HomeMy WebLinkAboutMisc. CONCEPT ENGINEERING, INC.
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-Issaquah, Washington 98027
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Wetland Delineation Report
For The
Jonah-Kai Hancock Short Plat
Located At:
11025 I 48 1h Avenue SE
Renton, WA 98059
Tax Parcel Number:
032305-9020
Report Prepared For:
Jonah-Kai Hancock
I 0025 I 48'h A venue SE
Renton, WA 98059
(206) 234-9673
Report Dated:
August 29, 2007
Concept Engineering, Inc.
Job Number:
25332
Conducted and Prepared By:
Chris Holcomb
Certified Wetland Specialist
Report Reviewed By:
Mark Rigos, P.E.
Certified Wetland Biologist
CIVIL ENGINEERING I SURVEYING/ LAND USE PLANNING
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Wetland Delineation Report
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TABLE OF CONTENTS
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1.0 PROJECT OVERVIEW AND SITE DESCRIPTION ....................................................... 1
2.0 METHODOLOGY, AUTHORITY AND LIMITATIONS ................................................ l
3.0 WETLAND DEFINITION AND METHODS ................................................................... 2
4.0 VEGETATION RES UL TS ................................................................................................ .4
5.0 SOILS RESULTS ............................................................................................................... 5
6.0 HYDROLOGY RESULTS ................................................................................................. 6
7.0 WETLAND DETERMINATION ....................................................................................... 6
8.0 IMPACT ASSESSMENT AND RECOMMENDATIONS ................................................ 8
9.0 REFERENCES ................................................................................................................... 9
Exhibit A:
Exhibit B:
Exhibit C:
Exhibit D:
Exhibit E:
Exhibit F:
Exhibit G:
APPENDIX
Vicinity Map, Aerial Photo, Wetland Sketch and SCS Soil Map
King County Critical Areas iMaps
Wetland Data Forms
Renton Municipal Code Excerpts
Color Photographs
Wetland Flagging Survey (Attached in Pocket)
Certifications
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Wetland Delineation Report
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1.0 PROJECT OVERVIEW AND SITE DESCRIPTION
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This Wetland Delineation Report was prepared to assess, delineate and rate the wetlands and a stream
located on tax parcel 032305-9020 in Renton, Washington. The parcel's legal location is in the SE Y.i of
Section 3 in Township 23 North and Range 5 East W.M. The site is rectangular in shape and .81 acres.
Directions to the site are as follows: from Interstate 405, take Exit 5 in Renton and drive east about 2.5
miles on State Rout 900 (NE Park Drive). Tum right onto 148'h Avenue SE and drive roughly 400 feet,
passing the junction with SE 111 th Street, and turn right into the large gravel driveway at 11025 148th St
SE. This is also where the client lives.
Our client and property owner, Jonah-Kai Hancock, is evaluating his parcel for residential development.
This report is the culmination of wetland delineation, rating, stream ordinary high water mark (OHWM)
flagging and surveying done by Concept Engineering Inc. Mark Rigos visited and rated a wetland on
the site on November 17, 2005. At this time, the parcel was within unincorporated King County. The
City of Renton recently incorporated the parcel so Renton Municipal Code regulates land use on the site.
Chris Holcomb delineated two wetlands and flagged the OHWM of the stream on May 24 and 25, 2007.
The weather on both days was around 68°F with clear skies. The preceding fall and winter had been
wetter than average.
The site is located in a mildly hilly area of northeast Renton. May Valley and May Creek are about 1/8-
mile northeast of the site. The site is bordered on the west and north by a housing development that was
constructed within the last three years. Houses to the south and east are on larger lots and are older.
There are stands of large trees northeast and southeast of the site: otherwise the area has few trees. The
eastern 2/3 of the site has a house, carport and lawn. The western I /3 of the site is where the wetlands
and stream discussed in this report are located and this area is covered in a variety of un-mowed grasses,
sedges and rushes. One of the wetlands, Wetland W, includes a small area of alders and Himalayan
blackberry (See Aerial Photo and Wetland Sketch in Exhibit A of the Appendix).
Two wetlands and one seasonal stream were found on the site. Wetland Wis located in the northwest part
of the site and Wetland Y is located in the southwest part of the site. The wetlands' borders were marked
with numbered pink flags that had the words 'WETLAND BOUNDARY' printed on them. Wetland W
has 17 flags and Wetland Y has 6 flags. Sample points were established inside and outside of the
wetlands so that the differences in hydrology, soils, and vegetation between the wetland and adjacent
upland could be demonstrated. The 6 sample points were marked with blue flagging. The stream's
OHWM was marked with blue and white striped flagging. Nine flags were hung on both the west bank
and the east bank. The stream enters the site from the south and leaves it through a culvert on the north.
2.0 METHODOLOGY, AUTHORITY AND LIMITATIONS
Methodology:
The wetland determination was performed using the Routine Level 2 Methodology as described in the
Washington State Wetlands Identification and Delineation Manual (Washington State Department of
Ecology, March 1997). King County DOES adopted this Delineation Manual as an appropriate technical
basis for determining the presence of wetlands. The Routine Level 2 Methodology is used when there is
insufficient information already available to characterize the vegetation, soils and hydrology of the project
area.
The wetland determination was based on the presence of the three criteria for jurisdictional wetlands:
hydrophytic vegetation, hydric soils and wetland hydrology. All three criteria must be present in order to
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classify an area as a wetland. This wetland determination included a review of the King County Sensitive
Areas Map Folio for wetlands. This map showed the presence of wetlands on or near this site. However,
this map is intended as a graphic aid only, and is not a legal document.
Authority:
This wetland determination is in accordance with Section 404 of the Clean Water Act, the objective of
which is to "maintain and restore the chemical, physical, and biological integrity of the waters of the
United States" (COE, 1987).
Limitations:
Wetlands are subject to seasonal and annual variation. Wetland determinations and delineations are not
final until approved by regulatory agencies and/ or jurisdictions.
3.0 WETLAND DEFINITION AND METHODS
A wetland is defined as an area that is inundated or saturated by surface water or groundwater at a
frequency and duration sufficient to support, and that under normal circumstances do support, a
prevalence of vegetation typically adapted for life in saturated soil conditions. As stated from the Corps
of Engineers Wetlands Delineation Manual (COE, 1987), wetlands are required to have the following
three criteria:
A. The site supports predominately hydrophytic (wetland) vegetation.
The dominant vegetation are determined using the 50/20 rule as described in the
1997 Washington State Wetlands Identification and Delineation Manual. Hydrophytic vegetation
has adaptations that allow these species to survive in saturated and / or inundated environments.
Hydrophytic vegetation exists at a site if greater than 50% of dominant species are classified as
FAC, FAC+, FACW, FACW+, or OBL. The indicator status of wetland plants is classified
according to the USFWS National Wetlands Inventory and National Plant List Panel (Reed,
1988). Less common indicators of hydrologic vegetation include visual observation of plant
species growing in areas of prolonged inundation and / or soil saturation, morphological
adaptations, technical literature, physiological adaptations, and reproductive adaptations. As
shown on the following page, an indicator status is applied to each species according to its
probability of occurring in wetlands.
~ndicator Category
Obligate Wetland Plants
Facultative Wetland Plants
Facultative Plants
Facultative Upland Plants
Obligate Upland Plants
Not inventoried in the Manual
Symbol
OBL
FACW
FAC
FACU
UPL
NI
Occurrence in Wetland~
>99%
67-99%
34-67%
1-33%
<1%
Note: F ACW, F AC, and F ACU have + and -values to represent species near the wetter end of
the spectrum ( +) and the drier end of the spectrum (-).
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B. The substrate is predominantly undrained hydric soil.
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Hydric soils ( soils formed under wetland conditions) are a positive indicator of wetland
conditions. Hydric soil is defined as a soil "that in its undrained condition, is saturated, flooded,
or ponded long enough during the growing season to develop anaerobic conditions in the upper
part." (Soil Conservation Service, 1985). A preliminary determination ofhydric soils for a site is
made with reference to NRCS soil surveys (per county) and criteria established by The National
Technical Committee for Hydric Soils (NTCHS).
Hydric soil criteria are based on taxonomy, drainage, and permeability. However, NRCS
mapping units cover broad geographical areas and commonly don't include smaller inclusions of
non-hydric or hydric soils. Therefore, field confirmation is necessary. Field indicators of hydric
soils are examined from 18" soil pits. For non-sandy soils, indicators include presence of organic
soils (Histosols), histic epipedons, sulfidic material (hydrogen sulfide), aquic or peraquic
moisture regime, reducing soil conditions, hydric soil colors, verified soils appearing on the
NTCHS hydric soils list, and presence of iron and manganese concretions. Hydric soil colors are
analyzed immediately below the A-horizon or to a depth of 10" (whichever is shallower). Hydric
soils include gleyed (gray) soils, low chroma soils in an unmottled matrix, or soils with high
chroma mottles within a low chroma matrix. Mottles (redoxymorphic features) are spots of
contrasting color. Gleyed color and chroma are determined with the Munsell Color Charts
(Munsell Color, 1992). Hydric soil indicators for sandy soils include high organic matter content
in the surface horizon, streaking of subsurface horizons by organic matter and/or spodic horizons.
C. The substrate is saturated by water or covered by shallow water at least periodically
during the growing season.
Typically, wetland hydrology occurs where the presence of water has an overriding influence on
vegetation and soils, resulting in the development of wetland soils and wetland plant
communities. Sites with wetland hydrology are periodically inundated and / or saturated during
at least part of the growing season. Wetland hydrology normally exists where topography directs
water into low relief areas dominated by soils with poor drainage characteristics. Areas
demonstrate wetland hydrology if soils are periodically inundated or saturated to the surface for a
sufficient duration during the growing season. "Sufficient duration" is defined as greater than
12.5% of growing season days that are consecutively seasonally inundated and/or saturated to the
surface. The growing season can either be defined by the number of frost-free days, or the period
during which the soil temperature at 19.7 inches is above biological zero (41 F). As a rule of
thumb, the mesic growing season for Western Washington lowlands extends 245 days from
March l to October 31 (Washington Department of Ecology, 1997). At each sample location,
primary wetland hydrology indicators such as inundation, saturation in the upper 12", water
marks, drift lines, sediment deposits and drainage patterns are noted.
Secondary indicators such as oxidized root channels, water-stained leaves, local survey data, FAC
neutral test, etc., are also considered in the determination of a positive indicator for wetland
hydrology.
4.0 VEGETATION RESULTS
Prevalent vegetation is characterized by the dominant species compnsmg the plant community.
Dominant plant species are those that contribute more to the character of a plant community than other
species present, as estimated or measured in terms of some ecological parameter. The two wetlands exist
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in an area that is dominated by herbaceous plants and some of these are invasive species. This area may
have been forested at one time. The central part of the property is regularly mowed and both wetlands
have small portions that extend into this area.
SP-I (Sample Point I) was located within Wetland W(Photo 3). Dominant vegetation included Kentucky
bluegrass (Poa pratensis -F AC), common velvetgrass (Holcus linatus -FAC) and slough sedge ( Carex
obnupta. -OBL). At this location, hydrophytic vegetation was present, because greater than 50% of the
dominant species were OBL, FACW or FAC.
SP-2 was located outside of Wetland W (Photo 4). Dominant vegetation included evergreen blackberry
(Rubus lacinatus -FACU), red clover (Trifolium pratense -FACU), common velvetgrass (Ho/us linatus
-F AC) and soft rush (Juncus effusus -FACW). Hydrophytic vegetation was not present because greater
than 50% of the dominant species were not OBL, FACW or FAC.
SP-3 was located within the west end of Wetland W (Photo 5). Dominant vegetation included soft rush
(Juncus effusus -FACW), red clover (Trifolium pratense -FACU) and common velvetgrass (Holcus
/inatus -FAC). At this location, hydrophytic vegetation was present, because greater than 50% of the
dominant species were OBL, FACW or FAC.
SP-4 was located outside of Wetland W (Photo 6). Dominant vegetation included common velvetgrass
(Holcus /inatus -FAC), red clover (Trifolium pratense -FACU), tall buttercup (Ranunculus acris -
FACW-) and soft rush (Juncus effusus -FACW). Hydrophytic vegetation was present because greater
than 50% of the dominant species were OBL, FACW or FAC.
SP-5 was located between Wetland Wand Wetland Y (Photo 7). Dominant vegetation included common
velvetgrass (Holcus linatus -FAC), red clover (Trifolium pratense -FAC), orchard morning glory
( Convo/vulus arvensis -NI) and tall buttercup (Ranunculus acris -F ACW-). At this location,
hydrophytic vegetation was present, because greater than 50% of the dominant species were OBL, F ACW
orFAC.
SP-6 was located within Wetland Y (Photo 8). Dominant vegetation included common velvetgrass
(Holcus linatus -FAC), red clover (Trifolium pratense -FACU), orchard morning glory (Convolvulus
arvensis -NI), curled dock (Rumex crispus -FAC) and tall buttercup (Ranunculus acris -FACW).
Hydrophytic vegetation was present because greater than 50% of the dominant species were OBL, FACW
orFAC.
For additional vegetation information, see the Wetland Data Forms located in Exhibit C of the Appendix.
s_o SOILS RESULTS
The USDA 's Soil Conservation Service (SCS) mapped the site as having Alderwood gravelly sandy loam
( AgC). Alderwood soils occur in areas where the topography was formed by glacial till and that were
later covered by coniferous forests. These soils are considered to be moderately well drained. This soil
type is not listed as hydric but it can adapt physical characteristics that make it hydric if it's saturated for
sufficient time each year.
We classified the onsite soils by their hue, value, and chroma. The first number and letters correspond to
the hue, the second number corresponds to the value, and the third number corresponds to the chroma.
The presence of reddish specks or patches (mottles) or pebble-like nodules may also be necessary for
considering weather or not soils are wetland soils. The soils throughout the site were quite variable but
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they were closely examined since much of the area was covered in hydrophytic vegetation. An area
northwest of Wetland W, for example, was covered in small soft rush plants but the soils were chroma 3.
They were also more compacted and had a higher quantity of rocks than the other soils on this part of the
site. The soils within the wetland displayed chromas of 1 or chromas of 2 with mottles. The soils in the
areas just outside of the wetlands displayed chromas of2 without mottles or chromas of 3. Sample Points
1, 3 and 6 had hydric soils and Sample Points 2, 4 and 5 lacked hydric soils. For additional soil
information, please see the SCS Soil Map in Exhibit A and the Wetland Data Forms located in Exhibit C
of the Appendix.
6.0 HYDROLOGY RESULTS
Wetlands can receive water from three sources: 1) surface runoff from precipitation, 2) the overflow of
rivers and creeks and 3) groundwater from below. Wetland hydrology indicators may include drainage
patterns, drift lines, sediment deposition, watermarks, stream gage data and flood predictions, historic
records, and visual observation of saturated soils and inundation. The 1987 Core of Engineers manual
requires inundation, flooding, or saturation to the surface for at least 5-12.5% of the growing season to
satisfy the hydrology requirements for jurisdictional wetlands (COE, 1987). Hydrological indicators
include primary indicators such as saturation in the upper 12 inches or inundation on the surface and
secondary indicators such as water stained leaves and the PAC-neutral test. Primary indicators are
preferable for determining wetlands and at least one of the primary indicators listed on the data form is
required to be checked in order for an area to meet the hydrology parameter for being a wetland. (See
Wetland Data Forms in Exhibit C of the Appendix)
Water enters the site from the stream, a shallow water table and precipitation. The stream flows from the
adjacent lot to the south and then flows between the maintained lawn and the grassy area where the two
wetlands are located. The stream appears to have been artificially created long ago. The stream leaves
the lowest part of the site by way of a 14-inch wide steel culvert (Photo 2) and eventually ends up in a
detention/retention pond north of the site. Jonah Kai Hancock (property owner) informed Chris Holcomb
that Wetland W had a few inundated areas during the winter and early spring. These may be the areas
where soft rush is particularly dominant. Water from the center and eastern ends of Wetland W likely
leaves the site through the culvert while water on its southwest comer probably slowly infiltrates.
Wetland Y lacks inundation. Water in Wetland Y seems to leave via the stream that borders its east
border.
Saturation in the upper 12 inches of soil was used to delineate the wetlands. Wetland W generally
displayed saturation from 8 to IO inches below the surface. Wetland Y generally had soils that were
saturated to a shallower depth.
For additional information, please see the Wetland Data Forms in Exhibit C of the Appendix.
7.0 WETLAND AND STREAM DETERMINATION
Stream Class and Wetland Category Information
Concept Engineering Inc. flagged the OHWM of the stream within the parcel. A stream's type is
determined by its size, whether or not it can be used by salmonids, whether or not it runs during the entire
year and whether or not it flows through an artificial channel. The stream appears to have been
artificially created long ago, possibly to drain areas to the south. Since it flows through an artificial
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channel, it is considered a Class 5 stream per Renton Municipal Code (RMC) 4-3-050.L.1.a.v (See
Renton Municipal Code Excerpts in Exhibit D of the Appendix.
Two small wetlands were delineated on the site. The larger wetland, Wetland w; is dominated by
herbaceous plants and has a gradual northeast aspect. The wetland has been significantly altered from its
natural state. The stream runs in an artificial channel through one end of it. It may have been forested at
one time, is used minimally by wildlife (it is surrounded by residential development) and has introduced
species like reed canarygrass, tall buttercup and Kentucky bluegrass. Fill and gravel may have been
added to the soils in the northwest part of the wetland. Because of these characteristics, it would be
considered a Category 3 wetland (RMC-4-3-050.M.l.a.iii). The smaller wetland, Wetland Y, has also
been significantly altered from its natural state. The stream runs through part of it. It was probably
forested at one time and has some introduced species like tall buttercup. Because of these factors it would
also be considered a Category 3 wetland.
Buffer Information
RMC does not regulate Class 5 streams (waters). These streams do not have buffers and can be altered
without permission (RMC 4-3-050.L.l).
RMC requires that wetland buffers surround wetlands so that habitat can be preserved and wetland
functions can be maintained. Category 3 wetlands are required to have 25-foot wetland buffers (RMC-4-
3-050.M.6.c). Category 3 wetland buffers are also required to be fully vegetated with native vegetation
(RMC 4-3-050.M.6.a.iii). In addition, a building setback line (BSBL) is required to extend 15 feet
beyond stream and wetland buffers.
Information on Altering Wetlands and Altering Buffer Widths
Wetland W and Wetland Y may qualify for an exemption from these regulations since they are category 3
wetlands and under 2200 square feet (RMC 4-3-050.Ml ). All exemptions are subject to independent
secondary review (RMC 4-3-050.F.7) and require a Letter of Exemption from the Director of Renton
Department of Public Works (RDPW) (RMC 4-3-050.C.5).
Wetland buffer widths can generally be altered by a variance. Buffer averaging and buffer reduction are
not options because the buffers can never be reduced to more than 25 feet (RMC 4-3-050.M.6.f.v) and the
standard width for category 3 wetlands is 25 feet. The wetland buffer can be reduced by obtaining a
variance (RMC-4-3-050.N). A variance may require the design of a mitigation plan for the wetland and
wetland buffer. There are three approaches to mitigation: creation of new wetlands, restoration of former
wetlands and enhancement of existing wetlands. These approaches are covered in subsections 8-15 in the
Renton Municipal Code excerpts (See Exhibit D of the Appendix).
8.0 IMPACT ASSESSMENT AND RECOMMENDATIONS
Wetlands have three primary functions. They improve water quality, as soils and leafy emergents act to
filter and bind water borne pollutants. They provide important water holding and flood storage functions
by slowly releasing storm runoff to rivers, thereby reducing the extent of downstream flooding. Wetlands
also provide important wildlife habitat for a large number of invertebrate, plant, and animal species.
Benefits to nearby human residents include buffering from surrounding development and opportunities
for enjoying native wildlife and vegetation.
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The wetlands on this site provide an integral role in each of the above functions. The wetland meets the
criteria of hydrophytic vegetation, hydric soils and wetland hydrology. The purpose of the wetland
delineation was to determine first, the existence of possible wetlands, and second, if they exist, their
locations and buffer widths.
I. Do not clear or grade within the required wetland and stream buffer without a city approved
buffer modification plan. The buffers of these wetlands can be reduced by obtaining a variance.
2. Do not fill the wetlands or alter them in other ways without a city-approved mitigation plan that
incorporates wetland creation, enhancement or a combination of these two approaches.
3. Ensure there is no significant increase or decrease in storm water runoff flow to the wetlands
generated from new impervious surface areas attributed to site development.
4. Optional: Remove non-native and invasive vegetation that exists in or near the wetland.
Himilayan blackberry, evergreen blackberry and tall buttercup are three invasive species found on
this site. This would be a good measure for a wetland I wetland buffer enhancement plan.
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9.0 REFERENCES
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8129107
Chinn, Richard. 2002. Wetland Delineation & Management Training Manual & Reference, Richard Chinn
Environmental Training. Pompano Beach, Florida.
COE. 1987. Corps of Engineers Wetlands Delineation Manual, Technical Information Report Y-87-1, US
Army Engineer Waterways Experiment Station, Vicksburg, Miss.
Cooke, Sarah S. 1997. A Field Guide to the Common Wetland Plants of Western Washington and
Northwestern Oregon, Seattle Audubon Society and Washington Native Plant Society. Seattle, Washington.
Cowardin, L.M., V. Carter, F.C.Golet, and E.T. LaRoe. 1979. Classification of Wetlands and Deepwater
Habitats of the United States. US Fish and Wildlife Service, Washington DC. FWS/OBS-79/31.
King County. l 990. King County Sensitive Areas Map Folio. King County Environmental Division.
Bellevue, Washington.
King County. 2005. Critical Areas Ordinance No. 15051. Effective date January I, 2005.
Soil Survey of King County Area, Washington. 1973. United States Department of Agriculture, Soil
Conservation Service, in cooperation with the Washington Agricultural Experiment Station.
Munsell Color. 1992. Munsell Soil Color Charts. Kollmorgen Instruments Corp., Baltimore, MD.
Pojar, Jim and MacKinnon, Andy. 1994. Plants of the Pacific Northwest Coast, BC Forest Service Research
Program, Vancouver, British Columbia, Canada.
Reed, P.B., Jr. 1988. National List of Plant Species That Occur in Wetlands: Northwest (Region 9). U.S. Fish
and Wildlife Service Biological Report. 88(26.9). 89pp.
Washington State Department of Ecology. 1999. Washington State Wetlands Identification and Delineation
Manual. Pub!. No. 96-94.2
Washington State Department of Ecology. 2004. Washington State Wetlands Rating System for Western
Washington. Puhl. No. 04-06-025
Washington State Hydric Soils List, Washington Department of Ecology, Revised December 15, 1995.
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APPENDIX
EXHIBIT A:
VICINITY MAP, AERIAL PHOTO,
WETLAND SKETCH, SCS SOIL MAP
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warrant.es, express or ,mp:.ed , as to accuracy, oompleteoess. ume6ness, or nghts to the use of such mformalion this document IS not intended for use as f
sha ll not be liable for any general, speC:al, ind<fed, 10CK!ent.al , or consequential damages including, but not !•mited to, lost revenues or lost prof,ts resul ting
1nfom1ah0n conta,ned on this map. Any sale of th,s map or infomiation on thlS map 1s prohibited except by written permission of Kmg County.
Date: 5130/2007 Source: King County .MAP -Property lnfonnabon (httpJJwww.metrokc.gov/GIS/i MAP)
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IJESCRIPTIONS OF 1111' SOILS
This section des er j bes the soi 1 scri es and map-
ping units in the King County Arca. E~ch so~l .
series is described and then each mapping un1 t 1n
that series. Unless it is specifically mentioned
otherwise, it is to be assumed that what is stated
about the so] 1 series holds tn1c for the mapping
units in that series. Thus, to get full information
about any one mapping unit, it .is necessary to read
both the description of the mappjng unit and the
description of the soil series to which it belongs.
