20070108 Ver 1_More Info Received_20070213

. ~ HAZEN AND SAWYER
Environmental Engineers & Scientists
February 12, 2007
Ms. Cyndi Karoly, Supervisor
401 Oversight/Express Review Permitting Unit
2321 Crabtree Boulevard, Suite 250
Raleigh, North Carolina 27604
Hazen and Sawyer, P.C.
4944 Parkway Plaza Blvd.
Suite 375
Charlotte, NC 28217
704 357-3150
Fax: [phone]
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WETLANDS AND STOR WATE BRANCH
Subject: City of Raleigh- House Creek Sewer
Replacement
DWQ Project # 07-0108
Dear Ms. Karoly,
Mr. Masengill from the City of Raleigh received your January 31, 2007 letter on
February 2, 2007 requesting more information. In turn, Hazen and Sawyer has
reviewed your comments and has arranged for a meeting with Ms. Amy Chatman
to discuss this matter in further detail. Please find below our preliminary answers
to your comments as well as five copies of the additional information that you
requested.
Additional Information as Requested
1. After speaking with Ian McMillian and Amy Chatman, the temporary impacts
of perennial streams were limited to 40 ft. Therefore, Supplemental Sheet for
Item V14 has been modified and the total stream impact in linear feet is 575. The
table of cumulative impacts listed in Section V1 was also modified to match the
575 linear feet total. As a reminder, 340 feet is remove and replacement, 115
feet is new impacts for Phase I, and 120 feet is new impacts for Phase II.
2. Stream crossing Nos. 1 and 10a are non-perpendicular because they are
replacing an existing line that was non-perpendicular. The replacements will
occur in the existing 40ft maintained sewer easement.
3. After speaking with Ian McMillian and Amy Chatman, the widths for the
maintenance corridor for stream impacts have been limited to 40 ft. The City of
Raleigh currently maintains a 20 to 40 ft sewer easement at the indicated
locations. These existing limits are noted on the drawings.
New York, NY • Armonk, NY • Upper Saddle River, NJ • Raleigh, NC • Charlotte, NC • Vienna, VA • Hollywood, FL • Boca Raton, FL • Fort Pierce, FL • Jupiter, FL • Miami, FL • Bogota, D.E. Colombia

DWQ
Page 2 of 2
February 12, 2007
4. Supplement Sheet for Item VI 4 indicates the impacts that are new
(superscripts A-D). This amounts to 115 feet for Phase I and 120 feet for Phase
II. All constructions limits within creek crossing were limited to 40 ft. The new
and larger line size does not require widening of existing easements.
5. Section VIII Mitigation response was entered as "N/A" under the
understanding that this is a replacement pipe in lieu of a new pipeline project.
The buffer table located in Section X has been revised and no longer shows
required mitigation. However, the-square footage for buffer 1 and 2 remains
listed in the table.
These items will be discussed in our scheduled meeting with Ms. Amy Chatman
on February 13, 2007.
Thank you for your time,
Very Truly Yours,
Hazen and Sawyer, P.C.
`a
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Crystal M. Bon .E.
Engineer
cc. Mr. Robert Masengill, City of Raleigh-I?epartment of Public Utilities

FINALIZED TECHNICAL MEMORANDUM
TO: City of Raleigh Public Utilities Department
FROM: Hazen and Sawyer, P.C.
DATE: March 29, 2006
SUBJECT: House Subbasin Dynamic Sewer Modeling
H&S Job. No. 30381
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FER ] `~ 2007
DENR -WATER QUALITY
WETLANDS AND STORMWATER BRANCH
Introduction
The City of Raleigh retained Hazen and Sawyer to collect field data and perform additional
hydraulic modeling to evaluate the capacity of the House Subbasin existing sewer outfall line to
convey current and future wastewater flows. The subbasin is located in southwestern Raleigh,
transversed by both Wade Avenue and the I-440 beltline. The subbasin extends from Crabtree
Valley Mall (Glenwood Avenue) at its furthest downstream point to the North Carolina State
Veterinary Medical Facility (Blue Ridge Road and Hillsborough Street) at its headwaters. The
entire subbasin encompasses approximately 1,791 acres. Figure I illustrates the boundaries of
the House Subbasin.
There is concern that the existing outfall line may
be inadequate to hydraulically convey the
additional flows generated from the planned
phased expansion of both the North Carolina
State Veterinary Medical Facility and the North
Carolina Museum of Art. Furthermore, the City's
Park and Recreation Department is in the
preliminary planning stages to construct a
"greenway" within the existing sewer outfall line
corridor. Consequently, should the outfall line
require upsizing, construction of the proposed
greenway and improvements to the outfall line
should be coordinated to ensure a timely and cost-
effective overall project. With a coordinated work
effort by City Departments and selected
consultants, this will allow all available
information/data to be shared, prevent duplicity in
work effort, and accelerate both the design and
construction schedule.

