Below is quick summary of the pumping capabilities of each alternative:

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Stella Gregory
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1 Memorandum June 8, 17 To: From: cc: Re: Michael Bumbaco, City of Virginia Beach Scott Morrow, Hazen and Sawyer Emiliee Auyang-Jessen, City of Virginia Beach Mark Jones, City of Virginia Beach North Sherwood Lake Pump Station Preliminary Concept Alternatives Please find attached the three alternatives for the permanent and temporary pumping solutions at North Sherwood Lake. For all alternatives, the 12 temporary trailer mounted pump is shown connecting to an above ground suction and discharge flanged elbow. The suction line extends into the proposed permanent wet well with it s own bay within the wet well structure. The discharge line extends to back of property and heads south towards asphalt path of development. The permanent pump solutions within the wet well will have their discharge piping connect to the shared discharge force main. The A and B alternatives for each layout show the permanent discharge piping/valves in a valve vault (A) or above ground (B). This configuration will be an option based on preference of Operations and site layout constraints. All layouts will have the same 36 RCP influent line from the lake to the wet well. Below is quick summary of the pumping capabilities of each alternative: Alternative 1: (2) 25 hp submersible pumps ( Flygt NP 3171 LT utilized as basis of design) 1 pump operation: o 5 cfs operating point with temporary pump operating simultaneously o 8 cfs operating point without temporary pump 12 temporary pump can achieve 13 cfs maximum operating point with and without permanent pumps operating. A throttling valve will be required on the discharge of the temporary pump to ensure pump is operating on pump curve. Maximum combined pumping capacity of 18 cfs with temporary pump operating. 18 discharge force main 25 x 35 fenced in concrete slab area Alternative 2: (3) 25 hp submersible pumps ( Flygt NP 3171 LT utilized as basis of design - same as alternative 1 pump) 2 pump operation: o 6.5 cfs operating point with temporary pump operating simultaneously o 11.5 cfs operating point without temporary pump 12 temporary pump can achieve 13 cfs maximum operating point with and without permanent pumps operating. A throttling valve will be required on the discharge of the temporary pump to ensure pump is operating on pump curve. Hazen and Sawyer 2809 S. Lynnhaven Road, Suite 350 Virginia Beach, VA

2 June 8, 17 Maximum combined pumping capacity of 19.5 cfs with temporary pump operating. 18 discharge force main 25 x 35 fenced in concrete slab area Alternative 3: (3) 35 hp submersible pumps (12 Flygt NP 32 LT utilized as basis of design) 2 pump operation: o 18.3 cfs operating point without temp pump o 13.5 cfs operating point with temp pump 1 pump operation: o 12.0 cfs operating point without temp pump o 9.5 cfs operating point with temp pump 12 temporary pump would only be utilized in event of an emergency. The permanent pumps with 2 in operation can provide the required 18 cfs maximum capacity of the station. Maximum combined pumping capacity of 26.5 cfs with 2 pumps and temporary pump operating. discharge force main 30 x 40 fenced in concrete slab area Please do not hesitate to contact me with any questions or concerns regarding the project and the attached preliminary pump station concept alternatives. North Sherwood Lake Pump Station Preliminary Concept Alternatives Page 2

3 ALTERNATIVE 3 30' " DI FM SHADOW BO 40' File = O:\315-HRD\315 - PWCN C\315-03C - Sherwood Lake\CAD-BIM\MISC\FIGURES\17-06\Figure 1 - Pump Layout-REV Saved by smorrow Save date = 6/16/17 :19 AM WET WELL (15'x18') W/ (3) 35 HP SUBMERSIBLE PUM (18 CFS W/ 2 PUM) EPANSION REPLACE E INLETS SCALE: 1" = ' 0 '

4 ALTERNATIVE 2 25' 18" DI FM SHADOW BO 35' File = O:\315-HRD\315 - PWCN C\315-03C - Sherwood Lake\CAD-BIM\MISC\FIGURES\17-06\Figure 1 - Pump Layout-REV Saved by smorrow Save date = 6/16/17 :19 AM WET WELL (12.5'x15.0') W/ (3) 25 HP SUBMERSIBLE PUM (12 CFS W/ 2 PUM) EPANSION REPLACE E INLETS SCALE: 1" = ' 0 '

5 ALTERNATIVE 1 25' 18" DI FM SHADOW BO 35' File = O:\315-HRD\315 - PWCN C\315-03C - Sherwood Lake\CAD-BIM\MISC\FIGURES\17-06\Figure 1 - Pump Layout-REV Saved by smorrow Save date = 6/16/17 : AM WET WELL (11.5'x12.5') W/ (2) 25 HP SUBMERSIBLE PUM (5 CFS) EPANSION REPLACE E INLETS SCALE: 1" = ' 0 '

Flygt N-Pumps 3085, 3102 & 3127

Flygt N-Pumps 3085, 3102 & 3127 For reliable and efficient wastewater handling The ConCepT Flygt N-Pump series Reduced pumping efficiency, high energy and maintenance costs shouldn t be a fact of life