HomeMy WebLinkAboutI. Req for Recon -TPWAG (1/21/2015) z
Date: Wed,Jan 21, 2015
To: City of Renton
Hearing Examiner Phil Olbrechts mailto:olbrechtslaw@gmail.com
CITY OF RENTOIV
City of Rentonr
y Wa
1055 Grad ,
Way JAN � 1 2015
Renton, WA 98057
RECEIVED
CITY CLERK'S OFFICE
From: Tiffany Park Woods Advocacy Group mailto:renton-opposites@comcast.net
1725 Pierce Avenue SE
Renton, WA 98058
Subject: Reserve at Tiffany Park PP- Hearing Examiner Decision (LUA13-001572)
Request for Reconsideration
Dear Mr. Olbrechts:
This letter constitutes Tiffany Park Woods Advocacy Group's Request for Reconsideration pursuant to RMC 4-
8-110(E)(13). TPWAG has elected to pursue this Request for Reconsideration Pro Se and hereby designates
Renate Beedon as the designated representative.
References
• Letter entitled, "RE:The Reserve at Tiffany Park- Preliminary Plat- Preliminary Plat and SEPA Appeals -
LUA13-001572, ECF, PP, CAE - Final Decision", from Phil Olbrechts- City of Renton Hearing Examiner, dated
Jan 8, 2015.
Scope
• The Hearing Examiner's decision provides inadequate mitigation for the impacts on the environment and
on the surrounding community of Applicant's proposed development to support a DNS-M determination
under SEPA.
• The City of Renton has authority to ask for mitigation under SEPA, and TPWAG asks the City of Renton (via
the Hearing Examiner)to exercise that authority in the areas discussed in this letter.
• An environmental impact statement is justified and must be prepared whenever significant adverse
impacts on the environment are probable, not just when they are inevitable. If an environmental
statement is required by the weight of the evidence and if the responsible city authority does not require
an environmental impact statement then the decision is clearly erroneous.
Wetlands
Problems
• Wetland determination, measuring and staking
One of our concerns is the wetlands and the way they have been determined, measured and staked.
As you can see from our comments below, we believe that the wetland depiction alone has been
done incorrectly and therefore question the way other studies pertaining to this development have
TPWAG Request for Reconsideration Page 1 of 20
been conducted. An EIS� ild clearly provide the city and all inte _.,ced parties with information that
is correct and fully evaluate the significant adverse impacts on the environment.
The ORIGINAL study by Otak pointed out many discrepancies in the original study submitted by
Schulz. Specifically, this study claimed that the wetlands are actually larger than the original study
submitted by Schulz.
After the Applicant received the Otak study, a meeting was held between the City of Renton, Schulz
and Otak. This was an on-site meeting where apparently the Applicant convinced the Otak
consultants that the original study by Schulz was correct and the OTAK study was not. If you look at
and compare both reports, you can see significant changes between the two versions of Otak studies.
One thing they did agree on is the additional wetland D.
OTAK Secondary
Review Memo-4-3-1•
• As you can see from the pictures taken On January 16, 2015, the wetland boundary markers and in
some cases even the wetland buffer markers are standing in bodies of water. This is NOT after a
record rainfall, but during a typical day in January. This is of great concern to us, as it suggests that
the boundary of wetland B and possibly wetland C were not correctly delineated.
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TPWAG Request for Reconsideration Page 2 of 20
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TPWAG Request for • •- • '.•- 11 of 20
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• We are supplying copy of a topographical map showing the location of trees and wetlands upon which
we indicate location of photos taken on January 16, 2014.. (Topographic Survey, Renton School
District, February 2008)
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TPWAG Request for Reconsideration Page 12 of 20
• We are also providing you with a Tree Cutting/Land Clearing Plan, which shows how the proposed lots
are appearing to encroach onto the wetlands B and C, in particular lots 70, 79 and 80.
