05-0770 Drain and Erosion Report 0424081
SAMANTHA RIDGE
Drainage and Erosion
Control Report
Prepared for: Jack Long
The One Eleven Building
Auburn, WA 98002
(253) 846-5756
April 10, 2008
Prepared by: Pete Swan
Reviewed by: Jeff McInnis, PE
PETRA ENGINEERING, LLC
535 Dock Street, Suite 213
Tacoma, WA 98402
(253) 752-7617
Project No: 06-036
Project Name: SAMANTHA RIDGE
Storm Report -Samantha Ridge.doc
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TABLE OF CONTENTS
I. FACILITY SUMMARY FORM ................................................................................ ..................3
II. PROJECT ENGINEER'S CERTIFICATE .............................................................. ..................7
III. DRAINAGE REPORT ............................................................................................. ..................8
Section 1 -Project Description .......................................................................... .................8
Section 2 -Existing Conditions .......................................................................... .................8
Section 3 -Infiltration Rates/Soils Report .......................................................... .................8
Section 4 -Wells and Septic Systems .............................................................. ..................8
Section 5 -Fuel Tanks ...................................................................................... ..................9
Section 6 -Sub-basin Description .................................................................... ..................9
Section 7- Analysis of 100-Year Flood ............................................................. ..................9
Section 8 -Aesthetic Considerations ................................................................ ..................9
Section 9 -Facility Sizing and Downstream Analysis ....................................... ..................9
Section 10 -Covenants, Dedications, and Easements .................................... ................10
Section 11 -Property Owners Association Articles of Incorporation ................ ................10
Section 12 -Other Permits or Conditions Placed on the Project ..................... ................10
Section 13 -Bond Quantities and Declaration of Covenant ............................. ................10
IV. EROSION CONTROL PLAN ................................................................................ .................11
Section 1 -Construction Sequence and Procedure ......................................... ................11
Section 2 -Soil Stabilization and Sediment Trapping ...................................... ................11
Section 3 -Permanent Erosion Control and Site Restoration .......................... ................12
Section 4 -Geotechnical Analysis and Report ................................................. ................12
Section 5 -Inspection Sequence ...................................................................... ................12
Section 6 -Control of Pollutants other than Sediments ................................... .................12
Section 7 -Utilities ............................................................................................ ................12
Appendix A -Vicinity Map, Drainage Exhibits, FEMA Map and LOMA
Appendix B -Hydraulic Analysis
Appendix C -Geotechnical Report
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I. FACILITY SUMMARY FORM
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4 Proponent's facility name or identifier (e.g., Pond A):
Name of road or street to access facility:
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Hearings Examiner case number:
~ Development Review Project No. /Bldg. Permit No.:
~ Parcel Number(s):
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P
art 1 -Project Name and Proponent
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Detention Pond
Crystal Springs Road NW
#15854-001-01
22719240600
Project name: Samantha Ridge
~" Project owner: Jack Lon
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P' Project contact: PETRA Engineering
W Address: 535 Dock Street -Ste. 213 Tacoma, WA 98402
P Phone: (253) 752-7617
~ Project proponent (if different):
Address:
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Phone:
Project engineer: Pete Swan
Firm: PETRA Engineering
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Phone number: (253) 752-7617
SS~.A~~THl1 RIDvc
Q4.1 C.Q8
Part 2 -Project Location
Section ............................. 19
Township ......................... 17
Range .............................. 02
Names and addresses of adjacent property owners:
Floyd Cummings (North) 614 Crystal Springs Rd. Yelm, WA 98597
Pacific Frontier, LLC (East) 406 Crystal Springs Rd. Yelm, WA 98597
Clarke Properties, LLC (South) 404 Railroad Ave SE Yelm, WA 98597
Ryan 8~ Tami Pearson (South) 404 Edwards St. SW Yelm, WA 98597
Troy Truong (South) 402 Edwards St. SW Yelm, WA 98597
Michael Killion (West) 15744 Coates Rd. Yelm, WA 98597
Part 3 -Type of Permit Application
Type of permit (e.g., commercial building):
Other permits (~):
^ DOF /W HPA
^ COE Wetlands
^ FEMA
^ Shoreline Management
^ Encroachment
^ Other
^ COE 404
^ DOE Dam Safety
^ Floodplain
^ Rockery/Retaining Wall
® Grading
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Other agencies (Federal, State, Local, etc.) that have or will review this Drainage and Erosion Control
Plan: None
Part 4_- Proposed Project Description
What stream basin is the project in (i.e., Clover): Yelm Creek
Project Size, acres 4.12 Acres
Zoning :......................... R-6
On-site:
Residential Subdivision:
Number of lots .................................................................... 29 Units
S4{:r':fi.NTHA ~I~vc.
Lot size (average, acres) .................................................... NIA
Building Permit/Commercial Plat:
Building(s) (footprint, acres) ............................................... 0.44 Acres
Concrete paving (acres) ..................................................... 0.28 Acres
Gravel surface (acres) ........................................................ NIA
Lattice block paving (acres) ............................................... NIA
Public roads-including gravel shoulder (acres)............ 0.25 Acres (off-site)
Private roads-including gravel shoulder (acres) .......... 0.33 Acres
On-site impervious surface total (acres) ....................... 1.05 Acres
Part 5 -Pre-developed Project Site Characteristics:
Stream through site (y/n) ......................................Yes
Name ................................................... Yelm Creek
Shoreline Designation ......................... Urban
Type of feature this facility discharges to (i.e., lake, stream, intermittent stream, pothole, roadside ditch,
sheettlow to adjacent property, etc.): Spreader Trench
GROUND
Swales (y/n) ....................................................... ......... N
Steep slopes-steeper than 10% (y/n) ................ ......... N
Erosion hazard (y/n) .......................................... ......... N
100-year floodplain (y/n) ................................... .......... Y
Wetlands (y/n) ................................................... .......... N
Seeps/springs (y/n) ........................................... .......... N
High groundwater table (y/n) ............................ .......... N
Creek ............................................................... .......... Y
Part 6 -Facility Description
Total area tributary to facility (acres) ..................................... ......... 1.30 Acres
Total off-site area tributary to facility (acres) .......................... ......... 0.25 Acres
Total on-site area tributary to facility (acres) ......................... ......... 1.05 Acres
Design impervious area tributary to facility (acres) ................ ......... 1.30 Acres
Design landscaped area tributary to facility (acres) ............... ......... 0.00 Acres
Design total tributary area to facility (acres) .......................... ......... 1.30 Acres
jAP~'r".'v`THA RI~G~ C4.1G.~8 PAGE :,
Enter "1" for type of facility
Wet pond detention ............................................ ....... 1
Wet pond water surface area (acres) ................. ....... 0
Dry pond detention ............................................. ....... 0
Underground detention ....................................... ....... 0
Infiltration pond ................................................... ....... 0
Drywell infiltration ................................................ ....... 0
Coalescing plate separator ................................. ....... 0
Centrifuge separator (Vortechs 2000) ................ ....... 1
ther .................................................................. ....... 0
Outlet type (enter "1" for each type present):
Filter ......................................................................... .. 0
Oil/water separator .................................................. .. 0
Single orifice ............................................................ .. 0
Multiple orifices ........................................................ .. 0
Weir ......................................................................... .. 0
Spillway .................................................................... .. 0
Pump(s) ................................................................... .. 0
Other (Spreader Trench) ......................................... .. 1
Part 7 -Release to Groundwater
Design percolation rate to groundwater (if applicable) ..........................................NIA
Part 8 -Release to Surface Water (if applicable)
Prior to entering the storm pond, the flow will be routed through a Vortechs Model 2000 for stormwater
treatment. Once through the water quality device and attenuated by the 8,590 cubic foot storm pond, the
stormwater will be released to the Yelm Creek system through a spreader trench system located just
outside of the 100-year flood plain elevation.
SAS-'?.NTHA RI~vE Q4.10.^'c ?AGE 6
II. PROJECT ENGINEER'S CERTIFICATE
I hereby certify that this Drainage and Erosion/Sediment Control Report for the SAMANTHA RIDGE
project has been prepared by me or under my direct supervision and meets minimum standards of care
and expertise which is usual and customary in this community for professional engineers. I understand
that City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of
drainage facilities designed by me.
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III. DRAINAGE REPORT
Section 1 -Project Description
This report accompanies the civil plan submittal for the development of the 29 unit mulit-family project
named Samantha Ridge on Crystal Springs Road in Yelm, WA. The site is located east of Crystal
Springs Road in the northern extremity of the City of Yelm, directly across from the intersection between
Crystal Springs and Coates Street in Section 19 of Township 17N and Range 2E.
The project involves the creation of 29 residential units on 8 lots, approximately 14,500 Sq. Ft. of
associated private roads, and the associated recreation tracts and open space areas to satisfy the PRD
requirements of the City of Yelm.
Section 2 -Existing Conditions
Appendix Acontains apre-developed hydrology map showing the site as it exists today. As can be seen
from that map, the site remains mostly undeveloped and covered in grasses, a small number of trees,
and a small residence in the southwest corner of the subject property.
The overall site proposed for development is 179,583 Square Feet, or 4.12 Acres, after aright-of-way
dedication to the City of Yelm. Although the overall parcel is significantly larger than 4.12 acres, the
western portion of the site is being segregated through a Boundary Line Adjustment process and sold to a
third party; only 1.30 acres of the 4.12 acres will be developed.
The site is sloped to the east, fairly steeply at the western portion and fairly shallow farther to the east.
The site is entirely contributory to the small creek bed known as Yelm Creek. This creek bed has been
dry during the duration of this project, but historically has flowed through the rainy season. There is an
associated floodplain to approximately elevation 330 which is noted on the plans submitted with this
report.
Yelm Creek is considered a Critical Area. A Critical Areas Report has been compiled and submitted by
Talasaea Consultants under separate cover. This Critical Areas Report will address the reduction of the
CAO buffer to accommodate the proposed design.
Section 3 -Infiltration Rates/Soils Report
A geotechnical report was prepared by Gary A. Flowers, PLLC for this project and is included in Appendix
C. This report was prepared only for use by the design engineer in designing pavement and for
exploration of the feasibility of on-site infiltration.
Section 4 -Wells and Septic Systems
' Records at Thurston County Health Department and the Department of Ecology were searched in order
to locate wells and septic systems that may be located within the setback distances from the stormwater
pond. In addition, the Project Engineer, or someone under his direct supervision, has visited the site to
~ verify the presence or absence of wells and septic systems as best can be done visually without
trespassing onto other properties. All wells and septic systems found to be located within the setback
distances from the stormwater pond or ponds have been shown on the plans.
~ „4'UiANTNA ~Si~Gc G4.1~.v8 PRGE 8
Section 5 -Fuel Tanks
Records at Thurston County Health Department and the Department of Ecology were searched in order
to locate the presence of above and below ground fuel storage tanks that may be located within the
setback distances from the stormwater pond or ponds. In addition, the Project Engineer, or someone
under his direct supervision, has visited the site to verify the presence or absence of fuel tanks as best
~ can be done visually without trespassing onto other properties. All fuel tanks found to be located within
the setback distances from the stormwater pond or ponds have been shown on the plans.
