Innovative I/I Analysis Leads to Sustainably Program

Transcription

1 Innovative I/I Analysis Leads to Sustainably Program Heart of the Valley Metropolitan Sewerage District Kaukauna, Wisconsin Mark Surwillo, HOVMSD District Manager Tammy Kuehlmann, PE, Donohue & Associates Project Manager

2 Background HOVMSD v Serves five communities along the Fox River v WWTP landlocked v Facility plan developed in 2003 identified capacity limitations for plant and interceptor v Aggressive 30% peak I/I reduction for the 100-year storm with 10 years v WDNR mandated

3 Community Challenge Older communities and sanitary infrastructure High groundwater / perched groundwater Nearly every house has a basement with a foundation drain

4 Interceptor Challenge Portions lie in and along the Fox River Extremely susceptible to I/I Difficult to access Modifications cost prohibitive

5 By 2009 Communities spent $15 million on I/I projects Estimated $40 to $80 million more was needed to reach the 30% mandate 10x the original 2004 estimate A NEW APPROACH WAS URGENTLY NEEDED

6 Approach Antecedent moisture modeling (AMM) v Gauge the effectiveness of projects v Identify and prioritize future projects Frequency Analysis v AMM and hydraulic modeling v Predict future system performance v Risk assessment tool

7 Approach First time a Wisconsin entity of this size used risk assessment as a basis for facility plan amendment approval Communication with WDNR Frequent and Reciprocal

8 Antecedent Moisture Modeling AMM models response to wet weather in each community Uses rainfall, temperature, and flow as inputs 2 years of pre-project rainfall and flow data developed baseline wet weather response Compare current flows to simulated flow for performance evaluation

9 AMM Conventional Modeling Based on single event Very conservative high construction cost Starts with empty system Wet weather response directly proportional to rainfall Facility sizing based on linear extrapolation of model results Antecedent Moisture Modeling Based on long-term simulation Less conservative lower construction cost Simulates effect of back-to-back rainfall events Wet weather response a function of soil moisture conditions Facility sizing readily determined from long-term frequency analysis

10 AMM Results Based on modeling, HOV and communities had removed 7% of the peak I/I flow by 2010 BUT - WWTP wasn t having overflows even during construction

11 Frequency Analysis Risk Assessment Ran the AMM model backwards Based on 54 years of rainfall data Annual peak flows were extracted from long-term simulations Statistical analyses determined recurrence intervals and likelihood of discharges (overflows)

12 Frequency Evaluation Community Hydrographs (AMM) Historic Rainfall Data (54 years) Historic Temperature Data (54 years) Interceptor Model (Dynamic)

13 Overflow Risk at WWTP Interceptor has sealed / bolted manhole lids. No interceptor overflows Return period for exceeding 60 MDG (years) Year Local System Limiting (Existing) Unrestricted Flow (3%) 25 (4%) (2%) 40 (2.5%)

14 Overflow Risk for Communities Return period for surcharging into member community meter stations (years) Community 2008 Conditions 2011 Conditions Kaukauna 19/15 19/19 Little Chute 18/29 29/>54 Kimberly Combined Locks Darboy 15 15

15 Overflow Risk for Communities Impact of surcharge was further evaluated (basement backups were considered failure) Dynamic modeling extended to community system Community Local Sewer Surcharge Comment Kaukauna yes Local sewers will back up before interceptor surcharge Little Chute no Protected by local elevation differences Kimberly Combined Locks Yes south No north No South- local sewers will back up before interceptor surcharge. North - protected by elevation difference Protected by local elevation differences Darboy No Protected by local elevation differences

16 Financial Analysis 2004 cost estimate v 30% peak flow reduction v Est $7.6 million 2006 Sanitary Sewer Evaluation Study estimate v $20.5 million 2011 revised estimate v actual (7%) reduction $14.8 million v estimate $12.8 million (EQ basins)

17 Sustainability Program Capacity, Management, Operation, and Maintenance (CMOM) Program v HOV defined program goals v Uses WDNR outline for CMOM development Annual reporting to HOV v Based on Community Maintenance Annual Report (CMAR)

18 Sustainability Program Flow monitoring and analysis v I/I trends over time v Long-term flow frequency analysis v Overflow Enforcement and Self-Regulation by HOV v Ordinance Revisions v Special orders for non-compliance

19 Result Facility Plan Amendment approved by WDNR Sustainability program used to control I/I Regulatory oversight was reassigned from WDNR to HOV Program completed 2 years ahead of schedule HOV and member communities realized $40 to $80 million in savings

20 WDNR Reaction This modeling approach may potentially help communities to better define the scope of sanitary sewer rehabilitation efforts and ultimately minimize the associated project costs and potential for sanitary sewer overflow occurrences. Stephen Smith, PE WDNR Wastewater Section Bureau of Water Quality

21 Community Reaction We were planning to spend an additional $1.9M in the next 2 years to meet our I/I goal. As a community of 3,400 residents, we would have had to borrow this money. This loan would have consumed our entire budget for sanitary rehabilitation projects for the next 15 years. Now, our $200,000 annual infrastructure budget funded by user charges meets the CMOM program requirements. Sean Hutchison, Administrator Village of Combined Locks

22 Questions