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Ammon Foothill MPC_Water Study_Keller 2 Project No. 221128 The proposed development lies within a range of elevations that fall between those served by two of the City of Ammon’s existing drinking water pressure zones (Zone 1 and Zone 2). As a result, at least one new pressure zone must be created to serve this development. This technical memo documents this development’s impacts to the City of Ammon’s drinking water system and provides recommended system improvements to address those impacts. Drinking water system improvements were selected in order to comply with the City standards described in the 2018 Ammon Water Facilities Planning Study (WFPS) and with the Idaho Drinking Water Rules (IDAPA 58.01.08). 2.0 DRINKING WATER SYSTEM 2.1 DEMAND To evaluate the development’s drinking water needs as they pertain to state Drinking Water Rules, a maximum day demand (MDD) and peak hour demand (PHD) for the development were developed based on the land uses and number of residential units shown in the concept layout. Assumptions used to estimate a potable water demand per unit (household) were consistent with those used for other development requests since the implementation of the City’s pressurized irrigation requirement. Per the City’s request, the assumption for average household density was updated to 2.96 persons/household (average 2015-2019 household density, US Census Bureau QuickFacts). This results in a MDD of 0.37 gallons per minute (gpm)/household and PHD of 0.49 gpm/household (applicable for large area analysis only). Commercial demands were estimated using water meter records for a similarly sized commercial area on 17th Street in Ammon, comprised of a variety of business types. Demands for the two school areas were estimated assuming that the school areas shown in the concept layout would accommodate the needs of all k-8th grade students generated by the development. It was assumed that all high school students would attend a high school outside of the development. State code guidelines for wastewater generation at schools were used to estimate a demand of 29 gallons per day (gpd)/student for k-5 and 35 gpd/student for grades 6-8. Table 1 shows the MDD and PHD values estimated for the development. A Winter Day Demand (WDD) of 780 gpm for the entire development was also calculated for modeling purposes and represents a more typical demand outside of heavy demand times. Calculations related to the values presented in this section are found in Appendix B. TABLE 1 - Development Drinking Water Demands MDD (gpm*) PHD (gpm*) 2021 Existing Ammon System 11,310 16,250 Development Residential 1,170 1,530 Development Commercial 1.1 1.5 Development School 40 50 Development Total 1,210 1,580 Ammon Total w/ Development 12,520 17,840 * gpm = gallons per minute, an average of demand over the max day or peak hour 3 Project No. 221128 Current existing demands for the City of Ammon were taken from other modeling efforts performed for the City earlier this year (Brogan Creek Tech Memo dated 03-25-2021 and addenda). 2.2 SUPPLY ANALYSIS State Drinking Water Rules require that water system sources (almost exclusively groundwater in Eastern Idaho) provide PHD with any given pump out of service. This requirement can be reduced to meeting only MDD where water storage is available to make up the difference (see Storage Analysis). Ammon’s typical mode of operation is to provide MDD with this “equalization” storage as this can reduce pumping costs and impacts to water rights. Although Ammon’s system has several pressure zones, all of its wells are currently located in pressure Zone 1 (valley floor). If the development were to be served through Zone 1 sources, it’s impact to the system’s “firm capacity” (the total groundwater supply with largest pump out of service) are shown in Table 2. If the development were served through new wells dedicated solely to this pressure zone those wells would