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ci��il engineers•land planners
STORM DRAINAGE AND
EROSION CONTROL REPORT
F � R
THE BORGATA APARTMENT
�.
HOMES
SEPTEMBER 1 ��9
REVISED FEBRUARY ZOOO ,
.., �A,�`��.__,��,ti I
� PREPARED FOR: R�����'��
SEB, I1�C. FEB 2 1 2000 �
240 STADIUM WAY SOUTH g�J;�n�NG D11�i�lON '
T�coMl�, WA 98402
(253) 428-0800 '
� PREPARED BY:
TIMOTHY D, HOLDERMAN, P.E., PRINCIPAL ,
SOUND ENGINEERING, INC. II'�,
1019 P�CIFIC AvENUE, SUITE 906 ��,
T��co:��, WA 98402 '
(253) 573-0040
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STORM DRAINAGE AND
EROSION CONTROL REPORT
� FOR '
The Borgata Apartment Homes
Renton, Washington
September 1999
Revised February 2000
Prepared for: ;�.t D• NO�Q ,
�O�� oF W � F�` ;�
e. ��, , ,:� �`,�?r ,�
Steve Berg and Eric Blitz F�r1``•,� r'• z
SEB, Inc. - / �
240 Stadium Way South A ��748 �
Tacoma, WA 98402 � Rfrf���'� ���'�
��S�ONAL EN��,
IXr"IRES 1�/23/Qr
Prepared by:
Timothy D. Holderman, P.E., Principal
- REPORT #99121.10
This analysis is based on data and records either supplied to, or obtained by, Sound Engineering, I
Inc. These documents are referenced within the text of the analysis. This analysis has been
prepared utilizing procedures and practices within the standard accepted practices of the industry.
SOUND ENGINEERING, Il�'C.
'�1:;991211STORM REPORT.02.09.00.doc
TABLE OF CONTENTS
PAGE
1.0 PROJECT OVERVIEW.......................................................................................................................1
l.l PURPOSE AND SCOPE.....................................................................................................................1 II
1.2 PREDEVELOPEDCOND[TIONS........................................................................................................1
�
1.3 POST-DEVELOPMENT CONDITIONS...............................................................................................2
2.0 PRELIMINARY CONDITIONS............................................................................................................2
3.0 OFF-SITE ANALYSIS.........................................................................................................................3
4.0 FLOW CONTROL& WATER QUALITY FACILII'Y ANALYSIS AND DESIGN...................................3 ',
4.1 EXISTING SI"i'E HYDROLOGY.........................................................................................................3 I�
4.2 DEVELOPED SITE HYDROLOGY.........................................................••••........................................4 I
4.3 PERFOR;�tANCE STANDARDS..........................................................................................................4 '
4.4 FLOW CONTROL SYSTEM ..............................................................................................................4
4.5 WATER QUAI.ITY SYSTE�t......................................................................................•••••..................5
�.0 CO�iVEYANCE SYSTE�i ANALYSIS AND DESIGN............................................................................5
6.0 SPECIAL REPORTS AND STUDIES....................................................................................................5
7.0 BASL�1 AND COhIMUNI'I'1'PLANNING AREAS..................................................................................�
8.0 OTFIER PER'�tITS..............................................................................................................................�
9.0 TESC ANALYSIS AND DESIG�1........................................................................................................6
9.1 UVTRODUCTION....................................................••••••••••................................................................6
9.2 DESIGN CONSIDERATIONS.....................................•••...•••...............................................................6
9.3 DES[GN..........................................................................................................................................7
' 10.0 BOTiD QtiAtiTITIES,F:�CILITY SL�1'IMARIES AND DECLARr1TION OF COVENANT........................7
10.1 BOtVD QUANTITY SHEETS..............................................................................................................7
10.2 FLOW CONTROL r��ID WATER QUAL.ITY FACILITY SUMMARY SHEET AND SKETCH.....................7
103 DECLARAT[ON OF COVENANT.............................•••••...................................................................._8 i
11.0 1�I�►INTENANCE AND OPERATIONS MANUAL..................................................................................8 I
AppendixA Vicinity Map A-1
USDA Soil Map A-2
USDA Soil Description A-3
USGS Topob aphic Map A-4 '
Appendix B Geotechnical Report B-1 I
Appendix C Basin Summary G1 ,
CN Calculations C-3 !,
Runoff Curve Numbers C-4
Basin Map GS
M:1991211STORM REPORT.02.09.00.doc
r�ppe�zdix C (Contint�ec�i
Isopluvial Charts C-7
Correction Factor to Pond Volume C-]0
Detention Pond Sizing C-1 1
Bioswale Sizing G 1�
Equivalent Area Calculations C-1��
Capacity Calculations C-1 l
, Sediment Pond Sizing Calculations C-1��
Appendix D Maintenance and Operations Manual D-l
Retention/Detention Summarv Sheet D-ll)
I��cl�ir:i[i��n ;�f C�����n,int D-1�
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M:199121\STORM REPORT.02.09.00.doc
1.O PROJECT OVERVIEW
1.1 Purpose and Scope
This report accompanies the Preliminary Grading and Storm Drainage Plan for the
proposed project as submitted to City of Renton. This document provides site
information and the analysis used for the preliminary storm drainage design.
The City of Renton Municipal Code, Section 4-6-030, the King County Surface Water
Design Manual, January 1990 have partially established the methodology and design
criteria used for this project. Because the project will require an HPA permit, the
Department of Ecology Stormwater�'Llanagement ll�lanual for the Puget Sound Basin has
been utilized for water quality treatment and stormwater detention sizing.
1.2 Predeveloped Conditions
The existing site consists of a rectangular parcel totaling approximately 8.12± acres. The
site is located east of Talbott Road South just north of S. SSth Street, within the City of
Renton. (See Appendix `A' for Vicinity Map.). From the proposed developed eastern
portion of the propeny, the site slopes to the west at approximately 15%. A single-family
house currently located on the lower northwest portion of the site. Short grass, brush,
scattered conifer trees, and a couple of small out buildings make up existing ground cover
on the site. -
The existing site consists of a rectangular parcel totaling approximately 8.12± acres. The '
site is located east of Talbott Road South just north of S. SSth Street, within the City of
Renton (See Appendix `A' for Vicinity Map). From the proposed developed eastern �'
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portion of the property, the site slopes to the west at approximately 15°l0. A single-family
house cunently located on the lower northwest portion of the site. Short grass, brush,
scattered conifer trees, and a couple of small out buildings make up existing ground cover
on the site.
1.3 Post-Development Conditions . ��`�%
�I•
The proposed project consists of the construction of 82 apartment units, parking,
landscaping, recreational building and access roads. Approximately 5.16± acres of the
overall site will be disturbed. Approximately 2.96± acres of the easterly portion will
remain undisturbed due to steep slopes. An additional 0.75± acres will remain as buffers
for a Type IV stream located within the undisturbed central portion of the site. There are
two proposed paved accesses that will connect to Talbott Road South at the western edge
of the site. Earthwork volumes are estimated in the 9,000 cubic yard range. The intent of
the final grading plan will result in a balanced site. It is anticipated that unsuitable soils
encountered durin� construction will be removed from the site. Site �rading will consist
of cutting pads for the proposed buildings as well as parking and access road
construction. Stormwater runoff from the buildings, traveled areas and landscaping will
be routed through an underground detention vault and thru a 14' biofiltration swale
located adjacent to Talbott Road South.
2.O PRE�IMiNARY CONDITIONS
The conditions and requirements for the parcel have yet to be determined. This parcel
falls within its intended zoning (R-14) and does not require any rezoning approval.
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3.0 OFF-SITE ANALYSIS
The project basin flows west to Talbott Road South where storm water from the site will
be discharged via controlled release to the existing storm drainage system located within ',
Talbott Road South. This storm system crosses under Talbott Road South and flows west
to where it discharges to a Type N stream. Due to downstream drainage problems, the
city has required that the proposed storm drainage detention system be designed to detain
the 2, 10 and 100 post-developed storm events. The proposed detention system goes one
step further by restrictin�the pre-developed runoff rates to 50% of the 2-year, 10-year and
100-year storm events. Consequently, post-developed runoffs will not exceed pre-
developed flows up to the 100-year storm event.
� This off-site basin delineation was based on a site visit and a field survey. In addition, the ,
USGS Map for this portion of King County was reviewed, and confirms the basin
boundary.
4.O FLOW CONTROL 8c WATER QUALITY FACILITY ANALYSIS AND DESIGN
4.1 Existing Site Hydrology
T'he 8.12-acre parcel is positioned along the easterly ridgeline. The soils consist of an I
Alderwood soils according to the USDA Soil Conservation Service soils survey of King
I �_ County. In addition, a geotechnical consultant also confirmed the soil type and
' characteristics. In May of 1999, twelve (12) test pits were excavated by Geotech
i
a �
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.,f.,,..,,.,r;.,., ,.1 \„ ,,1;•- �T2• .- th.� r.,,�r., l, A.�.-.
proposed roof drains will be directed through a separate conveyance line that will flow to
the 18" culvert within Talbott Road South, which then flows to the wetlands area to the
west. The remaining 4.41 acres of developed site will be detained and released to a water
quality treatment swale. A total of .44 acres of the site will be landscaped. The
combined CN number for the developed 4.41 acres has been calculated to be 68. Please
see Appendix `C' for additional area breakdown information.
4.3 Performance Standards
Not applicable at this time.
4.4 Flow Control System
The detention system was sized to detain the 2, 10, and 100 post-developed storm events
and release at the pre-developed runoff rates equivalent to 50% of the 2 year, 10 year, and
100-year storm events with a correction factor of 1.37 has been utilized as required by the
DOE design manual. Hydraulic calculations were performed utilizing the Santa Barbaza
Unit Hydrograph Method per City of Renton guidelines. The computer program
�
4
��nenc�i�c `C' �f th�
�1.� 1�ater lluality 5ystem
Water quality will be addressed by providing a 12' wide biofiltration swale designed per
a
1990 King County Surface Water Standards. �°� �
5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN
r�li lnc; >lUrItlW�llt;r iiOtIl tilc: �rU�JWc:IL Uulllllil�'� �lIl�l a��ti�til ar�u� '���lil Dc: �:iuliVC��c:ll U� ..
tightlined conveyance system to the under�
/ .0 i7HJ1iV i-11VU liUlYl�rIUIVI! T i�L/�(VIVIIVIa HtiCHJ
Not Applicable.
8.0 OTHER PERMITS
HPA Permit and wetland approval.
! .
5
9.O TESC ANALYSIS AND DESIGN
9.1 Introduction
The following discussion is provided to address general erosion control measures for site
preparation.
9.2 Design Considerations
The proposed �rading of the site, as well as the construction of the items listed below,
will mitigate against any major diversion of storm water runoff by maintaining natural
draina�e patterns. The structural components of the erosion control plan will work in
combination with temporary and permanent soil stabilization effor[s to minimize the level
of sediment-laden runoff from leaving the site and enterina the downstream environment.
l�feasures taken to control sediment:
■ A planned construction sequence designed to provide for construction of erosion
control features.
■ Quarry spall construction entrance to mitigate the introduction of sediment into
any off-site storm facilities or adjacent public roadway facilities.
■ Timely stabilization of exposed soils to prevent erosion.
■ Temporary siltation fences as needed.
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9.3 Design
A quarry spall construction entrance onto Talbott Road South will be provided. Silt
fences will be utilized to control runoff velocities and sedimentation at appropriate
locations.
The creation of airborne dust during construction will also need to be controlled by the
contractor. This can be accomplished through the use of watering trucks during
construction.
All of the features contained within the TESCP, if installed and periodically maintained,
are expected to minimize the level of sediment-laden runoff entering any of the public
road right-of-ways and adjacent properties.
1 O.O BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION OF
COVENANT
10.1 Bond Quantity Sheets
Not applicable at this time.
10.2 Flow Control and Water Quality Facility Summary Sheet and Sketch �
A Retention/Detention Summary Sheet has been included in Appendix `D'.
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7
10.3 Dectaration of Covenant Il
Not applicable at this time. A completed Declaration of Covenant form has been
included in Appendix `D' of this repoR for future use.
11.0 MAINTENANCE AND OPERATIONS MANUAL
A Maintenance and Operations Manual is included in Appendix `D' of this report.
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APPENDIX A
VicinityMap......................................................................................................A-1
USDASoil Map.................................................................................................A-2
USDASoil Description.....................................................................................A-3
USGSTopographic Map ...................................................................................A-4
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OIIND Tacoma.WA 98402 The Borgata Apartment Homes
Bus: (253) 573-0040
NGINEERING, Inc. Fax: f2531 sr,�-o�as
USDA Soil Conservation Services Soil Description
CIVII ENGINEERS'LANO PUNNERS sound�soundenginc.com
Alderwood gravelly sandy loam,6 to 15 percent slopes (AgC)
This soil is rolling. Areas are irregular in shape and range from t0 to about 600 acres in size.
The A horizon ranges from very dark brown to dark brown. The B horizon is dark brown, grayish brown,
and dark yellowish brown. The consolidated C horizon, at a depth of 24 to 40 inches, is mostly grayish
brown mottled with yellowish brown. Some layers in the C horizon slake in water. In a few areas, there is a
thin, gray or grayish-brown A2 horizon. In most areas, this horizon has been destroyed through log�ing
operations.
Soils included with this soil in mapping make up no more than 30 percent of the total acreage. Some areas
are up to 3 percent poorly drained Norma, Bellingham, Seattle, Tukwila, and Shalcar soils; some are up to 5
percent the very gravelly Everett and Neilton Soils; and some are up to 15 percent Alderwood soils that
have slopes more gentle or steeper than 6 to 15 percent. Some areas in Newcastle Hills are 25 percent
Beausite soils, some nonheast of Duvall are as much as 25 percent Ovall soils, and some in the vicinity of
Dash Point are 10 percent Indianola and Kitsap soils. Also included are small areas of Alderwood soils that
have a gravelly loam surface layer and subsoil.
Permeability is moderately rapid in the surface layer and s�bsoil and very slow in the substratum. Roots
penetrate easily to the consolidated substratum where they tend to mat on the surface. Some roots enter the
substratum through cracks. Water moves on top of the substratum in winter. Available water capacity is
low. Runoff is slow to medium, and the hazard of erosion is moderate.
This soil is used for timber,pasture,berries,row crops, and urban development. Capability unit Ive-2;
woodland group 3d1.
Alderwood gravelly sandy loam, l�to 30 percent slopes(AgD)
Depth to the substratum in this soil varies within shoR distances, but is commonly about 40 inches. Areas
are elongated and range from 7 to 250 acres in size.
