Collins, Michelle

Michelle Collins was a speaker at the WEFTEC 2024 conference in New Orleans, LA October 5-9, 2024.

Titles from this speaker

Implementation of a Private Lateral Inflow and Infiltration Pilot Study

Abstract

In 2015 and 2016 the City of St. Petersburg, Florida (City) experienced extreme wet weather resulting with unauthorized discharges due to capacity limitations in the sewer collection system, water reclamation facility (WRF) effluent filters, injection wells and impacts from inflow and infiltration (I/I). The City engaged a team of professional engineers to evaluate the wastewater collection system and WRFs to identify the most cost-effective solution to mitigate potential similar overflows during future storm events. The City advanced development of a Wet Weather Overflow Mitigation Program (WWOMP). The WWOMP Phase I Study recommended improvements to the WRFs and I/I removal from the collection system to reduce flows to the WRFs and increase capacity in the sewer network to reduce the likelihood of future overflows. Preliminary recommendations from the WWOMP included an I/I pilot program be performed to assess the effectiveness of various I/I removal approaches to determine which work best for the City. As the WWOMP was being finalized, the City initiated an I/I pilot study in the Maximo Moorings neighborhood within the Southwest WRF (SWWRF) collection system. The initial phases of the Maximo Moorings Pilot Study focused on inspection and rehabilitation of the City’s public infrastructure. Work included lining of gravity mains and the public portion of laterals, defect repair in manholes and sewers, and the installation of manhole inflow dishes. Pre-construction and post-construction flow monitoring was performed to estimate the potential I/I reduction associated with rehabilitation of the public infrastructure. Although data limitations made comprehensive analysis of the Maximo Moorings Study challenging, it was generally concluded that rehabilitation of public infrastructure alone did not achieve the desired I/I reductions. Private sources of I/I are often also significant contributors to wet weather flow. A Water Environment Research Foundation (WERF) Study reported a range of private sector I/I contributions of 7% to 80%, with a mean of 40% based on a survey of 26 utilities (WERF, 2006). The City subsequently implemented a Private Lateral I/I Pilot Study (Pilot Study) expanding inspection and rehabilitation to the private laterals in the Maximo Moorings neighborhood. Because I/I is highly dependent on the characteristics of the targeted collection system, rehabilitation programs focused on removing private sources of I/I often have wide-ranging results. This same variability in I/I from system to system and from basin to basin is expected in St. Petersburg and will be incorporated as the City plans for the future implementation of a City-Wide Private Lateral I/I Program. This paper presents a step-by-step process to successfully implement a private lateral inflow and infiltration pilot study and discusses the preliminary results of the impacts of performing private lateral rehabilitation to mitigate I/I on a coastal community's wastewater collection system.

This paper is intended to present engineers with a step-by-step process that will successfully mitigate wet weather impacts for a coastal community's wastewater collection system through private property inflow and infiltration (I/I) mitigation. The process builds upon work performed within the City of St. Petersburg, Florida (City) to date and incorporates the City’s understanding of its own infrastructure for the implementation of a pilot study focusing on the inspection and rehabilitation of private laterals to further eliminate I/I. The process implemented, lessons learned, and results of the study will guide the next steps for the implementation of a City-wide Private Lateral I/I Program.

SpeakerCollins, Michelle

Presentation time

14:30:00

14:50:00

Session time

13:30:00

15:00:00

SessionFinding and Removing I/I

Session number301

TopicCollection Systems

Author(s)

Michelle Collins

Author(s)M. Collins1; J. Palenchar3; K. Barrera2;

Author affiliation(s)Jacobs Engineering Group, Tampa, FL1City of St. Petersburg, St. Petersburg, FL2,3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158051

Volume / Issue

Content sourceWEFTEC

Word count11

Is Private Lateral Inflow and Infiltration Mitigation Effective?