An important part of the description of each
soil series is the soil profile, that is, the
sequence of layers from the surface downward to
rock or other underlying material. Each series
contains two descriptions of this profile. The
first is brief and in tenns familiar to the layman.
The second, detailed and in technical terms, is for
scientists, engineers, and others who need to make
thorough and precise studies of soils. Unless it
is otherwise stated, the colors given in the
descriptions are those of a moist soil,
As mentioned in the section "How This Survey Was
Made,'' not all mapping units are members of a soil
series. Urban land, for ex~ple, does not belong
to a soil series, but nevertheless, is listed in
alphabetic order along with the soil series.
Following the name of each mapping unit is a
symbol in parentheses. This symbol identifies the
mapping unit on the detailed soil map. Listed at
the end of each description of a mapping unit is the
capability unit and woodland group in which the
mapping unit has been placed. The woodland desig-
nation and the page for the description of each
capability unit can be found by referring to the
11 Guide to Mapping Units" at the back of this survey.
The acreage and proportionate extent of each
mapping unit are shown in table 1. Many of the
terms used in describing soils can be found in the
Glossary at the end of this survey, and more de-
tailed information about the terminology and methods
of soil mapping can be obtained from the Soil Survey
Manual (.!2..) ,
Alderwood Series
lhe Alderwood series is made up of moderately
well drained soils that have a weakly consolfdated
to strongly consolidated substratum ·at a depth of
24 to 40 inches. These soils are on uplands. They
formed under conifers, in glacial deposits. Slopes
are Oto 70 percent. The annual precipitation is
35 to 60 inches, most of which is rainfall, between
October and May. The mean annual air temperature is
about 50° F. The frost-free season is 150 to 200
days. Elevation ranges from 100 to 800 feet.
In a representative profile, the surface layer
and subsoil are very dark brown, dark-brown, and
grayish-brown gravelly sandy loam about 27 inches
thick. Tiie substratum is grayish-brown, weakly
consolidated to strongly consolidated glacial till
that extends to a depth of 60 inches and more.
8
/\lderwood soils 8re used for timber, pasture,
berries, row crops, and urhan development. They
are the most extensive soi ls in the survey area.
Alderuood_gravelly sandy .!_0~111~~-t_o~~
~lopes (/\gC) .--'[ids soi 1 h ro11111g. l\reas .ire
irregular in shape and range from 10 to about 600
acres in size.
Representative profile of /\ldcrwood gravelly
sandy loam, 6 to 15 percent slopes, in woodland,
450 feet east and 1,300 feet south of the north
quarter corner of sec. 15. T. 24 N., R. 6 E.:
Al--0 to 2 inches, very dark brown (IOYR 2/2)
gravelly sandy loam, dark grayish brown
(lOYR 4/2) dry; weak, fine, granular struc-
ture; slightly hard, fr.i.ahlc, nonsticky,
nonplastic; many roots; strongly acid;
abrupt, wavy boundary. 1 to 3 inches thick.
B2--2 to 12 inches, dark-brown (IOYR 4/3) gravelly
sandy loam, brown (lOYR 5/3) dry; moderate,
medium, subangular blocky structure; slightly
hard, friable, nonsticky, nonplastic; many
roots; strongly acid; clear, wavy boundary.
9 to 14 inches thick.
B3--12 to 27 inches, grayish-brown (2.SY 5/2)
gravelly sandy loam, light gray (2.SY 7/2)
dry; many, mediwn, distinct mottles of light
olive brown (2.5Y 5/6); hard, friable, non-
sticky, nonplastic; many roots; mediwn acid;
abrupt, wavy boundary. 12 to 23 inches thick.
l!C--27 to 60 inches, grayish-brown (2.5Y 5/2),
weakly to strongly consolidated till, light
gray (2.SY 7/2) dry; common, medium, distinct
mottles of light olive brown and yellowish
brown (2.5Y 5/6 and !OYR 5/6); massive; no
roots; medilllll acid. Many feet thick.
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 logging 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 the poorly drained Norma
Bellingham, Seattle, Tukwila, and Shalcar soils· '
some are up to 5 percent the very gravelly Ever;tt
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 New-
castle Hills are 25 percent Beausite soils, some
no:theast of Duvall are as much as 25 percent Ovall
soils, and some in the vicinity of Dash Point are
10 percent Indianola and Kitsap soi ls, 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 subsoil and very slow in the substratum.
Roots penetrate easily to the consolidated substra-
tum 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. Rtmoff is slow to medium,
and the hazard of erosion is moderate.
This soil is used for timber, pasture1 berries,
and row crops, and for urban development. Capability
unit IVe-2; woodland group 3dl.
Alderwood ravelly sandy loam, 0 to 6 ercent
slopes (AgB) .--is soil is nearly level an
undulating. It is similar to Alderwood gravelly
sandy loam, 6 to 15 percent slopes, but in places
its surface layer is 2 to 3 inches thicker. Areas
are irregular in shape and range from 10 acres to
slightly more than 600 acres in size.
Some areas are as much as 15 percent included
Norma, Bellingham, Tukwila, and Shalcar soils, all
of which are poorly drained; and some areas in the
vicinity of Emunclaw are as much as 10 percent
Buckley soils.
RWloff is slow, and the erosion hazard is
slight.
This Alderwood soil is used for timber, pasture,
berries, and row crops, and for urban development.
Capability tmit IVe-2; woodland group 3d2.
Alderwood ravelly sandy loam, 15 to 30 ercent
slopes (AgD) .--Depth to t e su stratum in t is soil
varies within short distances, but is commonly
about 40 inches. Areas are elongated and range
from 7 to about 250 acres in size.
Soils included with this soil in mapping make
up no more than 30 percent of 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 of
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 mostly for timber.
Some areas on the lower parts of slopes are used
for pasture. Capability unit VIe-2; woodland -group
3dl.
Alderwood and Kitsap soils, very stee~ (Ak.F).--
Til.is mapping unit is about 50 percent Al erwood
gravelly sandy loam and 25 percent Kitsap silt
loam. Slopes are 25 to 70 percent. Distribution
of the soils varies greatly within short distances.
About 15 percent of some mapped areas is an
included, unnamed, very deep, moderately coarse
textured soil; and about 10 percent of some areas
is a very deep, coarse-textured Indianola soil.
Drainage and permeability vary. Runoff is rapid
to very rapid, and the erosion hazard is severe to
very severe. The slippage potential is severe.
These soils are used for timber. Capability
unit VIie-!; woodland group 2dl.
10
Arents, Alderwood Matedal
Arents, Alderwood material consists of Alderwood
::.oils that have been so disturbed through urban-
ization that they no longer can be classified with
the Alderwood series. These soils, however, have
many similar features. The upper part of the soil,
to a depth of 20 to 40 inches, is brown to dark-
brown gravelly sandy loam. Below this is a grayish-
brown, consolidated and :impervious substratum.
Slopes generally range from Oto 15 percent.
These soils are used for urban development.
Arents, Alderwood material, Oto 6 percent slopes
(AmB). --In many areas this soil is level, as a
result of shaping during construction for urban
facilities. Areas are rectangular in shape and
range from 5 acres to about 400 acres in size.
Representative profile of Arents, Alderwood
material, 0 to 6 percent slopes, in an urban area,
1,300 feet west and 350 feet south of the northeast
corner of sec. 23, T. 25 N., R. 5 E.:
0 to 26 inches, dark-brown (!OYR 4/3) gravelly
sandy loam, pale brown (IOYR 6/3) dry;
massive; slightly hard, very friable, non-
sticky, nonplastic; many roots; medium acid;
abrupt, smooth boundary. 23 to 29 inches
thick.
26 to 60 inches, grayish-brown (2.SY 5/2) weakly
consolidated to strongly consolidated glacial
till, light brownish gray (2.SY 6/2) dry;
common, meditDTI, prominent mottles of yellowish
brown (lOYR 5/6) moist; massive; no roots;
medium acid. Many feet thick.
The upper, very friable part of the soil extends
to a depth of 20 to 40 inches and ranges from dark
grayish brown to dark yellowish brown.
Some areas are up to 30 percent included soils
that are similar to this soil material, but either
shallower or deeper over the compact substratum;
and some areas are 5 to 10 percent very gravelly
Everett soils and sandy Indianola soils.
This Arents, Alderwood soil is moderately well
drained. Permeability in the upper, disturbed soil
material is moderately rapid to moderately slow,
depending on its compaction during construction,
The substratum is very slowly penneahle. Roots
penetrate to and tend to mat on the surface of the
consolidated substratum. Some roots enter the
substratwn through cracks. Water moves on ·top of
!he substratum in winter. Available water capacity
1s low. Runoff is slow, and the erosion hazard is
slight.
This soil is used for urban development. Ca-
pability unit IVe-2; woodland group 3d2.
Arents, Alderwood material, 6 to 1S percent
slopes (AmC). This soil has convex slopes. Areas
are"rectangular in shape and range from 10 acres to
about 450 acres in size.
Wetland Delineation Report
Hancock Short Plat
EXHIBITB:
RENTON CRITICAL AREAS MAPS
P:\2005\25332\Engineering\A nalysis-Calcs\Documents\ W ord\25332 Wetland Oc\ineation Report .doc
Concept Eng.
8/29/07
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS
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FLOOD HAZARDS
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5/30/2007
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 8 of 14
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Wetland Delineation Report
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EXHIBIT C:
WETLAND DATA FORMS
P:\2005\25332\Engineeri ng\Analysis-Calcs\Oocuments\ W ord\25 332 Wet land Deli neat ion Report.doc
Concept Eng.
8/29/07
DATA FORM
ROUTINE WETLAND DETERMINATION
(1987 COE Wetlands Delineation Manual)
Project/Site: Tax Parcel: 032305-9020 Date:
Applicant/Owner: Jonah-Kai Hancock County:
lnveslinator: Chris Holcomb State:
Do Normal Circumstances exist on the site? 0Yes 0No Community ID:
Is the site significantly disturbed (Atypical Situation)? 0Yes c;;:;JNo ~ransect ID:
5/25/07
King
WA
Is the area a potential Problem Area? 0Yes c;;:;JNo Plot ID: Samrle Point I
/If needed, exolain on reverse.\
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant Soecies Stratum Indicator
1. Kentucky Bluegrass Herb FAC 5.
1. Paa eratensis 5.
2. Common Velvetgi:ass Herb FAC 6.
2. Holcus linatus 6.
3. Slough Sedge Herb OBL 7.
3. Carex obnue_ta 7.
4 8.
4. 8.
Percent of Dominant Species that are OBL, FACW or FAC excluding FAC-). 3/3= 100%
Remarks: The parameter for wetland vegetation was met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Wetland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
Dother 0 Saturated in Upper 12 Inches
0 No Recorded Data Available D Water Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Depth of Surface Water: None (in.)
Secondary Indicators (2 or more required):
D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
12:J FAG-Neutral Test
Depth to Saturated Soil: 7 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was present.
SOILS
-]Map Unit Name Alderwood gravelly sandy loam (AgC) Sample Point 1 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? [8JYes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-12 A lOYR 3/1 Sandi' Gia)'
Hydric Soil Indicators:
D Histosol D Concretions
D Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
D Sulfidic Odor D Organic Streaking in Sandy Soils
D Aquic Moisture Regime D Listed on Local Hydric Soils List
D Reducing Conditions D Listed on National Hydric Soils List
[8J Gleyed or Low-Chroma Colors D Other (Explain in Remarks)
Remarks: Hydric soils were 12resent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present? [21Yes0No (Check) (Check)
Wetland Hydrology Present? [8JYes0No
Hydric Soils Present? [21Yes0No
Is this Sampling Point Within a
Wetland? [8JYes0No
Remarks: This is a representative location just within Wetland W.
Approved by HQUSACE 3192
DATA FORM
ROUTINE WETLAND DETERMINATION
( 1987 COE Wetlands Delineation Manual)
ProjecUSite: Tax Parcel: 032305-9020 Date:
ApplicanUOwner: Jonah-Kai Hancock County:
lnvestioator: Chris Holcomb State:
Do Normal Circumstances exist on the site? IZ]Yes 0No Community ID:
Is the site significantly disturbed (Atypical Situation)? 0Yes IZ]No -ransect ID:
5/25/07
King
WA
Is the area a potential Problem Area? 0Yes IZ]No Plot ID: SamEle Point 2
/If needed, exolain on reverse.)
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant Snecies Stratum Indicator
1. Evergreen Blackberry Shrub FACU 5.
1. Rubus lacinatus 5.
2. Red Clover Herb FACU 6.
2. Trifolium e_ratense 6.
3 Common V elvetgrass Herb FAC 7.
3. Ho/cus /inatus 7.
4. Soft Rush Herb FACW 8.
4. Juncus e[fesus 8.
Percent of Dominant Species that are OBL, FACWor FAC excludina FAC-). 2/4 = 50%
Remarks: The parameter for wetland vegetation was not met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Wetland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
D Other IZ] Saturated in Upper 12 Inches
IZl No Recorded Data Available D Water Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Secondary Indicators (2 or more required):
Depth of Surface Water: None (in.) D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
D FAC-Neutral Test
Depth to Saturated Soil: 10 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was present.
SOILS
f Map Unit Name Alderwood gravelly sandy loam (AgC) Sample Point 2 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? [2'.JYes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-12 A 10YR2/2 Sand)' Clal'
Hydric Soil Indicators:
D Histosol D Concretions
D Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
D Sulfidic Odor D Organic Streaking in Sandy Soils
D Aquic Moisture Regime D Listed on Local Hydric Soils List
D Reducing Conditions D Listed on National Hydric Soils List
D Gleyed or Low-Chroma Colors D Other:
Remarks: Hydric soils were not ~resent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present?
Wetland Hydrology Present?
Hydric Soils Present?
0Yes[2JNo
[2JYes0No
0Yes[2JNo
(Check)
,,this Sampling Point Within a
I etland?
Remarks: This is a representative location just outside of Wetland W.
(Check)
0Yes[2JNo
Approved by HQUSACE J/92
DATA FORM
ROUTINE WETLAND DETERMINATION
( 1987 COE Wetlands Delineation Manual)
ProjecUSite: Tax Parcel: 032305-9020 Date:
ApplicanUOwner: Jonah-Kai Hancock County:
lnvestiaator: Chris Holcomb State:
Do Normal Circumstances exist on the site? J::,<;lYes 0No Community ID:
ls the site significantly disturbed (Atypical Situation)? 0Yes J::,<;]No -ransect ID:
5/25/07
Kine.
WA
Is the area a potential Problem Area? 0Yes [g!No Plot ID: Samele Point 3
/If needed, exolain on reverse. l
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant Soecies Stratum Indicator
1. Soft Rush Herb FACW 5.
1. Juncus ef/usus 5.
2. Red Clover Herb FACU 6.
2. Trifolium e.ratense 6.
3. Common Velvetgrass Herb FAC 7.
3. Holcus linatus 7.
4. 8.
4. 8.
Percent of Dominant Species that are OBL, FACW or FAC excluding FAC-). 2/3-66.6%
Remarks: The parameter for wetland vegetation was met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Wetland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
D Other (gJ Saturated in Upper 12 Inches
[gJ No Recorded Data Available D Water Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Secondary Indicators (2 or more required):
Depth of Surface Water: None (in.) D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
D FAG-Neutral Test
Depth to Saturated Soil: 8 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was present.
SOILS
1Map Unit Name Aldcrwood gravelly sandy loam (AgC) Sample Point 3 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? ~Yes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-6 A lOYR 3/3 Sandy Clay
6-12 B 10YR4/2 IOYR 3/6 I 5%/Med./Prom. Sandy Clay
Hydric Soil Indicators:
0 Histosol D Concretions
0 Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
0 Sulfidic Odor D Organic Streaking in Sandy Soils
0 Aquic Moisture Regime D Listed on Local Hydric Soils List
0 Reducing Conditions D Listed on National Hydric Soils List
0 Gleyed or Low-Chroma Colors ~ Other: Mottles in a chroma 2 matrix
Remarks: Hydric soils were gresent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present? IS]YesDNo (Check) (Check)
Wetland Hydrology Present? ~YesONo
Hydric Soils Present? ~YesONo
Is this Sampling Point Within a
Wetland? ~YesONo
Remarks: This is a representative location within the west end of Wetland W.
Approved by HQUSACE J/92
DATA FORM
ROUTINE WETLAND DETERMINATION
(1987 COE Wetlands Delineation Manual)
ProjecUSite: Tax Parcel 032305-9020 Date:
ApplicanUOwner: Jonah-Kai Hancock :ounty:
lnvestinator: Chris Holcomb C:tate:
Do Normal Circumstances exist on the site? 12:JYes 0No Community ID:
Is the site significantly disturbed (Atypical Situation)? 0Yes 12:JNo -ransect ID:
5/25/07
King
WA
Is the area a potential Problem Area? DYes 12:JNo Plot ID: Samele Point 4
/If needed, exolain on reverse.)
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant Srw:,.cies Stratum Indicator
1. Common Velvetg,:ass Herb FAC 5.
1. Ho/cus linatus 5.
2. Red Clover Herb FACU 6.
2. Trifolium eratense 6.
3. Soft Rush Herb FACW 7.
3. Juncus effusus 7.
4. Tall Buttercue Herb FACW-8.
4. Ranunculus acris 8.
Percent of Dominant Species that are OBL, FACW or FAG excluding FAC-). 3/4 = 75%
Remarks: The parameter for wetland vegetation was met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Wetland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
OOther D Saturated in Upper 12 Inches
12J No Recorded Data Available D Water Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Depth of Surface Water: None (in.)
Secondary Indicators (2 or more required):
D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
12J FAC-Neutra I Test
Depth to Saturated Soil: >12 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was not present.
SOILS
I Map Unit Name Alderwood gravelly sandy loam (AgC) Sample Point 4 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? [2JYes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-12 A 7.5YR 3/2 Sandy Clay
Hydric Soil Indicators:
0 Histosol D Concretions
0 Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
0 Sulfidic Odor D Organic Streaking in Sandy Soils
0 Aquic Moisture Regime D Listed on Local Hydric Soils List
0 Reducing Conditions D Listed on National Hydric Soils List
0 Gleyed or Low-Chroma Colors D Other:
Remarks: Hydric soils were not ~resent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present? [2JYes0No (Check) (Check)
Wetland Hydrology Present? 0Yes[2JNo
Is this Sampling Point Within a
Hydric Soils Present? 0Yes[2JNo Netland? OYes [2JNo
Remarks: This is a representative location just outside of Wetland W.
Approved by HQUSACE 3/92
DATA FORM
ROUTINE WETLAND DETERMINATION
(1987 COE Wetlands Delineation Manual)
Project/Site: Tax Parcel 032305-9020 Date:
Applicant/Owner: Jonah-Kai Hancock County:
lnvestiaator: Chris Holcomb !':late:
Do Normal Circumstances exist on the site? IZ]Yes 0No vommunity ID:
Is the site significantly disturbed (Atypical Situation)? 0Yes IZ]No -ransect ID:
5125/07
King
WA
Is the area a potential Problem Area? 0Yes IZ]No Plot ID: Samele Point 5
/If needed, exolain on reverse.)
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant SrY>cies Stratum Indicator
1. Tall Buttercu12 Herb FACW-5. Curled Dock Herb FAC
1. Ranunculus acris 5. Rumex Crise.us
2. Common Velvetgrass Herb FAC 6.
2. Holcus linatus 6.
3. Red Clover Herb FACU 7.
3. Trifolium eratense 7.
4. Orchard Morning Glol}' Herb NI 8.
4. Convolvulus arvensis 8.
Percent of Dominant Species that are OBL, FACW or FAC excluding FAG-). 3/4-75%
Remarks: The parameter for wetland vegetation was met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Netland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
D Other IZ] Saturated in Upper 12 Inches
IZl No Recorded Data Available D Waler Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Depth of Surface Water: None (in.)
Secondary Indicators (2 or more required):
D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
D FAG-Neutral Test
Depth to Saturated Soil: 9 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was present.
SOILS
[Map Unit Name Alderwood gravelly sandy loam (AgC) Sample Point 5 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? [g!Yes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-12 A IOYR 212 Sandy Clay
Hydric Soil Indicators:
D Histosol D Concretions
D Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
D Sulfidic Odor D Organic Streaking in Sandy Soils
D Aquic Moisture Regime D Listed on Local Hydric Soils List
D Reducing Conditions D Listed on National Hydric Soils List
D Gleyed or Low-Chroma Colors D Other (Explain in Remarks)
Remarks: Hydric soils were not 11resent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present? [giYesONo (Check) (Check)
Wetland Hydrology Present? [g!YesONo
Is this Sampling Point Within a
Hydric Soils Present? OYes[giNo Wetland? 0Yes[g!No
Remarks: This is a non-wetland area located between Wetlands Wand Y and adjacent to the stream. This land was
slightly higher than surrounding areas within either wetland.
DATA FORM
ROUTINE WETLAND DETERMINATION
( 1987 COE Wetlands Delineation Manual)
ProjecVSite: Tax Parcel: 032305-9020 Date:
ApplicanVOwner: Jonah-Kai Hancock County:
lnvestiaator: Chris Holcomb State:
Do Normal Circumstances exist on the site? IS]Yes 0No .;ommunity ID:
Is the site significantly disturbed (Atypical Situation)? 0Yes IS]No Transect ID:
5/25/07
King
WA
Is the area a potential Problem Area? 0Yes IS]No Plot ID: Samele Point 6
(If needed, exolain on reverse.)
VEGETATION
Dominant Plant Species Stratum Indicator Dominant Plant Soecies Stratum Indicator
1. Tall ButtercuI' Herb FACW-5. Curled Dock Herb FAC
1. Ranunculus acris 5. Rumex cris[!_US
2. Common Velvetgrass Herb FAC 6.
2. Holcus linatus 6.
3. Tall Fescue Herb FAC-7.
3 F estuca arundinacea 7.
4. Morning Glo,:y Herb NI 8.
4. Convolvulus arvensis 8.
Percent of Dominant Species that are OBL, FACW or FAG excluding FAC-). 3/4-75%
Remarks: The parameter for wetland vegetation was met.
HYDROLOGY
D Recorded Data (Describe in Remarks): Welland Hydrology Indicators:
D Stream, Lake, or Tide Gauge Primary Indicators:
D Aerial Photographs D Inundated
OOther IS] Saturated in Upper 12 Inches
IS] No Recorded Data Available D Water Marks
D Drift Lines
D Sediment Deposits
Field Observations: D Drainage Patterns in Wetlands
Secondary Indicators (2 or more required):
Depth of Surface Water: None (in.) D Oxidized Root Channels in Upper 12 Inches
D Water-Stained Leaves
Depth to Free Water in Pit: >12 (in.) D Local Soil Survey Data
D FAG-Neutral Test
Depth to Saturated Soil: 5 (in.) D Other (Explain in Remarks)
Remarks: Wetland hydrology was present.
SOILS
[Map Unit Name Alderwood gravelly sandy loam (AgC) Sample Point 6 (pg.2)
(Series and Phase): Drainage Class: Moderate
Field Observations
Taxonomy (Subgroup): Confirm Mapped Type? [g!Yes 0No
Profile Descriptions: Mottle
Depth Matrix Color Mottle Colors Abundance/ Texture, Concretions,
(inches) Horizon (Munsell Moist) (Munsell Moist) Size/Contrast Structure, etc,
0-12 A !OYR 2/2 IOYR 3/6 Sandr Clar
Hydric Soil Indicators:
D Histosol D Concretions
D Histic Epipedon D High Organic Content in Surface Layer in Sandy Soils
D Sulfidic Odor D Organic Streaking in Sandy Soils
D Aquic Moisture Regime D Listed on Local Hydric Soils List
D Reducing Conditions D Listed on National Hydric Soils List
D Gleyed or Low-Chroma Colors [gJ Other: Mottles in a chroma 2 matrix
Remarks: Hydric soils were Qresent at this location.
