HomeMy WebLinkAboutPN_Project_Narrative_190221_v1.pdfPreliminary Project Narrative
For
Madueno Short Plat
General Information:
Madueno Short Plat is a proposed 6-lot single-family development located in South Renton with
the east property line coinciding with the Renton-Kent city limits along 108th Ave SE. The site
consists of a single legal parcel in R-4 zoning with a total site area of 72,986 SF (1.67 acres):
Parcel # 052205-9078
Address: 19805 108th Avenue SE, Renton 98055
The parcels bordering the project site to the north, west, and south are located in R-4 zoning as
Residential Low Density. The northeast corner of the site is developed with an existing residence
and driveway providing access to 108th Avenue SE while the other portion of the site remains
undeveloped and vegetated with evergreen trees and deciduous trees. In addition, there are
offsite trees that may be impacted along the north property line.
The site slopes gently from west to east toward 116th Avenue SE with an average slope of around
2% with an area with 20% slope on the east side of the project site. The grades in the right-of-
way along 106th Avenue SE describe an existing ditch that carries stormwater from south to
north through a series of ditches and culverts.
A small job shack can be anticipated on-site during construction. It is not currently known if a
model home will be utilized as a sales tool for work on the other lots.
Soils:
Cobalt Geosciences, LLC evaluated the soils on site in February 2018 in a series of four test pits.
One test pit exposed 2.5 feet of loose fill overlaying silty sand and gravel. The other three test
pits exposed 1.5 to 2 feet of topsoil. Silty sand and gravel - consistent with glacial till – underlay
these materials in all four test pits in the remaining column of soil sample.
Preliminary earthwork quantities include approximately 2,460 cubic yards of cut (including the
vault) and 2,370 cubic yards of fill to achieve grades shown on the current preliminary grading
plan. These numbers do not factor in actual house foundations, which will likely lower the
current estimated fill amounts if crawl spaces are utilized.
Trees:
Earth Dance Design, LLC evaluated the health and tree viability of the existing trees located on-
site and off-site in the immediate vicinity of the site in July 2018. There are currently 74 existing
trees located on the site that meet the “significant tree” definition defined by tree diameter at
breast height. 9 trees have been classified as “dangerous”, 14 viable trees are located in areas
proposed to be dedicated as right-of-way, leaving 52 on-site significant trees. As a result of site
plan density, buildable areas, grading and utilities, and a proposed tree retention tract, 22 trees
are marked for retention (19 significant, 3 landmark). This represents a 43% retention of existing
trees. Per code, the project is required to retain 30% (15 trees) or plant replacement trees
equivalent to 12 caliper inches / per tree under the retained minimum. Since significant tree
retention exceeds the minimum required, no replacement trees are provided for.
Of the existing trees currently shown to be retained, the following are of note in regard to
developing the plat and may warrant removal prior to final plat completion, providing we stay at
the minimum of 30% retainage:
· Trees #55 & #56: Within the Tree Tract but with driplines that extend into the allowed
building envelope of Lot 6. If retained, any work within the dripline should be at the
direction of the project arborist.
· Tree #57: On lot line between Lot 6 and Tree Tract. If retained, any fencing will need to
be installed around tree.
· Trees #9, #11, #12, #13, #76: In backyard areas of Lots 1, 2, 3 & 6. If retained, any
grading or utility work within driplines should be at the direction of the project arborist.
Note that Tree 11 is on lot line between Lots 2 & 3 – If retained, any fencing will need to
be installed around tree.
· Tree “O”: Off-site Tree behind Lot 2. On property line. Any fencing will need to be
installed around tree.
· Trees “A” through “M”, “P”, “Q”, & “R”: These are off-site trees just north of the site.
Driplines for all these trees extend onto the property with the area of work required for
grading and construction for the public access road. As this work is primary for plat
access, impacts to off-site trees will need to be evaluated by the project arborist on a tree
by tree basis. Replacement trees may be required in some cases if irreparable damage is
caused to these specific off-site trees due to grading / roadway work in those dripline
areas. Tree “R” is on the property line. Any fencing will need to be installed around tree.
Access:
The project proposes a 43-foot dedication to construct a new public right-of-way designed to
residential access standards along the north side of the plat. This public street will provide
vehicular access to each of the 6 lots and the proposed stormwater tract. While the street will be
physically connected to 108th Avenue SE (Benson Hwy), access to/from Benson will be
restricted to emergency vehicles only. Improvements along 108th Avenue SE will only include
replacement of a section of curb / gutter / sidewalk with a new commercial driveway apron
designed to City of Kent standards. A radio-controlled gate will be installed at the back of this
driveway apron that will allow access by Police and Fire in the case of an emergency. For
normal, every-day use, the street will function as a dead-end street. For that purpose, a
hammerhead turnaround is also provided near lots 4 & 5. An additional 10 feet of right-of-way
shall be provided by the property to the north (if / when it develops beyond current use) to bring
the right-of-way to the full 53-foot right-of-way width.