Soils included with this soi�in mapping make up no more than 30 percent if the total acreage. Some areas
are up to 25 percent Everett soils that have slopes of 15 to 30 percent, and some areas are up to 2 percent
Bellingham,Norma, and Seattle soils, which are in depressions. Some areas, especially on Squak Mountain,
in Newcastle Hills, and north if Tiger Mountain, are 25 percent Beausite and Ovall soils. Beausite soils are
underlain by sandstone, and Ovall soils by andesite.
Runoff is medium, and the erosion hazard is severe.The slippage potential is moderate.
This Alderwood soil is used for timber. Some areas on the lower parts of slopes are used for pasture.
Capability unit VIe-2; woodland group 3d1.
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Geotechnical IZeport..........................................................................................I3-1
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GEOTECHNICAL ENGINEERING STUDY
Proposed Multi-Family Devetopment
186xx Talbot Road South
King County� Washington
This report p�esents the findings and recommendations of our geotechnical engineering study for
the site of the proposed multi-family development in King County. The Vcinity Map, Plate 1,
illustrates the general location of the site.
We were provided with a faxed site plan showing lot lines and the location of the existing house in
the northwest corne� of the site. We anticipate that the property will be developed with apartment
buildings and that the existing house will be removed or demolished. Detailed plans showing the
proposed building locations, existing topography, and final site grading were not available at the
time of this report.
SITE CONDITIONS
Surface
The nearly rectangular tract covers 8.3 acres on the east side of Talbot Road South in King
County. It has approximately 375 feet of street frontage and an average depth of about 930 feet.
The ground surface slopes gently upward to the east for most of the property length. The eastern
100 to 200 feet of the property slopes steeply upward to the east property line. In addition to the
existing house located in the northwest corner of the property (18624 Talbot Road South), several
concrete structures including a barn, a bathhouse, two pump houses, and possibly a filled-in
swimming pool occupy the site. A concrete and rock basement foundation was faund near the
middle of the site. Except for the area around the existing house, the property is wooded and
overgrown.
' Nearby development consists of the Summit Park Condominiums immediately south of the site,
and several houses located to the no�th and east.
Subsurface
The subsurface conditions were explored by excavating 12 test pits at the approximate locations
shown on the Site Exploration Plan, Plate 2. The test pits were excavated on May 14, 1999 with a
track-mounted excavator. A geotechnical engineer from our staff observed the excavation p�ocess,
logged the test pits, and obtained representative samples of the soil encountered. "Grab" samples
of selected subsurface soil were collected from the trackhoe bucket. The Test Pit Logs are
attached to this report as Plates 3 through 8.
In the southeastern portion of the site, Test Pit 4 encountered about 1 foot of topsoil, and 3.5 feet
of gravelly, silty sand overlying stiff, fractured silt. The silt is underlain by dense, slightiy silty sand I
extending to an explored depth of 10 feet. Elsewhere, beneath 1 to 1.5 feet of forest duff and
topsoil, the native soils consist of inedium-dense, weathered, silty sand with gravel, which became
gray and very dense with depth. The very dense silty sands have been glacially consolidated and I
GEOTECH CONSULTANTS,INC. �—1
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are �efer�ed to in this report as glacial till. In our explorations, the dense to very dense glacial till
was encounte�ed to a maximum explored depth of 12 feet below the existing surface grade.
Based on our observations, the portions of the site have likely undergone grading associated with
the existing and previous structures. Therefore, some fill and demolitions debris may be
encountered. Fill will likely be found in the area of the old swimming pool.
The final logs represent our interp�etations of the field logs and laboratory tests. The stratification
lines on the logs represent the app�oximate boundaries between soil types at the explo�ation
locations. The actual transition between soil types may be gradual, and subsurface conditions can
vary between exploration locations. The logs provide specific subsurface information only at the
locations tested. The relative densities and moisture descriptions indicated on the test pit logs are
interpretive descriptions based on the conditions observed during excavation.
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problern, the backfill will need to be removed and
replaced with structu�al fill during construction.
Groundwater
Groundwater seepage was observed at a depth of about 6 feet in Test Pits 7 and 9.
Surface water was observed flowing in several small ditches that traverse the site east to
west. Water could be heard flowing into and out of a cistern located underneath one of the
concrete pump houses. The test pits were left open for only a short time period. Therefore,
the seepage levels on the logs represent the location of transient water seepage and may
not indicate the static groundwater level. It should be noted that groundwater levels vary
seasonally with rainfall and other factors. We anticipate that groundwater could be found
near the contact between the weathered upper soils and the underlying glacial till.
CONCLUSIONS AND RECOMMENDATIONS
General
Based on the results of the test pits and the observations made during our site visit, it is our opinion
that the proposed multi-family development is feasible from a geotechnical engineering standpoint.
The proposed buildings may be supported on conventional foundations bearing on the medium-
dense to very dense, na�ive soils.
A significant geotechnical consideration for development of this site is the overly moist to wet
condition of some of the soils. Based on our observations, and the results of our laboratory tests,
the moisture contents of the on-site soils varied from near optimum to as much as 5 to 10 percent
above optimum. The fine-grained, soils are sensitive to moisture, which makes them impossible to
adequately compact when they have moisture contents more than 2 to 3 percent above their
optimum moisture content. The reuse of the overly-moist soils as structural fill to level the site will
only be successful during hot, dry weather. Aeration or chemical treatment of each loose lift of soil
will be required to dry it before the lift is compacted. This drying will slow the earthwork process.
The earthwork contractor must be prepared to rework areas that do not achieve proper compaction
due to high moisture content. Utility trench bacfcfill in structural areas, such as pavements, must
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also be dried before it can be adequately compacted. Imprope� compaction of backfili in utility -
trenches and a�ound control structures is a common reason for pavement distress and failures.
Imported granular fill will be needed wherever it is not possible to dry the on-site soils su�ciently
befo�e compaction, o� if wet weather earthwork is attempted.
Depending on the depth of cuts necessary fo� site g�ading, seepage may be encountered. This is
most likely to occur following extended wet weathe�. Temporary dewatering can consist of
installing sumps o� rock-lined ditches that are either pumped o� that outfall by gravity. Subsurface
interceptor drains will be needed immediately upslope of permanent cuts that expose significant
seepage. These drains would consist of gravel-filled trenches excavated at least 12 inches into
dense glacial till. A non-woven filter fabric should be draped into the trench before backfilling with
gravel. A 4-inch-diameter perforated PVC pipe should be placed approximately 6 inches above the
bottom of the trench, with the pipe being sloped to a suitable discharge.
Well-constructed footing drains, free-draining wall backfill, and waterproofing are needed to prevent
seepage through below-grade walls. Underslab drains should be installed where building
excavations encounter heavy seepage.
Surface drainage features have been constructed on the site in the past. The grading and
drainage plan will need to include provisions for surface runoff entering the site.
The erosion control measures needed during the site development will depend heavily on the
weather conditions that are encountered. The erosion potential on the site is relatively low due to ,
the gentle slope of the ground, however, site cfearing will expose a large area of bare soil. We
anticipate that a silt fence will be needed around the downslope side of any cleared areas. Rocked
construction access roads should be extended into the site to reduce the amount of mud carried off
the property by trucfcs and equipment. Following rough grading, it may be necessary to mulch or
hydroseed bare areas that will not be immediately covered with landscaping or an impervious
surface.
Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may incfude
revisions to our recommendations to accommodate site, development, and geotechnical
constraints that become more evident during the review process.
Conventional Foundatians
The proposed structures can be supported on conventional continuous and spread footings bearing
on undisturbed, medium-dense to dense, native soil, or on structural fill placed above this
competent, soil. See the later sub-section entitled General Earthwork and Structural Fill for
recommendations regarding the placement and compaction of structural fill beneath structures.
Adequate compaction of structural fill should be verified with frequent density testing during fill
placement. We recommend that continuous and individual spread footings have minimum widths
of 12 and 16 inches, respectively. They should be bottomed at least 18 inches below the lowest
adjacent finish ground surface. The local building codes should be reviewed to determine if
different footing widths or embedment depths are required. Footing subgrades must be cleaned of
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loose or disturbed soil prior to pouring concrete. Depending upon site and equipment constraints,
this may require removing the disturbed soil by hand.
Depending on the final site grades, some overexcavation may be required below the footings to
expose competent, native soil. Unless lean concrete is used to fill an overexcavated hole, the
overexcavation must be at least as wide at the bottom as the sum of the depth of the
ove�excavation and the footing width. For example, an overexcavation extending 2 feet below the
bottom of a 3-foot-wide footing must be at least 5 feet wide at the base of the excavation. If lean
concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing.
An allowable bearing pressu�e of 2,500 pounds per square foot (psfl is appropriate for footings
supported on competent, native soil or properly-compacted structural fill. A one-third increase in
this design bearing pressure may be used when considering sho�t-term wind or seismic loads. For
the above design criteria, it is anticipated that the total post-construction settlement of footings
founded on competent, native soil, or on structural fill up to 5 feet in thickness, will be less than one
inch, with differential settlements on the order of one-haff inch in a distance of 50 feet along a
continuous footing with a uniform load.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the
foundation. For the latte� condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level structural fill. We recommend using the following
design values fo� the foundation's resistance to lateral loading:
Parameter Design Value _
Coefficient of Friction 0.40
Passive Earth Pressure 300 pcf
Where:(i)pcf is pounds per cubic foot,and(ii)passive earth
pressure is computed using the equivalent fluid density.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
not be appropriate. We recommend a safety factor of at least 1.5 for the foundation's resistance to
lateral loading, when using the above design values.
Seismic Considerations
The site is located within Seismic Zone 3, as iflustrated on Figure No. 16-2 of the 1997 Uniform
Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the soil profile within a
depth of 100 feet is best represented by Soil Profile Type S� (very dense soil). The site soils are
not susceptible to seismic liquefaction because of their dense nature.
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Slabs-on-Grade
The building floo�s may be constructed as slabs-on-g�ade atop firm, stable, native soil or an
stcuctural fill. The subgrade soil must be in a firm, non-yielding condition at the time of slab
constn.rction or underslab fill placement. Any soft areas encountered should be excavated and
replaced with select, impo�ted structural fill.
All slabs-on-grade should be underlain by a capillary break or drainage layer consisting of a
minimum 4-inch thickness of coarse, free-draining structural fill with a gradation similar to that
discussed later in Permanent Foundation and Retaininq Walls. In areas where the passage of
moisture through the slab is undesirable, a vapor barrier, such as a 6-mil plastic membrane, should
be placed beneath the slab. Additionally, sand should be used in the fine-grading process to
reduce damage to the vapor barrier, to provide uniform support under the slab, and to reduce
shrinkage cracicing by improving the concrete curing process.
Permanent Foundation and Retaining Wa_I_Is
Retaining walls backfilled on only one side should be designed to resist the laterai earth pressures
imposed by the soil they retain. The following recommended design parameters are for walls that
restrain level backfill:
Parameter Design Value
Active Earth Pressure " 35 pcf
' Passive Earth Pressure 300 pcf
Coe�cient of Friction 0.40
Soil Unit Weight 130 pcf
Where:(i) pcf is pounds per cubic foot,and(ii)active and passive
earth pressures are computed using the equivalent fluid
pressures.
' For a restrained wall that cannot deflect at least 0.002 tlmes its
height,a uniform lateral pressure equal to 10 pst times the height
of the wall should be added to the above active equivalent fluid
pressure.
The values given above are to be used to design permanent foundation and retaining walls only.
The passive pressure given is appropriate for the depth of level structural fill piaced in front of a
retaining or foundation wall only. We recommend a safety factor of at least 1.5 for overturning and
sliding, when using the above values to design the walls. Restrained wall soil parameters should
be utilized for a distance of 1.5 times the wall height from corners in the walls.
The design values given above do not include the pffects of any hydrostatic pressures behind the
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent
foundations will be exerted on the walls. If these conditions exist, those pressures should be added
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need
to be given the wall dimensions and the slope of the backfifl in order to provide the appropriate
GEOTECH CONSULTANTS,INC. �^�
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design earth pressu�es. The surcha�ge due to traffic loads behind a wali can typically be
accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid
density.
Heavy construction equipment should not be operated behind retaining and foundation walls within
a distance equal to the height of a wall, unless the walls are designed fo� the additional lateral
pressures resulting from the equipment. The wall design criteria assume that the backfill will be
well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should
be accomplished with hand-operated equipment to prevent the walls from being overloaded by the
higher soil forces that occur during compaction.
Retaining Wall Backfill
Backfill placed behind retaining or foundation walls should be coarse, free-draining,
structural fill containing no o�ganics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of
particles passing the No. 4 sieve should be between 25 and 70 percent. The onsite soils
are not free-draining. If the excavated soils are reused as backfill, at least 12 inches of
gravel should be placed against the walls. Gravel should be used for the entire width of
backfill wh.ere seepage is encountered in the excavation.
The purpose of these backfill requirements is to ensure that the design criteria for a
retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the
wall. The top 12 to 18 inches of the backfill should consist of a compacted, relative':
impermeable soil or topsoil, or the surface should be paved. The ground surface must alsc
slope away from backfilled walls to reduce the potential for surface water to percolate into
the backfill. The sub-section entitled General Earthwork and Structural Fill contains
recommendations regarding the placement and compaction of structural fill behind retaining
and foundation walls.
The performance of any subsurface drainage system will degrade over time. Therefore,
moist conditions or some seepage through the walls are not acceptable, waterproofing
should be provided. This typically includes limiting cold-joints and wall penetrations, and
using bentonite panels or membranes on the outside of the walls. Applying a thin coat of
asphalt emulsion is not considered waterproofing, but will only help to prevent moisture,
generated from water vapor or capillary action, from seeping through the concrete.
Rockeries
We anticipate that rockeries may be used in the site development. A rockery is not intended to
function as an engineered stn,icture to resist lateral earth pressures, as a retaining wall would do.
The primary function of a rocfcery is to cover the exposed, excavated surface and thereby retard
the erosion process. We recommend limiting rockeries to a height of 8 feet and placing them
against only dense, competent, native soil. Loose�soils should be excavated and replaced with
quarry spalls.
The construction of rockeries is, to a large extent, an art not entirely controllable by engineering
methods and standards. It is imperative that rockeries, if used, are constructed with care and in a
GEOTECH CONSUITANTS,INC. � �
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proper manner by an experienced contractor with proven ability in rockery construction. The
rockeries should be constructed with hard, sound, durable rock in accordance with accepted local
practice. Soft rock, or rock with a significant numbe� of fractures or inclusions, should not be used,
in order to limit the amount of maintenance and repair needed over time. Provisions fo�
maintenance, such as access to the rockery, should be considered in the design. In gene�al, we
recommend that rockeries have a minimum dimension of one-third the height of the slope cut
above them.
