HomeMy WebLinkAboutWYNFIELD RIDGE P ETERSON
CONSULTING
4030 Lake Washington Blvd. N.E., Suite 200, Kirkland, WA 98033
WYNFIELD RIDGE
Technical Information
Report
City of Newcastle
May 25, 2001
Prepared for:
Chaffey Homes
205 Lake Street S.
Suite 101
Kirkland, WA 98033
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Prepared by: ��� ors °
Robert Stewart '� jONAL �� f1l
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Reviewed by: EXPIRES 09109/02
Jennifer A. Steig, P.E.
PCE Job No. CHAF-0008
Soil Type Slopes Erosion Potential Erosive Velcoties
AgC 6% - 15% none none
AQD 15% -40% none none
❑ Additional Sheets Attached
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REFERENCE LIMITATION/SITE CONSTRAINT
(� Appendix A—Downstream Analysis by
D.R. Strong
❑ Additional Sheets Attached
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION AFTER CONSTRUCTION
Sedimentation Facilities Stabilize Exposed Surface
Stabilized Construction Entrance Remove and Restore Temporary ESC Facilities
❑ Perimeter Runoff Control Clean and Remove All Silt and Debris
❑ Clearing and Graing Restrictions Q Ensure Operation of Permanent Facilities
❑ Cover Practices ❑ Flag Limits of SAO and open space
Construction Sequence preservation areas
❑ Other
El Other
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❑ Grass Lined ❑ Tank ❑ Infiltration
Method of Analysis
Channel 3[Q 1998 KCRTS Vault ❑ Depression
Pipe System
❑ Energy Dissapator ❑ Flow Dispersal Compensation/Mitigati
❑ Open Channel ❑ Wetland ❑ Waiver on of Eliminated Site
❑ Dry Pond Storage
❑ Stream ❑ Regional
❑ Wet Pond Detention
Brief Description of System Operation Runoff will be conveyed via a tightline system into a
proposed wetvault facility and released at allowable rates at
the natural discharge locations
Facility Related Site Limitations
Reference Facility Limitation
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Parl 11: THE Tt t 1�.."..! 17 tT
F AGT
Cast in Place Vault X Drainage Easement
Retaining Wall Access Easement
❑ Rockery > 4' High Native Growth Protection Easement
❑ Structural on Steep Slope X Tract
❑ Other ❑ Other
.
rt 13 51GNA#+UI E F Pl SSIQPt .I Nall 1~EI `:.<>: >:
I or a civil engineer under my supervision my supervision have visited the site. Actual site
conditions as observed were incorporated into this worksheet and the attachments. To the best of
my knowledge the information provided here is accurate.
Si ne&Dafe
TABLE OF CONTENTS
SECTION1 PROJECT OVERVIEW...................................................................................................................I
SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY ........................................................................5
SECTION3 OFF-SITE ANALYSIS...................................................................................................................13
SECTION 4 FLOW CONTROL &WATER QUALITY ANALYSIS AND DESIGN.....................................13
SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN................................................................25
ConveyanceCalculations.....................................................................................................................25
OutletRiser..........................................................................................................................................26
DOWNSTREAMCONVEYANCE ANALYSIS...................................................................................................................... 27
SECTION 6 SPECIAL REPORTS AND STUDIES...........................................................................................28
SECTION7 OTHER PERMITS.........................................................................................................................28
SECTION 8 ESC ANALYSIS AND DESIGN....................................................................................................28
SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF COVENANT...29
SECTION 10 OPERATIONS AND MAINTENANCE MANUAL......................................................................29
Peterson Consulting Engineers Page i
Figures
Figure 1: Vicinity Map 2
Figure 2: Site Map 3,4
Figure 3: Existing Conditions Map 14,15
Figure 4: SCS Soils Map 16
Figure 5: Developed Conditions Map 17,18
Figure 6: Detention Facility 32
APPENDIX A
Downstream analysis submitted by D.R. Srong
APPENDIX B
Figure 5.3.4H from KCSWDM, riser inflow curves
Community Planning Area Map
Drainage Basin Map
APPENDIX C
Geotech Report by Zipper Zeman Associates, Inc. Dated February 11, 1999.
i
Peterson Consulting Engineers Page ii
Technical Information Report forWynfield Ridge May 25, 2001
SECTION I PROJECT OVERVIEW
Project: Wynfield Ridge
PCE Job Number: CHAF-0008
Site Area: The site consists of approximately 191,664 Square feet—4.4 Acres.
Site Location:
The site is located within the City of Newcastle approximately 300' north of the
intersection of 116th Avenue SE and SE 85th Street and on the west side of 116th
Avenue SE. Also, the west property line is located adjacent to the
Renton/Newcastle city limits (see Figure 1: Vicinity Map on following page).
More generally, the site is located within Section 32, Township 24 North, Range 5
East, W.M.
Existing Adjacent Development:
Existing development adjacent to the site includes the following:
North - Single-Family Residential and undeveloped parcels
East— 116th Avenue SE
South - Single-Family Residential and undeveloped parcels
West— 30' wide easement, 112th Place SE (not open)
Pre-developed Site Conditions:
The existing site runoff patterns are generally from east to west. The site consists
of one drainage basin that drains westerly towards Monterey Place NE. The
existing site is mostly undeveloped, with the exception of a single family residence
and gravel drive. The ground cover on the site consists mainly of forest on the
western portion of the site and pasture on the eastern portion. On the west portion
of the site, there are wetlands and some areas with slopes greater than 40%. These
steep slopes and sensitive areas and their will be dedicated to the city.
Post-developed Site Conditions:
The proposal is to construct 13 lots with associated roads and utilities. (See
Figure 2: Site Map on Page 4). Runoff patterns from the developed site will be
similar to the existing conditions. The runoff from proposed roads, driveways,
roof drains and landscaped areas will be conveyed via a closed pipe system to a
proposed combined detention and water quality treatment facility and released at
allowable release rates. See Section 4 for a detailed discussion and calculations.
Peterson Consulting Engineers Page 1
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VICINITY MAP
WYNFIELD RIDGE
SEC. 32, TWP. 24 N., RGE. 5 E., W.M.
DWN. BY.- DATE: JOB NO.
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CONSULTING Kirkland, WA 98033
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Technical Information Report forWynfreld Ridge AI qv 25, 2001
SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY
Preliminary plat approval for this submittal was granted February 6, 2001. 1998 King County
Surface Water Design Manual Core and Special Requirements and Hearing Examiner's
Conditions are being met in the following manner:
King County Surface Water Design Manual Core Requirements:
1. Discharge at the Natural Location
This site will discharge at the natural location.
2. Off-site Analysis
Previously prepared and submitted to City of Newcastle, see Section 3 for more
information.
3. Flow Control
Calculations performed under Section 4 of this TIR conform to the 1998 KCSWDM
requirements. A Level 2 flow control facility will be used on the site.
4. Conveyance
All conveyance systems proposed conform to the 1998 KCSWDM requirements, see O
Section 5 of this TIR. q
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5. Temporary, Erosion& Sediment Control
All TESC measures proposed conform to 1998 KCSWDM requirements, see Section 9 of
this TIR and the construction plans.
6. Maintenance & Operations
A maintenance and operations manual is provided in Section 10 of this TIR.
7. Financial Guarantees & Liability
A bonds worksheet will be completed after first review. The project owner will provide
bonding as required by the City of Newcastle.
8. Water Quality
Water quality facilities, in the form of a wetvault will be provided on this site.
Peterson Consulting Engineers Page 5
Technical Information Report for WynfieldRidge May 25, 2001
King County Surface Water Design Manual Special Requirements:
1. Other Adopted Area-specific Requirements
There are no other adopted area-specific requirements for this site.
2. Floodplain/Floodway Delineation
This site does not lie within the 100-year floodplain or floodway of any stream, lake,
wetland or closed depression.
3. Flood Protection Facilities
There are no flood protection facilities located on or directly adjacent to this site.
4. Source Control
This site does not meet the threshold for source control requirements.
5. Oil Control
This site does not meet the threshold for source control requirements.
Hearing Examiner's Conditions:
B. RECOMMENDATION:
Based upon the foregoing findings and conclusions, it is recommended that the proposed plat of
Wynfield Ridge be granted preliminary approval subject to the following conditions of final
approval.
1. The revised Significant Tree Retention Plan submitted October 20, 2000, (Exhibit 1,
Attachment F) shall be substantially adhered to for required tree retention per AMC
18.16.130, unless otherwise authorized by the Director of Community Development.
If the significant tree plan is revised it will be submitted to the City of Newcastle for
approval by the Director.
2. To protect significant trees from the impacts of the proposed development, the boundaries
of the clearing limits shown on the approved plans shall be.fenced prior to construction
with a 6 foot high chain link fence securely mounted and attached to driven steel posts.
Protective fencing shall remain in place throughout grading and clearing and during the
course of construction and shall be maintained by the applicant. Removal of the fencing
shall be authorized by the City at the time of final engineering inspection. Trees that
sustain damage during the course of construction shall be replaced pursuant to AMC
18.16.160. A representative of the City of Newcastle shall verify protective_fencing
Peterson Consulting Engineers Page 6
Technical Information Report forWynfield Ridge May 25, 2001
placement per this condition prior to issuance of a notice to proceed for grading and
clearing. The City shall inspect for compliance with the retention plan prior to a final
inspection. The inspection shall also evaluate the condition of retained trees and any and
all corrections will be required to be completed prior to a final inspection and sign-off.
Tree protection, as indicated above, will be installed prior to clearing and grading of the site.
3. As determined by the City of Newcastle Parks Department, the Applicant shall pay a fee-
in-lieu-of on site recreation space per AMC 18.24.230.
There is no recreation space on site and the applicant will pay a fee-in-lieu-of.
4. The Applicant shall provide mitigation,for an increase in storm water volumes and water
quality impacts by complying with the 1998 King County Surface Water Design Manual
(KCSWDM) design standards as adopted by the City. A complete Technical Information
Report (TIR) shall be submitted to the City prior to the issuance of any construction
permits.
A level two flow control per the 1998 KCSWDM, has been provided onsite.
5. After construction is complete, the Applicant shall clean all pipes, inlets, and outlet areas
as directed by the City,for those areas affected by the project. The City and Applicant
shall inspect the system prior to start of construction to verify the existing condition of
the system.
All existing pipes, inlets, and outlet areas will be inspected prior to construction and all
systems will be cleaned following construction as directed by the City.
6. The Applicant shall provide all necessary easements for the proposed storm system
including necessary maintenance access as determined by the City Engineer. Said
easements shall be clearly delineated on the plans prior to issuance of any construction
permits. Language of the same shall be provided for review and approval by the City
Attorney and City Engineer. All drainage easements and covenants shall be recorded at
final plat recording.
All necessary easements will be delineated on the plans and proper language will be
provided, prior to recording of the final plat.
7. The Applicant shall adhere to the design requirements and best management practices
identified in the 1998 KCSWDM, as a minimum, with respect to erosion control.
Proper erosion control and best management practices will be followed as specified by the
1998 KCSWDM.
8. The Applicant shall be required to submit simultaneously for review and approval all
clearing and grading plans, engineering construction drawings, and other site
improvement plans to the City.
Peterson Consulting Engineers Page 7
Technical Information Report,forWynfield Ridge May 25, 2001
Clearing, grading, and storm drainage plans will be submitted to the City for review.
Sewer and water plans will be prepared by the Coal Creek Sewer and Water District.
9. The Applicant shall be required to mitigate for potentially exacerbating downstream
channel incision and undermining of a rock headwall located in the City of Renton
approximately 1,300 feet from the subject property, according to the requirements of the
City of Renton. At the time of engineering construction review, the Applicant shall
submit to the City of Newcastle all plans, which make provisions for said mitigation, as
required and approved by the City of Renton.
Kayren Kittrick, Plan Review Supervisor for the City of Renton stated that the complaint
could not be located and is unaware of any existing problems.
10. Prior to or upon final plat recording the Applicant shall dedicate 12 feet of additional
street right-of-way to the City along the site frontage on Ile Avenue SE. Dedication
shall be noted on final plat drawing. The existing right-of-way is 30 feet wide from the
street centerline to the property line, and 42 feet is required for a minor arterial (half of
the 84 foot total requirement of City of Newcastle Public Works Standards).
All dedications will be noted on final plat in accordance with the City of Newcastle Public
Works Standards.
11. Prior to final plat approval, the Applicant shall construct vertical curb, gutter, sidewalk,
paving and related improvements along the site frontage on 116`h Avenue SE to City
standards for a three-lane Minor Arterial (Urban)per City of Newcastle Public Works
Standards. The future curb-to-curb width on 116`h Avenue SE shall be a minimum of 44
feet, to allow for three future motor vehicle traffic lanes, plus bike lanes on both sides.
The curb along the site frontage shall be constructed 22.feet front the centerline. A
suitable walkway transition (and barricade if necessary) shall be installed at the end of
the proposed sidewalk.
All frontage improvements shall be constructed to Newcastle's Public Works Standards.
12. Prior to or upon final plat recording, the Applicant shall dedicate street right-of-way to
the City and prior to final plat approval shall construct vertical curb, gutter, sidewalk,
paving and related improvements to the proposed SE 85`h Street to City standards for a
half street with a Subcollector Street (Urban) classification per City of Newcastle Public
Works Standards.
SE 851h Street improvements shall be constructed to the Newcastle Public Works
Standards.
13. Prior to or upon final plat recording the Applicant shall dedicate street right-of-way to
the City and prior to final plat approval shall construct vertical curb, gutter, sidewalk,
paving and related improvements to the proposed 1141h Avenue SE to City standards for
a Subcollector Street (Urban) classification per City of Newcastle Public Works
Peterson Consulting Engineers Page 8
Technical Information Report forWynfield Ridge May 25, 2001
Standards.
110' Avenue SE improvements shall be constructed to the Newcastle Public Works
Standards.
14. Prior to final plat approval the Applicant shall construct a temporary cul-de-sac
turnaround at the end of the proposed SE 85`h Street per City of Newcastle Public Works
Standards.
A temporary cul-de-sac will be constructed at the end of SE 85`h Street per City of
Newcastle Public Works Standards.
15. Prior- to final plat approval, the Applicant shall construct a fence on the south side of the
proposed SE 85`h Street to provide a physical separation from the existing "SE 85`h
Lane" located on the adjacent property to the south, in order to eliminate cross-traffic.
A hedge may be installed as offered by the applicant.. Said fence and hedge are to be
maintained by a Homeowner's Association. If the adjacent property were subdivided in
the future, this "SE 85`h Lane" would be improved and become the south half of SE 85`h
Street.
A fence will be installed on the south side of SE 85'' Street and will be maintained by the
Homeowners Association.
16. The Applicant shall install illumination continuously along all streets constructed or
reconstructed.for the project per City of Newcastle Public Works Standards, prior to
final plat approval. The Applicant shall submit street illumination plans and
calculations to the City for review prior to issuance of any construction permits.
Street illumination will be provided as requested.
17. Prior to final plat approval the Applicant shall install a barricade and sign stating
"THIS STREET TO BE EXTENDED WITH FUTURE DEVELOPMENT BEYOND THIS
POINT" at the end of each street, which is to be extended in the future, per City of
Newcastle Public Works Standards.
All appropriate barricades and signs will be installed.
17. Prior to final plat approval the Applicant shall provide a pavement marking and traffic
signing design jor review and approval by the City. Pavement markings should consist
of a stop bar on SE 85`h Street at the 116`h Avenue SE intersection. Traffic signs should
include an RI-1 "STOP" sign and a W14-2 "NO OUTLET"sign on SE 85`h Street at the
116`h Avenue SE intersection.
All appropriate pavement markings and signs will be installed.
18. The Applicant shall pay King County's Mitigation Payment System (MPS) fees, which
assess mitigation,for the construction of future improvements to Coal Creek Parkway SE,
Peterson Consulting Engineers Page 9
Technical Infonnation Report.forNlynfield Ridge May 25, 2001
as required by the City's adopted transportation mitigation ordinance. MPS,fees would
be collected by King County under the fee schedule in effect at the time of building
permit issuance. Fees applying to road projects under the City's jurisdiction would be
returned to the City. The project site is within MPS zone #422. hz addition, the
Applicant shall pay for any administrative costs incurred by King County .for
administration of the MPS fees, as applicable, to be paid incrementally with building
permit issuance.
The appropriate MPS fees will be paid to King County.
19. As necessary during construction, all trucks shall be inspected and cleaned before
leaving the site in order to ensure that dirt, mud, and other materials are not deposited
on public streets. The Applicant shall provide for prompt sweeping or cleanup of any
,dirt, mud or other materials deposited by the project's trucks on public streets.
Temporary traffic control shall be provided as necessary for safe sweeping or cleanup
operations. No cement truck wash out is permitted in the City of Newcastle.
Trucks will be inspected as required. See note on TESC plans.
20. The Applicant shall distribute appropriate current transit, carpool, vanpool and ride-
matching information to new residents immediately after the initial sale or rental of each
house.
So noted.
22. Prior to final plat approval the Applicant shall implement or financially assure a
landscaping plan and maintenance agreement for landscaping within City right-of-way.
A landscaping plan will be submitted to the City for review and approval.
23. During the construction of the proposed improvements, the Applicant shall provide and
maintain safe and convenient access to all adjacent properties at all times.
Safe and convenient access will be maintained during construction.
24. The Applicant shall observe the hours of operation per applicable City ordinances
during the construction of the development.
During construction, proper hours of operation will be observed in accordance with City
ordinances.
25. Any damage as a result of this project to existing roads, installation of utilities, or
improvements to existing roads will require the Applicant to overlay and/or reconstruct
the entire road width where damage, utility installation, or improvements occur.
Any damage to roadways or utilities that occur as a result of the project will be repaired as
necessary.
