HomeMy WebLinkAboutQuendall Terminals Sewer ReportQuendall Terminals
Renton, Washington
Sewer Report
November 2009 | Preliminary Report
Sewer Report
November 2009
Prepared for:
CenturyPacific, LP
1201 Third Avenue, Suite 1680
Seattle, WA 98101
Prepared by:
Tom Jones
Kris Koski, EIT
KPFF Consulting Engineers
1601 Fifth Avenue, Suite 1600
Seattle, WA 98101
(206) 622-5822
KPFF Job No. 109118.10
Property Owners:
Altino Properties, Inc., and J.H. Baxter & Company
CenturyPacific, LP
Quendall Terminals i
CenturyPacific, LP
Quendall Terminals ii
Table of Contents
1. Introduction.......................................................................................................1
2. Predeveloped Site Conditions...........................................................................1
3. Developed Site Conditions................................................................................2
4. Basis of Design .................................................................................................2
5. Design Criteria...................................................................................................3
Points of Connection...........................................................................................3
Existing Baxter Lift Station..................................................................................4
List of Tables
Table 1-1: Proposed Development..................................................................................1
Table 5-1: Design Criteria.................................................................................................3
Table 5-2: Building Area Summary and Sanitary Sewer Flows......................................3
Table 5-3: Lift Station Design Assumptions for Quendall Terminals .............................4
Appendix
Figure 1: Project Location
Figure 2: Existing Site Conditions
Figure 3: Site Plan
Figure 4: Proposed Sewer Plan
Figure 5: Calculations
Figure 5: Baxter Lift Station Sewer Report
1. Introduction
Quendall Terminals is a proposed mixed-use development in Renton, Washington. The development
includes five stories of residential or office space above two levels of above-grade parking or retail and
restaurant space. The development project anticipates entitlement of the following:
Table 1-1: Proposed Development
Use Quantity/Area
Residential 800 Units
Office 245,000 Square Feet
Retail 21,600 Square Feet
Restaurant 9,000 Square Feet
Parking 2,215 Spaces
Note: All areas shown are gross building areas (GBA).
The project site is located west of Interstate 405 near the northern city limits of Renton. The site is
bounded by the Seahawks Training Facility to the north, BNSF railroad tracks to the east, and the
Barbee Mill residential community to the south. Ripley Lane is located east of the BNSF railroad
tracks and Lake Washington Boulevard is located southeast of the project site. See Figure 1 in the
Appendix for the site location.
This report is intended to support City of Renton entitlement processing for Master Site Plan Approval.
The scope of this report is to address the sanitary sewer system for the proposed development.
Design criteria will be outlined and a sewerage approach will be evaluated.
2. Predeveloped Site Conditions
The existing site is vacant and is the former location of a log sorting and storage yard. The main site is
approximately 20.30 acres in size, and the parcel east of the main project site across Ripley Lane
North is approximately 1.15 acres in size. An existing 12-inch sanitary sewer main runs from south to
north along the east side of the site within a 60-foot roadway and utility easement. The invert
elevation of the existing sewer pipe is generally 10 to 13 feet below the existing ground surface. The
existing Baxter Lift Station serves Quendall Terminals as well as the Seahawks Training Facility to the
north and Barbee Mill to the South. There are no other sewers located on the project site. An 84-inch
Metro sewer main is located approximately 100 feet east of the site’s east property line. See Figure 2
in the Appendix for existing site conditions.
CenturyPacific, LP
Quendall Terminals 1
3. Developed Site Conditions
The proposed site improvements include a mixed-use development consisting of residential, office,
retail, and restaurant uses, as well as new public and private streets and parking. Sewer mains will be
constructed within the proposed public streets. Sewage from the buildings will discharge to the new
sewer mains via side sewers. The new sewer mains will discharge to the existing 12-inch sewer main
at the east side of the project site at a new manhole constructed over the existing main. No
improvements are planned for the 1.15-acre parcel east of Ripley Lane. See Figures 3 and 4 in the
Appendix for proposed site plan and proposed sewer plan, respectively.
4. Basis of Design
An on-site sanitary sewer system will collect and convey flows from Quendall Terminals. Adjacent sites
are already developed and served by separate sanitary sewer systems. This report has utilized
programmed project areas and Department of Ecology (DOE) criteria to establish projected sewer flows
without provisions for future growth or connections. See Figures 3 and 4 in the Appendix for proposed
site plan and proposed sewer plan, respectively.
Gross building areas have been used for this report.
An allowance of 1,100 gallons/acre/day (gpad) has been made for infiltration and inflow since the
proposed sanitary sewer system is expected to be below seasonal high groundwater elevations.
The 1.15-acre parcel east of Ripley Lane has not been included in the infiltration calculation.
A peaking factor of 4.0 was included in the design flows. This factor should account for the daily and
seasonal fluctuations in waste generation. This factor should also mitigate the impact of the varying
flow generations for the different uses proposed with this project.