Excavations and Slopes
Excavation slopes should not exceed the limits specified in local, state, and nationaf government
safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in
unsaturated soil away from property lines and existing structures, if there are no indications of
slope instability. Based upon Washington Administrative Code (WAC) 296, Part N, the soil type at
the subject site would be classified as Type B. Therefore, temporary cut slopes greater than 4 feet
in height cannot be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending
continuously between the top and the bottom of a cut. Flatter cuts, excavation sharing, and/or
dewatering will be necessary where excavations encounter heavy seepage or caving soils.
The above-recommended temporary slope inclination is based on what has been successful at
other sites with similar soil conditions. Temporary cuts are those that wifl remain unsupported for a
relatively short duration to allow for the construction of foundations, retaining walls, or utilities. The
cut slopes should be backfilled or retained as soon as possible to reduce the potential for instability.
Please note that loose, wet soils can cave suddenly and without warning. Contractors should be
made especially aware of this potential danger.
All permanent cuts into native soil should be incfined no steeper than 2:1 (H:V). Fill slopes should
not be constructed with an inclination greater than 2:1 (H:V). To reduce the potential for shallow
sloughing, fi(I must be compact2d to the face of these slopes. This could be accomplished by
overbuilding the compacted fill and then trimming it bacfc to its final incfination. Water should not be
allowed to flow uncontrolled over the top of any temporary or permanent slope. Also, all
permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce
erosion and improve the stability of the su�cial layer of soil.
Drainaqe Considerations
Foundation drains should be installed around the perimeters of the buildings, at the base of all
earth-retaining walls, and behind stepped foundation walls. These drains should be surrounded by
at least 6 inches of 1-inch-minus, washed rock and then wrapped in non-woven, geotextile fiiter
fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert
should be at least 6 inches below the bottom of a slab floor or the level of a crawl space, and it
should be sloped for drainage. Drainage should also_be provided inside the footprint of a structure,
where a crawl space will sfope or be lower than the surrounding ground surface or an excavation
encounters significant seepage. We can provide recommendations for inte�ior drains, should they
become necessary, during excavation and foundation construction.
. �1
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May 25, 1999 Page 8
All roof and surface water drains must be kept separate irom the foundation d�ain system. A
typical drain detail is attached to this repo�t as Plate 97. For the best long-term performance,
perforated PVC pipe is recommended for all subsurface drains.
Groundwater and wet soils were observed during our field worlc. Surface water was also observed
in shallow ditches across the site. If seepage is encountered in an excavation, it should be drained
from the site by directing it through drainage ditches, perforated pipe, or French drains, o� by
pumping it from sumps interconnected by shallow connecto� trenches at the bottom of the
excavation.
Building excavations and the site in general should be graded so that surface water is directed off
the site and away f�om the tops of slopes. Water should not be allowed to stand in any area where
foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to
buildings should slope away at least 2 percent, except where the area is paved.
Pavement Areas
The pavement section may be supported on competent, nativ� soil or on structural fill compacted to
a 95 percent density. Granular structural fill or geotextile fabric may be needed to stabilize soft,
wet, or unstable areas. To evaluate pavement subgrade strength, we recommend that a proof roll
be completed with a loaded dump truck immediately before paving. In most instances wher�
unstable subgrade conditions are encountered, an additional 12 inches of granular structural fill wi;
stabifize the subgrade, except for very soft areas where additional fill could be required. ThE
subgrade should be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to
grade. Recommendations for the compaction of structural fill beneath pavements are given in a
later sub-section entitled General Earthwork and Structural Fill. The performance of site
pavements is directly related to the strergth and stability of the underlying subgrade.
The pavement for lightly-loaded traffic and parking areas should consist of 2 inches of asphalt
concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt-treated base (ATB}.
We recommend providing heavily-loaded areas with 3 inches of AC over 6 inches of CRB or 4
inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with
truck traffic.
The pavement section recommendations and guidelines presented in this repo�t are based on our
experience in the area and on what has been successful in similar situations. As with any
pavements, especially thrase underlain by silty soils, some maintenance and repair of limited areas
can be expected as the pavement ages. To provide for a design without the need for any repair
would be uneccnomical.
Generai Earthwork and Structural Fill
All building and pavement areas should be stripped of su�face vegetation, topsoil, organic soil, and
other deleterious material. The stripped or removed materials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds.
� 3-8
GEOTECH CONSULTANTS,INC.
, . _ _
. ' SEB, Incorporated JN 99189
May 25, 1999 � Page 9
Structu�al fill is defined as any fill placed under a building, behind permanent retaining or foundation
walls, or in other areas where the underlying soil needs to support loads. All structural fill should be
placed in horizontal lifts with a moisture content at, or near, the optimum moisture content. The
optimum moisture content is that moisture content that results in the greatest compacted dry
density. The moisture content of fill is very impo�tant and must be closely controlled during the
filling and compaction process.
The allowable thickness of the fill lift will depend on the material type selected, the compaction
equipment used, and the number of passes made to compact the fift. The loose lift thickness
should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not
compacted to specifications, it can be recompacted before another lift is placed. This eliminates
the need to remove the fill to achieve the required compaction. The following table presents
recommended relative compactions for structural fill:
:Location af.�: �Minimum . -�_;'.
� x::`..., ...
�Fill Placement . _ ��rRelative�Compact�on ;�,�-
Beneath footings, slabs 95%
or walkways
Behind retaining walls 90% j
95°/a for upper 12 inches of I
Beneath pavements subgrade; 90% below that
level
Where: Minimum Relative Compaction Is the ratio, expressed in
percentages,of the compacted dry density to the maximum dry
density, as determined in accordance with ASTM Test
Designation D 1557-78(Modified Procto�j.
Considerations for reuse of the on-site soils as structural fill are discussed in the General section.
Structural fill that will be placed in wet weather should consist of an imported, coarse, granular soil j
with a silt or clay content of no more than 5 percent. The percentage of particles passing the No. '
200 sieve should be measured from that po�tion of soil passing the three-quarter-inch sieve.
LIMITATIONS
The conclusions and recommendations contained in this report are based on site conditions as I
they existed at the time of our exploration and assume that the soil and groundwater conditions i�
encountered in the tes� pits are representative of subsurface conditions on the site. If the
subsurface conditions encountered during construction are significantly different from those '
observed in our explorations, we should be advised at once so that we can review these conditions i
and reconsider our recommendations where necessary. Unanticipated soil conditions are �
commonly encountered on construction sites and cannot be fully anticipated by merely taking soil ;
samples in test pits. Subsurface conditions can also vary between exploration locations. Such
unexpected conditions frequently require making_additional expenditures to attain a properly ;
constructed project. It is recommended that the owner consider providing a contingency fund to
accommodate such potential extra costs and risks. This is a standard recommendation for all
projects.
� a_�
GEOTECN CONSULTANTS,INC.
, � � SEB, Incorporated JN 99189
May 25, 1999 Page 10
This report has been prepared for the exclusive use of SEB, Incorporated, and its representatives,
for specific application to this p�oject and site. Our recommendations and conclusions a�e based
on observed site materials, and selective laboratory testing and engineering analyses. Our
conclusions and recommendations are professional opinions derived in accordance with current
standards of practice within the scope of our senrices and within budget and time constraints. No
warranty is expressed or implied. The scope of our services does not include services related to
construction safety precautions, and our recommendations are not intended to direct the
co�tracto�'s methods, techniques, sequences, or procedures, except as specifically desc�ibed in
our report for consideration in design. We recommend including this report, in its entirety, in the
project contract documents so the contractor may be aware of our findings.
ADDITIONAL SERVICES
ln addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide
geotechnical consultation, testing, and observation services during construction. This is to confi�m
that subsurface conditions are consistent with those indicated by our exploration, to evaluate
whether earthwork and foundation construction activities comply with the general intent of the
� recommendations presented in this report, and to provide suggestions for design changes in the
event subsurface conditions differ from those anticipated prior to the start of construction.
However, our work would not include the supervision or direction of the actual work of the
contractor and its employees or a5ents. Also, job and site safety, and dimensional measurements,
will be the responsibility of the contractor.
The following plates are attached to complete this report:
Plate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 8 Test Pit Logs
Plate 9 Footing Drain Detail
. �-/�
GEOTECH CONSULTANTS,INC.
. . ____ __
� SEB� I�corporated JN 99189
May 25, 1999 � Page 11
We appreciate the opportunity to be of service on this project. If you have any questions, or if we
may be of fu�ther service, please do not hesitate to contact us.
Respectfuily submitted.
i GEOTECH CONSULTANTS, INC.
G �t. McG
,4, aF wAs,,, lrt,
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,��,'`'CIST E�� ,�'�'
s,sf�rvni.�•�'� S�zS;�
FXP!FES � �
Marc R. McGinnis, P.E.
Associate
DBG/MRM: alt
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;
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GEOTECH CONSULTANTS,INC.
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� ViCINITY MAP
GEOTECH s.E.B., iNc.
; CONSULTANTS � 186XX TALBOT RD. S.
� - KING COUNTY, WA
� dos No.r ao,.� Pro�.•
� 99188 MAY 1999 1
��
c . _
OTP-6 , OTP-5 0 P-4
�
� �
!
�
�
i
, OTP-7 0 P-3
� DTP-8
�
�
�
Z
0 OT -2
�
TP-10 �TP-9 ' OQ
� Z
� U
�
OTP-11 �
a �
a ,
F- i
�- EXlSTING HOUSE �
� OTP-� 2 pT -� �
�
�
TALBOT RD. S.
LEC3END:
Q APPROXiMATE TEST PIT LOCATION
� " S1TE EXPLORATION PLAN
_ GEOTECH s.E.B., iNc.
; CONSULTANTS 186XX TALBOT RD.. S..
' KING COUNTY, WA
� �oe Ne.r po,e� P/o►.�
�
''� ' 99188 MAY 1998 2
-��
� �� ��.� ��st���'`� TEST PIT 1
�� �'° �`��Q�`� �5
pQ' G° �°' J`' Description
TOPSOIL
Red-brown, silty SAND with some gravel, fine-grained, wet, medium-dense
(Weafhered Glacial Till)
�5'7% - becomes gray-b�own, dense to very dense (Glacial TiII)
5
13.9%
' SM :
i
I
10 ( i
(` II
* Test Pit was terminated at 12 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
15 * No caving was observed during excavation.
� t� o�� TEST PIT 2
`� �` ��
�4�,`��o`�r�,���d'`��,e, G5
� G° �S°' J5 Description
TOPSOIL
' '�� Red-brown, silty SAND with gravel, fine-grained, moist, medium-dense
�I, � I� (Weathered Glacia/ Till)
� �I - becomes gray-brown, dense to very dense (Glacial Till) I
� f '�'��i
! SM "
i .�. � '�
; � 'I - more gravelly and occasional cobbles within till
� : ; ! ::i
10 � '� ' (
* Test Pit was terminated at 10 feet on May 14, 1999.
" No groundwater seepage was observed during excavation.
"` No caving was observed during excavation.
15
TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
corrsuLz•a.rrrs,�rrc. King County, Washington
�
� � Job No: Date: Logged by: P/ate:
`�`r�' 99189 May 1999 DBG 3
�'1 T
�1 ' - -
��,�,�t��,�'`� TEST PIT 3
�Q�'� �'�o���`�o-o-'��� 5G5
� 9 G �S � Description
TOPSOIL
, , ,� � Red-gray, silty SAND with gravel and iron staining, fine-g�ained, very moist,
i� medium-dense (Weathered Glacia! Till)
5 �, gM
- becomes brown to gray, dense to very dense (Glacial Till)
10 '�
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
�� ��� �i�� TEST PIT 4
�4�,'���tio�o``'��`'�aa'°�.e ��5
Q G �S J Descrcption
TOPSOIL
;l l l l'i'� ! Brown, gravelly, silty SAND with cobbles, fine-grained, moist, medium-dense
ISM �
Ii!!'I'I ,
5 � ; ,� � �;', Bro�vn SILT, fractured, low plasticity, moist, stiff, iron stained
� MLI
i Ilili
10 j SP-SM I Brown, sli htl silt SAND, fine- to medium- rained, ve moist, dense �
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
" No caving was observed during excavation.
15
TEST PIT LOG
� � GEOTECH 186xx Talbot Road South �
CONSULTANTS,�rrc. King County, Washington
�
� . � Job No: Dafe: Logged by: Plate:
��� 99189 May 1999 DBG 4
�j-�S
1
� �.� . L�����'�� TEST P IT 5
��, o������a��`� G5
� p�Q �G° �C°' J`� Description
TOPSOII. and Forest Duff
' �� Brown, gravelly, silty SAND, fine-grained, moist, medium-dense
SM
III
5 Brown, slightly silty SAND, medium-grained, moist, medium-dense
- becomes finer grained
SPSY
� - becomes gravelly
10 SM Brown with iron staining, silty, gravelly SAND, medium- to coarse-g�ained, wet,
'❑ dense
' Test Pit was terminated at 11 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
i- 15
�
I
r-
�
�� oi� TEST PIT 6
�,'r�� . �� ��� ��
o�r�,�`�a�',��.z �5
pe4 Go ,�o- J5 Description
� TOPSOIL and Forest Duff
,..
� � �: : Brown, silt SAND with some ravel, moist, medium- rained, medium-dense
�,,�,� Y 9 9
; SM
5 I ��I��� �
;; ��, I� Brown-gray, silty SAND with some gravel, fine-grained, moist, dense to very
, I ; �!Ii: i
dense (Glacia! TiII)
SM _.
' .� :� �
10
,�I'I I:) : - becomes very moist I
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
'' No caving was observed during excavation.
1�
TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
CONSULTAN'I•s,INC. King County, Washington
�
�, � __ ___ _ .. Job No: Da1e: Logged by: Plate:
99189 May 1999• DBG 5
�—! !�
..
. ._ ,:• .., _,r
t � ��.��,���,ti�'�� TEST PIT 7
I Q�,�r �o rti��a��,� �5
� G° �o- J`' Description
TOPSOIL and Forest Duff
I SM I Red-brown, silty SAND with gravel, fine-grained, moist, medium-dense
18.2% Gray-brown, gravelly SAND, fine- to coarse-g�ained, wet, medium-dense
� - becomes dense
i
SP
10 �"" Brown, silty, gravelly SAND, fine-grained, moist, very dense (Glacial Til!)
* Test Pit was terminated at 10 feet on May 14, 1999.
" Moderate groundwater seepage was observed at 6 feet during excavation.
