Engineers | Scientists | Planners PARECORP.COM 8 BLACKSTONE VALLEY PLACE LINCOLN, RI 02865 T 401.334.4100 F 401.334.4108 10 LINCOLN ROAD, SUITE 210 FOXBORO, MA 02035 T 508.543.1755 F 508.543.1881 April 17, 2017 Mr. Charles Walsh Acting DPW Director – Town of Smithfield 64 Farnum Pike Smithfield, Rhode Island 02917 Re: Hydraulic Model Evaluation Proposed Village at Stillwater Smithfield, Rhode Island Pare Project No. 03066.48 Dear Mr. Walsh: As requested, Pare Corporation (Pare) has performed a hydraulic model evaluation of the proposed Village at Stillwater Development. The evaluation of the proposed development was performed using the existing computerized hydraulic model of the Smithfield Water Supply Board’s (SWSB) water supply and distribution system. Using the hydraulic model, proposed connections to the water system were simulated in order that the impact of the proposed improvements could be evaluated prior to construction. Background The proposed development is a mixed-use plan consisting of commercial, office, and retail space, as well as several residential units in the Town of Smithfield, RI. DiPrete Engineering Associates (DiPrete), the engineer for the development, provided information pertaining to the water system layout within the proposed development. DiPrete provided a 24”x36” set of plans entitled “The Village at Stillwater”, dated January 12, 2017. DiPrete proposes one connection on the existing 12-inch water main on George Washington Highway (Route 116) and another connection on the existing 16-inch water main on Douglas Pike (Route 7) creating a loop through the new development (refer to Attachment No. 1 – Partial Node and Pipeline Plan). The water main layout will include approximately 7,000 feet of new ductile iron pipe. While not specified on the drawings, it is assumed that this new water main will be 12 inches in diameter, which is reasonable given the size of the proposed development. DiPrete provided an estimate of domestic demand for the development, which is provided in Attachment No. 2. DiPrete estimated the average daily demand (ADD) for the proposed development to be 161,880 gpd (112.4 gpm). DiPrete provided a peaking factor of 4.0 for their peak water demand of 647,520 gpd (449.67 gpm). However, as part of the hydraulic model evaluation presented herein, Pare utilized peaking factors of 2.0 and 2.9 for maximum day demand (MDD) and peak hour (PH), respectively, which are consistent with the peaking factors experienced in the SWSB system at the time the model was last updated. DiPrete did not specify the needed fire flow demand (NFF) for the proposed development. Therefore, Pare modeled the available fire flow (AFF) throughout the development consistent with American Water Works Association (AWWA) Manual M31 – Distribution System Requirements for Fire Protection. The estimated demands for the proposed development are listed as follows:
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E n g i n e e r s | S c i e n t i s t s | P l a n n e r s
P A R E C O R P . C O M
8 BLACKSTONE VALLEY PLACE L INCOLN, RI 02865
T 401.334.4100 F 401.334.4108
10 L INCOLN ROAD, SUITE 210 FOXBORO, MA 02035
T 508.543.1755 F 508.543.1881
April 17, 2017 Mr. Charles Walsh Acting DPW Director – Town of Smithfield 64 Farnum Pike Smithfield, Rhode Island 02917 Re: Hydraulic Model Evaluation Proposed Village at Stillwater Smithfield, Rhode Island Pare Project No. 03066.48 Dear Mr. Walsh: As requested, Pare Corporation (Pare) has performed a hydraulic model evaluation of the proposed Village at Stillwater Development. The evaluation of the proposed development was performed using the existing computerized hydraulic model of the Smithfield Water Supply Board’s (SWSB) water supply and distribution system. Using the hydraulic model, proposed connections to the water system were simulated in order that the impact of the proposed improvements could be evaluated prior to construction. Background The proposed development is a mixed-use plan consisting of commercial, office, and retail space, as well as several residential units in the Town of Smithfield, RI. DiPrete Engineering Associates (DiPrete), the engineer for the development, provided information pertaining to the water system layout within the proposed development. DiPrete provided a 24”x36” set of plans entitled “The Village at Stillwater”, dated January 12, 2017. DiPrete proposes one connection on the existing 12-inch water main on George Washington Highway (Route 116) and another connection on the existing 16-inch water main on Douglas Pike (Route 7) creating a loop