RESERVE AT TIFFANY PARK
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TPWAG Request for Reconsideration Page 13 of 20
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EXHIBIT 18
• Also encroaching onto wetland C is a street. On the "Preliminary Cover Sheet for Tiffany Park" chart it
looks like the street is cutting right into the wetland.
• These encroachments appear on the Tree Cutting/Land Clearing Plan dated in 2014. (date is too small
to read).
• In addition,on the "Preliminary Cover Sheet for Tiffany Park" the wetland is encroached even more
than on the previous maps. In other words, it appears that the wetlands keep shrinking to make room
for proposed lots.
TPWAG Request for Reconsideration Page 14 of 20
•
• The photos taken on January 16 clearly show that several wetland boundary and wetland buffer
markers are clearly inside of the wetland boundaries and/or buffers. This is of great concern to
TPWAG. The maps provided by the Applicant show that plats and streets already encroach onto
wetland boundaries acknowledged by the Applicant. If we,TPWAG, are correct in our assumption
that the wetlands have been marked incorrectly and that the wetlands are bigger than depicted by
the Applicant, than the proposed lots and street will greatly violate the wetland buffers and therefore
the wetland code/regulations, etc.
•
• We believe that this aspect alone should call for an EIS, since it is possible that more errors or
oversights like with the wetlands have been made throughout the whole proposed development.
•
We hope that at least the wetland delineation will be revisited and re-staked and then reviewed again
Relief Requested
• Discount the one-sided testimony of Applicant's wetlands expert (because the property owner refuses
to allow TPWAG to bring an independent expert on the property)
• Require the property owner to allow TPWAG to bring a wetlands expert on site, allow adequate time
for the expert to prepare a report, and then hold a meeting to examine the results.
• Require an EIS to resolve the unanswered probable significant environmental impacts as raised by
Steve Neugebauer in his testimony before the Hearing Examiner, and as are raised in this letter.
Trees
Problems
• During the Hearing Examiner's meetings on Nov 18, 2014 and Dec 8, 2014, we witnessed public
testimony from Claudia Donnelly and Jill Jones showing how the developer had apparently removed
all trees from another development, even though the City of Renton requires them to retain trees.
• Therefore, we request that the City of Renton ensure that the developer doesn't intentionally or
carelessly damage the few trees that are required to be retained under city ordinance, and then use
that as legal loophole to circumvent city ordinance and remove the "damaged" trees.
Relief Requested
• Consider assigning a person on site during construction hours to monitor activities to ensure code
compliance.
• Consider steep fines for careless or intentional damage to trees.
• If trees are damaged and must be removed, require Applicant to replace the damaged trees with
equivalent *mature* trees, and prohibit them from using any of the original canopy from the
removed tree for any purpose other than to allow the new tree to grow.
Storm Water
Problems
• Per Steve Neugebauer's testimony, removing trees will remove 75%of the property's ability to process
storm water.
TPWAG Request for Reconsideration Page 15 of 20
• 24" pipe (as proposed by A:, .icant) is barely good enough for a 101 .r storm. 100-year storms are
common. We may have a few 100-year storms in any calendar year. Thus, it is likely that the
neighboring properties will be flooded regularly as a result of the proposed development.
Relief Requested
• Consider requiring a larger storm water drainpipe along SE 18th Street.
• Consider requiring "pervious" pavement (that allows water through it) on all streets, sidewalks and
driveways, so that the storm water can be naturally mitigated on site.
• Consider requiring retention of at least 6" of topsoil on all exposed surfaces (e.g., lawns)to minimize
the need for watering, and so that the storm water can be naturally mitigated on site.
• TPWAG requests that storm water management studies, calculations be completed in compliance
with the City of Renton Storm Water Management Requirements, as further defined by the adopted
King County Surface Water Design Manual; sections which specifically address this issue are titled:
Core Requirements#2 Off site Analysis, and Core Requirements#4 Conveyance Systems. The City of
Renton has some added amendments for special community situations.