Peterson Consulting Engineers Page 10
Technical Information Report forWynfield Ridge May 25, 2001
26. The steep slope hazard buffer shall be reduced from 50' to10'as proposed by the
Applicant. A 15 foot building setback shall be established.from the edge of the steep
slope buffer per AMC 18.24.190.
Proper steep slope buffers and building set backs will be observed.
27. Sensitive area tracts, Tracts A and D, shall be dedicated to the City of Newcastle.
Tracks A and D shall be dedicated to the City.
27. Tract C shall be dedicated to the City of Newcastle.
Tract C shall also be dedicated to the City.
28. Pursuant to AMC 18.24.170, the Applicant shall file a notice on title of all sensitive
areas and their buffers on site, as defined by the AMC, to be approved by the City with
the county's records and elections division. The notice shall inform the public of the
presence of sensitive areas or buffers on the property, of the application of Chapter
18.24 of the AMC to the property, and those limitations on actions in or affecting such
sensitive areas or buffers may exist. The notice shall run with the land.
A notice on title will be filed of all sensitive areas and their buffers.
30. All existing vegetation within the steep slope hazard areas and their buffers shall be
protected and retained.
No work is proposed within the steep slope hazard area or its buffer.
31. The Applicant shall be responsible for obtaining any necessary state,federal, and other
permits and approvals for the project, and shall comply with any conditions of approval
placed on these other permits or approvals, and for submitting revised drawings to the
City for its review and approval, if necessary to reflect these other conditions of
approval. The Applicant shall obtain these permits and approvals, with copies of the
same submitted to the City,prior to the City issuing any construction permits.
So noted.
32. Prior to final plat approval, the Applicant shall construct all required improvements.
The only exceptions would be the final lift of pavement, street trees and sidewalks. These
three items can be financially assured. The final lift of pavement and street trees shall
be completed within one year of final plat approval.. Sidewalks shall be completed prior
to final inspection of the first home within the subdivision. Notwithstanding the above,
all improvements constructed along the frontage of existing streets shall be complete
prior to final plat approval.
So noted.
Peterson Consulting Engineers Page I
Technical Information Report for WynfieldRidge May 25, 2001
33. The applicant shall submit to the City a copy of the Homeowners Association Articles of
Incorporation. The applicant shall submit a copy of proposed CC&R's to the City,for
review and approval prior to recording.
Proposed CC&R's will be submitted to the City for review and approval.
34. All easements and covenants shall be recorded at final plat recording.
So noted.
35.A safety barrier shall be installed along the south corner of proposed SE 85`"Street and
114"'Ave. SE. The location and design of said safety barrier must receive approval from
the City Engineer prior to installation.
Proper safety barriers will be installed with prior approval from City Engineer.
Peterson Consulting Engineers Page 12
Technical Information Report for WynfieldRidge May 25, 2001
SECTION 3 OFF-SITE ANALYSIS
An off-site analysis was previously completed and submitted to the City of Newcastle for review
in April 1999. The report is included in its entirety in the appendix of this TIR.
SECTION 4 FLOW CONTROL & WATER QUALITY
ANALYSIS AND DESIGN
The enclosed calculations are based on the 1998 King County Surface Water Design Manual
(KCSWDM) requirements, as adopted by the City of Newcastle. The site is located in the May
Creek Basin plan, which requires a minimum of a Level 2 Flow Control analysis. Water quality
features for the site will be designed from the basic water quality menu, as dictated by the
KCSWDM Water Quality Applications Map.
Existing Site Hydrology
The site slopes mainly to the west, draining towards the 1121h Avenue SE unopened right-of-way.
Slopes on the site range from 2% to 40%. Vegetation on the site consists of both deciduous and
coniferous trees with a thick under story of blackberry bushes, shrubs, and ferns. There is a
single-family residence on site with a detached garage and shed (see Figure 3: Existing Site
Conditions).
The soils on the site consist of AgC and AgD, Alderwood Gravelly Sandy Loams, and RdE,
Ragnar Indianola Association. AgC and AgD are classified as till soils and RdE is classified as
outwash by Table 3.2.2.13 in the 1998 KCSWDM (see Figure 4: SCS Soils Map).
Developed Site Hydrology
- The proposed development of this site will consist of 13 lots and approximately 1,550 lineal feet
of road. Runoff from the roadways and lots will be conveyed in a closed pipe system to the
proposed detention facility. The facility will be located within Tracts C, as shown on the
construction plans. The vault will include dead storage for basic water quality (see Figure 5:
Developed Site Conditions).
Runoff time series were created using the reduced 8-year data. The hourly series was used to size
the detention facility. The site is located within the SeaTac region with a scale factor of 1.0 and a
soil cover type of till forest and pasture. All pertinent calculations and printouts for the time
series are attached.
Peterson Consulting Engineers Page 13
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` �a• CA9D+�Alderwood gravelly sandy loom,6 to 15 percent slopes i
r, II• Y Akf
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11 w- .z r.;, l I AmB Arents,Alderwood material,0 to 6 percent slopes+- P ir.•, AmC Arents
TB ,Alderwood material,6 to 15 percent slopes
t y,, I An Arents, '
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M1 RaD Ragnar fine sandy loom,6 to 15 percent slopes
i t ir' y RdC Ragnor fine sandy loom, 15 to 25 percent slopes
�I 1'^—RdE Ragnar-Indianola association,sloping• xa
`;1 1 +��Ragnar-Indionola association,moderately steep e
it \ •••• "!;'� �I, Re Renton silt loam
Rh Riverwosh
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SCS SOILS MAP
WYNFIELD RIDGE
SEC. 32, TWR 24 N., RGE. 5 E., W M.
_= DWN. BY.' DATE: JOB NO.
_ - 1 ETERSON 4030 Lake Washington
Blvd. N.E., Suite 200 RSG 5129101 CHAF-0008
CONSULTING Kirkland, WA 98033
Tel (425)827-5874 CHKD. BY. SCALE: FIGURE
Fax(425)822-7216 JA S 4
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TOTAL AREA TO DETAIN = 3.54 AC
IMPERVIOUS = 0.56 AC
PERVIOUS PASTURE = 1.95 AC
` I
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PASTURE _ 0.23 AC — — — ' "— �L!
---- FOREST — 0.21 AC �,,
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e,o O-•I Y�ry R.S7EWART
A N g Z rn y DESIGNED:
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n c� CITYOFNEWCASTLE, WASH/NGTON E7 NAME: 0
Technical Information Report for WynfieldRidge May 25, 2001
Facility Design Methodology
The detention facility was sized by trial and error in accordance with the KCRTS detailed routing
method. The design intent for the detention facility is to maintain the duration of high flows to
their predevelopment levels for all flows greater than one-half of the 2-year peak flow up to the
50-year peak flow (Level 2 flow control standard).
Existing Conditions: Total Area to be detained= 3.54 Acres
Impervious Surface:
Total Impervious = 0.56 acres
Pervious Surface:
Till Pasture = 1.95 acres
Till Forest = 1.03 acres
Total Pervious = 2.98
Flow Frequency Analysis
Time Series File:predev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.299 4 2/09/01 15:00 ✓0.574 1 100.00 0. 990
0. 188 6 1/05/02 16:00 0.322 2 25.00 0.960
0. 322 2 2/27/03 7:00 /0.308 3 10. 00 0. 900
0.148 8 8/26/04 2:00 0.299 4 5. 00 0.800
0.186 7 1/05/05 8:00 0.288 5 3. 00 0.667
0.308 3 1/18/06 16:00 0.188 6 2. 00 0.500
0.288 5 11/24/06 3:00 0.186 7 1.30 0.231
0.574 1 1/09/08 6:00 0.148 8 1. 10 0.091
Computed Peaks 0.490 50. 00 0.980
Developed Conditions: Total Area to be detained = 3.54 Acres
Impervious Surface:
Roads = 0.61 acres
13 Lots/Houses = 0.63 acres
Total Impervious = 1.24 acres
Pervious Surface:
Till Grass = 1.86 acres
Till Pasture = 0.23 acres
Till Forest = 0.21 acres
Total Pervious = 2.30
Peterson Consulting Engineers Page 19
Technical Information Report forff�mfleld Ridge AIay 25, 2001
Flow Frequency Analysis
Time Series File:dev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.488 5 2/09/01 2:00 ,/1. 02 1 100.00 0.990
0.360 7 1/05/02 16:00 0. 592 2 25.00 0. 960
0.592 2 2/27/03 7:00 V"0.516 3 10.00 0. 900
0.345 8 8/26/04 2:00 0.500 4 5.00 0. 800
0.424 6 10/28/04 16:00 0.488 5 3.00 0. 667
0.516 3 1/18/06 16:00 , 0.424 6 2.00 0.500
0.500 4 10/26/06 0:00 0.360 7 1.30 0.231
1. 02 1 1/09/08 6:00 0.345 8 1.10 0.091
Computed Peaks 0. 880 50.00 0. 980
Retention/Detention Facility
Type of Facility: Detention Vault
Facility Length: 90.00 ft
Facility Width: 23.00 ft
Facility Area: 2070. sq. ft
Effective Storage Depth: 10.00 ft
Stage 0 Elevation: 234. 00 ft
Storage Volume: 20700. cu. ft
Riser Head: 10. 00 ft
Riser Diameter: 12.00 inches
Number of orifices: 2
Full Head Pipe
Orifice # Height Diameter Discharge Diameter
(ft) (in) (CFS) (in)
1 0.00 0.88 0.066
2 6.20 2.00 0.211 4. 0
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 234.00 0. 0. 000 0. 000 0.00
0.01 234.01 21. 0. 000 0. 002 0.00
0.02 234. 02 41. 0. 001 0.003 0.00
0.03 234.03 62. 0. 001 0. 003 0.00
0.04 234. 04 83. 0. 002 0.004 0.00
0. 05 234. 05 104. 0. 002 0.005 0.00
0.06 234.06 124. 0. 003 0. 005 0.00
0.07 234. 07 145. 0. 003 0.006 0.00
0.24 234.24 497. 0. 011 0.010 0. 00
0.41 234.41 849. 0. 019 0. 013 0. 00
0.58 234.56 1201. 0. 028 0. 016 0.00
0.75 234.75 1553. 0. 036 0. 018 0.00
0. 92 234. 92 1904. 0. 044 0.020 0.00
1.09 235.09 2256. 0. 052 0. 022 0.00
1.26 235.26 2608. 0. 060 0.023 0.00
1.43 235.43 2960. 0. 068 0. 025 0.00
1. 60 235.60 3312. 0. 076 0. 026 0.00
Peterson Consulting Engineers Page 20
Technical Information Report forWynfield Ridge May 25, 2001
1.77 235.77 3664. 0. 084 0.028 0.00
1.94 235.94 4016. 0. 092 0.029 0.00
2. 11 236.11 4368. 0.100 0. 030 0.00
2.28 236.28 4720. 0. 108 0.031 0.00
2.45 236.45 5072. 0. 116 0.032 0. 00
2.62 236.62 5423. 0. 125 0.034 0.00
2.78 236.78 5755. 0.132 0. 035 0.00
2. 95 236.95 6107. 0.140 0.036 0.00
3.12 237.12 6458. 0.148 0.037 0.00
3.29 237.29 6810. 0. 156 0.038 0.00
3.46 237.46 7162. 0. 164 0.039 0.00
3.63 237.63 7514. 0.172 0.040 0.00
3. 80 237.80 7866. 0. 181 0.040 0.00
3.97 237.97 8218. 0. 189 0.041 0. 00
4. 14 238.14 8570. 0. 197 0.042 0.00
4.31 238.31 8922. 0.205 0.043 0.00
4.48 238.48 9274. 0.213 0.044 0.00
4.65 238.65 9626. 0.221 0.045 0.00
4. 82 238.82 9977. 0.229 0.046 0.00
4. 99 238.99 10329. 0.237 0.046 0.00
5. 16 239.16 10681. 0.245 0.047 0.00
5.33 239.33 11033. 0.253 0.048 0.00
5.50 239.50 11385. 0.261 0. 049 0.00
5. 67 239. 67 11737. 0.269 0.049 0.00
5. 84 239.84 12089. 0.278 0. 050 0.00
6. 01 240.01 12441. 0.286 0. 051 0. 00
6. 17 240. 17 12772. 0.293 0.052 0.00
6.20 240.20 12834. 0.295 0. 052 0. 00
6.22 240.22 12875. 0.296 0. 053 0.00
6.24 240.24 12917. 0.297 0. 055 0. 00
6.26 240.26 12958. 0.297 0. 059 0.00
6.28 240.28 13000. 0.298 0. 065 0.00
6.30 240.30 13041. 0.299 0. 072 0. 00
6.33 240.33 13103. 0.301 0. 081 0.00
6.35 240.35 13145. 0.302 0.090 0.00
6.37 240.37 13186. 0.303 0. 097 0.00
6.54 240.54 13538. 0.311 0. 116 0.00
6.71 240.71 13890. 0.319 0. 131 0.00
6. 88 240.88 14242. 0.327 0. 144 0.00
7. 04 241. 04 14573. 0.335 0. 155 0.00
7.21 241.21 14925. 0.343 0.165 0.00
7.38 241.38 15277. 0.351 0. 174 0.00
7.55 241.55 15629. 0.359 0.183 0.00
7.72 241.72 15980. 0.367 0.192 0.00
7. 89 241. 89 16332. 0.375 0. 199 0.00
8. 06 242.06 16684. 0.383 0.207 0.00
8.23 242.23 17036. 0.391 0.214 0.00
8.40 242.40 17388. 0.399 0.221 0.00
8.57 242.57 17740. 0.407 0.228 0.00
8.74 242.74 18092. 0.415 0.234 0.00
8.91 242. 91 18444. 0.423 0.241 0. 00
9. 08 243.08 18796. 0.431 0.247 0. 00
9.25 243.25 19148. 0.440 0.253 0.00
9.42 243.42 19499. 0.448 0.258 0. 00
9. 59 243.59 19851. 0.456 0.264 0.00
9.76 243.76 20203. 0.464 0.269 0.00
9. 93 243.93 20555. 0.472 0.275 0. 00
10. 00 244.00 20700. 0.475 0.277 0.00
10. 10 244 .10 20907. 0.480 0.588 0.00
10.20 244.20 21114. 0.485 1. 150 0.00
10.30 244.30 21321. 0.489 1. 890 0.00
10.40 244.40 21528. 0.494 2. 680 0.00
Peterson Consulting Engineers Page 21
Technical Information Report forWynfield Ridge May 25, 2001
10.50 244.50 21735. 0.499 2.970 0. 00
10. 60 244.60 21942. 0.504 3.220 0.00
10.70 244.70 22149. 0.508 3.460 0.00
10. 80 244.80 22356. 0.513 3.680 0. 00
10.90 244.90 22563. 0.518 3.890 0. 00
11.00 245.00 22770. 0.523 4.090 0.00
11. 10 245.10 22977. 0.527 4.280 0.00
11.20 245.20 23184. 0.532 4.460 0.00
11.30 245.30 23391. 0.537 4.630 0. 00
11.40 245.40 23598. 0.542 4.790 0. 00
11.50 245.50 23805. 0.546 4.950 0. 00
11.60 245. 60 24012. 0.551 5.110 0. 00
11.70 245.70 24219. 0.556 5.260 0. 00
11.80 245. 80 24426. 0.561 5.400 0. 00
11.90 245.90 24633. 0.565 5.540 0.00
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 1.02 0.57 0. 93 10. 16 244. 16 21032. 0.483
2 0.48 ****�*�* 0..25) 9. 04 243.04 18710. 0.430
3 0.49 ***'**** 0.28 9.95 243. 95 20596. 0.473
4 0.59 *d *�** 0.21 8.05 242.05 16670. 0.383
5 0.52 ** �**** 0.21 8.20 242.20 16983. 0.390
6 0.30 ******* 0._12_ 6.62 240.62 13708. 0.315
7 0.36 ** �**** 0.45 6. 14 240. 14 12701. 0.292
8 0.34 ******* 0.04 3.24 237.24 6704. 0.154
- --------------------------------
Route Time Series through Facility
Inflow Time Series File:dev.tsf
Outflow Time Series File:rdout
Inflow/Outflow Analysis
Peak Inflow Discharge: 1.02 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.927 CFS at 8:00 on Jan 9 in Year 8
Peak Reservoir Stage: 10. 16 Ft
Peak Reservoir Elev: 244.16 Ft
Peak Reservoir Storage: 21032. Cu-Ft
0.483 Ac-Ft
Flow Duration from Time Series File:rdout.tsf
Cutoff Count Frequency CDF Exceedence_Probability
CFS 95
0. 004 38847 63.351 63.351 36.649 0.366E+00
0. 012 7109 11.593 74.945 25. 055 0.251E+00
0. 020 5380 8.774 83.718 16.282 0. 163E+00
0. 027 4029 6.570 90.289 9.711 0. 971E-01
0. 035 2559 4. 173 94.462 5.538 0.554E-01
0. 043 1630 2. 658 97.120 2. 880 0.288E-01
0. 050 1079 1.760 98.880 1. 120 0.112E-01
0. 058 299 0.488 99.367 0. 633 0. 633E-02
0. 066 56 0.091 99.459 0.541 0.541E-02
0. 074 36 0. 0S9 99.517 0.483 0.483E-02
0. 081 26 0. 042 99.560 0.440 0.440E-02
0. 089 10 0. 016 99.576 0. 424 0. 424E-02
0. 097 10 0.016 99.S92 0.408 0.408E-02
0. 105 39 0. 064 99.656 0. 344 0.344E-02
0.112 20 0. 033 99.689 0. 311 0. 311E-02
0.120 26 0. 042 99.731 0.269 0.269E-02
Peterson Considting Engineers Page 22
Technical Information Report forWynfteld Ridge May 25, 2001
0.128 22 0.036 99.767 0.233 0.233E-02
0.135 10 0.016 99.783 0.217 0.217E-02
0.143 6 0.010 99.793 0.207 0.207E-02
0. 151 8 0. 013 99. 806 0. 194 0. 194E-02
0. 159 9 0.015 99. 821 0.179 0. 179E-02
0. 166 14 0.023 99. 843 0.157 0. 157E-02