~ Section 6 -Sub-basin Description
The site is made of three drainage basins (see Appendix A for Drainage Basin Exhibit), with a high
elevation of 345 feet along the southwest corner of the site and a low elevation of 330 feet along the north
and east sides of the project. For drainage basins #2 and #3 all impervious roads, sidewalks, and
driveways will be routed to the ponds for treatment and detention. All roofs will be provided with a storm
~ drainage stub connecting to the centralized storm drainage water quality and detention system, thus
eliminating the need for individual infiltration systems on each lot. Drainage basin #1 will convey a small
portion of the storm water for Crystal Springs Road to catch basin #12 then via a 12" diameter pipe to an
existing ditch along the west side of Crystal Springs Road. Drainage basin #1 discharges to the road side
ditch, instead of the project detention system due to elevation /grade issues.
Section 7-Analysis of 100-Year Flood
A Hydrogeologic Assessment was prepared by GeoEngineers addressing potential; high groundwater
flood hazard areas on or around the site. This report is was submitted under separate cover.
Section 8 -Aesthetic Considerations
The stormwater facility will be landscaped. Additional landscaping shall also be provided throughout the
' project in conformance with the approved landscaping and tree restoration plan, as applicable, and as
otherwise required by the approving authority.
Section 9 -Facility Sizing and Downstream Analysis
In the developed condition, we are proposing the installation of a 22' wide internal road system consisting
of approximately 14,500 Sq. Ft. of new impervious. In addition, the building pads will comprise
approximately 19,000 square feet of impervious area, with the driveways encompassing approximately
10,700 square feet of impervious area. When tallied, the impervious area created by the project will total
1.30 acres including both on-site and off-site areas.
The proposed storm drainage system, designed to comply with the 1992 DOE stormwater Management
Manual for the Puget Sound Basin, will include a detention pond at the eastern portion of the project site.
This storm pond has been sized to receive runoff from the site. The developed 2, 10, and 100-year
storms have been estimated using the SBUH methodology using the Stormshed® software. The pond
was then sized to reduce flows to the pre-developed flows of 50% of the 2-year, and the 10 and 100-year
flowrates for drainage basins #2 and #3. Prior to entering the storm pond, the flow will be routed through
a Vortechs Model 2000 for stormwater treatment. Once through the water quality device and attenuated
by the 8,590 cubic foot storm pond, the stormwater will be released to the Yelm Creek system through a
spreader trench system located just outside of the 100-year flood plain elevation. Drainage basin #1 will
discharge to an existing ditch on the west side of Crystal Springs Road.
A hydrologic analysis of the developed conditions has been completed using Stormshed software and the
SBUH methodology using a Type 1A hyetograph. On-site soil has been classified as Spanaway
Recessional Outwash Sand and Gravel as a result of the on-site soil exploration compelted by Gary
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Flowers, PLLC. Although the SCS mapping and the on-site work by Gary Flowers show the site as
containing both Spanaway and McKenna soils, infiltration on a large scale is not recommended due to the
presence of a high water table. Instead a detention system is proposed.
The results of the detention analysis, showing the expected runoff values from the impervious areas
contributing to the WQ and detention systems, are tabulated below:
Event Pre-Develop Flow (cfs) Developed Flow cfs) Attenuated Flow (cfs)
2- r/24-hr .1960 50% - .0980) .6074 .0990
10-yr/24-hr .4183 .9366 .4179
100-yr/24-hr .6667 1.2448 .6660 _ _ __
The detention pond sizing was performed utilizing the rates presented above and is presented in the
Appendix B. The appendix contains the hydrology calculations as well as pre and post-development
maps.
Section 10 -Covenants, Dedications, and Easements
1!~ All stormwater facilities located on private property shall be owned, operated, and maintained by the
property owners, their heirs, successors, and assigns. The property owners shall enter into an
agreement with the governing body, a copy of which is included in the Maintenance Plan. The agreement
requires maintenance of the stormwater facilities in accordance with the maintenance plan provided and
shall grant easement for access to the governing body to inspect the stormwater facilities. The
~ agreement also makes provisions for the governing body to make repairs, after due notice is given to the
owners, if repairs are necessary to ensure proper performance of the stormwater system and if the
owners fail to make the necessary repairs. The cost of said repairs shall be borne by the property
owners, their heirs, successors, and assigns.
~ Section 11 -Property Owners Association Articles of Incorporation
All residential subdivisions shall form a Homeowner's Association for the purpose of assigning
responsibility and liability for the operation and maintenance of stormwater facilities jointly serving lots
within the subdivision. The association is not required for facilities that serve a single property owner.
illy Articles of Incorporation shall be developed for the association and submitted to the governing body prior
to final project approval.
Section 12 -Other Permits or Conditions PI ed on h
ac t e Project
Building Permits will be obtained to construct the buildings.
Section 13 -Bond Quantities and Declaration of Covenant
These items will be supplied after the first review of this plan set.
SA':`AN?HA RIDvW 04.10.08 ?4Gc 10
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IV. EROSION CONTROL PLAN
Section 1 -Construction Se uence and Procedure
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1 Prior to commencing any grading or filling upon the site, all erosion control measures, including
installation of a stabilized construction entrance, shall be installed in accordance with this plan and the
details shown on the drawings. More specifically, the following construction sequence shall be observed:
1. Construction on this site shall be conducted substantially in accordance with the construction
sequence described on the plans and in this erosion control plan. Deviations from this sequence
shall be submitted to the project engineer and permitting jurisdiction. Deviations must be
approved prior to any site disturbing activity not contained within these plans.
2. For each phase of the development of this site, the following general sequence shall be
observed:
a. Flag clearing limits.
b. Install construction entrance.
c. Install inlet protection for existing inlets in the vicinity of areas to be disturbed.
d. Call for inspection by the project engineer.
e. Clear and grub site per plans and specifications.
f. Install erosion control measures as required.
g. Rough Grade site and install utilities and storm drainage improvements.
h. Fine grade and pave site.
i. Stabilize site with landscaping and required seeding.
j. Remove erosion control measures after site is stabilized and after approval of Pierce County
inspector.
3.Once the site is disturbed, continue operations diligently toward completion.
4. Monitor all erosion control facilities, and repair, modify, or enhance as directed or as required.
Section 2 -Soil Stabilization and Sediment Trapping
Sediment ponds shall be constructed at the beginning of each phase of construction to perform as
temporary sediment traps. Protection of offsite properties against sedimentation is an absolute necessity.
Additional measures may be required to provide full protection of downstream areas. Additional
~ measures may include, but are not limited to, use of sediment bags in existing catch basins, increased
filters within sediment ponds such as hay bales, introduction of coagulants to the sediment ponds, and
other such measures. Continuous monitoring of the erosion control systems, depending upon site and
weather conditions, shall be ongoing throughout project development.
Vehicle tracking of mud off-site shall be avoided. Installation of a stabilized construction entrance shall be
installed at the start of construction at the exit point to be used by equipment. This entrance is a
minimum requirement and may be supplemented if tracking of mud onto public rights-of-way becomes
excessive. If the entrance mat becomes filled with dirt, it will be refurbished by dislodging the riprap and
reconstructing the pad. Alternatively, new material will be added to the pad to provide storage for
additional sediment. Should sediment be tracked on to the street, operations will cease until the tracked
material has been removed by street sweeping and the pads have been refurbished.
~ Catch basin inserts placed throughout the site will trap sediment and prevent silt laden runoff from leaving
the site. The insert will be examined regularly for rips or tears in the material and will be replaced if
defects are identified.
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Section 3 -Permanent Erosion Control and Site Restoration
There are no permanent retaining walls, energy dissipaters, geotextiles, or bank reinforcements
associated with this project. This project shall utilize landscaping and paving as permanent erosion and
sediment control features.
Disturbed areas on and off-site shall be hydroseeded or otherwise landscaped or stabilized upon project
completion to provide permanent erosion control where required. Erosion control measures shall remain
in place until final site stabilization is imminent (e.g., paving scheduled with a favorable weather forecast).
Section 4 - Geotechnical Analysis and Report
Existing slopes in the area of the stormwater ponds are at a maximum of 2%. No embankment is
required. A geotechnical report has been prepared by Gary Flowers and was submitted under separate
cover.
Section 5 -Inspection Sequence
The Project Engineer, or someone under his direct supervision, and the permit authority shall inspect the
temporary erosion control facilities (construction entrance, sediment traps, and erosion control barriers)
prior to commencement of construction. During and following construction, the Engineer shall inspect the
construction of the permanent stormwater facilities and report to the permit authority his findings as to
performance and operability of the completed system.
The plans for this project specify the use of various erosion/sediment control measures: construction
entrance and catch basin inlet protection. These sediment control facilities will be inspected weekly at the
end of the work week and subsequent to each storm event.
Section 6 -Control of Pollutants other than Sediments
Control of pollutants other than sediments is the responsibility of the Contractor. As a minimum, a
centralized equipment marshalling area and containment area is to be provided on-site for equipment
maintenance and storage of any equipment service materials. An area on-site will be selected as a
temporary debris and stockpile area for materials that will be removed from the site. Erosion control
containment and berming of this area will be provided for pollutant containment and sheeting provided for
coverage or lining if applicable. The superintendent will be expected to use his best judgment in
addressing any and all conditions that are potentially damaging to the environment.
Section 7 -Utilities
Trenches will be opened only immediately prior to installation of the sewer and water utilities. Trenches
will be backfilled immediately after any required testing or inspections of the installed utility lines. In
locations where the utility trenching may interfere with stormwater quantity and quality control measures,
the construction superintendent will coordinate the activity to ensure that no erosion or sediment transport
occurs. Trenching spoils will be treated as other disturbed earthwork and measures will be taken to cover
or otherwise stabilize the material, as required.
~' SA`:iANTHA :s1~GE a4.10.G8 PRGE 12
1 APPENDIX A -Vicinity Map & Drainage Exhibits
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September ll, :007
~1R. DF.N'~IS RAT:FR CASE \U.: 0.-t0-0640:1
GEOMATICS LAID SURVEI'ING COhtA1L'\IT"Y: C'1"i'l' OF YEL41_ THL:RSTON COUNTY
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N.O. E30X 2550 N`ASHING l-OK
YELM, WA 98597-2SS0 COMMUNITY NO.: 530310
DEAR MR. IiAI;ER:
This is in reference to a request that `the Federal Emergency Management Agency (FEV1A) determine
if the property described in the enclosed document is located within an identified Special Flood
Harard Area, the area that would be inundated by the flood having a 1-percent chancy of being equaled
or exceeded in an}• given year (base flood), on the effective National Flood Insurance Program (NF1P1
~ map. Using the information submitted and the effective NFIP map, our dctenninatiun is shown on the
attached Letrer of Map Amendment (LnMA) Determination Document. This determination document
provides additional information retarding the effective 'v'F1P map, the legal description of the
property and our determination.