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This technical memorandum summarizes previous
House Subbasin modeling efforts, and presents
both manhole field survey and temporary flow
monitoring data recently collected within the
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House Subbasin Boundaries

House Subbasin. This collected field data is then utilized to update the previously developed
InfoWorks dynamic sewer model to evaluate the hydraulic capacity of the sewer outfall line. Pipe
size recommendations and associated construction costs are provided to convey the future wet
weather flows.
Previous House Subbasin Modeling
In the spring of 2001, Hazen and Sawyer provided dynamic sewer modeling of the House
Subbasin. Model input data for manhole invert and grade elevations, along with corresponding
pipe diameter sizes, came from the City's GIS. Estimates of population and associated flow
projections were derived from zoning maps and equivalent number of persons per acre from the
City's Public Utilities Department Handbook. Other model assumptions included:
• Dry weather flows were estimated using 100 gpdpc.
• A peaking factor of 2.5 was applied to estimate wet weather flows.
• North Carolina State Veterinary Medical Facility encompassed 350 acres and zoned
"Office and Industrial." Dry weather flow estimated at 315 gpm. Corresponding wet
weather flow estimated at 789 gpm.
• North Carolina Museum of Art encompassed 135 acres and zoned "Office and
Industrial." Dry weather flow estimated at 121 gpm. Corresponding wet weather flow
estimated at 304 gpm.
These assumptions corresponded to a calculated dry and wet weather projected flow of 2.5 and
6.25 mgd, respectively. Flow monitoring conducted in 1998 by ADS Environmental Services
within the House Subbasin recorded an average dry weather flow of 1.04 mgd. However, no
significant rainfall events occurred during this monitoring period to obtain a corresponding wet
weather flow.
Preliminary pipe sizes recommended to convey the projected wet weather flow of 6.25 mgd
included:
• 30-inch diameter from Crabtree Valley Mall to first I-440 Beltline crossing.
• 24-inch diameter from first I-440 Beltline crossing to second I-440 Beltline crossing.
• 15-inch diameter from second I-440 Beltline crossing to North Carolina State Veterinary
Medical Facility.
• 12-inch diameter from second I-440 Beltline crossing to North Carolina Museum of Art.
The trunk sewer paralleling Lake Boone Trail was not evaluated during this timeframe.
Therefore, no preliminary pipe sizes were recommended.
This modeling effort concluded with the recommendation of performing a sewer survey and
conducting flow monitoring within the House Subbasin to determine existing infrastructure
attributes and dry and wet weather flows. Field data collected would either validate or replace
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Dynamic Sewer Modeling

City GIS attributes, whereas recorded flow monitoring data would be utilized to calibrate the
dynamic sewer model. Recommended attributes to be field surveyed include: manhole x and y
coordinates; manhole invert, grade, and rim elevations; and, pipe sizes entering and exiting the
manhole. Three flow monitors were recommended to be installed within the House Subbasin to
record both dry and wet weather flow events. Recommended locations included: near Crabtree
Valley Mall to monitor total House Subbasin flow; near Lake Boone Trail to monitor flow from
the Lake Boone Trail corridor; and near the Wade Avenue crossing to monitor flow from the
North Carolina Museum of Art and the North Carolina State Veterinary Medical Facility.
Manhole Survey
A field survey was initially performed in the summer of 2003 by Dennis Lee Surveyor of
Smithfield, NC to collect existing manhole and pipe attributes within the twelve (I 2) subbasins of
the Crabtree Creek Basin. Information collected included: manhole x and y coordinates;
manhole invert, grade, and rim elevations; and pipe sizes entering and exiting the manhole.
Approximately I ,240 manholes were surveyed. In general, data collected was limited to pipe
diameters 12-inches and greater.
Within the House Subbasin, 72 manholes were initially surveyed. Manholes surveyed extended
from the Crabtree Valley Mall area southward to Palm Court, and from Palm Court westward
along the Lake Boone Trail corridor. Existing sewer lines upstream of Palm Court were generally
less than 12-inches in diameter.
Due to the planned phase expansion of both the North Carolina State Veterinary Medical Facility
and the North Carolina Museum of Art, it was critical to obtain additional field data to adequately
evaluate their gravity sewers hydraulic carrying capacity. As a result, Dennis Lee Surveyor was
retained in August 2005 to perform additional manhole survey services.
Attributes, as previously discussed, were collected on 65 additional manholes extending from
Palm Court to the North Carolina State Veterinary Medical Facility and to the North Carolina
Museum of Art. A spreadsheet summarizing the data collected from both the 2003 and 2005
field survey and a figure illustrating the location of each manhole surveyed within the House
Subbasin are appended to this technical memorandum (Appendix A). Survey data collected was
based on NAD 83 for horizontal and NAVD 29 for vertical.
Temporary Flow Monitoring
Frazier Engineering of Stanley, NC was selected by Hazen and Sawyer to provide temporary flow
monitoring within the House Subbasin. Three flow meters and one tipping bucket rain gauge
was installed. Data was collected for athree-month period between September 8, 2005, and
December 2, 2005, to determine both average dry and wet weather flows, and to estimate
infiltration and inflow (I/I) quantities. Table I summarizes the three flow monitoring sites.
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Dynamic Sewer Modeling

