Transmission System Evaluation. For Additional Capacity. In a Coastal Wastewater Collection System

Transcription

1 Transmission System Evaluation For Additional Capacity In a Coastal Wastewater Collection System North Carolina AWWA-WEA 96 th Annual Conference November 14, HDR, Inc., all rights reserved.

2 Project Background System Evaluation Alternatives Evaluation Recommended Alternative

3 PROJECT BACKGROUND

4 BACKGROUND: WASTEWATER SYSTEM CAPACITY EXPANSION GOALS AND OBJECTIVES Southport requested capacity in the West Brunswick Wastewater Collection System o 0.75 MGD o MGD Peaked Identify and recommend the most cost-effective solution to utilize the Brunswick County System o Transmission Main o Wastewater Treatment o Effluent Disposal

5 BACKGROUND: TRANSMISSION SYSTEM BACKGROUND Transmission System is Young o Evaluated system was placed in service in 2006 Manifolded System o 15 Pump Stations Connected to Transmission Main Transmission Main Lengths 86,500 lf (NC 211) 60,000lf (Oak Island FM) Elevations are Relatively Flat Force Main Elevation varies from 0 60 ft MSL

6 BACKGROUND: PROJECT AREA DOT PROJECT AREA

7 SYSTEM EVALUATION

8 SYSTEM EVALUATION: Modeled System o Sewer CAD o Steady State Vs. Dynamic Model All On Only 1 Pump On o Establish Baseline Conditions Sandy Lane (Southport) Pump Station Off o Recorded Operating Characteristics Flow Rates Velocities Pressures Pump Station Operation Status

9 SYSTEM EVALUATION: ALTERNATIVES EVALUATION Develop transmission system improvement alternatives o Meet Established Background Conditions (System minus Sandy Lane Pump Station) o Meet County s Operating Criteria County Operating Condition Criteria o Pressure < 100 psi o Velocities 2 < 5 ft/s

10 SYSTEM EVALUATION: Excerpt from Evaluation Spreadsheet: Existing System Analysis Pump Characteristics Existing System Analysis Pump Station Shutoff Head (ft) Design Condition Flow (gpm) Pump Head (ft) Station St. James Main ft TDH Winding River Main ft TDH Palmetto Creek Supply Stone Chimney Rd ft TDH Mill Creek Cove Southport-Supply Rd ft TDH or Avalon gpm (1) 661 (2) Olde Georgetowne ft TDH Stonebridge St. James # gpm River Sea # gpm /Midway gpm Sandy Lane gpm N/A N/A N/A Rivermist gpm (1) 594 (2) 987 (Both) Seawatch gpm

11 SYSTEM EVALUATION: BASELINE CONDITIONS

12 SYSTEM EVALUATION: EXISTING CONDITIONS

13 ALTERNATIVES EVALUATION

14 TRANSMISSION MAIN ALTERNATIVES 1. Parallel 12-Inch Force Main 2. Parallel 12-Inch with 20-Inch Upsize 3. Re-Pump Stations Along Existing Force Main 4. Re-Pump Stations/Parallel 12 inch FM 5. Connection to Oak Island Force Main

15 PARALLEL LINE EVALUATION 24-INCH LINE

16 PARALLEL LINE EVALUATION 20-INCH LINE

17 PARALLEL LINE EVALUATION 16-INCH LINE

18 PARALLEL LINE EVALUATION 12-INCH LINE

19 PARALLEL LINE EVALUATION BASELINE CONDITIONS

20 ALT 1 PARALLEL FORCE MAIN EVALUATION SUMMARY Evaluated Multiple Force Main Diameters Selected Smallest Diameter that Met Existing Conditions and County Operating Criteria Easements Required Along Entire Route

21 TRANSMISSION MAIN ALTERNATIVES 1. Parallel 12-Inch Line Force Main 2. Parallel 12-Inch with Upsize with 20-Inch Upsize 3. Re-Pump Stations Along Along Existing Force Existing MainFM 4. Re-Pump Re-Pump Stations/Parallel Staton Parallel 12 inch FM FM 5. Connection Connection to to Oak Oak Island Island Force FM Main Parallel 12-in FM Upsize to 20-in FM

22 ALT 2 PARALLEL FORCE MAIN AND UPSIZE FM EVALUATION SUMMARY Evaluated Multiple Force Main Diameters Included Upsizing Existing 16-in Force Main in DOT Project Area in lieu of Parallel Force Main Selected Smallest Diameter that Met Existing Conditions and County Operating Criteria Easements Required for Parallel Force Main