WETLAND DETERMINATION
Hydrophytic Vegetation
Present? [8JYes0No (Check) (Check)
Welland Hydrology Present? [8JYes0No
Is this Sampling Point Within a
Hydric Soils Present? [8JYes0No Welland? [8JYes0No
Remarks: This is a representative location just inside of Wetland Y.
Approved by HQUSACE 3/92
Wetland Delineation Report
Hancock Short Plal
EXHIBIT D:
RENTON MUNICIPAL CODE EXCERPTS
Concept Eng.
8129107
•
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 54 of 158
assessment shall determine the extent, function and value of the critical habitat and potential for impacts and
mitigation consistent with report requirements in RMC 4-8-1200. In cases where a proposal is not likely to
significantly impact the critical habitat and there is sufficient information to determine the effects of a
proposal, an applicant may request that this report be waived by the Department Administrator in accordance
with subsection D4b of this Section.
3. Bald Eagle Habitat: Bald eagle habitat shall be protected pursuant to the Washington Slate Bald Eagle
Protection Rules (:NAC 232-12-292).
4. Native Growth Protection Areas: Based on the required habitat assessment, the Reviewing Official may
require critical habitat areas and their associated buffers be placed in a native growth protection area subject
to the requirements of subsection E4 of this Section, or dedicated lo a conservation organization or land trust,
or similarly preserved through a permanent protective mechanism acceptable to the City.
5. Alterations Require Mitigation: If alterations to critical habitaVwildlife habitat or buffers are proposed,
mitigation shall be required by the City. The applicant shall evaluate alternative methods of developing the
property using the following criteria in this order:
a. Avoid any disturbances to the habitat.
b. Minimize any impacts to the habitat.
c. Compensate for any habitat impacts.
6. Mitigation Options: In addition to any performance standards or mitigation required by wetland
regulations, additional mitigation may be determined by the Reviewing Official based upon the consultant
report submitted by the applicant, and/or peer review of the applicant's consultant report by a qualified
professional selected by the City at the applicant's expense, and/or by information from State or Federal
agencies.
a. On.Site Mitigation: Mitigation shall be provided on-site, unless on-site mitigation is not scientifically
feasible due to physical features of the property. The burden of proof shall be on the applicant to
demonstrate that mttigation cannot be provided on-site.
b. Off.Site Mitigation: When mitigation cannot be provided on-site, mitigation shall be provided in the
immediate vicinity of the permitted activity on property owned or controlled by the applicant, and
identified as such through a recorded document such as an easement or covenant, provided such
mitigation is beneficial to the habitat area and associated resources.
c. In-Kind Mitigation: In-kind mitigation shall be provided except when the applicant demonstrates and
the City concurs that greater functional and habitat value can be achieved through out-of-kind mitigation.
7. Mitigation Plan: Mitigation plans may be required consistent with subsection F8 of this Section. (Ord.
5137, 4-25-2005)
L. STREAMS AND LAKES:
1. Applicability/Lands to Which These Regulations Apply: These stream and lake regulations apply to
sites containing all or portions of Class 2 to 4 streams or lakes and/or their buffers as described below. This
section does not apply to Class 1 waters which are regulated by RMC 4-3-090, Shoreline Master Program
Re ulations, or to Class 5 waters which are exempt. All other critical area regulations, including, but not
hm1 e , ' regu ations an we an regu a ions, do apply to classified streams where applicable .
a. Classification System: The following classification system is hereby adopted for the purposes of
regulating streams and lakes in the City. Stream and lake buffer widths are based on the following rating
system:
i. Class 1: Class 1 waters are perennial salmonid-bearing waters which are classified by the City
and State as Shorelines of the State.
ii. Class 2: Class 2 waters are perennial or intermittent salmonid-bearing waters which meet one or
more of the following criteria:
(a) Mapped on Figure 04, Renton Water Class Map, as Class 2; and/or
(b) Historically and/or currently known to support salmonids. including resident trout, at any stage in the species lifecycle;
and/or
(c) Is a water body (e.g., pond, lake) between one half (0.5) acre and twenty (20) acres in size.
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 55 of 158
iii. Class 3: Class 3 waters are non-salmonid-bearing perennial waters during years of normal
rainfall, and/or mapped on Figure Q4, Renton Water Class Map, as Class 3.
iv. Class 4: Class 4 waters are non-salmonid-bearing intermittent waters during years of normal
rainfall, and/or mapped on Figure Q4, Renton Water Class Map, as Class 4.
:...:-.:::;;;.>3-~"'..;/;;.,· -------''))~ v. Class 5: Class 5 waters are non-regulated non-salmonid-bearing waters which meet one or more
r, · of the following criteria:
(a) Flow within an artificially constructed channel where no naturally defined channel had previously existed; and/or
(b) Are a surficially isolated water body less than one-ha~ (0.5) acre (e.g., pond) not meeting the criteria for a wetland as
defined in subsection M of this Section.
b. Measurement:
i. Stream/Lake Boundary: The boundary of a stream or lake shall be considered to be its ordinary
high water mark (OHWM). The OHWM shall be flagged in the field by a qualified consultant when
any study is required pursuant to subsection L of this Section.
ii. Buffer: The boundary of a buffer shall extend beyond the boundaries of the stream or lake to the
width applicable to the stream/lake class as noted in Subsection L5 of this Section, Stream/Lake
Buffer Width Requirements. Where streams enter or exit pipes, the buffer in this subsection L 1 b(ii)
shall be measured perpendicular to the ordinary high water mark from the end of the pipe along the
open channel section of the stream.
' '
,I
Figure 4-3-050L 1 b(ii). Buffer measurement at pipe opening.
c. Maps and Inventory:
i. Mapped Streams and Lakes: The approximate location and extent of Class 2 to 4 water bodies
within the City limits are indicated on a map in subsection Q of this Section, Maps. The map is to be
used as a guide to the general location and extent of streams. Specific locations and extents will be
determined by the City based upon field review and applicant-funded studies prepared pursuant to
subsection L3 of this Section.
ii. Reclassification: Where there is a conflict between the Renton Water Class Map in Subsection
Q and the criteria in subsection L 1 a of this Section, the criteria in subsection L 1 a of this Section
shall govern. The reclassification of a water body to a lower class (i.e. 2 to 3, or 3 to 4, etc.) requires
administrator acceptance of a supplemental stream or lake study, followed by a legislative
amendment to the map in subsection Q of this Section prior to its effect.
iii. Unmapped Streams and Lakes: Streams and lakes which are defined in subsection L 1 a of this
Section, Classification System, but not shown on the Renton Water Class Map in subsection Q of
this Section, are presumed to exist in the City and are regulated by all the provisions of this Section.
If the water body is unmapped according to the City of Renton's Water Class Map (refer to
subsection Q of this Section), and:
(a) The width of the stream channel averages less than two feet (2') at the ordinary high water mark; or
(b) The stream channel has an average gradient of greater than twenty percent (20%); or
(c) The channel or water body is upstream of an existing, enduring, and complete barrier to salmonid migration, as interpreted
in subsection L 1 c(iv} of this Section, or as shown on the City of Renton's Salmonid Migration Barrier Map, and the channel or
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 56 of 158
water body contains water only intermittently upstream of the barrier during years of normal rainfall; or
(d) The water body is isolated from any connected stream and/or wetland; or
(e) The water body is less than one-half (0.5) acre in size and connected to a stream meeting the criteria noted in subsections
L 1c(iii)(a) through (c) of this Section;
Then the water body is considered non-salmonid-bearing and water class would be assessed based upon the non-salmonid-
bearing waters criteria in subsections L 1a(iii) through (v) of this section. However, If none of the conditions above apply, then
the water body is considered Salmonid-Bearing -Class 2. Classification of an unmapped stream or lake is effective upon
expiration of the fourteen (14) day appeal period following the Administrator's determination, and the map in subsection Q of
this Section shall be amended consistent with Administrator determinations at the next appropriate amendment cycle.
iv. Salmonid Migration Barriers: For purposes of classifying or reclassifying water bodies, features
determined by the Administrator to be salmonid migration barriers per definition in RMC 4-11-190
shall be mapped. The Administrator shall prepare and update the map as appropriate and maintain
a copy in the Planning/Building/Public Works Customer Service Area.
v. Experts or State Agency May Be Required or Consulted: The City may require an applicant to
retain an expert or to consult the Washington Department of Fish and Wildlife to assess salmonid-
bearing status of the channel in question and prepare a report to the City detailing the facts and
conclusion of their analysis.
vi. Criteria to Govern: The actual presence or absence of the stream and lake criteria listed in this
subsection L, as determined by qualified professionals, shall govern the treatment of an individual
building site or parcel of land requiring compliance with these regulations.
2. Applicability -Activities to Which This Section Applies: This Section applies to all non-exempt
activities on sites containing Class 2 to 4 streams or lakes and their associated buffers.
3. Studies Required:
a. When Standard Stream or Lake Study Is Required: The applicant shall be required to conduct a
standard stream or lake study per RMC 4-8-120 if a site contains a water body or buffer area or the
project area is within one hundred feet (100') of a water body even if the water body is not located on the
subject property.
b. When Supplemental Stream or Lake Study is Required: The applicant shall be required to conduct
a supplemental stream or lake study per RMC 4-8-120 if a site contains a water body or buffer area and
changes to buffer requirements or alterations of the water body or its associated buffer are proposed,
either administratively or via a variance request.
c. When Stream or Lake Mitigation Plan is Required: The applicant shall be required to conduct a
stream or lake mitigation plan per RMC 4-8-120 if impacts are identified within a supplemental stream or
lake study. The approval of the stream or lake mitigation plan by the Administrator shall be based on the
criteria located in subsection L3c(ii) of this Section.
i. Timing of Mitigation Plan -Final Submittal and Commencement: When a stream or lake
mitigation plan is required, the applicant shall submit a final mitigation plan for the approval of the
Administrator prior to the issuance of building or construction permits, whichever comes first. The
applicant shall receive written approval of the final mitigation plan prior to commencement of any
mitigation activity.
ii. Criteria for Approval of Stream or Lake Mitigation Plan for Alterations of Streams and
Lakes or Associated Buffers: In order to approve a stream or lake mitigation plan the
Administrator shall find that the plan demonstrates compliance with the following criteria:
(a) Mitigation Location: Mitigation location shall follow the preferences in subsections L3c(ii)(a)(1) to (4) of this Section.
Basins and subbasins are indicated in subsection Q of this Section, Maps:
(1) On-Site Mitigation: On-site mitigation is required unless the Reviewing Official finds that on-site mitigation is notfeasible
or desirable;
(2) Off-Site Mitigation within Same Drainage Subbasin as Subject Site: Off-site mitigation may be allowed when located
within the same drainage subbasin as the subject site and ~ It achieves equal or improved ecological functions over mitigation
on the subject site;
(3) Off-Site Mitigation within Same Drainage Basin within City Limits: Off-site mitigation may be allowed when located
within the same drainage basin within the Renton City limits if it achieves equal or improved ecological functions within the City
over mitigation within the same drainage subbasin as the project;
(4) Off-Site Mitigation within the Same Drainage Basin Outside the City Limits: Off-site mitigation may be allowed when
located within the same drainage basin outside the Renton City limits if it achieves equal or improved ecological functions over
mitigation within the same drainage basin within the Renton City limits and it meets City goals.
(b) Mitigation Type: Types of mitigation shall follow the preferences in subsections L3c(ii)(b)(1) to (4) of this Section:
(1) Daylighting (returning to open channel) of streams or removal of manmade salmonid migration barriers;
(2) Removal of impervious surfaces in buffer areas and improved biological function of the buffer;
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 57 of I 58
(3) In-stream or in-lake mitigation as part of an approved watershed basin restoration project;
(4) Other mitigation suitable for site and water body conditions that meet all other provisions for a mitigation plan.
In all cases, mitigation shall provide for equivalent or greater biological functions per subsection L3c(ii)(e) of this Section.
(c) Contiguous Corridors: Mitigation sites shall be located to preserve or achieve contiguous riparian or wildlife conridors to
minimize the isolating effects of development on habitat areas, so long as mitigation of aquatic habitat is located within the
same aquatic ecosystem as the area disturbed; and
(d) Non-Indigenous Species: Wildlife or fish species not indigenous to the region shall not be introduced into a riparian
mitigation area unless authorized by a State or Federal permit or approval. Plantings shall be consistent with subsection L6c of
this Section; and
(e) Equivalent or Greater Biological Functions: The Administrator shall utilize the report "City of Renton Best Available
Science Literature Review and Stream Buffer Recommendations" by AC Kindig & Company and Cedarock Consultants, dated
February 27, 2003, unless superseded with a City-adopted study, to determine the existing or potential ecological function of
the stream or lake or riparian habitat that is being affected. Mitigation shall address each function affected by the alteration.
Mitigation to compensate alterations to stream/lake areas and associated buffers shall achieve equivalent or greater biologic
and hydrologic functions and shall include mitigation for adverse impacts upstream or downstream of the development
proposal stte. No net loss of riparian habitat or water body function shall be demonstrated; and
(I) Minimum Mitigation Plan Performance Standards: See Subsection F8 of this Section.
(g) Additional Conditions of Approval: The Administrator shall condition approvals of activities allowed within or abutting a
streamnake or its buffers, as necessary to minimize or mitigate any potential adverse impacts. Conditions may include, but are
not limited to, the following:
(1) Preservation of critically important vegetation and/or habitat features such as snags and downed wood;
(2) Limitation of access to the habitat area, including fencing to deter unauthorized access;
(3) Seasonal restriction of construction activities; and
(4) Establishment of a duration and timetable for periodic review of mitigation activities.
(hi Based on Best Available Science: The applicant shall demonstrate that the mitigation is based on consideration of the
best available science as described in WAC 365-195-905; or where there is an absence of valid scientific information, the
steps in RMC 4-9-250F are followed.
iii. Performance Surety: The Administrator shall require a performance surety to ensure completion
and success of proposed mitigation, per subsection G of this Section and RMC 4-1-230.
iv. Alternative Mitigation: The mitigation requirements set forth in this subsection L3 may be
modified at the Administrator's discretion if the applicant demonstrates that improved habitat
functions, on a per function basis, can be obtained in the affected sub-drainage basin as a result of
alternative mitigation measures.
d. Studies Waived:
i. Standard Stream or Lake Study: May only be waived by the Administrator when the applicant
provides satisfactory evidence that:
(a) A road, building or other barrier exists between the water body and the proposed activity, or
(b) The water body or required buffer area does not intrude on the applicant's lot, and based on evidence submitted, the
proposal will not result in significant adverse impacts to nearby water bodies regulated under this Section: or
(c) Applicable data and analysis appropriate to the proposed project exists and an additional study Is not necessary.
ii. Supplemental Stream or Lake Study: May only be waived by the Administrator when:
(a) No alterations or changes to the stream or lake, or tts standard buffer are proposed; or
(b) Applicable data and analysis appropriate to the proposed project exists and an additional report is not necessary.
iii. Stream or Lake Mitigation Plan: May only be waived when no impacts have been identified
through a supplemental stream or lake study.
e. Period of Validity for Studies Associated with This Section: Studies submitted and reviewed are
valid for five (5) years from date of study completion unless the Administrator determines that conditions
have changed significantly.
4. General Standards for Class 2 to 4 Waters:
a. Disturbance Prohibited: Streams and lakes and their buffer areas shall be undisturbed, except
where the buffer is to be enhanced, or where exemptions allowed in subsection C of this Section are
conducted, or where allowed to be altered in accordance with subsections L5, L7 and LS of this Section.
Where water body or buffer disturbance has occurred in accordance with exemption or development
permit approval during construction or other activities, revegetation with native vegetation shall be
required.
b. No Net Loss: There shall be no net loss of riparian area or shoreline ecological function resulting from
any activity or land use occurring within the regulated buffer area.
5. Stream/Lake Buffer Width Requirements:
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 62 of 158
b. Standard buffers may be reduced per subsection L5c of this Section. If reduced buffers in subsection
L5c of this Section along with other development standards of the zone would not allow the same
development level as without the watercourse daylighting, a modification may be requested as in
subsection N of this Section.
c. When designed consistent with the City's flood regulations in subsection 16 of this Section, portions of
the daylighted stream/created buffer may be considered part of compensatory storage in flood hazard
areas.
d. Stream relocation is permitted subject to subsection LB of this Section. (Ord. 5137, 4-25-2005)
M. WETLANDS:
1. Applicability: The wetland regulations apply to sites containing or abutting wetlands as described below.
Category 3 wetlands, less than two thousand two hundred (2,200) square feet in area, are exempt from these
regulations if they meet exemption criteria in subsection C of this Section.
a. Classification System: The following classification system is hereby adopted for the purposes of
regulating wetlands in the City. Wetlands buffer widths, replacement ratios and avoidance criteria shall
be based on the following rating system:
i. Category 1: Category 1 wetlands are wetlands which meet one or more of the following criteria:
(a) The presence of species listed by Federal or State government as endangered or threatened, or the presence of essential
habitat for those species; and/or
(b) Wetlands having forty percent (40%) to sixty percent (60%) permanent open water (in dispersed patches or otherwise) w~h
two (2) or more vegetation classes; and/or
(c) Wetlands equal to or greater than ten (10) acres in size and having three (3) or more vegetation classes, one of which is
open water; and/or
(d) The presence of plant associations of infrequent occurrence; or at the geographic limits of their occurrence; and/or
ii. Category 2: Category 2 wetlands are wetlands which meet one or more of the following criteria:
(a) Wetlands that are not Category 1 or 3 wetlands; and/or
(b) Wetlands that have heron rookeries or osprey nests, but are not Category 1 wetlands; and/or
(c) Wetlands of any size located at the headwaters of a watercourse, i.e., a wetland w~ a perennial or seasonal outflow
channel, but with no defined influent channel, but are not Category 1 wetlands; and/or
(d) Wetlands having minimum existing evidence of human-related physical alteration such as diking, ditching or channelization;
and/or
iii. Category 3: Category 3 wetlands are wetlands which meet one or more of the following criteria:
(a) Wetlands that are severely disturbed. Severely disturbed wetlands are wetlands which meet the following criteria:
(1) Are characterized by hydrologic Isolation, human-related hydrologic alterations such as diking, ditching, channelization
and/or outlet modification; and
(2) Have soils alterations such as the presence of fill, soil removal and/or compaction of soils; and
(3) May have altered vegetation.
(b) Wetlands that are newly emerging. Newly emerging wetlands are:
(1) Wetlands occurring on top of fill materials; and
(2) Characterized by emergent vegetation, low plant species richness and used minimally by wildlife. These wetlands are
generally found in the areas such as the Green River Valley and Black River Drainage Basin.
(c) All other weUands not classified as Category 1 or 2 such as smaller, high qualily wetlands.
b. Maps and Inventory:
i. The approximate location and extent of wetlands in the City is displayed in subsection Q of this
Section, Maps. The map is to be used as a guide to the general location and extent of wetlands.
ii. Wetlands which are defined in subsection M1a of this Section, Classification System, but not
shown on the Renton Wetlands Map Inventory, are presumed to exist in the City and are also
protected under all the provisions of this Section.
iii. The actual presence or absence of the wetland criteria listed above, as determined by qualified
professionals, shall govern the treatment of an individual building site or parcel of land requiring
compliance with these regulations.
c. Delineation of Wetland Edge: For the purpose of regulation, the wetland edge should be delineated
pursuant to subsection M4 of this Section.
d. Regulated and Nonregulated Wetlands: Refer to subsection M1a and M1e of this Section for
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS
applicability thresholds for regulatory and nonregulatory wetlands.
Page 63 of 158
e. Performance Standards: In addition to general standards of subsection E of this Section, the
following performance standards apply to all regulated wetlands.
i. Regulated and Nonregulated Wetlands -General: Wetlands created or restored as a part of a
mitigation project are regulated wetlands. Regulated wetlands do not include those artificial wetlands
intentionally created from nonwetland sites for purposes other than wetland mitigation, including, but
not limited to. irrigation and drainage ditches, grass-lined swales, canals, detention facilities,
wastewater treatment facilities. farm pond, and landscape amenities. or those wetlands created after
July 1, 1990, that were unintentionally created as a result of the construction of a road, street. or
highway. The Department Administrator shall determine that a wetland is not regulated on the basis
of photographs, statements. and other evidence. · ,
ii. Nonregulated Category 3 Wetlands: Based upon an applicant request. the Uepartmenr •
Administrator may determine that Category 3 wetlands are not considered regulated wetlands. if the
applicant demonstrates the following criteria are met:
(a) The wetiand formed on top of fill legally placed on a property; and
(b) The wetland hydrology is solely provided by the compaction of the soil and fill material; and
(c) The U.S. Army Corps of Engineers has determined that they will not take jurisdiction over the wetiand.
2. General Standards for Permit Approval: Permit approval by the Reviewing Official for projects involving
regulated wetlands or wetland buffers shall be granted only if the approval is consistent with the provisions of
this Section. Additionally, approvals shall only be granted if:
a. A proposed action avoids adverse impacts to regulated wetlands or their buffers or takes affirmative
and appropriate measures to minimize and compensate for unavoidable impacts; and
b. The proposed activity results in no net loss of regulated wetland area, value, or function in the
drainage basin where the wetland is located; or
c. A variance process is successfully completed to determine conditions for permitting of activity
requested including measures to reduce impacts as appropriate.
3. Study Required:
a. When Study ts Required: Wetland assessments are required as follows:
i. Wetland Classification: The applicant shall be required to conduct a study to determine the
classification of the wetland if the subject property or project area is within one hundred feet (100') of
a wetland even if the wetland is not located on the subject property but it is determined that
alterations of the subject property are likely to impact the wetland in question or its buffer. If there is
a potential Category 1 or 2 wetland within three hundred feet (300') of a proposal, the City may
require an applicant to conduct a study even if the wetland is not located on the subject property but
it is determined that alterations of the subject property are likely to impact the wetland in question or
its buffer.
ii. Wetland Delineation: A wetland delineation is required for any portion of a wetland on the
subject property that will be impacted by the permitted activities.
b. Study Waived: The wetland assessment shall be waived by the Department Administrator when the
applicant provides satisfactory evidence that a road, building or other barrier exists between the wetland
and the proposed activity, or when the buffer area needed or required will not intrude on the applicant's
lot. or when applicable data and analysis appropriate to the project proposed exists and an additional
report is not necessary.
4. Delineation of Regulatory Edge of Wetlands:
a. Methodology: For the purpose of regulation, the exact location of the wetland edge shall be
determined by the wetlands specialist hired at the expense of the applicant through the performance of a
field investigation using the procedures provided in the following manual: Washington State Wetlands
Identification and Delineation Manual, Washington State Department of Ecology, March 1997, Ecology
Publication No. 96-94.
b. Delineations -Open Water: Where wetlands are contiguous with areas of open freshwater, streams,
or rivers, the delineation shall be consistent with the Washington State Wetlands Rating System:
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 64 of 158
Western Washington, Second Edition, Washington State Department of Ecology, August 1993,
Publication No. 93-74, Appendix 5, or another accepted Federal or State methodology, subject to City
review.
c. Adjustments to Delineation by City: Where the applicant has provided a delineation of the wetland
edge, the City shall review and may render adjustments to the edge delineation. In the event the
adjusted edge delineation is contested by the applicant, the City shall, at the applicant's expense, obtain
the services of an additional qualified wetlands specialist to review the original study and render a final
delineation.
d. Period of Validity for Wetland Delineation:
i. Within City Limits: A final wetland delineation, for properties within the city limits at the time the
delineation was prepared, is valid for five (5) years, unless the Administrator determines that
conditions have changed.
ii. Outside City Limits: The period of validity of wetland delineations for properties, which were
unincorporated at the time of the delineation, will be determined by the Administrator. Following a
review of a wetland delineation prepared for an unincorporated property, since annexed into the
City, the Administrator may require adjustments be made to the study or a new study prepared, per
subsection M4 of this Section, Delineation of Regulatory Edge of Wetlands.