need to provide the full 1,210 MDD of new system demand. TABLE 2 – Supply Capacity Impacts Existing System With Development MDD (gpm) 11,310 12,520 Firm Capacity (gpm) 13,430 13,430 Surplus/(Deficit) (gpm) 2,110 905 The developer is unaware of any existing groundwater rights associated with this property. This development will need available groundwater rights of at least the MDD, assuming equalization storage is constructed to cover demands beyond MDD. 2.3 STORAGE ANALYSIS Drinking water storage must provide for the firefighting, operational, and equalization storage needs of the zone(s) it serves. The City typically removes the need for stand-by/emergency storage by including backup power generation at well sites. Fire flow storage is calculated as the total volume needed to supply the largest applicable fire flow (commercial/school fire event, see Delivery Analysis section). Equalization storage is the volume of water needed to meet any demands greater than the MDD for which well pumps are sized (such as PHD). Operational storage is the tank volume which empties between when the well pump turns off after filling the tank to when the pump is activated again. This reduces pump on/off cycles and has been estimated at 10% of total storage per the 2018 WFPS. Dead storage refers to the tank volume not accessible by booster pumps (minor, 1% assumed here). The total amount of storage needed for this development is shown in Table 3. 4 Project No. 221128 TABLE 3 – Storage Capacity Impacts Category Required (Gallons) Dead 7,000 Operational 65,000 Fire Flow 450,000 Equalization 131,000 Standby/Emergency 0 TOTAL 653,000 2.4 DELIVERY ANALYSIS Delivery capacity refers to the system’s ability to deliver flow rates at acceptable pressures. The Idaho Drinking Water Rules require that drinking water systems meet the criteria in Table 4. TABLE 4 - System Pressure Requirements Flow Condition Required Pressure Typical Operating Range 40 psi – 80 psi Fire Flow Event 20 psi minimum Required firefighting flows for the City of Ammon depend on land use. Planning demands for new development were reviewed with the Ammon Fire Marshall and are shown in Table 5. TABLE 5 - Fire Flow Requirements Property Type Required Fire Flow Residential 1500 gpm for 2 hours Commercial/School 2500 gpm for 3 hours Industrial 4500 gpm for 4 hours A pump station delivering flow to the development must be able to supply both PHD. It must also supply MDD during a fire event. Both conditions must be met with any pump out of service (code redundancy requirement). In the case of this development, total pumping capacity required is governed by the commercial/school fire flow requirement and MDD for the total shown in Table 6. TABLE 6 - Delivery Capacity Impacts Flow Rate (gpm) Fire Flow Demand 2,500 Max Day Demand 1,210 Minimum Pumping Capacity Required 3,710 5 Project No. 221128 2.5 SYSTEM IMPROVEMENTS The proposed development covers a range of elevations that are not currently served by Ammon’s drinking water system. This will require the establishment of a new pressure zone. While there are several ways in which the supply, storage, and delivery requirements of this development could be met, the proposed improvements represent our recommendation for a solution that keeps improvements within the developer’s control. Other solutions involving sharing of resources with other pressure zones may exist that would require additional buy-in from the City and/or third-party landowners. Based on discussions with a local hydrogeologist, there is a reasonable chance that a well drilled in the development could produce 2,000 gpm. This means that the new pressure zone will require two separate 1,300 gpm minimum wells, a primary well meeting MDD requirements and an equally sized redundant well. One cost effective solution for this would be to have a main wellhouse with a line-shaft vertical turbine pump and the necessary valves, meters, sampling, etc. for state compliance and to install