Roof Runoff
Problems
• Although roof runoff by itself may not be a pollutant, when it is mixed with chemicals and pesticides
used in the yard it becomes a pollutant.
• Although roof runoff may not be a target pollution-generating surface, roof runoff is still subject to
flow control per Core Requirement#3 which mandates that the City may require design adjustments
per the wetland hydrology protection guidelines in Reference 5.
• KCSWDM Reference 5, Wetland Hydrology Protection Guidelines, mandates that a wetland may not be
structurally or hydrologically engineered for runoff quantity or quality control in Category 2 wetlands.
(We have attached the Wetland Hydrology Protection Guidelines.)
Relief Requested
• Applicant should comply with the Wetland Hydrology Protection Guidelines.
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Wetland hydrology
• Protection guidelines.F
Traffic
Problems
• Applicant's expert has testified that the level of service on the roads surrounding the proposed
development will be acceptable per the applicable city and state laws.
• However, that analysis did not address the impact of converting SE 18th Street and 124th Place SE
from quiet Cul-De-Sacs into arterials for the traffic from almost 100 new homes (over 1,000 vehicles
per day- mostly on SE 18th Street- by Applicant's own estimates).
• Realtors know that the difference in value between a house on a busy street and a house on a Cul-De-
Sac is significant.
TPWAG Request for Reconsideration Page 16 of 20
o "Usually the differ. .: in pricing is someplace between 6% 16% depending on what type of
traffic is traveling on your busy street and at what times."
(http://www.realestateabc.com/homeguide/selling-busy-street.htm)
o "For instance, you may have a stellar home, but if it's on a busy street, its value will
undoubtedly be less than a comparable home on a road less traveled. Potential rezoning of
adjacent areas also can affect comps: If that lovely forest behind your home is due to become a
sea of condominiums, your home's value is likely to be less than a similar home that will retain
its forest view." (http://www.realtor.com/home-values/HomeValuesFag.aspx)
o "Nevertheless, the single obstacle to getting anyone interested in our home is the close
proximity to the access road. ... It needs to be priced alot less than the comps. ... around here it
seems a house siding a busy street sells for 10-15% less than the same house inside the
subdivision." (http://www.zillow.com/advice-thread/Tips-Suggestions-to-Sell-House-Near-Busy-
Street/17954/)
o "How much do you think the street knocks off the price tag? ... I'd say 10-25%, depending on
the street." (http:Hforums.redfin.com/t5/Seattle/Selling-House-on-Busy-Street/td-p/53731)
• Applicant also seems to be well aware of this fact. The planned development contains not one, but
two Cul-De-Sacs (instead of building adequate roads to carry traffic in and out)!
• We respect Applicant's right to develop their property, but we expect them to respect the property
rights of the surrounding community. We believe that Applicant is maximizing their profit by unfairly
externalizing their costs to the neighboring property owners.
• With this proposed development, we estimate that Applicant will effectively be taking$1,560,000 from
surrounding property owners without compensation. We ask the City of Renton to intervene to ensure
equal protection under the law.
o Based on City of Renton Plat maps.
o Based on Zillow.com for typical property values of$300k.
0 14 houses along SE 18th Street with severe 15% impact.
0 4 houses along 124th Place SE with severe 15% impact.
o Another 50 houses on surrounding roads with 5% impact.
o Thus, 18 property owners lose an estimated $45,000 each and 50 property owners lose an
estimated $15,000 each.
o Meanwhile Applicant's preliminary plat map shows that they intend to build 26 houses along
their Cul-De-Sacs, giving an estimated 26 * $45,000 =$1,170,000 in additional profit for
Applicant.
Relief Requested
• Consider substantially reducing the number of allowable houses in the proposed development.
• Consider requiring at least one more access road to the proposed development (even if Applicant has
to buy existing houses to replace with roads).