0.174 13 0.021 99.865 0.135 0. 135E-02
0.182 13 0.021 99. 886 0.114 0.114E-02
0. 190 7 0.011 99.897 0. 103 0. 103E-02
0. 197 10 0.016 99. 914 0. 086 0. 864E-03
0.205 8 0.013 99.927 0. 073 0.734E-03
0.213 10 0. 016 99. 943 0. 057 0.571E-03
0.220 4 0.007 99. 949 0.051 0. 506E-03
0.228 6 0.010 99.959 0. 041 0.408E-03
0.236 3 0. 005 99.964 0.036 0.359E-03
0.244 9 0.015 99. 979 0.021 0.212E-03
0.251 3 0.005 99.984 0.016 0. 163E-03
0.259 2 0.003 99.987 0. 013 0. 130E-03
0.267 2 0.003 99.990 0.010 0. 978E-04
0.275 4 0.007 99.997 0.003 0.326E-04
Duration Comparison Anaylsis
Base File: predev.tsf
New File: rdout.tsf
Cutoff Units: Discharge in CFS
-----Fraction of Time----- ---------Check of Tolerance-------
CutoffBase New %Change Probability Base New $Change
0. 095 I 0. 63E-02 0.41E-02 -35. 1 I 0.63E-02 0. 095 0.058 -38. 6
0. 112 I 0.43E-02 0.31E-02 -28. 9 I 0.43E-02 0.112 0.083 -25.9
0.130 I 0.30E-02 0.23E-02 -23.2 I 0.30E-02 0.130 0.113 -13.2
0.147 I 0.22E-02 0.20E-02 -9. 0 I 0.22E-02 0.147 0.134 -9.3
0. 165 I 0. 15E-02 0. 16E-02 3.2 I 0.15E-02 0.165 0.167 1. 3
0. 182 I 0.11E-02 0. 11E-02 -1. 4 I 0.11E-02 0.182 0.182 -0.3
0.200 I 0.91E-03 0. 85E-03 -7. 1 I 0. 91E-03 0.200 0.196 -1. 9
0.218 I 0.72E-03 0.52E-03 -27.3 I 0.72E-03 0.218 0.205 -5.7
0.235 I 0.52E-03 0.36E-03 -31.2 I 0.52E-03 0.235 0.218 -7.5
0.253 I 0.34E-03 0.16E-03 -52.4 I 0.34E-03 0.253 0.236 -6.5
0.270 I 0. 18E-03 0.49E-04 -72.7 0.18E-03 0.270 0.249 -7. 7
0.288 I 0. 11E-03 0.00E+00 -100. 0 I 0.11E-03 0.288 0.265 -8. 0
0.305 I 0.49E-04 0.00E+00 -100.0 I 0.49E-04 0.305 0.272 -11.0
Maximum positive excursion = 0.005 cfs ( 3.5$)
occuring at 0.158 cfs on the Base Data:predev.tsf
and at 0.163 cfs on the New Data:rdout.tsf
Maximum negative excursion = 0.037 cfs (-38.9�)
occuring at 0. 095 cfs on the Base Data:predev.tsf
and at 0.058 cfs on the New Data:rdout.tsf
Peterson Consulting Engineers Page 23
Technical Information Report forWynfield Ridge May 25, 2001
• Duration
C4
M
6 ldout.dl9f <:
o target.dur
IL
C
N
j5 C 00
10 5 10 _4 10 _3 10 2 10 10°
Probability Exceedence
Wetpool Sizins•
Vr=[0.9A;+0.25Atg+O.IA«+O.OlAo](R) Where:
_[0.9(53,980)+-0.25(81,021)+0.10(19,166)](0.039) V, =Runoff Volume from Mean Annual Storm(cf)
A; =Area of Impervious Surface (sf)
= 2,759 cf A,g=Area of Till Grass (sf)
A,f=Area of Till Forest(sf)
Vb =Required Wetpool Volume (cf)
Vb=.f V, f =Volume Factor(3.0 for basic ponds)
R =Rainfall from Mean Annual Storm(ft)
= 3.0 (2,766) = 8.278 cubic feet (from KCSWDM Figure 6.4.LA)
Volume Provided in the Wetvault = 8,280 cubic feet W x 23' x 90')
Peterson Consulting Engineers Page 24
Technical Information Report forWynfield Ridge May 25, 2001
SECTION 5 CONVEYANCE SYSTEM ANALYSIS AND
DESIGN
Conveyance Calculations
The conveyance calculations were performed using the water works computer program. The
pipes were sized to convey the 25-year developed storm and checked to ensure that during the
100-year storm event the system would function adequately. The smallest pipe on site with the
least amount of slope is the pipe which must be able to handle the 100-year flow. Since all pipes
are the same size (12"), the pipe connecting catch basins 12 and 13, has a slope of 1%, this is the
pipe that will be analyzed. Flow master analyzed that this pipe could carry a maximum flow of
3.56 cfs, which is greater than the actual 100-year flow of 2.47 cfs. See next page for flow master
details. In order to accurately model the proposed conveyance system the 15-minute time step
had to be run for the developed basin. The peak flow from the time series is provided below:
Flow Frequency Analysis
Time Series File:pipe.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.616 6 2/09/01 12:30 2.47 1 100.00 0.990
0.486 7 1/05/02 15:00 1.56 2 25. 00 0.960
1.56 2 12/08/Q2 17:15 1.10 3 10. 00 0.900
0.482 8 8/26/04 0:45 0. 863 4 5. 00 0.800
1.10 3 11/17/04 5:00 0.789 5 3. 00 0.667
0.789 5 10/27/05 10:45 0. 616 6 2. 00 0.500
0. 863 4 10/25/06 22:45 0.486 7 1.30 0.231
2.47 1 1/09/08 6:30 0.482 8 1. 10 0.091
Computed Peaks 2.17 50. 00 0.980
Peterson Consulting Engineers Page 25
Technical Information Report, brWynfield Ridge May 25, 2001
Flow master analyzed that this pipe could carry a maximum flow of 3.56 cfs, which is greater than
the actual 100-year flow of 2.47 cfs. See below for flow master details.
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Outlet Riser
The outlet riser for the combined detention / wetpool facility was sized per Section 5.3.4 of the
'98 KCSVv'DM. A 12-inch diameter riser, with 0.50 feet of head can convey 2.71 CFS. The 100-
Year Developed peak flow is 2.47 CFS, therefore a 12-inch riser will be adequate.
QORInCE= 3.782 x D 2 x H 112
Where D = diameter(ft)— 1.00'
H= head (ft) —0.50'
QORMCE = 3.782 X (1.00)2 X (0.50)1'2 = 2.67 CFS
See Figure 5.3.4H Riser Inflow Curves in Appendix C.
Peterson Consulting Engineers Page 26
Technical Information Report forWynfield Ridge May 25, 2001
Downstream Conveyance Analysis
To ensure that after the locking dome grate and storm system down stream of the detention vault
could handle the 100 year flow, another analysis 15 minute time step had to be completed.
Shown below are the areas which were used when determining the 100-year flow.
Developed Conditions: Total area flowing into dome grate (CB 6) = 4.62 Acres
Impervious Surface:
Roads = 0.61 acres
13 Lots/Houses = 0.63 acres
Total Impervious = 1.24 acres
Pervious Surface:
Till Grass = 1.88 acres
Till Pasture = 0.22 acres
Till Forest = 1.28 acres
Total Pervious = 3.38
Flow Frequency Analysis
Time Series File:domegrate.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.751 6 2/09/01 12:30 2 . 81 1 100.00 0. 990
0.573 7 1/05/02 15:00 1. 80 2 25. 00 0. 960
1. 80 2 12/08/02 17 : 15 1. 19 3 10.00 0. 900
0.562 8 8/26/04 0:45 1. 01 4 5.00 0. 800
1.19 3 11/17/04 5:00 0. 906 5 3. 00 0. 667
0.906 5 10/27/05 10:45 0. 751 6 2. 00 0. 500
1.01 4 10/25/06 22:45 0. 573 7 1.30 0.231
2. 81 1 1/09/08 6: 30 0. 562 8 1. 10 0. 091
Computed Peaks 2 .48 50. 00 0. 980
After determining the 100-year flow (2.81 cfs), flow master was used to determine the maximum
capacity for the pipe. The pipe with the least slope was the pipe connecting catch basins 5 and 6,
this is a 12 inch pipe with a slope of 1%. It was found using flow master that this pipe could i Z
convey flows up to 3.56 cfs. So the conveyance system downstream has sufficient capacity to
convey the 100-year flow. See flow master details on following page. 0
m
Peterson Consulting Engineers Page 27
Technical Information Report for WynfieldRidge May 25, 2001
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SECTION 6 SPECIAL REPORTS AND STUDIES
The geotechnical report by Zipper Zeman Associates, Inc. dated February 1999 can be found in
Appendix B.
SECTION 7 OTHER PERMITS
No other permits are required at this time.
SECTION 8 ESC ANALYSIS AND DESIGN
Several standard erosion control procedures will be utilized by the contractor to minimize the
amount of erosion and sedimentation perpetuated by the construction of the site. Some of the
measures include a rock-lined construction entrance, filter fabric fence, and standard ground cover
practices. A construction sequence will be used to minimize the impacts of erosion due to
construction. A temporary sedimentation pond will be constructed, the required surface area is
calculated below, per Section D.4.5.2 of the KCSWDM:
Peterson Consulting Engineers Page 28
Technical Information Report forWynfield Ridge t1Nlay 25, 2001
Sediment Pond Sizing
SA=2 X Q2-year/ 0.00096
where SA=required surface area at top of riser
Q2-year= 0.424 cfs
SA= (2 x 0.424)/0.00096 = 883 SF
The detention pond as designed has a surface area of 1,383 SF at the top of the riser. The
permanent control structure and dewatering device will be used for the temporary facility.
Emergency Over Flow Spillway Sizing
L= [Q(looYR)/(3.21 * H 11121)] —2.4*H
L=Length of spillway(6 foot min. allowed) - see below
Q(iooyR)= 100 year developed flow - 1.10 cfs
H=Height above head - 0.2 ft
L= [1.10 /( 3.21 * ( 0.211/21) ] -2.4 * 0.2= 3.35feet
The spillway as designed has a length of 6 feet.
SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES
AND DECLARATION OF COVENANT
A bond quantity worksheet will be provided after first review. The facility summary sheet and
figure is provided in the next few pages.
Peterson Consulting Engineers Page 29
KING COUNTY,, WASHINGTON, SURFACE WATER DESIGN MANUAL
STORMWATER FACILITY SUMMARY SHEET
Development Wynfield Ridge Date 5/23/01
Location 8617 116`�Avebue SE. Newcastle. Wa
ENGINEER DEVELOPER
Name: Jennifer Steig Name: Ian Slater
Firm : Peterson Consulting Engineers Firm: Chaffey Homes
Address: 4030 Lake Washington Blvd, Suite 200 Address: 205 Lake Street South, Suite 101
Kirkland,Wa. 98033 Kirkland, Wa. 98033
Phone: 425-827-5874 1 Phone: 425-822-5981
Developed Site: 3.54 Acres Number of lots 13
Number of detention facilities on site: Number of infiltration facilities on site:
0 ponds 0 ponds
1 vaults 0 vaults
0 tanks 0 tanks
Flow control provided in regional facility(give location) Control structure located inside of detention vault
No flow control required 2 Exemption number
Downstream Drainage Basins
Immediate Major Basin
Basin A
Basin B
Basin C
Basin D
Number&type of water quality facilities on site:
0 biofiltration swale(regular/wet/or 0 sand filter(basic or large?)
continuous inflow?) 0 sand filter,linear(basic or large?)
0 combined detention/WQ pond 0 sand filter vault(basic or large?)
(WQ portion basic or large?)
1 combined detention/wetvault 0 stormwater wetland
0 compost filter 0 wetpond(basic or large?)
0 filter strip 0 wetvault
0 flow dispersion
0 farm management plan
0 landscape management plan
oil/water separator(baffle or coalescing plate?)
o catch basin inserts: Manufacturer
pre-settling pond
L pre-settling structure: Manufacturer
0 flow-splitter catchbasin
DESIGN INFORMATION INDIVIDUAL BASIN
A B C D
Water Quality design flow 0.424 cfs
Water Quality treated volume or wet and Vr 8,280 cu. ft
1998 Surface Water Design Manual 9/l/98
• 3�
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
DESIGN TOTAL INDIVIDUAL BASIN
INFORMATION,cont'd
Drainage basin(s) A B C D
Onsite area 3.64
Offsite area 0
Type of Stora e Facility Vault
Live Storage Volume 20,700 cu. ft.
Predevelo ed Runoff Rate 2-year 0.188 cfs
10- ear 0.308 cfs
100- ear 0.574 cfs
Developed runoff rate 2-year 0.424 cfs
10- ear 0.516 cfs
100- ear 1.02 cfs
Type of restrictor
Size of orifice/restriction No. 1 0.875 in.
No. 2 2.0 in
No. 3
No. 4
FLOW CONTROL&WATER QUALITY FACILITY SUMMARY SHEET SKETCH
All detention, infiltration and water quality facilities must include a sketch per the following criteria:
1. Heading for the drawings should be located at the top of the sketch(top right-hand corner).
The heading should contain:
• North arrow(point up or to left) • D9#
• Plat name or short plat number •Address(nearest)
• Date drawn(or updated) •Thomas Brothers page, grid number
2. Label CBs and MHs with the plan and profile designation. Label the control structure in writing or abbreviate
with C.S. Indicate which structures provide spill control.
3. Pipes--indicate:
Pipe size
Pipe length
Flow direction
Use s single heavyweight line
4. Tanks--use a double, heavyweight line and indicate size(diameter)
5. Access roads
• Outline the limits of the road
• Fill the outline with dots if the road is gravel. Label in writing if another surface.the 6. Or Standard Symbols:
• Bollards: • 000 moon
• Rip rap 000000
000000
Fences --x---x---x---x---x---x---
• Ditches —D-- }D-->D 4-D
7. Label trash racks in writing.
8. Label all streets with the actual street sign designation. If you don't know the actual street name, consult the
plat map.
9. Include easements and lot lines or tract limits when possible.
10. Arrange all the labeling or writing to read from left to right or from bottom to top with reference to a properly
oriented heading.
11. Indicate driveways or features that may impact access, maintenance or replacement.
9/1/98 1998 Surface Water Design Manual
3�
6'D.L.GRAVITY
DRAIN To ce B� m
v B B'C 230.00 ' R,
Iw
B'GATE VALVE gi
OUTLET RISER NOTES: __________ _______________________________________________________________________________________________
__________I. PIPE SUPPORTS h RESTRICTOR SHALL BE OF SANE MATERIAL �.^
AND BE ANCHORED A J'MAX SPACING BY J'r 0.090 BOLTS I t ..> • - r. • •.• -•. • r- •. •.. '•• 10 r .OR EMBEDDED 2"IN WALL.
2. THE RES7RICTOR SHALL BE FABRICATED MOM.060" �� � _`�
ALIMONUM•PVC CPE OR HOPE PIPE PER CITY OF NEWCASTLE ; ;
STANDARDS. I I I I
J. THE VERTICAL RISER E HORIZONTAL
OF THE TA ROUTLET I7 SHALL BE I I I a
12'SAME CIA AS THE NORIZWTAL QU71£T PIPE W/A 2-
12'DIAMf7ER. - 46'DIA CLEAR ACCESS-1I I o
4. OUTLET SHALL BE CONNECTED TO CULVERT OR SEWER PIPE W/ I j r 5 W/LADDER AT 24 FRAME - l i 2a a a a a a a a a a a
SUITABLE COUPLER OR GROUTED INTO THE BELL OF CONCRETE
PPE LID
5. E METAL QU71ET PIPE CONNECTS TO CEMENT CONCRETE PIPE, i REMOVABLE
QU1LET PIPE TO HAVE SMOOTH O.D.EQUAL 70 CONCRETE PIPE
' I.D.LESS 1/4. i ; M BAFFLE I I O R
6. FRAME h LADDER OR STEPS OFFSET SO THAT.
A)SHEAR CARE IS VISIBLE FROM TOP
0OX
OON
�M _____�____________________________ __________________�_-__�.________ �e
B)CLIMB GOWN SPACE IS CLEAR O�RISERhSHEAR CA 7E. I I _________ ________________________________ �.-_ 1001[
C)FRAME IS CLEAR OF CURB. I - - ry W i
1 7 SHEAR GATE SHALL BE gg
A)SHEAR GATE.CAST 6RCN BODY AND CA7E,OLYMPIC FDY. I i I i ' 7 IN
STD.OR EQUAL OR, I I SS 66
B)SHEAR GA IC AGINMNUM OR CAST IRON,DRAINAGE I I GRATED PANEL I I
$PECIAL71E5(SAVANNAH,CA)STD.OR EQUAL I MIN.4R CE VAULT I
j
SURFACE AREA I I
B. GATE SHALL BE D'DIA.UNLESS OTHERWISE SPECIFIED. i i , 4X(90x2J)
ti
P. GA 7E SHALL BE JOINED 70 77F SECTION By BOL 77NC i i 9285 SOFT MIN.SOFT PROVIDED
(7HR000H FLANGE)
. WELD/Na OR OTHER SECURE MEANS I I / -
i i 4B'DIA.CLEAR ACCESS 2
10.LIFT ROD:AS SPECIFIED fO MANUFACTUREW1TN HANDLE I
j W/LADDER h 24'FRAME 2 I T =
NOOK LOCK
TO WITHIN ONE FOOT OF COVER AND ADJUSTABLE i i •, 6 UD
NOG!LOCK FASTENED TO FRAME OR UPPER HANONIXD. i i `Z
- y Z
II
�i II
CLEAN-OUT ----------------- -------- ------------------------------------- -----------'--- ------- ---___--------------�_____�-----------------"-----___----------------------------__---------"
TOP TO FINISH CRADE 6' 4
6'IE I3a50 I6'PVC PEWWA70 FOD-
DRAw. S-a=(TTT) PLAN VAfW B � J r
CRATED C0MR MARKED"GRAIN' GRATED COVER MARKED VrtAIN- � v
W/BOLT LOCKWVC RING W/BOLT LOCKING RING
EL.249.5t(MATCH F/N/SH GRADE)
EL.246.50 FIWSH GRADE /��
VICE SHAALL BE LOCATED
50 THAT U`BE OVERFLOW
DEOF -A-PANEL
6'HIGH FENCE PIPE IS VISIBLE FROM GRATED COVER NARKED TRAIN' FLAT TOP O
WHERE VAULT DPENING EL. 461 .00 w/BOLT LOCKING RING `R'NWT _________
IS EXPOSED EL 246.50
r, s
I' NAX-w.S4 FL?44.ODQ O 1�J_
A 7 M TACH Of7ENMI
SHEAR CATS HANDLE u
TO 70P LADDER STEP W
ti
2"ELBOW.DIA ORIFICE z4o.zo 12.1HIpr W
z'DIA. J/4'-1 1/2' p
WASHED ROCK
(TTP.)