the other well as a submersible pump piped to the main wellhouse. The submersible well would not need to be housed in a building and could simply be fenced for security. Due to the variability of local hydrogeology, we recommend that test wells be drilled at proposed well sites to verify suitability prior to finalization and to verify that well areas of influence do not negatively impact neighboring properties. Separation between wells should follow the recommendations of a hydrogeologist but should be no closer than 100 ft from one another. Wells drilled further up the bench in this area have dealt with water quality issues (temperature, pH, etc.); we recommend that well sites be kept on the lower “flat” portion of the proposed development. A single 653,000-gallon minimum tank should be constructed to meet storage needs. A booster station capable of delivering PHD and MDD plus fire flow should also be constructed adjacent to the tank and set to target a hydraulic grade of 4925 ft in order to ensure minimum pressures are produced during PHD and fire events. While the wells and tank/booster station could be located at two separate sites, transmission piping and other costs will be reduced by placing everything at the same site if space allows. This is the assumption used for the cost evaluation. Backup power generation should be provided for all facilities; if site spacing is such that backup power cannot be efficiently run to all well and booster pumps from the single permanent generator, then a portable generator and necessary hookups should be provided for the submersible well. Space for a future chlorination system should also be provided at the wellhouse. WaterCAD hydraulic modeling software was used to evaluate the placement and capacity of improvements required to meet the pressure and flow requirements previously described. A proposed system layout is shown in Figure 2. Pipe diameters shown are nominal and were sized to facilitate pressure requirements and future expansion of the zone to the north and south. See Appendix C for detailed modeling results. 6 Project No. 221128 FIGURE 2 – Proposed Drinking Water Improvements 7 Project No. 221128 The system was modeled with DR 11 HDPE pipe and features a combination of 14” and 12” diameter water transmission lines for equivalent functionality to the recommendations found in the 2018 WFPS. 8” and 10” distribution lines shown were generically placed to provide even coverage over the development and do not correspond to actual minor street locations (unknown at time of evaluation). Planning and placement of actual drinking water distribution lines should follow roadway alignments. We recommend that the model be updated with actual water line locations in order to verify suitability of waterline and pump station placement before improvements are designed. Though not shown in Figure 2, we recommend that emergency supply from pressure zone 2 through a pressure reducing valve also be provided to mitigate the effects of a major catastrophe at the booster station. It became apparent while modeling that the span of elevations encompassed by the development may be slightly too large to be contained within a single pressure zone without causing pressure issues (too high at the bottom or too low at the top). The City of Ammon has indicated that rather than split this development into two zones, individual pressure reducing valves (PRVs) should be installed on all homes whose pressures exceed the 80 psi maximum during low demand times (typically winter months). Modeling results in Appendix C show locations where pressures approach 80 psi; however, model results assume 5 psi variability and installation of individual PRVs should be determined by actual system pressures once constructed. The modeling shows that the pumps in Table 7 satisfy the pressure and flow demands described previously. This exercise is only intended to provide estimates of pump size and number; these values