• Consider removing speed bumps that are blocking arterial streets to the South (especially 126th
Avenue SE, SE 164th Street, and SE 160th Street). This will provide less incentive for drivers from the
proposed development to avoid the back entrance (i.e., 124th Place SE) and for drivers coming from
Fairwood to use Pierce Ave SE and SE 16th Street.
• Consider street modifications to encourage traffic to use Royal Hills Drive SE instead of SE 16th Street.
Royal Hills Drive SE is currently a bus snow route. It is a wide road, it has a gentle incline, it has good
sight distance, and it is sanded when icy, so it is much better suited for the heavy volume of traffic than
is SE 16th Street.
TPWAG Request for Reconsideration Page 17 of 20
1. Re-open the end of Beat . Way SE to Puget Drive SE.
2. Close the intersection at SE16th Street and Edmonds Avenue SE. Local traffic will be able to use the
newly opened Beacon Way SE, and traffic from Edmonds Way SE will no longer have to fight arterial
traffic to leave their neighborhood.
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TPWAG Request for Reconsideration Page 18 of 20
Environmental Impact 5tatemed
Problems
• An environmental impact statement is justified and must be prepared whenever significant adverse
impacts on the environment are probable, not just when they are inevitable. If an environmental
statement is required by the weight of the evidence and if the responsible city authority does not
require an environmental impact statement then the decision is clearly erroneous.
• The problems raised in this request for reconsideration, together with the issues raised at the appeal
hearing, coupled with Applicant's refusal to provide full documentation of environmental conditions
at the site and the full extent of structural retaining walls at the site, and the piecemeal manner in
which the City of Renton and the Applicant addressed problematic issues for the wetlands, detention
vault, drainage and retaining walls weigh in favor of requiring preparation of an environmental
impact statement.
Relief Requested
• The City of Renton should require an environmental impact statement for the project.
Respectfully submitted by Tiffany Park Woods Advocacy Group with the hope that you reconsider our
issues.
Thank you.
qko1
RENATE BEEDON
President
cc:
Rocale Timmons mailto:RTimmons@Rentonwa.gov
Nancy Rogers maiIto:NRogers@Cairncross.com
TPWAG Request for Reconsideration Page 19 of 20
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TPWAG Request for Reconsideration Page 20 of 20
Technical Memorandum
To: Rocale Timmons, Senior Planner
City of Renton-Current Planning
10230 hE Points Drive From: Darcey Miller,Senior Wetland Scientist
Suite 400 (425) 739-7977
Kirkland, WA 98033
Phone(425)8224446 Copies:
Fax(425)827-9577
Date: April 3, 2014
Subject: Reserve at Tiffany Park
Wetland Delineation Review
Project No.: 32385.A
This review pertains to the Preliminary Plat application for the Reserve at Tiffany Park (City of
Renton LUA13-001572) submitted by the applicant,Novastar Development,Inc., to the City of
Renton (City). The proposed Reserve at Tiffany Park is located generally to the east of Tiffany Park,
to the north of SE 158th Street, and south and west of Pierce Avenue SE. Otak has been asked by
the City of Renton (the City) to review the submitted critical areas document and to provide
comments regarding its applicability to the Renton Municipal Code (RMC), specifically, Section 4-3-
050, Critical Areas Regulations.
The following documents were reviewed in terms of compliance with the critical areas sections of
the City code:
• Vetland Determination:Reserve at Tiany Park, prepared by C. Gary Schulz, dated February 28,
2014;
• Plan set for the Reserve at Tiffany Park Preliminary Plat,prepared by Barghausen Consulting
Engineers, Inc., signed February 27,2014.
• Technical Information Report,prepared by Barghausen Consulting Engineers,Inc., dated
November 12,2013,and revised February 24,2014.
The Wetland Determination identifies three Category 2 wetlands and one Category 3 wetland on the
site,which are required to have 50-foot and 25-foot buffers,respectively. The report indicates that
wetland buffer averaging is proposed for the project site, and outlines the rationale for meeting the
requirements for buffer averaging described in the RMC.