Abstract

LEARNING OBJECTIVE
This paper presents an overview of the process to mitigate private property inflow and infiltration (I/I) impacts on a coastal community's wastewater collection system through inspection and rehabilitation of private laterals. This paper will present the pilot study results and provide a case-study of localized private laterals rehabilitation methodologies and a cost-benefit analysis of potential private laterals I/I reduction. Flow reduction to the City's public wastewater collection system and to the WRFs resulting from private-side I/I mitigation efforts will be summarized and presented. The process implemented, lessons learned, and results of the study will guide the next steps for the implementation of a city-wide Private Lateral I/I Program.
ABSTRACT BACKGROUND In 2015 and 2016 the City of St. Petersburg, Florida (City) experienced extreme wet weather resulting with unauthorized discharges due to high infiltration/inflow rates and capacity limitations in the sewer collection system, water reclamation facility (WRF) effluent filters, and injection wells. The City engaged a team of professional engineers to evaluate the wastewater collection system and WRFs to identify the most cost-effective solution to mitigate potential similar overflows during future storm events. The City advanced development of a Wet Weather Overflow Mitigation Program (WWOMP). The WWOMP Phase I Study recommended improvements to the WRFs and collection system to reduce the likelihood of future overflows. Collection system improvements were focused on public and private side I/I removals to reduce flows to the WRFs and increase capacity in the sanitary sewer system. The City initiated an I/I pilot study in the Maximo Moorings neighborhood within the Southwest WRF (SWWRF) basin. The initial phases focused on inspection and rehabilitation of the City's public infrastructure. Pre-rehabilitation and post-rehabilitation flow monitoring was performed to estimate the potential I/I reduction associated with rehabilitation of the public infrastructure. Results generally concluded that rehabilitation of public infrastructure alone did not achieve the desired I/I reductions. Private sources of I/I are often also significant contributors to wet weather flow. A Water Environment Research Foundation (WERF) Study reported a range of private sector I/I contributions of 7% to 80%, with a mean of 40% based on a survey of 26 utilities (WERF, 2006). The City subsequently implemented a Private Lateral I/I Pilot Study expanding inspection and rehabilitation to the private laterals in the Maximo Moorings neighborhood. Because I/I is highly dependent on the characteristics of the targeted collection system, rehabilitation programs focused on removing private sources of I/I often have wide-ranging results. This same variability in I/I from system to system and from basin to basin is expected in St. Petersburg and will be incorporated as the City plans for the future implementation of a City-Wide Private Lateral I/I Program.
OBJECTIVES The objectives of the Private Lateral I/I Pilot Study is twofold: (1) to collect data to better understand the I/I reduction associated with rehabilitation/replacement of private laterals in the study areas and (2) to guide the next steps and methods of reducing private sources of I/I throughout the City. METHODOLOGY Two similar neighborhoods were selected for the study in the event of anomalies or deficiencies in the data before and after rehabilitation. A study area and control area were identified and monitored in each neighborhood. In the study areas, defects resulting in I/I were identified and rehabilitated. The control area provided a baseline to compare flows for the same rainfall and groundwater conditions. The City selected the Maximo Moorings and the Greater Pinellas Point study areas due to the following characteristics: - Built between the 1950s and 1970s when the installation of Orangeburg pipe, a bituminized fiber pipe that has a tendency to break, was prevalent. - Located within the SWWRF basin and sit at a similar elevation with most of the gravity sewers below groundwater levels. Both study area's characteristics are representative of a majority of the City's residential neighborhoods. - Significant public infrastructure rehabilitation was performed previously in both neighbourhoods, with roughly 80% of the public gravity sewers recently lined (2016-2018). The project team performed an 8-step process for implementing the study as follows: 1. Pre-rehabilitation flow monitoring 2. Pre-qualification for plumbers 3. Data management procedures 4. Public outreach, pre- and post-Covid 5. Private lateral inspections 6. Rehabilitation 7. Post-rehabilitation monitoring 8. Post Pilot Study survey and lessons learned for citywide private lateral program implementation
RESULTS AND CONCLUSIONS Pre-rehabilitation and post-rehabilitation flow monitoring was performed to collect data on dry weather and wet weather flows generated in the Study Areas. For the pre-rehabilitation condition, the I/I was characterized as a baseline for comparison against post-construction flow data to estimate the effectiveness of private lateral rehabilitation. The control areas account for variation in rain and antecedent moisture conditions between the two monitoring periods and help identify wet weather events during the post-construction flow monitoring period. Rainfall impacts both the antecedent moisture conditions and the sanitary sewer responses (refer to Figure 2). Therefore, rainfall experienced during the pilot study was compared to historical rainfall to show how the pre-rehabilitation and post-rehabilitation rainfall data compared to historic norms and also to each other. In the pre-construction flow monitoring period, excessive levels of rainfall-derived inflow and infiltration (RDII) and groundwater infiltration (GWI) were observed in Greater Pinellas Point. Excessive levels of RDII and high levels of GWI were observed in Maximo Moorings. Figure 3 shows the total volume of rain compared to the portion that enters the sanitary sewer system for each event and incremental metershed for the pre-construction period. The antecedent moisture conditions are indicated by the size of the bubbles based on amount of rainfall that fell during the two weeks prior to the event. Linear regressions, assuming there is no RDII when there is no rain, are fitted to understand the trend for each metershed. Events with less than 1.5 inches of rain show less correlation to the trendlines than events with more than 1.5 inches of rain. These trends will be compared to the post-construction RDII results to understand the effectiveness of private lateral rehabilitation in this area. Post-construction flow monitoring began July 2021 and will continue through December 2021. The following will be summarized and presented: - pre- and post-construction study flows and reductions achieved, - inspection and rehabilitation costs, - cost-effectiveness evaluation, - Pilot Study findings and recommendations, - and lastly, the City's next steps in pursuing system-wide private lateral I/I mitigation.