~ Additional documents are enclosed which proeide information regarding the subject pruperty and
LUMA
l
s. P
ease see the List of Enclosures below to determine which documents are enclosed. ether
attachments specific to this request may be included as referenced in the Dclermination,'Comment
document If you have any questions about this letter or any of the enclosures, please contact the
FEMA Map Assistance Ctntcr toll free at {877) 336-2627 (877-FEM.A MAP) or by letter addressed
~ to the Federal Emergency ;tanagement Agency, 3601 Eisenhower Avenue, Suite 130, Alexnndria, ~'A
2230-6.139.
5inccrely
William R. [3lantrnt Jr., CFM, Chief
Engineering Management Section
\•titisation Directorate
' LIST pF ENCLOSURES:
LOMA DETERMINATION DOCUMENT (RE:~tOVAL)
cc: Smu;Commonwealth'~F1P Coordinator
Community ~1ap Repository
Region
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Page 1 of 2 Date: September 11, 2007 Case No.: 07-10-0690A LOM1IA
,t'
=~~1~- Federal Emergency Mana
erl~tnt /~
encv
g
~
r
`i.~ 1Gashm~ton. l~.C. 30.1?_'
~
•
'rs t, a c
LETTER OF MAP AMENDMENT
DETERMINATION DOCUMENT REMOVAL
COMMU NITY AND MAP PANEL INFORMATION LEGAL PROPERTY DESCRIPTION
CITY OF YELIN, THURSTON A poAion of St_ction 19, Township 17 North. Range 2 East.
COUNTY, WASHINGTON Willamette Mendtan as shown on the Boundary line Adjustment Map
recorded as Document No 3935810, in the Office of the Recorder
COMIUNITY ,
Thurston County, Washington
COMMUNITY NO.: 630310 The portion of property Is more partitxltarty described by the following
metes and bounds:
AFFECTED NUMBER; 5303100001A
MAP PANEL
GATE: 1i1t6/1999
FLOODING SOURCE: YELM CREEK APPRO%IMATE LATITUDE 3 LONOITUOE OF PROPI?KTY: {6.9{5, •122805
SOURCE OF LAT 8 LONG: PRECISION MAPPING STREETS 7-0 DATUM: NAO O3
DETERMINATION
OUTCOME 1°`„ AfiNUAL LOWEST LOWEST
LOT t3LOC1C/
SUBDIVISION
STREET KMAT tS
REMOVED FROlA
FLOOD CHANCE
FLOOD ADJACENT
GRADE LOT
ELEVATION
SECTION THE SFHA ZONE
ELEVATION
ELEVA710N
(NGVD29)
NGVD 291 NGVD 29
502 Crystal Springs Portion of X 330.2 to 329.4 - 330.2 to 329 4
Road NW Property (srwde•d) feet ~
Speelal Florxf Hazard Area (SFHA) -The SFHA is an area that would be inundated by the flood having a 1-percent chance of being
e ualed or exceeded in an ivten ear base flood
ADDITIONAL CONSIDERATIONS Please refer to the to sedan a+ Ansi3aneM t la the additbnal considerations fisted bebw.
LEGAL PROPERTY DESCR1PTtON
PORTIONS REMAIN UV THE SFHA
TMs dowrnsm provaes the Federal Emergency Management Agenlys determinaaon regardug a request ror a letter of Map Amendment for
the property described above. Using the inlormatlon submitted and the eftecDve National Flood Insurance Program (NFIP) map, ws havc
determined that the deswiDed portion(s) of Ifte propeny(ies) is~are not located in the SFHA, an area Inundated by ttte flood havng a i-percent
chance of being equabd or exceeded in any given year (base floodl~ This dowment amends the eflearve NFIP map to remove the suD)ed
property from me SFHA lopted on ttte af}edivo NFIP map, therefore. the Federal mandatory food insurance requirement does not apply
However, the lender has the option to continue the flood insurance requirement to prated ds 6nanaal risk on the loan. A Preferred Rrsk Pokcy
'
(PRP) is svar7sbte for bu
Wngs boated oulsi0e the SFHA_ IMormabon about the PRP and how one can appy a endosed.
This dNerminalion M based on the Oood data presently avalUbM. Tno endosed docwnents provide additional miormauon regarding Inis
determinalan. U you havc eny quesbona ^bout this dowment, please contact the FEMA Map Assistance Center toU free et (877) 336-2627
(877-FEMA MAP) or Dy lector addressed to the Federal Emergency Management Agoncy. 3601 Eisenhower Avenue. Sulfa 130. Alexandria. VA
21301-6439.
~Ydkam P,. Blanton Jr.. CFM, Chief
Lngureenng Management Section
Mitigation bireCOraM
SA~•"„-~NTHA RIDG= ~G.10 ~,r; PAGc 20
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Pagtt 2 of 2 Date: September 11, 2007 Case No.: 07-10-0690A LOh1A
of}4i1e
~~ ~ Federal Emergency Management Agency
%~~f ~1'ashint!tcm. ll i'. ~0~-,
i~t, 1+~
LETTER OF MAP AMENDMENT
DETERMINATION DOCUMENT (REMOVAL)
ATTACHMENT 1 (ADDITIONAL CONSIDERATIONS)
LEGAL PROPERTY DESCRIPTION (CONTINUED)
COMMENCING at the Northwest Comer of the Northeast Quarter of the Northwest Quarter; thence SO1 `02'02"E,
1322.01 feet; Thence S01°01'58"E, 1095.58 feet; thence S01 °02'00"E, 192.08 feet to the POINT OF
BEGINNING; thence N37°57'43"E, 47.68 feet; thence N01°02'00"W, 531.32 feet; thence S56°1T48'E, 3.07 feet;
thence S28°OT43"E, 47.77 feet; thence S83°25'52"E, 14.16 feet; thence N53°54'13"E. 14.48 feet; thence
N30°49'37"E. 23.92 feet; thence S83°48'10"E, 21.70 feet; thence S31"14'32"E. 56.02 feet; thence S36°14'02"E,
31.55 feet; thence 534°10'24"E, 41.18 feet; thence S34°05'02"E, 46.72 feet; thence S36°22'25'E, 46.57 feet;
thence S51°31'28"E, 47.44 feet; thence S49`13'15"E, 23.55 feet; thence S07°52'26"W, 34.62 feet; thence
S40°45'47"E, 16.68 feet; thence S18°38'14"E, 32.01 feet; thence S40°37'04"E, 46.48 feet: thence S35°16'44"E.
27.28 feet; thence N81°11'28"E, 37.25 feet; thence S50°54'00"W, 236 76 feet; thence N01`02'00"W, 10.00 feet;
thence S79°40'S4'W, 100.63 feet; thence S01 °02'00"E, 10.00 feet; thence S79°40'S4'W, 100.00 feet to the
POINT OF BEGINNING
PDRTIONS OF THE PROPERTY REMAIN IN THE SFHA (This Additional Consideration applies to the
preceding 1 Property.)
Portions of this property, but not the subject of the Determination/Commeni document, may remain in the Special
Flood Hazard Area Therefore, any future construction or substantial improvement on the property remains
subject to Federal, State/Commonwealth, and local regulations for floodplain management.
This attachment provides additional information regarding this request. If you have any quechons aooul INS attachment please contact the
FEr.+A Map Asalstance Center toll Tree at (977) 336Q627 (971•FEMA MAP) or by letter addrossdd to the Federal Emergency Management
Aper><y, 36D1 Eisenhower Avenue, SuAe 130. AW_xandria, VA 223-6439.
William R Blanton ,Ir., CFM. Ct>ief
Engineering Management Section
Mitigation O+redorate
.~4.10.Cts _ .......___....._ AGE 21
SAMANTHA Rf~GE ~
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Ee.e u r,+,F
V~~ i
~ Federal Emergency l~lanagement Agency
°s ~` Washington, D.C. 20d?2
ADDITIONAL INFOR~~IATION REGARDING
LETTERS OF MAP A,`•iENU'~1ENT
When making determinations on requGCts for Letters of Map Amcndmrnt (LOfiAs), the Department of
Homeland Sccwity's Federal Emergency A•lanagcmtnt Agency (FE.+~t.A) hasr_ti its determination on the flood
hazard information available at the time of the dctertnination. Requesters should be aw•arc that flood
conditions may change or ncu• infonnation may be generated that would suptrscdc FG'~tA's dctrrmination. In
such cases, the conununity will be informrd by letter.
Requesters also should be aware that removal of a property (parcel of land or stnrcturc) from the Special
Flood Hazard Area (SERA) means FEh4A has determined the pmpem~ is not subject to inundation by the
flood having a I-percent chance of being equaled or exceeded in any given year (base flvod). This doer not
mean thr properly is not subject to other flood hazards. The property could be inundated by a Hood with a
magnitude _rreatcr than the base flood or by localized (boding not shown on the effective National Flood
Insurance Program (NFIP) map.
The cffxt of a LOMA is it removes the Federal requirement for the lender to require flood insurance
coverage for the property described. The LOMA is not a u-aiver of the condition that the property owner
maintain flood insttranee coverage for the property. Only the )ender can waive the flood insurance purchase
requirement because the lendef imposed the requirement. The property m+~tcr must rcrquest and receive a
+rritten waiirr front the lender before canceling the policv. The lender may determine, on its on•n as a
business decision, that it wishes to continue the flood incttrance requirement to protect its financial risk on the
loan.
The LOMA provides FEIv1A's comment on the mandatory flood insurance requirements of the NFIP as they
apply to a particular property. A LOh4A is not a building permit, nor should ii be construed ac such. Any
development, new construction, or substantial improvement of a property impacted by a LOMA must comply
with all applicable State and local criteria and other Federal criteria.
If a lender releases a property owner from the flood insurance requirement, and the property ownter decades to
cancel the policy and setk a refund, the NFIP will refund the premium paid for the current policy year,
provided that nv claim is pending or has bren paid on the policy during the content policy year. The property
owner must provide a written waiver of the insurance requirement from the lender to the property uuurartce
agent or company srn•icing his or her policy. The agent or company will then process the refund request.
Even though stnuctwes arc not located in an SFl-IA, as mentioned above, they could be flooded by a flooding
event with a greater magnitude than the base flood. In fact, more thazr 25 percent of all claims paid by the
NFIP are for policies for structures located outside the SFNA in Zones B, C, X (shaded), or X (unshaded).
More than one-fourth of aU policies purchased under the'`+FIP pmtcct structures located in these zones. T~lre
risk to structwes located outride SFHAs is just not as great as [hc risk to swctures located in SFHAs. Finally,
approximately 90 percent of all federlly declared disasters are caused by flooding, and homeowners
insurance does not pro~~ide financial protection from this flooding. Therefore, FEMA cncaurages ttte widest
possible coverage under the NFIP.
