17-105489-Addendum to Critical Areas Report-11-12-2021-V2
Wet.land, LLC
Jennifer Marriott, PWS
15803 Bear Creek Parkway
Unit E513
Redmond, WA 98052
10 October 2021
Jim Harris
City of Federal Way
Department of Community Development
PROJECT: Woodbridge Business Park, Federal Way, Washington
SUBJECT: Addendum to 9 April 2020 Critical Areas Report and Proposed Mitigation Plan
Dear Jim,
The City provided comments on this Project in the spring of 2021 that included ESA’s review of the critical areas
information provided as part of this application. ESA’s review covered the most recent critical areas report titled
Critical Areas Report and Proposed Mitigation Plan, dated 9 April 2020 as prepared by Talasaea Consultants. I have
been part of this Project since its beginnings, and have continued my role even after leaving Talasaea in March of
2020. In order to respect the Project documents, rather than revise the April 2020 Talasaea Report or create a new
report, this letter will serve as an addendum to the April 2020 Talasaea critical areas report . Responses to ESA’s
comments on this application are provided as a separate document.
EXISTING CONDITIONS PAGE 2
1. Existing Conditions
1.1 Ordinary High Water Mark (OHWM)
The ordinary high water marks (OHWM) of the onsite streams and North Lake were determined based on the
Washington State Department of Ecology (ECY) guidance document Determining the Ordinary High Water Mark for
Shoreline Management Act Compliance in Washington State (October 2016, Publication No. 16-06-029). Delineations
were done between in late winter to spring of 2016. Stream AC was delineated based on the location of the tops of
bank for this artificial channel. North Lake was more complicated as the north end of the lake extends into a large
wetland complex. The lake OHWM was also used as the starting location to determine the extent of the Shoreline
Management Zone (SMZ).
The OHWM of North Lake was established based on a clear topographic break along the western lake edge. Where
wetlands occur adjacent to the open water portion of the lake, the OHWM was established based on the species of
vegetation present. Aquatic plants and other obligate (OBL) plants were considered to be within the OHWM based
on ECY guidance, while Facultative Wetland (FACW) or drier plants remained outside of the OHWM. Wetland
vegetation along the western edge of the lake typically lacks both aquatic vegetation and OBL wetland vegetation,
so the OHWM focused on the presence of a clear topographic break (bank) and the edge of the open water portion
of the lake. Wetland conditions that extended up the hill were dominated by FACW or facultative (FAC) species, and
thus were excluded from the OHWM delineation.
The OHWM was more complicated at the north end of the lake, east of the WDFW boat ramp, due to the large
wetland complex (Wetland CD) that occurs there. The upper limits of Wetland CD (not in Project Area) was
delineated as part of the greater critical areas evaluations of the Woodbridge Property, and included within the
Lakefront Boundary Line Adjustment application. The OHWM is located through Wetland CD such that this wetland
occurs both inside and outside of the OHWM of the lake. The OHWM was not field delineated through this specific
parcel/Wetland CD. Rather, the OHWM was approximated based on aerial imagery with field spot checks to be
located outside of the OBL wetland vegetation. Spot elevations at certain locations and the use of lidar elevations
combined were used to delineate the OHWM at this location. The remainder of the OHWM to the west and south
where the OHWM is adjacent to the Project Area was field delineated.
In addition to the OHWM of North Lake, this lake is also a Shoreline of the State. Therefore, in addition to delineating
the OHWM of the lake, the OHWM was then used to identify areas that occur within the Shoreline Management Zone
(SMZ). The SMZ extends 200 feet from the delineated OHWM of North Lake, and extends to encompass the entirety
of any wetlands that occur even partially within the 200-foot SMZ. This inclusion of wetlands within the SMZ that
occur even partially within the SMZ was the main reason why a field delineation of the OHWM of North Lake
northeast of the Project Area was not conducted or deemed an efficient use of time.
