HomeMy WebLinkAboutMiscSewall Wetland Consulting, Inc.
July 14, 2014
Justin Holland
Prospect Development, LLC
19410 Highway 99, Suite A #135
Lynwood, WA 98036
IDBox880
Fall Oty, WA 'ID24
Re: Weston Heights Preliminary Plat-Critical Areas Update
SWC Job#l4-l71
Dear Justin,
Phone: 253-859--0515
Sewall Wetland Consulting, Inc. prepared a Critical Areas Report for Robert Johnseine
for the "Pleasant Path Plat", dated October 9, 2012. This report was for Pleasant Path
Plat which was to be located on the east side of Nile Avenue NE (148th Avenue SE) in
the City of Renton, Washington (the "site"). Specifically, the site consists of two
abutting irregular shaped parcels (Parcels# 11230590 IO & 092) located in a portion of the
SW Y,, of Section 11, Township 23 North, Range 5 East of the Willamette Meridian in
King County, Washington.
This letter is to confirm that the findings of that report are still accurate as far as the
delineation, and associated rating and buffer.
If you have any questions or need any additional information please contact me at (253)
859-0515 or by email at esewall@sewallwc.com.
Sincerely,
Sewall Wetland Consulting, Inc.
Ed Sewall
Senior Wetland Ecologist PWS #212
l
July 10, 2014
Jill Ding
City of Renton
Depaitment of Community & Economic Development
Renton, WA 98057
Re: Weston Heights Preliminary Ph1t Wetland Stncly
CORE Project No. 14040
Dear Jill Ding:
I am writing to give my permission to use the wetland study that was done for my prope1ties under the
name Pleasant Path for this submittal as Weston Heights. The parcels involved are 650 & 684 Nile Ave.
N.E., 112305 92,1123059010.
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October 9, 2012
Robert Johnseine
9805 NE 116th Street, Suite 7499
Kirkland, Washington 98034
RE: Critical Areas Report -Pleasant Path
SWC Job#A6-209
1.0 INTRODUCTION
27641 Covington Way SE #2
Covington WA 90012
Phone: 253-859-0515
Fax: 253-852-4Z32
This report describes jurisdictional wetlands on the 3. 93 acre proposed Pleasant Path Plat
located on the east side of Nile Avenue NE ( I 48'h Avenue SE) in the City of Renton,
Washington (the "site"). Specifically, the site consists of two abutting irregular shaped
parcels (Parcels # 1123059010 & 092) located in a portion of the SW V. of Section 11,
Township 23 North, Range 5 East of the Willamette Meridian in King County,
Washington.
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Sewall Wetland Consulting, Inc.
October 9, 2012
Page 2
The site consists of an undeveloped parcel containing both forest and pasture areas.
The site is proposed to be subdivided into I I single family residential Lots with
associated roads and infrastructure.
2.0 METHODOLOGY
The site was originally delineated by Sewall Wetland Consulting in 2006 and 2007. This
is documented in the attached "Johnsein Property-Revised Wetland Analysis Report
and Conceptual Mitigation Plan dated October 10, 2006 and revised June 20, 2007. This
was reviewed and accepted by the City as part of the previous submittal on this project
between 2009-2010 (City of Renton File No LUA09-120 (L07S0018)).
Ed Sewall of Sewall Wetland Consulting, Inc. inspected the site in October of2012 to
confirm the findings regarding the delineation of this wetland remain the same using
methodology described in the Washington State Wetlands Identification Manual
(W ADOE, March 1997). This is the methodology currently recognized by the City of
Renton and the State of Washington for wetland determinations and delineations. The
site was also inspected using the methodology described in the Corps of Engineers
Wetlands Delineation Manual (Environmental Laboratory, 1987), and the Western
Mountains, Valleys and Coast region Supplement (Version 2.0) dated June 24, 2010, as
required by the US Army Corps of Engineers. Soil colors were identified using the 1990
Edited and Revised Edition of the Munsell Soil Color Charts (Kollmorgen Instruments
Corp. 1990).
The Washington State Wetlands Identification and Delineation Manual and the Corps of
Engineers Wetlands Delineation Manual/Regional Supplement all require the use of the
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Sewall Wetland Consulting, Inc.
October 9, 2012
Page 3
three-parameter approach in identifying and delineating wetlands. A wetland should
support a predominance of hydrophytic vegetation, have hydric soils and display wetland
hydrology. To be considered hydrophytic vegetation, over 50% of the dominant species
in an area must have an indicator status of facultativc (F AC), facultative wetland
(FACW), or obligate wetland (OBL), according to the National List of Plant Species That
Occur in Wetlands: Northwest (Region 9) (Reed, 1988). A hydric soil is "a soil that is
saturated, flooded, or ponded long enough during the growing season to develop
anaerobic conditions in the upper part". Anaerobic conditions are indicated in the field
by soils with low chromas (2 or less), as determined by using the Munsell Soil Color
Charts; iron oxide mottles; hydrogen sulfide odor and other indicators. Generally,
wetland hydrology is de lined by inundation or saturation to the surface for a consecutive
period of 12.5% or greater of the growing season. Areas that contain indicators of
wetland hydrology between 5%-12.5% of the growing season may or may not be
wetlands depending upon other indicators. Field indicators include visual observation of
soil inundation, saturation, oxidized rhizospheres, water marks on trees or other fixed
objects, drift lines, etc. Under normal circumstances, indicators of all three parameters
will be present in wetland areas.
3.0 OBSERVATIONS
3.2.2 Wetlands
As described the 2007 report, a single Category 2 wetland is located on the eastern side
of the site. The delineation of the wetland remains the same as in 2007 with a well-
defined edge.
According to the criteria in City of Renton Municipal Code (RMC) Chapter 4-3-050.M. I,
Wetland A would be classified as Category 2 wetland. Category 2 wetlands are defined
in the Code as follows;
ii. Category 2: Category 2 wetlands are wetlands which meet one or more
of the following criteria:
(a) Wetlands that are not Category I or 3 wetlands; and/or
(b) Wetlands that have heron rookeries or osprey nests, but are not
Category I wetlandY; and/or
(c) Wetlands of any size located at the headwaters of a watercourse,
i.e., a wetland with a perennial or seasonal outflow channel, but with no defined influent
channel, but are not Category I wetland5; and/or
(d) Wetlands having minimum existing evidence of human-related
physical alteration such as diking, ditching or channelization: and/or
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Wetland A best meets this rating as a wetland with minimum evidence of human related
physical alteration, but not meeting the criteria of a Category I or Category 3 wetland.
Typically, Category 2 wetlands have a 50' buffer measured from the wetland edge.
4.0 PROPOSED PROJECT
The proposed project is the construction of a l 4 lot subdivision with associated access
road, and storm water facility, all located along the western side of the site. In addition
and at the request of the City, a walking trail for residents will pass through the wetland
and buffer to allow access to the open space on the east side of the site.
In order to allow a reasonable density oflots on the site, the project proposed a
combination of paper fill and buffer averaging to allow the site to be developed in a
manner that economically feasible yet still protects and enhances the critical area and its
buffer. As a result, it is our intention to "paper fill" 191 sf of Category 2 wetland so as to
have the minimum 25' buffer, as well as average l l ,509sf of buffer as depicted on the
attached conceptual mitigation plan. Impacts to wetlands and buffers must be justified
through a mitigation sequence as detailed in City of Renton Code. This sequencing
requires addressing the following criteria;
a. Avoid any disturbances to the wetland or buffer;
As detailed above, avoidence of the wetland and its buffer is economically feasible as it
would eliminate all the lots (total of5) along the west side of the site, which is> 1/3 of
the project. The application of this project also negates the need to cross the wetland
with a road that was already approved in the King County approval of this plat prior to
annexation.
b. Minimize any wetland or buffer impacts;
The project has been designed to minimize the impact by leaving the entire east side of
the site undeveloped with the exception of the trail. The buffer will be reduced to the
minimum allowed by Code (50%) and transferred to the eastern side of the wetland. This
buffer is already functionally recued on the west side where the proposed reduction will
occur, as it has been converted to lawn and other portions are covered with blackberry.
The small amount of paper fill proposed is being proposed to meet the minimum 25'
buffer criteria. The wetland creation proposed on the east side of the wetland will
compensate for this impact and will restore some of the overall wetland size that has been
reduced in the past ofl~site to the south.
The trail is being proposed through the buffer and wetland at the request of the City. The
trail has been designed at a minimum width (4') to create a functional nature trail through
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the critical areas. The trail will be constructed on "pin piles" through the wetland, which
is generally not considered a wetland impact.
c. Restore any wetlands or buffer impacted or lost temporarily; and
Restoration of this wetland in this location would not be feasible due to the fact it is
genera II y not degraded.
d. Compensate fi,r any permanent wetland or buffer impacts by one of the following
methods:
i. Restoring aformer wetland and provide buffers at a site once exhibiting
wetland characteristics to compensate for wetlands lost;
This is not feasible on this site as there is no former wetland to restore.
ii. Creating new wetlands and buffers for those lost; and
As previously described and is depicted on the attached Conceptual Mitigation Plan, the
proposed project will compensate for the "paper fill" of 191 sf of Category 2 wetland at a
3:1 ratio by creating 818sfofwetland along the east side of the existing wetland edge.
This area will be excavated out and brought to grade with 12" of topsoil to an elevation
matching the existing wetland. As depicted on the attached Conceptual Mitigation Plan,
8 l 8sf of area will be excavated out to a similar depth to the existing wetland to intercept
the surficial groundwater table and create conditions favorable to create wetland
hydrology. This area will then be graded back at a slope no steeper than 3:1
(horizontal:vertical). The area will then be planted with a mix of native trees, shrubs and
herbaceous species and will also include several habitat features (logs) to increase its
habitat function. The goal will be to create at least 8 l 8sf of area meeting all three
wetland criteria (hydric soils, hydrophytic vegetation, and wetland hydrology) as
specified in the Washington State Wetlands Identification Manual (W ADOE, March
1997).
As described in Code; "Any applicant proposing to alter wetlands may propose to restore
wetlands or create new wetlands, with priority first for on-site restoration or creation
and then second, within the drainage basin, in order to compensate for wetland losses.
Restoration activities must include restoring lost hydrologic, water quality and biologic
junctions". Additionally, Code states" Where feasible, created or restored wetlands
shall be a higher category than the altered wetland. In no cases shall they be lower".
Code specifies the following mitigation ratios for wetland impacts;
i. RATIOS FOR WETLANDS CREATION OR RESTORATION:
Wetland CategorylVegetation TypelCreation/Restoration Ratio
Category 1 Forested
Scrub-shrub
Emergent
Category 2 Forested
Scrub-shrub
Emergent
Category 3 Forested
Scrub-shrub
Emergent
6 times the area altered.
3 times the area altered.
2 times the area altered.
3 times the area altered.
2 times the area altered.
1.5 times the area altered.
1.5 times the area altered.
1.5 times the area altered.
1.5 times the area altered.
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Buffer averaging will be utilized for the western buffer of Wetland A. In addition, the
remaining 25' buffer of Wetland A along its west side will be enhanced to increase its
functional value and remove exotic blackberry. Enhancement of this area will include
hand removal of blackberry, and installation of a native conifer understory as well as
native trees and shrubs in areas that are completely covered in blackberry. This will
restore a native shrub stratum in this area through removal of the exotic blackberry and
will also initiate the return of a conifer component to this forested area which is not
present at this time.
As requested by the City, a recreational trail will pass through the buffer and over the
wetland along its south end, and then with a loop on the eastern side of the site outside
the buffer. The areas of buffer impact from this bark covered 4' path will be
compensated through the use of buffer averaging and as allowed by Code. Code allows
trails through the outre part of the wetland buffer.
In order to access the east side of the site the trail will cross the wetland using pin piles to
eliminate any impacts to the wetland except for the small cross section of the pin pile.
The resulting wetland creation and buffer enhancement area will be monitored for 5 years
as required by Code.
If you have any questions regarding this report, please call us at (253) 859-0515 or at
esewall@sewallwc.com .
Sincerely,
Sewall Wetland Consulting, Inc.
Ed Sewall
Senior Wetlands Ecologist PWS #212
Attached: Johnsein Property-Revised Wetland Report June 20, 2007
REFERENCES
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Coward in, L., V. Carter, F. Go let, and E. LaRoe. 1979. Classification of Wetlands and
Deepwater Habitats of the United States. U.S. Fish and Wildlife Service,
FWS/OBS-79-31, Washington, D. C.
Daubenmire, R. 1959. A canopy-coverage method ofvegetational analysis. Northwest
Science 33:43-64.
Diers, R. and J.L. Anderson. 1984. Development of Soil Mottling. Soil Survey Horizons,
Winter 1984, pg 9-15.
Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual,
Technical Report Y-87-1. U.S. Army Corps of Engineers Waterways Experiment
Station, Vicksburg, Mississippi.
City of Renton Municipal Code
Hitchcock, C. and A. Cronquist. 1976. Flora of the Pacific Northwest. University of
Washington Press, Seattle, Washington.
Munsell Color. 1988. Munsell Soil Color Charts. Kollmorgen Instruments Corp.,
Baltimore, Maryland.
National Technical Committee for Hydric Soils. 1991. Hydric Soils of the United States.
USDA Misc. Pub!. No. 1491.
Reed, P., Jr. 1988. National List of Plant Species that Occur in Wetlands: Northwest
(Region 9). 1988. U. S. Fish and Wildlife Service, Inland Freshwater Ecology Section, St.
Petersburg, Florida.
Reed, P.B. Jr. 1993. 1993 Supplement to the list of plant species that occur in wetlands:
Northwest (Region 9). USFWS supplement to Biol. Rpt. 88(26.9) May 1988.
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1.0 CONCEPTUAL MITIGATION PROJECT OVERVIEW
October 9, 2012
Page 8
To compensate for the paper fill ofa 191sfCategory 2 wetland, it is proposed to create
818sf of wetland along the east side of Wetland A, a Category 2 wetland, as well as
enhance the averaged buffer along the west side of the wetland.
2.0 MITIGATION CONCEPT AND GOALS
2.1 Mitigation Concept
The mitigation proposal is to enlarge the existing Category 2 wetland on the site by 8 l 8sf
and enhance 9,930sf of the western buffer area. The wetland and buffer enhancement
areas will be densely planted with native vegetation. The use of diverse native plantings
are expected to significantly improve the overall function of the wetland and buffer as it
will remove dense thickets of exotic blackberry as well as add emergent and shrub plant
communities into what is now, a single class forested wetland.
2.2 Mitigation Goals
2.2.1 Create 818sf of forested wetland.
2.2.2 Enhance 9,930sf of the western wetland buffer and will consist of exotic
vegetation removal and replanting with native tree and shrub species.
3.0 CONSTRUCTION SEQUENCE
The construction sequence of this project will be implemented as follows:
3. I Pre-construction meeting
3 .2 Construction staking
3 .3 Construction fencing and erosion control
3 .4 Clearing and grading
3.5 Stabilization of mitigation area
3.6 Plant material installation
3. 7 Construction inspection
3.8 Agency approval
3.9 Monitoring inspection and reporting
3.10 Silt fence removal
3.11 Project completion
3.1 Pre-construction Meeting
A pre-construction meeting will be held on-site prior to commencement of construction,
to include the biologist, the City, and the contractor. The approved plans and
specifications will be reviewed to ensure that all parties involved understand the intent of
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the construction documents, specifications, site environmental constraints, sequences, and
inspection requirements.
3.2 Construction Staking
The limits of clearing and grading near the critical areas will be marked in the [1eld by a
licensed professional land surveyor prior to commencement of construction activities.
3.3 Construction Fencing & Erosion Control
All erosion control measures adjacent to the critical areas, including silt fencing and
orange construction fencing, will be installed. Erosion control fencing will remain
around the mitigation area until clearing, grading and hydroseeding are complete in
upland areas outside the critical areas.
3.4 Clearing & Grading
Clearing and grading in and near the existing sensitive area will be per the approved Final
Mitigation Plans.
3.5 Stabilization of Mitigation Area
All graded areas in the wetland or buffer will be stabilized with native hydroseed mix or
mulch upon completion of grading. Orange construction fencing and erosion control
fences will be restored (if necessary) and placed around the critical areas.
3.6 Plant Material Installation
All plant material will be planted by hand per detail and Construction and Planting Notes.
The Mitigation Plan specifies the required size, species, quantity, and location of plant
materials to be installed. The contractor will re-seed or over-seed all hydroseeded areas
disturbed during the planting process. Upon completion of the planting, the erosion
control fencing will be restored and repaired. Plant substitutions or modifications to
locations shall be approved in writing by the Owner's biologist prior to installation.
3. 7 Construction Inspection
Upon completion of installation, the biologist will conduct an inspection to confirm
proper implementation of the Mitigation Plan. Any corrections, substitutions or missing
items will be identified in a "punch list" for the landscape contractor. Items of particular
importance will be soils in pits, pit size, plant species, plant size, mulch around pits, and
tree staking.
Upon completion of planting, if installation or materials vary significantly from the
Mitigation Plan, the contractor will submit a reproducible "as-built" drawing to the
Owner.
3.8 Agency Approval
Following acceptance of the installation by the City, the biologist should prepare a letter
granting approval of the installation.
3.9 Monitoring
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The site will be monitored for 5 years to insure the success of the mitigation project.
3.10 Silt Fence Removal
Erosion control fencing adjacent to the mitigation area will remain in place for at least
one year, and/or until all areas adjacent to the mitigation area have been stabilized. The
City may recommend that the fencing remain in place for a longer duration.
4.0 CONSTRUCTION AND PLANTING NOTES
4.1 Site Preparation & Grading
4.1.1 The Landscape Contractor will approve existing conditions of subgrade prior to
initiation of any mitigation installation work.
The Landscape Contractor will inform the Owner of any discrepancies between the
approved construction document and existing conditions.
4.1.2 The General Contractor will flag the limits of clearing with orange construction
fencing and will observe these limits during construction. No natural features or
vegetation will be disturbed beyond the designated "limits of clearing".
4.1.3 The Landscape Contractor will hand grub all blackberry varieties onsite. Weed
debris will be disposed of off site.
4.1.4 The wetland area will be excavated to the depths shown on the Final Mitigation
Grading Plan and brought to grade with 8" of topsoil. The biologist will be on-site to
confirm the grading is acceptable for planting.
4.2 Plant Materials
4.2.1 All plant materials will be as specified in the plant schedule. Only vigorous plants
free of defects, diseases and infestation are acceptable for installation.
4.2.2 All plant materials will conform to the standards and size requirements of ANSI
Z60.l "American Standard for Nursery Stock". All plant materials will be native to the
northwest, and preferably the Puget Sound Region. Plant materials will be propagated
from native stock; no cultivars or horticultural varieties will be allowed. All plant
materials will be grown from nursery stock unless otherwise approved.
4.2.3 All nursery grown plant materials will be in containers or balled and burlapped.
Bare root plantings will be subject to approval.
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42A All plant materials stored on-site longer than two (2) weeks will be organized in
rows and maintained by the contractor at no additional cost to the owner. Plant materials
temporarily stored will be subject to inspection and approval prior to installation,
4,2,5 Substitution requests must be submitted in writing to the Owner and approved by
the Owner's biologist in writing prior to delivery to site,
4,2,6 All plant materials will be dug, packed, transported and handled with care to ensure
protection from injury. All plant materials to be stored on site more than 24 hours will be
heeled into topsoil or sawdust Precautionary measures shall be taken to ensure plant
materials do not dry out before planting, Wetland plants will be shaded and saturated
until time of installation, Immediately after installation the mitigation planting area will
be saturated to avoid capillary stress,
4.2.7The contractor will verify all plant materials, the quantities shown on the planting
plan, and the plant schedule, The quantity of plant materials shown on the plan takes
precedent over the quantity on the plant list
4-3 Plant Installation
43, I All plant materials must be inspected prior to installation to verify conformance of
the materials with the plant schedule including size, quality and quantity. Any plant or
habitat materials deemed unsatisfactory will be rejected.
4.3 2 All plant materials delivered and accepted should be planted immediately as
depicted on the mitigation plan, Plant materials not planted within 24 hours will be
heeled-in per note 3 .2.6. Plant materials stored under temporary conditions will be the
sole responsibility of the contractor. Plants will be protected at all times to prevent the
root ball from drying out before, during, or after planting.
43.3 All planting pits will be circular with vertical sides, and will be sized per detail on
the mitigation plan and filled with pit soils approved by the Owner's biologist If native
soils arc determined to be unacceptable by the Owner's biologist, pit soils will be
amended with Cedar Grove mulch or equivalent
43ANo fertilizers will be used within the wetland, In buffer areas only, install
"Agriform", or equal plant fertilizer to all planting pits as specified by manufacturer.
Fertilizers are allowed only below grade in the planting pits in the buffer areas. No
sewage sludge fertilizer ("SteerCo" or "Growco") is allowed in the mitigation area,
4.3 ,5 All containerized plant materials will be removed from their containers care folly to
prevent damage to the plant and its roots, Plants removed from their containers will be
planted immediately,
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4.3.6All plant materials will be placed as shown on the approved mitigation plan. If the
final installation varies from the approved mitigation plan, the contractor will provide an
electronic as-built of the installed conditions. All plant material will be flagged by the
contractor.
4.4 Planting Schedule and Warranty
4.4. l A fall-winter installation schedule (October I st -March 15th ) is preferred for lower
mortality rates of new plantings. If plant installation occurs during the spring or summer
(March 15 1h -Oct. ! 't ) a temporary irrigation system will be required, unless the area can
be sufficiently hand-watered.
4.4.2 All disturbed areas will be mulched or seeded with native mixes as specified on the
plans, as soon as the mitigation area grading is complete. The seed must be germinated
and a grass cover established by October I". If the cover is not adequately established by
October I st, exposed soils will be covered with approved erosion control material and the
contractor will notify the Owner in writing of alternative soil stabilization method used.
4.4.3 The installer will warrant all plant materials to remain healthy and alive for a period
of one year after final acceptance. The installer will replace all dead or unhealthy plant
materials per the approved plans and specifications.