LOh'IAEI~C-1
°.tDG~ ti4,10.G8
APPENDIX B -Hydraulic Analysis
1
SA:`•:~ANTNn nIDGE 04.1;;.8 ...PAGE 23
PROPOSED DETENTION POND SUMMARY:
PROPOSED DETENTION POND SUNh1AFtY:
-0~IENSIONS: 53.00`~6.5D'
-0EPTH: 5 (C DEEP POND! 1' FREE BDVIRD)
BOTTOM OF POND ELEVATION. SJ0.00
-TOP OF POND ELEVATION: 335,00
BOND VOLULE (REOUIREDk B,8T2~2 CU. FT.
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SAI.~ANTHA RIDGE 04.10.08 PAGE 25
noTS:
VORlEC11S SY8761S INSTALLED IN
A 9YPA65 CONFlGURATION
REOLRRE AN UPSTRFAIM DIV94410N
6TRUCTURE THAT SHALL BE
DETAILED aY THE COHSULT1Hi 100
ENGINEER WITH EIEYATN]fIAND
WER WIDTH DATA PROVOED HY
CONTECH $TORaAWATER
aauTlona ~ sExANr
ALIaYIIAIN SWIRL
CHAMBER ~~ / /~ EXTRUDED aUnA N SEAL ~- ~~R1h
/ ~
~-
OUTLET VARIES,
A ,~ + SEE noTE o A
~ WEB a *~
}._._
INLET VARIES, SE6 NOTE5869. ~-J aAFRE WALL-~ ~ROw~f11~~L
RYLET PIPE NA13T BE A CORNER INLET
TO INTRODUCE FLOW 7ANGEMVILLY
T9 THE SWIRL CNANSER
PLAN VIEW B - B
RIM ELEVATIONS TO
OONCRETE RErFORCFD MATCH FaV19Fm GRADE
FDR F1920 LDAONG
• ~ R1SERa BY GTHETi3
TOP AND SIDES
SEALED 7'O-
VN1LT ~ B
WEIR
WEIR /
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OPoFICE
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TO PUT6B
MLET DER OUfLET INVERT
l{ .__ ~ ~ __
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TYP
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TYP TYP
~
.d' e~r `~ _ oo;o 0 on?
^~> ° ~ f" <crd+ ~_ u~ _ ocr,~ -.va - NR11Na/N S•COMPACIID GMV[L
SECTION A - A
NOTES
1. STORLAYATFA TREATNENT BTSiD1 (SWIS) bNKL lNVE 1. SWf9 SHALL HAVE NO MFRNAI G17MONFNT9 TW1708STRUCTAWNIEnAMFACCE39
/iAK lAEA7NEM CAPAClTI".2btFb b NIET PPE MUST bE PfAPFfYNGIAM TO THE STRUCTURE
e~/~ORSTORAGE'12 CUYD A Pa+E QgtENTATY7NWYVARY; SEE SITE PLAN FOR S/&AND LOCA1pN
~7 G11a1aER DY\ f MN 1R PUiCWLSER 9Ii41 NOTSE RESfC71i91BIE i70R ASSFJIaLYOF IRIT
2 bSVTa SHALL EE CONUWm NOME RECIANGUAR SiRUCRgE S1.MMf10LE FRAMES AND PERFORATED COVERS IUPPIED WRH SYSTFAL NOTNSfi1LLED
1 SW13 REMWAI EFF1CffllCT' SWILL BE DOCUAEMFD EASED ON PARTIO.E S~ 12 PURCfKSFR ro PREPARE ETLGIYATATNANO PRONL¢ CAANEFOR CFT LpADN6AND 9ETfMq
1. SYB 9N[L RETAN FLOM7ASL.E.S AND TRAPPED IED~ETTT UP TO ANO AT TYLE OF DELIVERI'
NCLLO1NC PEN(7REATaEM CAPACJTT 1A YortrtT.leS sYSTEPa er COHfECN810RMKYITER EaVDOl1s; PORIINQ CR lew) alblerr
A awls rroERrs HAND ouTARE TYPIG1lLYATTHE sALE FL2VATICN SCMBWIOUGH Lff ronl ao13e7A 11FII1ICULl Mo roBe1710311/.
l SWIS SHALL NOISE COMPROYI9ED bYfFFCf:13 OF DOWNSTREAM TAlWA7E11
PROPRIETARY INFORMATION - NOT TO BE USED FOR CONSTRUCTION PURPOSES
7NP CAOO fr Y brlr PPPPr• d pdy~y ~mwwl rVPiIYA P WlpnfPM b CP AmNIwO M LONRrAI bbnww SbP11mP Pb mq PPIL' d bnPYnP1 b PSwr OPPIPRIb aAy a pgMOPO
q COIfTECH SbmuPY 8o~ewa TIIY Motli bbin~IbL ~abS Sw CONTECN 9bmrwlr SWlur bbonq CIP WNds Sbnmldr TtW1r119yPMn Orbf9m btl pPMR 11YIIbf, Rro
Ee AHa1e1 P iMO~Prry. RPtimP b P11T PPA d tl1r1 CADD M ~tl1Wl P' ooaNYrlen all CONTECH 8bm~~Or 90Y~1011/ ~11Y EP mre~PC unuMpholE uY d
prepnrPry :rP^^PS;or.
w~~nzwu•
~~~~~' ~ `` ~
STANDARD DETAIL
STORMWATER TREATMENT SYSTEM
SiOwVIWATER
VORTECHS® MODEL 2000
SOLUTIONS
_ U.S. PATEM Nn A7W.11a
OOIIad11LOfILAPBMI.COf11 DAZE 10RA6 SCALE NONE FIE NAME STOQK DRAWN:Ja4 CHECJ(ED: NDG
i~
~ l
KL~.
Si;'v'.ANTHk ~I~vE ±/4.10.~8
~.AG~ 26
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PRE-DEVELOPMENT STORM EVENT SUMMARY:
__
Event Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method
6-month 0.0526 8.17 0.0374 1.3000 SBUH
2 year 0.1960 8.17 0.0981 1.3000 SBUH
10 year 0.4183 8.00 0.1884 1.3000 SBUH
-- -
25 year _
0.5409
8.00
0.2364
1.3000 __
SBUH
100 year 0.6667 8.00 0.2856 1.3000 SBUH
PRE-DEVELOPMENT AREA SUMMARY:
Design Method SBUH Rainfall type TYPE1A i
Hyd Inty 10.00 min Peaking Factor 484.00
Abstraction Coeff ~ 0.20
__ .. __._
Pervious Area (AMC 2) ..
1.30 ac _. _..
DCIA --- ~---- _. __t
j 0.00 ac
Pervious CN 87.00 DC CN 0.00
.Pervious TC 19.32 min DC TC 0 00 min
Pervious CN Calc It
E
.....,.,.. ._ .,..,....._ ....___ _... ._.._._
j Description __ ..... SubArea Sub cn
`j Herbaceous
j
- 1.30 ac ; 87.00 ;'
r
___. __ _ ..._--- __ _ _.
-_ ---- _
Pervious Composited CN (AMC 2)
...~ I '
! 87.00
Type Description Length Slope Coeff Misc TT
Sheet Dense grasses :0.24 50.00 ft 22 00% 0.2400 .0.00 in 0.00 min
Sheet Dense grasses :0.24 100.00 ft 3.00% 0.2400 0.00 in 0.00 min
Pervious TC 19.32 i
1
SAh.IAILTFir"H Rf~v^~ 04.10,0& PAGE 27
POST DEVELOPMENT STORM EVENT SUMMARY:
Event Peak Q (cfs) Peak T (hrs) Hyd Vol (acft) Area (ac) Method Raintype
6-month 0.3386 7.83 0.1078 1.3000 SBUH TYPE1A
2 year 0.5991 7.83 0.1922 1.3000 SBUH TYPE1A
10 year 0.9235 7.83 0.2999 1.3000 SBUH TYPE1A
-_ - __
5 year 1.0844
__ _ __
7.83
_-
0.3539
_
1.3000 SBUH
YPE1A
100 year 1.2448 7.83 0.4079 1.3000 SBUH TYPE1A
POST DEVELOPMENT AREA SUMMARY:
- _ __
Design Method
SBUH
Rainfall type
TYPE1A
Hyd Intv 10.00 min Peaking Factor 484.00
Area (AMC 2) 0.00 ac DCIA
CN 0.00 DC CN
TC 0.00 min DC TC
Directly Connected CN
Description
'~ DC Composited CN
Directly Con
Type Description
Smooth Surfaces.: 0.011
(interm) ~ Concrete pipe (n=0.012)
Coeff ~ 0.20
1.30 ac
98.00
0.56 min
1.30 ac
Sub cn
98.00
Length Slope Coeff Misc TT
30.00 ft 10.00% -0.0110 0.00 in 0.00 min
200.00 ft 2.00% 0.0120 0.56 min
'd TC 0.8Bmm ? v
?AGE 28
HYDROGRAPH PLOTS:
PRE 8~ POST DEVELOPMENT - 2 YEAR HYDROGRAPH
Start of live storage: 330.0000 ft
Event Match Q (cfs) Peak Q (cfs) Peak Stg (ft) Vol (cf) Vol (acft) Time to Empty
- __ __
2 year 0.0980 0.0990 332.1232 2865.71 0.0658 39.33
__. __
_-
0.5 _
~ ; ,
~ 0.4 - - - - - -.- - -
s
,° 0.2 -.-----~---
0.1 -
0 -,
r~ o M
O 00
N N
.~- O M
O OD
!D f~ ti
2 yeas Hytlio~raph Plot
-----~------ -- -~--'--',--',--',--1-' -',-~~~-gPOS;2-~y'~:arl
, ~ ~ ~ ~ ~ ,
-,----- - -----;--~- - - - ------ -a~ ~2y~eerout
1~ O f'7 r~ O M n O M I~ O M f~ O M f~ O M h~ r
(D 47 M ~-- O 00 ID U1 M ~ O OD (D ~fJ M r O OD fD ~f
00 Of O ~ N N M V ~fi (D f` ti O O O ~ N N M d
r r r r r r r r N N N N N ['~
Time in Hours
PRE 8~ POST DEVELOPMENT - 10 YEAR HYDROGRAPH
Start of live storage: 330.0000 ft
Event Match Q (cfs) Peak Q (cfs) Peak Stg (ft) Vol (cf) Vol (acft) Time to Empty
10 year 0.4183 0.4179 332.4328 3476.86 0.0798 42.17
10 yeas Hyiliogiaph Plot
. _
~~ ~ N`ost `10 year
0.8
~'
c, 0.6 ~ ; ,
,
0 0.4 '
0.2 -
t 0
•
M r
o ~•;
m u? ~~ c-, r~ o M r~ o c~ n o M r` o
~ o ao cD u~ M
o ao cn M r+
o- o M r` o M
a
- f~ o M rti o M r`
~ ~
~ , ~ o
o cn ~ o
~ r- o ao cn u~ M r-
O N M ~ V1 Vi f0 1~ OD O O O ~ N M V 4n ~!i (D r< O O O O N M tF
~ ~ ~ ~-' ~ ~ ~ ~"' r e- ~ N N N N N N
Time in H ours
=,-n~TH.A RI~G~
04.1
0.08 ___
?AC_ Z9
PRE 8 POST DEVELOPMENT -100 YEAR HYDROGRAPH
Start of live storage: 330.0000 ft
__ __ _
Event Match Q (cfs) Peak Q (cfs) Peak Stg (ft) Vol (cf) Vol (acft) Time to Empty
__
100 year 0.6667 0.6660 332.8451 4377.40 0.1005 42.67
100 year Hydrograph Plot
--~--~-----~--,------,- - --,--;--;-- --- --~--~-- ---~-®-Pest;t0o-y?fir.
