CHAPTER 9 – Storage Infrastructure

Storage projects help meet the Drinking Water Utility’s Goal 6:

Goal

Infrastructure is prudently financed, and sustainably constructed, maintained and operated to ensure reliable delivery of high quality water to a growing community.

The 2015-2020 strategy is to develop and maintain storage and transmission/distribution infrastructure to ensure delivery of water at adequate pressure throughout the system and maintain required fire flow.

Other projects for improving the infrastructure are discussed in Chapter 8 (Source Infrastructure) and Chapter 10 (Transmission/Distribution Infrastructure); Chapter 12 describes operations and maintenance of the infrastructure. Water quality strategies are in Chapter 11.

This chapter describes existing water storage tanks, evaluates their ability to meet current and projected needs, and identifies projects to be constructed in 2015-2020. Washington State Department of Health (DOH) rules on storage facilities are in Chapter 173-160 WAC and Chapter 246-290 WAC, Part 3 (design of public water systems). Detailed specifications are in the DOH Design Manual.

9.1 Description of Existing Storage

The Utility’s system has 11 water storage tanks, with a total capacity of 30.97 million gallons. Table 9.1 is an inventory of these facilities, including capacities, elevations and dimensions. Locations are shown in Chapter 1, Map 1.4. Further details regarding the storage tanks serving each pressure zone are provided below in the analysis section.

9.2 Storage Capacity Analysis

This section reports the analysis of how well existing and planned storage facilities support current and future storage requirements. The design criteria upon which the analysis is based are first presented, followed by a discussion of the evaluation results.

Storage Volume Components

According to DOH requirements, water system storage volume is comprised of five separate components:

•    Operating storage

•    Equalizing storage

•    Fire flow storage

•    Standby storage

•    Dead storage

These components are illustrated in Figure 9.1.

View Figure 9.1 Storage Components.

Table 9.1 Storage Facilities Inventory

 

Meridian No. 1

Meridian No. 2

Fir 226 (north)

Fir 226 (south)

Hoffman 417

Boulevard 338

Eastside 347

Stevens Field 264

Bush 298

Elliott 298

Elliott 380

Zone Served

 

 

 

 

 

 

 

 

 

 

 

Zone Name

All Zones

All Zones

Zone 226

Zone 226

Zone 417

Zone 338

Zone 347

Zone 264

Zone 298

Zone 298

Zone 380

Elevation Range

N/A

N/A

0 – 139 ft

0 – 139 ft

150 – 276 ft

110 – 205 ft

110 – 204 ft

16 – 165ft

0 – 230 ft

0 – 230 ft

0 – 280 ft

Capacity (mg)

 

 

 

 

 

 

 

 

 

 

 

Total

4.0

4.00

2.50

2.50

3.69

2.44

3.43

0.60

1.05

2.00

4.76

Elevations (ft)

 

 

 

 

 

 

 

 

 

 

 

Tank Overflow

301

299

226

226

417

338

347

264

298

298

380

Tank Floor

281

281

206

206

277

238

214

160

258

278

280

Dimensions (ft)

 

 

 

 

 

 

 

 

 

 

 

Engineering Plans

Variable

Variable

Variable

Variable

67-ft Diam.

66-ft Diam.

67-ft Diam.

32

67-ft Diam.

130-ft Diam.

90-ft Diam.

Water Depth

20

20

20

20

140

95.5

130

104

40

20

100

Construction

 

 

 

 

 

 

 

 

 

 

 

Year Constructed

2004

1998

~1935

~1935

1980

2001

1987

2007

2007

1975

1994

Type

Ground level

Ground level

Buried

Buried

Standpipe

Standpipe

Standpipe

Standpipe

Standpipe

Buried

Standpipe

Material

Concrete

Concrete

Concrete

Concrete

Steel

Steel

Steel

Steel

Steel

Concrete

Steel

Security

 

 

 

 

 

 

 

 

 

 

 

Enclosed/covered?

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Fenced & locked?