The sanitary sewer system was designed to convey the estimated peak flows by gravity to the project
discharge location at a new manhole installed on an existing City of Renton sanitary sewer pipe. The
sewer capacities were established using Manning’s Equation, with an “n” factor of 0.013. Sewer lines
have been designed using the minimum slope requirements of the Washington State DOE. The pipe
slopes used in the final design and future construction documents may be greater than the minimum
slope to accommodate potential settlement, depending on the recommendation of the geotechnical
engineer.
CenturyPacific, LP
Quendall Terminals 2
5. Design Criteria
Table 5-1: Design Criteria
Use Unit Flow – Gallons per Day
(gpd) Peak Factor
Residential Per Unit 175 4
Office Per Square Foot 0.2 4
Retail Per Square Foot 0.3 4
Restaurant Per Seat 50 4
I/I Per Acre 1,100 1
Table 5-2: Building Area Summary and Sanitary Sewer Flows
Use Unit Size Total Flow – Gallons
per Minute (gpm)
Residential Unit 800 389
Office Square Feet 245,000 136
Retail Square Feet 21,600 18
Restaurant* Seat 396 55
I/I Acre 20.3 16
Total 614
*Assumes 1 seat per 22.7 square feet
See Figure 5 in the Appendix for calculations.
POINTS OF CONNECTION
Points of connection are available along an existing City of Renton 12-inch concrete sanitary sewer line
that flows south to north within a 60-foot roadway and utility easement along the east side of the
project site to the existing Baxter Lift Station. The point of connection for the proposed development
will be a new manhole constructed over the existing sanitary sewer pipe.
CenturyPacific, LP
Quendall Terminals 3
CenturyPacific, LP
Quendall Terminals 4
EXISTING BAXTER LIFT STATION
The Baxter Lift Station is an existing sewer lift station located at the northeast corner of the project site
within a sanitary sewer easement. The lift station was designed in 2006 and was constructed in
2009. The lift station was designed for an overall peak flow of 594 gpm for the Seahawks Training
Facility, Barbee Mill community, and the Quendall Terminals site. The lift station was designed and
constructed with the following assumptions for future development of the Quendall Terminals site:
Table 5-3: Lift Station Design Assumptions for Quendall Terminals (per Figure 6)
Developable Acres 5 Tributary Area 5.0 Acres
Flow Rate 2,800 gpad
Number of Units 75 Tributary Area 3.0 Acres
Persons/Unit 2.4
Flow Rate 100 gpad
Average Sewerage Flow 22.2 gpm Design I/I Rate 1,500 gpad
Peaking Factor 4
Design Sewage Flow 88.9 gpm Design I/I Flow 8.3 gpm
Total Design Flow 97.2 gpm Total Design Flow Q peak hourly
The sewer lift station was designed for a flow of 97.2 gpm from the Quendall project site. The
anticipated flow from the Quendall project site is 614 gpm. The sewer lift station capacity will need to
be increased by approximately 517 gpm to 1,111 gpm to accommodate development of the Quendall
Terminals site. Per discussion with the City of Renton Public Works, the existing lift station has the
ability to be modified to increase capacity by changing pump impellers and increasing the wet well
capacity. See Figure 6 in the Appendix for Baxter Lift Station design details and Figure 7 for a record
of discussion with the City.
Appendix
Figures
Figure 1: Project Location
Figure 2: Existing Site Conditions
Figure 3: Site Plan
Figure 4: Proposed Sewer Plan
Figure 5: Calculations
Figure 6: Baxter Lift Station Sewer Report
Figure 7: Telephone Record (Lift Station Flows)
CenturyPacific, LP
Quendall Terminals Appendix
KPFF Consulting Engineers November, 2009
Quendall Terminals Sewer Report Figure 1: Project Location
FIG 3
KPFF Consulting EngineersNovember, 2009BUILDING USE AND DISCHARGE POINT PER TRIBUTARY AREA UNIT FLOW AND PEAK FACTOR PER BUILDING USETrib. Area ID Resid. Office Retail Rest. Discharge To Use Peak Factor[UNITS] [SF] [SF] [SF] Residential 175 [per unit2]4NE Trib. Area 0 117500 4800 0 Reach 3 Office 0.2 [per sq ft] 4SE Trib. Area 175 107500 4500 0 Reach 2 Retail 0.3 [per sq ft] 4SW Trib. Area 1 360 0 0 0 Reach 2 Restaurant350 [per seat] 4SW Trib. Area 2 90 10000 6300 4500 Reach 4I/I41100 [per acre] 1NW Trib. Area 1 100 0 0 0 Reach 3NW Trib. Area 2 75 10000 6000 4500 Reach 4NOTESTotal 800 245000 21600 9000 Reach 11 Unit flows include normal infiltration2 Assumes 1.75 residents per unitBUILDING USE PER REACH3 Restaurant conversion: 1 seat = 22.7 square feet of restaurantReach ID Resid. Office Retail Rest. Rest.4 Infiltration due to