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City of Morgan Hill
Sanitary Sewer Flow Monitoring and Inflow/Infiltration Study
12-0248 AEG CofMorganHill FM Rpt.docx
Page 4 of 46
Basin Inflow and Infiltration Analysis Results
Due to potential cross-connections between basins, the I/I results for Basins 7 and 8 are shown
together, labelled “Basin 7/8”. The individual results for Basin 7 and 8 are presented as sub-headers
and for informational purposes only to be used at the reader’s discretion.
Table 2 summarizes the flow monitoring and I/I results for the nine flow monitoring basins that were
isolated during this study. Infiltration and inflow rankings are shown such that 1 represents the highest
infiltration or inflow contribution and 9 represents the least. Basins that ranked 1, 2 or 3 in a category
are color coded red. Please refer to the
I/I Methods
section for more information on inflow and
infiltration analysis methods and ranking methods.
Table 2. I/I Analysis Summary
Metering
Basin
ADWF
(mgd)
Peak I/I
Rate
(mgd)
Combined I/I
(gallons)
Inflow
Ranking
RDI
Ranking
Evidence
of High
GWI?
Combined
I/I
Ranking
Basin 1
0.19
0.23
56,400
7
4
No
7
Basin 2
0.17
0.13
47,200
9
T7
No
8
Basin 3
0.18
0.46
166,200
1
3
No
1
Basin 4
0.21
0.41
114,100
2
5
No
4
Basin 5
0.27
0.18
90,900
6
2
No
5
Basin 6
0.35
0.57
136,300
5
T7
Yes
6
Basin 7/8
0.40
0.67
230,300
3
T7
No
2
Basin 7
0.24
0.57
177,700
No
Basin 8
0.16
0.21
52,000
No
Basin 9
0.13
0.34
133,300
4
1
No
3
Basin 10
0.12
0.11
16,400
8
6
No
9
System
2.65
2.97
1,135,500
The following inflow/infiltration analysis results are noted:
Inflow:
Basins 3, 4, 7/8 and 9 ranked highest for normalized inflow contribution.
♦ If isolated, Basin 7 ranks highly within the Basin 7/8 basin and highly within the collection
system.
Rainfall-Dependent Infiltration:
Basins 3, 5 and 9 ranked highest for normalized RDI
contribution.
Groundwater Infiltration:
Basin 6 had GWI rates that were
above
the WEF typical low-to-
average ratio, indicating excessive groundwater infiltration.
Combined I/I:
Basins 3, 7/8, 9 and 4 ranked highest for normalized combined I/I contribution.
♦ If isolated, Basin 7 ranks highly within the Basin 7/8 basin and highly within the collection
system.