Hwy 99 Edmonds - Civil STORM Comment Response Letter_190521.pdfNAVIX
-i I r i
May 21, 2019
Zack Richardson
Stormwater Engineer
City of Edmonds
121 5th Ave N
Edmonds, WA 98020
11235 s.e. 6th street, suite 150 t 425.453.9501
bellevue, wa 98004 f 425.453.8208
navixeng.com a info@navixeng.com
Subject: GRE Edmonds 192-unit; Edmonds, Washington
Permit #BLD20181622 Comment Response
23400 Highway 99, Edmonds, WA 98020
Zack,
Thank you for the review of the GRE Edmonds 192-unit building permit submittal. We have
received the review comments, dated February 28, 2019, and have revised the submittal
documents accordingly. Please see our responses to your comments as indicated below.
Genera
The modelled vault does not match the one shown on the plans; review all vault values
and elevations and ensure the calculations match the plans, most specifically at the
riser.
a. Riser to invert appears to be shown as 5.75' and modelled as 6'
b. Multiple orifices were modeled but not shown on plans.
c. Notch height does not match
Response: The WWHM modelling submitted with the revised storm report is coordinated with
the vault details shown on C5.20.
Drainage Report
1. Revise MR #3 section to exclude reference to appendix B (these are LID BMPs not
source control BMPs) and update text to note and address the trash enclosure (storage
of materials) and the proposed pet relief areas; include structural BMPs where needed,
and operational source control guidance in report appendix as needed.
Response: MR#3 has been revised to exclude reference to appendix B and updated to note
and address the trash enclosure, proposed pet relief areas, and structural BMPs. Operational
source control guidance has been added to Appendix x.
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May 21, 2019
2. Expand MR #6 to address the roof and courtyard/amenity level surfacing; explain how
the engineer ensured the roof and amenity surfaces and improvements are non -
pollution generating (typically accomplished by coating metal roof materials and
ensuring all mechanical/HVAC equipment includes internal spill containment device;
update plans as needed to reflect these requirements.
a. The roof plan was reviewed and did not appear to contain any direction to this
effect.
b. The pet relief area appears to be a pollution generating impervious surface and
shall be treated accordingly.
i. Note: If this area is to drain to the sanitary sewer line, it must be covered
and isolated from rainfall (per sewer standards).
Response: MR #6 has been expanded to address the roof and courtyard amenity areas. All
roof coverings, including pavers, planters, guardrails, pergola, aggregate, waterproofing at
the courtyard will be non -pollution generating. All mechanical units to include internal spill
containment devices.
3. Expand MR #9 to explain the unique challenges of the maintaining this particular vault
placement within the building footprint and covered garage and update Appendix'C'
with project specific requirements as needed.
It does not appear that a typical vactor truck can fit into the garage entry way
and may not be able to operate within the garage clearance; address how the
vault will be alternatively maintained or provide evidence that typical vactor
trucks can access the necessary points of the vault.
Response: MR #9 has been updated to include reference to the Detention Vault Maintenance
section of the report, which describes how a typical vactor truck will service the vault.
Additionally, MR #9 now includes a brief summary of the vault maintenance plan.
4. Expand text (suggest in developed conditions section) to describe how drains within the
underground garage will be handled (i.e. connected to sanitary sewer).
Response: Underground garage drainage has been addressed in the Post -Development
Stormwater Runoff section. Additionally, Note 5 on sheet C5.00 states that all floor drains
within the garage must be connected to sanitary sewer.
5. Update table 2 as needed so that the new + replaced rows sum to the proposed hard
surfaces/effective impervious.
Response: Table 2 has been updated to the correct areas.
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6. Update conveyance discussion (page 26) to provide the un-detained 100-year flow rate
instead of the detained 100-year peak flow rate; if pipe capacity shown exceeds the
revise flow rate, additional calculations, documentation, or explanation may be
necessary.
Response: Conveyance discussion has been updated to address the un-detained 100 year
flow rate. The proposed 12-inch outfall pipe provides adequate capacity for the undetained
flow.
7. Include a developed conditions or impervious areas exhibit which hatches and
quantifies the areas considered when calculating the total project impervious surface;
note flow to the detention system vs bypass areas separately and note pollution
generating vs non -pollution generating separately.
a. It appears that no open grate collection points/drains are provided on the east
and south sides of the building and the drain on the west side bypass detention, -
it appears that all site surfaces are currently bypassing the detention system.
i. Ensure flow control calculation accurately reflects any bypass areas using
a point of compliance set-up within WWHM.
ii. Clarify how bypass areas are meeting the requirement of MR #5.