K:\project\32300\32385:1\Reports\Critical Areas Review\femo_2014_0403.doc
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Rocale Timmons,Seniot Planner, City of Renton Page 2
Reserve at Tiffany Park Wetland Review Apri13,2014
Two Otak wetland biologists visited the site on March 17, 2014,to confirm whether the wetland
delineation was consistent with the Washington State Wetlands Identification and Delineation Manual
(Ecology 1997), as required by the RMC. An Otak biologist made an additional site visit on March
31,2014. Please note that the wetland delineation was performed in June 2013,whereas the rainfall
amount as of March 17, 2014,was approximately 5.58 inches above the normal amount for March
(National Weather Service); and on March 31,2014 was 5.85 inches above normal for March.
Comment 1 — Delineation Method
The wetland determination report cites the US Army Corps of Engineers wetland delineation
manuals (1987 and 2010 supplement) for the methodology used. However, the Washington State
Wetlands Identification and Delineation Alanzral(Ecology 1997) is required by RMC 4-3-050.M.4.a.
Recommendation: The applicant should ensure that the wetland delineation is consistent with the
methodology required by the RMC.
Comment 2—Survey Map
We have not seen a survey map showing all of the wetland flags,which is necessary for confirming
the wetland delineation. As discussed below, some wetland flags were not found in the field;
however,if we have a detailed map and some of the flags remain,all of those missing flags may not
need to be replaced.
Recommendation: The applicant should submit a map shoeing all of the surveyed wetland flags
(from June 2013 and any upcoming revisions). In addition,missing wetland flags should be replaced
as deemed necessary for Otak's confirmation of the wetland edges.
Comment 3—Wetland A
We agree with portions of Wetland A's delineated edges. However,we could not find some of the
flags (including Wetland A-1) in the southern part of the wetland. It appears that the wetland areas
extend farther out than the delineated edge, specifically near Flags A-1,A-3,A-5,and A-6. In these
areas,we observed hydrophytic vegetation (if any plants at all), hydric soils, and wetland hydrology
(mainly inundation). On March 17,2014,in some areas that appeared to be outside of the delineated
(flagged) wetland,inundation was over 1 foot deep during our site visit (see Photograph 1). We
agree that Wetland A meets the criteria outlined in the RMC for a Category 2 wetland,which is
required to have a 50-foot buffer.
Recommendation: Wetland A should be reexamined and any differing edges re-flagged during the
early growing season (before mid-May). Any changes to the wetland should be included in the
revised Wedand Determination Report and project plans.
K:\project\32300\32385:\\Reports\Critical Areas Review 1\femo_2014_0401doc
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Rocale Timmons,Senior Planner, City ofRenton Page 3
Reserve at Tiffany Park Vetland Revieav April 3,2014
Comment 4—Wetlands B and C
During our site visits, standing water extended generally 10 to 70 feet farther than the delineated
edges of Wetlands B and C. In addition,Wetlands B and C are not separated by upland area; they
appear to be part of the same wetland. On March 17, 2014,inundation ranged from several inches
to 1.5 feet deep in areas that may be outside of the delineated wetland edge. Hydrophytic vegetation
(mainly salmonberry and red alder) and hydric soils were also observed in the majority of these
areas. We agree that Wetland C meets the criteria outlined in the RMC for a Category 2 wetland,
which is required to have a 50-foot buffer;however, because Wetlands B and C are connected (one
wetland),the area flagged as Wetland B would also be considered a Category 2.
Recommendation: Wetlands B and C should be reexamined and any differing edges re-flagged
during the early growing season (before mid-May). Confirm the rating and buffer size for Wetland
B. Any changes to the wetlands should be included in the revised Wetland Determination Report
and project plans.
Comment 5—Wetland D
We agree with the majority of the wedand flag locations on Wetland D,although the wetland
appears to extend approximately 25 feet to the south of Flags D-3 and D-4. We agree that Wetland
D meets the criteria outlined in the RMC for a Category 2 wetland.