23 TRANSMISSION MAIN ALTERNATIVES 1. Parallel 12-Inch Line Force Main 2. Parallel 12-Inch with Upsize with 20-Inch Upsize 3. Re-Pump Stations Along Along Existing Force Existing MainFM 4. Re-Pump Re-Pump Stations/Parallel Staton Parallel 12 inch FM FM 5. Connection Connection to to Oak Oak Island Island Force FM Main Proposed Re-Pump Station 1 Proposed Re-Pump Station 2 (Would Replace Old Georgetown PS)

24 ALT 3 RE-PUMPING STATIONS EVALUATION SUMMARY First Looked at only adding 1 Re-Pump Station Looked for Existing Pump Stations to Upgrade o Minimize Property/Easement Costs o Minimize Additional O&M Costs o Look at model outputs of increasing pressure conditions Selected 1 New PS Location and 1 PS Upgrade Location Sited PS s in an Attempt to Meet Existing Conditions and County Operating Criteria o No PS site scenarios could meet the evaluation criteria

25 TRANSMISSION MAIN ALTERNATIVES 1. Parallel 12-Inch Line Force Main 2. Parallel 12-Inch with Upsize with 20-Inch Upsize 3. Re-Pump Stations Along Along Existing Force Existing MainFM 4. Re-Pump Re-Pump Stations/Parallel Staton Parallel 12 inch FM FM 5. Connection Connection to to Oak Oak Island Island Force FM Main Parallel 12-in FM Proposed Re-Pump Station 1 Proposed Re-Pump Station 2 (Would Replace Old Georgetown PS)

26 ALT 4 RE-PUMPING STATIONS AND PARALLEL FORCE MAIN EVALUATION SUMMARY Extension of Alternative 3 with Addition of Parallel Force Main to Meet Evaluation Criteria First Looked at only adding 1 Re-Pump Station Looked for Existing Pump Stations to Upgrade o Minimize Property Costs o Minimize Additional O&M Costs Selected 1 New PS Location and 1 PS Upgrade Location Evaluated Multiple Force Main Diameters to Determine Smallest to Meet Evaluation Criteria Sited PS s to Meet Existing Conditions and County Operating Criteria Parallel Force Main Requires Easement

27 TRANSMISSION MAIN ALTERNATIVES 1. Parallel 12-Inch Force Main 2. Parallel 12-Inch with 20-Inch Upsize 3. Re-Pump Stations Along Existing Force Main 4. Re-Pump Stations/Parallel 12 inch FM 5. Connection to Oak Island Force Main Flow Also Routed Through Oak Island FM Parallel 12-in FM Upsize to 20-in FM Connect to Oak Island FM

28 ALT 5 CONNECTION TO OAK ISLAND FORCE MAIN EVALUATION SUMMARY Modeled Existing Oak Island Force Main Modeled Connected Force Mains to Determine Potential Capacity Evaluated Multiple Force Main Diameters in Force Main to Meet Evaluation Criteria o Minimize Additional Force Main o Minimize Easement Costs

29 ALTERNATIVES EVALUATION SUMMARY Alternative Meets Design Pressure Requirement (<100 psi) Highest Pressure Modeled (psi) Meets Velocity Requirements (>2 fps, <5fps) Highest Observed Velocity (fps) Pump Stations where System Pressures Exceed Shut Off Head Cost Estimate Existing No 111 No N/A 1 Yes 99.5 Yes $8,510,000 2 Yes 87.4 Yes $7,740,000 3 Yes 100 No $2,660,000 4 Yes 90 Yes $8,990,000 5 Yes 98.7 Yes $2,850,000

30 RECOMMENDED ALTERNATIVE

31 INFLUENT TRANSMISSION KEY FINDINGS Utilizing available capacity in Oak Island FM reduces easement acquisition and new pipe installation costs Capacity used in Oak Island Force Main matches requested flow from Southport Transmission Alternatives Cost Opinion No Transmission Alternative Cost 1 Parallel 12-Inch FM $ 8.51 M 2 Parallel 12-Inch FM and Upsize in DOT Project Area $ 7.74 M 3 Re-Pump Stations 1 $ 2.65 M 4 Re-Pump Stations and Parallel FM $ 8.99 M 5 Oak Island FM Connection $ 2.85 M 1 Does not meet Brunswick County Minimum Operating Requirements

32 RECOMMENDED TRANSMISSION IMPROVEMENTS Connection Parallel Line to Oak Island Force Main o Upsize Existing 16-in Force Main to 20-in Force Main from St. James to the end of Parallel with Upsize Re-Pump the NC DOT Stations Project Area Along Existing FM o Interconnect Oak Island FM to 12-in Parallel Force Main and Existing FM on NC 211 Re-Pump Staton Parallel FM Connection to Oak Island FM Flow Also Routed Through Oak Island FM Parallel 12-in FM Upsize to 20-in FM Connect to Oak Island FM

33 QUESTIONS Randy Plummer, PE