4.5 Site Conditions
4.5. 1 The installer will coordinate with the Owner and the Owner's biologist for
construction scheduling.
4.5.2Landscape installation will begin after the City acceptance of grading and
construction. The Owner will notify the Owner's biologist of acceptance of final
grading.
4.5.3 Silt fences will be installed as shown on the approved mitigation grading plans. The
installer is responsible for repair and replacement of silt fences disturbed during plant
installation. No equipment or soils will be stored inside the silt fences.
4.5.4After clearing and grading is complete in the mitigation area, exposed soils will be
seeded or mulched. Orange construction fence will be placed around the mitigation area
to prohibit equipment and personnel in the mitigation area.
4.5.5Final grading will be based upon soil conditions found during excavation of the
mitigation area.
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4.5.6AII plant material will be planted with suitable soils per planting details. Soils from
planting holes will be spread and smoothed across the mitigation area.
5.0 MAINTENANCE PROGRAM
This maintenance program outlines the program, procedures and goals for mitigation of
the stream and buffer impacts at the mitigation site. This maintenance program will be
the responsibility of the project owner through the duration of its ownership of the
mitigation area, or throughout the duration of the monitoring period, whichever is longer.
The maintenance contractor will complete the work as outlined below.
5.1 Maintenance Work Scope
5. I. I To accomplish the mitigation goals, normal landscaping methods must be modified
to include:
a. No mowing or trimming of ground cover or vegetation in the mitigation area.
b. No placement of fertilizers in the mitigation area.
c. No placement of bark mulch or equivalent in the mitigation area, except as
noted in the planting details.
d. No placement of grass clippings, landscape debris, fill or ornamental plant
materials in the mitigation area.
5. l.2 Work to be included in each site visit:
a. Remove all litter including paper, plastic, bottles, construction debris, yard
debris, etc.
b. Remove all blackberry varieties and scotch broom within the mitigation area.
All debris is to be removed from site and disposed in an approved landfill.
c. Repair silt and/or permanent fencing and signage as needed.
5 .1.3 Work to be completed on an annual basis includes:
a. Areas containing Himalayan blackberry should be controlled by hand cutting
the blackberry and treating the remaining cut stems only with a glyphosphate
herbicide such as Roundup or Rodeo (applied by hand, not sprayed).
b. Replace dead or failed plant materials. Replacement plantings are to be of same
species, size and location as original plantings. Plantings are to be installed
during the dormant period.
c. Remove tree staking and guy wires from all trees after one year.
5.2 Maintenance Schedule
The Owner will conduct all items listed in the Maintenance Work Scope on an annual
basis. Additional work may be required per the Monitoring Report and as approved by
the City Biologist. Additional work may include removal of the grasses around each
shrub and tree, installation of wood chips at each shrub and tree base, reseeding the
mitigation area, re-staking existing trees and erosion control protection.
5.3 Watering Requirements
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5.3.1 If plantings are installed within the dormant period throughout the winter months
(October through March 15th ), watering is not required. However, watering will be
encouraged if plants mortality rises due to dry conditions.
5.3.2Ifplantings are installed during the summer months (March through October I st), a
temporary irrigation system will be required, unless the area can be sufficiently hand-
watered. The temporary irrigation system may be removed after the first year providing
the plantings are established and acclimated to on-site conditions.
5.4 Close-out of Five-Year Monitoring Program
Upon completion of the monitoring program and acceptance of the wetland mitigation by
the City, the maintenance of the project will be reduced to include removal of litter and
debris, repair of perimeter fencing and sign age, removal of noxious weeds and
undesirable vegetation, and repair of vandalized areas.
6.0 WETLAND AND BUFFER MONITORING PROGRAM
6.1 Sampling Methodology
The created wetlands and their associated buffers will be monitored 4 times the first year,
and once per year for years 2-5, as required by the City. Monitoring will be conducted
using the techniques and procedures described below to quantify the survival and relative
health and growth of plant material. A monitoring report submitted following each
monitoring visit will describe and quantify the status of the mitigation at that time. The
monitoring schedule will be determined after the plant installation has been completed.
Typically, the first monitoring visit occurs 3 months after the installation sign-off.
6. l.2 Vegetation
The vegetation monitoring consists of two tasks. The first is the inspection of the planted
material to determine the health and vigor of the installation. All the planted material in
the stream and buffer will be inspected during each monitoring visit to determine the
level of survival of the installation.
6.1.3 Hydrology
Monitoring of hydrology within the created wetlands will be conducted to confirm that
wetland hydrology has been created. Two sampling points will be established within the
created wetlands. At these points monitoring wells will be installed to determine the
level of surface or groundwater in these areas.
Pleasant Path/#A6-209
Sewall Wetland Consulting. Inc.
6.2 Standards of Success
October 9, 2012
Page 15
6.2.1. Evaluation of the success of the mitigation project will be based upon a
100% plant survival for all planted vegetation at the end of Year 1; 90% at the end
of Year 2; 85% at the end of Year 3; and 80% at the end of Year 5.
6.2.2. Up to 20% of any stratum can be composed of desirable native volunteers
when measuring cover.
6.2.3. No more than 10% cover of non-native or other invasive, e.g., Himalayan
blackberry, Japanese knotweed, evergreen blackberry, reed canary grass, Scots
broom, English ivy, morning glory, etc. Is permissible in any monitoring year.
Bond-holders are encouraged to maintain mitigation sites within these standards
through the monitoring period, to avoid corrective measures.
6.2.4 Wetland hydrology will be considered to be successfully attained when
inundation or saturation within 12" of the surface is present for 2 continuous
weeks or more in the growing season (March 15-0ctlS) in the 818sfofwetland
creation.
7.0 CONTINGENCY PLAN
7.1 A contingency plan can be implemented if necessary. Contingency plans can include
regrading, additional plant installation, erosion control, modifications to hydrology, and
plant substitutions including type, size, and location.
7.2 Careful attention to maintenance is essential in ensuring that problems do not arise.
Should any of the site fail to meet the success criteria, a contingency plan will be
developed and implemented with the County approval. Such plans are prepared on a
case-by-case basis to reflect the failed mitigation characteristics.
7 .3 Contingency/maintenance activities will include, but are not limited to:
-Replacing all plants lost to vandalism, drought, or disease, as necessary.
-Replacing any plant species with a 20 percent or greater mortality rate with the same
species or similar species approved by the City Biologist.
-Irrigating the stream area only as necessary during dry weather if plants appear to be too
dry, with a minimal quantity of water.
-Reseeding stream and buffer areas with an approved grass mixture as necessary if
erosion/sedimentation occurs.
-Removing all trash or undesirable debris from the wetland and buffer areas as necessary.
Preliminary
Technical Information Report
Project Manager:
Prepared by:
Date:
Revised:
Core No.:
FOR
Weston Heights
CITY OF RENTON
KING COUNTY, WASHINGTON
Lafe Hermansen
Sheri Murata, P.E.
July 2014
August 28, 2014
14040
!4111 Nf1?111l'lace.Suite 101
BtJll~vu~. Wu\l1inytun \1800!
Ph>\?.':, IIB5 7Rl7
www coredesigninc com
Weston Heights
Table of Contents
I PROJECT OVERVIEW ............................................................................................................... 1
Figure 1-1: Vicinity Map ........................................................................................................ 2
2 CONDITIONS AND REQUIREMENTS SUMMARY ................................................................ 3
2.1 Core Requirements ................................................................................................................ 3
2.1. l Core Requirement # I: Discharge at the Natural Location ............................................ 3
2.1.2 Core Requirement #2: Offsite Analysis ......................................................................... 3
2.1.3 Core Requirement #3: Flow Control ............................................................................. 3
2.1.4 Core Requirement #4: Conveyance System .................................................................. 3
2.1.5 Core Requirements #5: Erosion and Sediment Control ................................................. 3
2.1.6 Core Requirement #6: Maintenance and Operations ..................................................... 3
2.1.7 Core Requirement #7: Financial Guarantees and Liability ............................................ 3
2.1.8 Core Requirement #8: Water Quality ............................................................................ 3
2.2 Special Requirement #1: Other Adopted Area-Specific Requirements ................................ 4
2.2.1 Critical Drainage Areas ................................................................................................. 4
2.2.2 Master Drainage Plan···············································«··················································· 4
2.2.3 Basin Plans ..................................................................................................................... 4
2.2.4 Salmon Conservation Plans (SCPs) ............................................................................... 4
2.2.5 Stormwater Compliance Plans (SWCPs) ....................................................................... 4
2.2.6 Lake Management Plans (LMPs) .................................................................................. 4
2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) ........................................................... 4
2.2.8 Shared Facility Drainage Plans (SFDPs) ....................................................................... 4
2.3 Special Requirement #2: Floodplain/ Floodway Delineation .............................................. 4
2.4 Special Requirement #3: Flood Protection Facilities ............................................................ 4
2.5 Special Requirement #4: Source Controls ............................................................................ 4
2.6 Special Requirement #5: Oil Control .................................................................................... 4
3 OFFSITE ANALYSIS .................................................................................................................. 5
3.1 Study Area Definition and Maps ........................................................................................... 5
3.2 Resource Review ................................................................................................................... 5
Basin Reconnaissance Summary Reports ............................................................................... 5
FEMA Maps ........................................................................................................................... 5
Sensitive Areas Folio .............................................................................................................. 5
City of Renton Soil Survey ..................................................................................................... 5
Downstream Drainage Complaints ......................................................................................... 5
Core Design, Inc. WESTON HEIGHTS
3.3 Field Investigation ................................................................................................................. 5
Upstream Tributary Area ........................................................................................................ 5
Level 1 Downstream Analysis ................................................................................................ 6
Field Investigation .............................................................................................................. 6
3.4 Mitigation of Existing and Potential Problems ................................................................... 10
Downstream Drainage Problems Requiring Special Attention ............................................ 10
Department of Ecology 303d Listings .................................................................................. 10
Drainage Adjustments .......................................................................................................... 10
4 FLOW CONTROL AND WATER QUALITY DESIGN .................................. , ........................ 11
4.1 Existing Site Hydrology ...................................................................................................... 1 I
4.2 Developed Site Hydrology .................................................................................................. 12
Figure 4-1: Existing Conditions Basin Exhibit.. .................................................................. 14
Figure 4-2: Developed Conditions Exhibit.. ........................................................................ 15
4.3 Performance Standards ........................................................................................................ 16
Flow Control: Duration Standard Matching Forested Site Conditions ................................ 16
Conveyance Capacity ........................................................................................................... 16
Water Quality: Basic Water Quality Menu .......................................................................... 16
4.4 Flow Control System ............................................................... : ......................................... 16
Calculation of Lot Impervious Area ..................................................................................... 16
Flow Control BMPs/Individual Lot BMPs ........................................................................... 17
Detention Modeling .............................................................................................................. 18
4.5 Water Quality Calculations ................................................................................................. 22
Basic Wetvault ...................................................................................................................... 22
Basic Wetpond ...................................................................................................................... 23
5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN ........................................................... 25
6 SPECIAL REPORTS AND STUDIES ....................................................................................... 27
7 OTHER PERMITS ...................................................................................................................... 29
8 ESC ANALYSIS AND DESIGN ................................................................................................ 31
9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF
COVENANT .................................................................................................................................. 33
9.1 Bond Quantities ................................................................................................................... 33
9.2 Facility Summaries ............................................................................................................. 33
9.3 Declaration of Covenant ..................................................................................................... 33
10 OPERATIONS AND MAINTENANCE .................................................................................. 35
Core Design, Inc. WESTON HEIGHTS ii
Appendix A -Parcel & Basin Information
King County Parcel Report ( 1123059092)
King County Parcel Report ( 1123059010)
Appendix B -Resource Review & Off-site Analysis Documentation
FEMA Map (53033C0977F)
City of Renton Aquifer Protection Zones
City of Renton Groundwater Protection Areas
City of Renton Sensitive Area Maps
City of Renton Soil Survey
Drainage Complaints Exhibit
Downstream Drainage Map
Appendix C -Pond Sizing
City of Renton Flow Control Map
Rainfall Region & Regional Scale Factor (Figure 3.2.2.A)
KCRTS Hydrologic Soils Group Table (Table 3.2.2.B)
Mean Annual Storm Precipitation (Figure 6.4.1.A)
Vault KCRTS Input
Vault Results
Vault Peaks Analysis
Vault Durations Analysis
Pond KCRTS Input
Pond Results
Pond Peaks Analysis
Pond Durations Analysis
Appendix D -Conveyance Calculations
To be provided at Final Engineering
Core Design, Inc. WESTON HEIGHTS iii
Core Design, Inc. WESTON HEIGHTS iv
1 PROJECT OVERVIEW
The project site is located at Nile Avenue NE and NE 6th Pl in the City of Renton, King County.
Specifically the project is in the southwest quarter of Section 11, Township 23 North, Range 5
East, W.M. The site is bordered by single-family residential homes to the east, south and north
and Nile Avenue to the west. The King County tax parcel ID numbers for the two parcels
involved in the project are shown in Table l below (refer to the King County Parcel Reports
included in Appendix A).
Table 1: Parcel Information
KC Parcel# Parcel Area (SF)
1123059092 26,796
1123059010 171,190
Total 197,986 (4.55 ac)
The total parcel area is 4.55 acres, however the project site is approximately 3.3 acres. The west
quarter of the site has three structures with the surrounding area covered in lawn. It drains west
to Nile Avenue NE at approximately 8 percent to a ditch flowing south at a 2 percent. Drainage
remains on the east side of Nile Avenue NE in a series of ditches and culverts until NE 4th Place
where it is piped until the outlet to Maplewood Creek. The remaining area made up of forest and
drains to a wetland in the center of the site. When the wetland overflows it drains south and west
connecting to the storm drain system in Nile Avenue. The site does not receive any upstream
flow.
Proposed development of the property will include demolishing all existing structures and
constructing 12 new single-family residences with associated roadway, utilities, open space and
storm water management facilities on the site. Half-street frontage improvements on Nile
Avenue NE will be completed to provide 22 feet of pavement from the right of way centerline,
curb and gutter an 8-foot planter and a 5-foot sidewalk. See Figure 1-1: Vicinity Map, provided
below.
The project will be designed using the guidelines and requirements established in the 2009 King
County Surface Water Design Manual (2009 KCSWDM) and City of Renton Amendments to the
King County Surface Water Manual (COR Amendments) The project is required to apply a Flow
Duration Standard to Forested Conditions and Basic Water Quality.
The drainage analysis for detention sizing was modeled using the King County Runoff Time
Series (KCRTS) software. The water quality facility sizing calculations are based on methods
described in Chapter 6 of the 2009 KCSWDM. The conveyance calculations will be completed
using the Rational Method and the King County Backwater program.
There are two storm water facilities on site. A combined detention and water quality treatment
vault will be located at the southwest portion of the site next to Nile Avenue NE. The treated and
detained flows will be discharged towards Nile Avenue NE into the existing drainage ditch where
it will flow south. A combined detention and water quality treatment pond will located at the
southeast portion of the site at the end of the private road connecting to NE 7th Place. The treated
and detained flows will be discharged west to the existing wetland in Tract B.
Core Design, Inc. WESTON HEIGHTS Page 1
Core Design, Inc. WESTON HEIGHTS Page 2
2 CONDITIONS AND REQUIREMENTS SUMMARY
The proposed project is classified as requiring ·'Full Drainage Review" per the COR
Amendments. Therefore, all eight core requirements and five special requirements will be
addressed per Section 1.1 of the 2009 KCSWDM).
2.1 Core Requirements
2.1.1 Core Requirement #1: Discharge at the Natural Location
The combined detention and water quality vault will discharge at the natural discharge location to
the ditch on the east side of Nile Avenue NE. The combined detention and water quality vault
will discharge at the natural discharge location to the existing wetland located in Tract B.
2.1.2 Core Requirement #2: Offsite Analysis
This core requirement is addressed in Section 3 of this report.
2.1.3 Core Requirement #3: Flow Control
The detention vault and pond has been designed to meet the flow control duration standard
matching the forested site conditions per page 1-35 of the COR Amendments. This requires that
the developed condition discharge durations match the existing condition durations from 50% of
the 2-year to the 50-year storm events and that the developed 2-year and I 0-year peak discharge
rates do not exceed the existing 2-year and 10-year peak discharge rates, respectively.
2.1.4 Core Requirement #4: Conveyance System
A backwater analysis using King County Backwater (KCBW) will be performed during final
engineering and will show that the proposed conveyance system provides sufficient capacity for
the 25-year storm as calculated by the Rational Method.
2.1.5 Core Requirements #5: Erosion and Sediment Control
Erosion and sediment control will be provided through catch basin protection, silt fencing and
mulching. The permanent detention/water quality vault and pond will also be utilized as a
temporary sediment pond during construction.
2.1.6 Core Requirement #6: Maintenance and Operations
The vault and pond will be City owned and maintained.
2.1.7 Core Requirement #7: Financial Guarantees and Liability
A bond quantities worksheet will be provided in Section 9 of this Report during Final
Engineering.
2.1.8 Core Requirement #8: Water Quality
Basic water quality treatment will be provided by dead storage in the vault and pond.
Core Design, Inc. WESTON HEIGHTS Page 3
2.2 Special Requirement #1: Other Adopted Area-Specific
Requirements
2.2.1 Critical Drainage Areas
This project is not in an aquifer protection zone or groundwater protection area.
2.2.2 Master Drainage Plan
Not applicable.
2.2.3 Basin Plans
Not applicable.
2.2.4 Salmon Conservation Plans (SCPs)
Not applicable.
2.2.5 Stormwater Compliance Plans (SWCPs)
Not applicable.
2.2.6 Lake Management Plans (LMPs)
Not applicable.
2.2.7 Flood Hazard Reduction Plan Updates (FHRPs)
This project is not within a floodplain (see FEMA map included in Appendix B) and is not within
an area with an applicable Flood Hazard Reduction Plan. Therefore, additional requirements from
a Flood Hazard Reduction Plan do not apply.
2.2.8 Shared Facility Drainage Plans (SFDPs)
Not applicable.
2.3 Special Requirement #2: Floodplain/ Floodway Delineation
This project is not located within the 100-year floodplain (see FEMA Map included in Appendix
B).
2.4 Special Requirement #3: Flood Protection Facilities
As this project is not located within a 100-year floodplain there are no levees, revetments or
berms within the project.
2.5 Special Requirement #4: Source Controls
These requirements are not applicable as the project is not a commercial, industrial or multi-
family development.
2.6 Special Requirement #5: Oil Control
This requirement does not apply because the project is not a commercial or industrial
development nor is it expected to have more than 15,000 vehicles per day.
Core Design, Inc. WESTON HEIGHTS Page 4
3 OFFSITE ANALYSIS
3.1 Study Area Definition and Maps
The proposed project contains parcel numbers 1123059092 and 11230590 IO totaling 4.55 acres. A map
of the downstream can be found in Appendix B Downstream Drainage Map.
3.2 Resource Review
Basin Reconnaissance Summary Reports
No Basin Reconnaissance Summary Reports are available for the area that is within one mile of this
project site.
FEMA Maps
A FEMA map dated May 16, 1995 number 53033C0982 F was reviewed. The site is not located within a
floodplain as it is covered by "Zone X -Outside of 500-year floodplain. The FEMA Map is included in
Appendix B.
Sensitive Areas Folio
The City of Renton Sensitive Area Maps are included in Appendix B. Below is a summary of the project
site regarding Coal Mine Hazards, Erosion Hazards, Steep Slopes and Landslides:
• Coal Mine Hazard -the site is not near a coal mine hazard.
• Erosion Hazard -Low
• Steep Slopes -The majority of the site has 2% slopes with the steepest slope under 15%.
• Landslide Hazard -Low
City of Renton Soil Survey
The City of Renton Soil Survey Reference 11-C shows the site as having AgC or Alderwood (Till) soils.
The Soils Map exhibit is included in Appendix B.
Downstream Drainage Complaints
Drainage complaints were researched within the study area. King County lists four complaints which
have all been closed, therefore there are no current documented downstream problems associated with
this project site. See the Drainage Complaint Exhibit Appendix B.
3.3 Field Investigation
Upstream Tributary Area
There is no upstream tributary area for this project.
Core Design, Inc. WESTON HEIGHTS Page 5
Level 1 Downstream Analysis
Field Investigation
A field investigation was completed on May 21, 2014. The temperature was approximately 60 degrees
and sunny.
The existing site has two residences with gravel driveways and a detached garage. The western quarter of
the site is covered in lawn (surrounding the residences and garage) and the remaining site is forested with
a wetland in the center of the site. The wetland drains south and overflows into a 12-inch storm drain in
the Edenwood Plat which continues south to NE 61h Street. From NE 6'h Street, the 12-inch storm drain
flows west where it has a confluence with the drainage system on the east side of Nile Avenue NE.
Overland flow from the west portion of the site drains west to Nile Avenue NE and drains south in series
of grass or rock lined ditches and culverts on the east side of the street. The open channels range from a
depth of 1 foot and a width of 4 feet with rock lining on the north end of the site (Picture 1) to a vegetated
channel with a depth of2 feet and width of3 feet just below the project's south property line. The ditch
and culvert section continues south on the east side of Nile Avenue NE until approximately 300 feet north
of NE 4th Pl, where it drains into an 18-inch storm drain and flows south. This is the quarter mile point
downstream of the site.
The City of Renton provides current storm water information online, using a GIS based system called
COR Maps. COR Maps provides information on the type of pipes, manholes and catch basins in the city.
Following the pipe flow direction from COR Maps, the 18-inch diameter concrete pipe crosses over to the
west side of Nile Avenue just before it intersects with NE 4th street. The pipe then heads west down NE
4th street and crosses to the south side just before Jericho Avenue. The storm water pipe parallels Jericho
Avenue running through private property until NE 2"d street. Picture 10 shows the manhole as the pipe
crosses from the east side of Jericho Avenue and heads south down the center line of the road. Flow
continues south until NE I" street, where the 36-inch pipe heads west and discharges into Maplewood
Creek.