Table I
Flow Monitoring Site Summary
HO-72 12 Downstream of 2"d I-440 Beltline crossing. Accounts
for flow from NC Museum of Art and NC State
Veterinary Medical Facility.
2 HO-39 12 Downstream of Lake Boone Trail. Accounts for flow
along the Lake Boone Trail corridor.
3 HO-9 17 Upstream of Crabtree Valley Avenue. Accounts for
total House Subbasin flow.
During September to October, there were no significant rainfall events (i.e., rainfalls greater than
0. I -inches over a 24-hour period). Consequently, data collected during this timeframe was used
to estimate the average dry weather flows. Table 2 summarizes the average dry weather flow
data at each monitoring site.
Table 2
Average Dry Weather Flow Summary
12 3.82 0.225
2 12 5.06 0.867
3 17 I t .42 1.001
As Table 2 demonstrates, the total average dry weather flow in the House Subbasin is
approximately I mgd; however, the majority of this totalized flow (0.642 mgd) originates from
the sewer main extending along the Lake Boone Trail corridor. The table also illustrates that
approximately 67% of the pipe diameter at Site 3 is utilized during average dry weather flow
conditions.
A significant rainfall event occurred between November 20 through November 22, 2005. During
this event, approximately 3.04-inches of rain fell over a 33-hour period. The recorded peak
intensity was 0.46-inches/hour. Table 3 summarizes the wet weather flow data at each
monitoring site as a result of this singular November rainfall event.
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Table 3
Wet Weather Flow Summary
I 12 6.31 0.594 2.64 180,208
2 12 6,49 1.544 1.78 22,969
3 17 15.30 2.454 2.45 250,427
Table 3 provides a "snap shot" of how the House Subbasin collection system reacts to a
particular wet weather flow event. During this particular event, wet weather peaking factors
ranged from a low of 1.78 at Site 2 to a high of 2.64 at Site 1. Depth of flow within the pipe
increased significantly at each site. Sites I and 2 utilized approximately 53% of the pipe
diameter; whereas, Site 3 utilized 90% of the pipe diameter. Lastly, the table demonstrates that
a total of 453,610 gallons of I/I was estimated to enter the collection system during this particular
rainfall event.
The amount of I/I entering the collection system can be normalized by dividing the incremental I/I
in gallons by the corresponding length of pipe upstream of each flow monitor in inch-diameter
miles. Normalizing allows the data to be compared on an "apples-to-apples" basis by taking into
consideration the pipe length and pipe diameter. The data can then be used to prioritize areas
for further source detection field work such as smoke testing, closed-circuit television inspection,
and manhole inspection. Table 4 summarizes the normalized data from the November 2005
rainfall event.
Table 4
Normalized I/I Summary
I 25.04 153,097 6,1 14
2 15.61 18,223 I , 167
3 22.43 200,342 8,932
As Table 4 illustrates, the majority of the I/I entering the House Subbasin collection system is via
the main sewer outfall extending from Crabtree Valley Avenue to the North Carolina Veterinary
Medical Facility. This is not surprising, as the pipeline was originally constructed within a forested
area and parallel to House Creek. The combination of elevated groundwater conditions and root
intrusion makes this particular pipeline segment very susceptible to groundwater infiltration.
j:\30381:2/ 13/2007 - 5 - House Subbasin
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The House Subbasin Flow Monitoring Report dated December 16, 2005 as prepared by Frazier
Engineering is appended to this technical memorandum (Appendix B).
Wastewater Flow Projections
Prior to performing dynamic sewer modeling, population and associated wastewater flow
projections were estimated. A combination of geocoded water billing and traffic analysis zone
(TAZ) data was utilized to estimate the wastewater flows generated within the House Subbasin.
Water billing demand records for 2004 indicated a maximum month water usage of 0.825 mgd.
Approximately 70% of the water demand occurs along the Lake Boone Trail corridor (0.578
gpd). Water billing records correlate well with the wastewater flow data recently collected
during Fall 2005. As mentioned previously, 0.642 gpd of wastewater was recorded to originate
along this same corridor. TAZ data estimated a 2004 residential population within House
Subbasin of 7, 178. This corresponds to a per capita water consumption of 115 gpdpc. Applying
a conservative sewer return ratio of 0.9, the amount of wastewater generated per capita within
the House Subbasin equates to 103.5 gpm. Wastewater flows were then projected based upon
the TAZ estimates of population. Table 5 summarizes the residential TAZ population, water
demand, and wastewater flow within the House Subbasin for the indicated design year.
Table 5
Residential TAZ Population, Water Demand,
and Wastewater Flow Summary