SUPPORTS(2"IN) POLYPROPYLENE
J x0.90'ALUMINUM W/ MANHOLE 57EPS
12"RISER .� J'AQ090 BOLTS (TYP.) ,� REMOVABLE BAFFLE W
2-1500 ti
TO CB9
12'E 2J4.OP- - . . - - - - - - - - .. - - - - - - - - . . _ - IGP OF WAI£R QUALITY EL 1N±00 V
U
SHE
T OF NEWCASILE STANDARDS 1,MINIMUM
u ,MIRAGE 11'IE 1350D 70 LL
CATE PER CITY
SEDIMENT LL
rc RSHOP DRILLED O.BBy (SEE DETAIL 7N15 SHEET) r O
ORIFICE -£L.TJI.00
EL.1J2.00 22B60 _ 2.002 -- IJ0.00 _ I_lOP CE SEDIMENT STORAGE FL IJO.00
PERFORATE T29.00 2001. ! 22B.50
FODIRC 2-
ORA1N U
2 ( ')
SECTION VIEW A-A
DETENTION VAULT DETAIL
OUTLET RISER DETAIL SCALE.' 1'-4'
g SCALE: -4• 9gg RAN
Mr' NOTE t4�'cp rA,N S
a SEE VAULT ACCESS 2 3` 4Fj a
O 6'HIGH FENCE I� PROFlLf,SHEET 10 T < to
ADJUSTA WHERE VAULT EL 24C6 •�
H I$EXPOSED
ry;l Ay �p yp•
2 O El 244.50 IONAL
W.SE.ft 244.00 s- _ _ - _ EXPIRES 09/09/02
g 'c
1 sSSIGNID AND0
ID
REMOVAB WA 77GNi UFCESs sNIIEDAND OARED
CQU U
SHEAR GATE DETAIL
NOT TO SCALE I.E(SEE RESTRICTOR 12•THICK _
N07Fc OEJAK)6'MIN. MAX W„�°ROC FRO O N SUOLT I N G
1.SHEAR DATE SHALL BE: 0 REMOVABLE
A.CAST IRON BODY AND GATE,OLYMPIC FOY,STD.,OR EQUAL OW WIN BAFFLE
oN
/N EL.2J5
B.ALUMINUM.DRAINAGE SPECIALTIES(SAVANNA•GA)SID. 12 CA END PLATE • TOP OF WATER QUAUTY EL 2J4.00
OR EQUAL - - - ; - - 4030 1Ake Washington
2.GATE SMALL Of 6'DIAMETER UNLESS 07HERIWSE SPECIFIED. ELBOW DETAIL Blvd. N.E., Suite 200
J GATE SHALL BE 0NEO 70 TEE SEC77ON BY BOLTING NOT TO SCALE Kirkland,AA 98033
(THROUGH FIANCE).WELDING.OR DINER SECURE MEANS EL 231.00 PERFORATED APPROVED FOR CONSTRUCTION Tel (425)827-5874
4.LIFT ROD: AS$P£pFlEO BY MANUFACTURER qIM HANDLES TOP OF SfDINENT STORAGE EL.13000 ,ids FOOTING Fax (425)822-7216
EXTENDED TO WITHIN ONE FOOT OFCOVER AND ADJUSTABLE DRAIN BY: lkl TE:
HOOK LOCK FASTENED TO FRAME OR UPPER HANDHOLO (Typ-) CITY OF NEW'G4STLE
3 II.S' Iy"i ms rRo n[�oAR s+an� cw. aTv'�� J09NUANER
2J ALYAKS NaT P�w� x,OQ 90 5. 6L KWF. CHAF-0008
� , »�F 9RVLP MKAIKIIPI x L,DA,�x,am IH,
SECTION B-B rMK uwurtay. IHc a^.a..vwowc max aer.wcs
+sswts Iw u+arury w Arums m nAD1 Accn..cY M
y£ SCALE: 1'-4' crssws FIg UfQ
Technical Information Report forWynfield Ridge May 25, 2001
SECTION 10 OPERATIONS AND MAINTENANCE MANUAL
The storm drainage elements requiring maintenance attention include: detention vault, Type 2
catch basin, all storm conveyance lines and Type 1 catch basins.
The following operation and maintenance guidelines applicable for the proposed storm drainage
system at Wynfield Ridge can be found in the next page.
Peterson Consulting Engineers Page 33
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 3-CLOSED DETENTION SYSTEMS(PIPES/TANKS)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Storage Area Plugged Air Vents One-half of the cross section of a vent is blocked at Vents free of debris and
any point with debris and sediment sediment
Debris and Accumulated sediment depth exceeds 10%of the All sediment and debris
Sediment diameter of the storage area for'h length of storage removed from storage area.
vault or any point depth exceeds 15%of diameter.
Example:72-inch storage tank would require cleaning
when sediment reaches depth of 7 inches for more
than'h length of tank.
Joints Between Any crack allowing material to be transported into All joint between tank/pipe
Tank/Pipe Section facility sections are sealed
Tank Pipe Bent Any part of tank/pipe is bent out of shape more than Tank/pipe repaired or replaced
Out of Shape 10%of it's design shape to design.
Manhole Cover Not in Place Cover is missing or only partially in place.Any open Manhole is closed.
manhole requires maintenance.
Locking Mechanism cannot be opened by one maintenance Mechanism opens with proper
Mechanism Not person with proper tools.Bolts into frame have less tools.
Working than inch of thread(may not apply to self-locking
lids.)
Cover Difficult to One maintenance person cannot remove lid after Cover can be removed and
Remove applying 80lbs of lift. Intent is to keep cover from reinstalled by one maintenance
sealing off access to maintenance. person.
Ladder Rungs King County Safety Office and/or maintenance person Ladder meets design standards
Unsafe judges that ladder is unsafe due to missing rungs, allows maintenance person safe
misalignment,rust,or cracks. access.
Catch Basins See"Catch Basins"Standards No.5 See"Catch Basins"Standards
No.5
1998 Surface Water Design Manual 9/1/98
A-3
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 4-CONTROL STRUCTURE/FLOW RESTRICTOR
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
General Trash and Debris Distance between debris build-up and bottom of All trash and debris removed.
(Includes Sediment) orifice plate is less than 1-1/2 feet.
Structural Damage Structure is not securely attached to manhole wall Structure securely attached to
and outlet pipe structure should support at least wall and outlet pipe.
1,000 Ibs of up or down pressure.
Structure is not in upright position(allow up to Structure in correct position.
10%from plumb).
Connections to outlet pipe are not watertight and Connections to outlet pipe are
show signs of rust. water tight;structure repaired or
replaced and works as
designed.
Any holes--other than designed holes--in the Structure has no holes other
structure. than designed holes.
Cleanout Gate Damaged or Missing Cleanout gate is not watertight or is missing. Gate is watertight and works as
designed.
Gate cannot be moved up and down by one Gate moves up and down easily
maintenance person. and is watertight.
Chain leading to gate is missing or damaged. Chain is in place and works as
designed.
Gate is rusted over 50%of its surface area. Gate is repaired or replaced to
meet design standards..
Orifice Plate Damaged or Missing Control device is not working properly due to Plate is in place and works as
missing,out of place,or bent orifice plate. designed.
Obstructions Any trash,debris,sediment,or vegetation Plate is free of all obstructions
blocking the plate. and works as designed.
Overflow Pipe Obstructions Any trash or debris blocking(or having the Pipe is free of all obstructions
potential of blocking)the overflow pipe. and works as designed.
Manhole See"Closed Detention Systems"Standards No.3 See"Closed Detention Systems'
Standards No.3
Catch Basin See"Catch Basins"Standards No.5 See'Catch Basins"Standards
No.5
9/1/98 1998 Surface Water Desi-n Manual
A-4
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 5-CATCH BASINS
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is performed
General Trash&Debris Trash or debris of more than 1/2 cubic foot which is No Trash or debris located
(Includes Sediment) located immediately in front of the catch basin immediately in front of catch
opening or is blocking capacity of the basin by basin opening.
more than 10%
Trash or debris(in the basin)that exceeds 1/3 the No trash or debris in the catch
depth from the bottom of basin to invert the lowest basin.
pipe into or out of the basin.
Trash or debris in any inlet or outlet pipe blocking Inlet and outlet pipes free of
more than 1/3 of its height. trash or debris.
Dead animals or vegetation that could generate No dead animals or vegetation
odors that could cause complaints or dangerous present within the catch basin.
gases(e.g.,methane).
Deposits of garbage exceeding 1 cubic foot in No condition present which
volume would attract or support the
breeding of insects or rodents.
Structure Damage to Comer of frame extends more than 3/4 inch past Frame is even with curb.
Frame and/or Top Slab curb face into the street(If applicable).
Top slab has holes larger than 2 square inches or Top slab is free of holes and
cracks wider than 1/4 inch(intent is to make sure cracks.
all material is running into basin).
Frame not sitting flush on top slab,i.e.,separation Frame is sitting flush on top
of more than 3/4 inch of the frame from the top slab.
slab.
Cracks in Basin Walls/ Cracks wider than 1/2 inch and longer than 3 feet, Basin replaced or repaired to
Bottom any evidence of soil particles entering catch basin design standards.
through cracks,or maintenance person judges that
structure is unsound.
Cracks wider than 112 inch and longer than 1 foot No cracks more than 1/4 inch
at the joint of any inlet/outlet pipe or any evidence wide at the joint of inlet/outlet
of soil particles entering catch basin through pipe.
cracks.
Sediment/ Basin has settled more than 1 inch or has rotated Basin replaced or repaired to
Misalignment more than 2 inches out of alignment. design standards.
1998 Surface Water Design Manual A-5 9/1/98
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 5- CATCH BASINS (CONTINUED)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is performed
Fire Hazard Presence of chemicals such as natural gas,oil and No flammable chemicals
gasoline. present.
Vegetation Vegetation growing across and blocking more than No vegetation blocking opening
10%of the basin opening. to basin.
Vegetation growing in inlet/outlet pipe joints that is No vegetation or root growth
more than six inches tall and less than six inches present.
apart.
Pollution Nonflammable chemicals of more than 1/2 cubic foot No pollution present other than
per three feet of basin length. surface film.
Catch Basin Cover Cover Not in Place Cover is missing or only partially in place.Any open Catch basin cover is closed
catch basin requires maintenance.
Locking Mechanism Mechanism cannot be opened by on maintenance Mechanism opens with proper
Not Working person with proper tools.Bolts into frame have less tools.
than 1/2 inch of thread.
Cover Difficult to One maintenance person cannot remove lid after Cover can be removed by one
Remove applying 80 lbs.of lift;intent is keep cover from maintenance person.
sealing off access to maintenance.
Ladder Ladder Rungs Ladder is unsafe due to missing rungs,misalignment, Ladder meets design standards
Unsafe rust,cracks,or sharp edges. and allows maintenance person
safe access.
Metal Grates Grate with opening wider than 7/8 inch. Grate opening meets design
(If Applicable) standards.
Trash and Debris Trash and debris that is blocking more than 20%of Grate free of trash and debris.
grate surface.
Damaged or Grate missing or broken member(s)of the grate. Grate is in place and meets
Missing. design standards.
NO. 6 DEBRIS BARRIERS (E.G.,TRASH RACKS)
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Components Maintenance is Performed.
General Trash and Debris Trash or debris that is plugging more than 20%of Barrier clear to receive capacity
the openings in the barrier. flow.
Metal Damaged/Missing Bars are bent out of shape more than 3 inches. Bars in place with no bends more
Bars. than 3/4 inch.
Bars are missing or entire barrier missing. Bars in place according to
design.
Bars are loose and rust is causing 50%deterioration Repair or replace barrier to
to any part of barrier. design standards.
M
9/1/98 1998 Surface Water Design Manual
A-6
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 7- ENERGY DISSIPATERS
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Components Maintenance is Performed.
External:
Rock Pad Missing or Moved Only one layer of rock exists above native soil in Replace rocks to design
Rock area five square feet or larger,or any exposure of standards.
native soil.
Dispersion Trench Pipe Plugged with Accumulated sediment that exceeds 20%of the Pipe cleaned/flushed so that it
Sediment design depth. matches design.
Not Discharging Visual evidence of water discharging at Trench must be redesigned or
Water Properly concentrated points along trench(normal condition rebuilt to standards.
is a"sheet flow"of water along trench). Intent is to
prevent erosion damage.
Perforations Over 1/2 of perforations in pipe are plugged with Clean or replace perforated pipe.
Plugged. debris and sediment.
Water Flows Out Maintenance person observes water flowing out Facility must be rebuilt or
Top of"Distributor" during any storm less than the design storm or its redesigned to standards.
Catch Basin. causing or appears likely to cause damage.
Receiving Area Water in receiving area is causing or has potential No danger of landslides.
Over-Saturated of causing landslide problems.
Internal:
Manhole/Chamber Wom or Damaged Structure dissipating flow deteriorates to 1/2 or Replace structure to design
Post. Baffles,Side original size or any concentrated wom spot standards.
of Chamber exceeding one square foot which would make
structure unsound.
Other Defects See"Catch Basins'Standard No.5 See"Catch Basins"Standard No.
5
1998 Surface Water Design Manual 9/1/98
A-7
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 8- FENCING
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Components Maintenance is Performed
General Missing or Broken Any defect in the fence that permits easy entry Parts in place to provide adequate
Parts to a facility. security.
Erosion Erosion more than 4 inches hich and 12-18 No opening under the fence that
inches wide permitting an opening under a exceeds 4 inches in height.
fence.
Wire Fences Damaged Parts Post out of plumb more than 6 inches. Post plumb to within 1-1/2 inches.
Top rails bent more than 6 inches. Top rail free of bends greater than
1 inch.
Any part of fence(including post,top rails,and Fence is aligned and meets design
fabric)more than 1 foot out of design alignment. standards_
Missing or loose tension wire. Tension wire in place and holding
fabric.
Missing or loose barbed wire that is sagging Barbed wire in place with less than
more than 2-1/2 inches between posts. 3/4 inch sag between post.
Extension arm missing, broken,or bent out of Extension arm in place with no
shape more than 1 1/2 inches. bends larger than 3/4 inch.
Deteriorated Paint or Part or parts that have a rusting or scaling Structurally adequate posts or
Protective Coating condition that has affected structural adequacy. parts with a uniform protective
coating.
Openings in Fabric Openings in fabric are such that an 8-inch- No openings in fabric.
diameter ball could fit through.
NO. 9- GATES
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
General Damaged or Missing Missing gate or locking devices. Gates and Locking devices in
Members place.
Broken or missing hinges such that gate cannot Hinges intact and lubed.Gate is
be easily opened and closed by a maintenance working freely.
person.
Gate is out of plumb more than 6 inches and Gate is aligned and vertical.
more than 1 foot out of design alignment.
Missing stretcher bar,stretcher bands,and ties. Stretcher bar,bands and ties in
place.
Openings in Fabric See"Fencing"Standard No.8 See"Fencing"Standard No.8
9/1198 1998 Surface Water Design Manual
A-8
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 10-CONVEYANCE SYSTEMS(PIPES & DITCHES)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
40 Component Maintenance is Performed
Pipes Sediment&Debris Accumulated sediment that exceeds 20%of the Pipe cleaned of all sediment
diameter of the pipe. and debris.
Vegetation Vegetation that reduces free movement of water All vegetation removed so water
through pipes. flows freely through pipes.
Damaged Protective coating is damaged;rust is causing Pipe repaired or replaced.
more than 50%deterioration to any part of pipe.
Any dent that decreases the cross section area of Pipe repaired or replaced.
pipe by more than 20%.
Open Ditches Trash&Debris Trash and debris exceeds 1 cubic foot per 1,000 Trash and debris cleared from
square feet of ditch and slopes. ditches.
Sediment Accumulated sediment that exceeds 20%of the Ditch cleaned/flushed of all
design depth. sediment and debris so that it
matches design.
Vegetation Vegetation that reduces free movement of water Water flows freely through
through ditches. ditches.
Erosion Damage to See"Ponds"Standard No. 1 See"Ponds"Standard No. 1
Slopes
Rock Lining Out of Maintenance person can see native soil beneath Replace rocks to design
Place or Missing(If the rock lining. standards.
Applicable).
Catch Basins See"Catch Basins:Standard No.5 See"Catch Basins"Standard
No.5
Debris Barriers See"Debris Barriers"Standard No.6 See"Debris Barriers"Standard
(e.g.,Trash Rack) No.6
NO. 11 -GROUNDS(LANDSCAPING)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
General Weeds Weeds growing in more than 20%of the landscaped Weeds present in less than 5%
(Nonpoisonous) area(trees and shrubs only). of the landscaped area.