Recommendation: The wetland should be reexamined and any differing edges re-flagged during the
early growing season (before mid-May). Any changes to the wetland should be included in the
revised Wetland Determination Report and project plans.
Comment 6—Offsite Wetland (SW side Mercer Island Pipeline ROW)
An offsite wetland adjacent to the Reserve at Tiffany Park site was observed on the southwest side
of the Mercer Island Pipeline Right-of-way (see Photograph 2). The northwest end of the wetland is
southwest of(in line with) 18`h Court SE. This linear wetland is approximately 150 to 200 feet long
and contains hydrophytic vegetation (creeping buttercup,reed canarygrass, and other grasses) and
hydric soils.`Wetland hydrology observed on March 17,2014,ranged from saturation at the surface
to saturation at 4 inches below the surface. This wetland likely meets the criteria in the RMC for a
Category 3 wetland,which is required to have a 25-foot buffer.
Recommendation: If permission is granted from the offsite landowner, the wetland should be
delineated, classified,and added to the revised Wetland Determination Report and plans. If
permission for delineation is not received, the wetland location should be estimated and shown on
the plans,along with the buffer.
K:\project\32300\32385,k\Reports\Critical.Areas Review Memo_2014_0403.doc
i
Rocale Timmons, Senior Planner, City ofRenton Page 4
Reserve at Tifany Park Wetland Review April 3, 2014
Comment 7—Offsite Wetlands (NE side Mercer Island Pipeline ROW)
Several offsite wetlands were observed on the northeast side of the Mercer Island Pipeline Right-of-
way (northeast of the gravel access road). These wetlands appear to be Category 3 wetlands;if so,
they are likely far enough away so that their 25-foot buffers do not extend onto the project site.
Recommendation: The applicant should confirm that buffers from these offsite wetlands do not
extend onto the property.
Comment 8—Wetland in Southwest Corner of Site
A wetland was observed in the southwest corner of the site,to the north of SE 18`h Street and
southeast of the adjacent development's fence. The area was dominated by salmonberrv, Himalayan
blackberry,and reed canarygrass. On March 17, 2014, hydric soils and up to 4 inches of inundation
were observed,and water was draining from the wetland onto the sidewalk along the north side of
SE 18`h Street.
Recommendation: The wetland(if it is determined to be one) should be delineated,classified,and
added to the revised Wetland Determination Report and project plans.
Comment 9—Flowpath from Wetland B
During our March 17,2014 site visit,water was observed flowing generally west out of Wedand B to
the southwest corner of the project site (see Photographs 3,4, and 5),then offsite into the Cedar
River Pipeline Right-of-way. The wetted width of the flowpath onsite on March 17`h was
approximately 3 to 6 feet, and the water depth was 1 to 3 inches.Vegetation on the edges of the
stream generally consists of upland species such as Indian plum.A defined stream channel with bed
and banks was not observed. Sorted gravels were observed in several small portions of the
flowpath;however,these gravels were generally angular and therefore have not been subject to flow
strong enough to round their edges. During our March 31,2014 site visit,no water was observed
along the flowpath that had been observed on March 17`h. Standing water was present at Wetland B
(beyond the flagged wetland edge),but no flowing surface water was observed exiting the wetland.
No streams are mapped on or adjacent to the site.The closest stream is Ginger Creek,
approximately 800 feet offsite to the west. Ginger Creek is a Class 4 tributary to the Cedar River,per
RMC Figure 4-3-050-Q4 (Streams and Lakes).
Given the above information,it is our opinion that water flows through this area only during/after
high rainfall events, drains quickly, and that the area does not meet the definition of a stream.
Recommendation: No action is necessary.
