Separating Inflow Reduction and Infiltration Removal Frederick Bloetscher, PhD, PE Florida Atlantic University

Outline Sewer Design Concepts What is Infiltration/Inflow Inflow Solutions Effectiveness

Design Considerations Gravity sewers flow downhill Designed to flow ½ full Designed for maximum hourly flow (MHF) Industrial or domestic Infiltration/Inflow increases the flow volume Location of groundwater table relevant

Sanitary Pipe Materials Small lines: PVC Vitrified clay Asbestos cement Larger lines: Ductile iron Concrete

Types of Manholes? Doghouse Precast Drop Brick

Age and Water = Infiltration and inflow

Sewer Higher than Water Sales?

Flows Get Worse with Time

Infiltration/Inflow (I/I) Groundwater that enters the sewer through defective pipes, joints, connections, & manholes Inflow Stormwater discharged directly into sewers from roof drains and stormwater runoff Both overloads collection systems & reduces treatment efficiency Function of age I/I = 0.009 – 0.9 m3/d∙mm∙km (typically)

System Hydrograph RAINFALL TOTAL PLANT FLOW (INCHES) (MGD) 16 12 8 4 OCTOBER, 1991 NOVEMBER, 1991 80 60 TOTAL PLANT FLOW (MGD) Dry weather total flow at WWTP 37.7 MGD 100% Dry weather infiltration 15.2 MGD 40% Wastewater flow 22.5 MGD 60% Excessive I/I increases the amount of flow to be treated at Hollywood's Regional Wastewater Treatment Plant 40 20 OCTOBER, 1991 NOVEMBER, 1991

Inflow= Rain Flow Data vs. Rainfall Rainfall During rainevent INTRODUCTION

I/I Allowance (EPA) From Table 3 EPA Infiltration Allowance   From Table 3 EPA Infiltration Allowance Allowance Range (gpd/in-mile) Sewage Footage (ft) 2,000-3,000 > 100,000 3,000-5,000 50,000-100,000 5,000-8,000 1,000-50,000

Sewer Flows v. Rainfall We can see …..INFLOW!!!

Inflow =>Sanitary Sewer Overflow STORMWATER CONNECTIONS ALLOW INFLOW SANITARY SEWERS OVERFLOW TO WATERWAYS WATERWAY FOOTING DRAIN SANITARY SEWER STORMWATER SUMP PUMP HOUSE (LATERAL) DOWN- SPOUT STREET INLET INFILTRATION BASEMENT BACKUP

Sanitary Sewer Overflow

Inflow Sewer flow peaks during rain events. The size of the storm event matters. A larger storm event will create more inflow. During storm events, wastewater flow is linearly related to rainfall. Based on an analysis of flow vs. rainfall graphs from pre and post construction activities inflow reduction will be calculated.

Inflow

Inflow

Inflow INFLOW

BASEFLOW + INFILTRATION Inflow INFLOW BASEFLOW + INFILTRATION

Inflow INFLOW

Inspect Manholes

Protocol – Seal Manhole Frame/Cone Connection Infiltration Rain or Shine Water Table Protocol – Seal Manhole Frame/Cone Connection Inflow Cover / Frame Frame / Chimney    

Sealing the Manholes Plus Correct Dish!!! 25

Smoke the System - Finding it?

LDL Plugs for Cleanouts

Midnight Run flow. 2 inch wide flow, 1/4 in deep at 2 ft/s = 0.77917 gpm   flow. 3 inch wide flow, 1/2 in deep at 2 ft/s = 2.3375 flow. 4 inch wide flow, .75 in deep at 2 ft/s = 4.675 flow. 6 inch wide flow, 1.25 in deep at 2 ft/s = 28.05 flow. 8 inch wide flow, 4 in deep at 2 ft/s = 49.8667

Report MH 1-11 MH 1-12 3 2 MH 1-15 MH 1-3 4 MH 1-30 MH 1-40 0.5 2.5 MH 1-31 MH 1-32 0.35 MH 1-4 MH 1-13 5 30 upstream 8 150 LS FM? MH 1-42 35 MH 1-43 MH 1-5 MH 1-6 6 40 MH 1-7 MH 161 lateral

Map = note only 20% of pipe will be investigated – avoided cost

LS 52 – Cooper City

LS 53 Cooper City

LS 54 Cooper City

Dania – System

Savings for Inflow Removal   Community % Change (Pre Vs. Post) Dania Beach (2006 vs. 2009) -31.9% Cooper City (2011 vs. 2013) -62.8%