Core Design, Inc. WESTON HEIGHTS Page6
I -Looking south in drainage ditch along the
east side of Nile Avenue next to the site
3 -Looking south on the cast side of Nile
Avenue just downstream of site
2 -Looking south along the east side of 1'/ile
Avenue into first culvert
4 -Looking south along the cast side of Mic
Avenue just before 'iE 6'" Street
Core Design, Inc. WESTON HEIGHTS Page 7
' .....
5 -Looking at a concrete pipe junction with
water flowing left to right (south) down Nile
Avenue
7 -Looking south on the east side of Nile
Avenue before NE 4'" Street
6 -Looking south on the east side of '1/ilc
Avenue at the last drainage ditch before pipe
flow
8 -Looking South at the intersection of 4'"
and Nile Avenue where pipe flow crosses Nile
Avenue from left to right (east to west)
Core Design, Inc. WESTON HEIGHTS Page 8
9 -Existing man hole looking west on NE 4'"
street
~-.::~~-.. ;. ~.,. ·1:~t~f
";.,.: to, . ''{ ' : :·
'7!. ' : .. ,..,-~_:.,.,,:~,
. . •'~~ . /":>.,, ;;, ~· " ,• ~:·~~ ~: .;~,~~
" . ''.•~;:_.,,,. I .-: .. ! ~.;·v .. ..: ···~x:· >. :-• ~' ... ~--'".'I·, .... -, ,· ---. ·< .. "'"~-.. ~\ , ~
! __ (___ . ··~"~:~,\.:~ ~ ... '. :, . -.~
11 -Storm water outlet into Vlaplewood stream
next to Jericho Street
10 -Existing Man hole looking South down
Jericho Avenue
12 -Looking at the downstream flow from
Maplewood just after outlet Looking south on
Core Design, Inc. WESTON HEIGHTS Page 9
3.4 Mitigation of Existing and Potential Problems
Downstream Drainage Problems Requiring Special Attention
Type 1 -Conveyance System Nuisance Problems
There are no known, reported or observed current downstream conveyance nuisance
problems.
Type 2 -Severe Erosion Problems
There are no known, reported or observed current downstream severe erosion problems
Type 3-Severe Flooding Problems
There are no known, reported or observed current downstream severe flooding problems.
Department of Ecology 303d Listings
Type I -Bacteria Problems
There are no known or reported bacteria problems.
Type 2 -Dissolved Oxygen (DO) Problems
There are no known or reported dissolved oxygen problems.
Type 3 -Temperature Problems
There are no known or reported temperature problems.
Type 4 -Metals Problems
There are no known or reported downstream metals problems.
Type 5 -Phosphorous Problems
There are no known or reported downstream phosphorous problems.
Type 6 -Turbidity Problems
There arc no known or reported downstream turbidity problems.
Type 7 -High pH Problems
There are no known or reported high pH problems.
Drainage Adjustments
There is no drainage adjustment proposed for this project.
Core Design, Inc. WESTON HEIGHTS Page 10
4 FLOW CONTROL AND WATER QUALITY DESIGN
4.1 Existing Site Hydrology
The west quarter of the site has three structures with the surrounding area covered in lawn. It drains west
to Nile Avenue NE at approximately 8 percent to a ditch flowing south at a 2 percent. Drainage remains
on the east side of Nile Avenue NE in a series of ditches and culverts until NE 4th Place where it is piped
until the outlet to Maplewood stream. The remaining area made up of forest and drains to a wetland in
the center of the site. When the wetland overflows in will drain south and west connecting to the storm
drain system in Nile Avenue. See Table 4-1 below and Figure 4-1: Existing Conditions. A site Soils Map
is included in Appendix Band the KCRTS Hydrologic Soils Group table (Table 3.2.2.B) is included in
Appendix C.
Historic site conditions are assumed for the existing onsite area of 3.02 acres per Section 1.2.3.1 of the
2009 KCSWDM (page 1-43) and are modeled as Till Forest.
Table 4-1 Existinq Conditions Areas
GROUND COVER AREA ( acres l
Till-Forest (Draining to Nile Ave NE) 1.76
Till-Forest (Draining to Ex Wetland) 1.36
TOTAL 3.12
The peak flow rates for the pre-developed conditions as determined by KCRTS (one hour time steps) are
shown below. A regional scale factor of ST 1.0 was used as determined by Figure 3.2.2.A in
Appendix C.
Draining to Nile Avenue NE (Vault)
Flow Frequency Analysis
Time Series File:14040_pre.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0 .111 2 2/09/01 18:00
0.030 7 1/06/02 3:00
0.082 4 2/28/03 3:00
0.003 8 3/24/04 20:00
0. 049 6 1/05/05 8:00
0.085 3 1/18/06 21:00
0.072 5 11/24/06 4:00
0.142 1 1/09/08 9:00
Computed Peaks
-----Flow Frequency Analysis-------
--Peaks Rank Return Prob
(CFS) Period
0.142 1 100.00 0.990
0 .111 2 25. 00 0. 960
0.085 3 10.00 0.900
0.082 4 5.00 0.800
0. 072 5 3.00 0.667
0.049 6 2.00 0.500
0.030 7 1. 30 0.231
0.003 8 1.10 0. 091
0 .132 50.00 0.980
Core Design, Inc. WESTON HEIGHTS Page 11
Drainin!! to the Existin!! Wetland (Pond)
Flow Frequency Analysis
Time Series File:14040_pre.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0.083 2 2/09/01 18:00
0.022 7 1/06/02 3:00
0.061 4 2/28/03 3:00
0.002 8 3/24/04 22:00
0.036 6 1/05/05 8:00
0.064 3 1/18/06 21:00
0.054 5 11/24/06 4:00
0.106 1 1/09/08 9:00
Computed Peaks
4.2 Developed Site Hydrology
-----Flow Frequency Analysis-------
-Peaks Rank Return Prob
(CFS) Period
0.106 1 100.00 0.990
0.083 2 25. 00 0.960
0.064 3 10.00 0.900
0.061 4 5.00 0.800
0.054 5 3.00 0.667
0.036 6 2.00 0.500
0.022 7 1. 30 0.231
0.002 8 1.10 0.091
0.098 50.00 0.980
Proposed development of the property will include demolishing all existing structures and constructing 12
new single-family residences with associated roadway, utilities, open space and stormwater management
facilities on the site. Half-street frontage improvements on Nile Avenue NE will be completed to provide
22 feet of pavement from the right of way centerline, curb and gutter an 8-foot planter and a 5-foot
sidewalk. Lots 1-9 will drain to the detention/water quality vault in Tract C and discharge west to an
existing ditch on the east side of Nile Avenue NE. Lots 10-12 will drain south to a detention/water
quality pond in Tract A and discharge to the existing wetland in Tract B. There is a small portion of area
at the intersection of Road B and NE 7'' Street that is unable to drain to the pond due to topographic
constraints which will be modeled as bypass area. The developed condition areas are summarized in
Table 4-2 and Figure 4-2 Developed Conditions Map.
Table 4-2 Developed Condition Areas
GROUND COVER AREA /acres)
Till-Grass 0.65
Effective Impervious 1.11
TOTAL (To Vault) 1.76
Till-Grass 0.88
Effective Impervious 0.43
TOTAL (To Pond) 1.31
Till-Grass 0.01
Effective Impervious 0.04
TOTAL Bypass 0.05
Till-Grass 1.54
Effective Impervious 1.57
TOT AL (Site) 3.12
The undetained peak flow rates for the developed conditions as determined by KCRTS (one hour time
steps) are shown below.
Core Design, Inc. WESTON HEIGHTS Page 12
Draining to Nile Avenue NE (Vault)
Flow Frequency Analysis
Time Series File:14040 dev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0.327 6 2/09/01 2:00
0.267 8 1/05/02 16:00
0.393 3 2/27 /03 7:00
0.289 7 8/26/04 2:00
0.348 4 10/28/04 16:00
0.347 5 1/18/06 16:00
0.420 2 10/26/06 0:00
0.662 1 1/09/08 6:00
Computed Peaks
Draining to the Existing Wetland (Pond)
Flow Frequency Analysis
Time Series File:14040 dev.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0.183 4 2/09/01 2:00
0 .132 7 1/05/02 16:00
0.224 2 2/27/03 7: 00
0.124 8 8/26/04 2:00
0.154 6 10/28/04 16:00
0 .192 3 1/18/06 16:00
0.179 5 11/24/06 3:00
0.389 1 1/09/08 6:00
Computed Peaks
Pond Bvoass
Flow Frequency Analysis
Time Series File:14040_bypass.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0. 011 6 2/09/01 2:00
0.009 8 1/05/02 16:00
0.012 3 12/08/02 18:00
0.010 7 8/26/04 2:00
0.012 4 10/28/04 16:00
0.012 5 1/18/06 16:00
0.015 2 10/26/06 0:00
0.021 1 1/09/08 6:00
Computed Peaks
-----Flow Frequency Analysis-------
--Peaks Rank Return Prob
(CFS) Period
0.662 1 100.00 0.990
0.420 2 25.00 0. 960
0. 393 3 10.00 0.900
0.348 4 5.00 0.800
0. 347 5 3.00 0.667
0. 327 6 2. 00 0.500
0.289 7 1. 30 0.231
0.267 8 1.10 0.091
0.581 50.00 0.980
-----Flow Frequency Analysis-------
--Peaks Rank Return Prob
(CFS) Period
0.389 1 100.00 0.990
0.224 2 25.00 0. 960
0.192 3 10.00 0.900
0.183 4 5.00 0.800
0.179 5 3.00 0.667
0.154 6 2.00 0.500
0.132 7 1. 30 0.231
0.124 8 1.10 0. 091
0.334 50.00 0.980
-----Flow Frequency Analysis-------
--Peaks Rank Return Prob
(CFS) Period
0.021 1 100.00 0.990
0.015 2 25. 00 0.960
0.012 3 10.00 0.900
0 .012 4 5. 00 0.800
0 .012 5 3.00 0.667
0 .011 6 2. 00 0.500
0.010 7 1. 30 0.231
0.009 8 1.10 0.091
0.019 50.00 0.980
Core Design, Inc. WESTON HEIGHTS Page 13
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4.3 Performance Standards
All stormwater facilities will be designed in accordance with the 2009 KCSWDM with the COR
Amendments, with Flow Control Duration Standard Matching Forested Site Conditions. The proposed
water quality treatment system will meet requirements from the Basic Water Quality Protection Menu.
Flow Control: Duration Standard Matching Forested Site Conditions
The Flow Control Duration Standard Matching Forested Site Conditions requires maintaining the
durations of developed flows at their pre-development levels for all flows greater than one-half of the 2-
year peak flow through the 50-year peak flow. The pre-development peak flow rates for the 2-year and
I 0-year runoff events must also be maintained under this requirement.
Conveyance Capacity
The proposed conveyance system will be designed with sufficient capacity to convey and contain the 25-
year peak flow as determined by the Rational Method. It will also be verified that the I 00-year peak flow
will not create or aggravate a severe flooding or erosion problem per Section 1.2.2.
Water Quality: Basic Water Quality Menu
The Basic Water Quality Menu includes one pollutant removal targets:
• Total Suspended Solids~ 80% reduction
The Basic Water Quality Menu, described in detail in Section 6.1.1 of the 2009 KCSWDM (page 6-4),
provides eight options to meet the pollutant removal targets listed above.
• Option I: Biofiltration Swale
• Ootion 2: Filter Strio
• Option 3: Wetpond
• Option 4: Wetvault
• Option 5: Stormwater Wetland
• Option 6: Combined Detention and Wetpool Facilities
• Option 7: Sand Filter
• Option 8: Stormfilter
The project proposes to apply Option 3 and 4, a wetpond and a wetvault. More detailed discussion and
preliminary sizing calculations of the flow control and water quality treatment facility proposed for this
project follows later in this section.
4.4 Flow Control System
Calculation of Lot Impervious Area
The impervious area per lot applied to the developed basin time series file was determined using the
criteria in the 2009 KCSWDM page 3-27 and page 3-2 of the COR Amendments. The proposed
development is urban residential and the west portion of the site is zoned R-8. The minimum impervious
area per lot per the 2009 KCSWDM (page 3-27) would either be 4,000 square feet or the maximum
impervious area as stated in Section 3.2.2.1 of the COR SWDMA, whichever is less. The maximum
impervious surface allowed in the R-8, zone in the City of Renton, is 75%. The east portion of the site is
zoned R-4 with a maximum impervious surface of 55%.
Core Design, Inc. WESTON HEIGHTS Page 16
Flow Control BMPs/lndividual Lot BMPs
This project will not be served by an infiltration facility and therefore must apply flow control BMPs to
supplement the flow mitigation provided by the detention vault and pond. This project has lots less than
22,000 square feet so it is subject to the small lot BMP requirements. Full dispersion and full infiltration
of the roof runoff is not feasible, so one or more of the following BMPs must be applied to an impervious
area equal to at least 10% of the lot for lots up to 11,000 square feet and 20% of the lot for lots between
11,000 and 22,000 square feet.
• Limited Infiltration
I • Basic Dispersion
• Rain Garden
• Permeable Pavement
• Rainwater Harvesting
• Vegetated Roof
• Reduced Impervious Surface Credit
• Native Growth Retention Credit
This project will be implementing basic dispersion or other menu items that may be feasible at the time of
acquiring building permits on impervious area equal to 10% of the lot area for lots 1-9 since they are less
than 11,000 square feet. Lots 10-12 will be implementing dispersion on impervious area equal to 20% of
the lot area since these lots are greater than 11,000 square feet. This area draining to the flow control
BMP on each lot will be modeled as 50% impervious and 50% grass. Table 4-3 below summarizes the
breakdown of the onsite areas.
Table 4-3 Onsite Areas
Total Area Land Use Area
Lot Effective Individual Lot (sf) Impervious (sf) lmoervious (sf) Till Grass (sf) BMP (sf)
1 5,279 3.959 3,695 1,584 528
2 4,618 3,464 3,233 1,385 462
3 5,321 3,991 3,725 1,596 532
4 5,614 4,000 3,719 1,895 561
5 4,908 3.681 3,436 1,472 491
6 5,710 4,000 3,715 1,996 571
7 5,911 4,000 3,704 2,207 591
8 5,978 4,000 3,701 2,277 598
9 5,527 4,000 3,724 1,803 553
Tract A 8,891 2,001 2,001 6,890
ROW 18,879 22,489 13.616 5,263
Total to 76,636 48,268 28,368 Vault (sO
Total to 1.76 1.11 0.65 Vault (ac)
10 14,009 4,000 2,599 11,410 2802
11 13,129 4,000 2,687 10,442 2626
12 12,414 4,000 2,759 9,655 2483
RoadB 5,107 4,337 4,337 770
Core Design, Inc. WESTON HEIGHTS Page 17
Tract C 12,383 6,247 6,247 6,136
Total to 57,042 18,629 38,413 Pond (sD
Total to 1.31 0.43 0.88 Pond (acl
Pond 2,022 1,657 1,657 365 B~nass /sD
Pond 0.05 0.04 0.01 .
Bvnass (ac)
TOTAL 135,700 68,554 67,146 Site (sD
TOTAL 3.12 1.57 1.54 Site /acl
Notes:
1. Impervious Area= 4,000 sf or 75% of the Total Area for Lots 1-9, 55% for Lots I 0-12 whichever is less
2. Effective Impervious Area= Impervious Arca -Individual Lot BMP
3. Pervious Grass Area= Total Area -Impervious Area
4. Individual Lot BMP Area= I 0% of Total Area for Lots l-9 and 20% for Lots 10-12 (This area would not drain to the
vault)
Therefore, there is a total of 1. 96 acres draining to the vault consisting of 1.31 acres of effective
impervious area and 0.65 acres of till-grass. There is 1.31 acres draining to the pond consisting of0.43
acres of effective impervious area and 0.88 acres of till-grass. There is 0.05 ac of area that will bypass the
pond consisting of 0.04 ac of effective impervious and 0.01 ac of Till-Grass. The total developed area for
the project is 3.32 acres consisting of 1.78 acres of impervious and 1.54 acres of till-grass.
Detention Modeling
The proposed detention vault (82 'x62') will be located at the south west comer of the site adjacent to Nile
Avenue NE with 4. 7 feet of live storage.
KCRTS Vault Calculation
Type of Facility: Detention Vault
80.00 ft
62.00 ft
Facility Length:
Facility Width:
Facility Area:
Effective Storage Depth:
Stage O Elevation:
Storage Volume:
Riser Head:
Riser Diameter:
Number of orifices:
Orifice #
1
2
Height
(ft)
0.00
3.05
4960.
4.70
509.00
23312.
4.70
12.00
2
Diameter
(in)
0.68
1.44
Top Notch Weir: None
Outflow Rating Curve: None
sq. ft
ft
ft
cu. ft
ft
inches
Full Head
Discharge
(CFS)
0.027
0.072
Core Design, Inc. WESTON HEIGHTS
Pipe
Diameter
(in)
4.0
Page 18
The proposed detention vault includes a two orifice control structure. The first orifice is 11/16 inches in
diameter and is at the bottom of the riser. The second orifice is 3.05 feet above the live/dead interface
elevation and is I 7/16 inch in diameter. The proposed vault will have a maximum live storage depth of
4.78 feet (0.08 feet above the riser) with a maximum storage volume of23,713 cubic feet.
Target Cale Stage Elev (Cu-Ft) (Ac-Ft)
1 0.66 ******* 0.35 4.78 513.78 23713. 0.544
2 0.33 ******* 0.09 4.49 513.49 22249. 0 .511
3 0.39 0.10 0.08 4.12 513.12 20424. 0.469
4 0.33 ******* 0.08 3.95 512.95 19569. 0 .449
5 0.35 ******* 0.04 3.21 512. 21 15906. 0.365
6 0.21 0.06 0.02 2.97 511. 97 14729. 0.338
7 0.27 ******* 0.02 2.90 511. 90 14364. 0.330
8 0.29 ******* 0.02 1. 78 510.78 8847. 0.203
The outflow from the detention vault control structure releases 0.02 cfs for the 2-year event and 0.08 cfs
for the JO-year event. These release rates are below the pre-developed peak flows of 0.06 cfs and 0.10 cfs
for the 2-year and I 0-year rates, respectively. Therefore, the proposed facility meets the peak release rate
requirements.
The flow duration comparison analysis results for the provided detention vault are shown below. There is
less than I 0% excursion between the 2-year and 50-year release rate and the curve is entirely under the
target curve for the required range of 50% of the 2-year to the full 2-year pre-developed tlowrates.
Therefore, the proposed detention facility meets the flow duration requirement.
Core Design, Inc. WESTON HEIGHTS Page 19
Duration Comparison Anaylsis
Base File: 14040_pre. tsf
New File: rdout vault.tsf
Cutoff Units: Discharge in CFS
-----Fraction of Time--------------Check of Tolerance-------
Cutoff Base New %Change Probability Base
0.025 0.92E-02 0.57E-02 -37. 9 I 0.92E-02 0.025
0.031 0.62E-02 0.50E-02 -19.3 I 0.62E-02 0. 031
0.038 0.49E-02 0.45E-02 -7.0 I 0.49E-02 0.038
0. 045 0.37E-02 0.36E-02 -0.9 I 0.37E-02 0.045
0.051 0.28E-02 0.26E-02 -6.4 I 0.28E-02 0.051
0.058 0.22E-02 0.20E-02 -7.4 I 0.22E-02 0.058
0.065 0.15E-02 0.17E-02 13 .3 I 0.15E-02 0.065
0.071 0.99E-03 0 .12E-02 24.6 I 0.99E-03 0.071
0.078 0.60E-03 0.83E-03 37.8 I 0.60E-03 0.078
0.084 0.34E-03 0.44E-03 28.6 I 0.34E-03 0.084
0.091 0.21E-03 0.24E-03 15.4 I 0.21E-03 0.091
0.098 0.16E-03 0.82E-04 -50.0 I 0.16E-03 0.098
0.104 O.llE-03 O.OOE+OO -100.0 I O.llE-03 0.104
0 .111 0.16E-04 O.OOE+OO -100.0 I 0.16E-04 0 .111
Maximum positive excursion= 0.005 cfs ( 7.1%)
occurring at 0.076 cfs on the Base Data:14040_pre.tsf
and at 0.081 cfs on the New Data:rdout vault.ts£
Maximum negative excursion= 0.009 cfs (-29.4%)
occurring at 0.032 cfs on the Base Data:14040_pre.tsf
and at 0.022 cfs on the New Data:rdout vault.ts£
New %Change
0.021 -15.0
0.022 -28.9
0.033 -13. 9
0.044 -0.9
0.050 -2.3
0.056 -3.7
0.068 5.6
0.075 4.9
0.082 6.0
0.086 2.2
0. 092 1.4
0.094 -3.7
0.096 -7.7
0.099 -10.7
The proposed detention pond will be located at the south east comer of the site at the end of the private
road connecting to NE 7'" Place with 3.3 feet of live storage.
KCRTS Pond Calculation
Type of Facility: Detention Pond
Side Slope:
Pond Bottom Length:
Pond Bottom Width:
Pond Bottom Area:
Top Area at 1 ft. FB:
Effective Storage Depth:
Stage 0 Elevation:
Storage Volume:
Riser Head:
Riser
Number
Orifice#
1
2
of
Diameter:
orifices:
Height
(ft)
0.00
2.40
2.40 H:lV
80.00 ft
40.00 ft
3200. sq. ft
6103. sq. ft
0 .140 acres
3.30 ft
520.00 ft
13972. cu. ft
0.321 ac-ft
3.30
12.00
2
Diameter
(in)
0.56
1.38
ft
inches
Full Head
Discharge
(CFS)
0.016
0.049
Top Notch Weir: None
Outflow Rating Curve: None
Core Design, Inc. WESTON HEIGHTS
Pipe
Diameter
(in)
4.0
Page 20
The proposed detention pond includes a two orifice control structure. The first orifice is 9/16 inches in
diameter and is at the bottom of the riser. The second orifice is 2.4 feet above the live/dead interface
elevation and is 1 3/8 inch in diameter. The proposed vault will have a maximum live storage depth of
3.32 feet with a maximum storage volume of 14,061 cubic feet.
