold, fresh water at sea level and at a temperature no greater than 85 degrees F. Suction lift must not exceed that shown on curve. Performance Evaluation: Flow Speed Head Efficiency Power NPSHr US gpm rpm ft % hp ft 254 3500 222 72.9 19.5 16.5 212 3500 233 70.5 17.6 11.7 170 3500 241 64.9 15.9 7.68 127 3500 244 54.4 14.4 5.71 84.8 3500 ------

Selected from catalog: Patterson Pumps.60 Vers: 1.4 Pump Data Sheet - Patterson 60 Hz Pumps

Company: Selma Irr 2 Hr Duplex Rev 2 Name: Date: 11/19/2014

Pump: Search Criteria: Size: 2.5x2x9.5 Flow: 289 US gpm Head: 323 ft Type: EndSuction-CC Speed: 3560 rpm Fluid: Synch speed: 3600 rpm Dia: 8.875 in Water Temperature: 60 °F Curve: E2DA9A-CC Impeller: D05-87193 SG: 1 Vapor pressure: 0.2563 psi a Specific Speeds: Ns: 929 Viscosity: 1.105 cP Atm pressure: 14.7 psi a Nss: 4625 NPSHa: --- Dimensions: Suction: 2.5 in Discharge: 2 in Motor: Standard: NEMA Size: 60 hp Pump Limits: Enclosure: TEFC Speed: 3600 Temperature: --- Power: --- Frame: 364TS Pressure: --- Eye area: --- Sizing criteria: Max Power on Design Curve Sphere size: ---

---- Data Point ---- Flow: 289 US gpm 400 9.5 in 50 60 Head: 323 ft 65 70 Eff: 68.3% 8.875 in

Power: 34.4 hp 72.1 70 NPSHr: 16.2 ft 300 65 ---- Design Curve ---- 60

Shutoff head: 343 ft 6.75 in 50

Head - ft 200 Shutoff dP: 149 psi 50 60 65 Min flow: 97.5 US gpm BEP: 72.1% @ 390 US gpm 65 60 100 NOL power: 50 50.5 hp @ 619 US gpm

-- Max Curve -- 0 Max power: 100 200 300 400 500 600 700 62.1 hp @ 656 US gpm 75

NPSHr - ft 0 100 200 300 400 500 600 700 75

0 100 200 300 400 500 600 700 Power - hp US gpm Refer to Working Pressure vs. Temperature chart for maximum rated working pressure. All data are subject to change. Consult factory for certified data. In accordance with the Hydraulic Institute Standards, pump is guaranteed for one set of conditions. Performance guarantees are based on shop test and when handling clear, cold, fresh water at sea level and at a temperature no greater than 85 degrees F. Suction lift must not exceed that shown on curve.

Performance Evaluation: Flow Speed Head Efficiency Power NPSHr US gpm rpm ft % hp ft 347 3560 311 70.9 38.2 20.5 289 3560 323 68.3 34.4 16.2 231 3560 331 63.1 30.5 14.7 173 3560 336 52.9 27.6 15.7 116 3560 339 41.5 25.1 17.6

Selected from catalog: Patterson Pumps.60 Vers: 1.4 Pump Data Sheet - Patterson 60 Hz Pumps

Company: Selma 400 GPD PW Only Rev 2 Name: Date: 11/11/2014

Pump: Search Criteria: Size: 5x3 Flow: 850 US gpm Head: 238 ft Type: InLinePumps Speed: 3560 rpm Fluid: Synch speed: 3600 rpm Dia: 8.6875 in Water Temperature: 60 °F Curve: 53IP-A Impeller: D-5675 SG: 1 Vapor pressure: 0.2563 psi a Specific Speeds: Ns: 1484 Viscosity: 1.105 cP Atm pressure: 14.7 psi a Nss: --- NPSHa: --- Dimensions: Suction: 5 in Discharge: 3 in Motor: Consult Patterson 60 Hz Pumps to select a motor for this pump. Pump Limits: Temperature: 200 °F Power: --- Pressure: 225 psi g Eye area: --- Sphere size: 0.5625 in

---- Data Point ---- 8.75 in Flow: 850 US gpm 8.6875 in 60 65 70 75 77 Head: 238 ft 80 300 83 Eff: 82.9% 83.1 Power: 61.7 hp 83 NPSHr: 20.9 ft 80 77 ---- Design Curve ---- 200 75 Shutoff head: 327 ft 70

Shutoff dP: 142 psi Head - ft 5.5 in Min flow: 185 US gpm 65 BEP: 83.1% @ 742 US gpm 60 100 60 NOL power: 66 hp @ 1109 US gpm 60

-- Max Curve --

Max power: 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 68.1 hp @ 1119 US gpm 40