Safety Hazard Any presence of poison ivy or other poisonous No poisonous vegetation
vegetation. present in landscaped area.
Trash or Litter Paper,cans,bottles,totaling more than 1 cubic foot Area clear of litter.
within a landscaped area(trees and shrubs only)of
1,000 square feet.
Trees and Shrubs Damaged Limbs or parts of trees or shrubs that are split or Trees and shrubs with less than
broken which affect more than 25%of the total 5%of total foliage with split or
foliage of the tree or shrub. broken limbs.
Trees or shrubs that have been blown down or Tree or shrub in place free of
knocked over, injury.
Trees or shrubs which are not adequately supported Tree or shrub in place and
or are leaning over,causing exposure of the roots. adequately supported;remove
any dead or diseased trees.
1998 Surface Water Design Manual A-9 9/1/98
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 12-ACCESS ROADS/EASEMENTS
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
General Trash and Debris Trash and debris exceeds 1 cubic foot per 1,000 Roadway free of debris which
square feet i.e.,trash and debris would fill up could damage tires.
one standards size garbage can.
Blocked Roadway Debris which could damage vehicle tires (glass Roadway free of debris which
or metal). could damage tires.
Any obstruction which reduces clearance above Roadway overhead clear to 14 feet
road surface to less than 14 feet. high.
Any obstruction restricting the access to a 10 to Obstruction removed to allow at
12 foot width for a distance of more than 12 feet least a 12 foot access.
or any point restricting access to less than a 10
foot width.
Road Surface Settlement, Potholes, When any surface defect exceeds 6 inches in Road surface uniformly smooth
Mush Spots, Ruts depth and 6 square feet in area. In general,any with no evidence of settlement,
surface defect which hinders or prevents potholes,mush spots,or ruts.
maintenance access.
Vegetation in Road Weeds growing in the road surface that are Road surface free of weeds taller
Surface more than 6 inches tall and less than 6 inches than 2 inches.
tall and less than 6 inches apart within a 400-
square foot area.
Modular Grid Build-up of sediment mildly contaminated with Removal of sediment and disposal
Pavement petroleum hydrocarbons. in keeping with Health Department
recommendations for mildly
contaminated soils or catch basin
sediments.
Shoulders and Erosion Damage Erosion within 1 foot of the roadway more than 8 Shoulder free of erosion and
Ditches inches wide and 6 inches deep. matching the surrounding road.
Weeds and Brush Weeds and brush exceed 18 inches in height or Weeds and brush cut to 2 inches
hinder maintenance access. in height or cleared in such a way
as to allow maintenance access.
9/l/98 1998 Surface Water Design Manual
A-10
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 13-WATER QUALITY FACILITIES (CONTINUED)
D.)Wetvaults
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Wetvault Trash/Debris Trash and debris accumulated in vault,pipe or Trash and debris removed from
Accumulation inlet/outlet,(includes floatables and non- vault.
floatables).
Sediment Accumulation Sediment accumulation in vault bottom that Removal of sediment from vault.
in Vault exceeds the depth of the sediment zone plus 6-
inches.
Damaged Pipes Inlet/outlet piping damaged or broken and in Pipe repaired and/or replaced.
need of repair.
Access Cover Cover cannot be opened or removed,especially Pipe repaired or replaced to
Damaged/Not Working by one person. proper working specifications.
Vault Structure Vault:Cracks wider than 1/2-inch and any No cracks wider than 1/4-inch at
Damaged evidence of soil particles entering the structure the joint of the inlet/outlet pipe_
through the cracks,or maintenance/inspection Vault is determined to be
personnel determines that the vault is not structurally sound.
structurally sound.
Baffles Baffles corroding,cracking,warping and/or Repair or replace baffles to
showing signs of failure as determined by specifications.
maintenance/inspection staff.
Access Ladder Damage Ladder is corroded or deteriorated,not functioning Ladder replaced or repaired to
properly,missing rungs,has cracks and/or specifications,and is safe to
misaligned. use as determined by inspection
personnel.
1998 Surface Water Design Manual 9/1/98
A-13
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 14- OIL CONTROL FACILITIES(CONTINUED)
A.) OW Water Separators (Continued)
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Damaged Coalescing Plate media broken,deformed,cracked and/or Replace that portion of media
Plates showing signs of failure. pack or entire plate pack
depending on severity of failure.
Damaged Pipes Inlet or outlet piping damaged or broken and in need Pipe repaired and or replaced.
of repair.
Baffles Baffles corroding,cracking,warping and/or showing Repair or replace baffles to
signs of failure as determined by maintenance/ specifications.
inspection person.
Vault Structure Cracks wider than 1/2-inch and any evidence of soil Vault replaced or repaired to
Damage-Includes particles entering the structure through the cracks, design specifications.
Cracks in Walls, or maintenance inspection personnel determines
Bottom,Damage to that the vault is not structurally sound.
Frame and/or Top
Slab
Access Ladder Ladder is corroded or deteriorated,not functioning Ladder replaced or repaired and
Damaged properly,missing rungs,cracks,and misaligned. meets specifications,and is
safe to use as determined by
inspection personnel.
Cracks wider than 1/2-inch at the joint of any inlet/ No cracks more than 1/4-inch
outlet pipe or any evidence of soil particles entering wide at the joint of the inlet/
the vault through the walls. outlet pipe.
B.) Catch Basin Inserts
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Catch Basin Sediment When sediment forms a cap over the insert media of No sediment cap on the insert
Accumulation the insert and/or unit. media and it's unit.
Trash and Debris Trash and debris accumulates on insert unit creating Trash and debris removed from
Accumulation a blockage/restriction. insert unit.Runoff freely flows
into catch basin.
Inspection Inspection of media insert is required. Effluent water from media insert
is free of oils and has no visible
sheen.
Media Insert-Water Catch basin insert is saturated with water,which no Remove and replace media
Saturated longer has the capacity to absorb. insert
Media Insert-Oil Media oil saturated due to petroleum spill that drains Remove and replace media
Saturated into catch basin. insert.
General Regular interval replacement due to typical average Remove and replace media at
life of media insert product. regular intervals,depending on
insert product.
l
1998 Surface Water Design Manual 9/1/98
A-21
APPENDIX A
99363.510
RECEIVED
City.of Newcastle File#808 3/15/00 EB
" New file name is Wynfield Ridge CITY Of.,NE` CWLE
Old file name is Avalon Ridge -
LEVEL ONE DOWNSTREAM ANALYSIS
PRELIMINARY SUBDIVISION OF
AVALON RIDGE
Preparedfor
Chaffey Corporation
205 Lake Street South #101
Kirkland, WA 98033
\ 3::i ''
T
PREPARED BY
D. R. STRONG Consulting Engineers Inc.
10604 N. E. 38th PLACE, SUITE 101, - KIRKLAND, WA 98033 - (425) 827-3063
January 25, 1999
Revised January 31, 2000
LEVEL ONE DOWNSTREAM ANALYSIS
Proposed Subdivision of
Avalon Ridge
TABLE OF CONTENTS
I. NARRATIVE
H. UPSTREAM TRIBUTARY AREA
III. SITE DRAINAGE
IV. DOWNSTREAM ANALYSIS
V. REVIEW OF EXISTING RECORDS
VI. CONCLUSION
LIST OF FIGURES
Figure Description
1 Vicinity Map
2 USGS Map
3 SCS Soils Map
4 Streams and 100-Year Flood Plain
5 Wetlands
6 Erosion Hazard
7 Landslide Hazard
8 Seismic Hazard
9 Coal Mine Hazard
APPENDICES
APPENDIX"A' DOWNSTREAM MAP & TABLE
APPENDIX"B" GEOTECHNICAL ENGINEERING REPORT
LEVEL ONE DOWNSTREAM ANALYSIS
Preliminary Subdivision of
Avalon Ridge
This report was prepared at the request of the Chaffey Corporation for the proposed plat of Avalon
Ridge' in the City of Newcastle (City). D. R. STRONG Consulting Engineers, Inc. (DRS) has prepared
this report for the exclusive use of DRS, Chaffey Corporation, and their agents, for specific application to
the residential project as described herein. Use or reliance on this report, or any of its contents for any
revisions of this project, or any other project, or by others not described above, is forbidden without the
expressed permission by DRS.
L NARRATIVE
This Level One Drainage Analysis has been prepared for inclusion in a preliminary subdivision
application. It has been prepared in accordance with Core Requirement #2, Off-Site Analysis (Section
1.2.2) of the 1998 King County Surface Water Design Manual (SWDM). The proposed project will
subdivide one parcel (4.40 acres) into twelve individual lots for single-family residences. The project site
(Site) is located on the west side of 116th Ave SE between SE 84th Street and SE 85th Lane in the City
of Newcastle, in Section 32, Township. 24 North, Range 5 East, W.M. (see Figure 1, Vicinity Map).
The Site and downstream field evaluation was conducted on November 11, 1998 under cloudy and dry
weather conditions. A second field visit was conducted on January 21, 1999 following several weeks of
rainy weather, to confirm and update the previous observations. Weather conditions were overcast and
dry. A third field visit was conducted on January 26, 2000 following several weeks of cold, rainy
weather, to confirm and update the information gathered from the previous years. Weather conditions
were overcast, cold and dry.
The pre-developed Site consists of a single-family residence with several outbuildings (4,750 sf total roof
area). A large concrete driveway/walkway/deck area connects the house and outbuildings (16,072 total
area). The west portion of the Site is undeveloped and consists of light forest with dense underbrush. A
swale conveys runoff' to the natural discharge point. The west property line adjoins 112th Ave SE,
currently undeveloped. The surrounding parcels are developed with single family residences.
H. UPSTREAM TRIBUTARY AREA
In evaluating the upstream area we reviewed the City and USGS topographic maps, made field
observations, and prepared a detailed topographic survey map. It appears that the Site's upstream basin
area was approximately 5.73 acres in size (see Figure 2) prior to development. However, only the west
half of 116th Ave SE adjacent to the Site, and a portion of the lots adjacent to the south and north
property lines, appear to contribute runoff to the property. Drainage from the east perimeter of 116th
Ave SE (approximately 2 acres) is intercepted by a roadside ditch and is routed into a series of culverts
and catchbasins away from the Site. Therefore the actual upstream tributary area is approximately 3.73
acres.
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
1
FIGURE 1
VICINITY MAP
6 IT 1law
Mal
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IT
uzEcwoo Sf C N. [ r SE oo 0
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SE
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rg
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1 '28TH PL�•�,z,.,. ...-.�- _iT(-•4.:•r ° _ �-K-
TH ST --
NE" 2B .. '.. Vr..
0 "1 Poo s7£aaA
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p
i '.F 7' Pr, f>M sr NEIpITS
APARK t 25r1
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six s<.:i Y'a i q♦ oa sr
� d'nttU >f;3700 :,•(fi �� < NE NO % 'LlCM7t�S"�r ` a E
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IIsi: fY�'a T N sTT lath /
+ G'�Vlr'ld' K 5 sT•a'1� :` ! 'lf =•e too zsoo. ,Sj' P
o `� v. < l �ST o a t a :kr IsEhos,x 3 e#a r; NE 2
N! i,}"l
lLl� !���� :�' ► •• ^t t i. > ,Nil Ur
q �1, ; j,z ',�♦ �w�1 �NL� !. PARK•w-- C� �I�f 1 .iht - ::1I .:aP
♦ i i %' 'r'1. .1N� h� RL .E. .c ••. . ...al,sfi'•. ,a,} 'j�r��. .i AL.
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
2
M. SITE SOILS
A review of the SCS Soils map indicates Alderwood gravelly sandy loam (AgC and AgD) in the eastern
three-fourths, and Ragnar-Indianola (RdE) in the western quarter of the Site (see Figure 3). Alderwood
gravelly sandy loam is in Hydrologic Soil Group C and has moderately high runoff potential. Ragnar-
Indianola is in Hydrologic Soil Group AB and has low to moderately low runoff potential. Soils
exploration work conducted by Zipper-Zeman Associates confirmed the presence of these soils on-site
(see Geotechnical Engineering Report).
IV. DOWNSTREAM ANALYSIS The downstream analysis is further illustrated and detailed in the Downstream Map and Downstream
Table enclosed in Appendix`B".
The downstream analysis began at a point approximately 65 feet south of the northwest property line.
Runoff leaves the Site as shallow concentrated flow, then becomes undefined as it crosses unimproved
}} _E. We observed a slight, shallow concentrated flow dtscfiarg>ng westerly from the Site onto
the propQje
AXces-Freliminary Short Plat. Runoff continues west in an undefined flowpath through light
forest with underbrush to an 18" plastic pipe culvert on the east margin of Monterey Place NE.
At this point a`roadside_ ditch.-joins the downstream path, carrying runoff from_the _east margin of
nte Morey Place NE We observed a very s ig lit ow to e roa side ditch. This ditch contributes
approximate) 9y o/ f the total flow entering the culvert, while the Site contributes the remaining 10%. Z
There were no obvious problems observed at the culvert inlet.
. Q
Flow continues westerly beneath Monterey Place NE via the 18" pipe and joins a roadside ditch on th R1
west margin of the road. The-�uTvert transitions to an 18" corTcrete pipe at rts outfaIl. The ditch extends
south (upstream) along the west margin of Monterey Place NE.
The ditch is trapezoidal with dense blackberry vines. We noted slight erosion and no channel protection.
Approximately 90% of the total ditch flow is from the upstream area on the west margin of Monterey
Place NE. At the time of analysis, there was a light flow within this ditch. Flow continues northwesterly
in the ditch, then veers west across private property within a trapezoidal channel.
This channel is approximately 2-3' wide and 6-8" deep as it flows through the bottom of a broad forested
ravine with houses on both sides. The channel steps down across exposed tree roots and fallen limbs,
flowing westerly, then into a ponded area apparently formed by underground seeps. We noted signs of
erosion and minor flooding within the channel.
The flowpath meanders via braided channels past the ponded area, then becomes more defined as the
slope increases continuing west. The channel is 1-2' wide and 6-36" deep. There is evidence of incision
and erosion along this portion of the flow path. In conversations with the owner, he stated that this
problem did not exist until the construction of the Whitehawk Development upstream.
Level One Downstream Analysis-Avalon Ridge January 3 1,2000 99363
3
The channel discharges to a 12" LCPE pipe located on the east margin of Lincoln Ave NE. At this point
a roadside ditch along the east margin of the road joins the downstream path. The ditch has no channel
protection, and was not flowing at the time of the most recent analysis. We observed indications of
minor flooding at the pipe inlet.
The 12" LCPE conveys the runoff northwesterly to a Type 1 catchbasin (CB#1) with a solid cover,
located on the east margin of Lincoln Ave NE in the gutter flow line. During the two previous analyses,
CB#1 was accessible. However, we were unable to locate this catch basin during our most recent field
visit. The catch basin may have been removed or buried during recent construction activities on Lincoln
Ave NE. Runoff is discharged west via a 12" LCPE to a Type 2 catchbasin (CB#2), grated cover, on the
west margin of Lincoln Ave NE in the gutter flow line.
CB42 has two inlets. The first is the above mentioned 12" LCPE and the other is a 12" LCPE from the
roadside ditch to the south, on the west margin of Lincoln Ave NE. Flow is discharged northerly via a
12" LCPE to a Type 1 catchbasin (CB#3).
CB#3 has a grated cover and is located in the gutter flow line on the west margin of Lincoln Ave NE.
Flow discharges northerly from CB#3 via a 12" LCPE into a roadside ditch on the west margin of
Lincoln Ave NE.
The 12" LCPE outfall has rip rap protection. At this point, an 18" LCPE joins the downstream path from
a catchbasin located on the east margin of Lincoln Ave NE. The 18" LCPE contributes approximately
10% of the total flow discharging to the ditch. The roadside ditch is densely vegetated, and has straw
bales staked at intervals along its length. The ditch discharges to a beveled end, 30" concrete pipe.
There was no debris rack at the pipe inlet. The 30" concrete pipe conveys flow northerly beneath a
driveway entrance and discharges into a Type 2 catch basin (CB#4).
CB#4 has a grated cover and is located in the gutter flow line of the driveway entrance to the
Williamsburg Townhomes/Condominiums. Flow discharges northerly from CB#4 via a 30"LCPE into a
trapezoidal channel located on the west margin of Monterey Place NE. There is a rock headwall at the
pipe outlet.
The channel meanders northerly through light forest with dense underbrush, and is approximately 3-5'
wide and 12"- deep. A 36" LCPE from the east margin of Lincoln Ave NE joins the flowpath
approximately 35 ft. downstream from the 30" LCPE outfall. Flow continues northerly within the
channel to a point where the flowpath diverges. There is a ponded area here with a rock headwall and
what appears to be an emergency overflow inlet to a 36" LCPE. The inlet is protected by reinforced
metal plates and sandbags. This overflow apparently conveys peak flows northeasterly to the east/north
margin of Lincoln Ave NE/NE 44" Street. There was a very slight flow in the overflow pipe at the time
of the analysis. The main flow continues northerly in a rock lined trapezoidal channel for the remainder
of the quarter mile from. the Site. The downstream analysis terminates at this point where the proposed
project Site constitutes a minimum of 15% of the total tributary drainage area, and the point is at least
one-quarter mile downstream from the Site.
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
4
FIGURE 2
USGS MAP
BM
•, .cf,
�� � •ass -_ r'•1 t�, .. '� � � '
;. GS
41,
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
5
� b .
T" s.
.+rY 641 y f�;C 7�Ui•'14M i7Mfq� \\ � - I
r
-
A.