5. Determination of Wetland Classification: Wetland studies shall determine the appropriate wetland
classification according to subsection M1 of this Section, Wetlands. The City may accept a dual wetland
classification for a wetland exhibiting a combination of Category 1 and 2 features or a combination of
Category 1 and 3 features. The City will not accept a dual rating for a Category 2 wetland, such as a
combined Category 2 and 3 rating. Dual ratings for a Category 1 wetland shall be consistent with the
Washington State Wetlands Rating System: Western Washington, Second Edition, Washington State
Department of Ecology, August 1993, Publication No. 93-74 or as thereafter amended or updated.
6. Wetland Buffers:
a. Buffers Required:
i. Wetland buffer zones shall be required of all proposed regulated activities abutting regulated
wetlands.
ii. Any wetland created, restored, or enhanced in conjunction with creation or restoration as
compensation for approved wetland alterations shall include the standard buffer required for the
class of the wetland being replaced.
iii. All required wetland buffer zones shall be retained in their natural condition. Category 3 wetland
buffers of twenty five feet (25') require the buffers be fully vegetated with native species or restored;
otherwise increased buffer widths to protect functions and values may be required.
iv. Where buffer disturbance has occurred during construction or other activities, revegetation with
native vegetation may be required.
b. Measurement of Buffers: All buffers shall be measured from the wetland boundary as surveyed in
the field pursuant to the requirements of subsection M4a of this Section, Methodology.
c. Standard Buffer Zone Widths:
i. The width of the required wetland buffer zone shall be determined according to the wetland
category. The buffer zone required for all regulated wetlands is determined by the classification of
the wetland. If standard buffer widths cannot be met, and buffer reductions per subsection M6e of
this Section and buffer averaging per subsection M6f of this Section cannot be accomplished, a
variance to buffer requirements may be requested per subsection N of this Section, Alternates,
Modifications and Variances, and RMC 1-9-2508, Variance Procedures. If the criteria in subsection
M6d of this Section are met, standard buffers may be increased.
Wetland Category Standard Buffer
Category 1 100 feet
Category 2 50 feet
Category 3 25 feet <
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 65 of 158
ii. To protect the buffer functions, the Reviewing Official shall condition permits as appropriate to the
nature of the development. Conditions of approval may include, but are not limited to, the following:
(a) Fencing pursuant to subsection E4e of this Section, plant materials, and signage pursuant to subsection E4f of this Section,
to limit pet and human disturbance;
(b) Directing lights from buildings or parking areas, or noise-generating activities, away from the wetland;
(c) Implementing water quality treatment measures required in RMC 4-6-030, Drainage (Surface Water) Standards;
(d) Avoidance of buffer disturbance and retention of the buffer in a natural condition consistent with subsection M6a of this
Section.
d. Increased Wetland Buffer Zone Width: Each applicant shall document in required wetland
assessments whether the criteria in subsections M6d(i) through (iv) of this Section are or are not met and
increased wetland buffers are warranted. Based on the applicant's report or third party review, the
Responsible Official may require increased standard buffer zone widths in unique cases, i.e.,
endangered species, very fragile areas, when a larger buffer is necessary to protect wetlands functions
and values. Such determination shall be attached as a condition of project approval. Analysis shall be
prepared as directed in subsection M6d(v) of this section, and notification shall be given pursuant to
criteria in subsection M6d(vi) of this Section.
i. The wetland is used by species listed by the Federal or the State government as threatened,
endangered and sensitive species and State-listed priority species, essential habitat for those
species or has unusual nesting or resting sites such as heron rookeries or raptor nesting trees or
evidence thereof; or
ii. The subject property, or nearby lands to which the subject property drains in route to a wetland,
are susceptible to severe erosion, and erosion control measures will not effectively prevent adverse
wetland impacts; or
iii. The subject property or nearby lands to which the subject property drains in route to a wetland
have minimal vegetative cover or slopes greater than fifteen percent (15%) and conditions cannot be
restored to prevent adverse wetland impacts; or
iv. Wetland-dependent wildlife species are observed to be present in the wetland, and may require
larger buffers based upon the evaluation in subsection M6d(v) of this Section; and
v. For proposals meeting any of the criteria in subsections M6d(i) to (iv) of this Section, buffers are
established using a site specific evaluation and documentation of buffer adequacy based upon The
Science of Wetland Buffers and Its Implications for the Management of Wetlands, McMillan 2000,
Wetlands in Washington State Volume 2: Guidance for Protecting and Managing Wetlands, ~ 1W f Appendix BC (Hruby, et al., 2005), or similar approaches; and
vi. Notification is given consistent with subsection FB of this Section.
If p// f'> ~ Reduction of Buffer Width: Based upon an applicant's request, the Administrator may approve a
II I -reduction in the standard wetland buffer zone widths on a case-by-case basis for C ass 1 and 2 wetlands
C ~ ,.. {// where the applicant can demonstrate compliance with subsections M6e(i) and (iii) or (ii) and ui) of this 0 r7-Section. Such determination and evidence shall be included in the application file and public notification
shall be given in accordance with M6e(iv) of this Section. Conditions may be applied in accordance with
subsection M6e(v) of this Section.
i. The buffer area land is extensively vegetated and has less than fifteen percent (15%) slopes and
no direct or indirect, short-term or long-temn, adverse impacts to regulated wetlands, as determined
by the City, will result from a regulated activity. The City's detemnination shall be based on specific
site studies by recognized experts. The City may require long-term monitoring of the project and
subsequent corrective actions if adverse impacts to regulated wetlands are discovered; or
ii. The project includes a buffer enhancement plan using native vegetation and substantiates that the
enhanced buffer will be equal to or improve the functional attributes of the buffer. An enhanced
buffer shall not result in greater than a twenty five percent (25%) reduction in the buffer width.
Greater buffer width reductions require review as a variance per subsection N3 of this Section.
iii. The proposal shall rely upon a site specific evaluation and documentation of buffer adequacy
based upon The Science of Wetland Buffers and Its Implications for the Management of Wetlands,
McMillan 2000, or similar approaches. The proposed buffer standard is based on consideration of
the best available science as described in WAC 365-195-905; or where there is an absence of valid
scientific information, the steps in RMC 4-9-;2_50F are followed.
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Chapter 3 ENVIRONMENTAL REGULA TIO NS AND OVERLAY DISTRJCTS Page 66 of 158
iv. Public notification of the buffer reduction determination shall be given as follows:
(a) For applications that are not subject to notices of application per chapter 4-8 RMC, notice of the buffer determination shall
be given by posting the site and notifying parties of record, if any, in accordance with chapter 4-8 RMC.
(b) For applications that are subject to notices of application, the buffer determination or request for determination shall be
included with notice of application. Upon determination, notification of parties of record, if any, shall be made.
v. The Reviewing Official shall apply conditions of approval equivalent or greater than those
identified in subsection M6c(ii) of this Section to ensure that the reduced buffer width protects the
functions and values of the associated wetlands.
f. Averaging of Buffer Width: Standard wetland buffer zones may be modified by averaging buffer
widths. Upon applicant request, wetland buffer width averaging may be allowed by the Department
Administrator only where the applicant demonstrates all of the following:
')
i. That the wetland contains variations in ecological sensitivity or there are existing physical
improvements in or near the wetland and buffer; and
ii. That width averaging will not adversely impact the wetland function and values; and
iii. That the total area contained within the wetland buffer after averaging is no less than that
contained within the required standard buffer prior to averaging; and
iv. A site specific evaluation and documentation of buffer adequacy based upon The Science of
Wetland Buffers and Its Implications for the Management of Wetlands, McMillan 2000, or similar
approaches have been conducted. The proposed buffer standard is based on consideration of the
best available science as described in WAC 365-195-905; or where there is an absence of valid
scientific information, the steps in RMC 4-9-250F are followed.
v. In no instance shall the buffer width be reduced by more than fifty percent (50%) of the standard
buffer or be less than twenty five feet (25') wide. Greater buffer width reductions require review as al
variance per subsection N3 of this Section and RMC 4-9-2508; and
vi. Buffer enhancement in the areas where the buffer is reduced shall be required on a case-by-case
basis where appropriate to site conditions, wetland sensitivity, and proposed land development
characteristics.
vii. Notification may be required pursuant to subsection F8 of this Section.
7. Wetlands -Native Growth Protection Areas: As a condition of any approval issued pursuant to this
Section for any development permit, the property owner shall be required to create a separate native growth
protection area containing the areas determined to be wetland and/or wetland buffer in field investigations
performed pursuant to subsection M4 of this Section, Delineation of Regulatory Edge of Wetlands, and
subsection MS of this Section, Determination of Wetland Classification. Native growth protection areas shall
be established pursuant to subsection E4 of this Section.
8. Wetland Changes -Alternative Methods of Development: If wetland changes are proposed for a non-
exempt activity, the applicant shall evaluate alternative methods of developing the property using the
following criteria in this order and provide reasons why a less intrusive method of development is not feasible.
In determining whether to grant permit approval per subsection M2 of this Section, General Standards for
Permit Approval, the Reviewing Official shall make a determination as to whether the feasibility of less
intrusive methods of development have been adequately evaluated and that less intrusive methods of
development are not feasible:
a. Avoid any disturbances to the wetland or buffer;
b. Minimize any wetland or buffer impacts;
c. Restore any wetlands or buffer impacted or lost temporarily; and
d. Compensate for any permanent wetland or buffer impacts by one of the following methods:
i. Restoring a former wetland and provide buffers at a site once exhibiting wetland characteristics to
compensate for wetlands lost;
ii. Creating new wetlands and buffers for those lost; and
iii. In addition to restoring or creating a wetland, enhancing an existing degraded wetland to
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS
compensate tor Jost functions and values.
9. Compensating for Wetlands Impacts:
Page 67 of 158
a. Goal: The overall goal of any compensatory project shall be no net Joss of wetland function and
acreage and to strive for a net resource gain in wetlands over present conditions. The concept of "no net
loss" means lo create, restore and/or enhance a wetland so that there is no reduction lo total wetland
acreage and/or function.
b. Plan Requirements: The applicant shall develop a plan that provides for land acquisition,
construction, maintenance and monitoring of replacement wetlands that recreate as nearly as possible
the wetland being replaced in terms of acreage, function, geographic location and setting, and that are
equal to or larger than the original wetlands.
c. Plan Performance Standards: Compensatory mitigation shall follow an approved mitigation plan
pursuant to subsections M8 lo M10 of this Section and shall meet the minimum performance standards
in subsection F8 of this Section.
d. Acceptable Mitigation -Permanent Wetland Impacts: Any person who alters regulated wetlands
shall restore or create equivalent areas or greater areas of wetlands than those altered in order to
compensate for wetland losses. Enhancement of wetlands may be provided as mitigation if it is
conducted in conjunction with mitigation proposed to create or restore a wetland in order to maintain "no
net loss" of wetland acreage. Subsections M10 through M12 provide further detail on wetland restoration,
creation, and enhancement.
e. Restoration, Creation, or Combined Enhancement Required -Compensation for Permanent
Wetland Impacts: As a condition of any permit allowing alteration of wetlands and/or wetland buffers, or
as an enforcement action, the City shall require that the applicant engage in the restoration or creation of
wetlands and their buffers (or funding of these activities) in order to offset the impacts resulting from the
applicant's or violator's actions. Enhancement in conjunction with restoration or creation may be allowed
in order to offset the impacts resulting from an applicant's actions. Enhancement is not allowed as
compensation for a violator's actions.
f. Compensating for Temporary Wetland Impacts: Where wetland disturbance has occurred during
construction or other activities, see subsection C5f(ii) of this Section.
g. Mitigation Bank Agreement -Glacier Park Company: Pursuant lo the Wetland Mitigation Bank
Agreement between the City and the Glacier Park Company, King County recording number
9206241805, wetland alteration and wetland mitigation shall be conducted in accordance with the
agreement.
10. etland Compensation -Restoration, Creation, and Enhance e applicant may propose
mitiga approach that includes restoration or creation solely or co ines res ration or creation with
enhance nt. The City may require one mitigation approach in fav of another it is determined that:
greater probability of success in ensuring no ne loss of wetland acreage, functions,
a. Creation or Resto !ion Proposals: Any applican proposing to alter wetla
restore wetlands or ere e new wetlands, with priori~ rrst for on-site restoratio
second, within the draina e basin, in order to compe sate for wetland losses.
include restoring lost hydr ogic, water quality and b ologic functions.
b. Compliance with Goals: plicants proposing restore or create wetland
restoration or creation plan co forms to the purpo s and requirements of this
regional goals of no net Joss of etlands.
ds may propo to
or creation a then
estoration ac vities must
how the
stablished
c. Category: Where feasible, ere ed or restore wetlands shall be a higher ca egory Iha the altered
wetland. In no cases shall they be I wer, except s follows: For impacts to Cat ory 1 s ub-scrub and
emergent wetlands, if it is infeasible t create or restore a site to become a Cat gory 1 etland, the
Administrator may allow for creation/re ratio of high quality Category 2 wetla ds at ne hundred fifty
percent (150%) of the normally required c ran/replacement ratios of Category 1 sh b-scrub or
emergent wetlands, within the basin.
Chapter 3 ENVIRONMENTAL REGULA TIO NS AND OVERLAY DTSTRJCTS Page I of5
10. Wetland Compensation -Restoration, Creation, and Enhancement: The applicant may propose a
mitigation approach that includes restoration or creation solely or combines restoration or creation with
enhancement. The City may require one mitigation approach in favor of another if it is determined that:
a. There is a greater probability of success in ensuring no net loss of wetlands acreage, functions, and
values; and
b. The mitigation approach can be accomplished on-site rather than off-site.
11. Wetlands Creation and Restoration:
a. Creation or Restoration Proposals: Any applicant proposing to alter wetlands may propose to
restore wetlands or create new wetlands, with priority first for on-site restoration or creation and then
second, within the drainage basin, in order to compensate for wetland losses. Restoration activities must
include restoring lost hydrologic, water quality and biologic functions.
b. Compliance with Goals: Applicants proposing to restore or create wetlands shall identify how the
restoration or creation plan conforms to the purposes and requirements of this Section and established
regional goals of no net loss of wetlands.
c. Category: Where feasible, created or restored wetlands shall be a higher category than the altered
wetland. In no cases shall they be lower, except as follows: For impacts to Category 1 shrub-scrub and
emergent wetlands, if it is infeasible to create or restore a site to become a Category 1 wetland, the
Administrator may allow for creation/restoration of high quality Category 2 wetlands at one hundred fifty
percent (150%) of the normally required creation/replacement ratios of Category 1 shrub-scrub or
emergent wetlands, within the basin.
d. Design Criteria: Requirements for wetland restoration or creation as compensation areas shall be
determined according to the function, acreage, type and location of the wetland being replaced.
Compensation requirements should also consider time factors, the ability of the project to be self-
sustaining and the projected success based on similar projects. Wetland functions and values shall be
calculated using the best professional judgment of a qualified wetland ecologist using the best available
techniques. Multiple or cooperative compensation projects may be proposed for one project in order to
best achieve the goal of no net loss. Restoration or creation must be within the same drainage basin.
e. Acreage Replacement Ratio: The ratios listed in subsection M11 e(i) of this Section, Ratios for
Wetlands Creation or Restoration, apply to all Category 1, 2, or 3 wetlands for restoration or creation
which is in-kind, on-or off-site, timed prior to alteration, and has a high probability of success. The
required ratio must be based on the wetland category and type that require replacement. Ratios are
determined by the probability of recreating successfully the wetland and the inability of guarantees of
functionalitv, longevity, and duplication of tvne and/or functi ons.
i. RATIOS FOR WETLANDS CREATION OR RESTORATION:
Wetland Category Vegetation Type Creation/Restoration Ratio
Forested 6 times the area altered.
Category 1 Scrub-shrub 3 times the area altered.
Emergent 2 times the area altered.
Forested 3 times the area altered.
Category 2 Scrub-shrub 2 times the area altered.
Emergent 1.5 times the area altered.
Forested 1.5 times the area altered.
Category 3 Scrub-shrub 1.5 times the area altered.
Emergent 1 .5 times the area altered.
f. Increased Creation/Restoration/Replacement Ratios: The Reviewing Official may increase the
ratios under the following circumstances: uncertainty as to the probable success of the proposed
restoration or creation; significant period of time between destruction and replication of wetland functions;
projected losses in functional value; or off-site compensation. The requirement for an increased
replacement ratio will be determined through SEPA review, except in the case of remedial actions
resulting from illegal alterations where the Administrator or Environmental Review Committee may
require increased wetland replacement ratios.
g. Decreased Creation/Restoration/Replacement Ratios:
i. Category 1: The Reviewing Official may decrease the ratios for Category 1 forested and scrub-
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 2 of5
shruiJ wetlands to 2.0 times the area altered, and to 1.5 times the area altered for emergent
wetlands, provided the applicant has successfully replaced the wetland prior to its filling and has
shown that the replacement is successfully esta!Jlished for five (5) years.
ii. Category 2: The Reviewing Official may decrease the ratios for Category 2 forested and scrulJ-
shrulJ wetlands to 1.5 times the area altered provided the applicant has successfully replaced the
wetland prior to its filling and has shown that the replacement is successfully estalJlished for two (2)
years. Ratios for Category 2 emergent wetlands may IJe reduced to 1 .25 times the area altered
provided the applicant has successfully replaced the wetland prior to its filling and has shown that
the replacement is successfully established for two (2) years.
iii. Category 3:
(1) The Reviewing Official may decrease the ratios for Category 3 emergent wetlands to 1.0 times the area altered provided
the applicant has successfully replaced the wetland prior to its filling and has shown that the replacement is successfully
established for twelve (12) months. Ratios for Category 3 scrub-shrub and forested wetlands may be reduced to 1.25 times the
area altered provided the applicant has successfully replaced the wetland prior to its filling and has shown that the
replacement is successfully established for two (2) years.
(2) If the applicant can aggregate two (2) or more Category 3 wetlands, each less than ten thousand (10,000) square feet, into
one wetland, the replacement ratio shall be reduced to 1:1. If the combined wetland would be rated as a Category 2 wetland
as a result of the combination, the buffer requirement may be reduced to twenty five feet (25') minimum provided the buffer is
enhanced.
h. Category 3 Replacement Option: The applicant, at his/her expense, may select to use accepted /
Federal or State methods to establish the functions and values for the Category 3 wetland being --C--
replaced in lieu of replacement by acreage only. A third party review, funded by the applicant, and hired
and managed by the City, shall review and verify the reports. Dependent upon the results of the functions
and values evaluation, a Category 3 wetland may be replaced by assuring that alt the functions and
values are replaced in another location, within the same basin.
i. Minimum Restoration/Creation Ratio: Unless allowed by subsection M11g of this Section,
restoration or creation ratios may only be reduced by modification or variance pursuant to subsection N
of this Section, Alternates, Modifications and Variances, and RMC 4-9-2508, Variance Procedures, and
RMC 4-9-2500, Modification Procedures. In order to maintain no net loss of wetland acreage, in no case
shall the restoration or creation ratio be less than 1: 1. This minimum ratio may not be modified through
the modification or variance process.
12. Wetland Enhancement:
a. Enhancement Proposals -Combined with Restoration and Creation: Any applicant proposing to
alter wetlands may propose to enhance an existing degraded wetland, in conjunction with restoration or
creation of a wetland in order to compensate for wetland losses. Wetland enhancement shall not be
allowed as compensation if it is not accomplished in conjunction with a proposal to restore or create a
wetland.
b. Evaluation Criteria: A wetland enhancement compensation project may be approved by the
Reviewing Official; provided, that enhancement for one function will not degrade another function unless
the enhancement would provide a higher functioning wetland with greater or multiple environmental
benefits. For example, an enhancement may degrade haiJitat for one wildlife species but overall it may
result in a wetland that provides higher function to a wider variety of wildlife species. Wetland function
assessment shall be conducted in conformance with accepted Federal or State methodologies.
c. Wetlands Chosen for Enhancement: An applicant proposing to alter wetlands may propose to
enhance an existing Category 2 or 3 wetland. Existing Category 1 wetlands shall not be enhanced to
compensate for wetland alteration unless the wetland selected for enhancement is a Category 1 wetland
only by virtue of its acreage and three (3) vegetation classes, where the existing vegetation is
characterized partly or wholly by invasive wetland species.
d. Mitigation Ratios: Wetland alterations shall be created, restored and enhanced using the formulas in
subsection M12d(i), Ratios for Welland Restoration or Creation plus Enhancement. The following is an
example of use of the formulas below:
If one acre of Category 2, forested wetland, were proposed to be removed, the creation/replacement
ratio (subsection M11 e(i) of this Section) requires that three (3) acres of forested Category 2 wetland be
restored or created; if wetland enhancement were proposed (subsection M12d(i) of this Section) for the
Category 2, forested wetland, 1.5 acres of forested Category 2 wetland would have to IJe
created/restored and two (2) acres of forested Category 2 wetland enhanced, possibly in a different part
of the same wetland.
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 3 of 5
i. RATIOS FOR WETLAND RESTORATION OR CREATION PLUS ENHANCEMENT
Wetland Category Vegetation Type Restoration or Creation Ratio Enhancement Ratio
Forested 3 times the area altered plus 3.5 times the area altered
Category 1 Scrub-shrub 1.5 times the area altered plus 2 times the area altered
Emergent 1 times the area altered plus 1 .5 times the area altered
Forested 1.5 times the area altered plus 2 times the area altered
Category 2 Scrub-shrub 1 times the area altered plus 1.5 times the area altered
Emergent 1 times the area altered plus 1 times the area altered
Forested 1 times the area altered plus 1 times the area altered
Category 3 Scrub-shrub 1 times the area altered plus 1 times the area altered
Emergent 1 times the area altered plus 1 times the area altered
e. Ratio Modification and Minimum Restoration/Creation Ratio:
i. An applicant may propose an increased creation or restoration ratio and a decreased
enhancement ratio if the total combined ratio is maintained overall. Restoration/creation or
enhancement ratios shown in subsection M 12d of this Section may only be reduced by modification
or variance pursuant to subsection N3 of this Section, Alternatives, Modifications and Variances,
and RMC 4-9-2508, Variance Procedures, and RMC 4-9-2500, Modification Procedures. In order to
maintain no net loss of wetland acreage, in no case shall the restoration or creation ratio be less
than 1 :1. This minimum ratio may not be modified through the variance process.
ii. The Reviewing Official may increase the ratios under the following circumstances: uncertainty as
to the probable success of the proposed restoration or creation or enhancement proposal; significant
period of time between destruction and replication of wetland functions; projected losses in
functional value; or off-site compensation. The requirement for an increased mitigation ratio will be
determined through SEPA review, except in the case of remedial actions resulting from illegal
alterations where the Administrator or Environmental Review Committee may require increased
mitigation ratios.