The new right-of-way as it connects to 108th Avenue SE has been configured such that if / when
a general connection is allowed to 108th by the city of Kent, the connection can be modified with
no additional right-of-way dedications needed.
Proposed improvements for the public access road will generally consist of a crowned 26-foot
paving section (20’ drive lane / 6’ parking strip along the south side), vertical curb & gutter, 8-
foot planter strip and 5-foot concrete sidewalk along the south side and vertical curb & gutter on
the north. An additional 8-foot planter strip and 5-foot concrete sidewalk shall be provided by the
property to the north (if / when it develops beyond current use).
Frontage Improvements:
106th Avenue SE
The site fronts 106th Avenue SE to the west. 106th Avenue SE is classified as Residential Access
street. In its existing state within the vicinity of the site, it consists of approximately 22 feet of
pavement with an approximate 8-foot gravel shoulder on the west side and an approximate 2-foot
gravel shoulder on the east. Storm drainage is controlled / conveyed via a system of open ditches
and culvert pipes on the east side behind the shoulder. One the east side, runoff is collected /
conveyed via a system of catch-basins and conveyance pipe located in the middle of the
shoulder. Roadway improvements along our frontage to 106th Avenue SE will include new
vertical curb, gutter, and sidewalk constructed to City of Renton standards providing for a 13-
foot drive lane, 8-foot planter, and 5-foot concrete sidewalk.
Due to the shallow depth of the existing system in 106th, we will be required to replace and
deepen a portion of conveyance system on the west side of the road for approximately 500 feet
north until we can connect to the existing system at an elevation that will accept our on-site
outflow elevation that will work with a gravity system (see discussion in Utility section under
storm).
108th Avenue SE (Benson)
The site fronts 108th Avenue SE (Benson) to the east. 108th Avenue SE is under the jurisdiction
of the City of Kent and classified as a Principal Arterial. At this time, a general connection to
108th Avenue SE has been denied by the city of Kent based on intersection spacing dimensions.
The City of Kent has agreed to an emergency vehicle access by way of an automated, radio-
controlled gate located at the back of sidewalk along 108th Avenue SE at the location where our
internal right-of-way intersects with 108th. A portion of the existing curb/gutter and sidewalk will
be removed and replaced with a new commercial driveway apron at this location. Work within
the 108th Avenue right-of-way will be done to City of Kent Standards and will require final
review and approval by the City of Kent prior to approval of this preliminary short plat.
Utilities:
Storm
As a result of smaller project size and shape (non-dispersing) coupled with existing on-site soil
conditions (non-infiltrating), the project will construct / install on-site detention and water
quality facilities prior to discharge to the existing conveyance system in 106th Avenue SE. Due to
the very shallow condition of this system, deepening a portion of the existing system for
approximately 500 feet north of the site will be required in order to make a gravity system work
for the project (see Frontage Improvements - 106th Ave SE section of this narrative).
The storm drainage system will comprise of roof downspouts, area drains, tightlines, catchbasins
and mainline conveyance pipes that will collect and route drainage to the on-site detention
system.
Sanitary
An 8-inch gravity sewer main will be extended from 106th Avenue SE into the site within the
proposed new right-of-way. All manholes will be located within the paved roadway area. Each
residence will be connected to the proposed new main via 6-inch side sewers.
Water
An 8-inch water main will be extended from 106th Avenue SE into the site within the proposed
new right-of-way. Anticipate one new fire hydrant. Each residence will be served through
individual water meters. Anticipate 1-inch water meters.
Site Statistics:
Zoning designation:
R-4
Existing Use:
Residential single-family
Proposed use:
Residential single-family
Proposed Lots Info:
No. of Lots: 6
Size: Ranging from 9,020 SF to 9,214 SF.
Dedication to the City:
43-foot right-of-way along northern property line (25,737 SF). An additional 10-feet of right-of-
way to the north will be needed at future date to complete sidewalk and planter improvements on
the north side of the proposed road. Said additional right-of-way to be dedicate when / if the
property to the north redevelops.
Proposed Density:
3.66 DU/acre (see density worksheet)
Access:
Access to Lots 1-6 and the proposed storm water tract shall be via a new public road extended
from 106th Avenue SE in a new 43-foot half right-of-way.
Utility Purveyors:
Sanitary Sewer – Soos Creek
Domestic Water – Soos Creek
Anticipated Permits required:
Preliminary Short Plat, Utilities/Clear and Grade, Right-of-Way, Building.
Special features:
No sensitive areas or special features on or near the property.
Estimated Construction Cost:
$700,000 (Home Construction, Public Road Improvements, Utility Infrastructure)
Estimated project Value:
$3,600,000 ($600,000 / home)