Next Phase Once Stormwater inflow is out…. Pipelines…

Groundwater

Groundwater vs Base+Infiltration

Base + Infiltration increases with time

Infiltration After removing inflow, the remaining flow is in terms of baseflow + infiltration. Assuming the any increases in baseflow are neglieable, any decreases or increases in flow are related to fluctuations in infiltration. Based on an analysis of baseflow + infiltration vs. groundwater elevations graphs from pre and post construction activities infiltration reduction will be calculated. Separate baseflow + infiltration based on water use , dry days and day of the week

Infiltration

Infiltration

Infiltration

Infiltration

Infiltration A comparison of slopes developed the following findings: 2006 Slope 2009 Slope Total % Change % Change/Year 0.4147x 0.5558x 25.4% 8.5% In total Dania Beach experienced a 25.4% increase in infiltration between 2006 and 2009. Based on the findings above it is assumed that without any improvements utilities can expect approximately an 8.5% increase in infiltration per year.

Infiltration Initial remediation activities of the wastewater collection system were initiated in 2008. Initial activities included non-construction activities such as smoke testing and rehabilitation activities such as sealing manhole covers and adding manhole dishes to existing manholes. These initial activities were completed to reduce inflow into the system. In order to compare inflow following pre and post construction, flow values between 2006 and 2009 were compared. 2006 flow values represent pre-construction flows and 2009 flow values represent post- construction flows.

Infiltration Correction Work to reduce infiltration within the sewer collection system was initiated in 2013. Activities included CCTV analysis of the system and lining pipes in areas where broken or cracked pipes were observed. These initial activities were completed to reduce infiltration into the system. In order to compare infiltration following pre and post-construction, flow values between 2012 and 2013 were compared. 2012 flow values represent pre-construction flows and 2013 flow values represent post-construction flows.

Broken Pipe = Infiltration…   Broken Pipe

Leaky Pipe

Pipeline Leak Repair

Infiltration Calculations A comparison of slopes developed the following findings: 2012 Slope 2013 Slope Total % Change % Change/Year 0.4697x 0.4604x -2.0% -10.5% In total Dania Beach experienced a 2.0% decrease in infiltration between 2012 and 2013. Based on the findings above only a small drop in infiltration was experienced..

RESULTS In order to accurately estimate the percent change we must also take into account the amount of inflow and infiltration which would have increased if no work would have been completed. Baseline increase in inflow was calculated to be 14.1% per year. Baseline increase in infiltration was calculated to be 8.5% per year. Percent Change Total Net Change Inflow -54.8% -68.9% Infiltration -2.0% -10.5%

Results A significant decrease in inflow between the pre and post- construction flows was experienced. The construction activities resulted in a total net inflow decrease of 68.9%. The pre and post construction activities resulted in a significantly less percent decrease in infiltration. Two things to note however, are: The percent decrease in infiltration still accounts for a larger total flow decrease than the inflow decrease because infiltration is such a larger portion of the yearly total flow. The infiltration percent decrease was marginalized due to the fact that baseflow was left in the calculations. Without an adequate way exclude to baseflow, flow measurements were left in baseflow + infiltration. Leaving the baseflow in the analysis does not affect the amount of the flow reduced from the infiltration reduction work but it would decrease the percent change. Even though the percent change is minimalized due to the additional flow within the calculation, it will not affect the cost analysis, which will be based on the amount of flow reduced and not the percent change.

Cost Analysis The inflow calculations generated previously, based on the rainfall and flow, were used to calculate the cost savings from the inflow construction activities. Using the equation created to show the relationship between the 2006 flow and rainfall and the 2009 rainfall values, the amount of inflow that would have been generated if no construction activities were completed was calculate. 14.1% was added to the 2006 inflow values based on the 2009 rainfall values to account for the amount of increase in the system which would have occurred if no inflow reduction activities would have occurred.

Cost Analysis The baseflow + infiltration calculations generated previously, based on the groundwater elevation and flow minus inflow, were used to calculate the cost savings from the infiltration construction activities. Using the equation created to show the relationship between the 2012 flow minus inflow and groundwater elevation and the 2013 groundwater elevation values, I was able to calculate the amount of infiltration that would have been generated if no construction activities were completed. 8.5% was added to the 2012 baseflow + infiltration values based on the 2013 groundwater elevation values to account for the amount of increase in the system which would have occurred if no infiltration reduction activities would have occurred.

Sewage Reduced (gallons) Cost Analysis Based on information provided by the city of Hollywood, Dania Beach currently pays $2.98/1,000 gallons. Assume 850 Manholes, 60 Miles of pipe Assume 800 MH Inflow Infiltration Sewage Reduced (gallons) 18,348,011 72,706,566 Amount Saved ($55,044) ($216,665) Cost $472,000 $772,000 Cost/1000 gallon $22.72 $7.64 BUT… Avoided Cost ($1,200,000) $0 ($42.68)

Questions