1.2 Wetlands Clarification
Wetlands KG, KH, KI, KJ, KK, KL, and KM were removed because these areas were reevaluated and removed from
the plans due to their extremely small size. However, since these features were identified within the Boundary Line
EXISTING CONDITIONS PAGE 3
Adjustments (BLA) for this area, these seven (7) wetlands are being added back into the critical areas report. The
attached revised Critical Areas plan sheets and mitigation plan have been revised to reflect the presence of these
wetlands.
Wetlands KA, KB, KC, KD, KF, KN, KT, KU, KV, KW (previously included) and Wetlands KG, KH, KI,
KJ, KK, KL, and KM (readded back in)
These wetlands are a series of small slope and depressional wetlands that occur north of South 336th Street. These
herbaceous wetlands are dominated by pasture grasses, typically a mix of rye (Lolium spp.), fescues (Festuca spp.),
bentgrasses (Agrostis spp.), velvet grass (Holcus lanatus), sweet vernal grass (Anthoxanthum odoratum), and others.
WETLAND BUFFER IMPACTS DISCUSSION PAGE 4
2. Wetland Buffer Impacts Discussion
Certain development within buffers is allowed as outlined in FWRC 19.145.440 Development within wetland buffers,
including trails and stormwater management facilities, with buffer averaging or enhancement allowed to modify
buffers where needed. A detailed assessment of buffer modifications is outlined below. This assessment excludes
all wetlands that are proposed to be fully filled as these wetlands will not have post-development buffers
remaining. As a quick summary:
Buffer Impacts 3,024 square feet-Permanent
• Permanent Buffer Impacts 3,024 square feet
• Stormwater Ponds Nos 2 and 3 maintenance access road
• Temporary Disturbances 29,819 square feet
• Grading Impacts (multiple wetlands)
• Existing Trail Restoration (multiple wetlands)
• Hydrologic connection swale (Wetland BR)
Buffer Mitigation 60,116 square feet
• Wetland Buffer Replacement 3,184 square feet
• Replacement for Permanent Buffer Impacts
• Wetland Buffer Creation 27,113 square feet
• New buffer added between wetlands and Project (multiple wetlands)
• Wetland Buffer Restoration 29,819 square feet
• Restoration of grading related impacts (multiple wetlands)
• Restoration of existing unpaved trail (multiple wetlands)
• Restoration of buffer around hydrologic connection swale (Wetland BR)
Table 1. Summary of Wetland Buffer Standards, Impacts, and Mitigation Proposed.
# Wetland
ID
Impact
Status
Standard
Buffer
(feet),
FWRC
Ch.19
25%
Reduced
Buffer
(feet),
FWRC
Ch.19
Post-Development Buffers
Minimum
Buffer
Width
(feet)
Buffer
Reduced
(Loss)
(square
feet)
Buffer
Creation
(Gain)
(square
feet)
Buffer Restoration
(Temporary
Impacts*)(square
feet)
1 AE Filled 60 N/A N/A N/A N/A N/A
2 AF Filled 60 N/A N/A N/A N/A N/A
3 AG Partial Fill 60 45 46.3 ** 3,100 6248
4 AH Filled 60 N/A N/A N/A N/A N/A
5 AI
OUT OF PROJECT AREA 6 AJ
7 AL
8 AM
WETLAND BUFFER IMPACTS DISCUSSION PAGE 5
# Wetland
ID
Impact
Status
Standard
Buffer
(feet),
FWRC
Ch.19
25%
Reduced
Buffer
(feet),
FWRC
Ch.19
Post-Development Buffers
Minimum
Buffer
Width
(feet)
Buffer
Reduced
(Loss)
(square
feet)
Buffer
Creation
(Gain)
(square
feet)
Buffer Restoration
(Temporary
Impacts*)(square
feet)
9 AO
10 AR
11 AS
12 AV No Impact 60 45 30** ** 8473 N/A
13 BA-2 OUT OF PROJECT AREA
14 BR No Impact 105 78.75 105 None None 362
15 BS (N) Filled 60 N/A N/A N/A N/A N/A
16 BS (S) No Impact 40 30 40 None None None
17 CG OUT OF PROJECT AREA
18 DE Partial Fill 60 45 45 ** 11860 5678
19 DF No Impact 60 45 60 None None None
20 DG No Impact 60 45 60 None None None
21 DH No Impact 60 45 60 None None None
22 DI No Impact 60 45 60 None None None
23 DK Indirect
Impact 60 45 ** ** 3250 0
24 EI Filled 40 N/A N/A N/A N/A N/A
25 EJ Filled 60 N/A N/A N/A N/A N/A
26 EK Filled 60 N/A N/A N/A N/A N/A
27 EL Filled 60 N/A N/A N/A N/A N/A
28 EM Filled 60 N/A N/A N/A N/A N/A
29 FB No Impact 60 45 60 None None None