through the new development (refer to Attachment No. 1 – Partial Node and Pipeline Plan). The water main layout will include approximately 7,000 feet of new ductile iron pipe. While not specified on the drawings, it is assumed that this new water main will be 12 inches in diameter, which is reasonable given the size of the proposed development. DiPrete provided an estimate of domestic demand for the development, which is provided in Attachment No. 2. DiPrete estimated the average daily demand (ADD) for the proposed development to be 161,880 gpd (112.4 gpm). DiPrete provided a peaking factor of 4.0 for their peak water demand of 647,520 gpd (449.67 gpm). However, as part of the hydraulic model evaluation presented herein, Pare utilized peaking factors of 2.0 and 2.9 for maximum day demand (MDD) and peak hour (PH), respectively, which are consistent with the peaking factors experienced in the SWSB system at the time the model was last updated. DiPrete did not specify the needed fire flow demand (NFF) for the proposed development. Therefore, Pare modeled the available fire flow (AFF) throughout the development consistent with American Water Works Association (AWWA) Manual M31 – Distribution System Requirements for Fire Protection. The estimated demands for the proposed development are listed as follows:
Mr. Charles Walsh (2) April 17, 2017
Average Daily Demand (ADD) = 112.4 gpm Maximum Day Demand (MDD) = 224.8 gpm (multiplier of 2.0 to ADD) Peak Hour (PH) = 326.0 gpm (multiplier of 2.9 to ADD) AWWA Manual M32 – Distribution Network Analysis for Water Utilities was used as a guideline in performing the hydraulic analysis. This document states that the MDD should be afforded through the system’s source capacity, not distribution storage. Distribution storage should provide the additional peak hour demands and fire flow. This document also indicates that the fire flow at any given point in the system would be the rate of flow of water obtainable at a minimum residual pressure of 20 psi. Furthermore, this document states that all points in the distribution system also maintain a minimum residual pressure of 20 psi during fire flow conditions. The Smithfield Town Ordinance is consistent with the AWWA M32 standards and states that the minimum residual pressure at any point in the water distribution system during fire flow conditions shall be 20 psi. According to AWWA M32, a water system should have the capability of meeting system demands with system operations consisting of removing from service one active pump in each pump station, preferably the largest active pump. All remaining pumps within the pump stations may be active as required. The water level in the storage tanks for the fire flow evaluation should be at an elevation that represents the bottom water level of equalization storage, less the volume of the NFF rate over the required duration. Insurance Services Office (ISO) also recommends that the NFF be superimposed upon the average demand of the maximum day. Therefore, the MDD scenario for the system was used when evaluating fire flow for the proposed development. Because the NFF was not provided, the fire flow analysis did not include a reduction of the NFF volume from system storage when calculating the AFF. Hydraulic Evaluation To simulate the proposed development, the ADD, MDD, and PH demands were imposed on junction nodes J-1863 through J-1880 for the proposed mixed-use plan. The demand was allocated evenly across these junctions. Model simulations indicated that the SWSB has the capability of providing adequate domestic pressures under the various demand scenarios (i.e., average day through peak hour flows). Pressure at the proposed development ranged from 61 to 77 psi for the ADD, MDD, and PH demand scenarios (reference Attachment No. 3 – Hydraulic Model Simulation Results). However, while adequate pressure could be supplied at these nodes for all demand scenarios, the system’s supply source was unable to provide for the MDD demand scenario without draining the distribution storage, which is incompatible with AWWA M32 source capacity guidelines. To simulate fire flow conditions, the system was evaluated with the water level in the 1 million gallon (MG) Rocky Hill Tank and 4 MG Island Woods Tank lowered to the bottom of equalization storage. The overflow elevation of both these tanks is approximately 521.00 and the bottom of equalization is at 514.00 for each tank. Hydraulic model results indicated that during a fire event the AFF at the proposed development ranged from approximately 4,500 gpm to over 5,000 gpm.