* No caving was observed during excavation.
15
I
i
� ��� `�� TEST PIT 8
2`��`r�`�o`��,~�ao-'°�2 5G�
I 9 � � � Descnptton
� TOPSOIL
I ' ' � ' �' G�ay-brown with iron staining, silty SAND, fine-grained, wet, medium-dense �
I I I I ' eathered Glacia/ Til! I
(� )
5 I � j I � - becomes slightly gravelly i
SM �, - becomes dense (Glacial Ti!!)
II �
' �I Ii
10
�I �! i
* Test Pit was terminated at 10 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
" No caving was observed during excavation.
1�
TEST PIT LOG
� _�` GEOTECH 186xx Ta(bot Road South
�r CONSULTANTS,�rrc. King County, Washington
.�
�, � ____ , Job No: Date: Logyed by: P/ate:
99189 May 1999 dBG 6
�-►1
... . .. :�v . -- -
��,���,��'ti� TEST PIT 9
�,r' �,o �,tie�d,�� G5
��Q G° �C°' J`' Description
TOPSOIL
; , �,.
� ! gM , Red-brown to gray with extensive iron staining, clayey SILT and fine-grained
� � ML : SAND, wet, loose to medium-dense
� ,; �
� Gray, fine-grained SAND with some silt, very moist to wet, medium-dense to
SPSY dense
10 �
'' Test Pit was terminated at 10.5 feet on May 14, 1999.
; Light groundwater seepage was observed at 6.5 feet during excavation.
'' No caving was observed during excavation.
15
�,�1 ���e�`i�� TEST PIT '10
�,r� ��o��,�ti���1a��`� �5
��4 C,o ,�a �`' Description
TOPSOIL
' j , ; Brown-gray with iron staining, silty SAND, fine-grained, wet, medium-dense
' (Weathered Glacia! TiIJ)
. � � 'f
,
� SM ,'
12.3% 'I I`) - becomes dense to very dense (Glacial Til!)
, , �..
I 'I'�
* Test Pit was terminated at 8 feet on May 14, 1999.
10 * No groundwater seepage was observed during excavation. ,
* No caving was observed during excavation. ,
15 �
' TEST PIT LOG j
� � GEOTECH 186xx Talbot Road South I
CONSULTANTS,li�c. King County, Washington
�
�, � _. ______ Job No: Date: Logged by: Plate:
99189 May 1999 DBG 7
. � ���U
r
' � � y�� �'� TEST P1711
�� �,r��o��,ti���a����,� �9
� 9�� G° �S°' 0`' Description
TOPSOIL
Gray-brown with iron staining, silty SAND with trace gravel, fine-grained, wet,
I �' loose to medium-dense (Weathered Glacial Till)
� SM _ becomes very dense (Glacial TiJ!)
5 IIII � :
' Test Pit was terminated at 6 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
" No caving was observed during excavation.
10
� 15
� ��� �i� TEST PIT 12
�4�'���'0 0��,��'��o-a��,� ��5
� G � � Descnption
TOPSOIL
' ; �( �'�� Brown-gray with iron staining, silty SAND with trace gravel, very moist, ;
I ' I; I medium-dense (Weathered Glacial Till) I
. :I. I: ` - becomes very dense (Glacia! Till)
� �� S M !
�(. I , I
�: I
:` � :
, I `: :I' I
10 * Test Pit was terminated at 9 feet on May 14, 1999.
* No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
15
TEST PIT LOG
� � GEOTECH 186xx Talbot Road South
corrsuLTArrrs,irrc. King County, Washington
�
� Job No: Date: Logged by: Plate:
����— � - � 99189 May 1999 OBG 8
� ��� I
S/ope bock/il/ owoy fiom
/oundolion. �
� � T/GNTL/NE ROOf ORA/N
� Oo nol connecJ /o /oo/ing d�ain.
BACXF/L L
See Iex� lor ViIPOR BARR/ER
�e�uiremenls. SLAB _�
WASHED ROCX �'° .'o''• ��� � �� ��%��� `:�, 4��min.
.e. � O.p: `� . ;�
�r-"'-� o - J. , �`Y M / ' /^l �
♦� �
6 min. .•:�. :
FREE-ORA/N/NG �
NGNWOVEN GEOTEXT/LE SAND/GRAVEL �
F/LTER F.4BR/C
4'�PERFORATED HARD PVC P/PE
/nve�J aJ /easl os /ow os /ooling and/or
c�awl spoce. Slope io d�ain. P/ace
weepholes downwo�d.
� FOOTING DRA1N DETAfL
GEOTECH s.E.e., iNc.
� CONSULTANTS 186XX TALBOT RD.. S.
� KING COUNTY, WA
� ..r.� doo No.+ Oah, Seoie+ i/oli+
r""-`"�� 99189 MAY 1999 N.T.S. 8
APPENDIX C
BasinSummary..................................................................................................C-1
CNCalculations.................................................................................................C-3
RunoffCurve Numbers .....................................................................................C-4
BasinMap................................................�.........................................................C-6
IsopluvialCharts................................................................................................C-7
Correction Factor to Pond Volume ...................................................................C-10
DetentionPond Sizing.......................................................................................C-11
BioswaleSizin�.................................................................................................C-13 '�
Equivalent Area Calculations............................................................................G16 ,
Capacity Calculations... ........................................................................C-17 II
Sediment Pond Sizing Calculations ..................................................................C-19 I
i
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2/10/00 4 : 7 : 22 pm Sound Engineering Inc. page 1
Borgata Apartments
Detention sizing calculations
BASIN SUMMARY
l
BASIN ID: al • NAME: pre-developed 2 yr
SBUH METHODOLOGY �
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : PElA PERV IMP
PRECIPITATION. . . . : 2 . 00 inches AREA. . : 4 .41 Acres 0 . 00 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 85 . 00 0 . 00
TC. . . . . 34 . 96 min 0 . 00 min
ABSTR.ACTION COEFF: 0 . 20
TcReach - Sheet L: 300 . 00 ns: 0 .4100 p2yr: 2 . 00 s : 0 . 1500
TcReach - Shallow L: 300 . 00 ks: 5 . 00 s : 0 . 1500
TcReach - Channel L: 300 . 00 kc: 5 . 00 s : 0 . 1500
PEAK R.ATE: 0 .44 cfs VOL: 0 . 29 Ac-ft TIME: 490 min
BASIN ID: a2 NAME: pre-developed of 10 yr
SBUH NlETHODOLOGY
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 3 . 00 inches AREA. . : 4 .41 Acres 0 . 00 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 85 . 00 0 . 00
TC. . . . . 34 . 96 min 0 . 00 min
ABSTRACTION COEFF: 0 .20 '
TcReach - Sheet L: 300 . 00 ns : 0 . 4100 p2yr: 2 . 00 s : 0 . 1500
TcReach - Shallow L: 300 . 00 ks : 5 . 00 s : 0 . 1500
TcReach - Channel L: 300 . 00 kc: 5 . 00 s : 0 . 1500
PEAK RATE: 1 . 03 cfs VOL: 0 . 58 Ac-ft TIME: 490 min
BASIN ID: a3 NAME: pre-developed of 100 yr
SBUH NIETHODOLOGY
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS: 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP '
PRECIPITATION. . . . : 4 . 00 inches AREA. . : 4 .41 Acres 0 . 00 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 85. 00 0 . 00
TC. . . . . 34 . 96 min 0 . 00 min
ABSTRACTION COEFF: 0 . 20 ',
TcReach - Sheet L: 300 . 00 ns: 0 .4100 p2yr: 2 . 00 s : 0 . 1500 '
TcReach - Shallow L: 300 . 00 ks: 5 . 00 s : 0 . 1500 ,
TcReach - Channel L: 300 . 00 kc: 5 . 00 s : 0 . 1500 '
PEAK RATE: 1 . 69 cfs VOL: 0 . 90 Ac-ft TINIE: 490 min ',
C' \
2/10/00 4 : 7 :22 pm Sound Engineering Inc . page 2
Borgata Apartments
Detention sizing calculations
---------------------------------------------------------------------
---------------------------------------------------------------------
BAS IN SUNII�IARY
BASIN ID: a4 NAME: post-developed 2 yr
SBUH NIETHODOLOGY
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS: 0 . 00 cfs
RAINFALL TYPE. . . . : ElA PERV IMP
PRECIPITATION. . . . : 2 . 00 inches AREA. . : 4 .41 Acres 0 . 00 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 96 . 80 0 . 00
� TC. . . . . 1. 54 min 0 . 00 min
ABSTRACTION COEFF: 0 . 20
TcReach - Sheet L: 100 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 1500
TcReach - Shallow L: 300 . 00 ks : 27 . 00 s : 0 . 1500
TcReach - Channel L: 300 . 00 kc :42 . 00 s : 0 . 1000
PEAK RATE: 1 . 75 cfs VOL: 0 . 61 Ac-ft TIME: 470 min
BASIN ID: a5 NAME: post-developed 10 yr
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS : 0 . 00 cfs
R.AINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 3 . 00 inches AREA. . : 4 . 41 Acres 0 . 00 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 96 . 80 0 . 00
TC. . . . . 1. 54 min 0 . 00 min
ABSTRACTION COEFF: 0 .20
TcReach - Sheet L: 100 . 00 ns: 0 . 0110 p2yr: 2 . 00 s : 0 . 1500
TcReach - Shallow L: 300 . 00 ks : 27 . 00 s : 0 . 1500
TcReach - Channel L: 300 . 00 kc : 42 . 00 s : 0 . 1000
PEAK R.ATE: 2 . 77 cfs VOL: 0 . 97 Ac-ft TIME: 470 min
BASIN ID: a6 NAME: post-developed 100 yr
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 .41 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 4 . 00 inches AREA. . : 4 .41 Acres 0 . 00 Acres '
TIN� INTERVAL. . . . : 10 . 00 min CN. . . . : 96 . 80 0 . 00
TC. . . . . 1. 54 min 0 . 00 min
ABSTRACTION COEFF: 0 .20
TcReach - Sheet L: 100 . 00 ns: 0 . 0110 p2yr: 2 . 00 s: 0 . 1500
TcReach - Shallow L: 300 . 00 ks : 27 . 00 s : 0 . 1500
TcReach - Channe� L: 300 . 00 kc : 42 . 00 s: 0 . 1000
PEAK RATE: 3 . 78 cfs VOL: 1 . 33 Ac-ft TIME: 470 min
C'�
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1019 PACIFIC AVE.,SUITE 906,TACOMP�WA 98402•(253)573-0040•FAX(253)573-0142 �J
E-MAIL•SOUNDINC�AOL.COM
KING COUNTY, WASHINGTON, SU,RFACE WATER DESIGN MANUAL �I�I
TABLE 3.5?B SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS '
SCS WESTERN WASiiINGTON RUNOFF CUFiVE NUMBERS (Published by SCS in 1982)
Runoff curve numbers fo�selected agricultural, suburban and urban land use for Type �A
rainfall distribution, 24-hour storm duration.
CURVE NUMBERS BY
HYDROLOGIC SOIL GROUP
LAND USE DESCRIPTION A B C D
Cultivated land(t): winter condition � 86 91 94 95
Mountain open areas: low growing brush and grasslands i 74 82 89 92
I ,
Meadow or pasture: I 65 78 89
Wood or foresi Iand: undisturbed or older second growth 42 64 70 81 �
Wood o�forest land: young second growth or brush I 55 72 8� 86
Orchard: with cover crop � 81 � 92 94
Open spaces, lawns, parks, goff courses. cemet2ries, �
landscaping.
good concfition: grass cover on 75%
or more of the area 68 SO � c,p
fair ccndition: gr2ss cover on 50°G
to 754'0 of the area ; 77 85 90 g2
I
Gravel raads and parking lots 76 85 d9 9t �
Dirt Toads and parking lots I 72 82 E7 89 I
Impervious surfaces, pavement, rcofs, etc. � 93 98 98 98
Open water bodies: lakes, wetlands, ponds, etc. I 100 t00 100 100 I
� Single Family Residential (2) i
� Dwe!{�rg Und/Gross Acre °b Impervious (3} �
1.0 DU/GA i5 Separate �ur�e number
1.5 DU/GA 20 shall be selected
2.0 DU/GA 25 for pervious and
2.5 DU/GA 30 impervious portion
3.0 DU/GA 34 of the site or basin
3.5 DU/GA 38
4.0 DU/GA 42
. 4.5 DU/GA �46
5.0 DU/GA 48
', 5.5 DU/GA 50•
6.0 DU/GA 52
6.5 DU/GA 54
7.0 DU/GA 56
PI ned unit developments, % impervious
cc�ominiums, apartments, must be computed
cor��mercial business and
indu�triat argas. ,
(t) For a more detailed description of agncultural land use curve numbers refer to Nationai Engineering I
Handbook, Seciior.�, Hydrology, Chapter 9, Augusi 1972.
(2) - Assumes roof and dr�reway runoff is directed into sireet/storm system.
(3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. I
� 3.5.2-3 , 11/92 ,
e ��
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
(2) CN values can be area weighted when they apply to perviaus areas of similar CN's (within 20
:' -- -• CN points). However, high CN a�eas should not be combined with low CN areas (unless the
low CN areas are less than 15°�6 of the subbasini. In this case, separate hydrographs should be
generated and summed to form one hydrograph.
FIGURE 3.SZA HYDROLOGIC SOIL GROUP OF THE SOILS IN tiINC COUNTY
HYDROLOGIC HYDROLOGIC
SOIL GROUP GROUP' SOIL GROUP GROUP•
Alderwood Orcas Peat D
Arents, Alderwood Material C Oridia D
Arents. Everett Material 8 Ovall C
Beausite C Pilchuck C
Bellingham D Puget D
Briscot D Puyallup 8
Buckley 0 Ragnar B
Coastal Beaches Variable Renton D
Eartmont Silt Loam D Riverwash Variable (
�dgewick C Salal C
Everett A/B 'Samrr,amish D
Indiancla � Seatile D
Kitsap C I Shacar D
Klaus C Si Si1t C
Mixed Allwial Land Variable Snchomish D ,
Neilton A Sultan C
Newberg B Tukwila D
Nooksack C Urban Variable
Normal Sandy Loam D Woodinville i D
HYDROIGC�IC SOIL GRCU? C(.r�,.SSiF(Cn i(ONS
1
A. (Low r�noff potentiat). Soiis having high irfiltration ratas, evan when ,horoughly wett�, and consisting
cniefly o�deep, weil-to-excessively drainec2 sancs or gravels. These scils have a hign rate cf water
transmission.
B. (Moderatety low runoff potentiaJ). Soils having moderate infiltration rates when ihoroughly wetted, and
consisting chiefly of moderately fine to moderately caarse textures. These soils have a moderate rate of
water transmission.