30 FD Filled 40 N/A N/A N/A N/A N/A
31 FE Filled 105 N/A N/A N/A N/A N/A
32 FF Filled 40 N/A N/A N/A N/A N/A
33 GB (N) No Impact 60 45 60 None 430 0
34 IA
OUT OF PROJECT AREA
35 KA
36 KB
37 KC
38 KD
39 KF
40 KN
41 KT
42 KU
43 KV
44 KW
45 PK
Trail Restoration 17531
TOTALS 27,113 29819
*Temporary impacts related to buffer restoration values exclude the trail restoration. The trail restoration values are listed as separate
from any specific wetland.
**These wetlands either had indirect wetland impacts that modified the standard buffer, or lacked a full standard buffer due to existing
constraints of the Site. Details by wetland are discussed below.
WETLAND BUFFER IMPACTS DISCUSSION PAGE 6
2.1 Wetland AG
Partial fill of Wetland AG is proposed with associated indirect wetland impacts. Direct fill of 2,063 square feet of
Wetland AG is proposed for a permanent impact to 32% of this wetland for filling the northern arm of this wetland
that wraps around an existing stormwater pond. This impact is required for the modification of this existing
stormwater pond into a newly designed pond that will meet current requirements. As part of this direct fill, indirect
wetland impacts are proposed to 427 square feet of this wetland to ensure a minimum 45-foot buffer from the
remainder of this wetland post-development. All of the direct and indirect wetland impacts are proposed to be
mitigated through the purchase of in-lieu fee credits. Buffer impacts are not being directly calculated for this
wetland because partial wetland fill is required. The indirect wetland impacts address the wetland as buffer to
ensure a minimum 45-foot buffer is maintained consistent with the minimum requirements for both buffer
averaging and enhancement which allow for a 25% buffer reduction of the standard 60-foot buffer for this wetland.
Additional buffer modifications for this wetland include 5,413 square feet of buffer that will be temporarily
impacted through site grading that will be restored post-construction with an additional 2,926 square feet of new
buffer added as additional compensation for impacted buffers. Other temporary buffer impacts proposed during
construction will result from the restoration of an existing pedestrian trail into forested, functional buffer. These
temporary impacts for trail to buffer restoration are not tallied based on FWRC 19.145.440 as these are existing
trails that will be restored as buffer in place through removal of the trail substrate, soil decompaction and
amendments as needed, and subsequent replanting concurrent with other onsite buffer mitigation activities.
Figure 1. Snip from Revised Mitigation Plans showing dimensions of impacts and mitigation.
WETLAND BUF FER IMPACTS DISCUSSION PAGE 7
2.2 Wetland AV
Wetland AV is an irregularly-shaped wetland that is constrained by existing features on 3 of 4 sides. No direct
impacts are proposed to Wetland AV. However, indirect impacts of 406 square feet (3% of the total wetland area)
will result due to a necessary access road to the proposed stormwater ponds #3 and 4, discussed in more detail
below. Additional temporary impacts will result from the restoration of an existing unpaved access road to
functional buffer. This unpaved access road has deep ditches on either side of it that have a negative impact on
wetland hydrology in this area. Current buffers for Wetland AV range between almost none (south end) to roughly
11-12 feet to the east and west due to existing development constraints that have vegetative and hydrologic
impacts on this wetland. The buffer at the north end overlaps with buffers from Wetland DK, thus there is no “outer”
25% of the buffer for this wetland where a standard application of FWRC 19.145.440 could be implemented. The
same is true around the entirety of this wetland due to the constrained existing conditions of this wetland and its
buffer.