Mr. Charles Walsh (3) April 17, 2017
Summary It appears as though the SWSB can supply adequate domestic pressure to the proposed development. Domestic pressure during ADD, MDD, and PH demand scenarios ranges from approximately 62 to 73 psi. Moreover, the model results indicate that the existing system can provide a range of AFF of approximately 4,500 to over 5,000 gpm at the proposed development while maintaining a minimum residual pressure of 20 psi. However, the system’s supply source is unable to accommodate the proposed development without utilizing distribution storage on a MDD. It should be noted that water supply in the SWSB is becoming an increasingly critical issue. In general, demand in the SWSB is approaching 80 to 85 percent of the system’s total supply capacity (approximately 2 MGD). As indicated above, the existing pumps were unable to provide the MDD to the system with the additional development. Currently, SWSB is evaluating a number of concepts that could increase the system’s total supply capacity. One such concept is to transfer a portion of Providence Water’s 16-inch Ridge Road Tank supply line to the SWSB and having Providence Water acquire the SWSB’s 12-inch transmission main and the portion of the SWSB system located in North Providence, RI. This section of North Providence would be served by the Providence Water’s Ridge Road Tank in lieu of the SWSB’s Longview Reservoir Pump Station, which would reduce the demand on this pump station and free-up supply for future demand. In addition, the SWSB is considering an interconnection with the Lincoln Water Commission on George Washington Highway (Rt. 116). It is possible that either of these proposals could provide adequate supply to meet the demands of this and other future developments; however, these proposals are in the early concept phase and need further study and evaluation to identify the exact volume of water they could provide. If you have any questions or concerns, please don’t hesitate to contact me at your convenience at (401) 334-4100. Sincerely,
Timothy P. Thies, P.E. Vice President TPT/SPD/abv Enclosures cc: George G. Palmisciano, P.E. – Pare Corporation Z:\JOBS\03 Jobs\03066.48 SWSB Hyd Eval - Village at Stillwater\REPORTS\Village at Stillwater Hydraulic Evaluation.doc
ATTACHMENT NO. 1
PARTIAL NODE AND PIPELINE PLAN
ATTACHMENT NO. 2
HYDRAULIC MODEL EVALUATION CALCULATIONS
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9.0 Utilities Analysis The proposed development is to be serviced by public sewer with two connections approximately coordinating with the proposed roadway connections in Douglas Pike and George Washington Highway. The development is proposed to be serviced by public water with a looped system running through the site from a connection point to the existing water mains in Douglas Pike and George Washington Highway. DiPrete Engineering has coordinated with the Town of Smithfield Town Engineer and it is our understanding that additional flow modeling for both sewer and water will be performed by the Town’s consultant after the submission of the Master Plan materials. After a detailed engineered plan has been designed, site plans will be submitted to the Town of Smithfield for review. Anticipated project sewer and water flows, broken into flow to each connection point, are shown below:
Building # Floor Use Footprint (sf)GROSS Floor
Area (SF)
Sewer
Demand
(GPD)
Avg Water
Demand (GPD)
Peak Water
Demand (GPD)
1 1 Retail 10,500 10,500 525 525 2,100
1 Retail 350 350 1,400
2 Office (small) 525 525 2,100
1 Assisted Living (24) 3,600 3,600 14,400
2 Assisted Living (24) 3,600 3,600 14,400
3 Assisted Living (24) 3,600 3,600 14,400
4 1 Retail 10,000 10,000 500 500 2,000
5 1 Retail 8,000 8,000 400 400 1,600
6 Single Family Detached Condos (39) 2,000 109,200 12,870 12,870 51,480