C. (Moderately high runoff poterttiai). Soils having slow in�i tration rates when thoroughly wetted, and
consisting chiefly of soils with a layer that impedes downward mavement of water, or soiis with moderately
fine to fine textures. These soils have a slow rate of water transmission.
D. (High nanoff poient�al). Soi(s having very slow infiltraiion rates when thoroughly wetted and c�nsisting
chiefly of clay soils with a high sweiling potential, sols with a permanent hign�+rater table, soi(s with a
hardpa� or cfay layer ai or near the surface, and shallow soits over neariy impervious materiai. These soils
have a very slow rate of water transmission.
• From SCS, TR-55, Second Edition, June 1986, Exhibit A-1. Revisions made frcm SCS, Sod Interpretation
Record, Form �5. September t988.
� 3.5.2-2 11/92�
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NGINEERING, In c. KMB 2/�.5/0 0 °F !,
Bus: (253) 573-0040
Fax: (253) 573-0142 CHECKED: SCALE: �
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� �r,;�r � ��! "i�_ �y,
� � � !�� � L,� '��I� Y�
_- ��' ���w � ����,/� �,
I�.�e.�w.w��� �� _ ♦�---i
- A���ry ,-�-..�'1►.`,� ' ,��'l�l r,�� -
� �/��:. r��!` � -iJ'��►• '' /
�i�• � � wri�- _1��t, C Fi �
�•� � �r- �!� f _ -��
' �.,���� �� � �
� `�:�:������Mi�,
. . . - - . �,��,�►�t��►��� -
- . ��.�.:
.. . . .. . .c►�s.a���
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` ����_ �
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I
ORAFT TACOMA STORMWATER MANAGEMENT MANUAL - VOLUME I I
6.5.9 Correction Factor to Pond Volume
When designing runoff quantity conirol facilities, the Engineer shall apply a co�rection factor to
the design volume when using a unit hydrograph method to model 24-hour storm events. The
coneciion factor is shown in Figure 6.1 and shall be used to increase the proposed pond
volume by the applicable percentage, i.e. 10,000 c.f. + 30°� = 13,333 c.f. This factor is
based on site impervious cover. If the facility is to serve for water quality also, the po�d depth
cannot be increased beyond the criteria established in Chapter 7. NOTE: This factor does not
apply to infiltration facilities or facilities sized with a continuous simulation mode! such as
HSPF however, the design engineer is encouraged to incorporate an appropriate facior of
safety based upon the level of detail inctuded in the model.
FIGURE 6.1
VOLUIVIE CORRECTION FACTOR TO BE APPLIED TO RUNOFF QUANTiTY i
CONTROL BMPS BASED ON S(TE IMPERVIOUS COVER
� II
50
i �
45 � ^� � il
� � - � ' �
i
� !
O 35
U � /� i
v � ;
30 ; i
o f � s
�
�" 25 =
U ( � •
w
c Z� = u
O 15 ( ' i
,o L � � �
o zo � � � ,�o
. srr� w+pF�v,ous c�v�x r,c�
. Reference: Barker, et. af., 'Perfarmance of �eternion Ponds Designed According to Current Standards', 199Q.
6.6 DETENTION/RETENTION DESiGN CRITERIA
6.6.1 Discharge Criteria
U�less exempted in Section 6.4, the fo(lowing runoff quantity control requirements shall apply:
1. . Discharge Point - The discharge point for the projeci shall occur at the natural location.
�"
C -�o
s-s
.�,
2/10/00 6 :43 :22 pm Sound Engineering Inc. page 1
Borgata Apartments
Detention sizing calculations
STAGE STORAGE TABLE
RECTANGULAR VAULT ID No. 1 ',
Descriptio • tention Vault �
Length: 73 . ft. Width: 40 . 00 ft. voids : 1 . 000 '�
/.�, ,
� VJ iT�-►v�.r G.Jr-R.e c,T �v,.r �o c,j J CZ-
W`{l4.!. w�. . � I
�����-. -�er�. ����,��3 (,� -��� = r�o �- ,,� �.e.�.�w w r c�.c.����.� �a -�:�
STAGE c----STORAGE----� STAGE c----STt7RAGE----> STAGE <----STORAGE----> STAGE <----STORAGE---
(ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-Ft- (ft) ---cf--- --Ac-:
151.70 0.0000 0.0000 153.80 6132 0.1408 155.90 12264 0.2815 158.00 18396 0.4�.
151.80 292.00 0.0067 153.90 6424 0.1475 156.00 12556 0.2882 158.10 18688 0.4�
151.90 584.00 0.0134 154.00 6716 0.1542 156.10 12848 0.2949 158.20 18980 0.4357
152.00 876.00 0.0201 154.10 7008 0.1609 156.20 13140 0.3017 158.30 19272 0.4424
152.10 1168 0.0268 154.20 7300 0.1676 156.30 13432 0.3084 158.40 19564 0.4491
152.20 1460 0.0335 154.30 7592 0.1743 156.40 13724 0.3151 158.50 19856 0.4558
152.30 1752 0.0402 154.40 7884 0_1810 156.50 14016 0.3218 158.60 20148 0.4625
152.40 2044 0.0469 154.50 8176 0.1877 i56.60 14308 0.3285 158.70 2C440 0.4692
152.50 2336 0.0536 154.60 8468 0.1944 156.70 14600 0.3352 158.80 20732 0.4759
152.60 2628 0.0603 154.70 8760 0.2011 156.60 14892 0.3419 158_90 21024 0.4826
152.70 2920 0.0670 154.80 9052 0.2078 156.90 15184 0.3486 159.00 21316 0.4893
152.80 3212 0.0737 154.90 9344 0.2145 157.00 15476 0.3553 159.10 21608 0.4961
152.90 3504 0.0804 155.00 9636 0_2212 157.10 15768 0.3620 159.20 21900 0.5028
153.00 3796 0.0871 155.10 9928 0.2279 �57.20 16060 0.3687 159.30 22192 0.5095
153.10 4088 0.0938 155.20 10220 0.2346 157.30 16352 0.3754 159.40 22464 0.5162
153.20 4380 0.1006 155.30 10512 0.2413 157.40 16644 0.3821 159.50 22776 0.5229
153.30 4672 0.1073 155.40 10804 0.2480 157.50 16936 0.3888 159.60 23068 0.5295
153.40 4964 0.1140 155.50 11096 0.2547 157.60 17228 0.3955 159.70 23360 0.53E3
153.50 5256 0.1207 155.60 11388 0_2614 157.70 17520 0.4022 159.80 23652 0.54_'��
153.60 5548 0.1274 155.70 11680 0.2681 :57.80 17812 0.4089 159.90 23944 O.SS9%
153.70 5840 0.1"s4i 155.3C 11972 J.2748 :57.90 :B:JS 0.415e lEJ.�O 24235 0.5554
1 �11
v
2/10/00 6 :43 : 22 pm Sound Engineering Inc, page 2
Borgata Apartments
Detention sizing calculations
STAGE DISCHARGE TABLE
MULTIPLE ORIFICE ID No. 1
Description: Outlet Control Structure
Outlet Elev: 152 .20
Elev: 152 . 20 ft Orifice Diameter: 1. 9922 in.
Elev: 156 . 50 ft Orifice 2 Diameter: 6 . 6563 in.
STAGE <--DISCHARGE---� STAGE <--DISCHARGE---� STAGE <--DISCHARGE---> STAGE <--DISCHARGE---�
(ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- ------- (ft) ---cfs-- -------
152.20 0.0000 154.00 0.1445 155.80 0.2043 157.60 1.5113
152.30 0.034: 154.10 0.1485 155.90 0.2072 157.70 1.5697
152.40 0.0482 154.20 0.'_523 156.00 0.2099 157.80 1.625?
152.50 0.0590 154.30 0.1561 156.10 0.2127 157.90 1.6797
152.60 0.0681 154.40 0.1597 156.20 0.2154 158.00 1.�319
152.70 0.0762 154.50 0.1633 156.30 0.2181 158.10 1.7824
152.80 0.0834 154.60 0.1669 156.40 0.2207 158.20 1.8315
152.90 0.0901 154.70 0.1703 156.50 0.2234 158.30 1.8791
153.00 0.0963 154.80 0.1737 156.60 0.6061 158.40 1.9255
153.10 0.1022 154.90 0.1770 156.70 0.7662 156.50 1.9707
153.20 0.1077 155.00 0.1802 156.8D 0.8895 158.60 2.0148
153.30 0.1134 155.10 0.1834 156.90 0.9939 158.70 2.0579
153.40 0.1180 155.20 0.1865 157.00 1.0861 158.80 2.1001
153.50 0.1228 155.30 0.1696 157.10 1.169� 158.90 2.1414
153.60 0.1274 155.40 0.1927 157.20 1.2468 159.00 2.1819
153.70 0.1319 155.50 0.1956 157.30 1.3186
153.80 0.1362 155.60 0.1986 157.40 1.3862
153.90 0.1404 155.70 0.2015 157.50 1.4503
C�(�
2/10/00 6 : 43 :24 pm Sound Engineering Inc. page 3
Borgata Apartments
Detention sizing calculations
---------------------------------------------------------------------
---------------------------------------------------------------------
LEVEL POOL TABLE SUNlMARY
MATCH INFIAW -STO- -DIS- <-PEAK-> OUTFIAW STORAGE
c--------DESCRIPTION---------� (cfs) fcfs) --id- --id- <-STAGE> id (cfs) VOL (cf)
2 YR 24 HOUR ................. 0.22 1.75 1 1 156.37 10 0.22 13641.66 cf
10 YR 24 HOUR ................ 1.03 2.77 1 1 156.85 11 0.94 15034.59 cf
100 YR 24 HOUR ............... 1.69 3.78 1 1 157.92 12 1.69 18154.87 cf
C-f 3
Size Biofiltration Swale
Flow 1.01 cfs
slope (s) 1.00°/a (bottom slope for for biofiltration design)
depth (y) 0.33 ft.
Mannings n 0.07
Sides (z) 3 (3 to 1 side slope preferred)
Actual Length 135 ft. (desired length is 200 ft.)
Required bottom width (b) calculation
Q = (1.49/ n) x A x R'f3x� (mannings equation)
A = (b+ zY)Y
R = A/(b+2y l+ z' )
"b" is solved for using a computer spreadsheet function to obtain
a trail and error solution of b = 2.58 feet, for a desired length of 200 feet.
check Q = 1.011 cfs, OK same as given
Velocity = 0.857 fps <1.5 OK
Residence Time = 3.9 mins. 1.178
Find bottom width required if actual length is 135 ft. (Minimum length is 50 feet.)
For equal Surface Areas:
Required water Surface area = (2zy+b) x 200 feet
= 912 SF
Actual bottom width required = (Des. Surf. Area)/(length (actual)) - 2zy
b = 4.78 ft.
Filename Biosx�ale.x/s Tab BIOSW.9LE 2i10%00 6:26 P,ti1 �_( l�
l 1
2/10/00 4 : 7 : 37 pm Sound Engineering Inc. page 1
Borgata Apartments
Detention sizing calculations
---------------------------------------------------------------------
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BAS IN SLTNIl�ARY
BASIN ID: WQ NAME: post-devel 64% of 2yr (6mo)
SBUH NIETHODOLOGY
TOTAL AREA. . . . . . . : 4 . 41 Acres BASEFLOWS: 0 . 00 cfs
R.AINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 1. 28 inches AREA. . : 4 . 41 Acres O . Oa Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 96 . 80 0 . 00
TC. . . . . 1. 54 min 0 . 00 min
ABSTR.ACTION COEFF: 0 .20
TcReach - Sheet L: 100 . 00 ns : 0 . 0110 p2yr: 2 . 00 s : 0 . 1500
TcReach - Shallow L: 300 . 00 ks : 27 . 00 s: 0 . 1500
TcReach - Channel L: 300 . 00 kc : 42 . 00 s : 0 . 1000
PEAK R.ATE: 1 . 01 cfs VOL: 0 . 35 Ac-ft TIME: 470 min
C-I5
�Q��� v���� �-�" �A-�C���Tta�1S
Qtn 1 1/�ql.C-1 1 Ci 2�4 Q�' �'JO o S� �LJ�J Q�
REC12 Event Summary:�lv,�.�,�� �-� W�z�t,-� ` t,,,�}.kn d �'
BasinlD Peak G� Peak T Peak Vol Area �ethod Raintype Event
------- (cfs) (hrs) (ac-ft) ac /Loss
REC12 0.13 7.83 0.0458 0.75 SBUH/SCS TYPEIA 6-MONTH
Drainage Area: REC12
Hyd Method: SBUH Hyd Loss Method: SCS CN Number
Peak Factor: 484.00 SCS Abs: 0.20
Storm Dur 24.00 hrs
Area CN TC
Pervious 0.0000 ac 0.00 0.00 hrs
Impervious 0.7500 ac 94.00 0.01 hrs
Total 0.7500 ac
Supporting Data:
Impervious CN Data:
REC BDLG AND BLDGS 1 2 AND LAWNS 94.00 0.7500 ac
Impervious TC Data:
Flow type: Description: Length: Slope: Coeff: Travel Time
Sheet ROOF 25.00 ft 30.00% 0.0110 0.17 min
Channel ROOF LEADER 600.00 ft 15.00% 42.0000 0.61 min
TC of 0.79 min < 5 min, program will use a tc of 5 min in computations.
EXISTING NORTH Event Summary: A��,� F�o,�v�,���o��,`'`�r W�Sj°�
BasinlD Peak Q Peak T Peak Vol Area Method Raintype Event
------- (cfs) (hrs) (ac-ft) ac /Loss
EXISTING NORTH 0.05 8.67 0.0460 1.76 SBUHiSCS TYPEIA 6-MONTH
Drainage Area: EXISTING NORTH
Hyd Method: SBUH Hyd Loss Method: SCS CN Number '
Peak Factor: 484.00 SCS Abs: 020
Storm Dur 24.00 hrs ;
Area CN TC I
Pervious 1 J600 ac 85.00 0.42 hrs ;
Impervious 0.0000 ac 0.00 0.00 hrs
Total 1.7600 ac
Supporting Data:
Pervious CN Data: !