should be confirmed through further analysis during design of the actual improvements. A booster station consisting of six pumps, two fire flow pumps, two main pumps and two smaller pumps, is proposed to meet the anticipated range of flows and to satisfy state redundancy requirements. TABLE 7 – Model-Based Pump Selection Wells Number of Wells 2 Minimum Design Flowrate Each (gpm) 1,300 Design Head (ft) 117 Estimated Horsepower Each 60 Booster Station Design Head (ft) 200 Target Hydraulic Grade (ft) 4,925 (2) 100 HP Fire Flow Pumps - Design Flowrate (gpm) 1,300 (2) Main Pumps - Design Flowrate (gpm) 800 (1) 40 HP Intermediate Pump - Design Flowrate (gpm) 500 (1) 30 HP Low-Flow Pump - Design Flowrate (gpm) 350 All facilities should feature variable frequency drives and meet all other City of Ammon requirements. The booster pumps presented assume full build-out conditions, it may be necessary to adjust or install temporary pumps to accommodate phased construction of the 8 Project No. 221128 development. The developer will coordinate supply solutions for phased build out separately with the City. An opinion of cost for the wells, tank, and booster station improvements is provided in Table 8. Costs assume a buried tank with the booster station constructed above, similar to the Ammon Well 13 project currently under construction. Pipeline costs have not been included in these values as the development layout (which will determine the length of pipe required) has not been finalized. Market volatility continues to be high for pipe and other infrastructure components; the costs shown include a 30% contingency amount and are order of magnitude level only. Additional details are presented in Appendix D. Table 8 – Drinking Water Improvements Opinion of Cost Engineer’s Opinion of Cost Wells $1,748,000 Tank and Site $2,757,000 Booster Pump Station $1,460,000 Professional Services $1,213,000 TOTAL $7,177,000 9 Project No. 221128 APPENDICES Appendix A – Developer’s Concept Layout Appendix B – Calculations Appendix C – Modeling Results Appendix D – Cost Estimates 10 Project No. 221128 APPENDIX A – DEVELOPER’S CONCEPT LAYOUT 10 Project No. 221128 APPENDIX B - DRINKING WATER CALCULATIONS DEMANDS Base Demands (GPM) 117 gpcd winter day demand (2018 WFPS) 2.96 people/household (2015-2019 average density per US Census Bureau QuickFacts) 1.5 Culinary Winter to Summer Factor (from Kuna) 1.03 Avg Winter Day to MDD Factor (previous modeling, see #219067) 1.35 Avg Winter Day to PHD Factor (previous modeling) 3141.00 Total Housing Units 9297.36 Subdivision Population Added Residential MDD 0.37 GPM/household PHD 0.49 GPM/household (0.51 gpm/household used in 2019/2020 modeling) MDD 1,167 GPM, Total Residential Demand Added PHD 1,530 GPM, Total Residential Demand Added Commercial 1,039 gpd Avg Winter Day 1,558 gpd max month MDD 1.1 GPM Total PHD 1.5 GPM Total School 25.1%School age (5-17) % of Population (US Census Bureau QuickFacts) 1,167 k-5 students 583 6-8 students 778 9-12 students 33,546 Elementary School GPD Gal/day/student values from IDAPA 58.01.03, 20% consumption 20,419 Jr High GPD Assumes Elementary and Jr High only 0 High School GPD MDD 38.60 GPM, Schools Total PHD 50.59 GPM, Schools Total TOTAL NEW DEMAND MDD 1,207 GPM PHD 1,582 GPM WDD 781 GPM TOTAL SYSTEM DEMAND (Current and New) MDD 12,520 GPM PHD 17,835 GPM Fire Flow Demands (GPM) Residential 1500 for 2 hrs Commercial/K-12 2500 for 3 hrs College/Industrial 4500 for 2 hrs Assumes Elementary and Jr High only, no High School. Gal/Day/Student values from IDAPA 58.01.03 with 20% consumption assumed to go from wastewater to potable water usage. Elementary (cafeteria, no showers) = 29 gal/day/student Jr High (cafeteria, showers) = 35 gal/day/student Commercial Demand Details Address Business Jan 2016 Metered Usage (Gal/Month) 1615 Market Way Taqueria El Rodeo 1029 1639 Market Way Posh Hair and Nail Salon 3449 3379 E 17th St Subway Restaurant 5471 1675 Market Way Domino's Pizza 9790 1655 Market