20 NPSHr - ft 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 75

Power - hp 100 200 300 400 500 600 700 800 900 1000 1100 1200 US gpm In accordance with the Hydraulic Institute Standards, pump is guaranteed for one set of conditions. Performance guarantees are based on shop test and when handling clear, cold, fresh water at sea level and at a temperature no greater than 85 degrees F. Suction lift must not exceed that shown on curve. Performance Evaluation: Flow Speed Head Efficiency Power NPSHr US gpm rpm ft % hp ft 1020 3560 187 75 64.2 29.3 850 3560 238 82.9 61.7 20.9 680 3560 275 83 56.8 15.3 510 3560 303 76.1 51.2 11.7 340 3560 319 63.2 43.3 10.2

Selected from catalog: Patterson Pumps.60 Vers: 1.4 Pump Data Sheet - Patterson 60 Hz Pumps

Company: Selma 400 GPD PW Only Rev1 Name: Date: 11/11/2014

Pump: Search Criteria: Size: 4x3 Flow: 425 US gpm Head: 238 ft Type: InLinePumps Speed: 3520 rpm Fluid: Synch speed: 3600 rpm Dia: 7.875 in Water Temperature: 60 °F Curve: 43IP-A Impeller: D-5656 SG: 1 Vapor pressure: 0.2563 psi a Specific Speeds: Ns: 1285 Viscosity: 1.105 cP Atm pressure: 14.7 psi a Nss: --- NPSHa: --- Dimensions: Suction: 4 in Discharge: 3 in Motor: Consult Patterson 60 Hz Pumps to select a motor for this pump. Pump Limits: Temperature: 200 °F Power: --- Pressure: 225 psi g Eye area: --- Sphere size: 0.4375 in

---- Data Point ---- Flow: 425 US gpm 8.5 in 60 70 Head: 238 ft 75 300 80 7.875 in 82 Eff: 82.7% 83 Power: 30.8 hp 83 NPSHr: 12.6 ft 83.1 82 80 75 ---- Design Curve ---- 200 Shutoff head: 280 ft

Shutoff dP: 121 psi Head - ft 70 Min flow: 121 US gpm 5.5 in BEP: 83.1% @ 485 US gpm 60 100 70 75 NOL power: 75 35.8 hp @ 641 US gpm 70

-- Max Curve --

Max power: 0 100 200 300 400 500 600 700 46.1 hp @ 700 US gpm 30

10 NPSHr - ft 0 100 200 300 400 500 600 700 50

Power - hp 100 200 300 400 500 600 700 US gpm In accordance with the Hydraulic Institute Standards, pump is guaranteed for one set of conditions. Performance guarantees are based on shop test and when handling clear, cold, fresh water at sea level and at a temperature no greater than 85 degrees F. Suction lift must not exceed that shown on curve. Performance Evaluation: Flow Speed Head Efficiency Power NPSHr US gpm rpm ft % hp ft 510 3520 213 83.1 32.9 14.9 425 3520 238 82.7 30.8 12.6 340 3520 255 77.9 28 11.2 255 3520 268 70.2 24.6 10.4 170 3520 275 57.3 20.9 10.2

Selected from catalog: Patterson Pumps.60 Vers: 1.4

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APPENDIX B: Cost Estimates

This page intentionally left blank. Loudoun Water Raspberry Falls Water Supply and Treatment Evaluation Project Cost Summary

Estimated Capital Cost of STO 1 - 400 gpd/ERC from Water Treatment Plant with Two New Wells for Irrigation