Hyd Inflow Outflow Peak Storage
Stage Elev (Cu-Ft) (Ac-Ft)
1 0.39 0.12 3.32 523.32 14061. 0.323
2 0.18 0.06 3.16 523.16 13245. 0. 304
3 0.22 0.05 3.00 523.00 12387. 0.284
4 0.18 0.04 2.69 522.69 10845. 0.249
5 0.19 0.03 2.49 522.49 9874. 0.227
6 0 .11 0.01 2.38 522.38 9357. 0 .215
7 0 .13 0.01 2.28 522.28 8899. 0.204
8 0.12 0.01 0.97 520.97 3382. 0.078
Hyd R/D Facility Tributary Reservoir POC Outflow
Outflow Inflow Inflow Target Cale
1 0.12 0.02 ******** ******* 0.12
2 0.06 0.01 ******** ******* 0.06
3 0.05 0.01 ******** 0.06 0.06
4 0.04 0.01 ******** ******* 0.04
5 0.03 0.01 ******** ******* 0.03
6 0.01 0.01 ******** 0.03 0.02
7 0.01 0.01 ******** ******* 0.02
8 0.01 0.01 ******** ******* 0.02
The outflow from the detention vault control structure releases 0.02 els for the 2-year event and 0.06 cfs
for the 10-year event. These release rates are below the pre-developed peak flows of0.03 cfs and 0.06 cfs
for the 2-year and 10-year rates, respectively. Therefore, the proposed facility meets the peak release rate
requirements.
The flow duration comparison analysis results for the provided detention vault are shown below. There is
less than I 0% excursion between the 2-year and 50-year release rate and the curve is entirely under the
target curve for the required range of 50% of the 2-year to the full 2-year pre-developed flowrates.
Therefore, the proposed detention facility meets the flow duration requirement.
Duration Comparison Anaylsis
Base File: 14040_pre.tsf
New File: dsout_pond.tsf
Cutoff Units: Discharge in CFS
-----Fraction of Time--------------Check of
Cutoff Base New %Change Probability Base
0.018 0.99E-02 0.77E-02 -22.4 I 0.99E-02 0.018
0.023 0.64E-02 0.56E-02 -12.8 I 0.64E-02 0.023
0.028 0.50E-02 0.46E-02 -8.8 I 0.50E-02 0.028
0.033 0.38E-02 0.35E-02 -7.8 I 0.38E-02 0.033
0.038 0.29E-02 0.27E-02 -6.7 I 0.29E-02 0.038
0.043 0.22E-02 0.17E-02 -24.3 I 0.22E-02 0.043
0.048 0.15E-02 0.14E-02 -10.6 I 0.15E-02 0. 048
0.053 0.lOE-02 O.lOE-02 -1. 6 I 0.lOE-02 0.053
Core Design, Inc. WESTON HEIGHTS
Tolerance-------
New %Change
0.016 -13.1
0.020 -13. 3
0.026 -6.7
0.032 -3.5
0.036 -5.3
0.041 -4.9
0.046 -4. 3
0.053 -0.1
Page 21
0.058 0.65E-03 0.64E-03 -2.5 0.65E-03 0.058
0.063 0.34E-03 0.36E-03 4.8 0.34E-03 0.063
0.068 0.23E-03 0.33E-04 -85.7 0.23E-03 0.068
0.072 0.16E-03 O.OOE+OO -100.0 0.16E-03 0.072
0.077 0. llE-03 O.OOE+OO -100.0 O.llE-03 0. 077
0.082 0.16E-04 O.OOE+OO -100.0 0.16E-04 0.082
Maximum positive excursion= 0.001 cfs ( 2.1%)
occurring at 0.059 cfs on the Base Data,14040_pre.tsf
and at 0.060 cfs on the New Data,dsout_pond.tsf
Maximum negative excursion= 0.014 cfs (-17.9%)
occurring at 0.080 cfs on the Base Data,14040_pre.tsf
and at 0.065 cfs on the New Data,dsout_pond.tsf
4.5 Water Quality Calculations
Basic Wetvault
0.057 -0.5
0.063 0.2
0.064 -5.4
0.065 -10.9
0.065 -16.2
0.068 -17.5
A Basic Wetvault includes a permanent wetpool that allows for the removal of 80% of Total Suspended
Solids. Section 6.4.1.1 outlines a 4-step process to calculate the required wetpool volume.
Step 1: Identify required wetpool volume factor /f)
A basic wetpond requires a volume factor of 3.0.
Step 2: Determine rainfall (R) for the mean annual storm
Figure 6.4.1.A (page 6-71 in the 2009 KCSWDM, included below and in Appendix C) is used to
determine the rainfall, in inches, for the mean annual storm. The rainfall is then converted into feet for use
in Equation 6-13 (shown below). The mean annual storm rainfall for this project site is 0.47" as noted on
Figure 6.4.1.A included in Appendix C.
Step 3: Calculate runoff from the mean annual storm (V,) for the developed site
The land cover types and associated areas for each in the developed project site are used to calculate the
amount of rainfall, in cubic feet, that runs off each land cover type. Coefficients specific to the four U.S.
Department of Agriculture soil survey cover categories are weighted by the drainage areas and then
multiplied by the rainfall, R, from Step 2.
Equation 6-13 V,. = (0.9A; + O.ZSA,9 + O.lOA,1 + O.OlA 0 )x(R)
where V, ~ calculated volume of runoff from mean annual storm
A,~ area of impervious surface (57,141 sf)
A,, ~ area of till soil covered with grass (28,368 sf)
A,r~ area of till soil covered with forest (0 st)
A,~ area of outwash soil covered with grass or forest (0 sf)
R ~ rainfall from mean annual storm (0.039 ft)
Using Equation 6-13 above and the land cover areas in the developed basin calculations, the volume of
runoff from the mean annual storm is 2,292 cubic feet.
Core Design, Inc. WESTON HEIGHTS Page 22
Step 4: Calculate wetpool volume /V bl
The numbers/ results from the previous steps are used in Equation 6-14 (shown below) to calculate the
required wetpool volume.
Equation 6-14 Vb = fVr
where Vb= calculated required minimum wetpool volume
f = volume factor from Step I (3.0)
V, = volume of runoff from mean annual storm (2,292 cf)
Using Equation 6-14 above and the results from the previous steps, the required minimum wetpool
volume, V. is 6,876cubic feet. The proposed wetpool yields a volume of 7,355 cubic feet.
Basic Wetpond
A Basic Wetpond includes a permanent wetpool that allows for the removal of 80% of Total Suspended
Solids. Section 6.4.1.1 outlines a 4-step process to calculate the required wetpool volume.
Step I: Identify required wetpool volume factor /f)
A basic wetpond requires a volume factor of 3.0.
Step 2: Determine rainfall /R) for the mean annual storm
figure 6.4.1.A (page 6-71 in the 2009 KCSWDM, included below and in Appendix C) is used to
determine the rainfall, in inches, for the mean annual storm. The rainfall is then converted into feet for use
in Equation 6-13 (shown below). The mean annual storm rainfall for this project site is 0.47'' as noted on
Figure 6.4.1.A included in Appendix C.
Step 3: Calculate runoff from the mean annual storm (Vrl for the developed site
The land cover types and associated areas for each in the developed project site are used to calculate the
amount of rainfall, in cubic feet, that runs off each land cover type. Coefficients specific to the four U.S.
Department of Agriculture soil survey cover categories are weighted by the drainage areas and then
multiplied by the rainfall, R, from Step 2.
Equation 6-13 V,. = (0.9A; + 0.25Atg + 0.lOAtf + 0.0lA0 )x(R)
where V, = calculated volume of runoff from mean annual storm
A,= area of impervious surface (18,629 sf)
A,,= area of till soil covered with grass (38,413 sf)
A,r = area of till soil covered with forest (0 sf)
A,= area of outwash soil covered with grass or forest (0 sf)
R = rainfall from mean annual storm (0.039 ft)
Using Equation 6-13 above and the land cover areas in the developed basin calculations, the volume of
runoff from the mean annual storm is 1,033 cubic feet.
Step 4: Calculate wetpool volume /Vbl
Core Design, Inc. WESTON HEIGHTS Page 23
The numbers I results from the previous steps are used in Equation 6-14 (shown below) to calculate the
required wetpool volume.
Equation 6-14
where
vb= fV,.
Vb~ calculated required minimum wetpool volume
f~ volume factor from Step I (3.0)
V, ~ volume of runoff from mean annual storm (1,033 cf)
Using Equation 6-14 above and the results from the previous steps, the required minimum wetpool
volume, V. is 3,098 cubic feet. The proposed wetpool yields a volume of 4,080 cubic feet.
Core Design, Inc. WESTON HEIGHTS Page 24
5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN
The onsite conveyance system will be analyzed using the King County Back Water (KCBW) program per
the requirements described in Chapter 4 of the 2009 KCSWDM during Final Engineering.
Core Design, Inc. WESTON HEIGHTS Page 25
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 26
6 SPECIAL REPORTS AND STUDIES
The geotechnical report for this project completed by Liu and Associates, Inc. dated November 10, 2008
and is provided under a separate cover.
Core Design, Inc. WESTON HEIGHTS Page 27
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 28
7 OTHER PERMITS
~ NPDES Permit
~ Building Permits
~ ROW Use Permit
~ Demolition Permit
~ Vault Permit
Core Design, Inc. WESTON HEIGHTS Page 29
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 30
8 ESC ANALYSIS AND DESIGN
This section will be completed during Final Engineering.
Core Design, Inc. WESTON HEIGHTS Page 31
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 32
9 BOND QUANTITIES, FACILITY SUMMARIES, AND
DECLARATION OF COVENANT
9.1 Bond Quantities
A Site Improvement Bond Quantity Worksheet will be included prior to approval of the final engineering
plans.
9.2 Facility Summaries
Not applicable.
9.3 Declaration of Covenant
Not applicable.
Core Design, Inc. WESTON HEIGHTS Page 33
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 34
10 OPERATIONS AND MAINTENANCE
The operations and maintenance information will be provided at Final Engineering.
Core Design, Inc. WESTON HEIGHTS Page 35
THIS PAGE INTENTIONALLY LEFT BLANK
Core Design, Inc. WESTON HEIGHTS Page 36
Appendix A
Parcel & Basin Information
~
King Count','
Aho.cars .:,t your Se/'VYCE'
KCGIS Parcel Reports
Districts and Development
Condit:ons Report
Find Your Council District
Find Your Watershed
KCGIS Center
King County GIS Center
King Street Center
201 S Jackson St
Suite 706
Seattle, WA 98104
giscenjer@!(ingcoun!y__c_Qov
+ 47 59909 N
· 122 33136 W
+ 47" 35' 56 72"
-122' 19' 52 90"
HOME NEWS S:'RVJCES :JIRc::CTORY (:QNTACT$earcr1 rerr'lS /. -------:--·------------1 [ Search
KCGIS Center
www.KingCounty.gov/GIS
King County Districts and Development Conditions for parcel
1123059092
Parcel number 1123059092 Drainage Lower Cedar River and
Address 684 NILE AVE Basin May Creek
NE WfJ.leratiec Ci::!:tac Bint l L.aki::
Jurisdiction Renton WashingtQn
Zipcode 98069 l'.YB18 Cedar·Sammamish 18)
Krotl Map page 806 PLSS SW-11-23-5
Thomas Guide 656 Latitude 47.49353
page Longitude -122.14297
Electoral Districts ~---·-····· -------------
Voting district RNT 11-3404 Fire district does not apply
King County Council district District 9, RH9i!D (J:ynn Water district King County Water mstrict
(206) 477-90
1009 ~ Sewer district does not apply
Congressional district 9 Water & Sewer district does not apply
Legislative district 11 Parks & Recreation does not apply
School district lssaguah #411 district
Seattle school board district does not apply (not in Hospital district do .. not apply
Seattle) Rural library district Rural King County Library
District Court electoral district Southeast System
Tribal Lands? No
_Ki_ng_C_ounty_planning ancl critical areas designations ____ ---~---_
King County zoning
Develqpment conditions
Comprehensive Plan
Urban Growth Area
Community Service Area
Community Planning Area
Coal mine hazards?
Erosion hazards?
Landslide hazards?
Seismic hazards?
NA, check with
jurisdiction
None
um
Urban
does not apply
Newcastle
None mapped
None mapped
None mapped
None mapped
Potential annexation area
Rural town?
Water service planning area
Roads MPS zone
Tfansportation Concurrency
Management
Forest Production district?
Agricultural Production district?
Critical aquifer recharge area?
100-year flood plain?
Wetlands at this parcel?
Within the Tacoma Smelter
Plume?
_ R~late_dr~s2urci)_s ___ ··-···----~---·
does not apply
No
does not apply
443
does not apply
No
No
None mapped
None mapped
ID= 3723B Rating= 4
(NWI)
20.1 ppm to 40.0 ppm
in Soil
http://www5 .king county .gov/kcgisreports/dd _report.aspx?P!N = l l 23059092 6/3/2014
KCGIS Parcel Reports
Districts and Development
Conditions Report
Find Your Council District
Find Your Watershed
KCGIS Genier
King County GIS Center
King Street Center
201 S Jackson St
Suite 706
Seattle, WA 98104
g iscen te r@k lrJ.9.£Q.\ffi.!Y.,_g QX
+ 47 59909 N
-122 33136 W
+ 47° 35' 56 72"
-122· 19' 52 90"
_H_O_M_E __ N_E_W_S __ S_E_R_V-JC_E_S_ --D-JR_E_C_T_O_R_Y_ CONTAClSearch Terms· cL _________ J ~~:iJ
KCGIS Center
www.KingCounty.gov/GIS
King County Districts and Development Conditions for parcel
1123059010
.,, .. ., ..
Parcel number 1123059010
Address 650 NILE AVE
Drainage
Basin
Lower Cedar River and
May Creek
NE
Jurisdiction Renton
Zipcode 98059
Kroll Map page 806
Thomas Guide 656
page
Electoral Districts
Voting distrid
King County Council district
Congressional district
Legislative district
School distrtct
Seattle school board district
Watershed
'flBl8
PLSS
Latitude
longitude
Cedar River I Lake
Washington
Cedar-Sammamish (8)
SW-11-23-5
47-49314
-122.14297
----------------·-· ---
RNT 11-3404
District 9, Reagan Dunn
(20G) 477.
1009 ~
9
11
Issaquah #411
does not apply (not in
Seattle)
Fire district does not apply
Water district King County Water District
90
Sewer district does not apply
Water & Sewer district does not apply
Parks & Recreation does not apply
district
Hospital district
Rural library district
does not apply
District Court electoral district Southeast
Rural King County Library
System
Tribal Lands? No
King County planning and critical areas designations
King County zoning
Development conditions
Comprehensive Ptan
Urban Growth Area
Community Service Area
Community Planning Area
Coal mine hazards?
Erosion hazards?
Landslide hazards?
Seismic hazards?
Related resources . --··--·' --·------
NA, check with
jurisdiction
None
um
Urban
does not apply
Newcastle
None mapped
None mapped
None mapped
None mapped
Potential annexation area
Rural town?
Water service planning area
Roads MPS zone
Transpor1ation Concurrency
Management
Forest Production district?
Agricultural Production district?
Critical aquifer recharge area?
100-year flood plain?
Wetlands at this parcel?
Y'Ylthio the racoma Smeller
~?
does not apply
No
does not apply
443
does not apply
No
No
None mapped
None mapped
ID = 3723B Rating = 4
(NWI)
20.1 ppm to 40.0 ppm
Esrimaled Af5enii: Con1:<1nlr:;ition
in s.,;1
http://www5.kingcounty.gov/kcgisreports/dd _report.aspx?PIN=l 1230590 I 0 6/3/2014
Appendix B
Resource Review & Off-site Analysis Documentation
~
~
~ <
''\PfT So,. T-_t.A ': T
N~ ~ST
~l'i[.!
?1<0 o 1:: er
<S'ITG
11
KING COUNTY
UNINCORPORATED AREAS
530071
Ht-4TH SI
,6,.Pl-'R:)X.11v1~ 1 l:. s.:_AL£ IN H.~ ~
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~-==r= }
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IIAPIIIIIIIEI
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e Technical Services
Planning/Bui .. rig/J>ublic WOlb
R. Mat;.Ow, D. Vlsneskl
JII\Wlry 22, 20Clll
R&nltm Municipal Coda
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One YearCaplure Zone
Fi~e Year Caplure Zone
D Ten Yea~ Capture Zone
Cedar Valley Sole Source
Aquifer Project Review Area
S1,eamnow Source >'rea
Aquifer Protection Area Zones
f::{{I Zone 1
;(_~ Zone I Mcd1f,ed
~Zone2
Network Structure
• Produclrnn 'Nell
• Springbrook S~nngs
Cedar Val'ey Sole Source Aquofer [.":~j Renlon City _1rn11s
[:J Potenhal Anne~at,on Area
Groundwater Protection Areas Dale: 01/09/2014
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Information Technology-GIS
mapsupport@renlonwa.gov
Printed on: 08/13/2012
Data Sources: Ci\)" of Renton. King County
This document is a graphic representation, mX guaranteed
to survey accuracy, and is based on the best information
avai(able as of the date shown fh1s map is intended for
City display purposes only
Coordiruml Sy&tam NAD 1083 HARN Sla/flP/Qm, W,uhmgkm Noflh F/PS 4~QI Feol
Projedian. Lamberl Conformal Can;c;
D,1/um: North Amen·can 1!J81 HARN
!..~j Renton City Limits
.t Education
.tJ Flee Statloas * Police Department
(:] Valley Medical Center
:!
'
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City display pu<p0!1eS only.
rnlo!fflal"ln T~y. GIS
meosupp0rt@re11tonwe ,;io>'
PfJ/'l\ecl en: 1211112012
Mcrti F11i:lerai Erm,rgency M.1.,agemant Agancy maps availall1e M
1ne FEMA w11b5:l11 al www.tema IJllwha:zan:1/mapil~de~ shim
0666F
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t;e\lar '<,ver rJcod halilrtl ome uooa(ed with FEMA Ce<:!a, R.v;,r
1..0MR (Case nc Oll-1 O-B5BQP) approved Deca~•ber 4. 201)(1
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C=3 Renton Cay Limits
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mapsupport@rentonwa go\/
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Data Sources City of Renton, King County
I..'
,[
(' '' ! ..
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.t' ' !'
This document is a graphic representation, not guaranteed
to survey accuracy, and is based on the best information
available as of lhe date shown Tnis map is intended for
City dispiay purposes only.
Coordm.te Sys/em: NAD 1983 11/J.RN .Sta/oPI'-""' Wa.,11~,gfort Norlh FIPS 4501 Feel
Prniedl()f): L"mberl Conformal Conic
Do/um Norll1 American 1983 HARN
' . !!
~~j Renton City Limits
!. Education
,ii Fice Statioos * Police Deparlment rn Valley Medical Center
City of Renton
Sensitive Areas
' .t
-.I,
0
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·-·I'.
0.25 0.5
Miles
Erosion Hazard
Severity
High
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mapsupport@rentonwa.gov
Printed on: oa10112012
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to survey accuracy, and 1s based on the best information
available as of the date shown. This map is intended for
City display purposes only.
·t." ' ji
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·.'-1
CoordinG/8 SyaJem NAO fg53 HARN S/916Plane WBsl!ingl'on Nortl! F/PS ~60f Feel
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£:) Valley Medical Center
(ii Renton City Limits
<
' '.
City of Renton
Sensitive Area
•· ,.
:!
' ' 0
Coal Mine Hazards
Severity
M HIGH
MODERATE
UNCLASSIFIED
0.25 05 1
Miles ______ J
r~. Cityol' ~-----r 1 ;-[l[(j(I
-"''. :::· ,,
\:·_ c.·;J
Reference 11-C
City of Renton Soil Survey Map
Public Works
Surface \Nater UtHity
G Del Rosario
12/22/2009
----
r~---·
_ r):·.·r,~')
0 0.5
Miles
c::J G1'1>1ln<M•ter Prot,ctionArea Boundl!Y
~uifef Prolllction ArH Zona 1
0 Aqu,19 FfalKIID~ Ahia Zona 1 Modifled t:·.:1 Renlon Oly U1T1b!,
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R Complai Prahl Recd Date Close Date Address Comments
ec nt No em
1 2006-RFN 7/28/2006 8/31/2006 12601 148TH AVE SE Stormwater from 148 Ave SE. Inv found 2 developments
0515 (under DDES) contributing. Provided DOES contacts.
I 1996-RUN 10/11/1996 11/8/1996 12227 148TH AVE SE ADJACENT PROPERTY IMPACTS FILLING???
1771 OFF
;, 1996-WET 2/7/1996 2/27/1996 12227 148TH AVE SE SAME AS 96-01S7
0323 LAN
D
1 1996-DIGG 2/7/1996 2/26/1996 12227 148TH AVE SE EXC IN WETLAND
0157 ING
Figure 3-1 Downstream Drainage Complaints
Notes
Ncll>e
0
Ci~fl
l '111a111<c' & I r I l i\'i,ici n
MA?
ti:lM. wtlll,!--!!=!!.
S'-~ 't)OWN.s'fl:'£AM. ~I~
Legend
Qty and County Bounda,y
~; C.ltr~R~
Parcels
New."Olil Struciures
o ""' -""· D V, r,V,.•
L.' o....,
''\ T>nl ' v .. ,
"'-
P,pe
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Open 0r3Jns
Fac1lrty Oull ine
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l nfonn.1t1on T,e,chnology G,s Jt• t , , •r "ti' -·"\'"'1 ;'.;· : • ' '-,~ 11"1 ',;IT'l.:.I '1.,· ~ · j ~ P, .111 l
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5/2312 014 Thi", MAP ,!:, l'.OT TO 5t: u::;t:u FOR MA i 11,;A I 10'1
Notes
None
0
C ity of Rerlton
Fin .111 .:c & IT I llvi.~ion
~AIN~
Legend
City and County Boundary
o:r-
~.! (,ryolRo-on
Parcels
Network Structures
D ""'
1o1-.
CJ \ft ,yv,.,
\.fnL!':OW,~
6,.• f'.11nlrnl S in ,r-h'"'
hiformatlofl Tf'chnology . GIS
Re,ntot1M~pS upPQrt@Re,,10nW~.gov
5/23/2014
Oeten!Jon F ~ities
V P-
0 Tank
v,.,.