Figure 2. Snip from Revised Mitigation Plans for Wetland AV (south end, left; north end, right).
Large stormwater ponds are required to accommodate this Project due to the large area of impervious surfaces
proposed. Restrictions on development into the meadow west of the proposed project footprint due to this area
being of historical significance to the view corridor associated with the headquarters building to the south heavily
restricts where stormwater ponds can be placed. The use of vaults has been evaluated and are being used to a
limited extent where feasible to reduce the stormwater pond area requirements. Despite this, extensive ponds are
still necessary, and where ponds are placed, maintenance access is necessary. Multiple locations were evaluated
for placement of the maintenance access to the stormwater ponds, and it was decided the most direct route was
best to reduce the footprint of this access road within the critical areas that occur between the ponds and the
interior roads of the proposed development. Consideration was given to using the existing unpaved trail. However,
the current conditions of this trail are not adequate for safe access of maintenance vehicles, so work would have
been required to expand this feature into a safe access road. Proximity of this trail to Wetland AV was also a
consideration so the proposed access road location moves this road to the most direct route, thus limiting buffer
impacts, while also keeping this trail a maximum, feasible distance from all wetlands. Based on this assessment, it
was determined that the section of buffer between Wetlands AV and DK was the best location with the remainder
WETLAND BUFFER IMPACTS DISCUSSION PAGE 8
of the unpaved access road to be restored as functional buffer with the side ditches removed to also restore more
natural surface water movement through this area.
The indirect impacts proposed to the Wetland AV buffer to accommodate this access road will be compensated for
through the purchase of in-lieu fee credits. The stormwater maintenance access road located through the buffers
between Wetlands AV and DK will result in 3,024 square feet of buffer loss that will be replaced with the addition of
3,184 square feet of buffer, as required by buffer averaging. The indirect impacts resulting from this buffer intrusion
exceed the 25% reduction allowed per code due to the existing constraints of this location, but the nearest
interpretation of buffer averaging as feasible given existing conditions was applied to this location. Additional
buffer was added adjacent to Wetland AV totaling 7,792 square feet between the wetland and the proposed
development to the east as the existing edge of development was adjusted. These areas of new buffer will be
restored to a fully vegetation condition, including removal of all existing structures within these areas currently.
Restoration of the unpaved vehicular/pedestrian trail that extends along the southern and western boundaries of
Wetland AV will provide expanded buffers in those areas that will have a net positive benefit to both vegetation and
hydrology.
2.3 Wetland BR
Wetland BR will remain unimpacted with no substantial buffer impacts anticipated. A segment of a pedestrian trail
does occur within the buffer of Wetland BR that will be restored in place, requiring temporary impacts for the
restoration work. A small swale is also proposed within the Wetland BR buffer that will temporarily disturb 362
square feet of buffer for construction of this swale (see Figure 1 above). No dispersion trench or other structure is
proposed in association with this swale. This swale is not associated with the Project’s stormwater infrastructure,
but rather is intended to provide a clear hydrologic connection between Wetland AV and Wetland BR. The swale
will be field-located during construction to avoid any impacts to trees, and will be hydroseeded with a native grass
blend.
2.4 Wetland BS-South
Wetland BS-South will remain unimpacted with the only buffer impact proposed being the pedestrian trail
restoration.
2.5 Wetland DE
Direct placement of fill into Wetland DE will total 264 square feet (1% of the total wetland area) with an additional
3,961 square feet of indirect wetland impacts resulting from the insufficiently buffered wetland. The indirect
impacts were determined based on the minimum wetland area required to provide a minimum 45-foot buffer. Both
direct and indirect wetland impacts will be compensated for through the purchase of in-lieu fee credits.
New buffer totally 11,860 square feet will be added east of the wetland in an area already vegetated with native
species, but supplemental mid-canopy and understory species will be added to enhance the existing conditions.