Item Quantity Unit Material Unit Cost Labor Unit Cost Equipment Unit Cost Total Cost SOURCE OF SUPPLY New Wells (incl. testing and permitting costs) 2 EA$ 150,000 $ 300,000 Raw Water Pipelines 500 LF$ 72 $ 36,000 Valves and appurtenances for well pumps 1 LS$ 30,000 $ 30,000 Electrical service 2 LS$ 50,000 $ 100,000 SUBTOTAL $ 466,000 POTABLE WATER TREATMENT AND DISTRIBUTION Site Preparation Costs Sediment and erosion control 1 LS $ 3,500 $ 3,500 Clearing and grubbing 0.14 AC $ 5,000 $ 10,000 $ 10,709 Site demolition 1 LS $ 18,000 $ 18,000 Excavation 178 CY $ 15 $ 2,667 Select backfill 89 CY $ 20 $ 1,778 Final seeding / landscaping (incl. buffer areas) 1 LS $ 10,000 $ 10,000 New driveway 100 SY $ 65 $ 6,500 Pavement restoration 210 SY $ 100 $ 21,000 Curbs 60 LF $ 10 $ 600 Yard Piping Finished water piping 130 LF $ 72 $ 9,360 Drain piping 35 LF $ 120 $ 4,200 Membrane Treatment Building Concrete foundation 89 CY $ 350 $ 31,111 Building 1200 SF $ 250 $ 300,000 Chemical containment area coatings 160 SF $ 3 $ 400 FRP grating for containment area 20 SF $ 50 $ 1,000 HVAC 1 LS $ 35,000 $ 35,000 Fire Protection 1 LS $ 15,000 $ 15,000 Process Mechanical Equipment Demolition of existing process equipment 1 LS $ 25,000 $ 25,000 New membrane treatment skids 1 EA $ 900,000 $ 150,000 $ 10,000 $ 1,060,000 Break tank 1 EA $ 1,000 $ 5,000 $ 10,000 $ 16,000 Neutralization tank Excavation 240 CY $ 15 $ 3,600 Select backfill 80 CY $ 20 $ 1,600 Base slab 20 CY $ 350 $ 6,844 Walls 25 CY $ 450 $ 11,333 Elevated slab 20 CY $ 650 $ 12,711 Chemical metering pumps and tanks 1 LS $ 10,000 $ 10,000 Interior process mechanical piping 1 LS $ 15,000 $ 15,000 Chemical piping 1 LS $ 7,500 $ 7,500 Miscellaneous valves 1 LS $ 15,000 $ 15,000 Miscellaneous pipe supports 1 LS $ 5,000 $ 5,000 New Electrical Service 1 LS $ 100,000 $ 100,000 Interior Power and Lighting 1 LS $ 508,231 $ 508,231 Instrumentation and Controls 1 LS $ 290,418 $ 290,418 Finished Water Storage Tank Modifications 1 EA $ 256,000 $ 256,000 New FW Peak Usage Booster Pumps 3 EA $ 8,000 $ 2,200 $ 10,000 $ 60,600 New FW Jockey Pumps 2 EA $ 7,000 $ 2,000 $ 18,000 Allowance for PRV Vaults/PRV Modifications 1 LS $ 150,000 $ 150,000 SUBTOTAL $ 3,043,662

400-E O:\32256-FFX\32256-025\Eng\Cost Estimates\Selma and Raspberry Cost Estimates_FINAL Financial Model 12_22_2014.xlsx 1/6/2015 Loudoun Water Raspberry Falls Water Supply and Treatment Evaluation Project Cost Summary

NON-POTABLE DISTRIBUTION SYSTEM Raspberry Falls System 1 EA 172,000 Storage tank (installed cost quote )2 EA 20,000 $ 172,000.00 Booster pumps 5000 $ 10,000 $ 70,000.00 Distribution piping 24,356 LF 40 3-inch PVC piping 5,584 LF 48 $ 974,240 4-inch PVC piping 2,978 LF 72 $ 268,032 6-inch PVC piping - LF 96 $ 214,416 8-inch PVC piping - LF 120 $ - 10-inch PVC piping - LF 86 $ - 12-inch PVC piping 203 EA 40 $ - Meter / valve boxes 203 EA 200 40 $ 16,240.00 Meters 203 EA 20 80 $ 56,840.00 Isolation valves 1 LS 20,000 20 $ 8,120.00 Service connection piping $ 20,000.00 SUBTOTAL $ 1,799,888 Selma Estates System 1 EA 206,000 Storage tank (installed cost quote )2 EA 20,000 $ 206,000 Booster pumps 5000 $ 10,000 $ 70,000 Distribution piping 33,236 LF 40 3-inch PVC piping 7,712 LF 48 $ 1,329,440 4-inch PVC piping 4,113 LF 72 $ 370,176 6-inch PVC piping - LF 96 $ 296,136 8-inch PVC piping - LF 120 $ - 10-inch PVC piping - LF 86 $ - 12-inch PVC piping $ - Meter / valve boxes 277 EA 40 40 $ 22,160 Meters 277 EA 200 80 $ 77,560 Isolation valves 277 EA 20 20 $ 11,080 Service connection piping 1 LS 28000 $ 28,000 SUBTOTAL $ 2,410,552 SUBTOTAL $ 4,210,440 CAPITAL COST ESTIMATE SUMMARY Subotal $ 7,720,102 General Conditions (7%) $ 540,407 Contractor OH&P (21%) $ 1,621,221 Subtotal $ 9,881,731 Minus Contingency (15%) $ (1,482,260) Plus Contingency (30%) $ 2,964,519 TOTAL CONSTRUCTION COST RANGE $ 8,399,471 TO $ 12,846,250

TOTAL CAPITAL COST RANGE (15% markup for engineering design and construction management) $ 9,659,392 $ 14,773,187 Notes: 1. Based on Siemens Memcor CPII 10L40N. 2 units total: 1 duty, 1 spare. 2. Treatment building unit cost of $250 per square foot based on brick and block building. It was also assumed that the base slab for the treatment building is two feet thick. 3. It was assumed that an excavation depth of 4 feet would be required with 2 feet allowed for backfill/stone. Pavement includes labor, base, binder, and surface course - heavy duty for treatment plant.