Way Petal Passion Floral 312 1665 Market Way Ripp'd Nutrition 899 3415 E 17th St Ace Hardware 2338 3475 E 17th St.Walgreens 8829 3456 E 17th St.Business Park 91 TOTAL:32208 gal/month 1,039 gpd 0.72 avg gpm This area of Ammon has mixed commercial/business usage and is approximately 8 acres in total to match the commerical area of this subdivision. Intersection of Ammon Road and 17th Street. Area Base MDD Units Total MDD Nodes Demand per Node Commercial - -1.11 10 0.11 Village 1 0.37 490 182.07 11 16.55 Village 2 0.37 845 313.98 29 10.83 - Not including school area Neighborhood 2 0.37 180 66.88 24 2.79 Village 3 0.37 688 255.64 16 15.98 Village 4 0.37 322 119.65 6 19.94 - Not including school area Neighborhood 3 0.37 97 36.04 4 9.01 Neighborhood 1 0.37 163 60.57 15 4.04 Regional Park - 0 - 1 0.00 Neighborhood 5 0.37 176 65.40 21 3.11 Neighborhood 4 0.37 180 66.88 22 3.04 School - Village 2 19.30 19.30 School - Village 4 19.30 19.30 Model Demand Summary SUPPLY ANALYSIS Existing System Well ID Production (gpm)Motor hp VFD Emergency Power? Year Drilled Well 2 325 25 No No 1952 Well 3 (inactive)50 No No 1957 Well 5 1000 100 No No 1967 Well 6 (inactive)75 Yes Yes 1973 Well 7 1850 200 No No 1968 Well 8 4200 400 Yes Yes 1996 Well 9 1850 200 Yes Yes 2001 Well 10 3000 400 Yes Yes 2008 Well 11 3000 500 Yes Yes 2008 Well 13 2400 200 Yes Yes 2020 Total 17625 Firm Capacity 13425 System Wide 2020 Pop 2021 + Development MDD 11,313 12,520 gpm Firm Capacity 13,425 13,425 gpm Surplus/(Deficit)2,112 905 gpm Zone Specific 2020 Pop 2021 + Development MDD 0 1,210 gpm Firm Capacity 0 0 gpm Surplus/(Deficit)0 (1,210)gpm Well Assumptions Elev Static H2O Depth H20 Elev Well 11 4740 52 4688 ft Well 9 4819 124 4695 ft New Well Elev 4755 ft Lift to Surface from 4688'67 ft Lift to Tank (buried)0 ft Minor Losses 10 ft Drawdown, Decline, Seasonal Variation 40 ft TDH 117 ft New Wells Q H hp calc hp Actual Prime 1300 117 53 60 Redundant 1300 117 53 60 DELIVERY ANALYSIS Per state code, must be able to produce the larger of Peak Hour Demand or Max Day Demand Plus Fire Flow with any pump out of service. Target hydraulic grade for pumps was determined through hydraulic modeling, see Appendix C. Alternate option for pump sizing below: WDD 780 gpm MDD 1210 gpm MDD+FF 3710 gpm PHD 1580 gpm Option 2 Booster Q H hp calc hp Actual 800 200 56 60 800 200 56 60 1300 200 91 100 1300 200 91 100 (2) 100 HP Fire Pumps 750 to 1300 each (2) 60 HP Main pumps 400 850 800 each Combo of 30 HP and 50 HP 200 to 850 40 HP Intermediate Pump 250 to 500 30 HP Low Flow Pump 175 to 350 *Assumes safe operation of pumps in middle third of curve, with Design Point being upper end of that third (i.e. lower end equals design point divided by 2). Flow Range Served (GPM) Option 1 Booster Q H hp calc hp Actual 1000 200 70 75 1000 200 70 75 1000 200 70 75 1000 200 70 75 (4) 75 HP Main pumps 500 to 1000 each Combo of 30 HP and 50 HP 200 to 1000 50 HP Intermediate Pump 300 to 600 30 HP Low Flow Pump 200 to 400 Flow Range Served (GPM) STORAGE ANALYSIS Fire Storage Operational and Dead Storage Largest Fire Flow =2500 gpm for:3 hrs Required Fire Storage 450000 gal 0.4500000 MG Operational Storage Req'd:10% Dead Storage Req'd:1% Equalization Storage if Well Capacity = MDD Development MDD(gpm) Cumulative Storage (gal) EQ Storage (gal) Hour Smooth Unit Demand 1068 -8324 -9887 0:00 0.885 1016 -19773 -12473 1:00 0.842 982 -33270 -14220 2:00 0.814 958 -48213 -16112 3:00 0.794 919 -65495 -19159 4:00 0.761 856 -86532 -19736 5:00 0.710 900 -104967 -10446 6:00 0.745 1166 -107425 5604 7:00 0.966 1435 -93759 17651 8:00 1.189 1568 -72123 23428 9:00 1.299 1627 -46903 22995 10:00 1.348 1553 -26133 17788 11:00 1.287 1454 -11327 12302 12:00 1.204 1370 -1530 7778 13:00 1.135 1303 4230 4519 14:00 1.080 1262 7509 3916 15:00 1.045 1283 12062 4456 16:00 1.063 1280 16421 4399 17:00 1.060 1281 20860 4111 18:00 1.061 1270 24642 2103 19:00 1.052 1214 25066 -762 20:00 1.006 1175 23118 -2917 21:00 0.973 1142 19232 -3308 22:00 