Response: Figure 5. Proposed Conditions Map has been updated to include bypass
information and Figure 6 has been added to show bypass areas. Bypass area is discussed
relative to MR #5 under the MR #5 section.
Sheet C2.00
1. The proposed access road appears to be located within a decent cross slope (-7%)
which likely requires grading to make usable for the type of vehicles anticipated, or
more likely, will not be the practical location of the contractor selected access. Show
grading for the access road, revise location, and/or provide explanation of why this is
believed to be the most practical location and usable without additional grading.
Response: Construction access road has been revised for right -turn in and right -turn out off/
on Highway 99, per coordination with the contractor. Sheet C2.00 has been updated to
reflect this layout. Please refer to the contractor -provided Traffic Control Plans and Haul
Route Plan for additional information.
2. Revise TESC plan as needed to clarify the method of discharging water from the holding
tank to the public system across the public walkway.
a. If using the permanent proposed outfall pipe (underground), show the required
permanent storm drain features on this sheet and update notes as needed to
more clearly state the contractor may not proceed with clearing and grading
until the outfall is constructed and approved and the sidewalk surfacing is
restored to the satisfaction of the inspector.
Response: Note 8 has been updated to include clarification. Prior to vault construction, the
contractor will provide a temporary sediment trap and sump pit as shown on C2.00.
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Collected runoff will be discharged to the public stormwater system via the existing storm
pipe that currently passes through the site and connects to the public system in Highway 99.
Sheet C4.00
Add note to indicate that all landscaped areas must receive amended soils treatment
per BMP 5.13 and include specification or detail sufficient for the contractor to install
soils meeting this requirement (or reference location in landscape plans where this
information exists).
Response: Note #4 has been added to this sheet.
Sheet C5.00
1. Show the roof drain lines; it is not clear how downspouts or roof lines will be routed
back into the vault or possibly if internal drain lines are proposed within the building
structure.
Response: Internal drain lines route stormwater collected on the roof to the detention vault.
The plumbing design is design -build, but the detention vault has been designed to accept
flows in two locations, as shown in the vault detail on sheet C5.20. If needed, additional inlets
will be coordinate with the design -build plumbing contractor and structural engineer.
2. Add callout to the footing drain stub end of the footing drain line: Connect footing
drains only.
Response: A callout has been added to this sheet.
3. Identify elevations at the existing storm drain crossing over the proposed sewer line
just west of SDMH #1; provide direction for supporting/preserving the existing utility
while installing sewer beneath.
Response: Crossing information and Note 6 have been added to the plan.
4. Create an additional cross section accurately showing all utilities and limits of footings
between the west property line and west building limits; reviewer has concern for
feasibility of so many improvements in such a small area if other utilities or roof/footing
lines are needed in this location.
Response: A cross section along the west property line is shown in Detail 3/Sheet C4.20.
Careful coordination will be required by the contractor to install the sewer, storm, and
shoring along the west frontage.
5. It appears CB #4 exceeds 5'to invert and must be a Type 2; update or clarify as
needed.
Response: CB #4 has been updated to be a Type Il.
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6. Overlay the P1 floor plan on this plan sheet, shaded back, to confirm alignment of vault
access points.
Response: P1 floor plan grid lines have been added and shaded back. Additionally, the
Foundation Drainage Plan, G.00, is included with this set, which illustrates the foundation
drainage system relative to the foundation plan, detention vault, and outfall system.
Sheet C5.20
Provide additional detail of wall penetration points (sleeve, locking gaskets, cast -in -place
around pipe, etc) as needed for construction of the proposed storm alignment.
a. A generic sleeve detail was provided on the structural sheets but is not clear
that this is sufficient for construction or that it accurately accounts for the 12"
pipe through rebar spaced at 12" centers. Updated details or provide
confirmation of coordination with structural plans in response as needed.
Response: The wall penetrations with the 12-inch storm outfall pipe have been coordinated
with the structural engineer. Structural details address the penetrations and are shown on
S3.10.
We hope you find the resolution of the review comments acceptable. Please feel free to
contact me with any questions or coordination items you have at (425) 458-7900 or
oe@navixeng.com.
Sincerely,
. /
Joe Taflin, P.E., LEED AP
Principal
Hwy 99 Edmonds - Comment Response Letter-190508doc