~ ~ ~ v ®100 year ouC
v ;
~ ,
.~ ~ ~ ~ ~ ,
0
t~ O ('') Iti O C` i ti O M Iti O M 1~ O M ti O f7 1~ O ('7 t~ O M 1~ O M 1~ O
fD U7 Mi ~ O O [D U7 (~"1 O OD (D tfi f+'i O 00 fD U7 M O OD (D V7 fh O
O r N C'7 V V Ul (il 1~ 00 ~ m O N M V ~ V7 (D rti 00 O Q) O N ('7 ~
~ r ~--~ r r ~- r r N N N N N
Time in Hours
DETENTION POND SUMMARY:
Record Id: MH Release
Descrip: .Prototype Structure Increment 0.10 ft
Start EI. 330.0000 ft Max EI. 335.0000 ft
Orif Coeff 0.62
Lowest Orif EI. _,
98.00
Lowest Diam 1.5820 in Dist to next 2.2300 ft
_-.
D2 5.0684 in
Dist to next
0.3100 ft
D3 0.5859 in Dist to next 0.0000 ft
Stage Discharge Rating Curve
330.1000 ft 0.0215 cfs 332.7000 ft 0.5932 cfs
330.2000 ft 0.0304 cfs 332.8000 ft 0.6447 cfs
330.3000 ft 0.0372 cfs 332.9000 ft 0.6919 cfs
__ ._
330.4000 ft 0.0430 cfs 333.0000 ft 0.7357 cfs
330.5000 ft 0.0480 cfs 333.1000 ft 0.7768 cfs
___ _ _
330.6000 ft 0.0526 cfs 333.2000 ft 0.8156 cfs
_._.
330.7000 ft 0.0568 cfs 333.3000 ft .0.8526 cfs'.
__
330.8000 ft 0.0607 cfs 333.4000 ft 0.8879 cfs
330.9000 ft 0.0644 cfs 333.5000 ft 0.9218 cfs
SA`:'.ANTHk RIDGE ;;4.10.03 _ 'AGE ;i0
1000 ft
0.9544 cfs
1.0163 cfs
1.0458 cfs
i~
331.4000 ft 0.0804 cfs 334.0000 ft 1.0745 cfs
331.5000 ft 0.0832 cfs 334.1000 ft 1.1024 cfs
__- _ _ _--
331.6000 ft 0.0859 cfs 334.2000 ft 1.1296 cfs
331.7000 ft 0.0886 cfs 334.3000 ft 1.1562 cfs
331.8000 ft 0.0911 cfs 334.4000 ft 1.1821 cfs
_ ---
331.9000 ft 0.0936 cfs 334.5000 ft 1.2074 cfs
332.0000 ft 0.0961 cfs 334.6000 ft 1.2322 cfs
-----___
332.1000 ft 0.0984 cfs 334.7000 ft 1.2565 cfs
__._
332.2000 ft 0.1007 cfs 334.8000 ft 1.2804 cfs
332.3000 ft 0.2874 cfs 334.9000 ft 1.3037 cfs
332.4000 ft 0.3926 cfs 335.0000 ft 1.3267 cfs
__ _._ -_
332.5000 ft 0.4696 cfs 335.0000 ft 1.3267 cfs
2 YEAR OUT - HYDROGRAPH SUMMARY:
Area 1.3000 ac Hyd Int 10.00 min Base Flow
__ _-
Peak flow 0.0990 cfs _
Peak Time ,
12.17 hrs
Hyd Vol
_-
0.1922 acft'
___ __ _
.Time (hr) Flow (cfs)
Time (hr)
Flow (cfs)
__
- -
Time (hr)
_.
Flow (cfs)
__ _.
1.17 0.0000 14.00 0.0985 26.67 0.0711
1.33 0.0010 14.17 0.0984 26.83 0.0701
1.50 0.0027 14.33 0.0983 27.00 0.0690
1.67 0.0048 14.50 0.0982 27.17 0.0680 ~'
1.83 - - - -- - _ _
0.0073 _
14.67 __
0.0981 _
27.33 ____ _ __ i
0.0669 '~
2.00
._
.
. 0.0101
- 14.83 0.0980 27.50 0.0658 i
.
_
_
2.17 --._
_ _ - -
0.0132
15.00
0.0979
27.67 _---i
0.0648
2.33 0.0165 15.17 0.0978 27.83 0.0636
2.50 0.0198 15.33 0.0977 28.00 0.0625
2.67 0.0221 15.50 0.0976 28.17 0.0614
2.83 0.0235 15.67 0.0974 28.33 0.0603
--____ _
3.00 _- ------------ .
0.0250 ~.._ _ _
15.83 _.._... _ _
0.0973 _
28.50 _-----_.i
0.0591
3.17
-_ 0.0264 16.00 0.0971 28.67 0.0579 '.
j 3.33 0.0280 16.17 0.0970 28.83 0.0568
Si;~ANTHA RI~Gc ,~~.~;,
3.50 0.0295 16.33 0.0968 29.00 0.0556
3.67 0.0309 16.50 0.0967 29.17 0.0543
3.83 0.0322 16.67 0.0965 29.33 0.0532
4.00 0.0335 16.83 0.0964 29.50 0.0519
4.17
0.0350
17.00
0.0962
29.67 ...................
0.0506
4.33 0.0366 17.17 0.0961 29.83 0.0494
4.50 0.0380 17.33 0.0959 30.00 0.0482
4.67 0.0395 17.50 0.0957 30.17 0.0468
4.83 0.0411 17.67 0.0955 30.33 0.0455
~
5.00 --
0.0427
17.83 _ .
0.0953
30.50 _ _
0.0442
5.17 0.0441 18.00 0.0951 30.67 0.0429
;
-
5.33 _
0.0457 18.17 0.0949 30.83 _
0.0415
.~_
5.50
0.0473
18.33
0.0947
31.00 -
0.0401
5.67
0.0488
18.50
~ 0.0945
31.17 _ --- ---,
0.0388 f
5.83 0.0504 18.67 0.0943 3 ] .33 0.0375
6.00 0.0519 18.83 0.0941 31.50 0.0360
6.17 0.0535 19.00 0.0938 31.67 0.0345
6.33
0.0553
19.17
0.0936
31.83 _.....,
0.0331
6.50 0.0570 19.33 0.0933 32.00 0.0317
j 6.67 0.0588 19.50 0.0931 32.17 0.0304
j 6.83 0.0609 19.67 0.0928 32.33 0.0287 i
7.00 0.0627 19.83 0.0925 32.50 0.0271
7.17 0.0648 20.00 0.0923 32.67 0.0256
'7.33
___ . _ 0.0670
---- 20.17 0.0920 32.83 0.0241
I
_
7.50 _
___-__
0.0692 20.33 _____.. _. ____
0.0918 _
33.00 _ ___--_____
0.0228
7.67 __
0.0733 '
20.50
0.0915
33.17
0.0215
7.83 0.0794 20.67 0.0913 33.33 0.0186
8.00 0.0848 20.83 0.0910 33.50 0.0161 j
8.17
-- 0.0884 21.00 0.0908 33.67 0.0139
_ _
8.33
0.0902
21.17
0.0905
33.83 _.
0.0120
8.50 0.0918 21.33 0.0902 34.00 0.0104
.. __ -: - __ - _ _-- _ _ ..__.~i
8.67 0.0932 21.50 0.0900 34.17 0.
0090
8.83 0.0941 21.67 0.0897 34.33 _
0.0078
9.00 0.0950 21.83 0.0895 34.50 0.0067 ~
9.17
0.0957
22.00
0.0892
34.67 __ _
0.0058
v F.~
?AGE ~2
I~
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
9.33 0.0962 22.17 0.0890 34.83 0.0050
9.50 0.0966 22.33 0.0887 35.00 0.0043
9.67 ___
0.0970 _
22.50
0.0884
35.17
0.0037
9.83
0.0973 __ _
22.67 _
0.0881
35.33 ___ _
0.0032
_
10.00 _._
0.0976
22.83
0.0878
35.50
0.0028
10.17 0.0979 23.00 0.0875 35.67 0.0024
10.33 0.0981 23.17 0.0872 35.83 0.0021
10.50 0.0983 23.33 0.0869 36.00 0.0018
10.67 0.0984 23.50 0.0866 36.17 0.0016
~_~. _
10.83 ___
0.0985
23.67
0.0863
36.33
0.0014
-- -
11.00
0.0986
23.83
0.0860
36.50
0.0012
r~-- 11.17 0.0987 24.00 0.0858 36.67 0.0010
_..
11.33
0.0988
24.17
0.0852
36.83 _ _ _;
0.0009
11.50 0.0988 24.33 0.0844 37.00 0.0008
11.67 0.0989 24.50 0.0835 37.17 0.0007
11.83 0.0989 24.67 0.0826 37.33 0.0006
12.00 0.0989 24.83 0.0817 37.50 0.0005
12.17
. 0.0990 25.00 0.0808 37.67 0.0004
_.
..
12.33 _ _
0.0990
25.17
0.0799
37.83 ,
0.0004
12.50 0.0989 25.33 0.0789 38.00 0.0003
_.
12.67 _ _
0.0989
.
25.50
0.0780
38.17
0.0003
4
12.83 . _.
.. _.. _... ..._.
0.0989 _
25.67 __ ..__.___
0.0771
38.33 _ .___i
0.0002
13.00 0.0988 25.83 0.0761 38.50 0.0002
13.17 0.0988 26.00 0.0751 38.67 0.0002
13.33 0.0987 26.17 0.0741 38.83 0.0002
13.50 0.0987 26.33 0.0731 39.00 0.0001
13.67 0.0986 26.50 0.0721 39.17 0.0001
13.83 0.0986 26.67 0.0711 39.33 0.0001 :'
u.
r
e
i
i
r
w
10 YEAR OUT - HYDROGRAPH SUMMARY:
Area 1.3000 ac Hyd Int 10.00 min Basc Flow
Peak flow 0.4179 cfs
Peak Time _ .
8.33 hrs _
Hyd Vol _. _._
0.2999 acft
Time (hr) Flow (cfs) .Time (hr) .Flow (cfs) Time (hr) Flow (cfs)
0.83
0.0000
14.67 __
0.1314
28.33
0.0776
1.00 0.0014 14.83 0.1286 28.50 0.0766
1.17 0.0040 15.00 0.1269 28.67 0.0756
1.33 0.0077 15.17 0.1261 28.83 0.0747
1.50 0.0121 15.33 0.1256 29.00 0.0737
1.67 0.0170 ] 5.50 0.1253 29.17 0.0727
1.83 0.0219 15.67 0.1237 29.33 0.0717
2.00 0.0242 15.83 0.1209 29.50 0.0706
2.17 0.0268 16.00 0.1192 29.67 0.0696
2.33 0.0296 16.17 0.1184 29.83 0.0685
2.50 0.0320 16.33 0.1178 30.00 0.0675
2.67 0.0342 16.50 0.1176 30.17 0.0664
2.83
0.0365
16.67 _..