EXISTING NORTHERN BASIN 85.00 1.7600 ac I
Pervious TC Data:
Flow rype: Description: Length: Slope: Coeff: Travel Time ��
Sheet SHEET FLOW 200.00 ft 15.00% 0.4000 21.12 min �
Shallow SHALLOW CHANNEL FLOW 380.00 ft 15.00% 5.0000 3.27 min �
Channel TALBOT RAOD DITCH 110.0o ft 2.00% 17.00Q0 0.76 min �
i i
�
. �,�� I
.:F . �
Worksheet
Worksheet for Circular Channel
Project Description
Project File m:199121\project2.fm2
Worksheet 6' ROOF DRAIN � 2.00%
Flow Element Circular Channel
Method Manning's Formula
Solve For Discharge
Input Data
Mannings Coefficient 0.013
Channel Slope 0.020000 ft/ft
Depth 0.50 ft
Diameter 6.00 in
Results
Discharge 0.79 cfs 7 ���-�l� c�c,% : (�,��G-�^� ��;'��+►»�/S
Flow Area 0.20 ftz ��a�, /� �,., � 3
Wetted Perimeter 1.57 ft
Top Width 0.15e-7 ft
Critical Depth 0.44 ft
Percent Full 100.00
Critical Slope 0.017869 ft/ft
Velocity 4.04 ft/s �
Velocity Head 0.25 ft
Specific Energy 0.75 ft
Froude Number 0.2e-3
Maximum Discharge 0.85 cfs
Full Flow Capacity 0.79 cfs
Full Flow Slope 0.020000 ft/ft
Flow is subcritical.
G11
02/14/00 FlowMaster v5.13
02:07:24 PM Haestad Methods, Inc. 37 Brookside Road Waterbury,CT 06708 (203) 755-1666 Page 1 of 1
BLDGS 1 2 3 Event Summary:
BasinlD Peak� Peak T Peak Vol Area Method Raintype Event
------- (cfs) (hrs) (ac-ft) ac /Loss
BLDGS 1 2 3 0.44 7.83 0.1441 0.30 SBUH/SCS TYPEIA 100 yr
Drainage Area: BLDGS 1 2 3
Hyd Method: SBUH Hyd Loss Method: SCS CN Number
Peak Factor: 484.00 SCS Abs: 020
Storm Dur 24.00 hrs
Area CN TC
Pervious 0.0000 ac 0.00 0.00 hrs
Impervious 0.3000 ac 98.00 0.01 hrs
Total 0.3000 ac
Supporting Data:
Impervious CN Data:
BLDGS 1 2 3 ROOF DRAINS 98.00 0.3000 ac
Impervious TC Data:
Flow type: Description: Length: Slope: Coeff: Travel Time
Sheet ROOF 25.00 ft 30.00% 0.0110 0.17 min
Channel ROOF LEADER 600.00 ft 15.00% 42.0000 0.61 min
TC of 0.79 min < 5 min, program will use a tc of 5 min in computations.
i ,
__
,�
�tsa,
C'IV
Size Sediment ponds (�ng councy>
Surface Area= FS(G12/V,�,)
Q2= 1.75 cfs (Peak Flow , 2-yr 24hr Storm Event)
V�= 0.00096 fUs (Particle Settling Velocity)
FS= 2 (Factor of Safety)
SA=2'G�2/VS�= 3645.83 sf, (Surface area at Top of Riser)
(Per King County Stormwater Manual Pg. 5.4.5.2-2)
Surface Area at Top of Riser Provided = 2800sf
2' Settling Zone
1.5' Sediment storage
Principal Spilway(Riser) Diameter
Q,o =2.77cfs (Peak Flow, 10yr Pre-developed )
H = 1 ft. (Head measured from Top of Riser to Top of Spillway)
Diameter= 12" (From Table, Appendix "B")
Dewatering Orifice
Ao=(AS(2'h)"'')/(10.6'3600"T'g"�') i
Ao= 0.001856 (Orifice Area , Square Feet) '
A5= 3645.83 (Pond surface Area, Square Feet)
h = 3.5 (Height of Riser in Feet)
T= 24 (Dewatering Time, HRs
g = 32.2 (Acceleration of gravity ftlsec2)
Dewatering Orifice Diameter
D- 24*(Ao/3.14)^.5 = - 0.58 in
Filenume SEDI.ME.VT PO,VDS.xls Tub K/.b'G-POND 02/I1/L000 Z:58 PM C�I�
;
��` -
��.
i
4
;;�i
_
�
APPENDIX D
Maintenance and Operations Manua1................................................................D-1
Retention/Detention Summary Sheet................................................................D-10
Declaration of Covenant....................................................................................D-12
`,:
,
I
t
� ,
KINCi COUNTY, WA38INC3TON, SURFACE WATER DESI (� N MANUAL
MAINTENANCE REQUIREMENTS FOR
�- PRIVATELY MAINTAINED DRAINAGE FACiL1TIES
N0. 1 - PONDS
MaYM�n�� Candfdam Wlw�Mainbiw�cy Rwutb E�ct�d NRwn
Cowipaw�t D�f�at b NNd�d Maint�n�na M Pwform�d
Gawr�l TrMh�D� Any vesh snd debri�which excsed 1 cubio 7rash and debris deared from
. foot per 1,000 square fs�t (thi�is about squal site.
• ' to the amount of us�h it would taks to fill up
one�tandard aizs offic� parbeps canl. In
penerd, tMr�shouid b�no viwal evidenc�of
dumpinp.
Pawnous Any paso�ous vsqsution wtich may No danper of pasonous
VeQetetion constituts a hu�rd to County penonnel or the veqetaoon where County
public. Exart�ples of pawnou�vepetadon peroonnel or the public miqht
include: tstay rspwort,poison oak, stinpinq normaily bs. (Coordinatian with
nettle�,devils club. Seetde/Kinp County Hedth
Deperanent} '
Pollution Oil, �dir», o►othe�contaminanb of one No contaminann present other
pailon or mors or any emount found tfi�t than a surfacs film, (Coordinacen
could: 1) caus�damaas to plent, ertimai,o� with Ssettle/fGnp County Heeicn
merins life;2) conatitute a fire hazerd;or Depertmertt)
3) bs flushed downatrsam durinQ rain stormt.
Urrrwwed Grs�s/ If facility is Ixatsd in privets residerrod area, When mowinp is nseded,
Ground Cover mowinp is needed when prass exceed� 18 yrau/pround cover ahould bs
inchs�in heiQht. In other sreas,the penerd mowsd to 2 inches in heipht.
policy is to maks the pond aits match edjacent
. ' pround covsr and tertain as IonQ a�thers i�no
interferencs with the functio� of ths facility.
Rods�t Holes Any evidence of rode�t hole�if fecility is Rodents destroyed end dam or
sctnp u a dam or berm, or any evidencs of bertn repaired. (Caordinetion with
water pipirp throuph dem o�bertn via rodent Seattfe/Kiny County Heelth
holes. Deparcnentl
trnects When insects auch as wasps and homsu I�sects desvoyed o� removsd
interfe�s with msintenance activitiss. from eite.
Trs�Growth Trse prowth dos�not dlow maintensnc� T�ees do not hinder maintenance
accsas or irrterferos with msintenenc��cvvity sctivitiss. Sslectively cultivats
(i.s., slope mowinp, siit removd,vactorinq, or trees wch as eldero for flrewood.
squipmern movemsMsl. If trses sro not
irrts�ferinq with sccess,Iseve trse�sioM.
Sid�Slop�s of Eroaon Eroded damps owr 2 inche�deep wF�n Slopes ahould bs stebilized by
Pond caus�of drnep�ia so!present or whero usinq appropriats erosion co�ud
- thsro is potential fo�eorttinued erosion, mea�ure(sl;e.p., rock
rsinforcement.plantinQ of yrass.
compaction.
Storp�An� S�dim�M Accumul+tsd ssdirtN�+t that excsed� 109f.of Sed+ment cleaned out to desipned
tl+�desipned po�d d�pth. pond shapa and depth;pond
ross�ded if nscessary to contrd
eroaon.
Pond DikN S�ttfern�nts Any pert of dik� wHeh has�atded 4 inches Dike should be built back to the
low�r than ths desipn elev�tion. desipn sisvaoon.
Em�rq�noy Rodc Ibissinq Or�iy one layer of rodc s�dsts abow n�tivs sal Replace rocks w de�ipn
OwrAowJSpiNwq in sro fiw*qusro teet or larps�, or eny standerd�.
�xpowro of netive soii.
b-I .
� A-1 11/94
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 3 - CLOSED DETENTION SYSTEMS (PIPES/TANKS)
�__ Mainbnane� Cordttlona VYh�n Matnt�ane� Raults Exp�ct�d
Canpon�nt DN�et b NNd�d Mlh�e Mal�ana li PKtontMd
StoraQe Ana Plufly�d Air Verns On�-half of the cross s�tjon of a wnt is Wnts fre�of debris and ssdlmenL
bbcked at any poiM wifh debris and
a�diment.
Dsbris and Accumulated sedim�M depth excesds Ail sediment and debris removed from
S�dim�nt 1096 of th�diamet�r ot tM storag�arsa atorape aroa.
for 1/2 I�npth of atorap�vauft or any
point depth exceeds 15%of diamster.
Example: 72�nch storags tank would
nquirs deaninfl when ssdiment reaches
depth of 7 inches for mon than 1/2
length of tank.
Joints Bstween Any aack allowi�g materia!to be A!I joims between tank/pips sections ara
Tank/Pipe Section Vansported into facility. sealed.
Tank/Pips Be�t My part of tank/pips is bent out of shape Tank/pipe repaired or replaced to design.
Out of Shaps more than 10%of its design shape.
Manhale Cover not in Place Cover is missing or only partially in place. Manhole is ciosed.
Any open manhole requires maintenanoe.
Locking Mechanism cannot be opened by one Mechanism opens with proper toals.
Mechanism Not maintenance parson with proper tools.
Working Bolts into frame have less than 1/2 inch
of thread (may not apply to self-locking
lids).
Cover Difficult to One maintenancs person cannot remova Cover can be removed and reinstalled by
Rsmove lid after applying 80 pounds of lift. Intent one maintenance person.
is to keap cover from sealing off accass
to maintenance.
Ladder Rungs IGng County Safety Office and/ar Ladder meets design standards and
Unsafe maintenance person judges that ladder is allows maintenance persons safe access.
unsafe due to missing rungs, '
misalignment, rust,or cracks.
Catcfi Basins Ses'Catch Basins' Standard No. 5 See'Catch Basins'Standard No.5
_
. V/�
A-3 1/90
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 4 - CONTROL STRUCTURE/FLOW RESTRICTOR
Mai�nano� CondMlons Wlwn M�Man��w R�wlb Ezp�e�d
Compon«K D�f�e:t 1�NNd�d Wh�n Malnt�nana Is PKform�d
GM�aI Trash and D�bris dstano�b�lwwn d�is butld�p and All trash and debris removsd.
(hdudq bottom of ariffc�plat�is I�ss than 1-1/2
S�dim�rtt) fMt. ,
SWctural Damay� Struatun b not s�curoly attach�d to Struetun aecuroly attached to wall and
manhoN wall and outbt plp�structuro aritet pipe.
ahould wpport at I�ut 1�000 pounds of
up ot down proswn.
Structun is not in upriqht position {allow Structurs I�oorrsct positio�.
up to 10X irom plumb�.
Connections to outlet pip�ars not Co�nections to outlet pipe ars watertight;
watsrtight and show sqns of rust. structurs repaired or replaced and worlcs
as designed.
My holes-other than designed holes- Structuro has no holas other than
in the structure. designed holes.
Cleanout Gate Damaged or Cleanout gate is not watertight or is Gate is watertight and works as designed.
Missinp missing.
Gate cannot be mowd up and dawn by Gats movea up and down easily and is
one maintenance psrson. watertight.
Chain Isadin�to gate is missing or Chain is in place and works as dasigned.
damaped.
Gats is rusted owr 50%of its surfacs Gete is ropaired or roplaced to meet
usa. design standards.
Ori�cs Plate Dama�ed or Convol device is nat worlcing propsriy Plate is in plaos and works as designed. '
Missinfl due to missing,out of place,or bent
oritice plats.
Obsuuctions Any trash,debria, sediment,or vepetation Plate is free of all obstructions and works
blocking the plats. as designed.
Overflow Pip� Obstructio�s Any Vaah or debris bbcking (or heving Pipe is frea of all obstructions and works
the potential of blocking)ths overflow as designed.
P�Pe•
Manhols SN'pos�d Dstention Systems'Standard See'Gossd O�tsntion Systams'Standard
No.3. No.3.
Catch Basin SN'Catch Basins'Standard No.5. Ss�'Catch Basi�s'Standard No.5.
b-3
A-4 1/�
� KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 5 - CATCH BASINS
Matnt�nana Condltlona Wh�n MaleO�nana R�w1ts Exp�ct�d
compoe.nt aa�t b N..a.a wr,.n MaMt�nano.i. w.+�orm.d
General Tash 3 Osbris Tnah or d�btis ot moro than 1/2 cubio No trash or deb�is locatsd immediately in
(Indudq foot which is locat�d immediately in fro�t froM of catch basin openinfl.
S�dirtHnty of th�catch basin op�nin�or is blockinp
capactty of basin by mon than t096.
Trash or debris(in tM basin)that No Vash or debris in ths catch basin.
exceeds 1/3 ths depth from ths bottom
of basin to irnert of tha iowest pips i�to
w out of the basin.
Trash or debris in any inlet or outlet pipe Inlet and outlet pipas frae of trash or
bbcking more than t/3 of its height. debris.
Dead animals or vegetation that could No dead animals or vegatation present
genarats odors that would cause within the catch basin.
complaints or dangerous gases (s.g.,
msthana).
Deposits of garbage exceeding 1 cubic No condition present which would attract
foot in voVume. o�support the breeding of insects or
rodents.
Structurat Damage Comer of frame extends mors than 3/4 Frama is aven with curb.
to Frame and/or inch past curb face into the strest (f
Top Slab applicable).
Top slab has holes larger than 2 square Top stab is free of holes and aacks.
inches or cracks wider than 1/4 inch
[mtent is to maks sure all material is
running into the basin).
Frame not sitting flush on top slab,i.e., Frame is sitting flush on top slab.
. separadon of more than 3/4 inch of the
frame from ths top slab.
Ctacks in Basin Gacks wider than 1/2 inch and longer Bnain replaced or repaired to dasign
Walls/Bottom than 3 feet,any evidence of soil particles standards.
entering catch basin through cracks,or
maintenancs penon judges that mucture
is unsound.
Gacka wider than 1/2 inch and Ionger No cracks more then 1/4 inch wide at the
than 1 foot at the joint of any inlet/ouUet joint of inlet/ouUet pips.
pipe or any evidence of soil partiGes
enterinfl catch basin through cradcs.
SsttlemeM/ Basin has settled more than 1 inch or has Basin replaced or repaired to design
Misalignment rotated rtwre than 2 inches out of standards.