As discussed previously, recent flow monitoring data indicated an average dry weather flow of
I.0 mgd. The discrepancy between actual and estimated wastewater flows may be attributed to
groundwater infiltration. Therefore, for the purposes of this hydraulic evaluation, the residential
average dry weather flow for the year 2030 is assumed to be I.0 mgd. A peaking factor of 3.0
will be applied to the average dry weather residential flow to estimate the peak residential flow.
This factor is consistent with previous hydraulic modeling studies within the Crabtree Creek
Drainage Basin.
Next, wastewater flows were estimated for the ultimate buildout of the North Carolina State
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Veterinary Medical Facility. A letter report prepared by Affiliated Engineers (dated June 30,
2000) estimated wastewater flows generated for various stages of growth at the North Carolina
State Veterinary Medical Facility. Table 6 summarizes this data.
Table 6
Summary of Wastewater Flow Estimates
for Various Stages of Growth
A recent meeting with North Carolina State University staff members (Alan Daeke, P.E. -
Assistant Director for Utility Services, Tom Hunter, P.E. -Infrastructure Planning, and Ken
Satterwhite, P.E. -Project Manager) on March 2, 2006 validated that the flow estimates provided
in Table 5 were the best available data to date.
Currently, the North Carolina State Veterinary Medical Facility has a total building area of
approximately 500,000 sf. Per Table 6, this corresponds to a projected average and peak
wastewater flow of 0.278 and 0.547 mgd, respectively. Wastewater flow data collected in fall
2005 recorded an average and peak flow of 0.225 and 0.600 mgd, respectively. In summary, the
projected and monitored wastewater flow data compared very favorably. Consequently, it was
decided to use an ultimate buildout peak flow from the North Carolina Veterinary Medical
Facility of I ,000 gpm.
Similarly, correspondence was conducted with the North Carolina Museum of Art to estimate
their projected peak wastewater flow. The North Carolina Museum of Art is currently in the
preliminary design stages for expanding their facility. Stanford White Associates are the
consulting engineers selected to lead this effort. According to discussion with Stanford White
Associates, the projected average and peak flow for the expanded museum is 24,000 and 33,000
gpd. Assuming flows to occur during an 8-hour period and a peak flow factor of 2.0, the average
and peak wastewater flow generated from the expanded museum is estimated at 70 and 140
gpm, respectively.
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Table 7 summarizes the projected average and peak flows for the House Subbasin.
Table 7
Projected Wastewater Flow Summary
Figure 2 schematically depicts the average and peak wastewater flows generated within the
House Subbasin. The illustrated flows will be input into the hydraulic model to size the new
outfall sewer.
Crabtree Creek Interceptor
Total
Avg = 2.214 mgd
Peak = 4.642 mgd
Avg = 0.200 mgd
Peak = 0.600 mgd
Avg = 0.700 mgd
Peak = 2.100 mgd
Lake Boone
Trail Corridor
Avg = 0.100 mgd
Peak = 0.300 mgd
Avg = 0.101 mgd
Peak = 0.202 mgd
NC Museum of Art
NCSU Vet Med Facility
Figure 2
House Subbasin Flow Schematic
Avg = 1.113 mgd
Peak = 1.440 mgd
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Hydraulic Modeling
The InfoWorks dynamic modeling software utilized in the previous House Subbasin modeling
efforts was updated with the recently collected manhole and flow data. A figure illustrating the
existing House Subbasin sewer outfall is appended to this technical memorandum (Appendix C).
The InfoWorks model was used to evaluate the hydraulic capacity of the House Subbasin outfall
sewer to convey current and future wastewater flows. A key assumption in all the modeling
simulations was that the downstream Crabtree Creek Interceptor was flowing full. This resulted
in a starting hydraulic grade line (HGL) elevation of 213.89.
Initially, the existing House Subbasin outfall sewer was modeled to evaluate its existing hydraulic
capacity at current average flows (I.0 mgd) and peak flows (3.0 mgd). The model predicted, that
at average flow conditions, the depth of flow within portions of the outfall sewer was
approximately 35% to 45% of the pipe diameter. At peak flow conditions, portions of the
outfall sewer were surcharged, but not overflowing. The majority of the surcharging occurred at
the extreme downstream reaches of the House Subbasin outfall sewer due to its relatively flat
slopes. Figure 3 illustrates the HGL of the existing House Subbasin outfall sewer at current peak
flow conditions.
The existing House Subbasin outfall sewer was then modeled to evaluate its ability to convey the
future peak flow (4.642 mgd). The model predicted surcharging and overflowing along the entire
outfall sewer line. The surcharging/overflowing was attributed to the high peak flow originating