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Operating and Dead Storage

Operating storage is the water that lies between low and high water storage elevations set by City operations staff to control system pumps and flow control valves. Dead volume is the volume at the bottom of the tank that cannot be used because it is physically too low to provide sufficient pressures. Operational and dead storage volumes are subtracted from total storage to determine the effective storage available for equalizing, standby and fire flow.

Equalizing Storage

Equalizing storage is the total volume needed to moderate fluctuations in diurnal demands during periods when the demand exceeds the capacity of the supply system. Equalizing storage requirements are greatest during the peak hours of the maximum day demand. Operation of a properly balanced system results in replenishment of storage facilities during times of day when the demand curve is below the capacity of the supply system, and results in withdrawal from storage facilities when the demand exceeds the supply capacity. The equalizing storage of a storage tank must be located at an elevation that provides a minimum pressure of 30 pounds per square inch (psi) to all customers served by the tank.

Fire Flow Storage

Fire flow is defined as either 1,000 gpm for two hours or 4,000 gpm for four hours, depending on the demographics of the zone. The Olympia Fire Department establishes the fire flow needed for each zone. DOH allows for the “nesting” of standby and fire flow storage, with the larger used for the storage volume. However, the Olympia Fire Department requires that both standby and fire flow volumes be provided.

The required fire flow storage for a given pressure zone is calculated as the required fire flow multiplied by the required duration. The fire flow storage required for Zones 417, 338, 226, 264 and 298 is 960,000 gallons, based on a flow rate of 4,000 gpm for a duration of four hours. The fire flow storage required for Zones 347 and 380 is 120,000 gallons, based on a flow rate of 1,000 gpm for a duration of two hours.

The fire flow storage of a tank must be located at an elevation that provides a minimum pressure of 20 psi to all customers served by the tank.

Standby Storage

Standby storage is required to supply reasonable system demands during a foreseeable system emergency or outage. A key concept is that establishing standby storage involves planning for reasonable system outages – those that can be expected to occur under normal operating conditions, such as a pipeline failure, power outage or valve failure. Major system emergencies, such as those created by an earthquake, are intended to be covered by emergency system operations planning, since construction of sufficient reserve volume to accommodate sustained system demands under emergency conditions is not economically feasible.

DOH has established guidelines for determining minimum required standby storage. This component is calculated as the greater of: two times the average day demand, less multi-source credit; or 200 gallons times the number of ERUs served by the storage facility.

The multi-source credit allows the required standby storage to be reduced in pressure zones that have multiple sources of supply. The credit assumes the largest source of supply is out of service. It is calculated as the total source available to a particular pressure zone, or zone combination, less the capacity of the largest source. No credit is allowed for zones having only one source of supply.

DOH recommends that standby storage be located at an elevation that provides a minimum pressure of 20 psi to all customers served by a tank, similar to the fire flow volume requirement.

Evaluation of Storage Capacity

To meet City design standards, storage facilities must be designed so the sum of the required storage for each of the five components is met for the pressure zone(s) that will be served. Detailed results of the storage capacity analysis for each pressure zone are provided below. The minimum required storage for each pressure zone is calculated by adding the five storage components.

In addition to the storage tanks that directly serve the City’s pressure zones, as described in the following subsections, the Meridian Storage Tanks provide supplemental standby storage. However, due to the long 36-inch diameter transmission main that links these storage tanks to the distribution system, the City has elected to focus its standby storage capacity analysis on those storage facilities that directly hydraulically feed a pressure zone and/or are in close proximity to the geographic area covered by the zone.

Map 1.1 in Chapter 1 shows the location of the pressure zones and major drinking water system facilities.

Zones 417 and 338

The storage capacities for Zones 417 and 338 are first analyzed together, since the Hoffman Storage Tank provides storage capacity for both zones. The Boulevard Storage Tank provides additional storage for Zone 338. As a combined system, there is sufficient storage through 2034, as shown in Table 9.2.