13. Out-of-Kind Replacement: Out-of-kind replacement may be used in place of in-kind compensation only
where the applicant can demonstrate to the satisfaction of the Reviewing Official that:
a. The wetland system is already significantly degraded and out-of-kind replacement will result in a
wetland with greater functional value; or
b. Scientific problems such as exotic vegetation and changes in watershed hydrology make
implementation of in-kind compensation impossible or unacceptable; or
c. Out-of-kind replacement will best meet identified regional goals (e.g., replacement of historically
diminished wetland types).
14. Off-Site Compensation:
a. When Permitted: Off-site compensation may be provided in lieu of on-site compensation only where
the applicant can demonstrate to the satisfaction of the Responsible Official that:
i. The hydrology and ecosystem of the original wetland and those abutting or adjacent land and/or
wetlands which benefit from the hydrology and ecosystem will not be substantially damaged by the
on-site loss; and
ii. On-site compensation is not feasible due to problems with hydrology, soils, or other factors; or
iii. Compensation is not practical due to potentially adverse impact from surrounding land uses; or
iv. The proposed wetland functions at the mitigation site are significantly greater than the wetland
functions that could be reasonably achieved with on-site mitigation, and there is no significant loss of
function on-site, i.e., at the development project site; or
v. Established regional goals for flood storage, flood conveyance, habitat or other wetland functions
have been addressed and strongly justify location of compensatory measures at another site.
b. Locations: Any off-site compensation shall follow the preferences in subsections M14b(i) to (iii) of this
Section. Basins and subbasins are indicated in subsection Q of this Section, Maps:
Chapter 3 ENVIRONMENT AL REGULATIONS AND OVERLAY DISTRICTS Page 4 of
i. Off-Site Mitigation within Same Drainage Subbasin as Subject Site: Off-site mitigation may be
allowed when located within the same drainage subbasin as the subject site subject to criteria in
subsection M 14a of this Section;
ii. Off-Site Mitigation within Same Drainage Basin within City Limits: Off-site mitigation may be
allowed when located within the same drainage basin within the Renton City limits if it achieves
equal or improved ecological functions within the City over mitigation within the same drainage
subbasin as the project, and shall be subject to criteria in subsection M14a of this Section;
iii. Off-Site Mitigation within the Same Drainage Basin Outside the City Limits: Off-site
mitigation may be allowed when located within the same drainage basin outside the Renton City
limits if it achieves equal or improved ecological functions over mitigation within the same drainage
basin within the Renton City limits and it meets City goals, and shall be subject to criteria in
subsection M14a of this Section.
c. Siting Recommendations: In selecting compensation sites, the City encourages applicants to pursue
siting compensation projects in disturbed sites which were formerly wetlands, and especially those areas
which would result in a series of interconnected wetlands.
d. Timing: Compensatory projects shall be substantially completed and approved by the City prior to the
issuance of an occupancy pem,it. Construction of compensation projects shall be timed to reduce
impacts to existing wildlife and flora. The Reviewing Official may elect to require a surety device for
completion of construction.
15. Cooperative Wetland Compensation: Mitigation Banks or Special Area Management Programs
(SAMP):
a. Applicability: The City encourages and will facilitate and approve cooperative projects wherein a
single applicant or other organization with demonstrated capability may underlake a compensation
project under the following circumstances:
i. Restoration or creation on-site may not be feasible due to problems with hydrology, soils, or other
factors; or
ii. Where the cooperative plan is shown to better meet established regional goals for flood storage,
flood conveyance, habitat or other wetland functions.
b. Process: Applicants proposing a cooperative compensation project shall:
i. Submit a permit application;
ii. Demonstrate compliance with all standards;
iii. Demonstrate that long-term management will be provided; and
iv. Demonstrate agreement for the project from all affected properly owners of record.
c. Mitigation Banks: Mitigation banks are defined as sites which may be used for restoration, creation
and/or mitigation of wetland alternatives from a different piece of properly than the property to be altered
within the same drainage basin. The City of Renton maintains a mitigation bank. A list of City mitigation
bank sites is maintained by the Planning/Building/Public Works Department. With the approval of the
Planning/Building/Public Works Department, non-City-controlled mitigation banks may be established
and utilized.
d. Special Area Management Programs: Special area management programs are those wetland
programs agreed upon through an interjurisdictional planning process involving the U.S. Army Corps of
Engineers, the Washington State Department of Ecology, any affected counties and/or cities, private
property owners and other parties of interest. The outcome of the process is a regional wetlands permit
representing a plan of action for all wetlands within the special area.
e. Compensation Payments to Mitigation Bank: Compensation payments, amount to be determined
by the Reviewing Official, received as part of a mitigation or creation bank must be received prior to the
issuance of an occupancy pem,it.
16. Mitigation Plans:
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 5 of5
a. Required for Restoration, Creation and Enhancement Projects: All wetland restoration, creation,
and enhancement in conjunction with restoration and creation projects required pursuant to this Section
either as a permit condition or as the result of an enforcement action shall follow a mitigation plan
prepared by qualified wetland specialists approved by the City.
b. Timing for Mitigation Plan Submittal and Commencement of any Work: See subsection FB of this
Section.
c. Content of Mitigation Plan: Unless the City, in consultation with qualified wetland specialists,
determines, based on the size and scope of the development proposal, the nature of the impacted
wetland and the degree of cumulative impacts on the wetland from other development proposals, that the
scope and specific requirements of the mitigation plan may be reduced, the mitigation plan shall address
all requirements in RMC 4-8-120023, Wetland Mitigation Plan, and subsection F8 of this Section.
d. Perfonnance Surety: As a condition of approval of any mitigation plan, the Reviewing Official shall
require a performance surety per RMC 4-1-230 and subsection G of this Section. (Amd. Ord. 4851, 8-7-
2000; Ord. 5137, 4-25-2005)
N. ALTERNATES, MODIFICATIONS AND VARIANCES:
1. Alternates:
a. Applicability: See RMC 4-9-250E.
2. Modifications:
a. Applicability: The Department Administrator may grant modifications, per RMC 4-9-250D1,
Application Time and Decision Authority, in the following circumstances:
i. Aquifer Protection -Modifications: The Department will consider modification applications in
the following cases:
(a) The request is to find that a standard is inapplicable to that activity, facility, or development permit due to the applicant's
proposed methods or location; or
(b) The request is to modify a specific standard or regulation due to practical difficulties; and
(c) The request meets the intent and purpose of the aquffer protection regulations.
Based upon application of the above tests in subsection N2a(i)(a), (b), and (c) of this Section, applications which are
considered appropriate for review as modifications are subject to the procedures and criteria in RMC 4-9-2500, Modification
Procedures. Requests to modify regulations or standards which do not meet the above tests shall be processed as variances.
(d) In addnion to the criteria of RMC 4-9-2500, Modification Procedures, the following criteria shall apply: The proposed
modification is based on consideration of the best available science as described in WAC 365-195-905; or where there is an
absence of valid scientific information, the steps in RMC 4-9-250F are followed.
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Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS
N. ALTERNATES, MODIFICATIONS AND VARIANCES:
Page I of2
1. Alternates:
a. Applicability: See RMC 4-9-250E.
2. Modifications:
a. Applicability: The Department Administrator may grant modifications, per RMC 4-9-25.QD1,
Application Time and Decision Authority, in the following circumstances:
i. Aquifer Protection -Modifications: The Department will consider modification applications in
the following cases:
(a) The request is to find that a standard is inapplicable to that activity, facility, or development permit due to the applicant's
proposed methods or location; or
(b) The request is to modify a specific standard or regulation due to practical difficulties; and
(c) The request meets the intent and purpose of the aquifer protection regulations.
Based upon application of the above tests In subsection N2a(i)(a), (b), and (c) of this Section, applications which are
considered appropriate for review as modifications are subject to the procedures and criteria in RMC 4-9-250D, Modification
Procedures. Requests to modify regulations or standards which do not meet the above tests shall be processed as variances.
(d) In addition to the criteria of RMC 4-9-250D, Modification Procedures, the following criteria shall apply: The proposed
modification is based on consideration of the best available science as described in WAC 365-195-905; or where there is an
absence of valid scientific information, the steps in RMC 4-9-250F are followed.
ii. Geologic Hazards -Modifications: An applicant may request that the Administrator grant a
modification to allow:
(a) Regrading of any slope which was created through previous mineral and natural resource recovery activities or was created
prior to adoption of applicable mineral and natural resource recovery regulations or through public or private road installation or
widening and related transportation improvements, railroad track installation or improvement, or public or private utility
installation activities;
(b) Filling against the toe of a natural rock wall or rock wall created through mineral and natural resource recovery activities or
through public or private road installation or widening and related transportation improvements, railroad track installation or
improvement or public or private utility installation activities; and/or
(c) Grading to the extent that it eliminates all or portions of a mound or to allow reconfiguration of protected slopes created
through mineral and natural resource recovery activities or public or private road installation or widening and related
transportation improvements, railroad track installation or improvement, or public or private utility installation activities.
The following procedures shall apply to any of the above activities:
(1) The applicant shall submit a geotechnical report describing any potential impacts of the proposed regrading and any
necessary mitigation measures;
(2) All submitted reports shall be independently reviewed by qualified specialists selected by the City at the applicant's
expense;
(3) The Department Administrator may grant, condition, or deny the request based upon the proposal's compliance with the
applicable modification criteria of RMC 4-9-250D; and
(4) Any slope which remains forty percent (40%) or steeper following site development shall be subject to all applicable
geologic hazard regulations for steep slopes and landslide hazards, in this Section.
(5) In addition to the criteria of RMC 4-9-250D, Modification Procedures, the following criteria shall apply: The proposed
modification is based on consideration of the best available science as described in WAC 365-195-905; or where there is an
absence of valid scientific information, the steps in RMC 4-9-250F are followed.
iii. Wetlands -Modifications: An applicant may request that the Administrator grant a modification
as follows:
(a) Modifications may be requested for a reduction in creation/restoration or enhancement ratios for a Category 3 wetland;
however, the creation/restoration ratio shall not be reduced below 1:1.
(b) In addition to the criteria of RMC 4-9-250D, Modification Procedures, the following criteria shall apply:
(1) The proposal will result in no-net loss of wetland or buffer area and functions.
(2) The proposed modification is based on consideration of the best available science as described in WAC 365-195-905; or
where there is an absence of valid scientific information, the steps in RMC 4-9-250F are followed.
iv. Streams -Modifications: An applicant may request that the Administrator grant a modification
as follows:
(a) Modifications may be requested for a reduction in stream buffers for Class 2 or 3 watercourses proposed to be daylighted,
below the stream buffer reduction levels of subsection L5c of this Section.
(b) In addition to the criteria of RMC 4-9-250D, Modification Procedures, the following criteria shall apply:
(1) The buffer is lowered only to the amount necessary to achieve the same amount of development as without the daylighting.
(2) The buffer width is no Jess than fifty feet (50') on a Class 2 watercourse and twenty five feet (25') on a Class 3 watercourse.
(3) The proposed modification is based on consideration of the best available science as described in WAC 365-195-905; or
where there is an absence of valid scientific information, the steps in RMC 4-9-250F are followed.
3. Variances:
http://www.codepublishing.com/W A/Renton/renton04/renton0403.html 6/6/2007
Chapter 3 ENVIRONMENTAL REGULATIONS AND OVERLAY DISTRICTS Page 2 of2
a. Aquifer Protection -Variance:
i. Applicability: If an applicant feels that the strict application of this Section would deny all
reasonable use of the property or would deny installation of public transportation or utility facilities
determined by the public agency proposing these facilities to be in the best interest of the public
health, safety and welfare, the applicant of a development proposal may apply for a variance.
ii. Application Submittal: An application for a variance shall be filed with the Development Services
Division.
iii. Review Authority: A variance shall be decided by the Hearing Examiner based on the standards
set forth in RMC 4-9-2508, Variance Procedures.
b. Flood Hazards -Variances:
i. Applicability: Refer to RMC 4-9-2508.
c. Geologic Hazards, Habitat Conservation, Streams and Lakes -Classes 2 to 4, and Wetlands -
Variance:
i. Applicability: If an applicant feels that the strict application of this Section would deny all
reasonable use of the property containing a critical area or associated buffer, or would deny
installation of public transportation or utility facilities detenmined by the agency proposing these
facilities to be in the best interest of the public health, safety and welfare, the public agency or an
applicant of a development proposal may apply for a critical areas variance.
ii. Application Submittal: An application for a critical areas variance shall be filed with the
Development Services Division.
Iii. Review Authority: Variances shall be determined administratively by the Department
Administrator, or by the Hearing Examiner, as indicated in RMC 4-9-2508. (Amd. Ord. 4851, 8-7-
2000; Ord. 5137, 4-25-2005)
O.APPEALS:
1. General: See RMC 4-8-070, Authority and Responsibilities, and RMC 4-8-110.
2. Record Required -Flood Hazards: The Department Administrator or his/her designee, the Building
Official, shall maintain the records of all appeal actions and report any variances to the Federal Insurance
Administration upon request. (Amd. Ord. 4851, 8-7-2000; Ord. 4963, 5-13-2002; Ord. 5137, 4-25-2005)
http://www.codepubJishing.com/W A/Renton/renton04/renton0403 .html 6/6/2007
Wetland Delineation Report Concept Eng.
~H=an=co=,k~S=ho=rt~P=la<~----------------------------~8~/29/Q7
EXHIBIT E:
COLOR PHOTOGRAPHS
.·t. ~--.
Photo 1 : Overview of Wetland "W " looking west.
The stream is in a ditch between the mowed grass
Photo 2: View of the north end of the
stream looking north. The stream
lea ves the site through a cu lvert.
J:\AUT OCAD\PROJECTS\2005\25332\Engineering\A nalys,s -Cal cs\Documents\Word\Ph otos for Report.doc
Photo 3: View of Sample Point 1.
This is within Wetland "W ".
Photo 4. View of Sample Point 2.
This is just outside of Wetl a nd "W ".
The soils were not hydric and the plant
community w as not hydrophytic.
J :\AUT OCAD\PROJ ECTS\ 2005 \25 332\E ng,neering\Ana I ys ,s-Ca lcs\Documents\ Word \Photos for Repor t .doc
Photo 5: View of Sample Point 3
located within Wetland "W".
Photo 6: View of Sample Point 4
located just outside of Wetland "W".
The plant community was hydrophytic
but the soils w ere not hyd ric .
J·\AUTOCAD\PROJ ECTS\2005\25332\Engineering\Analysis-Calcs\Docu ments\W o rd \Photos for Re port.doc
Photo 7. View of Sample Point 5,
loc ated between Wetlands "W"
and "Y".
Photo 8: View of Samp le Point 6,
located within Wetland "Y".
J :\AUTOCAD\PROJECTS\2005\25332\Engineerong\Analysis-Calcs\Doc uments\Word\Photos f or Report.doc
Wetland Delineation Report
Hancock Short Plat
EXHIBIT F:
WETLAND FLAGGING SURVEY
(ATTACHED IN POCKET)
Concept Fng.
8/29/07
Wetland Delineation Report
Hancock Sho.rt.PJac__t ----------------
EXHIBITG:
CERTIFICATIONS
Concept Eng.
8129/07
THE EVERGREEN STATE COLLEGE
In recognition of completion
of the course of study approved by the faculty
Cltristoplter J<obin _Holcomb
is awarded the degree
BACHELOR OF ARTS
with all its honors, privileges and obligations, Conferred at Olympia,
Washington, the Twenty-first day of March,
Nineteen hundred and Ninety-Two. ~
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CHAIR, BOA
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CERTIFIES THAT
Cliris (j{J{o{com6
SUCCESSFULLY COMPLETED THE 2005-2006
Certificate <Program in
Wetfand Science and 9vtanagement
THIS TWENTY-FIRST DAY OF JUNE IN THE YEAR
David Szatmary
Vice Provost
UW Extension
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CONCEPT ENGINEERING, INC.
41111111111. 455 Rainier Boulevard North ---,
... Issaquah, Washington 98027 . :"W _(425) 392-8055 Fax: (425) 392_~~J
' ' ' '., , . '·"~""''' ..... ~ --....1
TECHNICAL INFORMATION REPORT (TIR) /
LEVEL 1 DOWNSTREAM DRAINAGE ANALYSIS
FOR THE
SILVER KING 3-LOT CLUSTER SHORT PLAT
Located At:
11025 148'"(Nile) Avenue SE
Renton, WA 98059
Owner / Applicant / Prepared For:
Jonah-Kai Hancock
11025 148'" Avenue SE
Renton, WA 98059
(206) 234-9673
Dated:
Original: August 22, 2007 (Access from Northwest -Level 1 Downstream Drainage Analysis Only)
Revised: January 19, 2009 (Access from East -Includes TIR Portion for Prelim. Short Plat Submittal)
Concept Engineering, Inc. Job Number:
25332
Prepared By:
Mark Rigos, P.E.
TIR / Level I Downstream Analysis
January 2009
TABLE OF CONTENTS
Silver King Short Plat
CE! Job No. 25332
I. PROJECT OVERVIEW .....................••...•...•..........................•...••..................•........ .3
II. PRELIMINARY CONDITIONS SUMMARY AND CORE I SPECIAL REQUIREMENTS ...... 3
ill. OFFSITE ANALYSIS ............................................................................................. 5
IV. RETENTION/ DETENTION ANALYSIS AND DESIGN ................................................. 5
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .................................................... 5
VI. SPECIAL REPORTS AND STUDIES ......................................................................... 5
VII. BASIN AND COMMUNITY PLAN AREAS ................................................................. 5
VIII. OTHER PERMITS ................................................................................................. 5
IX. EROSION I SEDIMENTATION CONTROL DESIGN .................................................... 5
X. BOND QUANTITIES WORKSHEET, RETENTION I DETENTION FACILITY SUMMARY
SHEET, AND DECLARATION OF COVENANT .......................................................... 6
XI. MAINTENANCE AND OPERATIONS MANUAL ......................................................... 6
APPENDIX A
APPENDIXB
APPENDIXC
APPENDICES
LEVEL 1 DOWNSTREAM ANALYSIS (8/22/2007)
TIR WORKSHEET
STORM DRAINAGE CALCULATIONS
MAINTENANCE AND OPERATIONS MANUAL
T[R / Level 1 Downstream Analysis
Januarv 2009
I. PROJECT OVERVIEW
Silver King Sho11 Plat
CE! Job No. 25332
This drainage report/ level I downstream analysis was prepared per the City of Renton Short Plat
Submittal Requirements and per Renton's 2/7/2008-Public Works Memorandum received at the Pre-
Application Meeting (Pre-App 08-008). Formerly this project was known as the Jonah-Kai Hancock Short
Plat, but has been renamed to the Silver King Short Plat. This report is the culmination of a downstream
and onsite drainage analysis for the proposed 3-lot cluster short plat on a 0.81-acre site. The site is located
at 11025 148'h Avenue SE Renton, WA 98059 and in Section 3, Township 23 North, Range 5 East, W.M.
A downstream drainage analysis is required to establish the downstream drainage path and determine if
downstream drainage problems exist within V, mile from the site. The downstream analysis was prepared
to satisfy Core Requirement #2 per the 1990 King County Surface Water Design Manual (1990 SWDM).
Renton has adopted the 1990 SWDM. The downstream analysis is provided in Appendix A. A Technical
Information Report (TIR) Worksheet is in Appendix B.
Originally, access to the site was proposed from the northwest in a right-of-way stem branching off SE
111 '" Street. However, access from that direction necessitates a stream crossing, wetland filling, and
impacting associated buffers. So that development configuration was ended. The newly proposed access
is directly from 1481h Avenue SE (public right-of-way), which is the site's existing access. The site's
existing drainage system is essentially a seasonal swale that flows north into a culvert near the north
property line. Several small degraded wetlands are in the swale's vicinity. The existing home and
driveway do not have formal storm drainage systems. Proposed storm drainage features consist of a
collection system (catch basins), conveyance system (pipe), private easements, and an outfall dispersion
trench. The site is relatively flat and partly vegetated. Several large evergreen trees are present, primarily
in the east-central portion of the site. The site's west-central side is in a depression that contains the
seasonal drainage swale. The existing structures (home and shed/ carport) on the east side are to be
demolished to allow for the new homes.
II. PRELIMIMARY CONDITIONS SUMMARY AND CORE I SPECIAL REQUIREMENTS
Preliminary conditions of approval have not yet been received from the City of Renton. Once the
conditions are received, then this section will be updated accordingly. The 5 Core Requirements and 7
Special Requirements are addressed as follows:
Core Requirement #1 -Discharge at the Natural Location:
Future drainage from the 3 homes and driveways will be dispersed above the seasonal swale (stream). The
stream is the site's natural discharge location.
Core Requirement #2 -Offsite Analysis:
A Level I Downstream Analysis is in Appendix A.
Core Requirement #3 -Runoff Control:
This project meets the 'exemption from onsite peak runoff control' critena found on 1990 SWDM Page
1.2.3-5. The site's post-development (proposed) peak runoff rate for the JOO-year, 24-hour duration design
storm event has been calculated to be less than 0.5 cfs more than the existing-development peak runoff
rate. The calculations are in Appendix B.
Core Requirement #4 -Conveyance System:
A conveyance system has been designed for the future homes and is shown on the preliminary engineering
TJR / Level I Downstream Analysis
January 2009
plan (Cl.OJ. Permanent private easements will be created on the final short plat map.
Core Requirement #5 -Temporary Erosion and Sediment Control:
Silver King Short Plat
CEI Job No. 25332
A TESC Plan, not yet prepared, will be designed prior to the clearing and grading permit application
submittal.
Core Requirement #6 -Maintenance and Operation:
The storm drainage facilities will be privately maintained by future residents and I or a possible
homeowners association.
Core Requirement #7 -Bonds and Liability:
This will probably not be required as the storm drainage systems will be private.
Special Requirement #I -Critical Drainage Areas:
Not applicable, as this project is not in a critical drainage area to my knowledge.
Special Requirement #2 -Compliance with an Existing Master Drainage Plan:
Not applicable, as there is not an existing master drainage plan.
Special Requirement #3 -Conditions Requiring a Master Drainage Plan:
Not applicable, as this project is not located in a master drainage plan area.
Special Requirement #4 -Adopted Basin or Community Plan:
Not applicable, there are no adopted basin or community plans to my knowledge.
Special Requirement #5 -Special Water Quality Controls:
Not applicable, as the threshold for special water quality controls is not triggered.
Special Requirement #6 -Coalescing plate oil/water separators:
Not applicable, as this project contains less than 5 acres of impervious surface area.
Special Requirement #7 -Closed Depressions:
Not applicable, as this project does not drain into a closed depression.
Special Requirement #8 -Use of Lakes, Wetlands or Closed Depressions for Runoff Control:
Not applicable, as runoff control is not being used by lakes, wetlands, or closed depressions.
Special Requirement #9 -Delineation of the 100-Year Floodplain:
The I 00-year floodplain for the stream is barely above its ordinary high water marks. The stream's
upstream tributary area is very small, at only several acres at most. This study was waived by City of
Renton staff.
Special Requirement #JO-Flood Protection Facilities for Type 1 and Type 2 Streams:
Not applicable, Type I and type 2 streams are absent.
Special Requirement #11 -Geotechnical Analysis and Report:
Not applicable, this threshold is not met for the project.
Special Requirement #12: Soils Analysis and Report:
1
TIR / Level 1 Downstream Analysis
January 2009
Not applicable, the soils in the site's vicinity have been mapped.
III. OFFSITE ANALYSIS
Appendix A contains the Level 1 Downstream Drainage (Offsite) Analysis.
IV. RETENTIONIDETENTION ANALYSIS AND DESIGN
Silver King Short Plal
CEI Job No. 25332
This project is exempt from retention and detention, because the site's redevelopment adds less than 0.5
cfs increase from the site's existing condition to the site's proposed condition.
