Capacity Assessment Models: Engineering and Operational Uses

Transcription

1 Capacity Assessment Models: Engineering and Operational Uses April 16, 2013 Chip Smith, PE Woolpert, Charlotte NC David Powell, PhD, PE Woolpert, Chesapeake VA Special Thanks to City of Hampton Public Works

2 Presentation Outline q Development of the Capacity Assessment Model Ø Why Required by a Regional Consent Order for SSOs Ø How Overview of the development of the Model q Other Uses for the Model were created Ø System capacity for new development Ø Investigating potential rehabilitation issues Ø Operations and Maintenance Identifying 2 nd Tier Cleaning Locations

3 DISCLAIMER: Although the information contained herein is believed to be reliable, no warranty, expressed or implied, is made regarding the accuracy, adequacy, completeness, legality, reliability, or usefulness of any information, either isolated or in the aggregate, unless expressly specified. Neither is this information intended as a substitute for applicant s obligation to retain its own professional advice from an engineer, surveyor, attorney, or the like.

4 Chesapea ke Bay City of Hampton Overview Atlantic Ocean

5 Regional System Includes > 500 Miles of Interceptors and 82 Regional Pump Stations

6 City Hampton Sewer Collection System q Wastewater Operations Division Ø 104 sewage pump stations Ø 11,055 manholes Ø 477 miles of sanitary sewer piping Ø 136 square miles of coverage Ø 46,054 customer accounts Founded in 1613 Ø Collects/transports ~ 8.5 MGD to HRSD on dry days Ø 70 MGD wet weather peak

7 Hampton s Capacity Assessment Model q Regional Consent Order Requirements Ø Baseline Dry Weather Flows Ø 2, 5, 10 -Year Peak Flow Recurrence Ø Current System Configuration Ø Current Conditions with 2030 Population Ø Identify Locations of Simulated SSOs Ø Identify Surcharged MHs < 1.5 feet Below Rim q Hampton wanted an all pipes model Ø 73% of system is > 50 years old Ø In-fill development is an issue

8 Capacity Assessment Challenges q 35 PS s connected to HRSD Force Mains Ø Subject to varying HRSD pressures q 300+ City Gravity connections to HRSD Gravity Mains Ø Subject to HRSD surcharging q Capacity Assessment Divided into Phases Ø Simulated overflows checked by free discharge runs Ø PS s analyzed at Policy Head Design Condition Ø PS s analyzed at Actual Head HRSD Model

9 Capacity Assessment Results 11,000 Structures in System q Results for Dry Weather Flow Conditions Ø 48 structures exceeded 1.5 foot free board criteria q Results for 2-yr Rain Peak Flow Event Ø 72 structures q Results for 5-yr Rain Peak Flow Event Ø 162 structures q Results for 10-yr Rain Peak Flow Event Ø 419 structures

10 Engineering and Operational Uses q Models are typically the realm of the Engineering department Capital Improvement & Master Planning q Additional uses/scenarios increase value Ø System capacity for new development Ø Investigating potential rehabilitation issues Ø Operations and Maintenance Identifying 2 nd Tier Cleaning Locations

11 Area of Studies L NT L E I F M IN- ELOP DEV N 1,000 ft

12 New Development q Infill development q Low area, upstream of low point

13 New Development q Determine if city infrastructure has capacity restriction Ø Regional conveyance system has current limitation, but ongoing plans already include fully developed flows q Developed flow parameters for the areas Ø Base sewage flow per residential unit Ø RDII flow used adjacent area s wet weather parameters q Run the 10-year Peak Flow Event worst case scenario Ø Free Discharge conditions Ø Downstream tailwater conditions from RHM

14 New Development q Examined HGL, dimensionless parameter Ratio of 10-yr Peak Q to Mannings Q Undeveloped 0.86 Developed 0.89 q No city capacity restrictions limitation is downstream in regional system q Time savings and verification of institutional knowledge

15 Investigating Potential Issues q 2,600 LF of CIPP lining in low-lying area Ø Sand buildup in pipe Ø Suspected leaky joints q Starred location is known low point q Highlighted section was to be lined

16 Investigating Potential Issues q Determine impact of reduced pipe diameter on water levels at low manhole during peak event q Subject to surcharging from the downstream interceptor q Multiple influences make this a sensitive location

17 Investigating Potential Issues q Lining does not increase HGL significantly q Larger problem is downstream capacity

18 Operations and Maintenance Identifying 2 nd Tier Cleaning Locations q Hampton O&M staff has a high frequency Hot Spot cleaning program 1 st Tier Cleaning Locations q Just now started using model results to identify areas with minimal velocity that result in sedimentation build up q Quickly identify the location and impact of reverse grade pipes (seen on previous slide) not on Hot Spot list q Model results will be compared with FOG program and Food Services Establishments to better prioritize cleaning program

19 In Summary q Models are not limited to Capital Improvement and Master Planning q Models can have a significant role in evaluating rehabilitation alternatives q Models are capable of supporting operations staff to improve system performance efficiently Ø Still working on getting it to make coffee

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