Zone 417 must also be analyzed independently, as only the Hoffman Storage Tank provides capacity for this zone. Table 9.3 summarizes the analysis for Zone 417. Currently, with only the Hoffman Storage Tank providing gravity storage to this zone, there is a deficiency of approximately 1.27 million gallons (Mg). To resolve this deficiency, the Utility plans to construct the Log Cabin Storage Tank and have it online in 2016. A new tank with a 90-foot diameter and the same height of the Hoffman Tank (417 feet) would contain approximately 4.5 Mg of storage providing a minimum of 20 psi to all customers within the zone. As a result, storage in this zone would be sufficient through the remainder of the 20-year planning horizon. The gross volume of the new Log Cabin Tank will be about 6.68 MG, including tank wall height that will extend above the overflow elevation.

Zone 347

Storage capacity is provided to Zone 347 by the Eastside Storage Tank. This storage facility provides sufficient capacity throughout the planning period, as shown in Table 9.4.

Zone 264

Zone 264 is primarily supplied by a 10-inch water main, which receives water from the Meridian Storage Tanks. Additional supply is provided by the Capitol Way pressure reducing valve (PRV) that transfers water from Zone 338 and the Boulevard Storage Tank. Additional storage capacity is provided by the Stevens Field Storage Tank, which was constructed in 2007.

As shown in Table 9.5, the total storage capacity is sufficient to meet storage requirements throughout the planning period. The Meridian Storage Tanks and Stevens Field Storage Tank provide storage capacity for operational and equalization purposes. Hydraulic analyses indicate that fire flow storage is utilized equally from the three storage facilities available to the zone: Meridian, Stevens Field, and Boulevard Storage Tanks.

Zone 226, 298 and 380

The storage capacities for Zones 226, 298, and 380 are first analyzed together, due to the interconnectedness of these zones. The Percival Booster Pump Station can supply storage demands from the Fir Street Storage Tanks to Zones 298 and 380 because it is equipped with on-site power. PRVs allow water to be supplied from the Elliott 380 Storage Tank to Zones 298 and 226. The Elliott 298 and Bush Storage Tanks provide additional storage for Zone 298 and through a PRV to Zone 226. As a combined system, there is sufficient storage through 2034, as shown in Table 9.6.

Zone 380 must also be analyzed independently, since only the Elliott 380 Storage Tank provides storage capacity for this zone. Table 9.7 summarizes the analysis for Zone 380, indicating sufficient storage capacity throughout the planning period.

9.3 2015-2020 Storage Infrastructure Projects

The storage projects planned for 2015-2020 will help meet the Drinking Water Utility’s Goal 6:

Goal 6

Infrastructure is prudently financed, and sustainably constructed, maintained and operated to ensure reliable delivery of high quality water to a growing community.

Objective 6.A Design and construct infrastructure to ensure reliable delivery of water.

Storage projects will implement Strategy 6.A.2: Develop and maintain storage and transmission/distribution infrastructure to ensure delivery of water at adequate pressure throughout the system and maintain required fire flow. Chapters 8 and 10 describe source and transmission/distribution infrastructure; Chapter 12 describes operations and maintenance of the infrastructure. Water quality strategies are in Chapter 11.

Based on the analysis in the previous section, the City’s Capital Improvement Program for 2015-2020 includes the following storage projects. Project-level cost estimates and implementation schedule are in Chapter 13, Table 13.2.

•    New Log Cabin Storage Tank construction, south of Morse-Merryman Road and east of the Boulevard Storage Tank, to address storage deficiencies in Zone 417.

•    Fir Street Storage Tank #1 and #2 seismic retrofit to maintain compliance with seismic codes and to ensure reliability of the facility.

•    Elliot Storage Tank seismic retrofit.

•    Hoffman Storage Tank Interior Coating. Maintenance to ensure longevity of the tank.