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
At this preliminary stage of the project, a conveyance system analysis has not yet been performed. The
project will generate very low stormwater flows. 6-inch diameter pipe is sufficient to convey stormwater
through the site.
VI. SPECIAL REPORTS AND STUDIES
• A wetland delineation report has been prepared by Concept Engineering, Inc. (CE!).
• A Level 1 Downstream Analysis has been prepared by CE!.
• A standard stream study has been prepared by CEL
• A supplemental stream study has been prepared by CEI.
• A critical area exemption request has been prepared by CE!.
VII. BASIN AND COMMUNITY PLAN AREAS
To my knowledge, this recently annexed area by the City of Renton does not have a drainage basin plan
area or community plan area. The site is in the May Creek Drainage Basin.
VIII. OTHER PERMITS
A right-of-way use permit will be required from King County for the utilities work in 148'" Avenue SE. A
HPA (Hydraulic Project Approval) will be required by Washington State Department of Fisheries and
Wildlife for the sewer/ stream crossing.
IX. EROSION/ SEDIMENATION CONTROL DESIGN
A TESC Plan will be designed following preliminary conditions of approval issuance from the City of
Renton. The TESC Plan will include clearing/ grading limits, a construction entrance, silt fence,
hydroseeding notes, etc. Formal sedimentation facilities are not provided.
s
TIR / Level I Downstream Analysts
January 2009
Silver King Short Plat
CE! Job No. ?5332
X. BOND QUANTITIES WORKSHEET, RETENTION/ DETENTION FACILITY
SUMMARY SHEET, AND DECLARATION OF COVENANT
These items were not provided since a formal retention / detention facility is not a part of this project.
XI. MAINTENANCE AND OPERATIONS MANUAL
Appendix C contains a maintenance and operations manual for the catch basins, pipes, and existing debris
barrier.
G
TIR i Leve! I Downstream Analysis
January 2009
APPENDIX A
Silver King Short Plat
CEI Job No. 25332
LEVEL 1 DOWNSTREAM ANALYSIS
l
. CONCEPT ENGINEERING, INC.
A: 455 Rainier Boulevard North
-Issaquah, Washington 98027
~. (425) 392-8055 Fa" (425) 392-0108
LEVEL 1 DOWNSTREAM ANALYSIS
FOR THE
JONAH-KAI HANCOCK SHORT PLAT .
Located At:
11025 148TH Ave. SE
Renton, WA 98059
Owner/ Applicant:
Jonah-Kai Hancock
11025 1481h Ave. SE
Renton, WA 98059
(206) 234-9673
Dated:
August 22, 2007
Concept Engineering, Inc. Job#:
25332
Prepared By:
lllzb
Mitchell Hogsett
Reviewed By:
Mark Rigos, P.E.
P·\2005\25332\EnginteiinglA:nal)'SJ.,-C.,ks\Dnc,11 r,en1,Q;{Jb--fl,!~~~-~l~}&l_f) /SURVEYING/ LAND USE PLANNING
Level 1 Downstream Analysis
August 22, 2007
TABLE OF CONTENTS
Jonah-Kai Hancock Short Plat
CE! #25332
TABLE OF CONTENTS .................................................................................................. 2
I. PROJECT OVERVIEW .................................................................................................. 3
II. OFFSITE ANALYSIS ...................................................................................................... 3
Task 1: Study Area Definition and Maps .......................................................... 3
Task 2. Resource Review ..................................................................................... 3
Task 3: Field Inspection ....................................................................................... 4
Task 4: Drainage System Description and Problem Descriptions ................... 4
Task 5: Mitigation ................................................................................................ S
APPENDIX: FIGURES
FIGURE!
FIGURE2
FIGURE3
FIGURE4
FIGURES
FIGURE6
FIGURE7
FIGURES
FIGURE9
FIGURE to
FIGUREll
FIGURE 12
FIGURE13
VICINITY MAP
ASSESSOR'S MAP
USGS TOPOGRAPHIC MAP
SOILS MAP
SOILS INFORMATION
WETLANDS MAP
STREAMS AND 100-YEAR FLOODPLAINS MAP
EROSION HAZARD AREAS MAP
LANDSLIDE HAZARD AREAS MAP
SEISMIC HAZARD AREAS MAP
DRAINAGE COMPLAINTS
DOWNSTREAM DRAINAGE MAP
DOWNSTREAM DRAINAGE TABLE
P:12005125332\Engine~• ing\Annlysis-Culcs\Docun:.cms\ Wtlrdl Tl R 125332 __ LE.DOC
Level I Downstream Analysis
August 22, 2007
I. PROJECT OVERVIEW
Jonah-Kai Hancock Short Plat
CE! #25332
This level 1 downstream analysis was prepared to address storm drainage related impacts from a
proposed 3-lot short plat on a 0.81-acre site at 11025 148th Ave. SE Renton, WA 98059. The
existing home will be demolished as part of this project. The site is located in Section 03, Township
23 North, Range 05 East, W.M. This analysis is necessary to establish the downstream drainage
path(s), and determine if downstream drainage problems exist within a 1/.i mile from the site.
This downstream analysis has been prepared to satisfy core requirement #2 in the 1990 King County
Surface Water Design Manual. The City of Renton currently uses the 1990 King County Surface
Water Design Manual. Site access is from 1481h Ave. SE (public right-of-way) that fronts the site
on the east. The property has a single family residence located on the east side of the parcel. The site
is relatively flat and grass covered. On the west side of the site is a local depression that contains
an apparent wetland/seasonal drainage swale.
In the existing conditions, most precipitation that falls onsite is either absorlled by vegetation or sheet
flows to the swale. The swale directs water north to an approximate 14" inside diameter corrugated
polyethylene pipe (CPEP) on the north property line.
II. OFFSITE ANALYSIS
Task 1: Study Area Definition and Maps:
See Section I (Project Overview) of this report for a detailed Study Area Definition. Attached are the
following maps:
Figure 1 Vicinity Map
Figure 2 Assessor's Map
Figure 3 USGS Quadrangle Topographic Map
Figure 4 Soils Map and Soils Information
Figure 5 Soils Information
Figures 6-10 King County Sensitive Areas Map Folios
Task 2: Resource Review:
The King County Sensitive Areas Map Folio for wetlands, streams and 100-year floodplams,
landslide hazard areas, erosion hazard areas, and seismic hazard areas were reviewed. According
to these maps this site does not contain any of these sensitive areas. Within the last 10 years there
were no relevant drainage complaints within the drainage path of the site per King County WLR
Local Drainage Services (LDS) Reports (Figures 11).
Task 3: Field Inspection:
During our field analysis (8/1/2007) the temperature was 70 degrees Fahrenheit and clear. The last
two weeks had been dry and warm with temperatures in the upper 70's to low 80's without
P.12005\25332\Engine,·rin~\Anulysis·Cxlcs\Docu1nents\Wor<.J\"['IR\25J32_LE.DOC
3
Level 1 Downstream Analysis
August 22, 2007
Jonah-Kai Hancock Short Plat
CE! #25332
significant rainfall. During this analysis the downstream drainage path was followed within V. mile
of the site.
A small upstream tributary area south of the site is composed of 2 sources. These include the
aforementioned swale and also a pasture/lawn area
The site slopes gradually to the north and west into a local depression containing a small
wetland/narrow swale. Much of the precipitation that falls on the 0.81-acre site is absorbed by
vegetation or sheet flows to the swale. In larger storm events, runoff would flow north in the swale
until reaching an inlet pipe on the north property line. We identified this point as the sole natural
discharge location for the site. This point is where our downstream analysis begins.
Task 4: Drainage System Description and Problem Descriptions:
The downstream drainage system is shown in Figure 12 (Downstream Drainage Map) and Figures
13a-13b (Offsite Analysis Drainage System Table). All field measurements are approximate and
have not been professionally surveyed.
Downstream Analysis:
Following storm events, runoff sheet flows west to the swale. This is where our downstream analysis
begins. (A-1) Runoff flows into a 14" CPEP inlet and is conveyed 10' to the north at 1 % into a type
1 cb (CB #1). CB #1 is in the backyard of a parcel located to the north of the site. (A-2) Stormwater
is then conveyed to the west 60' via a 14" CPEP sloped at 2% to another type 1 cb (CB #2).
(A-3) After leaving CB #2, stormwater flows 105' to the north in a 14" CPEP at 2% to a type 1 cb
(CB #3) located on the south side of SE 111 th St. (A-4) Following this, stormwater is conveyed to
the west 110' in a 14" CPEP along SE 111 th St. at 2% to a type 2 stormdrain manhole (SDMH #4).
(A-5) After leaving SDMH #4 stormwater is conveyed to the north 190' in a 14" CPEP through a
small park at 2% to another type 2 stormdrain manhole (SDMH #5) located beneath SE 110th PL.
(A-6) Stormwater is then conveyed 130' to the northeast in a 14" CPEP at 2% to another type 2
stormdrain manhole (SDMH #6). (A-7) Stormwater continues to the northeast for 20' in a 12" PVC
pipe and outlets into the southerly roadside ditch on SE Renton Issaquah Rd. (A-8) After entering
the roadside ditch, stormwater is conveyed to the east 295' at 5% within the ditch. The ditch is 8'
wide, 2' deep, 2: 1 side sloped, and rock and grass lined. (A-9) After leaving the ditch near the
intersection of SE Renton Issaquah Rd. and 148th Ave. SE, stormwater enters a 12" concrete pipe.
It is then conveyed to the north 50' at 2% beneath SE Renton Issaquah Rd., where it outlets on the
north side via a 12" ductile iron pipe onto a rip-rap splash pad. At some point beneath the road the
pipe type changes from concrete to ductile iron. (A-10) After leaving the splash pad, stormwater
sheet flows 465' to the northwest at 5% through a vegetation lined swale. This section is heavily
vegetated with blackberries and has 4: 1 side slopes. There was no evidence of scouring or erosion
and this path runs on the mutual property lines of tax parcels #0323059-070 and #0323059-120. (A-
11) Stormwater then enters a local low point in the drainage course for 110' at 0% as it enters a
newer development. There was no evidence of standing water or a control structure present, but this
local low point provides a "check dam" to slow down stormwater. (A-12) Stormwater is then
P.\2005\25332\Engmeen!1,!!\A.nalysis-Calcs\D,.>cum:n1.s\Won.J\TIR\25332_Lf DOC
4
Level 1 Downstream Analysis
August 22, 2007
Jonah-Kai Hancock Short Plat
CE! #25332
conveyed in a 24" CPEP for 30' at 2% to a type 2 stormdrain manhole (SDMH #7). (A-13) After
leaving SDMH #7, stormwater is conveyed for 165' at 10% within a 24" CPEP that outlets to a rip-
rap pad with debris barrier on the north side of NE 17th St. Stormwater continues in an open
drainage course more than 1A mile from the site.
Task 5: Mitigation:
During our downstream investigation, we did not observe any Severe Flooding problems (type 3),
Severe erosion problems (type 2) or Conveyance Nuisance problems (type 1 ). There were no
capacity-constraint issues observed and none have been reported in the past. Development of this
parcel should not significantly aggravate existing downstream drainage problems or create new
problems if the project is designed in accordance with the 1990 King County Surface Water Design
Manual. Proposed storm drainage facilities for this project will need to meet the applicable core
requirements.
Pc\2005\25332\E11ginceri11g\Ana!ysi~-Cak.s\l1ocumenrs\Wnrd\TlR\25332_LE DCC
5
Level l Downstream Analysis
August 22, 2007
APPENDIX A
Figures
P.\2005\25332\Engineenng\Analysis-Caks\Dxumenls\Word\TIR\2:'i332_LE.D0C
Jonah-Kai Hancock Short Plat
CE! #25332
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~i9. 'So.
IJESCIU PTl ONS OF 1111' SO!LS
soils are used f?r~~l~e~, ~~i~ This section descdbes the soil series and map-
ping units in the King County Arca. f:~ch so~l.
series is described an<l then each mapping unit 1n
that series. Unless it is specifically mentioned
otherwise, it is to be assumed thrit what is stated
about the soil series holds true for the mopping
units in that series. Thus, to get full information
about any one mapping unit, it .is ncccss ary to read
both the description of the mapping unit and the
description of the soil series to which it belongs.
An important part of the description of each
soil series is the soil profile, that is, the
sequence of layers from the surface downward to
rock or other underlying material. Each series
contains two descriptions of this profile. The
first is brief and in tenns familiar to the layman.
The second, detailed and in technical tenns, is for
scientists, engineers, and others who need to make
thorough and precise studies of soils. Unless it
is otherwise stated, the colors given in the
descriptions are those of a moist soil.
As mentioned in the section 1 1iow This Survey Was
Made," not all mapping units are members of a soil
series. Urban land, for example, does not belong
to a soil series, but nevertheless, is listed in
alphabetic order along with the soil series.
Following the name of each mapping unit is a
symbol in parentheses. This symbol identifies the
mapping llllit on the detailed soil map. Listed at
the end of each description of a mapping unit is the
capability unit and woodland group in which the
mapping unit has been placed. lhe woodland desig-
nation and the page for the description of each
capability unit can be found by referring to the
"Guide to Mapping Units" at the back of this survey.
The acreage and proportionate extent of each
mapping unit are shown in table 1. Many of the
tenns used in describing soils can be found in the
Glossary at the end of this survey, and more de~
tailed information about the tenninology and methods
of soil mapping can be obtained from the Soil Survey
Manual (19).
Alderwood Series
lhe Alderwood series is made up of moderately
well drained soils that have a weakly consolfdated
to strongly consolidated substratum at a depth of
24 to 40 inches. T1tese soils are on uplands. They
formed under conifers, in glacial deposits. Slopes
are Oto 70 percent. The annual precipitation is
35 to 60 inches, most of which .is rainfall, between
October and May. The mean annual air temperature is
about 50° F. The frost-free season is 150 to 200
days. Elevation ranges from 100 to 800 feet.
In a representative profile, the surface layer
and subsoil are very dark brown, dark-brown, and
grayish-brown gravelly sandy loam about 27 inches
thick, The substratum is grayish-brown, weakly
consolidated to strongly consolidated glacial till
that extends to a depth of 60 inches and more.
8
J\lderwood
berries, row
are the most
crops, an<l urhan development. They
extensive soils in the survey area.
Alderwood gravelly fj"?L loa'!'./-~t_~~
~lopes (Age) .--'rids so. 1.5 rofJ,ng. Areas arc
irregular in shape and range from 10 to about 600
acres in size.
Representative profile of Alderwood gravelly
sandy loam, 6 to 15 percent slopes, in woodland,
450 feet east and I ,300 feet south of the north
quarter corner of sec. 15 1 T. 24 N., R. 6 E.:
Al--0 to 2 inches, very dark brown (IOYR 2/2)
gravelly sandy loam, dark grayish brown
(lOYR 4/2) dry; weak, fine, granular struc-
ture; slightly hard, friable, nonsticky,
nonplastic; many roots; strongly acid;
abnJpt, wavy boundary. I to 3 inches thick.
82--2 to 12 inches, dark-brown (IOYR 4/3) gravelly
sandy loam, brown (IOYR 5/3) dry; moderate,
medium, subangular blocky structure; slightly
hard~ friable, nonsticky, nonplastic; many
roots; strongly acid; clear, wavy boundary.
9 to 14 inches thick.
83--12 to 27 inches, grayish-brown (2.5Y 5/2)
gravelly sandy loam, light gray (2.5Y 7/2)
dry; many, mediwn, distinct mottles of light
olive brown (2.5Y 5/6); hard, friable, non-
sticky, nonplastic; many roots; medium acid;
abrupt, wavy boundary. 12 to 23 inches thick.
IIC--27 to 60 inches, grayish-brown (2.5Y 5/2),
weakly to strongly consolidated till, light
gray (2.SY 7/2) dry; common, medium, distinct
mottles of light olive brown and yel-Jowish
brown (2 .SY 5/6 and lOYR 5/6); massive; no
roots; medium acid. Many feet thick.
The A horizon ranges from very dark brown to
dark brown. The B horizon is dark brown, grayish
brown, and dark yellowish brown. lhe 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 logging 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 the poorly drained Norma
Bellingham, Seattle, Tukwila, and Shalcar soils· '
some are up to 5 percent the very gravelly Ever;tt
and Neilton soils; and some are up to IS percent
Alderwood soils that have slopes more gentle or
steeper than 6 to 15 percent. Some areas in New-
castle Hills are 25 percent Beausite soils, some
no:theast of Duvall are as much as 25 percent Ovall
soils, and some in the vicinity of Dash Point are
10 percent Indianola and Kitsap soi ls. 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 subsoil and very sl0111 in the substrattun.
Roots penetrate easily to the consolidated substra-
tum 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,
and row crops, and for urban development. Capabili~y
unit IVe-2; woodland group 3dl.
Alderwood ravelly sandy loam, 0 to 6 ercent
~ (AgB) ,--is soil is nearly level an
undtiIS.ting. It is similar to Alderwood gravelly
sandy loam, 6 to 15 percent slopes, but in places
its surface layer is 2 to 3 inches thicker. Areas
are irregular in shape and range from 10 acres to
slightly more than 600 acres in size.
Some areas are as much as 15 percent included
Norma, Bellingham, Tukwila, and Shalcar soils, all
of which are poorly drained; and some areas in the
vicinity of Enumclaw are as much as 10 percent
Buckley soils.
Runoff is slow, and the erosion hazard is
slight.
This Alderwood soil is used for timber, pasture,
berries, and row crops, and for urban development.
Capability tmit IVe-2; woodland group 3d2.
Alderwood ravell sandy loam, 15 to 30 ercent
slofes AgD) .--Dept tote su stratum 1n tis soil
var1es within short distances, but is commonly
about 40 inches. Areas are elongated and range
from 7 to about 250 acres in size,
Soils included with this soil in mapping make
up no more than 30 percent of 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 of
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 mostly for timber.
Some areas on the lower parts of slopes are used
for pasture. Capability unit V!e-2; woodland-group
3dl.
A!derwood and Kitsa soils, ver stee (AkFJ.--
'111is mapp1ng unit is a out SO percent Al erwood
gravelly sandy loam and 25 percent Kitsap silt
loam. Slopes are 25 to 70 percent. Distribution
of the soils varies greatly within short distances.
About 15 percent of some mapped areas is an
included, unnamed, very deep, moderately coarse
textured soil; and about 10 percent of some areas
is a very deep, coarse-textured Indianola soil.
Drainage and permeability vary. Runoff is rapid
to very rapid, and the erosion hazard is severe to
very severe. The slippage p.otential is severe.
These soils are used for ·timber. Capability
unit Vile-I; woodland group 2dl.
JO
Arents, Alderwood
Arents 1 Alderwood material consists of Alderwood
soils that have been so d istu!'bed through urban-
ization that they no longer can be classified with
the Alderwood series. These soils, however, have
many similar features. The upper part of the soil,
to a depth of 20 to 40 inches, is brown to dark-
brown gravelly sandy loam. Below this is a grayish-
brown, consolidated and impervious substratum.
Slopes generally range from Oto 15 percent.
These soils are used for urban developm~nt.
ArentsJ Alderwood material, Oto 6 rcent sloes
(AmB .--In many areas t i.s soil is level, as a
result of shaping during construction for urban
facilities. Areas are rectangular in shape and
range from 5 acres to about 400 acres in size.
Representative profile of Arents, Alderwood
material, 0 to 6 percent slopes, in an urban area,
1,300 feet west and 350 feet south of the northeast
corner of sec. 23, T. 25 N.1 R. 5 E.:
0 to 26 inches, dark-brown (lOYR 4/3) gravelly
sandy loam, pale brown (lOYR 6/3) dry;
massive; slightly hard, very friable, non-
sticky, nonplastic; many roots; medium acid;
abn.ipt, smooth boundary. 23 to 29 inches
thick.
26 to 60 inches, grayish-brown (2.SY 5/2) weakly
consolidated to strongly consolidated glacial
till, light brownish gray (2.SY 6/2) dry;
co1J11J1on, medium, prominent mottles of yellowish
brown (lOYR 5/6) moistj massive; no roots;
medium acid. Many feet thick.
The upper, very friable part of the soil extends
to a depth of 20 to 40 inches and ranges from dark
grayish brown to dark yellowish brown.
Some areas are up to 30 percent included soils
that are similar to this soil material, but either
shallower or deeper over the compact substratum;
and some areas are 5 to 10 percent very gravelly
Everett soils and sandy Indianola soils.
~is Arents, Alderwood soil is moderately well
dra1n~d. Permeability in the upper, disturbed soil
material is moderately rapid to moderately slow
depending on_ its compaction during construction:
The substratum is very slowly permeable. Roots
penetrate to and tend to mat on the surface of the
consolidated substratum. Some roots enter the
substratum through cracks. Water moves on top of
~he substratum i~ winter. Available water capacity
1s low. Runoff 1s slow, and the erosion hazard is
slight.
lnis soil is used for urban development. Ca-
pability unit !Ve-2; woodland group 3d2.
Arents, Alderwood material, 6 to JS percent
slopes (Ame) .--1his soil has convex slopes. Areas
are re.ctangular in shape and range from JO acres to
about 450 acres in size.
1
,_ c::-:::_-:J
MILE + N
The boundaries of the sensitive areas dis-
played on these maps are approximate.
Addltlon<1I seflsltlve areas that t1ave not
been mapped may be present on a devel-
opment proposal site. WhP.re dilferences
occur between what Is IUustrated Ofl these
1naps and the site conditions, the actual pre·
sence or absence on the site of the sensitive
area as defined In ttie Sensitive Area
Ordinance. Is UJC legal control.
Numbered wetland~. PlfC~Pt those wlt11 an
"a" or "b" desl911atio11 are Included !n the
King Count,, O'rtla11d.~ Irw..:11lory. rile
locations of wetl;11H1S deslq11,1tcd ",1'' h,lvc
been vr.rfrlcd nn Pie 5il" Li' 11 varict\· of
sources. Wetland; ,1,~siqq,1t~,J "ti" ilte 111ap
Ped In the U.S. F ,~11 a111J Wi!!Jllte 5PrVICf"
fti~/;~~~en;~!~n~;';\, T~11 •(/i:/ 1: ;'.;~· I 1~;; _1 th,.; r 1ou1
There may he 9,1ps in \hp 1111<11bFJrlnq se-
quem::c within ir1divlrf" 11 <l>,1lll,1<r,i b;i5lns
Wet
.....
1/2
----~j t 0
MILE N
The boundaries of the sensitive areas dis-
played on these maps are approximate.
l\clditlonal sensitive areas tllat ti;ive nol
LJecn ,napped may be present on a dcve1-
oprne11t proposal site. Wt1etP rJilfc,c11ccs
or.cur hetwi:!en what is illustr;qed nn tJie,c
maps and the site conditions, 01c ,1rtual pr,:,.
sence or absence on the site of !!1,:, si::n~ltivP
area as defined in the si:-nsilive Area
01tlin,1nc'! -Is tt1e legal r::ontrol.
One-hundred-year floodplalns extend be-
yond those shown on maps. Flood ln-
sunmce Rate Maps do not always show the
floodPl11ln to the hf'ar:lwalers of streams.
ll!lllll 100-Year Roodplall'l9
Stre,
Year
'!
0 -· 1
::I
MILE t
N
-
f"he bot1ndatfcs of the sensitive areas djs.
1llayed on tl1ese maps are aPProxi111ate.
/\cJdiliona! ~ens!tlve <1reas tllilt l1;iv,: not
been marred may be Present on a deve1
t>p111ent prcros,11 site, Where diHe1e11ccs
o,_·ctn b~tween what Is ltlustr,1ted 011 tJ1c~8
maps ;ind the site conditions, the 1'l(ll!JI prr-
sence or absence on the site of Ila' scn1ltiv"
~rca a~ defin0d In the s,~11s/tivr' /\1e,1
! Jr<tinancJ> Is lbC' tegal control.