from the North Carolina State Veterinary Medical Facility which is located at the headwaters of
the House Subbasin. Due to its location, flow from the North Carolina State Veterinary Medical
Facility greatly impacts the HGL of the entire outfall sewer and, hence, sizing of the future House
Subbasin outfall sewer pipe diameters. Figure 4 illustrates the HGL of the existing House
Subbasin outfall sewer at future peak flow conditions.
Model simulations were then performed to evaluate the conveyance of future peak flows by
upsizing the pipe diameter of the House Subbasin outfall sewer. Two flow scenarios were
modeled. The first flow scenario modeled limited the depth of flow in the outfall sewer to no
greater than 50% at peak flow per the City's sewer design standards. The second flow scenario
modeled relaxed this requirement and allowed the depth of flow to increase from 50% to 75%
of the pipe diameter at peak flow.
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Table 8 summarizes the results of the two flow scenarios modeled and compares the proposed
pipe sizes to the existing pipe sizes.
Table 8
Comparison of Existing and Proposed Pipe Sizes
As Table 8 illustrates, the proposed pipe diameter (for either flow scenario) is required to be
significantly larger than the existing in order to convey the future peak flow. If the depth of flow
in the proposed pipe can be increased from 50% to 75% at peak flow, then the proposed pipe
diameter can be reduced by one pipe size. However, there is a trade-off. The hydraulic reserve
capacity is reduced in half from 50% to 25%.
Modeled simulations were also performed to evaluate the hydraulic capacity of the North
Carolina Museum of Art sewer main and the Lake Boone Trail sewer main. The sewer main
extending to the North Carolina Museum of Art is 10-inches in size. Due to the relatively low
flows generated by the North Carolina Museum of Art, the 10-inch sewer main is more than
adequately sized to convey the future peak flow (0.202 mgd). The sewer main extending along
the Lake Boone Trail corridor is predominantly 15-inches in diameter with a few pipe segments
of 12-inches in diameter. The majority of this sewer main has relatively steep slopes which
allows for sufficient hydraulic capacity to convey the future peak flow (2.1 mgd). There are
several segments that do have relatively flat slopes that would approach flowing full at future
peak flow conditions. However, by lowering the main sewer outfall by approximately 2-feet (to
decrease the starting HGL) and by selectively relaying the flat sloped pipe segments, no major
pipe upsizing is warranted along this corridor. Figure 5 illustrates the HGL of the sewer main
extending along the Lake Boone Trail corridor at the future peak flow condition.
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Alternatives Evaluation
Based upon the results of the hydraulic modeling evaluation, construction cost estimates were
prepared for four separate outfall sewer design alternatives. These construction cost estimates
will assist Hazen and Sawyer and the City of Raleigh in selecting the most cost-effective design for
upsizing the House Subbasin outfall sewer to convey the future peak flow. The alternatives
evaluated included:
Alternative No. I - Anew single outfall to replace the existing outfall
(depth of flow at 50% of pipe diameter at peak flow).
Alternative No. 2 - Anew outfall paralleling the existing and rehabilitation of the
existing outfall system (depth of flow at 50% of pipe diameter
at peak flow).
Alternative No. 3 - Anew single outfall to replace the existing outfall (depth of
flow at 75% of pipe diameter at peak flow).
Alternative No. 4 - Anew outfall paralleling the existing and rehabilitation of the
existing outfall system (depth of flow at 50% of pipe diameter at
peak flow).
Table 9 summarizes the preliminary construction cost estimates for each alternative evaluated.
Alternative Nos. 2 and 4 construction cost estimates included costs to rehabilitate the existing
sewer outfall line and associated manholes. Proposed rehabilitation included the installation of a
cured-in-place pipelines within the existing vitrified clay pipeline and the installation of a
cementitious liner system within the existing brick manholes. Both systems were proposed to
reduce I/I from entering the existing sewer outfall. Detailed construction cost estimates for each
alternative evaluated are appended to this technical memorandum (Appendix D).
Table 9
Alternatives Evaluation
Preliminary Construction Cost Estimate Summary
I New Single Outfall (50% Capacity)
2 New Parallel Outfall and Rehabilitation of
Existing Outfall System (50% Capacity)
3 New Single Outfall (75% Capacity)
4 New Parallel Outfall and Rehabilitation of
Existing Outfall System (75% Capacity)
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$5,8 10,000
$6,350,000
$5,490,000
$6,030,000
House Subbasin
Dynamic Sewer Modeling