01174
30.33
0.0653
3.00
0.0385
16.83 _..
0.1174
30.SU
0.0643
3.17 0.0404 17.00 0.1173 30.67 0.0631 `:
3.33 0.0423 17.17 0.1158 30.83 0.0620
,
3.50 0.0440 17.33 _
0.1131 31.00 _ _ ._
0.0609
3.67 0.0457 17.50 0.1114 31.17 0.0597
3.83 0.0475 17.67 0.1106 31.33 0.0586
4.00 0.0491 17.83 0.1101 31.50 0.0574 j
4.17 0.0508 18.00 0.1098 31.67 0.0562
4.33 0.0527 18.17 0.1082 31.83 0.0550
4.50 _
0.0544
18.33
0.1054
32.00 __ _
0.0538 i
4.67
0.0561
18.50 __ _
0.1037
32.17
0.0526
4.83
0.0580
18.67
0.1028
32.33 __._..
0.0513
5.00 0.0597 18.83 0.1023 32.50 0.0500
5.17 0.0615 19.00 0.1021 32.67 0.0488
5.33 0.0633 19.17 0.1007 32.83 0.0475
5.50 0.0650 19.33 0.1007 33.00 0.0462
5.67 0.0667 19.50 0.1006 33.17 0.0449
Si=~'_'ANTHfi ~I~G~ G4.1v".v8
~l
1
5.83 0.0685 19.67 0.1006 33.33 0.0436
6.00
0.0702
19.83
0.1005
33.50 _.
0.0423
__ ._._.
6.17 0.0720 20.00 0.1005 33.67 0.0408
--
6.33
0.0739
20.17
0.1004
33.83
0.0395
6.50 0.0757 20.33 0.1004 34.00 0.0381
6.67 _ __
0.0777 _
20.50 _
0.1003
34.17 __
0.0368
6.83 _.._.
0.0799
20.67
0.1003
34.33
0.0353
7.00 0.0819 20.83 0.1003 34.SU 0.0338
' 7.17 0.0841 21.00 0.1002 34.67 0.0324
7.33 0.0865 21.17 0.1002 34.83 0.0311
7.50 ___
0.0887
21.33
0.1001
35.00
0.0296
7.67 0.0928 21.50 0.1001 35.17 0.0279
7.83 _._
0.0990
21.67
0.1000
35.33
0.0264
8.00 0.3221 21.83 0.1000 35.50 0.0249
8.17 0.4127 22.00 0.0999 35.67 0.0235
8.33 0.4179 22.17 0.0999 35.83 0.0222
8.50 _._
0.4173
22.33
0.0998
36.00 _ . _
0.0202
1 8.67 0.4104 22.50 0.0997 36.17 0.0174
8.83 0.3887 22.67 0.0996 36.33 0.0151
9.00 0.3679 22.83 0.0995 36.50 0.0130
9.17 0.3429 23.00 0.0994 36.67 0.0113
9.33 . _ _ _----
0.3138
23.17
0.0993
36.83
0.0097
9.50 0.2914 23.33 0.0992 37.00 0.0084
9.67 0.2640 23.50 0.0991 37.17 0.0073
9.83 0.2397 23.67 0.0990 37.33 0.0063
10.00 0.2265 23.83 0.0989 37.50 0.0054
r 10.17 0.2146 24.00 0.0988 37.67 0.0047
10.33 _.
0.2024 ...
24.17 0.0985 37.83 0.0041
10.50 _.__ __
0.1952
24.33
0.0977
38.00
0.0035
10.67
0.1886 __
24.50
0.0970
38.17
0.0030
10.83 _
0.1809
24.67 _ _
0.0962
38.33 _
0.0026
11.00 0.1766 24.83 0.0955 38.50 0.0023
11.17
0.1728
25.00
0.0947
3 8.67 _.
0.0020
11.33 0.1687 25.17 0.0939 38.83 O.OOl7
11.50 0.1664 25.33 0.0931 39.00 0.0015
_. _ .. ~ _ _ _ _ V _...._.-..- ----.._._.__............_.........._.........._ .....................
1 __ _ __ _ ;
11.67 0.1637 25.50 0.0923 39.17 0.0013
i
1 ] .83 0.1603 25.67 0.0916 39.33 ___
0.0011
.,
12.00 0.1583 25.83 0.0907 39.50 0.0009
,
12.17 0.1558 26.00 0.0899 39.67 _
0.0008
12.33
0.1524
26.17
0.0891
39.83 __ __ _
0.0007
12.50 -- _
0.1505
26.33 _
0.0883
40.00 __
0.0006 E
12.67 0.1480 26.50 0 0874 40.17 0 0005
12.83 0.1447 26.67 0.0866 40.33 0.0005
13.00 0.1427 26.83 0.0857 40.50 0 0004 '
13.17 0.1417 27.00 0.0848 40.67 0.0003
13.33 _._
0.1411
27.17
0.0840
40.83 __-
0.0003
13.50 0.1408 27.33 0.0831 41.00 0.0003
13.67 0.1392 27.50 0.0822 41.17 0.0002 F
13.83 0.1364 27.67 0.0813 41.33 0.0002 x
14.00 0.1347 27.83 0.0804 41.50 0.0002
r _ _ - --
14.17 --__-----
0.1338 --- _ _
28.00 _ . _. _ __ __.__ .
0.0794 _ _
41.67 _--_____.---i
0.0001
14.33 0.1333 28.17 0.0785 41.83 0.0001
a
14.50 __
0.1331
_ _
28.33
0.0776
_
42.00
.__ . _.
0.0001
- _ _ __..:
100 YEAR OUT
HYDR OGR
-
APH SUMMARY:
ti _
Area _ _ - _ --_
1.3000 ac _ _ - -
Nyd Int ..
10.00 min . _ _ _ .._ ~ __
.Base Flow
Peak flow 0.6660 cfs
__ _ _ __ .Peak Time 8.17 hrs I-iyd Vol 0.4079 acft
Time (hr) Flow (cfs) .Time (hr) Flow (cfs) Time (hr) Flow (cfs)
~ 0.67 0.0000 14.83 0.1719 28.67 0.0784
0.83 0.0021 15.00 0.1697 28.83 0.0775
1.00 0.0059 15.17 0.1686 29.00 0.0765 {
1.17 0.0113 .15.33 0.1679 29.17 0.0756 1
,r,r 1.33 0.0181 15.50 0.1676 29.33 0.0746
1.50 0.0231 15.67 0.1653 29.50 0.0736 ~
~ 1.67 0.0266 15.83 0.1615 29.67 0.0726
1.83 0.0304 16.00 ' 0.1593 29.83 0.0716
2.00 0.0334 16.17 0.1582 30.00 0.0706
2.17 0.0366 16.33 0.1575 30.17 0.0695
I ..... --- _ _.. __ _ -- __ __ -._- _~. -.~.__._._ _:_ _
SAMANTHA R 1~GE v 4.10.0B
.i 6
i~
2.33
r__. 0.0395 16.50 0.1572 30.33 0.0685 ~'
2.50 __ _ _
0.0424
16.67
0.1570 _
30.50 _ _ _ -
0.0674
2.67 0.0450 16.83 0.1569 30.67 0.0663 ~
2.83 0.0475 17.00 0.1568 30.83 0.0653
3.00 0.0498 17.17 0.1547 31.00 0.0642 j
3.17 0.0520 17.33 0.1510 31.17 0.0631 j
~-._ _ _
3.33 __ - - -- ._ _
0.0540 _
17.50 _ __._ _
0.1489 _
31.33 ___~_ - - --i
0.0619
3.50 0.0560 17.67 0.1478 31.50 0 0608
3.67 0.0579 17.83 0.1471 31.67 0.0597
3.83
_ 0.0598 18.00 0.1468 31.83 0.0585
4.00 ___ _ _
0.0616
18.17
_
0.1445
32.00
_ ---
0.0573
. _.
4.17
0.0635
18.33 _
0.1407
32.17 _ ,
0.0562
r~
4.33 _._
0.0655
18.50 _
0.1385
32.33 _
0.0549
4.50 0.0673 18.67 0.1374 32.50 0.0537
4.67 0.0692 18.83 0.1367 32.67 0.0525 i
r__
4.83
0.0712
19.00
0.1364
32.83 0.0512
! 5.00 0.0730 19. ] 7 0.1341 33.00 0.0500
j 5.17 0.0749 19.33 0.1303 33.17 0.0487 ~
5.33 0.0768 19.50 0.1281 33.33 0.0475
~...
5.50
0.0787
19.67
_ _
- _ _
0.1270
33.50 ___ _~
0.0461 i
5.67 0.0805 19.83 0.1263 33.67 0.0448
5.83 0.0824 20.00 0.1259 33.83 0 0435
6.00 0.0842 20.17 01257 34.00 0.0422
6.17 0.0860 20.33 0.1256 34.17 0.0408
---- _ _
6.33 . _ ...._.__ __-
0.0880 --
20.50 - ----
0.1255 _
34.33 __-__ ---t
0.0394
6.50
0.0899
20.67 __
0.1255
34.50 _ __
0.0381
6.67 0.0920 20.83 0.1255 34.67 0.0367 j
~ 6.83 -
0.0942
21.00
0.1255
34.83 _ __;
0.0352
7.00 0.0963 21.17 0.1255 35.00 0.0337
7.17 0.0986 21.33 0.1255 35.17 0.0323
7.33 0.1144 21.50 0.1255 35.33 0.0310
~...
7.50 ___ _-__.
0.2551
21.67 __ - _
0.1255
35.50 _ __ - --I
0.0295 j
7.67
0.4032
21.83
0.1255
35.67 --_-_.
0.0278 1
7.83 0.5439 22.00 0.1255 35.83 0.0263
r..
8.00 _.. ___
0.6333
22.17
_
0.1234
36.00
0.0248 ~
SA'ANTHA ~3~v
~A~4 „
i~
14.00 0.1801 28. ] 7 0.0812 42.00 0.0002
-_
14.17
:_._
0.1790
28.33
0.0803
42.17 _
0.0001
14.33 __
0.1783
28.50
0.0794
42.33 __
0.0001
14.50 0.1780 28.67 0.0784 42.50 0.0001
14.67 0.1757 28.83 0.0775 42.67 0.0000
CONTROL STRUCTURE
Descrip: .Prototype Structure Increment 0.10 ft
Start EI. 330.0000 ft Max EI. 335.0000 ft'
- _ _
Orif Coeff _ --
0.62
Lowest Orif EI.
98.00
Lowest Diam 1.5820 in Dist to next 2.2300 ft
D2 5.0684 in Dist to next 0.3100 ft
D3 ___~
0.5859 in .