•s'
•Raf'C fIy _ rs f' 4.� y I I p �l .,1 •
.L •c,,. �ti' -E.s�b�4?' i + ;�:iij�I �� '� — --- of I I I
V. REVIEW OF EXISTING RECORDS
Included are sections of the King County Sensitive Areas Map Folio, which indicate the following:
• Streams: No streams are shown within the area of concern, (see Figure 4). However, the City of
Renton topographic map indicates an intermittent drainage course in the western third of the Site, and
several others within the area. Our review confirmed the existence of a swale in the western portion
of the Site.
• Wetlands: May Creek Wetland #9 is located approximately 1/2 mile upstream from the Site but does
not discharge towards the Site. Lake Washington is located approximately one mile downstream
from the Site (see Figure 5).
• Erosion Hazard: An erosion hazard is shown on the lower (western) portion of the Site, (see Figure
6). This will require a Notice on Title.
• Landslide Hazard: None shown, (see Figure 7).
• Seismic Hazard: None shown, (see Figure 8).
• Coal Mine Hazard: None shown, (see Figure 9).
VI. CONCLUSION
There was a very slight flow observed discharging from the Site into the 18" cross culvert beneath
Monterey Ave NE. Recent new developments upstream (south) from the 18" cross culvert, and
upstream (south) from the 12" cross culvert beneath Lincoln Ave SE, appear to be the primary cause of
problems noted along the downstream path. Runoff from these areas apparently contributes to the
erosion and incision observed. The roadside ditches on Monterey Ave NE and Lincoln Ave SE have no
channel protection, and are inclined at approximately 6% or greater. Therefore, channel velocities may
be too high, causing incision and erosion downstream.
The project proposes to add approximately 48,144 s.f of new impervious surface within the eastern half
of the Site. Furthermore, runoff control will be provided per the 1998 King County Surface Water
Design Manual. The post-developed 2-year and 10-year, 24-hour storms will be released at their
predeveloped rates (Level One Flow Control criteria). Therefore, the proposed project should have
minimal impact on the downstream properties.
Level One Downstrcam Analysis-Avalon Ridge January 31,2000 99363
7
FIGURE 4
STREAMS & 100-YEAR FLOODPLAINS
` 1
F.
y iJ
~ '` i. .•i 1_r i- 1 .fit'.,,;••, .�.
+ SITEt �L
3.
AI
t
q
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
8
FIGURE 5
WETLANDS
Lo
,' , � ;,M- � .�• � •� �\�:�"tCoal eras s.
rWaMrngton
r,
S"~ SITE
t
Washington
14,
d v _ L F• :i `F .. _"!Washi g•Ofl..^t Fj E �o r 24P
{{
:v � 'jj -�--�I� '—.' ' ''`•^fir' � `s_�' -1 1�.
ri
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
9
FIGURE 6
EROSION HAZARD AREAS
QjTE
'L/.w��• : :moo •;• .� + ,
�r` ass . � .ate + I c ., �. t•� _ I '
_ z'v [ —`ti►. �y rw- .1,-.r�� I .a� _ -� r �.r.1 - �� ���~*yYx•�1yk �
�1.� .L .i' i�61 _o:Li.. � w".�h.i� .1.�PLp':f�••`�'~ �>•� ^�
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
10
FIGURE 7
LANDSLIDE HAZARD AREAS
••�..31�M�: P1z'�• ; nr-% .., 1 •1 l ;-` �' H lI. f''F
zj
tb
1 ` 1 :ya •:;� � -Y ';Tt"S1w � •. _ '� y.( .•a���Yti ,�/-• <�
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\�"/',� ti r FT \�..�� t 1� //�1,_< .?� '`t �• � LL.��.J-I ` 1 �7/f' 1.1 .•!"�• .'�` , i'��+
1 �� ,� 'i•• 1� `o• .,.. *f A '�' s � " 1 I, �I -.F. z I '1 t 1;�
Level One DuwTmtream Analysis-Avalon Ridge January 31,2000 99363
I1
1
FIGURE 8
SEISMIC HAZARD AREAS
� ' :•�t 4.t'y�.J i�t, she'- 1�'S� p
i y i`•' {' � L 1 / r ,t .may
SiTE
Ic
i � L t.+l;l `„ \ '�11:• inn)la.r ,,� � l -L {1 ��... �� ��`4I � 1
�r `
i'. •:;�.`,. .. �.1^�••a.• � s �a -"".`A�l. ti'� .....r `'••. ^.r�,..r_. .�•i! '� f 7H 1 - t
Jj-
Level One Downstream Analysis-Avalon Ridge January 31,2000 99363
12
lY Y i • l: !' i t!' 110
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APPENDIX "A"
DOWNSTREAM TABLE & MAP
t
Surface Water Design Manual, Core Requirement #2
................................ .........
............. ..........................
................
... .......
...........................
.........
..........
. .. ........ .............. .......................
.... ............................ ............. .... .. .......
.............. ...
.......... ............
T'
....... ........ ....... ......
........ .............
.................
..................
..... ... . ..... . ....
Vt� 31, .0
.. ..................... ........
.... . ...... ................. .
d
A-B SHALLOW CONC.FLOW, UGHT FOREST WITH LIGHT GROUND 30 0-120, NONE OBSERVED NONE ANTICIPATED ONSITE STREAM BECOMES UNDEFINED AS IT
UNDEFINED PATH VEGETATION CROSSES IlTmAVE SE,THROUGHKEES
I SHORT PLAT TO MONTEREY PLACE NE
BC 18"PIPE,PLASTIC AT CULVERT UNDERNEATH MONTEREY PL NE 5 120-230' NONE OBSERVED NONE ANTICIPATED APPROXIMATELY 90%OF FLOW INTO
INLET,CONC.AT OUTLET FLOWS WESTERLY CULVERT IS FROM UPSTREAM AREA ON EAST
SIDE OF MONTEREY PLACE NE,SITE
CONTRIBUTES 10%OF FLOW,VERY SL10HT
FLOW FROM ROADSIDE DITCH
C-D ROADSIDE DFI'CH,WEST RUNOFF FLOWS NORTHWEST TTIROUGH 15 230-250' VEGETATION REDUCED CAPACITY APPROXIMATELY 90%OF FLOW IN DITCH Is
)ASRGLN1 OFMONTEREY DENSE BLACKBERRY VINES THROUGHOUT PARTIALLY BLOCKS DUE TO LACK OF FROM UPSTREAM AREA ON WEST MARGIN OF
PLACE NE DITCH CHANNEL MAINTENANCE MONTEREY PLACE NE,LIGHT FLOW IN DITCH
D-E I'"IEZ01DA-L CHANNEL RUNOFF FLOWS WEST-NORTHWEST 15-10% 250-300' EROSION ALONG MORE EROSION DRAINAGE PATH STEPS DOWN ACROSS
2-3-I-r.WIDE,6-8"DEEP THROUGH LIGHT FOREST WITI I LIGHT SIDEWALLS, EXPOSED ROOTS AND FALLEN BRANCHES
WITIUN BROAD RAVINE GROUND VEGETATION ACCUMULATION OF
SEDIMENT ALONG
FLOW PATH
E-F PONDED AREA WITH FLOW IS WEST-NORTHWEST THROUGH LIGHT 2 300-340' REDUCED CAPACITY MINOR FLOODING IN PONDED AREA APPEARS TO BE FROM
BRAIDED CHANNELS FOP-EST WITH LIGHT GROUND VEGETATION DUE TO HEAVY RAVINE DUE TO GROUNDWATER SEEPS
WrITHN BROAD RAVINE AND SMALL POOLS CREATED BY FALLEN VEGETATION PEAK FLOWS AND
TREES AND LIMBS REDUCED CAPACITY
F-0 TRAPEZOIDAL CHANNEL FLOW MEANDERS WEST-NORTHWEST VARIES 340-620' INCISED CHANNEL, INCREASED EROSION INDICATIONS OF RECENT MINOR FLOODING
I-2-FT.WIDE,6-36" THROUGH LIGHT FOREST WITH LIGHT 10-2% SCOURING AND MINOR FLOODING IN
DEEP WITHIN BROAD GROUND VEGETATION AND FALLEN TREES EROSION WITHIN RAVINE DUE TO THE
RAVINE CHANNEL, ACCUMULATION OF
ACCUMULATION OF SEDIMENT
SEDIMENT ALONG
FLOW PATH
G-H PIPE FLOW FLOW TO NORTHWEST TO CB#1 5 620-650' EVIDENCE OF MINOR INCREASED EROSION SILT APPEARS TO BE PRIMARILY FROM
12"LCPF FLOODING UPSTREAM AREA ON EAST SIDE OF LINCOLN
AVE NE
CBn 1,TYPE I ON EAST MARGIN OF LINCOLN AVE NE 0 650' UNABLE TO LOCATE INACCESSABILITY OF OUTLET IS BEVELED CPEP TO WEST BENEATH
CATCHBASIN, CB DUE TO RECENT CATCH BASIN LINCOLN AVE NE TO cB#2
SOLID COVER WATERMAIN
INSTALLATION AND
OTHER
CONSTRUCTION
ACTIVITIES,CB MAY
HAVE BEEN
REMOVED
H-1 PIPE FLOW FLOW TO WEST UNDERNEATH LINCOLN AVE 5 650-680' NONE OBSERVED NONE ANTICIPATED
12"LCPE NE
I CB#2,TYPE 2 ON WEST MARGIN OF LINCOLN AVE NE IN 0 680' NONE OBSERVED NONE ANTICIPATED SECOND INLET FROM SOUTH(ROAD SIDE
CATCHBASIN, GUTTER FLOW LINE DITCH FOR LINCOLN AVE NE)
GRATED COVER
I-I PIPE FLOW FLOW TO NORTH ALONG LINCOLN AVE NE 10 680-822' NONE OBSERVED NONE ANTICIPATED
12"LCPE
I CB#3,TYPE I NORTH OF DRIVEWAY APRON,ALONG 0 822' NONE OBSERVED NONE ANTICIPATED
CATCHBASIN, GUTTER FLOW LINE
GRATED COVER
I-K PIPE FLOW FLOW TO NORTH TO OUTFALL AT ROADSIDE 2 822-842' NONE OBSERVED NONE ANTICIPATED RIP RAP PROTECTION PROVIDED AT OUT-FALL,
12"LCPE DITCH STRAW BALES STAKED IN PLACE ALONG
CHANNEL, 18"LCPE FROM CB ON EAST
MARGIN OF LINCOLN A VE NE
K-L TRAPEZOIDAL ROADSIDE VEGETATED WITH HIGH GRASS -5 842-967' NONE OBSERVED NONE ANTICIPATED RIPRAP INLET PROTECTION
DITCH,2-3'DEEP
L-M PIPE FLOW FLOW TO NORTH UNDERNEATH DRIVEWAY 10 967-1032' NO TRASH RACK AT TRASH AND LARGE
BEVELED END,30"CONC. TO WILLIAMSBURG TOWNHOMES/CONDOS INLET DEBRIS COULD
PIPE OBSTRUCT PIPE
M CB#4,TYPE 2 CATCH IN GUTTER FLOW LINE 0 1032' NONE OBSERVED NONE ANTICIPATED
BASIN,GRATED COVER
M-N PIPE FLOW FLOW TO NORTH 10 1032-1072' NONE OBSERVED NONE ANTICIPATED HEADWALL PROTECTION AT OUTLET
30"LCPE
N-O MEANDERING FLOW TO NORTH-NORTHEAST THROUGH VARIES 1072-1300' INCISION INCREASED INCISION CHANNEL IS APPROXIMATELY 30 FT.FROM
TRAPEZOIDAL CHANNEL, DENSE UNDERBRUSH,ALONG EAST SIDE OF AND EROSION NEW BUILDINGS AT CLOSEST PONT;36"
WIDTH VARIES WILLIAMSBURG TOWNHOMES/CONDOS LCPE FROM EAST SIDE OF LINCOLN AVE NE
DISCHARGES TO CHANNEL APPROXIMATELY
35 FT.FROM OUIFALL OF 30"LCPE
0 OVERFLOW POOL 36"LCPE OVERFLOW INLET PROTECTED BY 0 1300' UNDERMINING OF DESTABILIZATION OF OVERLOW IS NOT IN MAIN STREAM CILANNFI.,
REINFORCED STEEL PLATES AND SANDBAGS ROCK HEADWALL ROCK HEADWALL. ROCK HEADWALL PROTECTION AT
OVERFLOW
O-P TRAPEZOIDAL CHANNEL ROCK LINED,24"WIDE AT BOTTOM,2:1 12 1300-1320' NONE OBSERVED NONE ANTICIPATED APPEARS TO CARRY MAIN STREAM FLOW
SIDESLOPES,MODERATE FLOW OBSERVED
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it
AVALON RIDGE SUBDIVISION
DOWN I -� STREAM MAP
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APPENDIX B
SECTION 5.3 DETENTION FACILITIES
Riser Overflow
The nomograph in Figure 5.3.4.H can be used to determine the head (in feet) above a riser of given
diameter and for a given flow (usually the 100-year peak flow for developed conditions). l
FIGURE 5.3.4.11 RISER INFLOW CURVES
100 72 54 48
42
i
or
000.36 f
t
33
t
30
27 00000 f
1000
24
00000
50000,
21 ��
a0000,
= H
18 w f
y
2 t �
10 i
1 5
w s
M WOO
000
U
U
C3 1 2
.00
10
YL
a�I -
Z
t
0.1 o,s 10
HEAD IN FEET (measured from crest of riser)
Q,,e;r=9.739 DHsn
Q orifice=3.782 D 2 H 1/2
Q in cfs, D and H in feetr
Slope change occurs at weir-orifice transition
9/1/98 1998 Surface Water Design Manual
5-50
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oft asTLift-
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APPENDIX C
Zipper Zeman Associates, Inc.
- Geotechnical and Environmental Consulting
J-257
February 11, 1999
D.R. Strong Consulting Engineers, Inc.
10604 NE 38th Place, Suite 101
Kirkland, Washington 98033
Attention: Mr. Patrick Chelin
Subject: Subsurface Exploration and Geotechnical Engineering Evaluation
Proposed 116th Avenue SE Plat
Newcastle, Washington
r
Dear Mr. Chelin:
Zipper Zeman Associates, Inc. (ZZA) is pleased to present herein our geotechnical
engineering report for the above-referenced project. This report presents the results of our
subsurface exploration and geotechnical engineering evaluation relative to foundation and
construction considerations, as well as slope stability considerations for the project site.
The purpose of the evaluation was to establish general surface and subsurface conditions
at the site from which conclusions and recommendations regarding foundation design and
construction considerations could be formulated, and to address slope stability considerations
along the west side of the project site. The scope of our work consisted of completing 5
backhoe-excavated test pits, a visual reconnaissance, laboratory testing, geotechnical enl7ineering
analysis, and preparation of this report. For purposes of preparing this report, we have assumed
that site grades will remain essentially as shown on the topographic survey by D.R. Strong dated
December 17, 1998 and enclosed with this report. In the event of any changes in the nature,
design, or location of the proposed structures, the conclusions and recommendations presented in
this report should be reviewed and modified, if necessary, to reflect the changes. We
recommend that ZZA be allowed the opportunity to review the plans and specifications of the
project once they become available to determine that the recommendations presented herein have
been properly interpreted with respect to this project. This report has been prepared in
accordance with generally accepted geotechnical engineering practices for the exclusive use of
Mr. Dan Sanchez, D.R. Strong Consulting Engineers, Inc., and their agents, for specific
application to this project.
SITE AND PROJECT DESCRIPTION
The project site is located northwest of the intersection of SE 88th Street and 116th
Avenue SE at 11514 SE 85th Lane in Newcastle, Washington. The parcel is approximately 6 to 7
acres in size and is currently occupied by a single-family residence, a carport, and several
outbuildings. The home is a wood-frame, single-story structure. The site is bordered to the
north by residential development, the south by SE 85th Lane and additional residential
19231 -36"Avenue W,quite 3201 Lynnwood, `,V snin.on 99036 425)771 -3304
Proposed 116th Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 2
development, to the west by the 112th Avenue SE right-of way, and to the east by 116th Avenue
SE.
Site topography slopes downward to the west from 116th Avenue SE with topographic
relief of approximately 146 feet across the entire length of the parcel. Topographic relief across
the proposed development area is limited to about 30 feet. A portion of the western margin of
the development area is comprised of slopes mapped as being steeper than 40 percent. Another
small area near the 112th Avenue SE right-of-way is also mapped as having slopes steeper than
40 percent.
Based upon preliminary site plans, we understand that the proposed development will
consist of constructing 10 single-family residential lots with associated access roads and utilities.
Finished floor elevations and grading plans were not provided at the time of our evaluation. The
buildings would be sited on the eastern, flatter portion of the site.. It is our understanding that
there is no construction proposed on the approximate western half of the property where slopes
vary from about 15 to 40 percent, except for the installation of a stormwater spreader trench.
The proposed locations of the lots, as well as the approximate locations of the explorations
accomplished for this study, are shown on the Site and Exploration Plan, Figure 1. Once
building elevations and grading plans are finalized, we recommend that ZZA be allowed to
review the plans in order to determine that the recommendations presented herein are suitable for
the proposed design and have been correctly interpreted. Lots 1 and 2 will be of primary interest
due to the anticipated grading in that area as well as the existing fill present on Lot 2.
GEOTECHNICAL EXPLORATION AND SUBSURFACE CONDITIONS
The subsurface exploration program conducted for this study consisted of completing
five test pit excavations (TP-1 through TP-5) across the site. Locating the test pit excavations
was based upon the referenced preliminary topographic survey and measuring from existing site
features. The test pits were completed to depths ranging from 9 to 10 feet below the existing
ground surface on December 29, 1998 by a local excavation company under subcontract to our
firm. The approximate locations of the test pit excavations are presented on Figure 1, the Site
and Exploration Plan.
An experienced engineer from our firm continuously observed and logged the subsurface
conditions encountered in the test pit excavations. The soils were visually classified in the field
and representative samples .were collected and returned to our office for further visual
classification and laboratory testing. The test pit logs presented in this report describe the
vertical sequence of soil types encountered and observed in the excavations.