_ alignment.
Fro Hazard Pressnce of chemicats such as natural No flammable chemicals present.
ges,oil,and gasoline.
Vegetation Vsgetatio�growing across and bbcking No vegetation blocking opening to basin.
rtwre than 1096 of the basin op�ninq.
Vsgetation growing in inlet/outlet pipe No vegetation or root growth present.
joinq that is more than six inchsa tall and
less than six inches apart.
Pollution Nonflammabb chemicals of mors than No pollution present other than surface
t/2 cubic foot per thrse fest of basin film.
length.
�J l
p_5 1/90
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 5 - CATCH BASINS (Continued)
�- Mal�nano� CondHlon�NRNn M�M�Nn�r�w R�sults Fxp�o�d
Cwnpoe�K D�f�ot Is NNd�d Wh�n Malnbnana Is PKfomNd
Catch Baain Cowr C,owr Not in Plaw Cowr is rMairp or ony p�Nalty in plac�. Gtch basin oowr is cloasd.
My op�n c�ch basin rpuires
ma1�LKw�a.
Locking M�chaniam cannot b�opM�d by on� M�chanism op�ns with proper tools.
�aniun Not mai�ano�p�aon with propK tools.
Worlclnfl Bolb irtEo 1nm�haw las than 1/2 inch
of thnad.
Cov�r pifhcuR to O��maiM�nana pKson cannot romow Co�sr can bs romoved by ons
Rsmow lid aftK applying 80 Ibs.of lift; intsnt is maintenance p�rson.
kNp cowr from s�alinp oit axass to
maintMana.
Ladde� Ladd�r Rungs Ladd�r is unsafs due to missing runqs, Ladder maets dasign standards and
Unsaf� misaliqnment,rust,cracks, or sharp allows maintenance person sate axess.
ed�es.
Metal Grates Grate with opsning wid�r than 7/8 inch. Grate opaninps maet design standards.
(f applicable)
Trash and Debris Trash and debris that is blocking rtwre Grats free of trash and debris.
than 2096 of flrate surtacs.
Damaged or Grate missing or broken member(s)of Grate is in place and meets design
Missing the grate. standards.
— 1 l�
a-� i/90
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 6 - DEBRIS BARRIERS (e.g. Trash RaCks)
MalnO�nanw CondMbn�Wh�n WlnMmnw R�sults Esp�cMd
CompoMnt ON�et Is NMd�d YMh�n �Aal�nar�b PKfonn�d
General Trash and D�bris Tnsh or d�bris that is Mu�pfnp mon BartIM dwr to roceiw capac�ty flow.
than 2076 of tM op�►irps in tM barriK.
nnew �.d/�wa�ny �e.M an of shap.m«.n,an 3 3ears�ptac.wkl,no b.nas mon than
�
8ara an mfssiny or�rMin barti�r b Bars in plac�accordinp to d�sign.
missinp.
Bars an loos�and rust is caudnp 50% Fi�pair or nplacs bartiK M design
det�rbratlon to arry part of barriK. sundards.
. .
.� ,
D��
A-7 1/9U
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 7 - ENERGY DISSIPATORS
Maln��nana CondNlon�1Mh�n Malnt�nano� R�sufts Exp�cad
CompoMnt D�Net b li��d�d 1Alh�n �Aaint��►ana ia PKtorm�d
mal:
Rodc Pad t�Usslnp or hAcv+d Only on�IayK ot rock�xists at�ow natiw Rsplaa rocks to d�si�n standard.
Rodc soil in ana fiw sqwn fNt or larfler,or
arry ezpown of natM soil.
Disp�rsion Tnnch Plps Pluyped with AccumulaUd s�dlm�M that ucaeds 20% Pip�deaned/flushed so that it matches
Ssdiment af th�desiQn depeh. desipn.
Not IXscharqinfl Viwal evid�w of watsr diacharpl�at Trench must b�rsdesiflned or rebuik to
Water Propery conwmrated poi�s along trMch (normal standud.
condition is a'shset flow'of watsr along
trench). Int�nt is to prevent�rosion
damaps.
Perforations Over 1/2 of perforaUons in pipe are qean or raplace pertorated pipe.
Pluppsd plugpsd with debris and sadiment.
Watar Flows Out MaiMenancs person observes water Facility must be rebuiR or redesigned to
Top af'Distributor' flowin9 out during any storm Isss than standards.
Catch 8asin ths dssign storm or it is causing or
appears liksly to cause damags.
Receiving Area Water in rsceiving area is causing or has No danger of landslides.
Over-Saturated potantial of causing landslide problema.
Intemal:
Manhole/Chamber Wom or Damaged Structurs dissipating flow deterioratsa to Replace structure to design standards.
Posts, Battlas, 1/2 or original sizs or any concentrated
Sides ot Chamber wom spot excseding one square foot
which would maks sttucture unsound.
Othar Defects See'Catch Basins' Standard No. 5 See'Catch 8asins' Standard No. 5
� ��
_�
— '✓��
A-8 1/rI0
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
NO. 10 - CONVEYANCE SYSTEMS (Pipes & Ditches)
Nlalnbeanc� CondHlons NRNn Malnbnano� R�wlb Exp�et�d
Cwnpo�t D�bct Is NNd�d VYh�n Mak�t�nana b PKform�d
Pip�s S�dlm�nt�D�bris Accumulated s�dimKrt that exos�da 2096 Pips d�an�d of all s�diment and debris.
of the diam�tK of the pip�.
V�pstatbn Vp�tttlon that reduas fn�mov�ems�t of All vprtitlon romowd so watet flows
wat�t�rouph pipes. itssly throuflh pipes.
pamaped Proosctiw coatiny is damaged;rust is P9ps ropaired or replacsd.
causing moro than 5096 deterioration to
�Y P��P�P�•
My derh that dscreasss the cross ssction Pip�repaind or roplaced.
ana of pips by more than ZO%.
Open Ditches Tnsh �Debris Trash and debris exceeds 1 cubic toot Trash and debris dsarsd from ditches.
per 1,000 squu�test of ditch and slopes.
SedimeM Axumulated sedimeM that excseds 2096 Ditcfi dsaned/flushed of all ssdYmsnt and
ot ths design depth. debris so that it matches desiyn.
Vegetation Vegetation that reduces free movement oi Water flows hesly through ditches.
water through ditches.
Eroalon Damaqs to Sss'Ponds'Standud No. 1 Ses'Ponds' Standard No. 1
Slopes
Rock Lining Out of Maintenance person can see native soil Replacs rxks to design standard.
Placs or Missing (M beneath the rxk Iining.
Applicable)
Catch Basina Sss'Gtch Basins" Standard No.5 See'Catch Basins'Standard No. 5
Debria Barriers Sse'Debris Barriers" Standard No. 6 Ses'Debris Barriers'Standard No.6
(e.p.,Trash Rack)
i
�_,
�'V
A-11 � '�
KING COUNTY, WASHINGTON� SURFACE WATER DESIGN MANUAL
NO. 11 - GROUNDS (Landscaping)
Malrtanano� Condltlons VNwn M�M�Mnr�a R�auRs Exp�e�d
Compornnt D�Not Is NNd�d Wh�n Mairr�anw la PKMrm�d
G�nKal IAN�ds VYNds�rowinp in ma�than 2096 of th� VW�ds pnssrtit in I�ss than 5%ot th�
M�P��s1 lar►dscaP�d ana�tn�s and�hrubs only). iandscap�d ana.
S+htY�� MY P�^a a P�+�NY or othK No poitonous ve��tation prossnt in a
poiwnous v�p�Uor�. landsCapsd aroa.
' Tra�h or Litt�r Pap�r,an,bottla.�obilin�mors than t Ma dear of Iftter.
cubic foot within a landscaped area(vses
and shrubs ottlyj of 1,000 aquan feet
Trses and Shrubs Damaqs Um�s or parts of Ve�s or shrubs that an Tnes and shrubs wkh Isss than 5%of the
split ot brok�n which afMci mors than total foliage with split or broken limbs.
259�of the toL!foliaq�of th�Vee ot
shrub.
Trses or ehrubs that havs been blown Trss or shrub in placs fres of injury.
down or knodced owr.
Trs�s or shrubs which ars not adaquatsly Trse or shrub in placs and adequataly
supported a ars leaning over,causing supportsd; romove any dead or diseased
expowrs of ths roots. Vees.
V� 1
A-12 1/90
KING COUNTY, WASHINGTON, SURFACE WA'TER DESIGN MANUAL
RETENTtON%DETENTION SUMMARY SHEET
� DevelopmeM oate
Location
ENGINEER DEVELOPER
Name Name
Firtn Frtn
Address Add�ess
Phone Phone
• Developed Site acres Number of Lots
• Number of Dete�tion Facilities On Site
• Detention provided in regional facility ❑
� Regional Facility bcation
• No detention required �
Acceptable receiving wate�s
• Downstream Drainage Basins
Immediate Major Basin
Basin A
Basin B
Basin C
Basin D
TOTAL INDIVIDUAL BAS1N
A B C D
Drainage Basin(s)
Onsite Area
Offsite Area
Type of Storage Facitity
Live Storage Volume
Predeveloped Runoff Rate 2 year
10 year
Postdeveloped Runoff Rate 100 year
2 year
10 year
Developed Q 100 year
Type of Restriction
Size of Or'rf'�ce/Restriction
Or'rficeJRestriction No.1
Noz
No.3
n�o.a �..�,D
No.5
�� . 1/'90
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
RETENTIOWDETENTION SUMMARY SHEET SKETCH
All retentioNdete�ion summary sheets must include a sketch prepared to the tolbwing criteria:
1. Heading for the drawings should be located at the bop of the sk�etch. Pre-
ferably at the top right t�ac�d corner.
Zhe heading sl�ould oontain:
- North arrow point up or to the left
— D9�
- Plat name or Short Plat n�nber
- Date drawn or updated
- Address (nearest the site)
- Thomas Brothers page and grid number
- Maintenance Division n�nber
2. Label CB's and I�i's with the plan and profile designation.
Label the oontrol structrue in writing or abbreviate with C.S. or
O.W.S.
3. Pipes - indicate:
- Pipe size
- Pipe lenghth
- Flow direction
- Use a single, heavyw�ight line
Example: ��o-��' _r-Ua,.�
4. Tanks - use a double, heavyweight li`e�and indicate the size
Example: �Z„
5. Access Roads
- Outl ine the 1 imi ts of the road
- Fill the outline with dots if the road is grav�el. Label in writing if
it is another surface
6. Other Standard Symt�ols:
- Bollarc3s ��•_ a�i�
- FencesP -�f��-�Y�—
- Di tches �c^--�o-�-�o
7. Label trash racks in writing. �,_�2,
E)cc�tilple: }ros}� raeic ,,/•-'—i
8. Label all streets with the actual street sign desigaation. Zf you don't
kncxa the actual street name, consult the plat map.
9. Znclude easen�ents and lot lines or tract limits when possible.
10. Arrange all the labeling or writing to read frnm left ta right or fran
bottaa to tAp with reference t�o a p�ronerly oriented heading.
11. Indicate driveways or features that may impact our acoess, maintenance or
replacement. .
�-u
RD-2 1/9U
,- �-�, After recording return to:
;
DECLARATION OF COYENANT
IN CONSIDERATION OF the approved King County ,
permit for application No.
relating to real property legally described as follows:
The undersigned as Grantor(s) , declares that the above described property
is hereby subject an easement for a natural or constructed conveyance system
and hereby dedicates, covenants and agrees as follows:
1 . King County shall have the right to ingress and egress over those
portions not contained in Exhibit "A" to access such easement area for inspec-
tion of and to reasonably monitor the system for performance, operational
flows, or defects in accordance with and [as presented in King County Code
Section 9.04. 120] .
2. If King County determines that maintenance or repair work is
r?quired to be done to the system, the Manager of the Surface Water Management
Division of the Department of Public Works shall give notice of the specific
maintenance and/or repair required pursuant to K.C.C. 9.04.030. The Manager
shall also set a reasonable time in which such work is to be completed by the
,`
Grantor(s) , its heirs, successors or assigns. If the above required
08:M[16 - 1 - ��r,� /
!/�
maintenance and/or repair is not completed within the time set by the Manager, .
�
the County may perform the required maintenance and/or repair. Written notice
will be sent to the Grantor(s) stating the County's intention to perform such
maintenance. Maintenance work will not commence until at least seven (7) days
� after such notice is mailed. If, within the sole discretion of the Surface
Water Management Division Manager, there exists an imminent or present danger,
said seven (7) day notice period will be waived and maintenance and/or repair
' work will begin immediately.
3. If at any time King County reasonably determines that any existing
retention/detention system creates any of the conditions listed in
K.C.C. 9.04.030 and herein incorporated by reference, the Surface '�1a� - �
Management Division Manager may take measures specified therein.
4. The Grantor(s) shall assume all responsibility for the cost of any
maintenance and for repairs to the system. Such responsibility shall include
reimbursement to the County within thirty (30) days of the receipt of the
invoice for any such work performed. Overdue payments will require payment of
interest at the current legal rate as liquidated damages. If legal action
ensues, the prevailing party is entitled to costs or fees.
5. The Grantor(s) is (are) hereby required to obtain written approval
from the Surface Water Management Division Manager of the King County
Department of Public Works prior to filling, piping, cutting, or removing veg-
etation (except in routine landscape maintenance) in open vegetated drainage
facilities (such as swales, channels, ditches, ponds, pond, etc. ), or perform-
ing any alterations- or modifications to the drainage facilities contained
within said drainage easement. Any notice or consent required to be given or
D8:lII16 - 2 -
��LJ
otherwise provided for by the provisions of this Agreement shall be effective �,
� � i
upon personal delivery, or three (3) days after mailing by Certified Mail , '
return receipt requested.
6. This Agreement constitutes the entire agreement between the parties,
and supersedes all prior discussions, negotiations, and all agreements whatso-
ever whether oral or written. I'
' This covenant is intended to protect the value of desirability of the !
real property described above, and shall insure to the benefit all the citi- I,
zens of King County, and shall be binding on all heirs, successors and I
assigns. I,
OWNER
OWNER
STATE OF WASHINGTON )
COUNTY OF KING ) ss.
On this date personally appeared before me:
, to me known to be the
individual (s) described in and who executed the within and fqregoing instru-
ment and acknowledged that they signed the same as their free and voluntary
act and deed, for the uses and purposes .therein stated.
Given under my hand and official seal this day of
, 199
NOTARY PUBLIC in and for the State of
Washington, residing at �
My Commission Expires:
:.
...�-
os:�t�6 - 3 - D-��
I !