Dist to next
__
0.0000 ft
Stage Discharge Rating Curve
330.0000 ft 0.0000 cfs
0.0304 cfs 332.8000 ft 0.6447
_-__ -
0.0372 cfs 332.9000 ft 0.6919
ft 0.0480 cfs 333.1000 ft
ft 0.0526 cfs 333.2000 ft
330.7000 tt 0.0568 cfs 333.3000 ft 0.8526 cfs
330.8000 ft 0.0607 cfs 333.4000 ft 0.8879 cfs
330.9000 ft 0.0644 cfs 333.5000 ft 0.9218 cfs
331.0000 ft 0.0679 cfs 333.6000 ft 0.9544 cfs
--___._
331.1000 ft 0.0712 cfs 333.7000 ft 0.9859 cfs
331.2000 ft 0.0744 cfs 333.8000 ft 1.0163 cfs
__
331.3000 ft 0.0774 cfs 333.9000 ft 1.0458 cfs
ft 1.0745 cfs
__ ___
ft 1.1024 cfs
.6000 ft 0.0859 cfs 334.2000 ft 1.1296 cfs
- -. _ ____
.7000 ft 0.0886 cfs 334.3000 ft 1.1562 cfs
.8000 ft 0.0911 cfs 334.4000 ft 1.1821 cfs
.9000 ft 0.0936 cfs 334.5000 ft 1.2074 cfs
__
.0000 ft 0.0961 cfs 334.6000 ft 1.2322 cfs
1000 ft
RiDGc C~4.10.0~ °=,G~ 39
1
332.2000 ft 0.1007 cfs 334.8000 ft 1.2804 cfs
332.3000 ft 0.2874 cfs 334.9000 ft 1.3037 cfs
332.4000 ft - - - _
0.3926 cfs 335.0000 ft _ -
1.3267 cfs
332.5000 ft 0.4696 cfs 335.1000 ft 1.3493 cfs
335.0000 ft 1.3267 cfs
I .
i
1
~ ~ .
i
1
1
t
1
SA'ANTNA R{~~E J4.10.08 ?AC` 4~
F+'
1
1
r
' APPENDIX C - Geotechnical Report
1
i
G4.1 v.08 ?AGE 4
Gary A. Flowers, PLLC
Geological & Geotechnical Consulting
19532 12`h Avenue NE
Shoreline, WA 98155-1106
~
August 4, 2006
Project No. 06-079
Pacific Frontier, LLC
111 5th Street NE
Auburn
WA 98002
,
~ Attention: Mr. Jack Long
Subject: Geological/Geotechnical Assessment
Crystal Springs Property
Crystal Springs Road NW & Edwazds Road NW
~ Yelm, Washington
This report presents the results of our eolo icaU eotechnical evaluation of the a roximate 4.1
g g g PP
acre property located at the east side of the intersection of Crystal Springs Road NW and
Edwards Road NW in Yelm, Washington. It is our understanding that the property will be
developed to support single family residence lots. Site layout or grading plans were not available
at the time of this report.
~ Th
e purpose of our site evaluation was to document existing shallow soil and ground water
conditions on the property, and to provide geotechnical design recommendations for construction
of the proposed improvements.
1 EXISTING CONDITIONS
The subject site is an irregular triangulaz shaped parcel measuring approximately 4.1 acres. The
west side of the site slopes down from the adjacent road elevation to a lower flat azea occupying
the majority of the property with a slight slope to the northeast. Total elevation change across the
property was on the order of 20 feet. A single story residence and attached garage are located on
' the southwest corner of the site. Primary vegetation is field grass with a few shrubs and bushes.
Several fruit trees and deciduous trees were located along the western side of the property. A
small stream bounds the property on the east side. A utility easement with fiber optic lines bisects
the property in the east-west direction. There was a collapsed old well house, presumably with
an open well under it, to the north of the utility easement at the base of the west slope. .
Gary A. Flowers, PLLC.
19532 12'" Avenue NE Shoroline, Washington 98155-1106 206-417-7640
SAMAi~iTHA Rl3G= G=!.1.i.i;~ ~ ACE ~2
Crystal Springs Property Geological/Geotechnical Services Report
Yelm, Washington
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Subsurface Soil and Ground Water Conditions
In order to characterize the shallow subsurface soil and ground water conditions on the
properties, a series of 8 subsurface exploration pits were completed using small track-mounted
excavator provided by the client. The exploration pits permitted direct, visual observation of the
subsurface soils on the property. The exploration pits were logged by a licensed geologist and
immediately backfilled. The exploration pit locations are shown on the site and exploration plan
attached to this report.
The exploration pits revealed that the site was underlain by Spanaway recessional outwash sand
and gravel. Minor fill soil was encountered in the southwest corner of the property. The topsoil
~ layer was very non-uniform across the property. Little to no topsoil was encountered in the
exploration pits except for EP-4 and EP-7 where it was found to be 4 and 2 feet thick,
respectively. The topsoil layer supporting the field grass at the remaining explorations was about
2 to 6 inches thick before grading into the recessional sand and gravel. The topsoil was loose,
dry, dark brown, fine sandy silt loam.
The upper 4 to 5 feet of EP-8 consisted of loose, dry, brown, gravelly sand with some silt and
construction rubble. This material was fill soil of unlmown origin or age.
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Under the fill or topsoil layers in all of the exploration pits were Spanaway recessional sand and
gravel deposits. The recessional outwash was deposited from fluvial processes during the retreat
of the Vashon stade of the Fraser glacial period about 10,000 years ago. Infiltration into this unit
is typically moderate to rapid. The outwash sediments consisted of loose to medium dense with
depth, dry to damp, brown or gray-brown, sandy gravel and gravelly sand with minor silt. Often
the sediment layers contained a significant cobble and boulder content indicating a high energy
depositional environment. The outwash deposits extended below the termination depths of all of
our explorations at 5 to 10 feet. In EP-3 and EP-7, the sediment was saturated below 8 and 9 feet
respectively.
Hydrology
There was a small stream along the east side of the property that was highly overgrown by shrub
and blackberry vegetation. There was no evidence of erosion anywhere on the parcel that we
could observe but due to the dense vegetation along the stream corridor, the stream banks were
not visible. Crround water was encountered in EP-3 and EP-7 at roughly the same elevation,
about 8 to 9 feet below ground surface. The ground water likely represents the local water table
for this azea. The ground water elevation will vary with the time of year.
Gary A. Flowers, PI.L.C.
19532 12'~ Avenue iVE Shoreline, Washington 98155-1106 206.417-7640
S.A"viANTHA RlJv=
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Crystal Springs Property
Yelm, Washington
Seismic Hazards
Geological/Geoteehnical Services Report
Generally, there are four types of potential geologic hazards associated with Large seismic events:
1) surficial ground rupture; 2) seismically induced landslides; 3) liquefaction; and 4) ground
motion. The potential for each of these to impact the site is discussed below.
A few known fault zones occur in the Puget Sound region, however none are currently known in
the Yelm area. Fault zones in the Puget Sound region are currently being studied by the United
States Geological Service (LJSGS) and have been determined to be active and capable of
producing large eazthquakes. Much is still to be learned about these fault systems but it is
generally hypothesized that their recurrence interval is several thousand years. Due to the
suspected long recurrence interval and the lack of known surficial faults traces, the potential for
surficial ground rupture is considered to be low during the expected life of the proposed
structures.
Due to the free draining nature of the sediments comprising the slope and its relatively low
topographic relief, it is our opinion that the potential risk of damage to the proposed structure, by
lazge scale seismically induced landsliding, is low.
Based on the density and grain size distribution of the sediments encountered in our exploration
pits, it is our opinion that the risk of liquefaction on this site is low.
Based on the encountered stratigraphy, structural design of the project should be consistent with
2003 International Building Code (IBC) guidelines. In accordance with Table 1615.1.1 of the
2003 IBC, the subject site would be classified as Site Class D.
CONCLUSIONS AND RECOMMENDATIONS
On the basis of our geologic research and field explorations, the property will be suitable for the
planned development. The upper surficial silty fine sandy loam topsoil where encountered on the
site may be problematic for structural development and should be removed from foundation
areas. Similarly, the old fill soil where encountered should be removed and replaced with
documented structural fill from all foundation or roadway areas. The near surface medium dense
recessional sand and gravel outwash or dense lodgment till sediment will be capable of providing
suitable foundation support for the planned roadways, pazking areas and structures.
The old water well on the site will need to be abandoned according to Washington State Dept. of
Ecology (DOE) standards. A well abandonment record will need to be filed with DOE and as
such, a licensed well driller should be contracted to perform this work.
Gary A. Flowers, PLLC.
19532 12m Avenue N6 Shoreline, Wachinglon 98155-I 106 206-417-7640
Si;:`:'A^tT~~ I~v~ x4.10.08
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Crystal Springs Property GeologicaUGeotechnical Services Report
Yelm, Washington
Site Grading
The existing vegetation on the site shall be removed from all areas planned to be graded as part
of the planned development. The organic topsoil is relatively thin in most areas and should be
should be removed from all structural areas even where it is 2 to 4 feet thick.
A grading plan was not available at the time this study was completed. As such, we are unsure as
to fmal grading plans for the site. However, it is anticipated that some structural fill will be
required to develop the planned property. Structural fill is non-organic soil that is near optimum
moisture content. The fill soil must be placed in maximum 8-inch loose lifts with each lift being
compacted to a dense, non-yielding condition prior to installation of the succeeding lift. The
moisture content must be neaz enough to optimum moisture content to allow the fill to achieve
the required compaction. Compaction effort must be applied to achieve a minimum of 95
percent of the modified Proctor maximum dry density per ASTM:D-1557. In addition to being
monitored by a representative of this firm, the placement and compaction of structural fill should
be tested using a nuclear densometer to verify that suitable compaction is being obtained.
In the case of utility trench backfill, the structural fill should be placed and compacted in
accordance with current local or county codes and standards. The top of all compacted fill
should extend horizontally outwazd a minimum distance of 3 feet beyond the location of
' perimeter footings or pavement edges before sloping down at a maximum angle of 2H:1 V.
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It should be the responsibility of the contractor to maintain safe slope configurations since the
contractor is continuously on-site. As is typical with earthwork operations, some sloughing and
raveling may occur and cut slopes may have to be adjusted in the field. It may be necessary to
cover the sides of temporary slopes with plastic or otherwise protect them from the elements to
minimize sloughing and erosion. For estimating purposes, we anticipate that temporary,
unsupported cut slopes can be made at an inclination of 1.SH:1V (Horizontal:Vertical).
Permanent, unsupported cut or structural fill slopes should not exceed a gradient of 2H:1 V.
Permanent, non-structural fill slopes should not exceed a gradient of 4H:1 V.