Subsurface Conditions
The subsurface soil conditions revealed by the test pit excavations were relatively
consistent with respect to soil type and density except for the area including most of Lot 2. In
general, the near-surface geology transitions from loose to medium dense, fine to medium sands
Zipper Zeman Associates, Inc.
19231—36'Avenue W.,Suite B201 Lynnwood,Washington 98036 (425)771-3304
Proposed 116t°Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 3
with varying proportions of silt in the topographically higher, western portion of the site to
medium dense to dense, silty sand with some gravel (glacial till) in the eastern portion of the site.
More specifically, test pits TP-1 and TP-2 encountered about 9 inches of loose, wet,
brown, organic-rich topsoil over loose grading to medium dense, moist, light brown grading to
gray, fine to medium sand with varying proportions of silt. These excavations extended to a
depth of 91/2 feet below existing grades. Between 21/2 and 4 feet, 9 inches of topsoil underlain
by a layer of dense silty sand with some gravel was encountered in test pit TP-2. In test pits TP-
3, TP-4, and TP-5, medium dense to dense, moist to wet, orange-brown and light brown grading
to gray, silty sand with some gravel was encountered to depths of 8, 61/2, and 3 feet,
r' respectively. These soils were interpreted to be weathered grading to unweathered glacial till.
The dense glacial till typically has high strength and low compressibility characteristics due to its
depositional history. Below the glacial till, dense, fine to medium sand with varying proportions
of silt was encountered to the full depths explored. At the time of the subsurface evaluation, we
did not observe any surficial ponded water or signs of environmental contamination. Our scope
of work did not include sampling or testing soil for potential environmental contaminants.
The western portion of Lot 2 was not accessible for evaluation at the time of our
evaluation. Based on the slope configuration on the west side of the lot, it appears that some
undocumented fill exists in this area. We anticipate that the fill is on the order of a few feet
thick. It is our interpretation that the existing building currently situated on the proposed
property line between Lots 1 and 2 was built in a cut to construct a daylight basement. This cut
gives the appearance that the western portion of Lot 2 may have significantly more fill. At the
time of site development, we recommend that ZZA be allowed to further evaluate the extent and
thickness of fill in this area.
Soil descriptions presented in this report are based on the subsurface conditions
encountered at specific test pit locations across the site. Variations in subsurface conditions may
exist between the test pit locations and the nature and extent of variations between the
explorations may not become evident until construction. If variations then appear, it may be
necessary to reevaluate the recommendations of this report.
Groundwater
t :
Perched groundwater seepage was encountered in all of the test pit excavations, except
TP-1, at the time the explorations were completed. Perched groundwater conditions should be
expected to develop following periods of prolonged precipitation at the transitions between the
medium dense and dense glacial till soils as well as above siltier zones within the fine to medium
sands. Percolation of the rainfall into the soil will be precluded at the interface between the
medium dense soils and the less permeable, underlying dense soils. Under such conditions,
perching will develop and groundwater will begin to flow laterally under the influence of
gravity.
It should be noted that groundwater conditions and soil moisture contents are expected to
vary with changes in season, precipitation, site utilization, and other on- and off-site factors.
Given the relatively dense nature of the soils a few feet beneath the existing ground surface,
Zipper Zeman Associates, Inc.
192 3 i —36'Avcnuc W..Suiic B201 Lynnwood,Washington 98036 (425)171-3304
Proposed I I6`h Avenue SE Plat J-257
Newcastle,Washington February 11, 1999
Page 4
perched groundwater conditions should be expected to develop following periods of prolonged
precipitation.
Seismic Criteria
Figure 16-2 presented in the 1997 Uniform Building Code classifies the subject site as
being within Seismic Zone 3. Based on the subsurface conditions encountered at the site and
published geologic literature, it is our opinion that a Soil Profile Type of Sc be used to describe
the average properties within the upper 100 feet of soil beneath the site. This designation
describes soils that are considered very dense with a shear wave velocity of 1,200 to 2,500 feet
per second, Standard Penetration Test values greater than 50, and an undrained shear strength
greater than 2,000 psf.
Steep Slope, Landslide, and Erosion Considerations
The southwest portion of Lot 2 appears to meet the common definition of a steep slope.
Steep slopes are typically defined as any ground that rises 10 or more feet in 25 feet of horizontal
distance and are at least 10 feet in height. The existing steep slope is moderately vegetated and
shows no visible signs of instability. The native soils which comprise the slope consist of loose
to medium dense grading to dense fine to medium sand and silty sand with some gravel which, in
our opinion, are stable under current slope configurations and vegetative cover. At this time,
rainfall either percolates into the ground or becomes surficial runoff. It is our opinion that
drainage conditions above the slope will be improved by the connection and tightlining of all
runoff from impervious surfaces.
Development of the site during winter months would not increase the risk of instability or
erosion of the steep slope in the southwest portion of Lot 2 provided that concentrated runoff is
_ not allowed to discharge down the slope. The vegetation on the slope will not be disturbed, and
all runoff from the construction area can be directed away from the steep slope. There are no
apparent existing springs or seepage zones present on this slope.
It is our opinion that the proposed development with a minimum 25-foot set back from
the steep slope area in the southwest portion of Lot 2 would not create a landslide or erosion
hazard to the subject property or surrounding properties.
Erosion and sedimentation controls are recommended during construction to reduce the
potential impacts to adjacent ,areas. Erosion control measures should be designed to prevent
sediment transport. This may be accomplished by constructing water bars or utilizing other
methods to control surface water runoff, and constructing silt fence to control sedimentation. If
construction is accomplished during the winter months, we further recommend that temporary
erosion protection be provide consisting of covering exposed soil areas with plastic sheeting
and/or straw.
CONCLUSIONS _-ND RECOMMENDATIONS
Zipper Zeman Associates. Inc.
19231—36"Avcnuc W.,Suitc 8201 Lynnwood, Washington 99036 (425)771-3304
Proposed 116`h Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 5
We anticipate that the proposed development will utilize wood frame construction above
reinforced concrete, cast-in-place, foundations, as well as concrete slab-on-grade floors. Based
upon the subsurface exploration program, the project appears feasible utilizing shallow
foundation support.
Site Preparation
We anticipate that this project will require minor cuts and fills to establish the access road
and building pad grades. Site preparation should include the removal of all vegetation, root
mass, organic soils, existing structures, undocumented fill material (if any), and any deleterious
debris from building and paving areas, or those locations where "structural fill" is to be placed.
Preparation for site grading and construction should begin with procedures intended to drain any
ponded water and control surface water runoff. It will not be possible to successfully utilize on-
site soils as "structural fill" if accumulated water is not drained prior to grading, or if drainage is
not controlled during construction. Attempting to grade the site without adequate drainage
control measures will reduce the amount of on-site soil effectively available for use, increase the
amount of select import fill materials required, and ultimately increase the cost of the earthwork
and foundation construction phases of the project
Following clearing and grubbing, organic-rich silty sand and sandy silt topsoil will need
to be stripped in the building and pavement areas, as well as those areas to receive structural fill.
Topsoil thickness are anticipated to be about 9 inches in these areas. Localized areas of deeper
organics, such as root systems, may be encountered within the project site and should likewise be
removed. Any excavations that extend below finish grades should be backfilled with structural
fill as outlined subsequently in this report. In our opinion, the topsoil is not suitable for reuse as
structural fill and should therefore be exported from the site or used for landscaping purposes.
After stripping of the topsoil is completed, the exposed soils will generally consist of silty
sand. After stripping, and prior to placement of structural fill, we recommend that foundation,
floor subgrade, sidewalk, pavement, and areas to receive structural fill be proofrolled and
compacted to a firm and unyielding condition in order to achieve a minimum compaction level
of 90 percent of the modified Proctor maximum dry density as determined by the ASTM:D-1557
test procedure. Due to the silty nature of the near-surface soils, proofrolling and adequate
compaction can only be achieved when the soils are within approximately —_ 2 percent of the
optimum moisture content. Soils which appear firm after stripping may be proof-rolled with a
heavy compactor, loaded double-axle dump truck, or other heavy equipment under the
observation of a qualified geotechnical engineer, or his representative. This observer will assess
the subgrade conditions prior to filling. Areas where loose surface soils exist due to grubbing
and stripping operations should be excavated to the depth of the disturbance and backfilled with
structural fill. The need for or advisability of proofrolling due to soil moisture conditions should
determined at the time of construction. We recommend that a representative of our firm observe
the soil conditions prior to and during proofrolling to evaluate the suitability of stripped
subgrades prior to fill placement.
Earthwork may be difficult or impossible during periods of elevated soil moisture and
wet weather due to the moisture sensitive nature of the fine-grained soils. Excavated site soils
Zipper Zeman Associates, Inc.
192,31—360'Avenuc W.,Suitc B201 Lynnwood,Washington 98036 (425)'171-3304
Proposed 116"'Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 6
may not be reusable as structural fill depending on the moisture content and weather conditions
-- at the time of construction. If soils are stockpiled for future reuse and wet weather is anticipated,
the stockpile should be protected with plastic sheeting that is securely anchored. If on-site soils
become unusable, it may become necessary to import clean, granular soils to complete wet
weather site work.
Subgrade soils that become disturbed due to elevated moisture conditions should be
overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted
structural fill. We recommend that the earthwork portion of this project be completed during
extended periods of dry weather if possible. If earthwork is completed during the wet season it
may be necessary to take extra precautionary measures to protect subgrade soils. Wet season
earthwork may require additional mitigative measures beyond that which would be expected
during the drier summer and fall months. This could include diversion of surface runoff around
exposed soils, draining of ponded water on the site, and collection and rerouting of groundwater
seepage from upgradient on- and off-site sources. Once subgrades are established, it may be
necessary to protect the exposed subgrade soils from construction traffic. Placing 2 to 4 inch
quarry spalls, crushed recycled concrete, or clean pit-run sand and gravel over these areas would
further protect the soils from construction traffic. Materials considered suitable for subgrade
protection are described in the following sections of the 1998 WSDOT/APWA Standard
Specifications for Road, Bridge, and Municipal Construction:
9-03.9(1) Ballast*
9-03.9(3) Base Course*
9-03.11 Recycled Portland Cement Rubble*
9-03.18 Foundation Materials Class C*
* These material specifications should be modified so that the percent passing the U.S. No. 200
sieve is less than 5 percent based upon the fraction passing the U.S. No. 4 sieve.
Structural Fill
All fill material placed in building, pavement, and non-landscaped areas should be placed
in accordance with the recommendations herein for structural fill. Prior to placement, the
surfaces to receive structural fill should be prepared as previously described. All structural fill
should be free of organic material, debris, or other deleterious material. Individual particle size
should be less than 6 inches in diameter.
Structural fill should be placed in lifts no greater than 8 inches in loose thickness and
each lift should be compacted to at least 90 percent of the modified Proctor maximum dry
density as determined by the ASTM:D-1557 test procedure. Within building areas and for the
Lipper two feet below the subgrade in pavement areas, the structural fill should be compacted to
at least 95 percent of ASTM:D-1557. We recommend that a ;eotechnical engineer, or his
representative, be present during grading so that an adequate number of density tests may be
conducted as structural fill placement occurs. In this way, the adequacy of the earthwork may be
evaluated as it proceeds. In the case of roadway and utility trench filling and wall backfilling in
Zipper Zeman Associates, Inc.
19231—36"Avcnuc W..Suice B201 Lynnwood,Washington 98036 (425)771_3304
Proposed 116" Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 7
municipal rights-of-way, the backfill should be placed and compacted in accordance with current
local codes and standards.
Permanent fill slopes should be constructed no steeper than 2H:1V. If the slopes are
exposed to prolonged rainfall before vegetation becomes established, the surficial soils will be
prone to erosion and possible shallow sloughing. Surficial repairs, such as armoring affected
areas with quarry spalls, may be necessary until vegetation is established.
When the ground surface slopes more than 4H:1V beneath proposed fills, the fill should
be keyed and benched in suitable native soils per the minimum requirements of UBC, Volume 1,
Section 33.3.2, Preparation of Ground. We recommend that all benches be at least 5 feet wide
and the key at the toe of the fill be at least 8 feet wide and 4 feet deep.
The suitability of soils for structural fill use depends primarily on the gradation and
moisture content of the soil when it is placed. As the amount of fines (that soil fraction passing
the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in
moisture content and adequate compaction becomes more difficult, or impossible, to achieve.
Generally, soils containing more than about 5 percent fines by weight (based on that soil fraction
passing the U.S. No. 4 sieve) cannot be compacted to a firm, non-yielding condition when the
moisture content is more than a few percent from optimum. The optimum moisture content is
that which yields the greatest soil density under a given compactive effort.
At the time of the limited subsurface evaluation, the site soils disclosed by the
explorations appeared to have moisture contents at or above their optimum moisture content
relative to their possible use as structural fill. However, soil moisture conditions should be
expected to change throughout the year. Most of the site soils contain a significant fine-grained
fraction. Consequently, use of the on-site soil as structural fill will require that strict control of
the moisture content be maintained during the grading process. Selective drying of over-
optimum moisture soils may be achieved by scarifying or windrowing surficial materials during
dry weather. Soils which are dry of optimum may be moistened through the application of water
and thorough blending to facilitate a uniform moisture distribution in the soil prior to
compaction.
In the event that inclement weather or wet site conditions prevent the use of on-site soil
or non-select material as structural fill, we recommend that a "clean", free-draining pit-run sand
and gravel be used. Such materials should generally contain less than 5 percent fines, based on
that soil fraction passing the U.S. No. 4 sieve, and not contain discrete particles greater than 6
inches in diameter. It should be noted that the placement of structural fill is, in many cases,
weather-dependent. Delays due to inclement weather are common, even when using select
granular fill. We recommend that site grading and subsurface utility work be scheduled for the
drier months, if at all possible.
It is our opinion that structural fill could be placed on Lots 1 and 2 in the area of an
existing building Aith a daylight basement. This area appears to have been cut in the past to
establish the grades for the daylight basement.
Zipper Zeman Associates,Inc.
19231—36"Avcnue W.,Suac B201 Lynnwood,Washington 98036 (425)771-3304
Proposed 116''Avenue SE Plat J-257
Newcastle,Washington February 11, 1999
Page 8
Utility Trenching and Backfilling
We recommend that utility trenching, installation, and backfilling conform to all
applicable Federal, State, and local regulations such as WISHA and OSHA regulations for open
excavations.
In order to maintain the function of any existing utilities, we recommend that temporary
excavations not encroach upon the bearing splay of existing utilities. Likewise, utility
excavations should not encroach upon the bearing splay of footings or floor slabs. The bearing
splay of existing structures and utilities should be considered to begin 3 feet away from the
widest point of the pipe or foundation and extend downward at a 1H:1V slope. If, due to space
constraints, an open excavation cannot be completed without encroaching on a utility, we
recommend shoring the new utility excavation with a slip box or other suitable equipment.
We recommend that utility subgrades be firm, unyielding and free of all soils that are
loose, disturbed, or pumping. Such soils should be removed and replaced with compacted
structural fill. After a firm subgrade has been established, we recommend that a minimum of 3
inches of bedding material be placed in the trench bottom. Bedding material for rigid and plastic
pipe should conform with Sections 9-03.15 and 9-03.16, respectively, of the 1998
WSDOT/APWA Standard Specifications for Road, Bridge, and Municipal Construction. We
further recommend that all bedding material extend at least 4 inches above utilities that require
protection during subsequent trench backfilling. All trenches should be wide enough to allow for
compaction around the haunches of the pipe. Otherwise, materials such as controlled density fill
(CDF) or pea gravel could be used to eliminate the required compaction around the pipe.
Backfilling the remainder of the trenches could be completed with on-site soils if they
can be compacted to the minimum levels recommended in the Structural Fill section of this
report. Wet soils excavated from the trenches could only be used as backfill by reducing the
moisture content to within a few percent of optimum. We recommend that all utility trench
backfill beneath slabs and pavements be density tested in order to determine that the backfill has
been compacted in accordance with the approved plans and specifications.
Temporary and Permanent Cut Slopes
Temporary slope stability is a function of many factors, including the following:
1. The presence and abundance of groundwater;
2. The type and density of the various soil strata;
3. The depth of cut;
4. Surcharge loadings adjacent to the excavation;
5. The length of time the excavation remains open.
It is exceedingly difficult under the variable circumstances to pre-establish a safe and
"maintenance-free" temporary cut slope angle. Therefore, it should be the responsibility of the
contractor to maintain safe slope configurations since the contractor is continuously at the job
site, able to observe the nature and condition of the cut slopes, and able to monitor the subsurface
Zipper Zeman Associates, Inc.
19231—36i°Avenue W.,Suite B201 Lynnwood.Washington 98036 (425)771-3304
Proposed 1166 Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 9
materials and groundwater conditions encountered. It may be necessary to drape temporary
- slopes with plastic or to otherwise protect the slopes from the elements and minimize sloughing
and erosion. We do not recommend vertical slopes or cuts deeper than 4 feet if worker access is
necessary. The cuts should be adequately sloped or supported to prevent injury to personnel
from local sloughing and spalling. The excavation should conform to applicable Federal, State,
and local regulations.
According to Chapter 296-155, Part N, Excavation Trenching and Shearing, of the
Washington Administrative Code (WAC), it is our opinion that the soils encountered at the site
would be classified as Type B soils. According to the Code, excavations less than 20 feet deep
in Type B soils may be cut at a maximum temporary slope angle of 45 degrees (IH:IV). We
recommend that temporary cuts exposed to inclement weather be covered with sheet plastic to
reduce the risk of erosion and destabilization.
We recommend all permanent cut slopes be designed at a 2IJ:1 V inclination or flatter. It
has been our experience that the permanent slopes steeper than 2H:1 V will tend to ravel and
slough to a flatter inclination over time. In addition, with the steeper slopes, topsoil erodes
readily and it is more difficult and takes longer to establish vegetation for slope protection.