Table 9.2 Evaluation of Storage Adequacy for Zone 417 and Zone 338

Year

2015

2020

2034

Max (10)

Projected Equivalent Residential Units (ERUs)

14,500

15,825

19,976

47,415

Projected Demand(1)

 

 

 

 

Average Day

2,407,000

2,627,000

3,316,000

7,870,871

Maximum Day

4,785,000

5,145,000

6,226,000

15,335,742

Available, Existing + Future Source (gpd)(2)

 

 

 

 

South Sound Booster (2,350 gpm)

3,384,000

3,384,000

3,384,000

3,384,000

Fones Road Booster (1,950 gpm)

2,808,000

2,808,000

2,808,000

2,808,000

Shana Well and Corrosion Facility (1,000 gpm)

1,440,000

1,440,000

1,440,000

1,440,000

Hoffman Well 3 (S08) (1,000 gpm)

1,440,000

1,440,000

1,440,000

1,440,000

Indian Summer Well 20 (S12) (850 gpm)

1,224,000

1,224,000

1,224,000

1,224,000

Briggs Well (1,100 gpm)

0

0

1,584,000

1,584,000

Total Available Source (gpd)

10,296,000

10,296,000

11,880,000

11,880,000

Multi-Source Credit (gpd)(3)

8,568,000

8,568,000

10,152,000

10,152,000

Required Storage Calculations

 

 

 

 

Operating Storage (gal)(4)

448,314

448,314

448,314

448,314

Equalizing Storage (gal)(5)

0

0

0

1,396,605

Standby Storage (gal)(6)

2,900,000

3,165,060

3,995,181

9,482,977

Fire Flow Storage (gal)(7)

960,000

960,000

960,000

960,000

Required Storage

 

 

 

 

Greater than 30 psi at highest meter (gal)(8)

448,314

448,314

448,314

1,844,919

Greater than 20 psi at highest meter (gal)(9)

4,308,314

4,573,375

5,403,495

12,287,896

Existing Storage Greater Than 30 psi (gal)(11)

 

 

 

 

Hoffman Storage Tank

3,692,000

3,692,000

3,692,000

3,692,000

New Log Cabin Storage Tank

0

6,377,000

6,377,000

6,377,000

Boulevard Storage Tank

1,629,287

1,629,287

1,629,287

1,629,287

Total Existing Storage at 30 psi (gal)

5,321,287

11,698,287

11,698,287

11,698,287

Storage Surplus/(Deficiency) at 30 psi (gal)

4,872,973

11,249,973

11,249,973

9,853,368

Existing Storage Greater Than 20 psi (gal) (11)

 

 

 

 

Hoffman Storage Tank

3,692,000

3,692,000

3,692,000

3,692,000

New Log Cabin Storage Tank

0

6,377,000

6,377,000

6,377,000

Boulevard Storage Tank

2,218,896

2,218,896

2,218,896

2,218,896

Total Existing Storage at 20 psi (gal)

5,910,896

12,287,896

12,287,896

12,287,986

Storage Surplus/(Deficiency) at 20 psi (gal)

1,602,582

7,714,522

6,884,401

0

Table 9.3 Evaluation of Storage Adequacy for Zone 417

 

 

Year

 

 

2015

2020

2034

Max (11)

Projected Equivalent Residential Units (ERUs)

11,807

12,910

16,855

26,602

Projected Demand(1)

 

 

 

 

 Average Day

1,960,000

2,143,000

2,798,000

4,415,927

 Maximum Day

3,897,000

4,198,000

5,254,000

8,489,853

Available, Existing + Future Source (gpd)(2)

 

 

 

 

 South Sound Booster (2,350 gpm)

3,384,000

3,384,000

3,384,000

3,384,000

 Fones Road Booster (1,950 gpm)

2,808,000

2,808,000

2,808,000

2,808,000

Shana Park Well 11 (S10) and Corrosion Facility (1,000 gpm)

1,440,000

1,440,000

1,440,000

1,440,000

 Hoffman Well 3 (S08) (1,000 gpm)

1,440,000

1,440,000

1,440,000

1,440,000

 Indian Summer Well 20 (S12) (850 gpm)

1,224,000

1,224,000

1,224,000

1,224,000

 Briggs Well (1,100 gpm)