Estimated Capital Cost of STO 2 - 900 gpd/ERC from New Water Treatment Plant with Two Wells for Potable Water Supply

Item Quantity Unit Material Unit Cost Labor Unit Cost Equipment Unit Cost Total Cost SOURCE OF SUPPLY Testing of PW-1 and PW-2 to Confirm Yield 1 LS $ 75,000 Raw Water Pipelines 16700 LF $ 72 $ 1,202,400 SUBTOTAL $ 1,277,400 POTABLE WATER TREATMENT AND DISTRIBUTION Site Preparation Costs Sediment and erosion control 1 LS $ 3,500 $ 3,500 Clearing and grubbing 0.14 AC $ 5,000 $ 10,000 $ 10,709 Site demolition 1 LS $ 18,000 $ 18,000 Excavation 207 CY $ 15 $ 3,111 Select backfill 104 CY $ 20 $ 2,074 Final seeding / landscaping (incl. buffer areas) 1 LS $ 10,000 $ 10,000 New driveway 100 SY $ 65 $ 6,500 Pavement restoration 210 SY $ 100 $ 21,000 Curbs 60 LF $ 10 $ 600 Yard Piping Finished water piping 130 LF $ 72 $ 9,360 Drain piping 35 LF $ 120 $ 4,200 Membrane Treatment Building Concrete foundation 104 CY $ 350 $ 36,296 Building 1400 SF $ 250 $ 350,000 Chemical containment area coatings 160 SF $ 3 $ 400 FRP grating for containment area 20 SF $ 50 $ 1,000 HVAC 1 LS $ 35,000 $ 35,000 Fire Protection 1 LS $ 15,000 $ 15,000 Process Mechanical Equipment Demolition of existing process equipment 1 LS $ 25,000 $ 25,000 New membrane treatment skids 1 EA $ 950,000 $ 150,000 $ 10,000 $ 1,110,000 Break tank 1 EA $ 15,000 $ 5,000 $ 10,000 $ 30,000 Neutralization tank Excavation 240 CY $ 15 $ 3,600 Select backfill 80 CY $ 20 $ 1,600 Base slab 20 CY $ 350 $ 6,844 Walls 25 CY $ 450 $ 11,333 Elevated slab 20 CY $ 650 $ 12,711 Chemical metering pumps and tanks 1 LS $ 10,000 $ 10,000 Interior process mechanical piping 1 LS $ 15,000 $ 15,000 Chemical piping 1 LS $ 7,500 $ 7,500 Miscellaneous valves 1 LS $ 15,000 $ 15,000 Miscellaneous pipe supports 1 LS $ 5,000 $ 5,000 New Electrical Service 1 LS $ 100,000 $ 100,000 Interior Power and Lighting 1 LS $ 415,131 $ 415,131 Instrumentation and Controls 1 LS $ 237,218 $ 237,218 Finished Water Storage Tank Modifications 1 EA $ 381,000 $ 381,000 New FW Peak Usage Booster Pumps 3 EA $ 8,000 $ 2,200 $ 10,000 $ 60,600 New FW Jockey Pumps 2 EA $ 5,000 $ 1,500 $ 13,000 Allowance for PRV Vaults/PRV Modifications 1 LS $ 150,000 $ 150,000 SUBTOTAL $ 3,137,288 CAPITAL COST ESTIMATE SUMMARY Subotal $ 4,414,688 General Conditions (7%) $ 309,028 Contractor OH&P (21%) $ 927,084 Subtotal $ 5,650,801 Minus Contingency (15%) $ (847,620) Plus Contingency (30%) $ 1,695,240 TOTAL CONSTRUCTION COST RANGE $ 4,803,181 TO $ 7,346,041 TOTAL CAPITAL COST RANGE (15% markup for engineering design and construction management) $ 5,523,658 TO $ 8,447,947 Notes: 1. Based on Siemens Memcor CPII 20L40N. 2 units total: 1 duty, 1 spare. 2. Treatment building unit cost of $250 per square foot based on brick and block building. It was also assumed that the base slab for the treatment building is two feet thick. 3. It was assumed that an excavation depth of 4 feet would be required with 2 feet allowed for backfill/stone. Pavement includes labor, base, binder, and surface course - heavy duty for treatment plant.

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