Pipe
Culvert
Open Drains
Facility Ou tline
Priv;alA Ni>two,k ~1n 1r.lur~
f,-,-rr'l;!1t ,•,.-.ry ... i\T'" .. ~.Jn"~f" )C; v-,o
'i",r·•'.,.....ot -I .. C1•1.1, ... ,t-i,,.,.~pti'.)l' r:r:'5rJ~ ,,,. "'1"11 1 -. ·•
•·
THIS MAP IS NOT TO BE USED FOR NA'JIGA TION
Appendix C
Pond Sizing
I _, ~
·sw1t'~St>'
I f.
J
Reference 11-A
Peak Rate Flow Control Standard (Existing Sit1:1 Conditions)
Flow Control Dural:ion Slandard (Exis~ng Site Condi~ons)
~1~ Flow Control Duration Standard (Forested Conditions)
: \
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•. __
Flow Control Application Map N
A
Printed 1/14/2010 0 2
Miles
SECTION 3.2 Rli1'0FF COMPUTATJOJ-,; AND ANALYSIS METHODS
FIGURE 3.2.2.A RAINFALL REGIONS AND REGIONAL SCALE FACTORS
ST 1.1
ST 1.1
ST 1.0
Rainfall Regions and
Regional Scale Factors
; _____ Incorporated Area
--.r= River/Lake
Major Road
1/912009
3-22
LA 0.9 LA 1.0 LA 1.2
~lfQlfQl,IISH ~OUlfTY
l;l · ,o.,,,i ~ou11TY-
LA 1.0
2009 Surface Water Design Manual
3.2.2 KCRTS/RU!\OFF FJl.f'.S METHOD-GENERATING TIME SE!llr.S
·---
TABLE 3.2.2.B EQUIV ALEN CE BETWEEN SCS SOIL TYPES AND KCRTS SOIL TYPES
SCS Soil Type scs KCRTS Soil Notes
Hydrologic Group
Soil Group
Alderwood (AgB, Age, AgD) e Till
Arents, Alderwood Material (AmB, Ame) e Till
Arents, Everett Material (An) B Outwash 1
Beausite (Bee, BeD, BeF) e Till 2
Bellingham (Bh) D Till 3
Brisco! (Br) D Till 3
Buckley (Bu) D Till 4
Earlmont (Ea) D Till 3
Edgewick (Ed) e Till 3
Everett (EvB, Eve, EvD, Ewe) A/B Outwash 1
Indianola (lne, lnA, lnD) A Outwash 1
Kitsap (KpB, KpC, KpD) C Till
Klaus (Kse) e Outwash 1
Neilton (NeC) A Outwash 1
Newberg (Ng) B Till 3
Nooksack (Nk) e Till 3
Norma (No) D Till 3
Orcas (Or) D Wetland
Oridia (Os) D Till 3
Ovall (Ove, OvD, OvF) C Till 2
Pilchuck (Pc) e Till 3
Puget (Pu) D Till 3
Puyallup (Py) B Till 3
Ragnar (RaC, Rao, Rae, RaE) B Outwash 1
Renton (Re) D Till 3
Salal (Sa) C Till 3
Sammamish (Sh) D Till 3
Seattle (Sk) D Wetland
Shalcar (Sm) D Till 3
Si (Sn) e Till 3
Snohomish (So, Sr) D Till 3
Sultan (Su) C Till 3
Tukwila (Tu) D Till 3
Woodinville (Wo) D Till 3
Notes:
1. Where outwash soils are saturated or underlain at shallow depth (<5 feet) by glacial till, they should
be treated as till soils.
2. These are bedrock soils, but calibration of HSPF by King County DNRP shows bedrock soils to
have similar hydrologic response to till soils.
3. These are alluvial soils, some of which are underlain by glacial till or have a seasonally high water
table. In the absence of detailed study, these soils should be treated as till soils.
4. Buckley soils are formed on the low-permeability Osceola mudflow. Hydrologic response is
assumed to be similar to that of till soils.
2009 Surface Water Design Manual 119/2009
3-25
6.4.1 WETPONDS-BASIC AND LARGE-METHODS OF ANALYSIS
FIGURE 6.4.1.A PRECIPITATION FOR MEAN ANNUAL STORM IN INCHES (FEEn
ST 1.1
, __ i Incorporated Area
~ River/Lake
Major Road
0.47"
(0.039")
0.47"
(0.039')
NOTE: Areas east of the easternmost isopluvial should use 0.65
inches unless rainfall data is available for lhe location of interest
LA 1.2 ST 1.0/
LA0.8 LA. 0.9 LA 1.0
,,.,,.,.,,.,,,. ,,rn111,
-'!""""'~ ,----.-.-..r... -' ·-...
,'/ ,;i,
\,...,-"-"'\.l.
0.52"
(0.043') 0.56"
(0.047')
··-···-----·--· """ """"'
r)
\ . '·---,c
..,-..~ 0.65"
(0.054')
result, generates large amoW1ts offWloff. For this application, till soil types include Buckley and
bedrock soils, and alluvial and outwash soils that have a seasonally high water table or are underlain
at a shallow depth (less than 5 feet) by glacial till. U.S. Soil Conservation Service (SCS) hydrologic
soil groups that are classified as till soils include a few B, most C, and all D soils. See Chapter 3 for
classification of specific SCS soil types.
2009 Surface Water Design Manual l/912009
6-71
KCRTS Program ... file Directory:
C:IKC SWDMIKC DAT Al --::J CREA TE a new Time Series
T
I. 76 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
4040 Pre.tsf
T
1.00000
0.000000 Till forest
0. 000000 Ti II Pasture
0.000000 Till Grass
0.000000 Outwash Forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
[T] Enter the Analysis TOOLS Module
'] Compute PEAKS and Flow Frequencies
4040 Pre.tsf
14040_Pre.pks
q RETURN to Previous Menu
:J CREATE a new Time Series
ST
0.00 0.00
0.00 0.00
0.65 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
1.1 1 0.00
14040 Dev. tsf
1.00000
T
0. 000000 Till forest
0.000000 Till Pasture
0. 000000 Ti II Grass
0.000000 Outwash forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
'] Enter the Analysis TOOLS Module
'] Compute PEAKS and Flow Frequencies
14040 Dev.tsf
W40_Dev.pks
t] RETURN to Previous Menu
[CJ CREATE a new Time Series
r
0.00 0.00
0.00 0.00
0.65 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
1.11 0.00
1040 Devi 5.tsf
1.00000
0.000000 Till Forest
0.000000 Till Pasture
0. 000000 Till Grass
0.000000 Outwash Forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
F
[T] Enter the Analysis TOOLS Module
[P] Compute PEAKS and Flow Frequencies
14040 Devl5.tsf
14040 _ Devl 5.pks
[DJ Compute Flow DURATION and Exceedence
14040 Pre.tsf
14040 Pre.dur
F
F
36
0.0031
0.025
[RJ RETURN to Previous Menu
Retention/Detention Facility
Type of Facility:
Facility Length:
Facility Width:
Facility Area:
Effective Storage Depth:
Stage O Elevation:
Storage Volume:
Riser Head:
Riser Diameter:
Number of orifices:
Detention Vault
80.00 ft
62.00 ft
4960. sq.
4.70 ft
509.00 ft
23312. cu.
4.70 ft
ft
ft
12.00 inches
2
Full Head Pipe
Orifice# Height
(ft)
0.00
3.05
Diameter Discharge Diameter
1
2
Top Notch Weir:
Outflow Rating Curve:
(in)
0.68
1.44
None
None
(CFS) (in)
0.027
0.072 4.0
Stage Elevation Storage Discharge
(ft) (ft) (cu. ft) (ac-ft) (cfs)
0.00 509.00 0. 0.000 0.000
0.01 509.01 50. 0.001 0.001
0.02 509.02 99. 0.002 0.002
0.03 509.03 149. 0.003 0.002
0.04 509.04 198. 0.005 0.003
0.05 509.05 248. 0.006 0.003
0.06 509.06 298. 0.007 0.003
0.16 509.16 794. 0.018 0.005
0.26 509.26 1290. 0.030 0.006
0.36 509.36 1786. 0.041 0.007
0.46 509.46 2282. 0.052 0.008
0.56 509.56 2778. 0.064 0.009
0.66 509.66 3274. 0.075 0.010
0.76 509.76 3770. 0.087 0. 011
0.86 509.86 4266. 0.098 0.012
0.96 509.96 4762. 0.109 0.012
1. 06 510.06 5258. 0.121 0. 013
1.16 510.16 5754. 0 .132 0. 013
1.26 510.26 6250. 0.143 0. 014
1.36 510.36 6746. 0.155 0.015
1.46 510.46 7242. 0.166 0.015
1. 56 510.56 7738. 0.178 0.016
1. 66 510.66 8234. 0.189 0.016
1. 76 510.76 8730. 0.200 0.017
1. 86 510.86 9226. 0.212 0.017
1. 96 510. 96 9722. 0.223 0.017
2.06 511. 06 10218. 0.235 0.018
2.16 511.16 10714. 0.246 0.018
2.26 511. 26 11210. 0.257 0.019
Percolation
(cfs)
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
2.36 511.36 11706. 0.269 0.019 0.00
2.46 511. 46 12202. 0.280 0.020 0.00
2.56 511. 56 12698. 0.291 0.020 0.00
2.66 511. 66 13194. 0.303 0.020 0.00
2.76 511.76 13690. 0 .314 0. 021 0.00
2.86 511. 86 14186. 0.326 0.021 0.00
2.96 511. 96 14682. 0.337 0.021 0.00
3.05 512.05 15128. 0.347 0.022 0.00
3.07 512.07 15227. 0.350 0.022 0.00
3.08 512.08 15277. 0.351 0.024 0.00
3.10 512.10 15376. 0.353 0.026 0.00
3 .11 512 .11 15426. 0.354 0.029 0.00
3 .13 512 .13 15525. 0.356 0.033 0.00
3.14 512 .14 15574. 0.358 0.037 0.00
3.16 512.16 15674. 0.360 0.040 0.00
3.17 512.17 15723. 0.361 0.042 0.00
3.27 512. 27 16219. 0.372 0.049 0.00
3.37 512.37 16715. 0.384 0.055 0.00
3.47 512. 47 17211. 0.395 0.060 0.00
3.57 512.57 17707. 0.407 0.064 0.00
3.67 512.67 18203. 0.418 0.068 0.00
3.77 512.77 18699. 0 .429 0.072 0.00
3.87 512.87 19195. 0.441 0.075 0.00
3.97 512.97 19691. 0.452 0.079 0.00
4.07 513. 07 20187. 0.463 0.082 0.00
4.17 513 .17 20683. 0.475 0.085 0.00
4.27 513. 27 21179. 0.486 0.088 0.00
4.37 513. 37 21675. 0.498 0.091 0.00
4.47 513 .47 22171. 0.509 0.093 0.00
4.57 513. 57 22667. 0.520 0.096 0.00
4.67 513.67 23163. 0.532 0.099 0.00
4.70 513.70 23312. 0.535 0.099 0.00
4.80 513.80 23808. 0. 547 0. 410 0.00
4.90 513.90 24304. 0.558 0.975 0.00
5.00 514.00 24800. 0.569 1.710 0.00
5.10 514 .10 25296. 0.581 2.500 0.00
5.20 514. 2 0 25792. 0.592 2.790 0.00
5.30 514.30 26288. 0.603 3.040 0.00
5.40 514. 40 26784. 0.615 3.280 0.00
5.50 514. 50 27280. 0.626 3.500 0.00
5.60 514. 60 27776. 0.638 3.710 0.00
5.70 514.70 28272. 0.649 3.900 0.00
5.80 514.80 28768. 0.660 4.090 0.00
5.90 514.90 29264. 0.672 4.270 0.00
6.00 515.00 29760. 0.683 4.440 0.00
6.10 515.10 30256. 0.695 4.600 0.00
6.20 515. 20 30752. 0.706 4.760 0.00
6.30 515.30 3124 8. 0. 717 4.920 0.00
6.40 515 .40 31744. 0.729 5.070 0.00
6.50 515.50 32240. 0.740 5.210 0.00
6.60 515.60 32736. 0.752 5.350 0.00
6.70 515.70 33232. 0.763 5.490 0.00
Hyd Inflow Outflow Peak Storage
Target Cale Stage Elev
1 0.66 ******* 0.35 4.78 513.78
2 0.33 ******* 0.09 4.49 513.49
3 0. 3 9 0.10 0.08 4.12 513 .12
4 0.33 ******* 0.08 3.95 512.95
5 0.35 ******* 0.04 3.21 512. 21
6 0.21 0.06 0.02 2.97 511. 97
7 0.27 ******* 0.02 2.90 511. 90
8 0. 29 ******* 0.02 1. 78 510.78
----------------------------------
Route Time Series through Facility
Inflow Time Series File:14040 dev.tsf
Outflow Time Series File:rdout vault
Inflow/Outflow Analysis
Peak Inflow Discharge:
Peak Outflow Discharge:
Peak Reservoir Stage:
Peak Reservoir Elev:
0.662
0.350
4.78
513.78
CFS
CFS
Ft
Ft
at
at
Peak Reservoir Storage: 23713. Cu-Ft
0.544
Flow Frequency Analysis
Time Series File:rdout vault.tsf
Project Location:Sea-Tac
Ac-Ft
(Cu-Ft) (Ac-Ft)
23713. 0.544
2224 9. 0. 511
20424. 0.469
19569. 0.449
15906. 0.365
14 72 9. 0.338
14364. 0.330
8847. 0.203
6:00 on Jan 9 in Year 8
10:00 on Jan 9 in Year 8
---Annual Peak Flow Rates--------Flow Frequency Analysis-------
Flow Rate Rank Time of Peak
(CFS)
--Peaks --Rank Return Prob
0. 099 2
0. 021 7
0. 084 3
0. 017 8
0. 022 6
0. 046 5
0.078 4
0.350 1
Computed Peaks
Flow Duration
Cutoff Count
CFS
0.002
0.004
0.007
0.010
0. 013
0.015
0.018
0.021
0.024
0.026
0.029
27402
7586
7679
5690
4636
3467
2390
1461
645
34
12
(CFS) (ft) Period
2/09/01
1/07/02
3/06/03
8/26/04
1/08/05
1/19/06
11/24/06
1/09/08
20:00
4:00
22:00
8:00
6:00
1:00
8:00
10:00
0.350
0.099
0.084
0.078
0.046
0.022
0.021
0.017
0.267
4.78
4.70
4.12
3.95
3.23
3.02
2.97
1. 79
4.75
from Time Series File:rdout vault.tsf
1
2
3
4
5
6
7
8
100.00
25.00
10.00
5.00
3.00
2.00
1. 30
1.10
50.00
Frequency CDF Exceedence_Probability
% % %
44.687
12. 371
12.523
9.279
7.560
5.654
3.898
2.383
1.052
0.055
0.020
44.687
57.058
69.581
78.860
86 .42 0
92.074
95.972
98.355
99.406
99.462
99.481
55. 313
42.942
30.419
21.140
13. 580
7.926
4.028
1.645
0.594
0.538
0.519
0.553E+OO
0.429E+OO
0.304E+OO
0.211E+OO
0 .136E+OO
0.793E-Ol
0.403E-01
0.165£-01
0.594£-02
0.538£-02
0.519£-02
0.990
0. 960
0.900
0.800
0.667
0.500
0.231
0. 091
0.980
0.032
0.035
0.037
0.040
0.043
0.046
0.048
0.051
0.054
0.057
0.059
0.062
0.065
0.068
0.070
0.073
0.076
0.079
0.081
0.084
0.087
0.090
0.092
0.095
0.098
16
10
9
15
29
29
25
24
19
13
13
7
10
7
11
13
10
10
7
14
8
2
5
4
3
Discharge Volume
0.026
0.016
0.015
0.024
0.047
0.047
0. 041
0.039
0.031
0.021
0.021
0. 011
0.016
0 .011
0.018
0.021
0.016
0.016
0. 011
0.023
0. 013
0.003
0.008
0.007
0.005
99.507
99.524
99.538
99.563
99.610
99.658
99.698
99.737
99.768
99.790
99. 811
99.822
99.839
99.850
99.868
99.889
99.905
99.922
99.933
99.956
99.969
99.972
99.980
99.987
99.992
Discharge Volume from Time Series
rdout vault.tsf
0.492
0.476
0.462
0.437
0.390
0.342
0.302
0.263
0.232
0.210
0.189
0.178
0.161
0.150
0 .132
0 .111
0.095
0.078
0.067
0.044
0.031
0.028
0.020
0. 013
0.008
between 10/01/00 00:00 and 10/30/00 23:59
24881. Cu-Ft or 0.571 Ac-Ft in
Duration Comparison Anaylsis
Base File: 14040_pre.tsf
New File: rdout vault.tsf
Cutoff Units: Discharge in CFS
0.492E-02
0.476E-02
0.462E-02
0.437E-02
0.390E-02
0.342E-02
0.302E-02
0.263E-02
0.232E-02
0.210E-02
0.189E-02
0.178E-02
0.161E-02
0.150E-02
0 .132E-02
0. lllE-02
0.946E-03
0.783E-03
0.669E-03
0.440E-03
0.310E-03
0.277E-03
0.196E-03
0 .130E-03
0.815E-04
30.0 days
-----Fraction of Time--------------Check of Tolerance-------
Cutoff Base New %Change Probability Base New %Change
0.025 0.92E-02 0.57E-02 -37.9 I 0.92E-02 0.025 0.021 -15.0
0.031 0.62E-02 0.50E-02 -19.3 I 0.62E-02 0.031 0.022 -28.9
0.038 0.49E-02 0.45E-02 -7.0 I 0.49E-02 0.038 0.033 -13. 9
0.045 0.37E-02 0.36E-02 -0.9 I 0.37E-02 0. 045 0.044 -0.9
0.051 0.28E-02 0.26E-02 -6.4 I 0.28E-02 0.051 0.050 -2.3
0.058 0.22E-02 0.20E-02 -7.4 I 0.22E-02 0.058 0.056 -3.7
0.065 0.15E-02 0.17E-02 13. 3 I 0.15E-02 0.065 0.068 5.6
0. 071 0.99E-03 0.12E-02 24.6 I 0.99E-03 0. 071 0.075 4. 9
0.078 0.60E-03 0.83E-03 37.8 I 0.60E-03 0.078 0.082 6.0
0.084 0.34E-03 0.44E-03 28.6 I 0.34E-03 0.084 0.086 2.2
0.091 0.21E-03 0.24E-03 15.4 I 0.21E-03 0. 091 0.092 1.4
0.098 0.16E-03 0.82E-04 -50.0 I 0.16E-03 0.098 0.094 -3.7
0.104 0.llE-03 O.OOE+OO -100.0 I 0. llE-03 0.104 0. 096 -7.7
0 .111 0.16E-04 O.OOE+OO -100.0 I 0.16E-04 0 .111 0.099 -10.7
Maximum positive excursion= 0.005 cfs ( 7.1%)
occurring at 0.076 cfs on the Base Data:14040_pre.tsf
and at 0.081 cfs on the New Data:rdout vault.tsf
Maximum negative excursion~ 0.009 cfs (-29.4%)
occurring at 0.032 cfs on the Base Data:14040_pre.tsf
and at 0.022 cfs on the New Data:rdout vault.tsf
iii
"-s
~ e> m
£
0 w
0
10
•
10-
o rdou'. __ vHult.pks iri Sea-Tac
~1!0'1::J pre pks
0
Return Period
2 5 101 20 50 109 ~ ______ _L ___ _L._ __ _L ___ L_ _ __c
0
00
95 98 99
Cumulative Probability
8
D
0
0
":'
0
"/
0
~
"? ,------+,-------,------1------+-------+-------l-o
2:("0 0("0 B O 9 ·o t,Cl"O c: ·o oo·
(s~::,) aBJB4:lS!O
Q)
()
C
Q)
" Q)
Q)
()
X
lJ.J
£
i5
"' .a e
0..
KCRTS Program ... File Directory:
C:\KC SWDM\KC DATA\ --
[C) CREATE a new Time Series
ST
1.31 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
14040Pre.tsf
T
1.00000
T
0.000000 Till Forest
0.000000 Till Pasture
0.000000 Till Grass
0.000000 Outwash Forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
[T] Enter the Analysis TOOLS Module
[P] Compute PEAKS and Flow Frequencies
14040 Pre.tsf
14040 _pre.pks
[R] RETURN to Previous Menu
[C] CREATE a new Time Series
ST
0.00 0.00
0.00 0.00
0.01 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.04 0.00
14040 _ Bypass.tsf
T
1.00000
T
0.000000 Till Forest
0.000000 Till Pasture
0.000000 Till Grass
0.000000 Outwash Forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
[T] Enter the Analysis TOOLS Module
tP] Compute PEAKS and Flow Frequencies
14040 _ Bypass.tsf
14040 _ Bypass.pks
[R] RETURN to Previous Menu
[CJ CREATE a new Time Series
ST
0.00
0.00
0.88
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.43 0.00
14040 Dev .tsf
T
1.00000
0.000000 Till Forest
0.000000 Till Pasture
0.000000 Till Grass
0.000000 Outwash forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
, .·] Enter the Analysis TOOLS Module
rpJ Compute PEAKS and Flow Frequencies
!040 Dev.tsf
. 1040_Dev.pks
rRJ RETURN to Previous Menu
:J CREA TE a new Time Series
C r
0.00 0.00
0.00 0.00
0.88 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.43 0.00
. (040 Devl5.tsf
T
1.00000
0.000000 Till Forest
0. 000000 Till Pasture
0. 000000 Till Grass
0.000000 Outwash Forest
0.000000 Outwash Pasture
0.000000 Outwash Grass
0.000000 Wetland
0.000000 Impervious
fTJ Enter the Analysis TOOLS Module
J Compute PEAKS and Flow Frequencies
. 1040 Dev15.tsf
14040_Dev15.pks
1] Compute Flow DURATION and Exceedence
.. 040 Pre.tsf
14040 Pre.dur
36
J.0023
).018
fRJ RETURN to Previous Menu
Retention/Detention Facility
Type of Facility:
Side Slope:
Pond Bottom Length:
Pond Bottom Width:
Pond Bottom Area:
Top Area at 1 ft. FB:
Effective Storage Depth:
Stage O Elevation:
Storage Volume:
Riser Head:
Riser Diameter:
Number of orifices:
Orifice#
1
2
Height
(ft)
0.00
2.40
Detention Pond
2.40 H:lV
80.00 ft
40.00 ft
3200. sq. ft
6103. sq. ft
0.140 acres
3.30 ft
520.00 ft
13972. cu. ft
0.321 ac-ft
3.30
12.00
2
Diameter
(in)
0.56
1. 38
ft
inches
Full Head
Discharge
(CFS)
0.016
0.049
Top Notch Weir: None
Outflow Rating Curve: None
Pipe
Diameter
(in)
4.0
Stage Elevation Storage Discharge Percolation
Area
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
ft)
0.00 520.00 0. 0.000 0.000 0.00
3200.