Shallow Foundations
All footings should be founded within the medium dense to dense native soils, or within
compacted structural fill which extends down to the medium dense to dense native soils.
Footings should not be founded on or within loose or disturbed native soil, topsoil, or the
existing fill material unless it has been evaluated by the geotechnical engineer. Continuous or
column footings may be designed for a maximum allowable bearing pressure of 2,000 psf.
Foundation members founded within structural fill compacted to 95 percent relative density
(ASTM:D-1557) may also utilize a maximum allowable bearing pressure of 2,000 psf. A one-
third increase of these bearing pressures may be used for short-term wind or seismic loading.
For building and retaining wall foundations, we recommend using an allowable base friction
value of 0.35 and a maximum allowable passive resistance of 250 pcf(pounds per cubic foot) for
those foundations embedded at least 18 inches below finish grades. Exterior footings should
extend at least 18 inches below adjacent grade for frost protection, while interior footings should
extend at least 12 inches below adjacent grade. We also recommend that all foundations be set
back at least 5 feet horizontally from the face of any slope. This distance should be measured
from the side of the footing horizontally to the slope face. We recommend that all continuous
and isolated footings be at least 18 and 24 inches in width, respectively.
We estimate that the total settlement of foundation members founded within the medium
dense and dense silty sand soils may approach 3/4 inch. Differential settlement of foundations
founded within the same soil type could approach 1/2 inch. Settlements would occur elastically
as the loads are applied. If possible, we recommend that the foundation elements be placed
within the same soil type to minimize the magnitude of possible differential settlement. It should
be noted that differential settlement could approach the total settlement values if adjacent
footings are founded on different bearing strata. At the time this report was written, final design
information regarding foundation or floor grades was not available. Consequently, we cannot
Zipper Zeman Associates, Inc.
19231—36'Avenue W., Suite 3201 Lynnwood, Washington 98036 (425)771-3304
Proposed 116`h Avenue SE Plat )-257
Newcastle,Washington February 11, 1999
Page 10
comment conclusively regarding the anticipated bearing conditions of foundations at specific
locations. Foundation settlement is oftentimes a function of the condition of the footing
excavation subgrade. Footing excavations should be free of loose or soft soil, slough, debris, or
water prior to pouring footing concrete.
The high sensitivity of the silty site soils to disturbance may require that the footing
excavations be covered with a lift of crushed rock or a lean concrete "mud mat" to minimize
disturbance of the bearing surface during construction in wet weather. Under no circumstances
should footings be cast atop loose or soft soil, slough, debris, or surfaces bearing standing water.
We recommend that a qualified geotechnical engineer, or his representative, from our firm
observe the condition of the footing subgrades prior to the pouring of concrete, or a lean concrete
mud mat, in order to verify that the bearing soils are undisturbed and that conditions are
consistent with the recommendations contained within this report.
We recommend that the structures be protected by a perimeter footing drain. The drain
should consist of a minimum 4-inch diameter perforated pipe embedded in at least a 18-inch
thick envelope of clean, free-draining granular material, such as pea gravel. Footing drains
should be directed toward appropriate storm water drainage facilities. Roof drains should not be
connected to the footing drains.
Backfilled Walls
All backfill placed behind walls or around foundation elements should be placed in
accordance with our recommendations for structural fill except that import fill will be necessary
for wall backfill. The following recommended earth pressures, presented as equivalent fluid
weights, are based on the assumption of a uniform level granular backfill with no buildup of
hydrostatic pressure behind the wall. To minimize lateral earth pressures and prevent the
buildup of hydrostatic pressures, the wall backfill should consist of a free-draining granular
material coupled with a perforated pipe drain placed at the base of the wall backfill, similar in
configuration to that described for the perimeter footings. All backfill within 24 inches of the
wall should contain less than 5 percent fines, based on the portion passing the U.S. No 4 sieve.
If the backfilled walls are structurally restrained from lateral movement at the top, we
recommend that they be designed for an "at-rest" equivalent fluid weight of 50 pounds per cubic
foot (pcf). If the tops of the walls are free to move laterally in an amount equal to at least 0.1
percent of the wall height during placement of backfill soils, they may be designed for an
"active" equivalent fluid weight of 35 pcf.
Surcharges due to sloping ground, adjacent footings, vehicles, construction equipment.
etc., must be added to these values. The above equivalent fluid pressures assume that the
backfill was compacted to approximately 90 percent of the modified Proctor maximum dry
density. Additional compaction adjacent to the wall will increase the earth pressure, while a
lesser degree of compaction could permit post construction settlements.
The utility trenches may act as french drains by intercepting perched groundwater
seepage. Some of these utility trenches may lead to the proposed houses and subject them to
additional moisture, if basements are constructed. Therefore, it is Iiighly recommended that the
Zipper Zeman Associates, Inc.
19231 —36'Avenue W.,Suac B201 Lynnwood, Washington 98036 (425)771-3304
a
Proposed 116t`Avenue SE Plat J-257
Newcastle,Washington February 11, 1999
Page I 1
wall backfill consist of free-draining aggregate as recommended herein. Footing drains should
be constructed at elevations below all wall penetrations and preferably at footing elevations.
Additionally, trench dams should be constructed at suitable locations in the utility trenches to
minimize the flow of water in the trench backfill toward the houses.
Floor Slab Support
j.
The subgrades for floor slabs should be prepared in accordance with the previous site
preparation recommendations. The floor slabs should be founded on prerolled or compacted
native ground or structural fill compacted to 95 percent relative density (ASTM:D-1557). We
recommend that slabs be underlain by a minimum 4-inch thickness of compacted crushed rock.
In floor slab areas where moisture sensitive floor coverings are planned, an impermeable
membrane ( e.g., polyethylene sheet) should be placed over the base course to reduce the
migration of moisture through the concrete slab. The impermeable membrane should be
protected by two inches of fine, moist sand placed both above and below the membrane. The
sand cover should provide protection for the membrane and should promote uniform curing of
the slab concrete. The sand cover should be moistened and tamped prior to slab placement.
Construction Considerations
The native soils that will be exposed upon completion of stripping contain a significant
percentage of fine-grained particles. These silty soils are susceptible to disturbance, particularly
when wet. We recommend that the contractor make every effort to minimize disturbance of
stripped surfaces. These efforts may include directing surface water away from open
excavations and the placement of a crushed rock or concrete mud slab surface in the footing
trench excavations. If site work is accomplished in wet weather, the placement of clean sand and
gravel below paved areas would promote future drainage and improve subgrade support. In
addition, vehicle traffic over wet subgrades or prepared areas should be minimized. Application
of these measures will reduce the likelihood of additional overexcavation of disturbed soils and
associated costs for export and import will be reduced.
Pavement Design Recommendations
The subgrade soils are anticipated to generally consist of silty sand and fine to medium
sand that is rated as a fair to good subgrade material with an estimated field California Bearing
Ratio (CBR) value ranging from 10 to 20 percent based on the unified Soil Classification of SM.
An estimated CBR value of 15 was used for pavement design due to the silty nature of the soil
and the likelihood that some asphalt will be supported on structural fill. In order to use this CBR
value, all fill used beneath the pavement must have support characteristics at Ieast equivalent to
the on-site silty sand soils and must be placed under compacted structural fill conditions.
The following recommendations assume that the subgrade and any structural fill will be
prepared in accordance with the recommendations presented in this report. The top 12 inches
beneath the pavement should be compacted to a minimum of 95 percent relative compaction
using ASTM:D-1557 as a standard. Specifications for pavements and crushed base/top course
Zipper Zeman Associates, Inc.
19231—36'Avenue W.,Suite B201 Lynnwood,Washington 98036 (425)771-3304
Proposed 116 h Avenue SE Plat J-257
Newcastle, Washington February 11, 1999
Page 12
could conform to specifications presented in Division 9, Materials, of the 1998 WSDOT/APWA
Standard Specifications for Road, Bridge, and Municipal Construction. In lieu of crushed gravel
base/top course, asphalt treated base (ATB) can be substituted. ATB could be utilized to provide
a wearing surface during design construction and protect the subgrade soils that would otherwise
be subjected to construction traffic. Some degradation of the ATB in areas subjected to repeated
and/or concentrated equipment traffic should be anticipated. Degraded areas would require
removal and repair prior to paving with Class B asphalt. We recommend a minimum asphalt
pavement section consisting of 2 inches of Class B asphalt over 4 inches of crushed aggregate
base course. The crushed aggregate base course could be substituted with 3 inches of ATB.
Crushed aggregate base course should meet the requirements presented in Section 9-
03.9(3) of the WSDOT Standard Specifications. Asphalt concrete pavement should be Class B
as described in Sections 5-04 and 9-03.8 of the Standard Specifications. Asphalt Treated Base
(ATB) should conform to Sections 4-06.3, 5-04, and 9-03.6 of the Standard Specifications.
Stormwater Spreader Trench
Current plans are to discharge stormwater from the plat in a spreader trench which will be
located in the sloping area downhill from the western margin of Lots 1 and 2. This approach is
expected to be feasible and is not expected to affect the stability of the slope provided that the
spreader trench is properly positioned and that vegetation is reestablished after construction.
We recommend that the spreader trench be constructed in the gently sloping area that is
located just west of the steep slope area at the southwest corner of Lot 2. In this gently sloping
area, existing slopes appear to be inclined at about 5H:1 V. We recommend that a minimum
setback of 30 feet be maintained between the spreader trench and the toe of the steep slope area
on Lot 2.
It is important that vegetation which is disturbed during installation of the spreader trench
be restored at the completion of construction.
CLOSURE
The conclusions and recommendations presented in this report are based on the
explorations accomplished for this study. The number, location, and depth of the explorations
for this study were completed within the site and scope constraints of the project so as to yield
the information necessary to formulate our recommendations. Some of the plans for this project
were in the preliminary stage at the time this report was written. Under the circumstances, it is
recommended that we be provided the opportunity for general review of the project plans and
specifications in order to confirm that the recommendations and design considerations presented
in this report have been properly interpreted and implemented into the project design package.
The integrity and performance of the foundation systems at this site depend greatly on
proper site preparation and construction procedures. Field judgement by a qualified engineer
will be necessary in order to determine the adequacy of the site drainage and foundation support
systems. Therefore, because of our familiarity with the site soils, we recommend that Zipper
Zipper Zeman Associates, Inc.
19231—36i°Avenue W.,Suite B201 Lynnwood, Washington 98036 (425)771-3304
Proposed 116`h Avenue SE Plat J-257
Newcastle,Washington February 11, 1999
Page 13
Zeman Associates, Inc. be retained to provide geotechnical engineering services during the
earthwork and foundation construction phases of the project. If variations in the subsurface
conditions are observed at the time of construction, we would be able to provide additional
geotechnical engineering recommendations to the contractor and owner in a timely manner as the
project construction progresses. If other engineering or soil inspection firms are used during
earthwork, we recommend that the transfer of responsibility be completed in accordance with
Volume 1, Section 3317.9 of the Uniform Building Code.
We appreciate this opportunity to be of service to you, and would be pleased to discuss
the contents of this report or other aspects of the project with you at your convenience.
S 3 THoM A Respectfully submitted, -
t wASy, IS Zipper Zeman Associates, Inc.
n f v
Thomas A. Jones, P.E.
Associate
E;PIrtES '/3/2000
James B. Thompson, P.E.
Principal
Enclosures: Figure 1 - Site and Exploration Plan
Test Pit Logs TP-1 through TP-5
Zipper Zeman Associates. Inc.
19231 —36'Avenue `.V..Suac 3201 Lynnwood,Washing[on 98036 (425)771-3304
r-:
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APPENDIX A
FIELD EXPLORATION PROCEDURES AND LOGS
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ZIPPER ZEINLAN ASSOCIATES IN
GEOTECHNICAL AND ENVIRONMENTAL
w CONSULTING HIC SURVEY",PREPARED 61 U.R.STRONG CONSULTING
FIELD EXPLORATION PROCEDURES AND LOGS
J-257
Our field exploration program for this project included 5 test pit excavations completed
on December 29, 1998. Approximate exploration locations are shown on the Site and
Exploration Plan, Figure 1. Exploration locations were estimated by pacing from existing site
features and referencing existing features on and around the site. As such, the exploration
locations should be considered accurate to the degree implied by the measurement method. The
following sections describe our procedures associated with the explorations. Descriptive logs of
the explorations are enclosed in this appendix.
Test Pit Explorations
An independent contractor working under subcontract to our firm excavated the test pits
using of a rubber-tired backhoe. An experienced geotechnical engineer from our firm
continuously observed the test pit excavations, logged the subsurface conditions, and obtained
representative soil samples. The samples were stored in moisture tight containers and
transported to our laboratory for further visual classification and testing. After we logged each
test pit, the operator backfilled each with excavated soils tamped into place. Some settlement of
the backfill should be expected over time.
The enclosed test pit logs indicate the vertical sequence of soils and materials
encountered in each test pit, based primarily on our field classifications. Where a soil contact
was observed to be gradational or undulating, our logs indicate the average contact depth. We
estimated the relative density and consistency of in situ soils by means of the excavation
characteristics and by the sidewall stability. Our logs also indicate the approximate depths of
any sidewall caving or groundwater seepage observed in the test pits, as well as all sampling
locations.
Test Pit Lots J-257
Page 1
Depth (feet) Soil Group Material Description
Classification
(Symbol)
Test Pit TP-1
0.0—0.8 SM/ML Loose, wet, dark brown, silty sand and sandy silt (topsoil
with roots throughout).
0.8—2.0 SM Loose to medium dense, moist, light brown, silty fine to
medium sand.
2.0—4.0 SM Medium dense, moist, grayish to light brown,fine to
medium sand with some silt.
4.0— 9.5 SP Medium dense, moist, gray, fine to medium sand with trace
silt.
Test pit completed at 9.5 feet on 12/29/98
Disturbed samples obtained at 3.0 and 6.0 feet.
No groundwater seepage observed.
Moisture content of sample at 3.0 and 6.0 feet measured at
10.7 and 12.2 percent, respectively.
Test Pit TP-2
0.0 - 0.8 SM /ML Grass over loose, wet, dark brown, silty sand with sandy
silt (topsoil).
0.8 — 2.5 SM Medium dense, moist to wet, light brown, silty fine to
medium sand.
2.5 —4.0 SM Dense, moist, light brown, silty sand with some gravel
(glacial till-like).
4.0 — 9.5 SP Medium dense, moist, gray, fine to medium sand with trace
silt.
Test pit completed at 9.5 feet on 12/29/98
Disturbed soil sample obtained at 2.0 feet.
Slight caving observed between 0.0 and 6.0 feet.
Slight groundwater seepage observed between 6.0 and 6.5
feet.
Moisture content of sample at 2.0 feet measured at 17
percent.
Test Pit Lots J-257
Page 2
Depth (feet) Soil Group Material.Description
Classification
S bol
Test Pit TP-3
0.0—0.8 SM/ML Grass over loose, wet, dark brown, silty sand and sandy silt
(topsoil).
0.8 —2.5 SM Medium dense, wet to saturated, orange-brown grading to
light brown, silty fine to medium sand (weathered glacial
till).
2.5 — 8.0 SM Dense,moist, gray, silty sand with some gravel (glacial
till).
8.0—9.0 SP Dense, moist, gray, medium sand with trace silt.
Test pit completed at 9.5 feet on 12/29/98
Disturbed samples obtained at 1.5.
Moderate groundwater seepage observed between 2.0 and
3.0.
Moisture content of sample at 1.5 feet measured at 19.7
percent.
Test Pit TP-4
0.0 - 0.8 SM i ML Loose, wet, dark brown, silty sand and sandy silt (topsoil).
0.8 — 3.5 SM Medium dense, wet to saturated, orange-brown to light
brown, silty sand with some gravel (weathered glacial till).
3.5 — 6.5 SM Dense, moist, gray, silty sand with some gravel (glacial
till).
6.5 — 9.5 SP Dense, moist, gray, medium sand.
Test pit completed at 9.5 feet on 12/29/98
Slight to moderate groundwater seepage observed between
3.5 and 4.5 feet and between 6.0 and 7.0 feet.
x
Test Pit Lots J-257
Page 3
Depth (feet) Soil Group Material Description
Classification
S bol
Test Pit TP-5
0.0—0.8 SM /ML Grass over loose, wet, dark brown, silty sand and sandy silt
(topsoil).
0.8 — 3.0 SM Medium dense, wet, light brown, silty sand with some
gravel (weathered glacial till).
3.0— 10.0 SM-SP Dense, moist, gray-tan, fine to medium sand with some silt
interbedded with dense, moist tan-gray silty sand with
some gravel.
Test pit completed at 10.5 feet on 12/29/98.
Disturbed sample obtained at 10.0 feet.
Slight perched groundwater seepage observed at 3.0 feet.
Moisture content of sample at 10.0 feet measured at 12.2
percent.
APPENDIX B
LABORATORY TESTING PROCEDURES AND RESULTS
LABORATORY TESTING PROCEDURES
J-257
A series of laboratory tests were performed during the course of this study to evaluate
_ the index and geotechnical engineering properties of the subsurface soils. Descriptions of the
types of tests performed are given below.
Visual Classification .
Samples recovered from the explorations were visually classified in the field during the
exploration program. Representative portions of the samples were carefully packaged in
moisture tight containers and transported to our laboratory where the field classifications were
verified or modified as required. Visual classification was generally done in accordance with the
Unified Soil Classification system. Visual soil classification includes evaluation of color,
relative moisture content and soil type based upon grain size. Soil classifications are presented
on the exploration logs in Appendix A.
Moisture Content Determinations
Moisture content determinations were performed on representative samples obtained
- from the explorations in order to aid in identification and correlation of soil types. The
determinations were made in general accordance with the test procedures described in ASTM:
D-2216. The results are shown on the exploration logs in Appendix A.
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