Foundation Recommendations
The planned residences may be set to beaz on documented structural fill soil placed as discussed
above or on undisturbed medium dense gravely sand on-site soils. An allowable soil bearing
value of 2000 psf may be used in the design of the house footings, including both dead and live
loads. An increase of one-third may be used for short-term wind or seismic loading. Perimeter
footings for the proposed structures should be buried a minimum of 18 inches into the
surrounding soil for frost protection. Settlement of footings placed as detailed herein should be
less than 1 inch between comparably loaded foundations. However, foundations placed on
disturbed soil may result in increased settlement. Steps in the foundation grade are acceptable
Gary A. Flowers, PLLC.
19532 12`" Avenue AIE Shoreline, Wavhington 98155-1106 206-417-7640
SAFr.4;ti~HA RI!:JGE 04.1v.~8 PAGE 45
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Yelm, Washington
provided that none of the foundations are set to beaz adjacent to the step. A 1 H:1 V load line
extending down from the edge of the foundation must not daylight on a cut slope. All foundation
excavations should be inspected by a representative of this firm, prior to concrete placement, to
' verify that the design bearing capacity of the soils has been attained and that construction
conforms to the recommendations contained in this report.
Lateral loads can be resisted by friction between the foundation and the supporting soils, and/or
by passive earth pressure acting on the buried portions of the foundations. The foundations must
be backfilled with structural fill compacted to a dense, nonyielding condition to achieve the
passive resistance provided below. The structural fill must extend horizontally outward from the
embedded portion of the foundation a distance equal to at least three times the embedment depth
over which the passive resistance is applied. We recommend the following design parameters.
• Passive equivalent fluid = 250 pcf
• Coefficient of friction = 0.40
The above values are allowable and include a factor of safety of at least 1.5.
Floor Support Recommendations
~ Slab-on-grade floors should be set to bear on undisturbed native soils or structural fill in a firm,
unyielding condition. A capillary break layer consisting of 4 inches of washed pea gravel and a
heavy duty (minimum 10 mil), polyethylene plastic vapor barrier should be provided under any
floor slabs where moisture intrusion is a concern. The on-site clean sand and gravel, if free of
silt, may also be used as a capillary break layer. If the vapor bamer becomes compromised in
>r any way during construction it should be replaced or an additional layer added. Penetrations
through the vapor barrier should be wrapped and taped.
f Site Drainage
1 All storm water runoff from impervious surfaces should be collected and piped into an approved
storm water drainage system. Individual lot infiltration trenches or dry wells would be an option
for this site. Footing drains are likely not needed for this site provided the foundations are placed
atop the clean sand and gravels encountered in our explorations. If footing drains are utilized
they should consist of rigid, perforated, PVC pipe sun-ounded by washed pea gravel. The level of
the perforations in the pipe should be set approximately at the bottom of the footing and the
drains should be constructed with sufficient gradient to allow gravity discharge away from the
~ buildings. Footing drains that will have more than 8 feet of backfill should be constructed of
schedule 3034 or better sewer grade pipe to minimise potential for collapse. Roof and surface
runoff should not dischazge into the footing drain system, but should be handled by a separate,
rigid, tightline drain that discharges into an approved storm water conveyance system. In
~ planning, exterior grades adjacent to walls should be sloped downward away from the structure
to achieve surface drainage.
' Gary A. Flowers, PLLC.
19532 12t° Avenue NE Shoieiine, Washington 98155-1106 206-017-7640
SAFJANTHA ?IQGF 04.1 x.08 --__.....____._-.........._........____.-SAGE 46
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Crystal Springs Property GeologicaUGeotechnical Services Report
Yelm, Washington
Due to the high ground water table encountered in several of the explorations, a large scale
infiltration pond may not be suitable for this site. Additional in-situ testing and ground water
modeling analysis should be performed to evaluate for ground water mounding if an infiltration
pond is to be utilized. However, individual lot infiltration systems are suitable for the residential
properties. For roadway runoff shallow infiltration ditches along the roadway may be an option
provided suitable pre-treatment can be accomplished. Any infiltration facilities should penetrate
through the loamy fine sand to the underlying recessional outwash sediments.
The materials encountered in our exploration pits would be classified as sand per the USDA
Textural Triangle. Per the Dept. of Ecology's Western Washington Storm Water Manual, these
materials have an allowable short term infiltration rate of 8.0 inches per hour and an estimated
long term infiltration rate of 2.0 inches per hour with a correction factor of .4. Due to some
variability of the sediments on this site, and the relatively high water table, it is our opinion that
the higher correction factor is appropriate and a maximum design rate of 2.0 inches per hour
should be used for this site.
The design engineer should take this information into account during the design process. The
infiltration facilities should be developed in accordance with requirements of the local
jurisdiction for storm water runoff.
SUMMARY
Based on our site reconnaissance and subsurface explorations the site appears to be suitable for
the proposed development provided the recommendations presented herein are properly
implemented.
We recomumend that we be retained to review those portions of the plans and specifications that
pertain to grading or foundation installations to determine that they are consistent with the
recommendations of this report. Construction monitoring and consultation services should also
be provided to verify that subsurface conditions aze as expected. Should conditions be revealed
during construction that differs from the anticipated subsurface profile, we will evaluate those
conditions and provide alternative recommendations where appropriate.
Field construction monitoring and observation services should be considered an extension of this
initial geotechnical evaluation, and are essential to the determination of compliance with the
project drawings and specifications. Such activities would include site clearing and grading,
subsurface drainage, foundafions bearing and fill placement and compaction.
Gary A. Flowers, PLLC.
19532 12i6 Avenue NE Shoreline, Washington 98155-1106 206-417-7640
..i --, ... t': t1:-1 ti~JVC U4, tw..%v Ji-1vv ~7
(:ryslaf.Sprin~s Proper{t' GeologicaL~Gcnlechnicaf ,Ser~•ices Rep<~r1
f efm. lf'ashinglon
(hu findings and reconunendations provided in this report were prepanecf in accordance with
generally accepted principles of engineering geology and gcotechnical engineering as practiced in
the Puget Sound area at the time this report vwas submitted. We make no other warranty, either
express or implied.
Sincerely,
EXPIRES it-28
Jamey S. Batienmann, P.E., L.G.
Geotechnical Cngineer
Attachments: Site Plan
Appendix A -Exploration Pit Logs
Gary A. Flowers, PLLC.
195)2 12°iAvtnaci:L Shcxclinc, WachinglcmyglSS-IIU6 2(1617-7440
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Gary A. Flowers, P.G., P.F.G.
8ngincering Geologist
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Geological/Geotechnical Services Report
APPENDIX A
EXPLORATION LOGS
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Gary A. Flowers, PLI.C.
19532 12°i Avenue NE Shoreline, Washington 98155-1 l06 206.417.7640
EXPLORATION PIT LOG
0 Number EP-1
1
2
3
4
5
6
7
8
9
10
11
12
SPANAWAY RECESSIONAL OUTWASH
Loose to medium dense, dry to damp, brown, sandy gravel with cobbles.
13 '
SWSUrrace condroons Oepicwd represent our observatiar. at Me qme enq locatgn d Nrs exporatory note, nwdirred 5y geologic
inaerprotation, engineering analysts, and tudgmerq. They are not neoessariy repwsergative d odrer qmp and IOtafi011. Ya3 wiN not
accept tesponsAility (a the use or in[erprebtion py others of ettorrtlati0n presented on ttrs tog.
GARYA. FLOWERS, PLLC
BOH @ 6'
Minor Caving
No Ground Water Seepage
Crystal Springs Property
Yelm, Washington
July 10, 2006
vf:~ ."'~IVTNA RID^v~ 04.1`.:.vd
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SArI"AN ~ FiA RI~G~ 04.1 v.^v3 ?AGE ~2
EXPLORATION PIT LOG
o Number EP-3
1
2
3
4
5
6
7
8
9
10
11
NISC2UALLY LOAMY FINE SAND
Loose, dry, dark brown, fine sandy loam.
12
13
SrAsurface condimnx oerycteO tePrexN our ooservation e< ine Ume and txedon Of Ihls a:poratory IItNe, moyreW Dy g~lopk
inlerpreuaon, engineering anaysis, and Na9men1 They ate not neoeesarily reprEgentatire d oamr Wines and locatgr:, Nk wib no7
accept tesponaiOiMy lar Ne use or nlerpretstbn M Mhero o! ntarmalgn preserµea p1 this pp.
Crystal Springs Property
GARYA. FLOWERS, PLLC Yelm, Washington
July 10, 2006
SPANAWAY RECESSIONAL OUTWASH
Loose to medium dense, dry to damp, brown, sandy gravel and gravelly sand with
cobbles and occaisional boulders.
64.10.08
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X4.1 G G8 ?:,G~ 54
EXPLORATION PIT LOG
o Number EP-5
1
2
3
4
5
6
7
8
9
10
11
12
13
SPANAWAY RECESSIONAL OUTWASH
Loose to medium dense, dry to damp, brown, sandy gravel with cobbles.
BOH@5'
Minor Caving
No Ground Water Seepage
• --- - - ~----- - - -. ... .. ...~ a....,... „r~,o~y..epresemsave a omen ernes ana location. Nu wil nol
aC..ept nesponsibilily for pre use or ineerpretation tiY apiers d infarmslior, presenley on pia Ipg.
GARYA. FLQWERS, PLLC
Crystal Springs Property
Yelm, Washington
July 10, 2006
.....
v4. ru.v • P
EXPLORATION PIT LOG
o Number EP-6
1
2
3
4
5
6
7
8
9
10
11
12
13
SPANAWAY RECESSIONAL QUTWASH
Loose to medium dense, dry to damp, brown, sandy gravel with cobbles.
BOHQS'
Minor Caving
No Ground Water Seepage
Oll OhLwNlinn at ew li.
••+o.~.e~mAn. enpineertrtg anaycis, and ~ud9metw. iTrey are not neoesaarpy rapreaentative of etrer emss and toeetbn~ We wMi not
accept respons:ellny for the use or inlrtrprelaEOn b'f' atfrera od inbrmetbn presented on Otis b9.
GARYA. FLOWERS, PLLC
Crystal Springs Property
Yelm, Washington
July 10, 2006
_-.....--_...__.---...._.._._...... G4.
:':"~NTH~1 RfDGc
Q Number EP-7
EXPLaRATI~N PIT L0~
NISQUALLY LOAMY FINE SAND
Loose, dry, dark brown, fine sandy loam with trace gravel.
1
2
3
a
5
6
7
8
9
10
11
12
13
SPANAWAY RECESSIONAL OUTWASH
Medium dense, damp, light brown, fine to medium sand; with some silt and trace gravel
Medium dense, damp to wet with depth, brown, gravelly sand with cobbles and
boulders.
Subsurface oonditwns depicted repesent our nhserration x are Urns aM bcation of fn6 e~loratory hole. modltlted b1' geotogo
Merprelation, enpineerinp anarysis, an0 peagmenl TToey AB nol neCeS3aAy reprt:sentedvt: of carer rimes and bastion. YVe will nol
accopt rasponsllzlity for are use or interpretatbn by others d information presented on axis log.
GARYA. FLOWERS, PLLC
Crystal Springs Property
Yelm, Washington
July 10, 2006
Sfi~'Ati'FiA ~1DG~ ~4,1~.OE PAGE ::~