high groundwater[UNITS] [SF] [SF] [SF] [SEATS3]Reach 1 800 245000 21600 9000 396FLOW PER REACHReach 2 535 107500 4500 0 0 Reach ID Resid. Office Retail Rest. I/I TotalReach 3 100 117500 4800 0 0 [GPM] [GPM] [GPM] [GPM] [GPM] [GPM]Reach 4 165 20000 12300 9000 396 Reach 1 389 136 18 55 16 614Reach 2 260 60 4 0 4 328INFILTRATION/INFLOWReach 3 49 65 4 0 4 122Site Size [AC] Flow [GPD/AC] Flow [GPM] Reach 4 80 11 10 55 4 16120.3 1100 16PIPE CALCULATIONSReach ID Upstrm. MH Downstrm. MH Length Inner Dia Upstrm. IE Downstrm. IE Slope n QfullQfullQdesign% Cap. VfullOrigin of Flow[FT] [IN] [FT] [FT] [FT/FT] [CFS] [GPM] [GPM] [FPS]REACH 1REACH 2, REACH 3, REACH 4SSMH #2 SSMH #1 335 12 19.23 18.49 0.0022 0.013 1.68 754 614 81% 2.14REACH 2SE Trib. Area, SW Trib. Area 1SSMH #3S-2 SSMH #3S-1 278 8 21.88 20.77 0.0040 0.013 0.77 344 328 95% 2.19SSMH #3S-1 SSMH #2 278 8 20.67 19.56 0.0040 0.013 0.77 344 328 95% 2.19REACH 3NE Trib. Area, NW Trib. Area 1SSMH #3N SSMH #2 340 8 20.92 19.56 0.0040 0.013 0.77 344 122 35% 2.20REACH 4SW Trib. Area 2, NW Trib. Area 2SSMH #3W SSMH #2 271 8 20.64 19.56 0.0040 0.013 0.76 343 161 47% 2.19Unit Flow1 [GPD]Quendall Terminals Sewer Report Figure 5: Calculations
Quendall Terminals Sewer Report Figure 6: Baxter Lift
Station Sewer Report
KPFF Consulting Engineers 11/2009
Quendall Terminals Sewer Report Figure 6: Baxter Lift
Station Sewer Report
KPFF Consulting Engineers 11/2009
Quendall Terminals Sewer Report Figure 6: Baxter Lift
Station Sewer Report
KPFF Consulting Engineers 11/2009
Quendall Terminals Sewer Report Figure 6: Baxter Lift
Station Sewer Report
KPFF Consulting Engineers 11/2009
1601 Fifth Avenue, Suite 1600 Seattle, WA 98101 (206) 622-5822 Fax (206) 622-8130
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Notes
By:Tom Jones
Date: 6/16/09
Telephone
Record
Time Begin: Time End:
With:Dave Christensen
Company: City of Renton Public Works
Address:
Phone: Fax:
Regarding:Quendall Sewer Capacity, Anticipated Sewer Flows
KPFF Project #: 109118
CC:Campbell Mathewson, Mark Veldee
Conversation:
I called Dave to discuss the existing Baxter Sewer Pump Station capacity and its ability to handle the
anticipated flows from the Quendall Terminals development currently being planned.
Existing Baxter Pump Station:
The existing sewer pump station was designed to include conservative flows from the Quendall site
(hotel & office only 100gpm). The conservative approach was based on the information at the time
related to traffic constraints that would limit development for the site.
The current location of the Baxter Pump Station is within the center of the access drive between the
Seahawks and Quendall, which will require street access between the two sites to “meander” around
the PS. Dave indicated when the PS was planned the access between these two sites did not exist.
Proposed Quendall Flows:
KPFF has run estimated peak flows based on the 5/7/09 and 6/16/09 Lance Mueller layouts in the
range of 500gpm based on a peaking factor of 4.0. The City uses a peaking factor of 2.0 for individual
site masterplans where specific site density is being planned and the change in peak flow (change is
use/density) is not anticipated to be a major divergence in the future over the original masterplan. A
2.0 peaking factor would provide an estimated sewer demand of 250gpm less the 100gpm available
results in a 150gpm capacity deficit.
Dave indicated the existing pump station has the ability to be modified to increase the existing pump
station capacity by 300+-gpm. This would include changing pump impellers and adding additional wet
well capacity, relatively minor modifications (less than $100k) that would be a Quendall developer
cost.
Figure 7
KPFF Consulting Engineers Page 2 Telephone Record November 17, 2009
Other available options are installing larger pumps but Dave did not believe that would be necessary
as the existing pumps were specifically chosen to allow impeller modifications as they anticipated the
need for additional capacity in the future.
Fees:
Quendall has recently been assessed a capacity charge of $166k for their “fair share” of the Baxter
Pump Station. This assessment was based on 111gpm of capacity. I asked Dave if future
assessments would be required if the flows exceeded the 111gpm. Dave indicated there would be NO
additional capacity charge assessments for the Quendall site only mechanical pump station upgrades
to increase the pump station capacity to meet our proposed site demand.
Figure 7