SpeakerCollins, Michelle

Presentation time

08:55:00

09:20:00

Session time

08:30:00

10:00:00

TopicIntermediate Level, Collection Systems

Author(s)

Collins, Michelle

Author(s)Michelle Collins1; Victoria Berry2; Kira Barrera3; John Palencha4

Author affiliation(s)Jacobs Engineering Group, Tampa, FL1; Jacobs Engineering Group, Cincinnati, OH2; City of St. Petersburg, St. Petersburg, FL3; City of St. Petersburg, St. Petersburg, FL4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158507

Volume / Issue

Content sourceWEFTEC

Word count9

Leveraging Grant Funds to Reduce Private System I/I

Abstract

Pinellas County Utilities (PCU) wastewater collection system is aging and experiences excessive levels of inflow and infiltration (I/I) during wet weather events. These events have caused sanitary sewer overflows (SSO) due to impacts of I/I and resulting capacity limitations in the system and the downstream water reclamation facilities. PCU's South Cross Bayou Water Reclamation Facility (SCBWRF) is permitted at 33 million gallons per day (MGD) and can experience peak flows up to 100 MGD during severe wet weather events such as tropical storms. PCU has identified a significant portion of its I/I originate from the private-side, with significant contributions from manufactured housing communities (MHC). PCU has identified 14 private MHCs within the Lealman, Largo, and Lake Seminole areas whose wastewater systems contribute high or excessive I/I to the County's public wastewater collection system and initiated a program for the replacement of these private systems. PCU views the MHCs wastewater systems holistically as these systems are conveyed to the County's public system. Improving these systems impact multiple elements such as environmental stewardship, operation and maintenance, sustainability, and public health. MHCs are also residences to many fixed and low-income community members. This project addresses an identified need in areas with economically vulnerable populations, as the 4,000 residences associated with the 14 MHCs do not have sufficient cash funds for the significant sewer system improvements. Recognizing that the cost to repair these systems would be a huge burden on residents, the County worked directly with these communities to secure state and federal funding to upgrade each system at no cost to them. While the County will own and maintain the systems permanently, homeowners will still own and maintain the private lateral once the project is complete. Replacement of the wastewater collection systems would eliminate leaking pipes, manholes, and illegal connections from storm and roof drains. Replacing the systems will reduce the likelihood of SSOs and associated impacts leading to higher water quality in the area and nearby water bodies, a contribution to the protection of living coastal and marine resources and their environments, and a more resilient wastewater collection system in an environmentally vulnerable area. As this project requires significant federal and state funding investment, PCU evaluated vulnerabilities of each MHC to sea level rise and flooding impacts due to climate change. Figure 1 presents a location map of each MHC included in the program as well as overall flood risk. Because the MHCs are private systems, PCU cannot utilize Enterprise dollars and must solely use grant dollars to fund the design and construction of the 14 MHC wastewater systems. As presented in Table 1, the County has received various grant funding for this program, with varying associated requirements and schedules, adding an additional tier of complexity. Because the 90 percent opinion of probable construction cost (OPCC) of approximately $80M developed by the engineer came in higher than PCU's original estimate of $25 million, PCU is currently applying for additional grant money. Currently, PCU has the grant funding available to complete the wastewater system construction of 10 MHCs. This paper will provide an overview of the major components and associated challenges of the County's MHC Wastewater System Improvements Program: 1.Social Equity: Rehabilitating/replacing these wastewater systems in underserved communities such as the MHC's promotes and supports equitable participation involving the County's infrastructure investments, thereby maximizing the benefits aspect of social equity. Other social equity considerations include participation, construction sequencing, and communication to address fair treatment and maximize benefits for inclusive outreach aspects. 2.Funding: Implementing a programmatic approach for funding the program solely through grants with no Enterprise investment and, concurrently, how to strategically leverage and obtain additional funding. 3.Grant Administration: Continually meeting the reporting and schedule requirements of all three funding sources outlined in Table 1. 4.System Acquisition Planning: A step by step process on how to target, acquire, and plan for the transfer of infrastructure and associated maintenance of 14 MHC wastewater systems, and concurrently meeting the federal provisions required by the grants. 5.Design: PCU has onboarded a consultant for the design of the 14 MHCs to meet the grant requirements. 6.Bidding and Construction: PCU has considered alternative delivery, CMAR, and design-bid-build for the construction of the 14 MHC wastewater systems in accordance with requirements of the grants. Because of the complexity and tight schedule requirements, the construction schedule has been compressed and will need to consider specific grant reporting requirements, such as Davis Bacon requirements. PCU intends to onboard multiple contractors and organize separate bid packages per County procurement, grant requirements, and funding availability. 7.Public Outreach: PCU developed and implemented a comprehensive and successful public outreach program for buy-in and engagement of the 14 MHCs, which includes over 4,000 residences.

Pinellas County Utilities (PCU) collection system is aging, experiencing excessive levels of wet weather I/I, causing SSOs. PCU found that a significant portion of its I/I originate from areas of manufactured housing communities with predominantly economically vulnerable populations unable to pay for upgrades. Recognizing this, PCU worked directly with these communities to secure state/federal funding to upgrade each system at no cost to them, creating a new model to address these issues.

SpeakerCollins, Michelle

Presentation time

15:30:00

16:00:00

Session time

15:30:00

17:00:00

SessionReducing Wet Weather Flows Using Public and Private I/I Removal Solutions

Session number221

Session locationRoom 346

TopicCollection Systems, Intermediate Level

Author(s)