1-,1. ~
l:=-{"OS; Oh
'r:, c,
·, :j
f,.,1'
I :,n::,
1\n· ;,
1--0 --~:/
MILE
t
N
The boundaries of the sensitive areas dis-
Played on these maps are approximate.
/\dditional sensitive areas that 11avf! nol
bo:'!(!11 m,1pped n1.1y be present on a de11e1-
opmer1t nroposat site. Where differences
orcur betwt>en what Js Illustrated 011 those
maps and tlle site conditions, the ac-tuaf pre
s~ncE" ot abs1mce on the sltc of the sensitive
area -as d<>flnecr In the Sen~ilivr> Arc<1
Onlinttnce -Is 1h19 legar control.
Lands
Areas
1 1/2 0
lil
1
I
MILE
t
N
The boundaries of the sensitive areas dis-
played on these maps are apProxlmate,
Additional sensitive areas that have not
been mapped maY be present on a devel-
opn1ent proposal site. Where differences
occur between what Is Illustrated on these
111aps and the site conditions, the acluaf pre-
sence or absence on tf,e site of the se11s1tlvc
area as defined In tt1e St'n~itlve Are;,
Or<1i11.J11ce I~ the le9af control.
',h, ',-,,)
See weuands and !.1nclslicl1; l1az;11d' maps for
addiLlonil! polcnti,11 s1;i~111ic h<Vilrrl art'itS.
Wctlamis rir1d l,111(1Slicic ;uC'a,; ;ire s11sccptf1Jle
to failu1c duriri•J c,11\IJ't11al(r:,;. (Jthc1 sei~i11ic
ll.1Zil1tf tH!!,1S 11()! sl!'h'.'ol ri11 tlliS 111,1P ,11('
sl1oreli11es 1111dc1l,1111 t,y I,,, ,1~tri1w sr•di111r•11ts:
these arc susco:>plit.11" 1" 11'l"''!Jtl/(111
'"
Se
Ar
AUG. 2. 2UUI 2:04PM KING CO. WLRD N0.6031 p
r-.:~. \\ 0.
King County Water and Land Resources (WLR) Division CrQ4 "°'d <Z.. Coinp.
20 l S Jackson St, Suite 600
Seattle, WA 98104-3855
FAX
Date:
Number of pages including cover sheetd__
From: Cindy Torkelson
WLR Stonnwater Services Section
Phone: 206-296-1900
Fax Number: 206-296-0192
IMPORTANT LEVEL 1 ANALYSIS NOTE: We do not send copies of certain
complaint types that are not relevant such as BCW, FI, FIR, FIH and WQA, and
we do not send CL and LS types. See key below. Type SI, S2 and S3 will not be
faxed due to size constraints.
* IF YOU ARE USING THE 200S SWM DESIGN MANUAL YOU ONL YNEED IOYRS WORTII OF
COMPLAINTS
The following is a li&t of complaint types received by the Water and Land Resources Storm.water
Services Section. Complaint numbers begimring prior to 1990-XXXX have been archived and are no
longer in our possession. They can still be retrieved, if necessary, but will take additional time and may
not be beneficial to Your research due to their age, development which has occurred, etc. If YoU are
interested in reviewing the actual complaints, they can be pulled (time permitting) for your review.
Copies can be obtained for$ .15 per page, and $2.00 per page for plans.
Keys;
J'Ipe of Investigation
C Action Request
BCW )l05inos.,• (or a ... w-
CCF Response ,o Jnquhy
.. CL Claim
EH En1brtement on Hold
ER lloftm:omcot l\oview
FCC,FC~ Focility Co~lain<s
fl SWM Fee Inquiry
FIR SWM Fee Review
FlH SWM Fee on Hold
•r.s
RR
NOA
WQC
WQ!;
WQR
WQA
WQO
S!,S2.sNJ
Lawsuir
FactlityEn~ ~ew
Noighborhood Drain>gc Assist.nee
Wa«r Quality Complaint
Water Quality Enfb1teme.nt
Wattt Quality Engineering RevwN
Water Quality Audit
W,ter Quality-Olhor
En.gineeriug Srudies
DP<! ,r Problem
DCA
DDM
DES
DL1i
PTA
INQ
MMA
MM!'
MMG
MMM
MNM
MNW
SWP
WQB
WQD
WQI
REM
ORT
NWD
Devolo\mtentlConsttuction
Drainage • Miscellaneous
Dran,age -&osion/S..iimenlatlon
Ilnrin>s•-Landolide/Barth Movcmcnt
Dnlinage Toolmioal Asslslance
Drainage-Oeneral lrtqui,y
MamtellaDCO -Aesthetic,
MQmtCQ811.ce -Flooding
Mamtcoaru:< -General
Mointenanct • Mowing
Main-... -Needs Maintenance
Maintenance-Noxious Weeds
SWM Fee Questions:
Wator Quality-Best Managem<'1t Practices
Wot<, Quality-Dumping
Water Quality -ffiicit Connecriort
SWMFee-Re,:neasuremont
SWM Fee-Gn>nt
SWM Fc:c-Ncw Discount
*Subject to Public Di.sc:losun:. n:quircmc:nta 1. R.eocipt of written~ for documents 2. Review and' approval by Prosecuting Attorney's office
AUG. 2 2007 2 04PM KING CO. WLRD NO. 6031 p 2
Fi 3. ll b
Orc.ih~<.!. Grnp~llb
King County Water IOI Laud Resnurces Division -Drainage services Section
CUllll)laint Searcll Pnn1ed : 08/02/2007 11 :?.7:50 AM
CllllllllalDt : Tnl Gt Pl'llllam A-.n of Problem Commeuts Tbl'osPaga ,_er
1975-0004 C DRNG 958 S UNSET BL SE 138TH/SUNSET BUANNEXED 626J6
1985--0046 C DRNG 11203 14eTHAVESE PONDING 626J6
1964-0015 C FLDG RENTON-JSSA HWY MAY CREEK 62BJ6
1986-0654 C FILLING 11203 148THAVE SE 626J6
1968-0790 C DRNG 14418 SE 116TH ST INADEQUATE SYSTEM INSTALLED 626J6
1989-0140 C EROSION 14429 SE 116TH ST PVT RD WASHOUT DUE TO NO DRAINAGE 626J6
1989-0150 C DRNG/ERO 14428 SE 11eTHST PVT RD WASHOUT DUE TO NO DRNG 89-0 626J6
1989-0318 E DRNG 11800 138THAVE SE CLEARINGOF RID NATURAL RID POND 626J6
1990-1623 C FLOG 13611 SE 116TH ST @R/0 FACILITY SEEPING WATER 626J6
1991-0339 C FLDG 11212 137THAVE SE PIPE OF PRNATE DITCH 626"6
1991-0578 C DRNG 11833 142NDAVE SE WATER PONDING IN YARD 626J6
1992-0100 C DRAINAGE 12240 142NDAVE SE 626J6
1996-0143 C RUNOFF 14614 SE RENTON-JSSAQUAH RD RUNOFF FROM SR 900 626J6
1996-0552 C FLOG 11615 148THAVE SE 628J6
1996-0562 R FLOG 11615 148THAVE SE FLOODING FROM VANDALIZED FIRE HYDR 626J6 c 2000-01eo WQR WQB 11204 148TH AVENUE SE Mrs. Wa~ has muklhed al exposed soi lo st 626J6
2003--0210 X INQ 10415 147THAVESE EMAL INQUIRY REGARDING EROSION CO 626J6
2003--0567 C DTA 11327 146THAVESE WATER IN CRAWL SPACE. APPEARS TOG 626J6
2004--0624 WQR WOB 148THA@ SE RENTON ISSAQUAH 626J6
200$-0596 SUP UTI 14BTHA & SE RENTON ISSAQUAH S-236-05 UTILITY INSTALLATION 626J6
2006-0596 SUPF I.Jrl 14BTHA & SE RENTON ISSAQUAH S-236-05 UTILITY INSTALLATION 626J6
2005-0674 C RFN 11323 148THAVE SE Work by neighbor has flooded field. Inv informe 626J6
2007-0029 C DES 14702 SE 105TH ST Changes to Wlndstone dev oauslrlg floodlrig & 626J5
2007-0223 FCR MNM 10731 148THAVE SE Const material stored lri D91403 pond tract R 626J6
Page 1 of 1
_,
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OFFSITE D . "·
FOR JONAH-~AINAGE MAP
SEC. 03, T. 2t~ HANCOCK
---~ -~--
Basin: May Creek Basin
Symbol
11
See mop
A-I
A-2
A-3
A-4
A-5
A-6 I
A-7 I
A-8 I
Drainage
Component
Type;
Nameand
Size
Type: sheet flow,
swale, stream,
channel;: pipe,
·pond; Size:
diameter,:sUrface
.-area
Pipe
Pipe
Pipe
Pipe
Pipe
Pipe
Pipe
Ditch
OFFSITE ANALYSIS DRAINAGE SYSTEM TABLE
Surface Water Design Manual, Core Requirement #2
''·nmn~g~'eo1npt5i\en1
· msciipti<m
Drainag.ebasins, vegetalian, cover~_: .. dtjlth;
' _,' '"" ' -~:e pf.Scri~i~Ve:areafV0_1~,m,e
14" Inside Diameter CPEP
14" Inside Diameter CPEP
14" Inside Diameter CPEP
14" Inside Diameter CPEP
14" Inside Diameter CPEP
14" Inside Diameter CPEP
12" Diameter PVC
Rock and grass lined, 2: I side
sloped, 8' wide, 2' deep
Slope ..
. (approx.) \
%
1%
2%
2%
2%
2%
2%
2%
I 5% I
Distance
ffon1 Site ••
DiscMr<>e ,, , ..... _,)':."";Ci; .>
0-10'
10-70'
70-175'
175-285'
285-475'
475-605'
605-625'
625-920'
None
None
None
None
None
I None
I None
I None
None
None
None
None
None
None
None
None
Obsep,~tions offield inspector
\--Re~l.iutce:revlewecor resident
likelihood:ofprobtem, overflow
potential impacts
Stormwater leaves the site and enters a
type 1 catch basin #1 North of the site.
Stormwater is conveyed to the West
from CB #1 to another type I catch
basin #2
Stormwater is conveyed to the North
from CB #2 to a type 1 catch basin #3
with a solid lid
Stormwater is conveyed to the West
from CB #3 to a type 2 storm drain
manhole #4 with a solid lid
Stormwater is conveyed to the North
beneath a small park from SDMH #4 to
another type 2 storm drain manhole #5
with a solid lid
Stormwater is conveyed to the Northeast
from SDMH #5 to another type 2 storm
drain manhole #6 with a solid lid
*lid locked, unable to open
Stormwater is conveyed to the Northeast
from SDMH #6 to the Southerly ditch
on SE Renton Issaquah Rd
Southerly roadside ditch on SE Renton
Issaquah Rd
Tl
,1 c,.
\J,.J
.)>
---
Basin: May Creek Basin
Symbol Draiiiage
Component
Type,
Name and
Size
See map l Type: sheet flow,
sWale, su-eam,
channel. pipe,
·pClnd~ Size:
A-9
diarileter, :Surface
area
Pipe
A-10 Loosely I
I defined swale
A-11 I Pond/ low I point
A-12 Pipe
A-13 Pipe
'1''!'lrainage'Compi;fnei/t
-Descripyq~·. -
• ',1· :::,,,,+,:,
Drai~g~ .basins; ,v~~;ttj_qii; ·c~yet~~clqnh; type of sens·i,~VK llrefa~-vc,1i'titi(.
12" Cone at inlet,
, 12" DI at outlet
Heavily vegetated with black
berries, 4:1 side slopes
A low point as the drainage course
enters a development
24" CPEP
24" CPEP
I
I
.,, Slope
(appfox.)
,;";.,,, . ";
:;,;i1Yt ..
·>;;';;f,-j;
,%
2%
5%
0%
2%
10%
920-970'
970-1,435'
1,435-1,545'
1,545-1,575'
1,575-1,740'
None None
None None
None None
None None
None None
, Obser;vatio,ns, ?(field inspector · · >~~-0.ll'esOurce fevieWer-:br resident
"'<.:J)'· ',.c'
Stormwater is conveyed to the
Northwest under SE Renton Issaquah
Rd, the pipe changes from concrete to
ductile iron at some unknown point,
there is a rip-rap pad at the outlet
Natural drainage course. no evidence of
scouring
No control structure found, no standing
water, provides a nice "check dam" for
moving water
Stormwater is conveyed to a type 2
storm drain manhole #7
Stormwater is conveyed from SDMH #7
to an outfall with trash guard and rip-rap
ad
1-----+---+------f----+---+------+-----+---------Jlil -·
w
0 ..
TIR / Level 1 Downstream Analysis
Januar 2009
APPENDIXB
Silver King Short Plat
CE! Job No. 25332
TIR WORKSHEET AND
STORM DRAINAGE CALCULATIONS
Page 1 ol 2
(o"¥'Li rt,o 1/ /~/2""'1
King County Building and Land Development Division
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
PART 1 PROJECT OWNER AND .
· PROJECT ENGINEER .
Project Owner i.,J4)l·IL-'1, ll ~"''''-"
Addressj1oi $ l~~il' flvt•J• 5C l2l11n•,, 1,/A qg <.>_l;i
Phone (7ob) lV-1· 4\,13
PART 2 PROJECT LOCATION
AND DESCRIPTION
Project Name ~ilV//1. 1.:1,.1(;. s,,,.,, f'l-'lr
Location
Township ·i;, :'\I ,,,:w
Range S t11ST
Section _·z.} ____ _ Project Engineer /11~~1( a IGd-f.i.
Company Vll/l[I r-trlbi-vlln.,.,-1, 1,/L.
Address Phone .. ~!;" e,,,,.,.JtlZ f>t\/0. t'I t<:&A..1"'111
0-2 7 (/.ti· -t'5"S°
Project Size (2.'iP /\{ -Zl'I AC ___ _
Upstream Drainage Basin Size +/. \-l ~l11;}AC __
PART 3 TYPE OF PERMIT APPLICATION PART 4 OTHER PERMITS
D Subdivision D OOF/GHPA D Shoreline Management
dz( Short Subdivision D COE404 D Rockery
D Grading D DOE Dam Safety D Structural Vaults
D Commercial D FEMA Floodplain D Other
D Other D COE Wetlands CMHPA
PART 5 SITE COMMUNITY AND DRAINAGE BASIN
Community .
l.)'T'1 0 f ,z. ''"' 1" ,v
Drainage Basin
PART 6 SITE CHARACTERISTICS
D River ____________ _
D Stream------------
0 Critical Stream Reach
@ Depressions/Swales
D Lake _____________ _
D Steep Slopes
D Lakeside/Erosion Hazard
PART7 SOILS
D Floodplain --------------
ozf Wetlands Z S M11 Lt. Qt\/c)
D Seeps/Springs
D HighGroundwaterTable
D Groundwater Recharge
D Other
SoilType
A c.. 3 6 .. Slopes 7. Erosion Potential Erosive Velocilies
+, i5 · I.,:, w __L/V,U.f2-~ -----
0 Additional Sheets Attatched
1/90
Page 2 of 2
King County Bufldlng and Land Development Division
TECHNICAL INFORMATION REPORT (TIA) WORKSHEET
PART 8 DEVELOPMENT LIMITATIONS
REFERENCE LIMITATION/SITE CONSTRAINT
~
D
D
D
D
.Ch. 4 • Downstream Analysis
\i)'tJlAr,O {1,(.('otZ:T
D Additional Sheets Attatched
PART 9 ESC REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
D Sedimentation Facilities
~ Slabilized Construction Entrance
[JY, Perimeter Runoff Control 9£. Clearing and Grading Restrictions
L':f, Cover Practices
cg"' Construction Sequence
D Other
PART 10 SURFACE WATER SYSTEM
{2,vffl.tZ
MINIMUM ESC REQUIREMENTS
FOLLOWING CONSTRUCTION
CT6 Stabilize Exposed Surface fil Remove and Restore Temporary ESC Facilities
IB Clean and Remove All Silt and Debris ~ Ensure Operation of Permanent Facilities
~ Flag Limits of NGPES
D Other
D Grass lined Channel D Tank D Infiltration C0 Pipe System D Vault D Depression
Method of Analysis
S0vil
D Open Channel D Energy Dissapator GZf Flow Dispersal
D Dry Pond D Wetland D Waiver
Compensation/Mitigation
of Eliminated Site Slorage
!V/f; D Wet Pond D Stream D Regional Detention
BriefDescription of System Operalion CA1~ \t 91)SI 'II~ (oi.U:<,T s.va.F,,c£
Viii" [,,,J1;•19..,cf f1P[ 'Th 1}1£ O;Sf'l'IZ)lr, TIZt'"JC/1.
Facility Related Site limitations
Reference Facility limitation D Additional Sheets Allatched
------------------
PART 11 STRUCTURAL ANALYSIS
(May require special structural review)
D Cast in Place Vault D Other
D Retaining Wall
D Rockery> 4' High
D Structural on Steep Slope
I or a civil engineer under my supervision have visited the site. Actual
site conditions as observed were Incorporated into this worksheet and the
attatchments. To the best or my knowledge the Information provided
here is accurate.
'-----·---.
PART 12 EASEMENTS/TRACTS
D Drainage Easement
D~ccess Easement
u2'f Native Growlh Protection Easement
D Tract
D Other
lf,10
\
! " I ·. . / i 0,i . ., ·-·.
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-A-fLtl', i-o (3£ OL11t.1or1,.o:: [..o1 Ii. i..aT 8
g ,~as;:: c; )10 s,
t .v 1.1) '
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"~'>? NIA>< i "'1(/1,it\i·,.;:;
A i!'!.4:t¥"" (o S'3) (::J 1.17.)-: o -1_3 A:.~_1,(
A(}. l A p tt'· :: l". ,n) (". i. , ) -; o. 1.? At!?,~
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f&7N! <;',,If.It' i? (\JLl)l,,(f
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T:. t'f> / 6,; z .7 ~)
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(7,v,:,1,iJ''llt <; •Nlt: (.:;,Ne,11/"4/i
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,,,;;,,r"' C l1 I\ ,1 (. ( 11,\v l r
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( /\r;y:"1 Aptn" 7b
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K I N G C O U N T Y, W A S H I N G T O N, S U R F A C E W A T E R D E S I G N M A N U A L ·------··---·--
/
..... ~-~ ~er,
·---------
100-YEAR 24-HOUR PRECIPITATION /
.,.. 3.4-ISOPLUVIALS OF 100-YEAR 24-HOUR .J
TOTAL PRECIPITATION IN INCHES
---------------------------·----
0 1 2 3 4 5 6 7 a MIies
1: 300,000 3.5.1-13
1/90
J
I
'"'
. '-
-
K I N G C O U N T Y, W A S H I N G T O N, S U R F A C E W A T E R D E S I G N M A N U A L
I
i
i
FIGURE 3.5.lC 2-YEAR 24-HOUR ISOPLUVIALS
':
\
1.~----'
lf---...---
lfl.·---:t"i:J:f:i(#
11
l(I 1s,
/
/
/
/
//j--
/ ;J
/ !
2-YEAR 24-HOUR PRECIPITATION
I'
.-3.4-ISOPLUVIALS OF 2-YEAR 24·HOUR
TOTAL PRECIPITATION IN INCHES
-------~--~
0 l 2 3 4 5 6 7 8 MIies
1: 300,000
--7"1:::---~---h-1/J ' \ -o--
j
.
'
-""' I L .
3.5.1-8 1/90
KING c OUN TY, WASHINGTON, SURFACE WATER DES I G N MANUAL
(2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20
CN points). However, high CN areas should not be combined with low CN areas (unless the
low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be
gonerated and summed to form one hydrograph.
FIGURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN KING COUNTY
HYDROLOGIC HYDROLOGIC
SOIL GROUP GROUP• SOIL GROUP GROUP•
Alderwood C Orcas Peat D
Arents, Alderwood Material C Oridia D
Arents, Everett Material B Oval C
Beausite C PIich k C
Bellingham D Puget D
Briscot D Puyallup 8
Buckley D Ragnar 8
Coaslal Beaches Variable Renton D
Earlmont Sill Loam D Riverwash Variable
Edgewick C Sala! C
Everett A/8 'Sammamish D
Indianola <P Seattle D
Kilsap Shacar D
Klaus SI Silt C
Mixed Alluvial Land Variable Snohomish D
Neilton A Sultan C
Newberg 8 Tukwila D
Nooksack C Urban Variable
Normal Sandy Loam D Woodinville D
HYDROLOGIC SOIL GROUP CLASSIFICATIONS
A. (Low runoff potential). Soils having high lnfillratlon rates, even when thoroughly wetted, and consisting
B.
C.
D.
•
chiefly of deep, well-to-<axcessively drained sands or gravels. These soils have a high rate of water
transmission.
(Moderately low runoff potential). Soils having moderate Infiltration rales when thoroughly wetted, and
consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of
water transmission.
(Moderately high runoff potential). Salls having slow Infiltration rates when thoroughly wetted, and
consisling chiefly of soils with a layer that impedes downward movement of water, or solls with moderalely
fine to rine textures. These soils have a slow rate of water transmission.
(High runoff potential). Soils having very slow infiltration rales when thoroughly wetted and consisting
chiefly of clay soils with a high swelling potential, soils with a permanent high water table, sells with a
hardpan or clay layer at or near the surface, and shallow soils over nearly Impervious material. These soils
have a very srow rate of water transmissfon .
From SCS, TA-55, Second Edition, June 1986, Exhibit A-1. Revisions made from SCS, Soll Interpretation
Record, Form #5, September 1988.
3.5.2-2 11192
KING COUNTY, WASHINGTON, SURFACE WATER DES I G N MANUAL
TA nu: J.5.2Il scs WESTERN WASHINGTON RUNOFF CURVE NUMBERS
SCS WESTERN WASHINGTON RUNOFF CURVE NUMBERS (Published by SCS In 1982)
Runott curve numbers for selected agricultural, suburban and urban land use for Type 1A
rainfall distribution. 24-hour storm duration.
CURVE NUMBERS BY
HYDROLOGIC SOIL GROUP
LAND USE DESCRIPTION A B C D
Cultivated land(l): winter condition 86 91 94 95
Mountain open areas: low growing brush and grasslands 74 82 89 92
I
Meadow or pasture: ' 65 78 85 89
Wooo or forest land: undisturbed or older second growth 42 64 76 81
Wooo or forest land: young second growth or brush 55 72 81 86
Orchard: with cover crop 81 88 92 94
Open spaces, lawns, parks. golf courses, cemeteries,
landscaping.
9000 condition: grass cover on 75%
or more of the area '113 80 86 90 fair condition: grass cover on 50%
® to 75% of the area 77 85 92
Gravel roads and parking lots 76 85 89 91 Dirt roads and parking lots 72 82 87 89
Impervious surfaces, pavement, roofs, etc. 98 98 ~ 98 Open water booies: lakes, wetlands, ponds, etc. 100 100 100 100
Single FamHy Residential (2)
Dwelling Unit/Gross Acre % Impervious (3)
1.0 DU/GA 15 Separate curve number 1.5 DU/GA 20 shall be selected 2.0 DU/GA 25 for pervious and 25 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
Planned unit developments. % Impervious
condominiums, apartments, must be computed
commercial business and
Industrial areas.
(1)
(2)
(3)
For a more detailed description of agricultural land use curve numbers refer to Nauonal Engineering
Handbook, Section 4, Hydrology, Chapter 9, August 1972.