0.01 520.01 32. 0.001 0.001 0.00
3206.
0.02 520.02 64. 0.001 0.001 0.00
3212.
0.03 520.03 96. 0.002 0.001 0.00
3217.
0.04 520.04 129. 0.003 0.002 0.00
3223.
0.05 520.05 161. 0.004 0.002 0.00
3229.
0.15 520.15 487. 0. 011 0.003 0.00
3287.
0.25 520.25 818. 0.019 0.004 0.00
3345.
0.35 520.35 1156. 0.027 0.005 0.00
3404.
0 .45 520.45 1499. 0.034 0.006 0.00
3464.
0.55 520.55 1848. 0.042 0.006 0.00
3524.
Surf
(sq.
0.65 520.65 2204. 0.051 0.007 0.00
3584.
0.75 520.75 2565. 0.059 0.007 0.00
3645.
0.85 520.85 2933. 0.067 0.008 0.00
3706.
0.95 520.95 3307. 0.076 0.008 0.00
3768.
1. 05 521.05 3686. 0.085 0.009 0.00
3830.
1.15 521.15 4073. 0.093 0.009 0.00
3893.
1.25 521. 25 4465. 0.103 0.010 0.00
3956.
1.35 521. 35 4864. 0 .112 0.010 0.00
4020.
1.45 521.45 5269. 0.121 0.010 0.00
4084.
1. 55 521.55 5681. 0 .130 0. 011 0.00
4148.
1. 65 521.65 6099. 0.140 0. 011 0.00
4213.
1. 75 521. 75 6523. 0.150 0. 011 0.00
4279.
1. 85 521.85 6954. 0.160 0.012 0.00
4344.
1. 95 521. 95 7392. 0.170 0.012 0.00
4411.
2.05 522.05 7837. 0.180 0.012 0.00
4478.
2.15 522.15 8288. 0.190 0. 013 0.00
4545.
2.25 522.25 8746. 0.201 0. 013 0.00
4613.
2.35 522.35 9210. 0.211 0. 013 0.00
4681.
2.40 522.40 9445. 0.217 0.013 0.00
4715.
2.41 522.41 9492. 0.218 0.014 0.00
4722.
2.43 522.43 9587. 0.220 0.015 0.00
4736.
2.44 522.44 9634. 0.221 0.017 0.00
4743.
2.46 522.46 9729. 0.223 0.020 0.00
4756.
2.47 522.47 9777. 0.224 0.023 0.00
4763.
2.49 522.49 9872. 0.227 0.027 0.00
4777.
2.50 522.50 9920. 0.228 0.030 0.00
4784.
2.51 522.51 9968. 0.229 0.031 0.00
4791.
2.61 522.61 10450. 0.240 0.038 0.00
4860.
2. 71 522. 71 10940. 0.251 0.043 0.00
4930.
2.81 522.81 11436. 0.263 0.047 0.00
5000.
2. 91 522. 91 11940. 0.274 0.051 0.00
5071.
3.01 523.01 124 51. 0.286 0.055 0.00
5143.
3 .11 523 .11 12969. 0.298 0.058 0.00
5214.
3.21 523.21 13494. 0.310 0.062 0.00
5286.
3.30 523.30 13972. 0. 321 0.064 0.00
5352.
3.40 523.40 14511. 0.333 0.375 0.00
5425.
3.50 523.50 15057. 0.346 0.941 0.00
5498.
3.60 523.60 15611. 0.358 1.670 0.00
5572.
3.70 523.70 16172. 0.371 2.470 0.00
5647.
3.80 523.80 16740. 0.384 2.750 0.00
5721.
3.90 523.90 17316. 0.398 3.010 0.00
5797.
4.00 524.00 17900. 0 .411 3.250 0.00
5873.
4.10 524.10 18491. 0.424 3.470 0.00
5949.
4.20 524.20 19089. 0.438 3.670 0.00
6026.
4.30 524.30 19696. 0.452 3.870 0.00
6103.
4.40 524.40 20310. 0.466 4.060 0.00
6180.
4.50 524.50 20932. 0.481 4.240 0.00
6259.
4.60 524. 6 0 21562. 0.495 4.410 0.00
6337.
4.70 524.70 22199. 0.510 4.570 0.00
6416.
4.80 524.80 22845. 0.524 4.730 0.00
6496.
4.90 524.90 23498. 0.539 4.880 0.00
6576.
5.00 525.00 2416 0. 0.555 5.030 0.00
6656.
5.10 525.10 24830. 0.570 5.180 0.00
6737.
5.20 525.20 25507. 0.586 5.320 0.00
6818.
5.30 525.30 26193. 0.601 5.460 0.00
6900.
Hyd Inflow Outflow Peak
Stage Elev
1 0. 3 9 0.12 3.32 523.32
2 0.18 0.06 3.16 523.16
3 0.22 0.05 3.00 523.00
4 0.18 0.04 2.69 522.69
5 0.19 0.03 2.49 522.49
6 0 .11 0.01 2.38 522.38
7 0 .13 0.01 2.28 522.28
8 0.12 0.01 0.97 520.97
Hyd R/D Facility Tributary Reservoir
Outflow Inflow Inflow
1 0.12 0.02 ********
2 0.06 0.01 ********
3 0.05 0.01 ********
4 0.04 0.01 ********
5 0.03 0.01 ********
6 0.01 0.01 ********
7 0.01 0.01 ********
8 0.01 0.01 ********
----------------------------------
Route Time Series through Facility
Inflow Time Series File:14040 dev.tsf
Outflow Time Series File:rdout Pond
POC Time Series File:dsout Pond
Inflow/Outflow Analysis
Storage
(Cu-Ft) (Ac-Ft)
14061. 0.323
13245. 0.304
12387. 0.284
10845. 0.249
9874. 0.227
9357. 0.215
8899. 0.204
3382. 0.078
POC Outflow
Target Cale
******* 0.12
******* 0.06
0.06 0.06
******* 0.04
******* 0.03
0.03 0.02
******* 0.02
******* 0.02
Peak Inflow Discharge: 0.389 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.116 CFS at 11:00 on Jan 9 in Year 8
Peak Reservoir Stage: 3.32 Ft
Peak Reservoir Elev: 523.32 Ft
Peak Reservoir Storage: 14061. Cu-Ft
0.323 Ac-Ft
Add Time Series:14040_bypass.tsf
Peak Summed Discharge: 0.120 CFS at 11:00 on Jan 9 in Year 8
Point of Compliance File:dsout_Pond.tsf
Flow Frequency Analysis
Time Series File:rdout_pond.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--------Flow Frequency Analysis-------
Flow Rate Rank Time of Peak --Peaks --Rank Return Prob
(CFS) (CFS) (ft) Period
0.064 2 2/09/01 23:00 0 .116 3.32 1 100.00 0.990
0. 013 7 1/08/02 5:00 0.064 3.28 2 25.00 0.960
0.055 3 3/06/03 23:00 0.055 3.00 3 10.00 0.900
0.008 8 8/26/04 11:00 0.042 2.69 4 5.00 0.800
0. 013 6 1/08/05 8:00 0.028 2.49 5 3.00 0.667
0.028 5 1/19/06 19,00
0.042 4 11/24/06 15,00
0.116 1 1/09/08 11,00
Computed Peaks
Flow Frequency Analysis
Time Series File,dsout_pond.tsf
Project Location,Sea-Tac
0. 013
0. 013
0.008
0.098
2.40
2.33
0.97
3.31
6
7
8
2.00
1. 30
1.10
50.00
0.500
0.231
0.091
0.980
---Annual Peak Flow Rates--------Flow Frequency Analysis-------
Flow Rate Rank Time of Peak
(CFS)
--Peaks Rank Return Prob
(CFS) Period
0. 068 2
0. 02 0 6
0.058 3
0.017 7
0.017 8
0. 02 8 5
0. 043 4
0. 12 0 1
Computed Peaks
2/09/01
1/05/02
3/06/03
8/26/04
1/05/05
1/19/06
11/24/06
1/09/08
18,00
16,00
19,00
2,00
8,00
19,00
12,00
11,00
0.120
0.068
0.058
0.043
0.028
0.020
0.017
0.017
0.103
Flow Duration from Time Series File,rdout__pond.tsf
1
2
3
4
5
6
7
8
100.00
25.00
10.00
5.00
3.00
2.00
1. 30
1.10
50.00
Cutoff Count Frequency CDF Exceedence_Probability
CFS % % %
0.001 31998 52.182 52.182 47.818 0.478E+OO
0.003 6454 10.525 62.707 37.293 0.373E+OO
0.005 5579 9.098 71.805 28.195 0.282E+OO
0.006
0.008
0.010
0.012
0. 013
0.015
0.017
0.019
0.020
0.022
0.024
0.026
0.027
0.029
0.031
0.033
0.034
0.036
0.038
0.040
0.042
0.043
0.045
0.047
0.049
0.050
0.052
5702
4287
2220
2550
1935
104
47
51
37
16
17
25
30
22
21
29
16
14
11
27
16
15
7
11
7
6
9
9 .299
6. 991
3.620
4.159
3.156
0.170
0.077
0.083
0.060
0.026
0.028
0. 041
0. 049
0.036
0.034
0.047
0.026
0.023
0.018
0.044
0.026
0.024
0. 011
0.018
0. 011
0.010
0.015
81.104
88.095
91. 716
95.874
99.030
99.199
99. 2 76
99.359
99.419
99.446
99. 4 73
99.514
99.563
99.599
99.633
99.680
99.706
99. 729
99.747
99.791
99.817
99.842
99.853
99. 871
99.883
99.892
99.907
18. 896
11. 905
8.284
4.126
0.970
0.801
0.724
0. 641
0.581
0.554
0.527
0.486
0.437
0.401
0.367
0.320
0.294
0 .271
0.253
0.209
0.183
0.158
0.147
0.129
0 .117
0.108
0.093
0.189E+OO
0 .119E+OO
0.828E-01
0.413E-Ol
0.970E-02
0.801E-02
0.724E-02
0.641E-02
0.581E-02
0.554E-02
0.527E-02
0.486E-02
0.437E-02
0.401E-02
0.367E-02
0.320E-02
0.294E-02
0.271E-02
0.253E-02
0.209E-02
0.183E-02
0.158E-02
0.147E-02
0.129E-02
0. ll 7E-02
0.108E-02
0.930E-03
0.990
0.960
0.900
0.800
0.667
0.500
0.231
0.091
0.980
0.054
0.056
0.057
0.059
0.061
0.063
10
9
4
5
9
9
0.016
0.015
0.007
0.008
0.015
0.015
99.923
99.938
99.945
99.953
99.967
99.982
0.077
0.062
0.055
0.047
0.033
0.018
0.766E-03
0.620E-03
0.554E-03
0.473E-03
0.326E-03
0.179E-03
Flow Duration from Time Series File:dsout pond.tsf
Cutoff Count Frequency CDF Exceedence Probability
CFS % % %
0.001
0.003
0.005
0.007
0.009
0.010
0.012
0.014
0.016
0.018
0.020
0.022
0.024
0.025
0.027
0.029
0.031
0.033
0.035
0.037
0.039
0.041
0.042
0.044
0.046
0.048
0.050
0.052
0.054
0.056
0.058
0.059
0.061
0.063
0.065
0.067
28611
9639
5508
5841
4146
3067
2283
1373
291
91
85
31
24
19
23
29
21
30
25
15
13
16
34
6
8
11
8
6
9
10
8
6
7
9
13
2
Discharge Volume
46.659
15. 719
8.982
9.525
6.761
5.002
3.723
2.239
0.475
0.148
0 .139
0.051
0.039
0.031
0.038
0.047
0.034
0. 049
0.041
0.024
0.021
0.026
0.055
0.010
0. 013
0.018
0. 013
0.010
0.015
0.016
0. 013
0.010
0. 011
0.015
0.021
0.003
46.659
62.378
71.360
80.886
87.647
92.648
96.371
98. 611
99.085
99.234
99.372
99.423
99.462
99.493
99.530
99.578
99.612
99.661
99.702
99.726
99.747
99.773
99.829
99.839
99.852
99.870
99.883
99.892
99.907
99.923
99.936
99.946
99.958
99.972
99.993
99.997
Discharge Volume from Time Series
rdout_pond.tsf
53.341
37.622
28.640
19.114
12.353
7.352
3.629
1.389
0. 915
0.766
0.628
0.577
0.538
0.507
0.470
0.422
0.388
0.339
0.298
0.274
0.253
0.227
0.171
0.161
0.148
0 .130
0 .117
0.108
0.093
0.077
0.064
0.054
0.042
0.028
0.007
0.003
between 10/01/00 00:00 and 10/30/00 23:59
14850. Cu-Ft or 0.341 Ac-Ft in
Duration Comparison Anaylsis
0.533E+OO
0.376E+OO
0.286E+OO
0.191E+OO
0.124E+OO
0.735E-01
0.363E-01
0.139E-01
0.915E-02
0.766E-02
0.628E-02
0.577E-02
0.538E-02
0.507E-02
0.470E-02
0.422E-02
0.388E-02
0.339E-02
0.298E-02
0.274E-02
0.253E-02
0.227E-02
0.171E-02
0.161E-02
0.148E-02
0.130E-02
0.117E-02
0.108E-02
0.930E-03
0.766E-03
0.636E-03
0.538E-03
0.424E-03
0.277E-03
0.652E-04
0.326E-04
30.0 days
Base File: 14040_pre.tsf
New File: dsout_pond.tsf
Cutoff Units: Discharge in CFS
-----Fraction of Time--------------Check of
Cutoff Base New %Change Probability Base
0.018 0.99E-02 0.77E-02 -22.4 I 0.99E-02 0.018
0.023 0.64E-02 0.56E-02 -12.8 I 0.64E-02 0.023
0.028 0.50E-02 0.46E-02 -8.8 I 0.50E-02 0.028
0.033 0.38E-02 0.35E-02 -7.8 I 0.38E-02 0.033
0.038 0.29E-02 0.27E-02 -6.7 I 0.29E-02 0.038
0.043 0.22E-02 0.17E-02 -24.3 I 0.22E-02 0.043
0.048 0.15E-02 0.14E-02 -10.6 I 0.15E-02 0.048
0.053 0.lOE-02 O.lOE-02 -1. 6 I O.lOE-02 0.053
0.058 0.65E-03 0.64E-03 -2.5 I 0.65E-03 0.058
0.063 0.34E-03 0.36E-03 4.8 I 0.34E-03 0.063
0.068 0.23E-03 0.33E-04 -85.7 I 0.23E-03 0.068
0.072 0.16E-03 O.OOE+OO -100.0 I 0.16E-03 0.072
0.077 O.llE-03 0.00E+OO -100.0 I 0. llE-03 0.077
0.082 0.16E-04 O.OOE+OO -100.0 I 0.16E-04 0.082
Maximum positive excursion = 0.001 cfs 2.1%)
occurring at 0.059 cfs on the Base Data:14040_pre.tsf
and at 0.060 cfs on the New Data:dsout_pond.tsf
Maximum negative excursion= 0.014 cfs (-17.9%)
occurring at 0.080 cfs on the Base Data:14040_pre.tsf
and at 0.065 cfs on the New Data,dsout_pond.tsf
Route Time Series through Facility
Inflow Time Series File:14040 dev.tsf
Outflow Time Series File:rdout Pond
POC Time Series File:dsout Pond
Inflow/Outflow Analysis
Peak Inflow Discharge:
Peak Outflow Discharge:
Peak Reservoir Stage:
Peak Reservoir Elev:
0.389 CFS
0 .116 CFS
3.32 Ft
523.32 Ft
at
at
Peak Reservoir Storage: 14061. Cu-Ft
0.323 Ac-Ft
Add Time Series:14040_bypass.tsf
6:00 on
11:00 on
Jan
Jan
Tolerance-------
New %-Change
0.016 -13.1
0.020 -13.3
0.026 -6.7
0.032 -3.5
0.036 -5.3
0.041 -4. 9
0.046 -4.3
0.053 -0.1
0.057 -0.5
0.063 0.2
0.064 -5.4
0.065 -10.9
0.065 -16.2
0.068 -17.5
9 in Year 8
9 in Year 8
Peak Summed Discharge: 0.120 CFS at 11,00 on Jan 9 in Year 8
Point of Compliance File:dsout_Pond.tsf
Flow Frequency Analysis
Time Series File:rdout_pond.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--------Flow Frequency Analysis-------
Flow Rate Rank Time of Peak --Peaks --Rank Return Prob
(CFS) (CFS) (ft) Period
0.064 2 2/09/01 23:00 0 .116 3.32 1 100.00 0.990
0. 013 7 1/08/02 5:00
3/06/03 23:00
8/26/04 11:00
1/08/05 8:00
1/19/06 19:00
0.055 3
0.008 8
0. 013 6
0. 028 5
0. 042 4 11/24/06 15:00
1/09/08 11:00 0 .116 1
Computed Peaks
Flow Frequency Analysis
Time Series File:dsout_pond.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates---
Flow Rate Rank Time of Peak
(CFS)
0.068
0.020
0.058
0.017
0.017
0.028
0.043
0.120
Computed Peaks
2 2/09/01 18:00
6 1/05/02 16:00
3 3/06/03 19:00
7 8/26/04 2:00
8 1/05/05 8:00
5 1/19/06 19:00
4 11/24/06 12:00
1 1/09/08 11:00
0.064
0.055
0.042
0.028
0. 013
0. 013
0.008
0.098
3.28
3.00
2.69
2.49
2.40
2.33
0.97
3.31
2
3
4
5
6
7
8
25.00
10.00
5.00
3.00
2.00
1. 30
1.10
50.00
0. 960
0.900
0.800
0.667
0.500
0.231
0.091
0.980
-----Flow Frequency Analysis-------
--Peaks Rank Return Prob
(CFS) Period
0.120 1 100.00 0.990
0.068 2 25.00 0.960
0.058
0.043
0.028
0.020
0.017
0.017
0.103
3
4
5
6
7
8
10.00
5.00
3.00
2.00
1. 30
1.10
50.00
0.900
0.800
0.667
0.500
0.231
0.091
0.980
Flow Duration from Time Series File:rdout_pond.tsf
Cutoff Count Frequency CDF Exceedence_Probability
CFS % % %
0.001
0.003
0.005
0.006
0.008
0.010
0.012
0. 013
0.015
0.017
0.019
0.020
0.022
0.024
0.026
0.027
0.029
0.031
0.033
0.034
0.036
0.038
0.040
0.042
0.043
0.045
31998
6454
5579
5702
4287
2220
2550
1935
104
47
51
37
16
17
25
30
22
21
29
16
14
11
27
16
15
7
52.182
10.525
9.098
9.299
6. 991
3.620
4.159
3.156
0.170
0.077
0.083
0.060
0.026
0.028
0.041
0.049
0.036
0.034
0.047
0.026
0.023
0.018
0.044
0.026
0.024
0. 011
52.182
62.707
71.805
81.104
88.095
91. 716
95.874
99. 03 0
99.199
99.276
99.359
99.419
99.446
99.473
99.514
99.563
99.599
99.633
99.680
99.706
99.729
99.747
99.791
99.817
99.842
99.853
47.818
37.293
28.195
18. 896
11. 905
8.284
4.126
0.970
0.801
0.724
0.641
0.581
0.554
0.527
0.486
0.437
0.401
0.367
0.320
0 .294
0.271
0.253
0.209
0.183
0.158
0 .147
0.478E+OO
0.373E+OO
0.282E+OO
0.189E+OO
0 .119E+OO
0.828E-01
0 .413E-01
0.970E-02
0.801E-02
0. 724E-02
0.641E-02
0.581E-02
0.554E-02
0.527E-02
0.486E-02
0.437E-02
0.401E-02
0.367E-02
0.320E-02
0.294E-02
0.271E-02
0.253E-02
0.209E-02
0.183E-02
0.158E-02
0.147E-02
0.047 11 0.018 99. 871 0.129 0.129E-02
0. 049 7 0. 011 99.883 0 .117 0.117E-02
0.050 6 0.010 99.892 0.108 0.108E-02
0.052 9 0.015 99.907 0.093 0.930E-03
0.054 10 0.016 99. 923 0.077 0.766E-03
0.056 9 0.015 99.938 0.062 0.620E-03
0.057 4 0.007 99.945 0.055 0.554E-03
0.059 5 0.008 99.953 0.047 0.473E-03
0.061 9 0.015 99.967 0.033 0.326E-03
0.063 9 0.015 99.982 0.018 0.179E-03
Flow Duration from Time Series File:dsout_pond.tsf
Cutoff Count Frequency CDF Exceedence Probability
CFS % % %
0.001 28611 46.659 46.659 53. 341 0.533E+OO
0.003 9639 15. 719 62.378 37.622 0.376E+OO
0.005 5508 8.982 71. 360 28. 640 0.286E+OO
0.007 5841 9.525 80.886 19.114 0.191E+OO
0.009 4146 6.761 87.647 12.353 0.124E+OO
0.010 3067 5.002 92.648 7.352 0.735E-Ol
0.012 2283 3.723 96.371 3.629 0.363E-01
0.014 1373 2.239 98. 611 1. 389 0.139E-01
0.016 291 0.475 99.085 0.915 0.915E-02
0.018 91 0.148 99.234 0.766 0.766E-02
0.020 85 0 .139 99.372 0.628 0.628E-02
0.022 31 0.051 99.423 0.577 0.577E-02
0.024 24 0. 039 99.462 0.538 0.538E-02
0.025 19 0. 031 99. 4 93 0.507 0.507E-02
0.027 23 0.038 99.530 0 .470 0.470E-02
0.029 29 0.047 99.578 0.422 0.422E-02
0.031 21 0.034 99.612 0.388 0.388E-02
0.033 30 0. 049 99.661 0.339 0.339E-02
0.035 25 0. 041 99.702 0.298 0.298E-02
0.037 15 0.024 99.726 0. 274 0.274E-02
0.039 13 0. 021 99.747 0.253 0.253E-02
0.041 16 0.026 99.773 0.227 0.227E-02
0.042 34 0.055 99. 82 9 0.171 0.171E-02
0.044 6 0.010 99.839 0.161 0 .161E-02
0.046 8 0. 013 99.852 0.148 0.148E-02
0.048 11 0.018 99.870 0 .130 0.130E-02
0.050 8 0. 013 99.883 0 .117 0 .117E-02
0.052 6 0.010 99. 8 92 0.108 0.108E-02
0.054 9 0. 015 99.907 0.093 0.930E-03
0.056 10 0.016 99.923 0.077 0.766E-03
0.058 8 0. 013 99.936 0.064 0.636E-03
0.059 6 0.010 99.946 0.054 0.538E-03
0.061 7 0. 011 99.958 0.042 0.424E-03
0.063 9 0.015 99.972 0.028 0.277E-03
0.065 13 0.021 99.993 0.007 0.652E-04
0.067 2 0.003 99.997 0.003 0.326E-04
Discharge Volume
Discharge Volume from Time Series
rdout_pond.tsf
between 10/01/00 00:00 and 10/30/00 23:59
14850. Cu-Ft or 0.341 Ac-Ft in 30.0 days
in u._
8
V
"' ~
~
0 -~
Cl
10-
s) rdout. Pond pks in Sea-Tac
• dsout. Pond.pks
•
2
• •
(' 00
Return Period
5
R _____ _
•
•
10 20 50 100
•
10 <-->-----------------------------------------~-------------------
10-'--'---~------~ ----------,·
2 5 10 20 30 40 50 60 70 80 90 95 98 99
Cumulati\/e Probability
cii u..