0

0

1,188,000

1,188,000

Total Available Source (gpd)

10,296,000

10,296,000

11,484,000

11,484,000

Multi-Source Credit (gpd)(3)

8,856,000

8,856,000

10,044,000

10,044,000

Required Storage Calculations

 

 

 

 

 Operating Storage (gal)(4)

448,314

448,314

448,314

448,314

 Equalizing Storage (gal)(5)

0

0

0

286,207

 Standby Storage (gal)(6)

2,361,446

2,581,928

3,371,084

5,320,393

 Fire Flow Storage (gal)(7)

960,000

960,000

960,000

960,000

Required Storage

 

 

 

 

 Greater than 30 psi at highest meter (gal)(8)

448,314

448,314

448,314

734,521

 Greater than 20 psi at highest meter (gal)(9)

3,769,760

3,990,242

4,779,399

7,014,915

Existing Storage Greater Than 30 psi (gal)

 

 

 

 

 Hoffman Storage Tank

1,892,657

1,892,657

1,892,657

1,892,657

 New Log Cabin Storage Tank

0

3,415,466

3,415,466

3,415,466

Total Existing Storage at 30 psi (gal)

1,892,657

5,308,123

5,308,123

5,308,123

Storage Surplus/(Deficiency) at 30 psi (gal)

1,444,343

4,859,808

4,859,808

4,573,602

Existing Storage Greater Than 20 psi (gal)

 

 

 

 

 Hoffman Storage Tank

2,501,229

2,501,229

2,501,229

2,501,229

 New Log Cabin Storage Tank

0

4,513,686

4,513,686

4,513,686

Total Existing Storage at 20 psi (gal)

2,501,229

7,014,915

7,014,915

7,014,915

Storage Surplus/(Deficiency) at 20 psi (gal)

(1,268,531)

3,024,673

2,235,516

0

Table 9.4 Evaluation of Storage Adequacy for Zone 347

Year

2015

2020

2034

Max (10)

Projected Equivalent Residential Units (ERUs)

3,849

3,855

4,259

10,258

Projected Demand(1)

 

 

 

 

Average Day

639,000

640,000

707,000

1,702,841

Maximum Day

1,271,000

1,254,000

1,327,000

3,318,681

Available, Existing + Future Source (gpd)(2)

 

 

 

 

Eastside Booster (2,000 gpm)

2,880,000

2,880,000

2,880,000

2,880,000

Total Available Source (gpd)

2,880,000

2,880,000

2,880,000

2,880,000

Multi-Source Credit (gpd)(3)

2,880,000

2,880,000

2,880,000

2,880,000

Required Storage Calculations

 

 

 

 

Operating Storage (gal)(4)

105,538

105,538

105,538

105,538

Equalizing Storage (gal)(5)

0

0

0

278,095

Standby Storage (gal)(6)

769,880

771,084

851,807

2,051,615

Fire Flow Storage (gal)(7)

120,000

120,000

120,000

120,000

Required Storage

 

 

 

 

Greater than 30 psi at highest meter (gal)(8)

105,538

105,538

105,538

383,633

Greater than 20 psi at highest meter (gal)(9)

995,418

996,623

1,077,346

2,555,249

Existing Storage Greater Than 30 psi (gal)

 

 

 

 

Eastside Storage Tank

1,946,373

1,946,373

1,946,373

1,946,373

Total Existing Storage at 30 psi (gal)

1,946,373

1,946,373

1,946,373

1,946,373

Storage Surplus/(Deficiency) at 30 psi (gal)

1,840,834

1,840,834

1,840,834

1,562,740

Existing Storage Greater Than 20 psi (gal)

 

 

 

 

Eastside Storage Tank

2,555,249

2,555,249

2,555,249

2,555,249

Total Existing Storage at 20 psi (gal)

2,555,249

2,555,249

2,555,249

2,555,249

Storage Surplus/(Deficiency) at 20 psi (gal)