As Table 9 illustrates, constructing a new single outfall (Alternative Nos. I and 3) has a lower
estimated construction cost than constructing a new parallel outfall and rehabilitating the existing
outfall system (Alternative Nos. 2 and 4). Obviously, constructing a new single outfall designed
for 75% capacity at peak flow (Alternative No. 3) is less costly than constructing one designed
for 50% capacity (Alternative No. I ). However, the cost differential is only $320,000. The
differential is attributed to material cost of the pipe as installation cost between the two
alternatives is assumed to be negligible.
Recommendations
Based upon the results of the House Subbasin dynamic sewer modeling evaluation, the following
recommendations are made:
• The existing sewer outfall has insufficient hydraulic capacity to convey future peak flows
(4.642 mgd).
• House Subbasin sewer outfall improvements should be made prior to or concurrent with
the proposed "greenway" project to minimize cost and disturbance.
•:• Defer upsizing trunk main along Lake Boone Trail corridor until wastewater flows
warrant improvements. However, sewer main crossing under the I-440 Beltline should
be upsized to 18-inches to facilitate future construction.
• No need to upsize trunk main extending to North Carolina Museum of Art.
•:• Upsize House Subbasin sewer outfall from Crabtree Valley Avenue to the North
Carolina State Veterinary Medical Facility. Construct a new single outfall line in lieu of
constructing a new parallel and rehabilitating the existing outfall. Anew single outfall line
offers several advantages including lower estimated construction costs, construction
within the existing outfall right-of-way, and the potential to eliminate existing aerial creek
crossings.
• Due to small cost differential, design new sewer outfall for 50% flowing full at future
peak flows. Construction cost is estimated at $5,810,000 (includes a 30% contingency).
•:• Pipe material for new sewer outfall should be either DIP with an interior coating for
corrosion protection or thick walled PVC analogous to C900.
•:• Recommended pipe sizes should be upsized to standard pipe diameters to facilitate O&M
practices. As such, the recommended 21 and 15-inch pipe segments should be upsized
to 24 and 16-inches, respectively. A figure illustrating the recommended pipe sizes is
appended to the end of this technical memorandum (Appendix E).
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Dynamic Sewer Modeling

Appendix A
House Subbasin Manhole Field Survey

Appendix B
House Subbasin Flow Monitoring Report

Appendix C
Figure of Existing House Subbasin Sewer Outfall

Appendix D
Alternatives Nos. I - 4
Preliminary Construction Cost Estimates

Appendix E
Figures Illustrating Recommended Pipe Sizes for
New House Subbasin Single Parallel Sewer Outfall