HomeMy WebLinkAboutR_Stream Study_20171129_v2
November 29, 2017
AOA-5029
Jim Dalpay
Dalpay Properties LLC
4033 NE Sunset Boulevard
Renton, WA 98059
SUBJECT: Standard Stream Study for Dalpay Short Plat (LUA17-000234)
Parcel 042305-9032, Renton, WA (Revised)
Dear Jim:
We have updated this stream study for the subject project to address the required
encroachment into the stream buffer for the Lot 1 access drive.
Background
On December 14, 2015 a wetland and stream reconnaissance was conducted on
the subject property utilizing the methodology outlined in the May 2010 Regional
Supplement to the Corps of Engineers Wetland Delineation Manual: Western
Mountains, Valleys, and Coast Region (Version 2.0). One stream (Stream 1) was
identified and delineated within a small ravine that traverses the central portion of
the property. No wetlands were identified on the site.
Stream 1
Stream 1 is a tributary to Honey Creek, which is identified as a Type Np stream per
the City of Renton (COR) mapping. The stream on the subject property is not
mapped on the COR mapping.
Stream 1 drains from north to south through a ravine dominated by a coniferous
forest that includes Douglas fir (Pseudotsuga menziesii), western red cedar (Thuja
plicata), Oregon grape (Mahonia sp.), holly (Ilex sp.), Himalayan blackberry (Rubus
armeniacus), sword fern (Polystichum munitum), and English ivy (Hedera helix).
Jim Dalpay
November 29, 2017
Page 2
Stream 1 was identified as a Class 4 stream as part of a previous short plat
associated with the subject property. As part of the previous application, Stream 1
and the adjacent slopes were placed within a Native Growth Protection Easement
(Recording No. 20050927003163). It is my understanding that the stream dries out
during the summer months and would therefore be considered a Type Ns stream per
the current City of Renton classification system.
City of Renton Mapping
The new stream delineation has been surveyed and is depicted on the survey
drawing. Type Ns streams in the City of Renton currently require a standard 50-foot
buffer plus 15-foot building setback from the ordinary high water of the stream
adjacent new development per RMC 4-3-050.G.2 (Figure 1). When a required
stream buffer falls within a protected slope or very high landslide hazard area, the
stream buffer width must extend to the boundary of the protected slope or very high
landslide hazard area (as determined by the geotechnical consultant).
Proposed Project
The proposed project consists of a 4-lot Short Plat. Access to Lots 2-4 in the
southeast portion of the site would be from Redmond Court NE to the east and
would be constructed outside of all applicable buffers.
Jim Dalpay
November 29, 2017
Page 3
Lot 1 Stream Buffer Crossing
Access to Lot 1 would be provided by the continuation of Redmond Place NE, which
currently terminates along the northern property boundary. There is no other viable
alternative access point available for Lot 1. The proposed driveway must
unavoidably impact 860 s.f. of the historically cleared outer buffer of the stream. As
depicted on the tree survey, there are no significant trees that would be impacted as
part of the driveway construction and the impacted buffer is not located on a
sensitive slope.
Stream buffer crossings associated with transportation crossings such as driveways
are required to meet all of the conditions outlined in RMC 4-3-050.J.2.a (below).
a. Criteria for Administrative Approval of Transportation Crossings in
Stream/Lake or Buffer Areas: Construction of vehicular or non-vehicular
transportation crossings may be permitted in accordance with an approved
stream/lake study subject to the following criteria:
i. The proposed route is determined to have the least impact on the
environment, while meeting City Comprehensive Plan Transportation
Element requirements and standards in RMC 4-6-060; and
There is no other access driveway location for Lot 1 that would have less impact on
the stream buffer. The only other potential access to Lot 1 would be to cross the
forested ravine and stream from the south. This potential crossing would have
significantly greater impacts to the stream buffer and would require both culverting
the stream at the crossing and traversing the steep slope.
It is my understanding that the driveway as proposed is consistent with the City
Comprehensive Plan Transportation Element requirements and standards in RMC 4-
6-060.
ii. The crossing minimizes interruption of downstream movement of
wood and gravel; and
The driveway would cross the buffer only and would not require any work within the
stream channel or adjacent ravine that could potentially interrupt the downstream
movement of wood and gravel within the riparian corridor. Furthermore, the
proposed crossing does not require the removal of any significant trees from the
buffer.
iii. Transportation facilities in buffer areas shall not run parallel to the
water body; and
The proposed driveway crossing would enter Lot 1 and immediately turn west
toward the proposed residence to avoid running parallel to the stream corridor.
Jim Dalpay
November 29, 2017
Page 4
iv. Crossings occur as near to perpendicular with the water body as
possible; and
The proposed crossing of the buffer has been designed to impact the least amount
of buffer area as possible. Upon entering Lot 1, the driveway would turn west and
be as perpendicular as feasible to the riparian corridor.
v. Crossings are designed according to the Washington Department of
Fish and Wildlife Fish Water Crossing Design Guidelines, 2013, and
the National Marine Fisheries Service Guidelines for Salmonid
Passage at Stream Crossings, 2000, as may be updated, or
equivalent manuals as determined by the Administrator; and
There is no proposed crossing of the stream channel and this condition is not
applicable.
vi. Seasonal work windows are determined and made a condition of
approval; and
Although no work associated with the buffer crossing would occur on the slope or
within the stream channel, the condition is noted as it may apply to conditions of the
required Temporary Erosion Control Plan (TESCP) for the development proposal.
vii. Mitigation criteria of subsection L of this Section are met.
Mitigation for the impact of the 860 s.f. of degraded and historically cleared buffer
would occur through the preservation of 860 s.f. of additional forested replacement
buffer located adjacent to Lot 2. The buffer area to be impacted was entirely cleared
by 2005 and does not currently provide any significant stormwater storage, water
quality protection, or habitat functions to the stream corridor.
The proposed buffer replacement area is currently forested and would increase the
size of the protected habitat corridor over existing conditions. The additional buffer
area will also provide increased physical and visual screening to riparian corridor
from the development and will allow for increased potential of large woody debris
recruitment.
Since the buffer replacement area is already forested, no buffer plantings are
proposed and the maintenance and monitoring requirements associated within
mitigation site per RMC 4-3-050.L are not applicable.
Jim Dalpay
November 29, 2017
Page 5
2005 Aerial photo showing Lot 1 cleared as part of
construction to north
If you have any questions regarding the stream study, please give me a call.
Sincerely,
ALTMANN OLIVER ASSOCIATES, LLC
John Altmann
Ecologist
Attachment
PROJECT DRAWN DATE SCALE REVISED Landscape Architecture AOA Environmental Planning &Office (425) 333-4535 PO Box 578Carnation, WA 98014Fax (425) 333-4509 Altmann Oliver Associates, LLC 5029-MIT-02-19-17.dwg
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