£
<I)
e> m ,:;; u
1/J
c5
0
~
c::i
co
c::i
cg
c::i
y
c::i
(:,I
c::i
~
10' -5
+-
R ---.--
00
10 -4
:)
0-=--=---fi~.l
10 -3
rdout_Pond.dur
dsout_Pond.dur +
14040 Pre oc11
\
>,, C •c ,_ o---,, __ , ------>, t --'-. ,,.
10' -2 10 -1 10°
Probability Exceedence
Appendix D
Conveyance Calculations
To Be Provided at Final Engineering
GEOTECHNICAL ENGINEERING STUDY
PROPOSED WESTON HEIGHTS PLAT
684 & 650 NILE A VENUE NE
RENTON, WASHINGTON
G-2884-1
Prepared for
Mr. Justin Holland, Manager
Prospect Development, LLC
2913 -5th Avenue NE, Suite 201
Puyallup, WA 98372
July 3, 2014
GEO GROUP NORTHWEST, L"JC.
13240 NE 20th Street, Suite 10
Bellevue, Washington 98005
Phone: (425) 649-8757
Email: wchang@gcogroupnw.com or agaston@geogroupnw.com
JUL ?, 1 Zl11 11
, I
July 3, 2014
Mr. Justin Holland, Manager
Prospect Development, LLC
2913 -5th Avenue NE, Suite 201
Puyallup, WA 98372
SUBJECT: GEOTECHNICAL ENGINEERING STUDY
PROPOSED WESTON HEIGHTS PLAT
684 & 650 NILE A VENUE NE
RENTON, W ASIIlNGTON
Dear Mr. Holland:
G-2884-1
GEO Group Northwest, Inc., has prepared the following geotechnical report for the proposed
residential development based upon our previously completed subsurface investigation at the
site. This work was performed in accordance with our contract with you dated May 28, 2014.
GEO Group Northwest, Inc., explored subsurface soil conditions at the site by excavating four
exploratory test pits on October 30, 2012 and two test pits in May of 2009. Soils encountered at
the test pits consisted of loose to medium dense sandy SILT and silty SAND overlying dense to
very dense and gravelly silty SAND and gravelly sandy SILT with some cobbles at depths
ranging from 1.5 to 3.5 feet below ground surface (bgs).
Based on the results of our study, it is our professional opinion that the site is geotechnically
suitable for the proposed development. The proposed buildings can be supported on
conventional spread footings bearing on the dense native site soils or on compacted structural fill
placed on top of the dense native soils. The loose site soils and fills are not suitable to support
foundations due to their loose and variable condition. Based on the findings from our soil
investigation at the site, we anticipate that the dense soil under the building areas are present at
depths of approximately 2-feet below ground surface at the test pit locations. Some over-
excavation may be necessary at select locations but firm soil conditions are likely to be found at
the anticipated foundation depths. Please refer to the text of the report for more specific
recommendations regarding the site development.
We appreciate this opportunity to have been of service to you on this project. We look forward
to working with you as this proje<.'t progresses. Should you have any questions regarding this
report or need additional consultation, please feel free to call us.
13240 NE 20th Street. Suite 10 • Bellevue, Washington 98005
Phone 425/649-8757 • Fax 425/649-8758
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
Sincerely,
GEO Group Northwest, lnc.
William Chang, P.E.
Principal
I
GEO Group Northwest, Inc.
G-2884-1
Page ii
I •
TABLE OF CONTENTS
JOB NO. G-2884-l
Page
1.0 INTRODUCTION ...................................................... I
l. I Project Description ............................................... .
l .2 Scope of Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l
2.0 SITE CONDITIONS .................................................... 2
2. I Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.2 Geologic Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.3 Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.4 Soil Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.5 Groundwater Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.0 SEISMIC CONSIDERATIONS ........................................... 3
4.0 INFILTRATION EVALUATION ......................................... 3
5.0 CONCLUSIONS Al'l'D RECOMMENDATIONS ............................. 4
5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.2 Site Preparation and General Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2.1 Temporary Excavation and Slopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2.2 Structural Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5 .3 Spread Footing Foundations ......................................... 7
5.4 Permanent Basement and Conventional Retaining Walls ................... 8
5.5 Slab-on-Grade Floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.6 Footing Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. 7 Pavements ...................................................... 11
6.0 LIJ\,fiT ATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.0 ADDITIONAL SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
ILLUSTRATIONS
Plate l
Plate 2
Plate 3
APPENDIX A:
-Site Vicinity
. Site Plan
· Typical Footing Drain Detail
TEST PIT LOGS Al'l'D SOIL LEGEND
GEO Group Northwest, Inc.
GEOTECIL'IICAL ENGINEERING STt:DY
PROPOSED WESTON HEIGHTS PLAT
684 & 650 NILE A VE NE
RENTON, WASHINGTON
G-2884-l
1.0 INTRODUCTION
1.1 Project Description
The project site is located at the eastern side of Nile Ave NE at the subject address. Property tax
records indicate that the site has addresses of 684 and 650 Nile Ave NE with parcel numbers of
1123059092 and l 1230590 IO, respectively. Based upon our previous work at this site we
understand that the site also has an address of 12204 -148th Avenue SE. There is an existing
single family residence at the 684 address and a couple of storage buildings at the 650 address.
The existing buildings are shown on the attached Plate 2 · Site Plan.
The project site consists of a 4.54 acre parcel. We have been provided with a Site Plan for the
proposed development by Core Design which is dated June 17, 2014 and which has been
modified and included with this report as Plate 2 · Site Plan. According to the site plan the
development will consist of 14 new residential lots, a Open Space lot (Tract B) and two lots for
stormwatcr facilities (Tracts A and C). Based upon information provided by the owner and Core
Design we understand that wood-framed single family residences are planned for the western IO
lots at the site. Finish floor elevations for the new buildings were not provided at the time of this
study. A private access road is proposed to access the 10 new residences from Nile Avenue NE
(148th Ave SE). In addition a new road is proposed to access the new eastern lots and Tract C.
The majority of development is limited to the western portion of the property. The existing
house and accessory buildings will be demolished.
1.2 Scope of Services
The tasks we completed for this study were conducted in general accordance with the scope of
work presented in our contract dated May 28, 2014. The results of our subsurface investigation
and our recommendations regarding the proposed development are summarized in the following
report.
GEO Group Northwest, Inc.
July 3, 2014
Proposed Western Heights Plat, Renton, Washington
2.0 SITE CONDITIONS
2.1 Site Description
G-2884-1
Page 2
Based upon the site plan the site consists of a relatively flat 4.5 acre parcel occupied with one
single family residence and two accessory structures. The existing buildings and development
are located at the western side of the lot and the eastern side of the lot is undeveloped.
2.2 Geologic Overview
According to the geologic map for the site vicinity the soils at the site are reported to be Ground
Moraine Deposits (Qgt). The Ground Moraine soils typically consist of glacial till, a mixture of
sand, silt and gravel, which was consolidated by overriding glacial ice. These soils can usually
be divided into a surficial loose to medium dense weathered zone which overlies the dense to
very dense underlying un-weathered till soils.
2.3 Field Investigation
GEO Group Northwest, Inc., explored subsurface soil conditions at the site by excavating and
logging 6 exploratory test pits labeled TP-1 through TP-6. The test pits labeled TP-1 and TP-2
were excavated at the western portion of the site in 2009 in order to support a Pavement Design
by GEO Group Northwest. Test pits TP3 through TP-6 were excavated on October 30, 2012
specifically to provide data for a November 2008 geotechnical report. The test pits were located
near the proposed development areas, as shown on Plate 2 · Site Plan.
The test pits were excavated to depths ranging between 3 and 6 feet below ground surface (bgs ).
Soil samples at varying depths were collected, classified and returned to our laboratory. The test
pits were then backfilled with the excavated site soils. Backfilled soils were not compacted.
2.4 Soil Conditions
Soils encountered in the test pits consisted of primarily loose to medium dense sandy SILT
overlying dense to very dense gravelly sandy SILT and gravelly silty SAND with varying
amounts of cobble. The underlying dense to very dense soils appear to be the glacial till soils
GEO Group Northwest, Inc.
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
G-2884-l
Page J
which are noted on the geologic map. For the most part, the soils at the site appear to consist of
predominately SILT size particles. At a few locations and depths we visually estimate that the
predominate grain size is SAND followed closely by SILT. fn either case the soil, are
anticipated to exhibit relatively impermeable characteristics due to both their fine-grained texture
and underlying dense to very dense condition. [n general, the underlying competent dense soils
were encountered at depths ranging from l.5 to 3 .5 feet below ground surface.
Copies of the Test Pit Logs are presented in Appendix A: Test Pit Logs.
2.5 Groundwater Conditions
No groundwater seepage was encountered at the test pits. ft should be noted that groundwater
conditions may fluctuate seasonally, depending on rainfall, surface runoff and other factors.
3.0 Seismic Considerations
Based upon our subsurface investigation at the site, it is our opinion that the project buildings
may be designed using the Class C soil profile per the fntemational Building Code. It is our
opinion that the soils at the project site are not susceptible to liquefaction, due to the absence of
groundwater within the loose soil zone.
4.0 INFILTRATION EVALUATION
At the time of report preparation the site plan suggests that stormwater structures, such detention
or infiltration ponds may be proposed for Tracts A and C at the site. Consequently, we have
included this discussion regarding the potential for infiltration at the site.
Based upon our subsurface investigation the soils at the site consist predominately of sandy S [LT
and gravelly sandy SILT. Because they are fine-grained these soils are relatively impermeable.
Additionally, the underlying soil deposit is dense to very dense which further inhibits the
permeability of the ground. Of course the soils will allow for some infiltration under certain
conditions, however, the infiltration rate for these soils is generally low. We recommend that if
infiltration is used to treat site stormwater then overflow to an off-site stormwater system should
be part of the design, or the detention should be designed for the required storm water event.
GEO Group Northwest, Inc.
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
G-2884-l
Page 4
Alternatively, stonnwater treatment facilities such as dispersion trenches may be incorporated
which will allow for dispersion at times when rainfall exceeds capability of the system to provide
for infiltration.
5.0 CONCLUSIONS Al'1D RECOi\~IENDATIONS
5.1 General
Based upon the results of our study, it is our professional opinion that the site is geotechnically
suitable for the proposed development. The proposed buildings may be supported on
conventional spread footings bearing on the dense native site soils or on compacted structmal fill
placed on top of the dense native site soils. If a detention vault is planned then it should also be
constructed on top of the dense native soils or compacted structmal fills placed on top of the
dense native soils. The overlying loose site soils are not suitable to support foundations. We
anticipate that the dense soils are located at depths ranging from 1.5 feet to 3.5 below ground
surface (bgs) at the western portion of the site. At most of the test pit locations the dense soils
were encountered at or near standard shallow foundation depths of 1.5 to 2 feet bgs.
Consequently, we anticipate that over-excavation may be required only at select locations and
may be limited to the area near test pit TP-2. Based upon om understanding of the proposed site
plan new homes are currently proposed only for the western to-lots near Nile Ave NE. Our
subsurface investigation occurred at this area. If at some point houses are to be developed at the
eastern new lots (lots 11-14 ), we recommend that additional subsurface investigation be
completed for this area or that GEO Group Northwest, Inc., be on-site at the time of building pad
excavations in order to verify that new foundations are founded on the native dense soils and that
foundations are properly designed for the soil conditions.
It is also important to note that mapping of our test pits indicates that some test pits may have
been located at areas where proposed buildings or pavements are to be located. No compaction
was performed at the time that the test pits were backfilled. Therefore it is anticipated that the
fills at the test pit locations will be loose. We recommend that the contractor plan on over-
excavating and placing compacted structtual fill at any test pit locations which are located at
pavement or building locations such as TP-1, TP-2 and TP-5. GEO Group Northwest, Inc., can
be on-site at the time of grading and building pad preparation to aid in locating test pit locations
and overseeing the subgrade repair work.
GEO Group Northwest, Inc.
July 3. 20 l4
Proposed Weston Heights Plat, Renton, Washington
5.2 Site Preparation and General Earthwork
G-2884-1
Page 5
The building pad areas should be stripped and cleared of surface vegetation and forest duff soils.
Based upon the subsurface investigation topsoil/forest duff soils were encountered to depths of
up to 2-feet below ground surface. Silt fences should be installed around areas disturbed hy
construction activity to prevent sediment-laden surface runoff from being discharged off-site.
Exposed soils that are subject to erosion should be compacted and covered with plastic sheeting.
5.2.1 Temporary Excavation and Slopes
Under no circumstances should temporary excavation slopes be greater than the limits specified
in local, state and national government safety regulations. Temporary cuts greater than four feet
in height should be sloped at an inclination no steeper than IH: l V (Horizontal:Vertical) in the
loose site soils. Temporary cuts in the dense site soils may be excavated no steeper than IH:2V
provided that no seepage is encountered. [f groundwater seepage is encountered during
construction, excavation of cut slopes should be halted and the cut slopes should be re-evaluated
by GEO Group Northwest, Inc. If necessary the underlying very dense soils may be capable of
standing at steeper inclinations such as I H:JV, however, this is dependent upon the conditions at
the time of excavation. If it is necessary to form such steep excavation slopes than GEO Group
Northwest, lnc., must be retained to evaluate the conditions at the excavation at the time of
grading to provide an evaluation of stability. If the proposed temporary excavation slopes
encroach upon adjacent properties then it may be necessary to obtain an excavation easement or
plan for temporary shoring at those locations. Permanent cut and fill slopes at the site should be
inclined no steeper than 2H: IV.
Surface runoff should not be allowed to flow uncontrolled over the top of slopes into the
excavated area. During wet weather exposed cut slopes should be covered with plastic sheeting
during construction to minimize erosion.
5.2.2 Structural Fill
All fill material used to achieve design site elevations below the building areas and below non-
structurally supported slabs, parking lots, sidewalks, driveways, and patios, should meet the
GEO Group Northwest, Inc.
July 3. 2014
Proposed Weston Heights Plat. Renton. Washington
G-2884-1
Page 6
requirements for structural fill. During wet weather conditions, material to be used as structural
fill should have the following specifications:
l. Be free draining. granular material containing no more than five (5) percent fines (silt and
clay-size particles passing the No. 200 mesh sieve);
2. Be free of organic material and other deleterious substances, such as construction debris
and garbage;
3. Have a maximum size of three (3) inches in diameter.
All fill material should be placed at or near the optimum moisture content. The optimum
moisture content is the water content in soil that enables the soil to be compacted to the highest
dry density for a given compaction effort.
The majority of the surficial site soils will be moisture-sensitive because they consist of sandy
SILT and silty SAND soils. The site soils should be suitable for use as structural fill as long as
they are placed near their optimum moisture content. We anticipate that the site soils will most
likely be too wet to achieve the compaction requirements unless work is performed during the
dry summer months. Alternatively, an imported granular fill material may provide more
uniformity and be easier to compact to the required structural fill specification.
If the on-site soils are to be used as engineered structural fill, it will be necessary to segregate the
topsoil and any other organic-or debris-containing soil, because such soils would be unsuitable
for use as structural fill. Excavated on-site material that is stockpiled for later use as structural
fill should be protected from rainfall or contamination with unsuitable materials by covering it
with plastic sheeting until it is used.
Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness.
Structural fill under building areas (including foundation and slab area~). should be compacted to
at least 95 percent of the maximum dry density. as determined by ASTM Test Designation D-
1557-91 (Modified Proctor).
GEO Group Northwest, Inc.
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
G-2884-1
Page 7
Structural fill under driveways, parking lots and sidewalks should he compacted to at least 90
percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified
Proctor). Fill placed within 12-inches of finish grade should meet the 95% requirement.
We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of
structural fill material and to monitor the compaction work during construction for qua I ity
assurance of the earthwork.
5.3 Spread Footing Foundations
The proposed buildings can be supported on conventional spread footings bearing on the dense
native site soils or on compacted structural fill placed on top of the dense native site soils. Based
on the findings from our soil investigation at the site, we anticipate that the dense soils are
present between at between 1.5 and 3.5 feet below ground surface (bgs). Some over-excavation
and placement of structural fill may be required at foundation locations, dependent upon the
proposed finish grades and the conditions encountered at the building foundation excavations.
We recommend that GEO Group Northwest, Inc., be retained to verify competent soils are
present at each building foundation location, at the time of construction, prior to the foundation
pour(s).
Individual spread footings may be used for supporting columns and strip footings for hearing
walls. Our recommended minimum design criteria for foundations bearing on the dense site soils
or on compacted structural fill are as follows:
Allowable bearing pressure,
Dense native soil
Compacted structural fill
including all dead and live loads
= 2,500 psf
= 2,500 psf
Minimum depth to bottom of perimeter footing below adjacent final exterior grade = l 8
inches
Minimum depth to bottom of interior footings below top of floor slab = l 8 inches
Minimtun width of wall footings = l 6 inches
GEO Group Northwest. Inc.
July 3, 2014
Proposed Weston Heights Plat. Renton, Washington
Minimum lateral dimension of column footings = 24 inches
Estimated post-construction settlement= l/4 inch
G-2884-1
Page 8
Estimated post-construction differential settlement; across building width= 1/4 inch
A one-third increase in the above allowable bearing pressures can be used when considering
short-term transitory wind or seismic loads.
Lateral loads can also be resisted by friction between the foundation and the supporting
compacted fill subgrade or by passive earth pressure acting on the buried portions of the
foundations. For the latter, the foundations must be poured "neat" against the existing
undisturbed soil or be backfilled with a compacted fill meeting the requirements for stmctural
fill. Our recommended parameters are as follows:
-Passive Pressure (Lateral Resistance)
• 350 pcf equivalent fluid weight for compacted structural fill
• 350 pcf equivalent fluid weight for native dense soil.
-Coefficient of Friction (Friction Factor)
• 0.35 for compacted structural fill
• 0.35 for native dense soil
We recommend that footing drains be placed around all perimeter footings. More specific details
of perimeter foundation drains are provided below in Section 5.6 · Footing Drains.
5.4 Permanent Basement and Conventional Retaining Walls
At the time of report preparation finish grades for the proposed development were not shown on
the site plan. We anticipate that little site grading is proposed and that the new construction will
be primarily at-grade. The site plan does not indicate whether or not a detention vault of pond
will be located at the stormwater tracts A & C. The following design recommendations may be
used for permanent basement and conventional retaining walls at the project site, if necessary.
GEO Group Northwest, Inc.
July 3, 2014
Proposed Westlm Heights Plat, Renton, Washington
G-2884-1
Page 9
Permanent basement walls restrained horizontally on top are considered unyielding and should he
designed for a lateral soil pressure under the at-rest condition; while conventional reinforced
concrete walls free to rotate on top should be designed for an active lateral soil pressure.
Active Earth Pressure
Conventional reinforced concrete walls that are designed to yield an amount equal to 0.002 times
the wall height, should be designed to resist the lateral earth pressure imposed by an equivalent
fluid with a unit weight of 35 pcf for level backfill.
At-Rest Earth Pressure
Walls supported horizontally by floor slabs are considered unyielding and should be designed for
lateral soil pressure under the at-rest condition. The lateral soil pressure design shm1ld have an
equivalent fluid pressure of 45 pcf for level ground behind the walls.
Passive Earth Pressure and Base Friction
The available passive earth pressure that can be mobilized to resist lateral forces may be assumed
to be equal to 350 pcf equivalent fluid weight in both undisturbed soils and engineered structural
backfill.
The base friction that can be generated between concrete and undisturbed native soils or
engineered structural backfill may be based on an assumed 0.35 friction coefficient.