This area of buffer is dominated by native conifers with a sparse understory and low species diversity. This exceeds
WETLAND BUFFER IMPACTS DISCUSSION PAGE 9
the requirements for buffer averaging by giving back more than what was lost. Portions of the remaining buffer
north of the indirect impacts proposed will be temporarily disturbed for construction, but will be restored post-
construction as native buffer.
Figure 3. Snip from Revised Mitigation Plans of Wetland DE.
2.6 Wetland DF
Wetland DF will remain unimpacted by this Project. No buffer impacts to this wetland are proposed.
2.7 Wetland DG
Wetland DG will remain unimpacted by this Project. No buffer impacts to this wetland are proposed.
2.8 Wetland DH
Wetland DH will remain unimpacted by this Project. No buffer impacts to this wetland are proposed.
2.9 Wetland DI
Wetland DI will remain unimpacted by this Project. No buffer impacts to this wetland are proposed.
WETLAND BUFFER IMPACTS DISCUSSION PAGE 10
2.10 Wetland DK
Wetland DK has a standard 60-foot buffer that overlaps the Wetland AV buffer to the south. No direct impacts to
this wetland are proposed. However, indirect impacts totaling 1,981 square feet are proposed to accommodate the
maintenance access road for the proposed stormwater ponds west of this wetland. A detailed discussion on the
location of this access road was provided above under Section 2.2. Portions of the unpaved access road also occur
within the buffer of this wetland that will be temporarily impacted for restoration activities.
The stormwater pond maintenance access road will require the loss of 3,024 square feet of buffer that overlaps
both Wetlands AV and DK. Buffer averaging will be used to accommodate this buffer impact with a total of 3,184
square feet of buffer added to the standard buffers of this and adjacent wetlands. In addition to the targeted buffer
replacement of 3,184 square feet, an additional 3,250 square feet of buffer will be provided adjacent to the Wetland
DK buffer.
Figure 4. Snip from Revised Mitigation Plans of Wetland DK.
2.11 Wetland FB
Wetland FB will remain unimpacted by this Project. No buffer impacts to this wetland are proposed.
2.12 Wetland GB-North
Wetland GB-North will remain mostly unimpacted by this Project. No direct wetland impacts are proposed. Indirect
impacts totally 18 square feet are proposed due to the encroachment into the standard 60-foot buffer for this
wetland. The indirect wetland impacts were calculated based on a required 45-foot minimum buffer. Temporary
buffer impacts will occur to the outer 25% of the buffer of this wetland to accommodate the Project with these
areas being restored post-construction to restore the full 60-foot buffer except where the indirect wetland impact
is proposed. Buffer replacement is provided north of Wetland GB-North totaling 430 square feet. In addition to
WETLAND BUFFER IMPACTS DISCUSSION PAGE 11
these buffer modifications, the trail identified to be restored also occurs through the eastern buffer for this wetland
for additional temporary buffer disturbances that will ultimately be restored to fully functional, native buffer.
Figure 5. Snip from Revised Mitigation Plans for Wetland GB-North.
SUMMARY PAGE 12
3. Summary
As described above – in addition to all direct and indirect wetland impacts being compensated for through the
purchase of in-lieu fee credits, buffer intrusions are generally kept within the allowable thresholds of no more than
25% reductions except where existing conditions lack a full standard buffer. Permanent buffer impacts are
restricted to only 3,024 square feet which will be directly offset through the addition of 3,184 square feet of
replacement buffer. Temporary buffer impacts are proposed to accommodate the site plan grading, restore an
existing unpaved access road/trail as forested buffer, and to construct a hydrologic connection swale between
Wetlands AV and BR that will be field located to avoid any tree impacts. All temporary buffer impacts will be fully
restored post-construction for no net loss of buffer functions. Beyond these buffer modifications, voluntary buffer
totaling an added 27,113 square feet will be provided around the remaining wetlands on the Site. These combined
efforts will ensure there will be no net loss of wetland buffers.
Should you have any questions or require additional information regarding this Project, please contact me at
jen@wet.land (cell: 813-846-1684).
Jennifer Marriott, PWS
Owner, Wet.land, LLC