1,559,831

1,558,626

1,477,903

0

Table 9.5 Evaluation of Storage Adequacy for Zone 264

Year

2015

2020

2034

Max (12)

Projected Equivalent Residential Units (ERUs)

2,596

2,675

2,970

>2,970

Projected Demand(1)

 

 

 

 

Average Day

431,000

444,000

493,000

493,000

Maximum Day

859,000

869,000

926,000

926,000

Available, Existing + Future Source (gpd)(2)

 

 

 

 

10" Water Main (2,545 gpm)

3,664,800

3,664,800

3,664,800

3,664,800

Capitol Way PRV (1,310 gpm)

1,886,400

1,886,400

1,886,400

1,886,400

Brewery Well (1,000 gpm)

0

0

0

0

Total Available Source (gpd)(3)

5,551,200

5,551,200

5,551,200

5,551,200

Multi-Source Credit (gpd)

3,664,800

3,664,800

3,664,800

3,664,800

Required Storage Calculations

 

 

 

 

Operating Storage (gal)(4)

375,000

375,000

375,000

375,000

Equalizing Storage (gal)(5)

0

0

0

0

Standby Storage (gal)(6)

519,277

534,940

593,976

593,976

Fire Flow Storage (gal)(7)

960,000

960,000

960,000

960,000

Required Storage

 

 

 

 

Greater than 30 psi at highest meter (gal)(8)

375,000

375,000

375,000

375,000

Greater than 20 psi at highest meter (gal)(9)

1,854,277

1,869,940

1,928,976

1,928,976

Existing Storage Greater Than 30 psi (gal)

 

 

 

 

Stevens Field Storage Tank

163,489

163,489

163,489

163,489

Meridian Storage Tanks(10)

1,508,677

1,524,340

1,583,376

1,583,376

Total Existing Storage at 30 psi (gal)

1,672,166

1,687,828

1,746,864

1,746,864

Storage Surplus/(Deficiency) at 30 psi (gal)

1,297,166

1,312,828

1,371,864

1,371,864

Existing Storage Greater Than 20 psi (gal)

 

 

 

 

Stevens Field Storage Tank

304,882

304,882

304,882

304,882

Meridian Storage Tanks(10)

1,508,677

1,524,340

1,583,376

1,583,376

Boulevard Storage Tank(11)

316,800

316,800

316,800

316,800

Total Existing Storage at 20 psi (gal)

2,130,359

2,146,021

2,205,058

2,205,058

Storage Surplus/(Deficiency) at 20 psi (gal)

276,082

276,082

276,082

276,082

Table 9.6 Evaluation of Storage Adequacy for Zone 226, 298 and 380

Year

2015

2020

2034

Max (10)

Projected Equivalent Residential Units (ERUs)

17,500

18,867

21,675

35,244

Projected Demand(1)

 

 

 

 

Average Day

2,905,000

3,132,000

3,598,000

5,850,585

Maximum Day

5,776,000

6,133,000

6,755,000

11,260,171

Available, Existing + Future Source (gpd)(2)

 

 

 

 

36" Water Main (4000 gpm)

5,760,000

5,760,000

5,760,000

5,760,000

Allison Well 19 (S11) (900 gpm)

1,296,000

1,296,000

1,296,000

1,296,000

Allison Well 13 (S09) (650 gpm)

936,000

936,000

936,000

936,000

Kaiser Well 1 (S03) (360 gpm)

518,400

0

0

0

Indian Springs Well 20 (S12) (850 gpm)

1,224,000

1,224,000

1,224,000

1,224,000

Total Available Source (gpd)

9,734,400

9,216,000

9,216,000

9,216,000

Multi-Source Credit (gpd)(3)

3,974,400

3,456,000

3,456,000

3,456,000

Required Storage Calculations

 

 

 

 

Operating Storage (gal)(4)

2604,153

2604,153

2604,153

2604,153

Equalizing Storage (gal)(5)

0

94,481

249,815

1,000,676

Standby Storage (gal)(6)

3,500,000

3,773,494

4,334,940

8,245,171

Fire Flow Storage (gal)(7)