0.946 1161 16502 -5527 23:00 0.962 1068 23:59 0.885 1218 AVERAGE: 0.03 0.13 Required EQ Storage (MG) 0.131 EQ Deficit (MG) 0.653 Additional Storage Needed (MG) Population:9297 MDD:1,207 gpm Equalization storage is the cumulative amount of volume over a day required by the system beyond the well supply capacity serving the tank. MDD EQ Storage Hourly Demand 10 Project No. 221128 APPENDIX C - DRINKING WATER MODELING RESULTS MAXIMUM DAY DEMAND *For all model runs a 5 psi buffer from specified pressure limits was used to ensure satisfactory performance. All scenarios feature a booster station supplying 4,925 ft target discharge hydraulic head. All results produced in Bentley’s OpenFlows WaterCAD CONNECT Edition hydraulic modeling software. MAXIMUM DAY DEMAND WITH FIRE FLOWS Pressures shown are the residual pressure at each node under its assigned fire flow requirement. All nodes met or exceeded MDD plus fire flow requirements without dropping any node in the zone below 20 psi. PEAK HOUR DEMAND WINTER DAY DEMAND *Any nodes that report pressures above 75 psi (80 psi max minus 5 psi factor of safety modeling buffer) may exceed state standards for max pressure depending on actual system performance. 10 Project No. 221128 APPENDIX F - OPINIOF COST APPENDIX F - OPINION OF COST General Line Items Unit Unit Price Estimated Quantity 2019 Cost Test Well EA 45,000$ 2 90,000$ Well Drilling EA 200,000$ 2 400,000$ Well Pump (Vertical Turbine) - 60 HP EA 100,000$ 1 100,000$ Well Pump (Submersible) - 60 HP EA 80,000$ 1 80,000$ Mechanical Piping LS 60,000$ 1 60,000$ Main Well Building - CMU Construction SF 210$ 1500 315,000$ IndoorBackup Generator LS 203,000$ 1 203,000$ Booster Station Building - CMU Construction SF 210$ 2030 426,300$ Fire Flow Pumps (Vertical Turbine) - 100 HP EA 96,000$ 2 192,000$ Main Pumps (Vertical Turbine) - 60 HP EA 78,000$ 2 156,000$ Intermediate Pump (Vertical Turbine) - 40 HP EA 69,600$ 1 70,000$ Low-Flow Pump (Vertical Turbine) - 30 HP EA 48,000$ 1 48,000$ Mechanical Piping LS 150,000$ 1 150,000$ Cast-in-Place Concrete Tank - 660,000 gallons LS 726,000$ 1 726,000$ Yard Piping LS 290,000$ 1 290,000$ Site Concrete and Asphalt LS 83,000$ 1 83,000$ Plumbing, Electrical, and HVAC LS 750,000$ 1 750,000$ Instrumentation and Controls (SCADA)LS 50,000$ 1 50,000$ Site Grading LS 20,000$ 1 20,000$ Landscaping & Fencing - Basic LS 50,000$ 1 50,000$ Construction Subtotal 4,259,300$ Mobilization % 10%426,000$ Contingency - % of construction costs % 30%1,278,000$ Total Construction Costs 5,963,300$ Additional Services (Permitting, Geotech, Legal) LS 20,000$ 1 20,000$ Engineering and CMS LS 1,193,000$ 1 1,193,000$ Total Project Cost (rounded)$7,177,000 Wells Booster Station Building Tank & Site Professional Services Project Location: Ammon, ID Capital Improvements Project BCP Development Project Identifier: BCP Development Objectives: - Create a new pressure zone by installing wells, a tank, and a booster station. Potential Issues: - Current supply chain and labor issues Assumes: - Wells, tank, and booster station are built at the same site. - Tank is buried cylindrical AWWA Type 3 prestressed concrete. - Booster station sits above tank as at Well 13 facility. - Does not include transmission/distribution line costs (including emergency PRVs from Zone 2 or canal crossings) as subdivision layout has not yet been finalized. The cost estimate herein is based on our perception of current conditions at the project location. This estimate reflects our opinion of probable costs at this time and is subject to change as the project design matures. Keller Associates has no control over variances in the cost of labor, materials, equipment, services provided by others, contractor's methods of determining prices, competitive bidding or market conditions, practices or bidding strategies. Keller Associates cannot and does not warrant or guarantee that proposals, bids, or actual construction costs will not vary from the cost presented herein.