APPENDIX E
City of Renton Mitigated Deternunation of Non-Significance ........................E-1
�
�,�:
I
�;
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4 ,
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� .. ' ;� ,.� CITY OF RENTON
' .�l Planning/Building/Public Works Department
3eabe T�er.Mr:os G�7immermaa P��.dminisbratoc
January 06, 2000
Mr. Paul Casey,A.1.A.
The Casey Group Architects
10116—36'�Avenue Court SW, Suite�109
Lakewood,WA 98499
SUBJECT: Normandy Ridge
Project No. LUA-99-136,SA-A,V-B,ECF
Dear Mr. Casey:
This letter is written on behalf of the Environmentai Review Committee (ERC) and is to advise you that
they have completed their review of the subject project. The ERC, on January 04, 2000, issued a
;hreshold Determination of Non-Significance-Mitigated with Mitigation Measures. See the enclosed
ti1itigation Measures document.
Appeals of either the environmental determination [RCW 43.21.0075(3), WAC 197-11-680] and/or the
land use decision must be filed in writing on or before 5:00 PM January 24, 2000. If no appeals are filed
by this date, both actions will become final. Appeals must be filed in writing together with the required
�75.00 application fee with: Hearing Examiner, City of Renton, 1055 South Grady Way, Renton, WA
98055. Appeals to the Examiner are governed by City of Renton Municipal Code Section 4-8-11 B.
Additional information regarding the appeal process may be obt2ined from ;he Renton City C1erk's Office,
(425)-430-6510.
�he preceding info�mation wiil assist you in planning for implementation of your projec; and enable you to
exercise yo�r appeal rights more fuliy, if you choose to do so. if you have any questions or desire I
clarification of the above, please cail me at (425)430-7219.
For the Environmental Review Committee, I
����� I
Peter Rosen I
Project Manager
cc: Mr. & Mrs. Ervm Yoder/O
wners II
Mr. & Mrs. G. Warren Diamond/Owners
Mr. Stephen Berg/SEB, Inc.
Mr. Jack Martz �
Enclosure
dnsmletter G��
1055 South Grady Way- Renton,Washington 98055
�This papor concams 50:recyc�otl matonal,209.posl consurt�er
CITY OF RENTON
DETERMINATION OF NON-SIGNIFICANCE
(MITIGATED)
', MITIGATION MEASURES AND CONDITIONS
APPLICATION NO(S): LUA-99-136,SA-A,V-B,ECF
4 APPLICANT: SEB, Inc
PROJECT NAME: Normandy Ridge
DESCRIPTION OF PROPOSAL: Proposal to construct 83 multi-family residentiai units,
consisting of 42 ground-related townhouses and 41 muiti-family stacked flats.Access is proposed via a
driveway off Talbot Road S. A secondary, emergency access also connects to Talbot Road S. A total of
190 parking spaces are proposed; with 64 garage spaces and 64 driveway parking spaces for the
townhouses, and 62 parking stalls in carports for the multi-family flats. 27 guest parking stalfs are also
provided, with 24 stalis as parallel parking along the internal streets and 3 stalis of head-in parking
associated with the recreation building. There are five Category 3 wetlands identified on the site,
ranging in size from 475 sq. ft. to 2,048 sq. ft. The City does not regulate Category 3 wetlands that are
less than 5,000 sq. ft. and hydrologically isolated. The proposal would fill the wetlands and
compensatory mitigation is not required. A drainage channel/creek bisects the site and the proposal
includes a 25-foot stream buffer. The proposed internal street crosses the stream in 2 locations. A
variance from the Land Clearing and Tree Cutting Ordinance was approved by the Renton Board of
Adjustments to allow the two street crossings to intrude into the 25-foot required buffer.
LOCATION OF PROPOSAL: 4914 Talbot Road South
MITIGATION MEASURES:
1. The applicant shall install a silt fence along the downslope perimeter of the area that is to be
dist�rbed. The silt fence shall be in place before clearing and grading is initiated, and shall be
construc;ed in conformance with the specifications presented in Section D.4.3.; of the King
County SurFace Water Design Manual, Appendix D. This will be required during the construction
of both off-site and on-site improvements as well as building construction.
2. Shallow drainage swafes shall be constructed to intercept surface water flow and route the flow
away from the construction area to a stabilized discharge point. Vegetation growth shall be
established in the ditch by seeding or placing sod. Depending on site grades, it may be
necessary to line the ditch with rock to protect the ditch from erosion and to reduce flow rates.
The design and construction or drainage s�riales shall conform to the specifications presented in
Section 4.4.1 of the SW DM. Temporary pipe systems can also be used to convey stormwater
across the site. This will be required during the construction of both off-site and on-site
improvements as well as building construction.
3. The project contractor shall perform daily review ard maintenance of all erosion and
sedimentation control measures at the site during the construction of both off-site and on-site
improvements as well as building construction.
4. Weekly reports on the status and condi6on of the erosion control plan with any recommendations
of change or revision to maintenancE schedules or installation shall be submitted by the Project
Engineer of record to the public works inspector. Certification of the installation, maintenance
and proper removal of the erosion control facilities shall be required prior to final approval of
construction permits.
. � �-Z
' Nortnandy Ridge
� LUA-99-136,SA-A,V-B,ECF
Mitigation Measures 8 Conditions(continued)
Page 2 of 2 �
5. The applicant shall provide extra stormwater detention on-site with a 30% safety factor beyond
the normal requirements for the 2, 10 and 100-year storm events to minimize additional
downstream flooding problems. Plans for this facility shall be submitted to the satisfaction of the
Development Services Division prior to the issuance of consUuction permits.
6. The applicant shall pay the appropriate Fire Mitigation Fee equal to $388 per multi-family unit and
$0.52 per square foot for the recreation building. The Fire Mitigation Fee is payable prior to the
issuance of building permits.
7. The applicant shall be required to pay a Traffic Mitigation Fee of $75 for each average daily trip
associated with the project. The traffic mitigation fee is estimated to be $35,762.25. This fee is
payable prior to the issuance of building permits.
8. The applicant shall pay a Park's Department mitigation fee of �354.51 per multi-family dwelling
unit. The value of the proposed recreation building may be credited for up to one-third of the total
parks mitigation fee. The required mitigation fee shall be subject to the approval of the Parks
Department and the Development Services Division, and the fee shall be paid prior to the
issuance of building permits.
The Site Plan for Normandy Ridge, File No. LUA-99-136, SA-A, ECF, is approved subject to
the following conditions.
1) The applicant shall submit details of the street lighting, mailboxes, and signage in order to qualify
for the R-14 bonus provision. The details shall be subject to the approval of the Development
Services Division, prior to issuance of building permits.
2) The applicant shall revise the site plan to eliminate the carport to the east of Building 9 because
the carport does not meet the front setback requirement for detached accessory struc;ures. The
revised site plan shall be subjec; to :he Gpproval of the Cevelopment Services Civisicn, prior to
issuance ci building permits.
3) The applicant shall record a restrictive covenant or other device acceptable to the City that
assigns tandem parking spaces to the exclusive use of specific dwelling units. The applicant
shall also install signs at the garages indicating that the driveway apron is reserved for use by the
unit occupant. The restrictive covenant shall be approved by the Development Services Division
prior to recording. Recording of the covenart shall occur prior to final occupancy permits.
���
CITY OF RENTON
DETERMINATION OF NON-SIGNIFICANCE
(MITIGATED)
ADVISORY NOTES
APPLICATION NO(S): LUA-99-136,SA-A,V-B,ECF
APPLICANT: SEB, Inc
PROJECT NAAAE: Normandy Ridge
DESCRIPTION OF PROPOSAL: Proposaf to construct 83 muiti-famly residentiat units.
consisting of 42 ground-related townhouses and 41 muiti-family stacked flats. Access is proposed via a
d�iveway off Talbot Road S. A secondary, emergency access also connects to Talbot Road S. A total
of 190 parking spaces are proposed; with 64 garage spaces and 64 driveway parking spaces for the
townhouses, and 62 parking stalls in carports for the multi-family flats. 27 guest parking stalls are also
provided, with 24 stalls as parallel parking along the internal streets and 3 stalls of head-in parking
associated with the recreation building. There are five Category 3 wetlands identified on the site,
ranging in size from 475 sq. ft. to 2,048 sq. ft. The City does not regulate Category 3 wetlands that are
less than S,OQO sq. ft. and hydrologically isolated. The proposal would fill the wetlands and
� compensatory mitigation is not required. A drainage channel/creek bisects the site and the proposal
inclu�es a 25-foot stream buffer. The proposed internal street crosses the stream in 2 locations. A
variance from the Land Clearing and Tree Cutting Ordinance was approved by the Renton Board of
Adjustments to allow the two street crossings to intrude into the 25-foot required buffer.
LOCATION OF PROPOSAL: 4914 Talbot Road South .
Advisory Notes fo Applicant:
The following notes are supplemental information provided in conjunciion with the
environmental defermination. Because these notes are provided as information only, they are
not subject to the appea!process for envrronmental determinafions. �
BUILDING
Follow geotechnical recommendations.
F1RE
1. The preliminary fire flow required is 3,000 GPM which requires one fire hydrant within 150 feet of
the building and two additional hydrants within 300 feet of the building.
2. Secondary access roadway is required. Bollards cannot be used to control traffic. An approved
gate or chain and padlock are allowed ta restrict traffic on the emergency access. All roadways 20-
feet in width are required to be marked as"Fire Lane, No Parking."
3. All buildings two stoaes and five or more units are required to be sprinklered. Central station
monitored fire alarm systems are required in all buildings by City Ordinance. Separate plans and
permits are required for the sprinkler and fire alarm systems.
PLAN REVIEW
SEW ER
• There is an existing 8" sewer main in Talbot Road available for this site. Most of the internal sewer
system will be private, but constructed to City main line standards. A portion of the main may be
required to be public to provide future service east of the site. This would required a minimum 15 foot
easement, which would extend to the easterly property line. The main will not be required beyond the
developed portion of the site.
• System Development Charges (to be paid to the City, for Soos Creek Sewer District) will be required
for this project(approximately$1835 per unit).
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Advisory Notes (continued) �
Page 2 of 3
, WATER
• A water main loop extension will be required for this project. To meet the fire flow requirement of
3000 gpm set by the Fire Department, a minimum 10"main must be provided through the site.
Easements will be required for all on-site water mains and hydrants (minimum of 15 feet in width).
• Backflow prevention devices will be required for irrigation and fire protection systems.
• Depending on fire flow requirements, additional hydrants will be required.
• System Development Charges will be required for this project (�510 per unit). There are SAD
($0.048 per sq. ft.) and Latecomers Fees (�0.0262 per sq. ft..) also due upon development of this
site.
DRAINAGE
• A conceptual drainage plan and drainage repo�t has been submitted with the site plan application for
this project. The conceptual drainage plan includes provisions for detention and water quality
treatment in compliance with the requirements of the KCSWM.
• Due to downstream flooding problems in this drainage basin, staff recommends a SEPA condition for
extra detention for the on-site drainage system. The recommendation will for detention through the
100 year storm event with a 30% safety fac;or. It appears that an HPA permit is also required for this
project, which will incfude this additional detention standard as a permit condition. The conceptual
��iN�ce P[.��submitted with this application complies with this additional detention requirement.
• System Development Charges will be required for this project (�0.129 per sq. ft.. of new impervious
surface)
STREETIMPROVEMENTS
• Talbot Road South adjacent to the site must be improved with curb, gutters, sidewalks, street lighting,
new paving from the edge of existing pavement to the new gutter, and drainage improvements for the
new street improvements.
• This zone allows for condominium style development (i.e. no separate platted lots), but must meet the
development standards of a shadow plat. The shadow plat provided demonstrates the equivalent of
standard right-of-way widths throu5h the project, with a interccnnected vehicular and pedestrian
system. The praject provides equivalent street improvements internal to the site, including adequate
pavement width, curos, drainage, sidewalks and tumarounds for dead-end street sections. The
standard street design requirements for this type of project has been modified to allow for sidewalks
along one side of the street only, pavement widths of 20 feet where parking is precluded by driveways
, on both sides of the street, and 28 feet of pavement with parking limited to one side of the street
where parallel parking is feasible.
• Street lighting must be provided on the private street sections, meeting or exceeding the lighting
levels established in City Code. This systern will be privately owned and maintained.
GENERAL _
• All required utility, drainage and street improvements will require separate plan submittals prepared
according to City of Renton drafting standards by a registered Civil Engineer. The construction perrtiit
application must include a itemized cost estimate for these improvements. The fee for review and
inspection of these improvements is 5% of the first $100,000 of the estimated construction costs; 4%
of anything over $100,00 but less than $200,000, and 3% of anything over $200,000. Half of this fee
must be paid upon application for building and construction permits, and the remainder when the
permits are issued. There may be additional fees for water service related expenses.
PARKS
Recommend 5-foot bike lanes striped and signed on Talbot Road S.
Ensure that new street trees are not planted under existing electric/telephone lines.
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Advisory Notes (continued)
Page 3 of 3
POLICE
Estimate 76.36 police calls for service annually, based on the number and type of residential dwelling
units. Many of these estimated calls will occur during the construction phase, and will be incidents such
I as Trespass, Commercial Burglary and Theft of building materials and tools. To help prevent these
crimes, the site will need to have temporary, security fencing in place and security lighting. Post the
correct No Trespass signs along the fencing (�efer to the attached flier with the correct wording).
Other properties along Talbot Road experienced crime problems such as burglary, theft, trespass and
even a drive-by shooting at one of the construction traile�s. Other sites felt the need to use the services
of off-duty police and private security companies for on-site patrols of the area while it was being built.
All building materials and tools will need to be kept locked up when not in use, and any construction site
office trailer will need to have metal doors with dead-bolt locks, metal bars over the windows, and all
office machinery will need to have the serial numbers recorded to aid in recovery in the event of theft.
On some of the proposed units, there are windows adjacent to the entry doors. These windows will
either need to have reinforced glass in place, or an application of security film. Otherwise, it would be
too easy `or a burglar to break the glass, put his hand through the window, unfock the front door and
gain entry to individual units. Each door to each unit will need to be solid core wood or metal, with
dead-bolt locks and peepholes for security of the residents. Each unit will need to have the address
clearly posted, of a color that contrasts strongly with the color of the unit, and at least 6" in height, to aid '
responding emergency personnel. Since this development has one entry/exit, recommend the
installation of a security gate to limit access only to residents and guests.
PLANNING
Only rockeries or retaining walls that are less than 4-feet in height may extend into required yard
setbacks. The applicant shall require variance approval if the rockery walls shown on the site plan that
extend into the required yard setbacks exceed 4-feet in height.
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