Assumes roof and driveway runott is directed into street/storm system.
The remaining pervious areas (lawn) are considered to be in gooo condition for these curve numbers.
3.5.2-3
.
11192
K I N G C O U N T Y, WA S H I N G T O N, S U R FA C E WA T E R D E S I G N MA N U A L
TABLE 3.5.2C "n" AND "k" VALUES USED IN TIME CALCULATIONS FOR HYDROGRAPHS
"11 1 • Sheol flow Equa11on Manning's Values (For the inltla! 300 h ol travol)
Smoolh surfaces (concrelo, asphall, grl!llvel, or bare hard packod soil)
Fanow fields or loose sou surface (no residue)
CuUlvalod.1soll with residue cover ( s < m 0.20 fl/fl)
Cullivated son with residue cover (S> 0.20 fl/fl)
Short prairie grass and lawns
Dense grasses
Bermuda grass
Range (natural)
Woods or forest with fight underbrush
Woods or forest with dense underbrush
•Manning values for shffl flow only, from Overton and Meadows 1976 (See TA-55, 1986}
"I< Values Used In Travel Tlme{Tlma of Concentration calculations
Shaffow Coocenlrated Row (After the Initial 300 11.. ol sheet Row, R • 0.1)
1. Fores! Wfth heavy ground ltt:e, and meadows (n•0.10)
2. Brushy ground with some trees (n -0.060)
3. Fallow or minimum IHlage culllvallon (n .. o.040)
4. High grass (n .. 0.035)
5. Short grass, pasture and lawns (n=0.030)
6. Nearly bare ground (n,.,0.025)
7. Paved and gravel areas (n•0.012)
Chanuol Flow (Intermittent) (At 1he beginning of vlslbkt ctvlnnels: A•0.2)
1.
2
Foresled swale with heavy ground liner (n = 0.10)
'
4.
Fmeslod drainage course/rl'lvlne wllh defined channel bed (n. 0.050)
Rock-lined waterway (n=0.035)
5
6.
7.
8.
Grassed walerway (n .. 0.030)
~arth-llned watflfWay (n • 0.025)
CMP pipe (n=0.024)
Concrete pipe (O.O 12)
01her waterways and pipes
Channel Flow (Conllnuous stream, A -0.4)
9. Meandering stream with some ,x>ols (n .. 0.040)
10. Rock-llned stream (n•0.035)
11. Grass-tined stream (n=0.000)
12. Other Slreams, man-made channels and pipe
u5ee Chapter 5, Table 5.3.6C for addhlonal Mannings ·n· values for open channels
3.5.2-7
0.011
0.05
0.06
0.17
0.15
0.2-4
OA1
0.13
0.40
0.BO
k,
3
5
8
9
11
13
27
k,
5
10
"
17
20
21
"
0.508/n
k,
20
23
27
0.907/n ..
1,90
·---
TIR / Level I Downstream Analysis
Januar 2009
APPENDIXC
Silver King Short Plat
CEI Job No. 25332
MAINTENANCE AND OPERATIONS MANUAL
K I N G c o u N T Y, WA S H I N G T O N, S U R FA C E W A T E R D E S I G N M A N U A L
NO. 5 -CATCH BASINS
Maintenance
Component
General
Defect
Trash & Debris
(Includes
Sediment)
Structural Damage
to Frame and/or
Top Slab
Cracks In Basin
Walls/Bottom
Settlement/
Mlsallgnment
Are Hazard
Vegetation
Pollution
Conditions When M•lntenance
la Needed
Trash or debris of moro than 1/2 cubic
loot which Is located Immediately In front
of the catch basin opening or Is blocking
capacity of basin by more than 10%.
Trash or debris Qn the basin) that
exceeds 1 /3 the depth from the bottom
of basin to Invert of the lowest pipe Into
or out of the basin.
Trash or debris In any Inlet or outlet pipe
blocking more than 1/3 of tts height.
Dead animals or vegetation that oould
generate odors that would cause
complaints or dangerous ga~(e.g.,
methane).
Deposits of garbage exceeding 1 cubic
foot in volume.
Corner of frame extends more than 3/4
Inch past curb laoa Into the street QI
applicable).
Top Blab has holes larger than 2 square
Inches or cracks wider than 1 /4 Inch
Qntent Is to make sure all material Is
running Into the basin).
Frame not sitting flush on top slab, I.e.,
separation of more than 3/4 Inch of the
frame from the top slab.
C,acks wider than 1 /2 Inch and longer
than 3 feet, any evidence of soil particles
entering catch basin through cracks, or
maintenance person judges that structure
Is unsound.
Cracks wkfer than 1 /2 Inch and longer
than 1 loot at the joint of any Inlet/outlet
pipe or any evidence of so/I particles
entering catch basin through cracks.
Basin has settled more than 1 Inch or has
rotated more than 2 Inches out of
alignment.
Presence of chemicals such as natural
gaa, olf, and gasoline.
Vegetation growing across and blocking
more than 10% of the basln opening.
Vegetation growing In Inlet/outlet pipe
Joints that Is more than Blx Inches tall and
less than six Inches apart.
Nonflammable chemlcals of more than
1 /2 cubic loot per three feet of basin
length.
A-5
Results Expected
When Maintenance la Performed
No trash or debris located Immediately In
front of catch basin opening.
No trash or debris In the catch basin.
Inlet and outlet pipes free of trash or
debris.
No dead animals or vegetation present
within the catch basin.
No oondltlon present which would attract
or support the breeding of Insects or
rodents.
Frame Is even with curb.
Top slab Is free of holes and cracks.
Frame Is sitting flush on top slab.
Basin replaced or repaired to design
standards.
No cracks more than 1 /4 Inch wide at the
joint of Inlet/outlet pipe.
Basin replaced or repaired to design
standards.
No flammable chemicals present.
No vegetation bloclclng opening to basin.
No vegetation or root growth present.
No pollution present other than surface
film.
1/90
K I N G C O U N T Y, W A S H I N G T O N, S U R FA C E WA T E R D E S I G N M A N U A L
NO. 5 -CATCH BASINS (Continued)
Maintenance Condition• When Maintenance
Component Defect laN-ed
Catch Basin Cover Cover Not In Piece Cover I• missing or only partially In plaoa.
"'1y open catch basin requires
maintenance.
Locking Mechanism cannot be opened by one
Mechanism Not maintenance parson wtth proper tools.
Working Botta Into frame have leaa than 1 /2 Inch
of thread.
Cover Dffflcult to One maintenance peraon oannot remove
Remove lid altar applying eo lbs. ol 1111; Intent la
keep cover from aeallng off access to
malntanance.
Ladder Ladder Rungs Ladder Is unsafe due to mlsalng rungs,
Unsafe mlsallgnment, rust, cracks, or sharp
edges. " Metal Gratea Grate with opening wider than 7 /8 Inch.
(,I applicable)
Trash and Debris Trash and debrfs that Is blocking more
than 20% of grate surfaoa.
Damaged or Grate missing or broken member(s) of
Mlsalng the grate.
A-6
Reaulta Expected
When Maintenance la Performed
Catch basin oover Is closed.
Mechanism opens with proper tools.
Cover can b9 removed by on•
maintenance person.
Ladder mHls design standards and
allows malntenanoa person sale aocess.
Grate openings meet design slandards.
Grate free of trash and debris.
Grate Is In plaoa and meets design
standards.
If')()
K I N G C O U N T Y, WA S H I N G T O N, S U R FA C E WA TE R D E S I G N M A N U A L
NO. 6 -DEBRIS BARRIERS (e.g. Trash Racks)
Maintenance
Component
General
Metal
Delecl
Trash and Debris
Damaged/ Mlsslng
Bars
Condition• When Maintenance
la Needed
Trash or debris thal Is plugging more
than 20% of the openings In the barrier.
Bars are bent out or shape more than 3
Inches.
Bars are missing or entire barrier Is
mlBSlng.
Bars are loose and rust Is caualng 50%
deterioration to any part of barrier.
A-7
Reoull1 Expected
When Maintenance la Performed
Barrier clear to receive capacity flow.
Bars In place with no bends more than
3/4 Inch.
Bars In place aocordlng to design.
Repair or replace barrier to design
standards.
1/90
K I N G C O U N T Y, WA S H I N G T O N, S U R FA C E WA T E R D E S I G N MA N U A L
NO. 10 • CONVEYANCE SYSTEMS (Pipes & Ditches) -Maintenance Condition• When Maintenance Result, Expected
Component Defect la Needed When Maintenance la Performed
Pipes Sediment & Debris Accumulated sediment that exceeds 20% Pipe cleaned of all sadlment and debris.
of the diameter of the pipe.
Vegetation Vegetation that reduces free movement of All vegetation removed so water flows.
water through pipes. freely through pipes.
Damaged Protective coating Is damagedi rust Is Pipe repaired or replaced.
causing more than 50% deterioration to
any part of pipe.
My dent that deoreases the croas section Pipe repaired or replaced.
area of pipe by more than 20%.
Open Ditches Trash & Debris Trash and debris exceeds 1 cubic foot Trash and debris cleared from ditches.
per 1,000 square feet of dik:\. and slopes.
Sediment Accumulated sediment that exceeds 20% Ditch cleaned/flushed of all sediment and
of the design depth. debris so that It matches design.
Vegetation Vegetatton that reduces f,ee movement of Water flows freely through ditches.
water th,ough ditches.
Erosion Damage to See "Ponds" Standord No. 1 See 'Pends' Standard No. 1 Slopes
Rock Lining Out of Maintenance person can see native soll Replace rocks to design standard. Place or Missing (W beneath the rock lining.
Appllceble)
Catc:h Baalns See 'Gatch Basins' Standord No. 5 See 'Gatch Basins' Standord No. 5
Debris Barrle,s See 'Debris Barriers" Standard No. 6 See ·Debris Barriers" Standard No. 6 (e.g., Trash Rack)
A-11 1,')0
' '
CONCEPT ENGINEERING, INC
~ 455 Rainier Boulevard North ~:
-Issaquah, Washmgton 98021 I
.. (425) 392-8055 Fax: (425) 392-0108 J
A. SITEMAP
Standard Stream Study
For The
Silver King Short Plat
Located At:
11025 148"' Avenue SE
Renton, WA 98059
Tax Parcel Number:
032305-9020
Report Prepared For:
Jonah-Kai Hancock
10025 148th Avenue SE
Renton, WA 98059
(206) 234-9673
Report Dated:
January 19, 2009
Concept Engineering, Inc.
Job Nnmber:
25332
Prepared By:
/7#&;
Mark: Rigos, P.E,
Certified Wetland Biologist
Attached to this Standard Stream Study is a Site Map that shows the following information:
1. The entire parcel ofland owned by the applicant, including 100 feet downstream, is shown,
Upstream, the drainage channel resembles a narrow swale or small ditch. Downstream, the
drainage channel is a piped conveyance system.
11. The stream's onsite OHWMs were flagged in 2007 by a wetland biologist, Chris Holcomb, I
have reviewed and approved the flag locations.
111, The stream classification has already been performed and is described in our 8/29/2007-Wetland
Delineation Report and our 1/2009-Supplemental Stream Study, The drainage channel is a class
5 stream. It could be best described as a drainage ditch that conveys seasonal runoff
1v. Topographic contours are shown on the Site Map.
v. 100-year floodplain and floodway boundaries are not applicable for such a small drainage
channel.
CIVll ENC:i!NEERING / SURVEYINC / LJ\ND USE f'LANNII\C
P ·\2006\253 32\l:ng.1 nccring\,\ n:1lys1 s-Calcs\J )ut: un icnts\\Vord\253 32. Supp St1 t:arn S lud y .doc
VJ. The drainage pattern across the site 1s straightforward. The stream flows north. Arrows arc
provided.
vn. The stream is only I -2 feet wide and 6 inches -1 foot deep, so a cross-section was not provided
on the Site Map. A top view (plan view) of the stream is shown.
v111. The site's vegetated cover is shown on the Site Map. Vegetation includes approx. 10 significant
trees, several small alder groves, a couple lawns, and un-manicured pasture grasses and weeds.
1x. The Conceptual Wetland Mitigation Plan, attached to the preliminary short plat application
submittal package, shows proposed lots, existing improvements (to be removed), proposed
utilities, etc.
x. The Site Map shows existing and proposed ingress and egress from the east. Photos of the stream
are attached to this study.
B. GRADING PLAN
A grading plan is not provided, as I believe a grading plan is unnecessary, because the existing grade will
not be permanently modified near the stream. The only grades that will be impacted by the short plat are
near the east property line and the center of the site, where an alley tract is proposed. The alley results in
only 1-2 feet of cut or fill. The grading plan design was waived at the "dry-run" preliminary short plat
application submittal at Renton City Hall.
C. STREAM ASSESSMENT NARRATIVE
1. The drainage channel's classification is a class 5 stream.
11. The vegetated cover of the site is partly to mostly cleared. Several large trees remain on the site's
east side. The site's west side contains weeds, pasture grasses, and low groundcover. The central
portion of the site contains a manicured lawn up to the drainage channel's east side. There is no
existing flood hazard area. Homes will not be built near the stream, so there is no relevant or
increased flood hazard.
111. The stream's ecological functions are minimal. From a water quality standpoint, its functions are
low. The stream is surrounded by weeds and pasture grasses. It generally lacks mature
vegetation such as shrubs and trees. From a habitat standpoint, its functions are also low, as
homes and outbuilding structures are directly north and south of the stream. From a hydrologic
standpoint, its functions are also low, as the drainage channel flows into a detention pond just
downstream of the site before release into a stream.
1v. The class 5 stream is located in the west-central portion of the site. Seasonal storrnwater runoff
flows south to north in this channel. Onsite, the channel's dimensions are approximately 1 -2
feet wide by 118 feet long x by 6 inches -1 foot deep. The channel's upstream tributary area is
very small, at approx. 1 -2 acres. It does not have a large enough tributary area to create a
floodplain. We did not observe any fish or fish habitat. Clearly, the channel's narrow width, low
flows, and non-perennial flows prevent any fish or fish habitat. The downstream portion of the
stream begins a 500-foot long journey through 15-inch diameter drainage pipe that also inhibits
fish or fish habitat. There is some wildlife in the area, since the site is close to the Growth
Management Act (GMA) boundary. The immediate area likely supports an active population of
raccoons, squirrels, and deer. Further away several miles to the north, cougars and black bears
roam the forested hills of Cougar Mountain.
In 2007, Concept Engineering Inc. flagged the stream channel's OHWM (ordinary high water marks)
onsite. The channel was constructed long ago. It was likely constructed for draining the pasture and
farmhouse directly to the south. The channel was constructed in virtually a straight line to the north to
P:\2005\253 J 2\Engineeri ng\Ana lysis-('a lcs\Docu men ts\ \Vord\2.53 32. Standard Strea 111 Study.doc
efficiently convey runoff. Natural stream channels do not nonnally follow straight lines, as they are
usually sinuous because of natural topographic variations. Because the channel's upstream area is so
small and the channel's geometry is so straight, I believe the channel is not a natural channel.
Downstream: Near the site's north property line, the channel funnels into an approximate 15-inch
diameter corrugated polyethylene culvert constructed approximately 5 years ago. Stonnwater is further
conveyed underground by drainage pipe several hundred feet to the north through the Aster Park
subdivision also constructed approx. 5 years ago by Norris Homes. The conveyance system's discharge
point is into a stonn drainage detention pond on the northeast portion of that subdivision.
Upstream: At the site's upstream (south) property line, the offsite drainage channel enters the site. The
drainage channel resembles a narrow swale or ditch. Drainage emerges from a possible wetland and
seeps. From a distance, the offsite soils appeared fairly impenneable. The soils generally resemble till
type soils, a moderately impenneable soil. When it rains, runoff from the pasture gravity sheet flows
toward the low area containing the ditch. Inside the site's south property line, a very small onsite wetland
abutting the stream was found and delineated. Many years ago, I believe a drainage channel was dug in
the site's low point to more efficiently convey runoff through the subject site.
In general, a stream is classified based on its size, presence of fish or fish habitat, seasonal or permanent
flow, intennittent or continuous flow, and if it flows in an artificial channel. Based on Renton Municipal
Code (RMC) 4-3-050Ll, the site's drainage course resembles a class 5 stream. Class 5 streams are
defined as, "non-regulated non-salmon id-bearing waters which meet one or more of the following
criteria:
a. Flow within an artificially constructed channel where no naturally defined channel had
previously existed; and I or
b. Are a surfically isolated water body less than one-half (0.5 acre) (e.g., pond) not meeting the
criteria for a wetland as defined in subsection M of this Section. "
Criteria (a) from above is met. Since runoff flows through an artificial constructed channel where no
naturally defined channel previously existed, it is classified as a class 5 stream per RMC 4-3-050.L. l .a.v.
D. ALTERATIONTOSTREAM
RMC does not regulate class 5 waters (streams), so an impact evaluation is not required. Class 5 streams
do not have buffers and can be altered without city permission (RMC 4-3-050.L.l).
In this case, the stream alteration is for a public benefit; the extension of public sewer. The sewer
extension will allow the 3 future homes to direct their wastewater into the new sewer system which
merges into the existing sewer system. Miles downstream, wastewater enters the regional wastewater
treatment plant for proper sewage treatment. A second public benefit is that the existing home's septic
drainfield will be decommissioned when the home is demolished. Removing the septic system near an
open water channel is especially beneficial, as the stream's water quality will be improved.
A critical areas exemption has been requested for approval from Renton for the proposed sanitary sewer
extension that crosses the stream.
Encl.: Photographs
Stream Map
P :\2U{J5\25.l .\2\Engin(Tring1A11al ysi~-C<1 lcs\Documents\\V1)rd\25 }J 2 .Standard Strcnm Study .doc
November 2008 Stream Photos
Look ing north at rip rap pad and culve rt .
Looking south at stream.
J:\AU TOCA DIPAOJECTS\2005125332\Engineering\Analysis-C alcs\Documents\Word\Photos for Report 3 .doc
November 2008 Stream Photos
Looking north at stream.
Looking southwest at proposed
sanitary sewer alignment.
J:IAUTOCAO\PAOJECTS\2005125332\En g;neer,ng\Analys;s,Calcs\Oocuments\Word\Photos for Report 3.doc
November 2008 Stream Photos
Looking at stream.
Looking northeast across site.
J:\AUTOCAD\PROJECTS\2005\25332\Eng;neering\Analysis-Calcs\Docum ents\Word\Pho tos tor Repor, 3.doc
November 2008 Stream Photos
Near site's south property line,
looking south (upstream) at
stream .
Several hundred feet north (downstream) of site the
stream enters a storm drainage pond.
J:\AUTOCAO\PAOJECTS\2005\25332\Engineering\Analysis-Celcs\Oocuments\Word\Photos for Reparl 3 doc
Supplemental Stream Study
For The
Silver King Short Plat
Located At:
11025 148th Avenue SE
Renton, WA 98059
Tax Parcel Number:
032305-9020
Report Prepared For:
Jonah-Kai Hancock
10025 148 1h Avenue SE
Renton, WA 98059
(206) 234-9673
Report Dated:
January 19, 2009
Concept Engineering, Inc.
Job Number:
25332
Mark Rigos, P.E.
Certified Wetland Biologist
A. UNCLASSIFIED STREAM ASSESSMENT
:·---,
This Supplemental Stream Study was prepared because one is required per City ofRenton's Short Plat
Application Submittal Requirements since the project site contains an unclassified stream. The 0.81-acre
site is in the northeast quadrant of the City of Renton. This property was recently annexed out of
Unincorporated King County. The site is located in the SE Y, of Section 3, Township 23 North, Range 5
East, W.M.
CIVIi_ [NGINE[RING; sunVEYINC,; LANI) USE !'LANN.NG
P :\2006\2 5JJ2\£:ngim:cri ng\t\nulysis-C a le s'-.Dm: umcnb I Word\253 32. Supp.Streum Study .doc
A drainage channel is located in the west-central portion of the site. Seasonally, stormwater runoff flows
south to north in this channel. Onsite, the charmel's dimensions are approximately 1-2 feet wide by 118
feet long by 6 inches -I foot deep. The channel's upstream tributary area is very small, at approx. 1-2
acres. It does not have a large enough tributary area to generate any sort of floodplain.
In 2007, Concept Engineering Inc. flagged the stream channel's OHWM (ordinary high water marks)
onsite. The stream channel appears to have been constructed long ago. It was likely constructed for the
purpose of draining the adjacent pasture and farmhouse to the south. The channel was constructed in
virtually a straight line to the north to convey runoff. Natural stream charmels do not normally follow
straight lines. Because the channels' upstream area is so small and the channel's geometry is so straight, I
believe the charmel is not a natural charmel.
Downstream: Near the site's north proper(y line, the channel funnels into a 15-inch diameter corrugated
polyethylene culvert that was installed approx. 5 years ago. From this culvert, drainage is conveyed north
several hundred feet underground by drainage pipe through the recently constructed Aster Park
subdivision. The drainage ultimately discharges into a storm drainage detention pond on the northeast
portion of Aster Park.
Upstream: At the site's upstream (south) proper(y line, the offsite drainage charmel enters the site. The
drainage charmel resembles a narrow swale or ditch. Drainage emerges from a possible wetland and
seeps. From a distance, the offsite soils appeared fairly impermeable. Onsite and offsite, the soils are
likely till. When it rains, runoff from the pasture gravity sheet flows toward the low area containing the
ditch. Inside the site's south proper(y line, a very small onsite wetland abutting the stream was found and
delineated. Many years ago, I believe a drainage channel was dug in the site's low point to efficiently
convey runoff through the site.
In general, a stream is classified based on its size, presence of fish or fish habitat, seasonal or permanent
flow, intermittent or continuous flow, and if it flows in an artificial charmel. Based on Renton Municipal
Code (RMC) 4-3-0SOLI, the site's drainage charmel resembles a class 5 stream. Class 5 streams are
defined as, "non-regulated non-salmonid-bearing waters which meet one or more of the following
criteria:
a. Flow within an artificially constructed channel where no naturally defined channel had
previously existed; and I or
b. Are a surfical/y isolated water body less than one-half (0.5 acre) (e.g., pond) not meeting the
criteria for a wetland as defined in subsection M of this Section. "
Criteria (a) from above is met. Since drainage flows through an artificially constructed channel where no
naturally defined channel previously existed, the drainage channel is classified as a class 5 stream per
RMC 4-3-050.L. ! .a.v.
B. ALTERATION TO STREAM
RMC does not regulate class 5 waters (streams), so an impact evaluation is not required. Class 5 streams
do not have buffers and can be altered without city permission (RMC 4-3-050.L. l).
In this case, the stream alteration is being performed, in part, as a public benefit; the extension of public
sewer. The sewer extension will allow the 3 future homes to direct their wastewater into the new sewer
system which will merge into the existing sewer system. Miles downstream, the wastewater enters the
regional wastewater treatment plant for proper sewage treatment. A second public benefit is that the
existing home's septic drainfield will be decommissioned when the home is demolished. Removing the
P:\2005\25JJ2\Engineering\Analysis-Calcs\Docume11Ls\Word\25JJ2.Supp. Stream Study.doc
septic system near an open water channel is especially beneficial as the stream could result in improved
water quality conditions.
Although a formal impact evaluation is not required, precautions will be provided to limit environmental
impacts during the sewer installation. Only 2 feet of the sewer pipe will be constructed underneath the
stream channel. This work shall be performed in the dry season when the channel is absent of any water,
so that erosion and sedimentation are less of a concern.
P:\2005\253 32\Engineeri ng\Anal ysis-C.i lc::;\Docurncnb\\Vord\2 .5 .13 2 .Supp. Stream Study.doc