Drainage
Based upon the subsurface investigation no groundwater seepage was encountered at the test pit
locations which extended to depths of up to 6-feet below ground surface (bgs). If excavations
extend deeper than this, such a for detention vaults or full-height basement~ then seepage may be
encountered. If seepage is encountered then GEO Group Northwest, Inc., should be retained to
evaluate and provide updated recommendations for the un-anticipated conditions.
We recommend that a vertical drain mat, Miradrain 6000 or equivalent, be used to facilitate
drainage behind permanent concrete basement and conventional retaining walls. We recommend
GEO Group Northwest, Inc.
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
G-2884-I
Page IO
that the drainage mat be installed on the back side of the wall extending from the finish grade
down to a footing drain pipe. The wall footing drain pipe should consist of a 4-inch diameter
perforated rigid PVC pipe surrounded by a bed of washed gravel and separated from site soils by
filter fabric, Mirafi 140N or equivalent. The drain pipe should be tightlined to discharge to the
stormwater system. Backfill behind conventional retaining walls should consist of free-draining
sand or gravel soils which are compacted in lifts.
Backfill in areas adjacent to basement or conventional retaining walls should be compacted with
hand held equipment or a hoepack. Heavy compacting machines should not be allowed within a
horizontal distance to the wall equivalent to one half the wall height, unless the walls are
designed with the added surcharge.
5.5 Slab-on-Grade Concrete Floors
Loose site soils should be excavated from all concrete slab subgrade areas or compacted to a firm
and unyielding condition. Slab-on-grade concrete floors may be constructed on top of medium
dense to dense native site soils or on top of compacted structural fill placed on top of the
competent site soils. The slab-on-grade floors should not be constructed on top of loose soils.
To avoid moisture build-up on the subgrade, slab-on-grade floors should be placed on a capillary
break, which is in turn placed on the prepared subgrade. The capillary break should consist of a
minimum of a six (6) inch thick layer of free-draining crushed rock or gravel containing no more
than five (5) percent finer than the No. 4 sieve. A vapor barrier, such as a IO-mil plastic
membrane, is recommended to be placed over the capillary break beneath the slab to reduce
water vapor transmission through the slab. Two to four inches of sand may be placed over the
barrier membrane for protection during construction.
5.6 Footing Drains
We recommend that drains be installed around the perimeter of the foundation footings. The
drains should consist of a four (4) inch minimum diameter perforated rigid drain pipe laid at or
near the bottom of the footing with a gradient sufficient to generate flow, as schematically
illustrated in Plate 3 -Typical Footing Drain Detail. The drain line should be bedded on,
surrounded by, and covered with a free-draining rock, pea gravel, or other free-draining granular
material. The drain rock and drain line should be completely surrounded by a geotextile filter
GEO Group Northwest, Inc.
July 3, 2014
Proposed Westrm Heights Plat, Renton, Washington
G-2884-1
Page l l
fabric, Mirafi 140N or equivalent. Once the drains are installed, the excavation should he
backfilled with a compacted fill material. The footing drains should be tightlined to discharge to
the stormwatcr collection system.
Under no circumstances should roof downspout drain lines be connected to the footing drainage
system. All roof downspouts must be separately tightlined to discharge into the storm water
collection system. We recommend that sufficient cleanouts be installed at strategic locations to
allow for periodic maintenance of the footing drains and downspout tightline systems.
5.7 Pavements
Based upon the site plan we understand that new private access roadways will be constructed at
the site. The adequacy of pavements is strictly related to the condition of the underlying
subgrade. We recommend that all pavement subgrades be compacted by several passes of a large
vibratory drum roller prior to placement of the crushed rock base. Before paving, we recommend
that the subgrade be proof-rolled under the supervision of the geotechnical engineer to verify that
the subgrade is firm and unyielding at the time of paving. The proof-roll may be performed by
driving a fully loaded dump truck over the sub grade areas. If loose or yielding soils are
encountered it may be necessary to over-excavate and replace with compacted structural fill in
some areas. For firm and unyielding native subgrade soils we recommend the following
minimum pavement sections for driveways:
Class "B" Asphalt Concrete (AC)
Crushed Rock Base (3/4-inch minus)
Or
Concrete Pavement
Crushed Rock Base (3/4-inch minus)
3 inches
6 inches
6 inches
4 inches
We understand that it may be beneficial to install a base pavement layer such as ATB (Asphalt-
Treated Ba~e) prior to completion of the project. Oftentimes this can help protect the sub grade
from construction impacts and reduce cost related to subgrade repairs during wet weather
periods. Consequently we have calculated that the 3-inches of AC over 6-inches of Crushed
Rock Base noted above would be equivalent to the following total pavement thickness:
GEO Group Northwest, Inc.
July 3, 2014
Proposed Western Heights Plat, Renton, Washington
Class "B" Asphalt Concrete (AC)
Asphalt Treated Base (A TB)
Crushed Rock Base (3/4-inch minus)
2 inches
4 inches
3 inches
G-2884-l
Page 12
In accordance with the Washington State Department of Transportation Construction Manual,
transverse cracks will develop in concrete slabs at about 15 foot intervals along the length of
slabs and a slab wider than 15 feet may crack longitudinally. To control cracking of the concrete,
contraction joints should be installed. Contraction joints are weakened planes which collect the
cracking into a controlled joint, creating a maintainable joint in the slab, and preventing random
ragged cracks which spread and require expensive maintenance. We recommend that contraction
and construction joints be connected with #5 dowel bars, 30 inches long, 18 inches on center.
The contraction joints should be placed at maximum 14 foot intervals.
6.0 LIMITATIONS
This report ha~ been prepared for the specific application to this site for the exclusive use of
Prospect Development, LLC and their authorized representatives. We recommend that this
report be included in its entirety in the project contract documents for use by the contractor.
Our findings and recommendations stated herein are based on field observations, our experience
and judgement. The recommendations are our professional opinion derived in a manner
consistent with the level of care and skill ordinarily exercised by other members of the profession
currently practicing under similar conditions in this area and within the budget constraint. No
warranty is expressed or implied. In the event the soil conditions are found to vary during site
excavation, GEO Group Northwest, Inc. should be notified and the above recommendation
should be re-evaluated.
7.0 ADDITIONAL SERVICES
We recommend that GEO Group Northwest Inc. be retained to perform a general review of the
final design and specifications of the proposed development to verify that the earthwork and
foundation recommendations have been properly interpreted and implemented in the design and
in the construction documents. We also recommend that GEO Group Northwest Inc. be retained
GEO Group Northwest, Inc.
July 3, 2014
Proposed Weston Heights Plat, Renton, Washington
G-2884-1
Page 13
to provide monitoring and testing services for geotechnically-relatcd work during construction.
This is to observe compliance with the design concepts, specifications or recommendations and
to allow design changes in the event subsurface conditions differ from those anticipated prior to
the start of construction. We anticipate the following construction monitoring inspections may
be necessary:
I. Site clearing and grubbing;
2. Over-excavation and structural fill placement at building foundation locations;
3. Verification of bearing soil conditions for foundations;
4. Structural fill placement and compaction;
5. Slab-on-grade preparation;
6. Subsurface drainage installation;
7. Proof-rolling of pavement subgrade areas.
We appreciate this opportunity to have been of service to you on this project. We look forward
to working with you as this project progresses. Should you have any questions regarding this
report or need additional consultation, please feel free to call us.
Sincerely,
GEO Group Northwest, Inc.
(/~1Jnk
Adam Gaston
Project Engineer
cc: Bob Nix -Core Design
William Chang, P.E.
Principal
GEO Group Northwest, Inc.
ILLUSTRATIONS
G-2884-1
GEO Group Northwest, Inc.
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WESTON HEIGHTS PLAT
6S4 & 650 NILE A VE NE
RENTON, WASHINGTON
JOB NO.: G-2884-1 PLATE:
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SITE PLAN BASED UPON SHEET I
PROVIDED BY CORE DESIGN,
ruNE 17, 2014.
.IL ~ TEST PIT NUMBER AND
'-1"-rr-I APPROXIMATE LOCATION • Gro~F .. ~2E!,~~-~ Inc.
SITE PLAN
PROPOSED WESTO?,l HEIGHTS PLAT
6S4 & 650 Nil.E A VE NE
R.ENTON,WASHIN010N -~'1Ft.X~.'II -
--------
Ill
BACKFILL wrrn COMP,\CTEO
NATIVE SOIL
GEOTEXTILE FILTER FABRIC.
~HRAFI 140N OR EQUIVALENT
FREE DRAINING BACKFILL
CONSISTING OF WASHED
ROVND ROCK OR CRUSHED
ROCK
M!Nl~IIJM 4 INCH DIAMETER
PERFORATED PVC PIPE
LEVEL OR WITH POSITIVE
GRADIENT
TO DISCHARGE
NOTES:
i
ft" to 12"
FOOTING
111~11 II
NOT TO SCALE
I.) Do not replace rigid PVC pipe with flexible com1gated plastic pipe.
2.) Perforated or slotted PVC pipe should be tight jointed and laid with
perforations or slots down. with positive gradient to discharge.
3.) Do not connect roof downspout drains into the footing drain lines.
SLAB
• Group Northwest, Inc.
TYPICAL FOOTING DRAIN DETAIL
WESTON HEIGHTS PLAT
SCALE NONE DATE 712/14 MADE AG CHl<O WC
684 & 650 NILE A VE NE
RENTON, WASHINGTON
JOB NO. G-2884-1 PLATE 3
APPENDIX A:
TEST PIT LOGS
G-2884-1
LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST
UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) --r ---------------;· --------
,
MAJOR OJVIStoN ! GROUP
SYMBOL TYPICAL OESCA1PT10N LABORATORY CLASSIRCATIOH CRftERlA
•• T"' ------r· -. --·-·--ii ·-· -------------....
I CLEAN GW WELL GRADED GRAVELS. GRAVEL-SANO 'I Cu = {060 i DH)) 0~1e, 11'.an 4
GRAVELS ___ L_ Ml~~~lJffiEOR~~-NES···-----J PE;ET:: ... ~:OF :_ ~~'.~-'.lCr.2)11010"~)~ 1 m?J
GRAVELS I (irlt!e 0( no I GP POORL y GAAOEO GAAVEL'i, ANO GRAVEL-SAND·:; GRAVEL ANO SANO II NOT I.EETlNQ ABOVE REQUIREMl:Hrs
!Moo! Than Half hne11) i "41XTURES lJTTlf OR NO F!"tES · FROM GAAJN SIZE .
COARSE-~ BUTI .
GRAINED SC>LS ;
1
u~': 4 r-Gg::;LS ; GM -~Sl~TY GRA,ELS,~:V~L $~~LT :XTURES) DIS~RVE OO : =; ;_•:R~,l~::~~
! i (W!U'l 50'!'8 / GC ' CLAYEY GRAV~LS~:~EL-SANO-CLAY I COARSE GRAINED I exceeos ,r,.i ATTEABE~ ~:;~s ABOVE ·--·----·-.. ~~-+---------~-.. ------·------------------------l C~~,~~EAS ;:_ -------L ___ ~ P ~--~ETHA~_! __ -
S-'NOS j SW I WEU. GRADED SANOS. GRAV EU. Y SANOS, Lil TLE i FOUOWS. ! Cu .,, {060 I DlO) greater t!"lal1 15
: CLEAN i I OANOFINES ! Cc"(DJ0'1)t(010"060)oetwHnlal"ldl
~Tha,ittalfi,y[ (~~= \1 <'~
1
00 :-~; :--~LYG~~E~~~·:tF;~."~ I, <5%AMG-~---.:;~~:;,:,sov~:;~~ .... ~-
w~Latge, iSmalletThanNo.4, . 1 • GW,GP,SW.SP
"""'s,~,200 ! ~) lr-·--------+------r-
1
· ---------·----------!
1
. >l2%FheG~ ;---·Tl ATTEABE~·u,,.""'Ne BELOW
-~ DIRTY SM Sil TY SANOS. SANO-SILT MIXTlJRES : ,.,
i i SANDS I i ! GM, GC. SM. SC ' CONTENT OF ! -NITrl P.I LESS THAN 4
! I -: -----I ----·------------1 s 10 12'% Frne J Exe:;~ 12"". r-A. ITTRB€R0 LIMITS ABOVE
: {With som6 SC 1, CL.A VEY SANDS. SANO-CL.Av MtXTIJAES Grain«!: use dual L I 'A· LINE
, i fltlElll) : ! svrntx,11 ( ~ P I ,l,.ORE TkAN 7 ~------!----·--t-:;-ililimil ! ·------t-1 ;~NICSILT~.AOCK-~OUR,SANOV;fLfS f . . .
Sll TS i < 50% , ""-. OF SLIGHT PLASTICITY 60 ·1,
I P1atticify Ghan, i I I j ---' (Be!ow A-UN Oil L__J__ ____ L ---------1 PV.SnCnl' CHART / A·l.Jll'8 --/
ANE-GRAINED : NeQliglblie Organic); l,Qoid L;mii t MH ! INORO.ANIC SILTS. YICACEOi.JS OR FOR SotLPASSING r--+--1'--t--,,.-t--1 50
SOILS ' I > 50"4 : ! DIATOMACEOUS. FINE SANDY OR Sll TY SOIL NO. 40 SIEVE I I /
l i '"-----1~-----~---1---tlNOAGANICCU.vSOFLOWPLASTICITY ·1 I / CHorOH I CLAYS ! L..iQuid Lirnil I CL I GAAVELJ.Y. SAHOY. OA siuy cLAvs. cLEAN lJ -Ir--. /-l-r-i--t-1---J I <JO% . ' Cl/, '
i .:EJ ~ l.imjf lc:T1NOF10AN1c cws OF ::H PLASTICITY FA~ t-+-t-,-/lc.JL'-o,-OLt-~/1!---+--+-t-+-l--1
G:i 40
0 ;:;
JO ~
: I > 50% I ' CLAYS '
More Than Ha1H1~ t-· ~ --
WrtqYt Smalet I_ I L..quid limit I I ORGANIC Sll TS ANO ORGANIC Sil TY CLAYS cx:-
@ 20 ~
Q. I / ' "'"o, OH
Than No 200 /OAOA;~;~LTS 'L <.""-. I Ol J.____ LOW PLASTICITY I
SNNe (Below A·l.Jne on I I .. ----1----'
__ / P-.,c,,.,., j ';": I OH I 00GAN1CClAYS0FH10HPLASTIC1TV
1
" 7
4
0
/
I I I--pc, ML
0 10 20 JO 40 <J 60 70 "' 90 !00 110
HIGHL v ORGANIC SOILS I "' PEA r ANO OTI<ER HIGHI. v Of!GAN/G SOILS I LIQUID UMrT (%)
SOIL PAlfflCl.E SIZE
GEHERA.l. GUIDANCE OF SOI... ENOJNEERINQ PAOP£ATIE8 FROM STANDAAO PElfETFU.TIOH TEST(SPT)
,-----U.S. STAND.A.AD s,,ivE-----·-----l~-----------------~------------1
FRACTION I-P .... r,g j_' --1-------
I ' Sim I
.. [/ Sieve I (mm)-~. :'"-
sa. T I Cl.AV r.?00 : 0 075 , ----1-. L ----r~
I Slz9
I Jmm) -·1
r .. ---
I llAlfll I i I :~:w i :: ! fi:S I : I ::
~-COARSE ;_-~-_L .4 ~---i---~~-i _.,-2 __
W!4m [/ i I
1
1
FINE , 19 i •• -t 75
COARSE i, 715 / ! 19 o------·L ----'-----..L.·--~---·-__ _t_ ____ _
C080l.Ell
1----------·1-----
80ULDE.Ftl!I i
f-----·· -
AOCl( i
---------f---
i
76 ITWl'I ro 203 rrm
-
Blow
N
o-•
4-10
IO JO
> 50
I
I
S.AHOY SOfLS SIL TY I CLAYEY SOILS = 1 ':;' r.· ----_-_---··----=------1-,-"= 1 _ _.-
%. i ,t. Ol!lgl'N I N j Qu, Isl j -,~r---·-r-v..,~ ,, l-;-,-25-r·-;;·;; --·
15·35 I 28·Xl I llXlN Z·• 025-0.50 ! Sdt
35 66 28 -35 1 MIJdil.nl OenN 4 a 0.50 -1 oo I ~ Stiff
M·815 I 35 .Q i Denle 11·15 j 1.00-2.00 ;
8!5 · roo I! 38 ·.., I vi,,y DenM 1s ~ I 2.00. 4 oo ;
,,. JO :>-4.00 i
132'40 NE 2Cffi Stlwt, Suite fO
Phone (425) 649--8757
~.WA 98005
F.u {425) 6"9-3758 PLATE
51'1
A1
TEST PIT NO. TP-1
LOGGED BY AW TEST PIT DATE: 05/ l 5/2009 ..
DEPTH SAMPLE Water OTHER TESTS/
fl. uses SOIL DESCRIPTION No. % COMMENTS
ML Dk. Brown top~il. SILT. l(XlSC S-1 Probe 5-9" -~-------. -------------------------------------------------.
Bruwn .'>anJy S[L T with gravel, tine-grained, rnui:,1, loose to mc<lium S-2 Pn1bc4-l4" -' \!L
' ' dense S-3 Pnihe 0-J" -"·1-----· --------------------------------------------------·
-" SM
Gray gr..ivelly silty SAND with cobble, dense, becoming very dense at
5 -
3' bgs (unweathcred TILL)
. Total depth of test pit:;; 3.3 feet bgs
. No groundwater seepage observed
.
-
10 -
-
-
-
-
15 _
TEST PIT NO. TP-2
LOGGED BY AW TEST PIT DATE: 05/15/2009
DEPTH SAMPLE Water OTHER TESTS/
fl. uses SOIL DESCRIPTION No. % COMMENTS
----.1'.1!-. .... Drk. Brown Topsoil, SILT, very loose ________________________ Probe 30"
-ML Brown sandy SILT with some gravel, fine-grained, moist, loose
Probe 10" ----------------------------------------------------------Probe 2" -" SM Gray gravelly silty SAND wilh cobble, dense becoming very dense at
5 -4' bgs (unweathered TILL)
-
-Total depth of test pit= 4 feet bgs
No groundwater seepage observed -
-
10 -
-
-
.
-
15 _
TEST PIT LOGS
• WESTON HEIGHTS PLAT Grou~ Northwest, Inc. 684 & 650 Jlt'ILE A VE NE
GeolecMicaJ Engi'!&ers, Geologists, & RENTON, WASHL'iGTON Bwirorirrental Scientists
JOB NO. G-2884-1 DATE 7/2/14 PLATE A2 -·------~
TEST PIT NO. TP-3
LOGGED BY AG TEST PIT DATE: 11)/30120 12
-.
DEPTH SAMPLE Water OTHER TESTS/
n. uses SOIL DESCRIPTION No. 0, COMMENTS 0
~1L Dk. Rniwn ,;andy S[LT (t1)psoil), moist, l1)t)SC to medium den~ S-1 Prohe 3-6" ----------------------------------------------------------Pn>hc 2-J"
-.\IL CrJ:y g:rJvc!ly san<ly S(LT with oci.:asion.il cobhle, demc, hccoming S-2
Prnhc < l" -very Jense J.!ld cemented at J' hgs (unwealhered TILL)
-
5 -
Total depth of test pit = 6 feet bgs. -No groundwater 'iecpag:e obsen:e<l
-
-
10 -
-
-
-
-
15 -
TEST PIT NO. TP-4
LOGGED BY AG TEST PrT DATE: I 0130/2012 -~---------·------
DEPTH SAMPLE Water OTHER TESTS/
n. uses SOIL DESCRIPTION No. % COMMENTS
ML Drk. Brown sandy SILT (topsoil-forest <luff). moist. very loose to Probe 12-l8'' -medium dense S-I
---------~--------------------------------------------------Probe 1-3"
S-2 -ML Tan and mottle<l sandy SILT wich occasional gravel and cobbles, Probe <I'' -dense becoming very dense at 3.5' hgs (unweathered TILL)
5
-Total depth of test pit= 5 feet bgs
-No groundwater seepage observed
-
-
10 _
-
-
-
-
15 -
TEST PIT LOGS
• WF.~TON HEIGHTS PL,\ T Group Northwest, Inc. 684 & 65-0 NILE A VE :,;i,:
G&otect'-,rncal 8,,gi'leers. Geologists. & RE.'liTON, WASHLNGTON
8"1V,rontr8ntal Sc113111:1Sts
JOB NO. G-2884-1 DATE 7/2/14 PLATE A3
. ----·--------·--~--
TEST PIT NO. TP-5
LOGGED BY AG TEST PIT DATE: I 0/30/2012 ·~· ---... _ .. ------·-·· .
DEPTH SAMPLE Water OTHER TESTS/
ft. uses SOIL DESCRIPTION No. % COMMENTS
\IU Dk. Brown silty SAND/sandy SILT (cop54.,il). moi.st. loose to medium Pn>he 18-24" -SM dense
----------------------------------------------------------S-1 Pwbe <I ..
ML Tan grc1velly sandy S[L T with occasional cobbles., r~mcnted. moist, -, dense to very dense (unweathercd TlLL)
.
5 Total depth of test pit = 3 feet hgs -No groundwater seepage observed -
-
-
-
10 _
-
-
-
.
15 -
TEST PIT NO. TP-6
LOGGED BY AG TEST PIT DATE: l0/30/2012
DEPTH SAMPLE Water OTHER TESTS/
ft. uses SOIL DESCRIPTION No. % COMMENTS
ML Ork. Brown to red-brown silty SAND/sandy SlL T with some gravel and Probe 4-IO" -occasional cobble, moist, loose to medium dense
--------· ~--------------------------------------------------S-1 Probe 2"
-SM Brown to tan and then gray gravelly silty SAND. dry, dense to very S-2 dense, cemented (unweathered TILL)
5 Total depth of test pit = 4 feet bgs -
-No groundwater .seepage observed
-
-
-
10 _
-
-
-
-
15 -
TEST PIT LOGS
• WESTON HEIGHTS PLAT Group Northwest, Inc. 684 & 650 NILE A VE NE
Geotechncal &ig.,eers, Geoi:>gists, & RENTON, WASHINGTON &lvironmental Scl8n~ts
JOB NO. G-2884-1 DATE 7/2/14 PLATE A4 ------------