960,000

960,000

960,000

960,000

Required Storage

 

 

 

 

Greater than 30 psi at highest meter (gal)(8)

2,604,153

2,698,634

2,853,967

3,604,829

Greater than 20 psi at highest meter (gal)(9)

7,064,153

7,432,128

8,148,907

12,810,000

Existing Storage Greater Than 30 psi (gal)

 

 

 

 

Fir 226 (north)

2,500,000

2,500,000

2,500,000

2,500,000

Fir 226 (south)

2,500,000

2,500,000

2,500,000

2,500,000

Bush 298

1,050,000

1,050,000

1,050,000

1,050,000

Elliott 298

2,000,000

2,000,000

2,000,000

2,000,000

Elliott 380

4,760,000

4,760,000

4,760,000

4,760,000

Total Existing Storage at 30 psi (gal)

12,810,000

12,810,000

12,810,000

12,810,000

Storage Surplus/(Deficiency) at 30 psi (gal)

10,205,847

10,111,366

9,956,033

9,205,171

Existing Storage Greater Than 20 psi (gal)

 

 

 

 

Fir 226 (north)

2,500,000

2,500,000

2,500,000

2,500,000

Fir 226 (south)

2,500,000

2,500,000

2,500,000

2,500,000

Bush 298

1,050,000

1,050,000

1,050,000

1,050,000

Elliott 298

2,000,000

2,000,000

2,000,000

2,000,000

Elliott 380

4,760,000

4,760,000

4,760,000

4,760,000

Total Existing Storage at 20 psi (gal)

12,810,000

12,810,000

12,810,000

12,810,000

Storage Surplus/(Deficiency) at 20 psi (gal)

5,745,847

5,377,872

4,661,093

0

Table 9.7 Evaluation of Storage Adequacy for Zone 380

 

 

Year

 

 

2015

2020

2034

Max (10)

Projected Equivalent Residential Units (ERUs)

4,343

4,663

5,416

9,121

Projected Demand(1)

 

 

 

 

Average Day

721,000

774,000

899,000

1,514,150

Maximum Day

1,434,000

1,516,000

1,688,000

2,918,300

Available, Existing + Future Source (gpd)(2)

 

 

 

 

West Bay Booster (2,400 gpm)

3,456,000

3,456,000

3,456,000

3,456,000

Elliot Booster Pump Station (2,300 gpm)

3,312,000

3,312,000

3,312,000

3,312,000

Total Available Source (gpd)

6,768,000

6,768,000

6,768,000

6,768,000

Multi-Source Credit (gpd)(3)

5,904,000

5,904,000

5,904,000

5,904,000

Required Storage Calculations

 

 

 

 

Operating Storage (gal)(4)

618,800

618,800

618,800

618,800

Equalizing Storage (gal)(5)

0

0

0

0

Standby Storage (gal)(6)

868,675

932,530

1,083,133

1,824,277

Fire Flow Storage (gal)(7)

120,000

120,000

120,000

120,000

Required Storage

 

 

 

 

Greater than 30 psi at highest meter (gal)(8)

618,800

618,800

618,800

618,800

Greater than 20 psi at highest meter (gal)(9)

1,607,475

1,671,330

1,821,933

2,563,077

Existing Storage Greater Than 30 psi (gal)

 

 

 

 

Elliot 380 Storage Tank

1,464,615

1,464,615

1,464,615

1,464,615

Total Existing Storage at 30 psi (gal)

1,464,615

1,464,615

1,464,615

1,464,615

Storage Surplus/(Deficiency) at 30 psi (gal)

845,815

845,815

845,815

845,815

Existing Storage Greater Than 20 psi (gal)

 

 

 

 

Elliot 380 Storage Tank

2,563,077

2,563,077

2,563,077

2,563,077

Total Existing Storage at 20 psi (gal)

2,563,077

2,563,077

2,563,077

2,563,077

Storage Surplus/(Deficiency) at 20 psi (gal)

955,602

891,747

741,144

0