K:\project\32300\32385A\Reports\Critical Areas Reeiew tiiemo_2014_0403.doc
Rocale Timmons, SeniotPlanner, City ofRenton Page 5
Reserve at Tiffany Park Wetland Review Aprd13,2014
Comment 10—Offsite Wetland (Cedar River Pipeline ROW)
The flowpath described in Comment 9 drains into the Cedar River Pipeline ROW,to the southwest
of the southwest corner of the Tiffany Park site. Inundation was observed in the area, as well as
FAC or wetter vegetation and potentially hydric soils;therefore, the area appears to be a wetland
(see Photograph 6).
Recommendation:The wetland (if it is determined to be one) should be delineated, classified, and
added to the revised Wedand Determination Report and plans.
Comment 11—Buffer Averaging
The buffer averaging proposal in the\Vetland Determination Report has demonstrated that it meets
all of the requirements in RMC 4-3-050.M.6.f. However,revisions to wetland edges will likely
change this proposal.
Recommendation: The applicant should revise the buffer averaging proposal to be consistent with
the any necessary revisions to the wetland edges and wetland buffers onsite.
Comment 12—Temporary Buffer Impacts
Sheets 6 and 7 of the plan set (Preliminary Grading Plan) show disturbed areas in wetland buffers
that will result from grading and wall installation. These temporary buffer impacts are not discussed
in the Wetland Determination Report,nor are they shown on Figure 2 in the report.
Recommendation: The applicant should revise the wetland documentation to discuss all temporary
impacts to wetland buffers,including impacts to specific functions and how restoration will replace
those functions. A restoration planting plan for the disturbed areas should be provided as part of
60% design.
Encl. Photographs
K:\project\32300\32385. \Reports\Critical Areas Review Memo_2014_0-V)1doc
Rocale Timmons,Senior Planner, City ofRenton Page 6
Reserve at Tiany Park Wetland Reviev April 3,2014
PHOTOGRAPHS
r .
5
Photograph 1: Wetland A,near southern delineated edge (3/17/14)
f.
Photograph 2. Offsite wetland on Mercer Island Pipeline ROW, facing SE (3/17/14)
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SECTION 6.2 GENERAL REQUIREMENTS FOR WQ FACILITIES
runoff is unaffected by whether or not the runoff is detained. Therefore.facilities such as wetponds,
which are sized by a simple volume-based approach that does not route flows through a detention facility.
are the same size whether they precede or follow detention.
Note that facilities which are sized based on volume and vv-hich include routing of tlows through a
detention facility,such as the detailed sand filter method.arc significantly smaller when located
downstream of detention.even though the same volume of water is treated in either situation. This is
because the detention facility routing sequence stores peaks within the pond and releases them at a slow
rate,reducing the size of the sand filter pond subsequently needed(the volume needed to store the peaks
need not be provided again in the sand filter pond).
Flow Volume to be Treated
When water quality treatment is required pursuant to the core and special requirements of this manual, it is
intended that a minimum of'95%of the annual average runoff volume in the(8 year)time series.as
determined v`ith the KCRTS model,be treated. Designs using the WQ design flow(as discussed above)
will treat this minimum volutne.
Treatable Flows
As stated in Chapter I.only runoff Brom target pollution-generating surfaces must be treated using the
water qualit) tacility options indicated in the applicable water quality menu. These surfaces include both
pollution-generating-impervious surface and pollution-generating pervious surface. "Target"means
that portion from which runoff must he treated using a water qualit) facility as specified in Chapter I.
Pollution-generating impervious surfaces arc those impervious surfaces which are subject to vehicular
use or storage of erodible or leachable materials.wastes,or chemicals:and which receive direct rainfall or
the run-on or blow-in otrainfall. Por subdivisions.target pollution-generating impervious surfaces
typically include right-of-way improvements(roads),parking areas and driveways that are notfulls,
disperser)as specified in Section 1.2.3.2. Metal roofs are also considered to be pollution-generating-
impervious
ollution-generatingimpervious surface unless they are treated to prevent leaching. Pollution-generating-pervious surfaces
arc those non-impervious surfaces subject to use of pesticides and fertilizers, loss of soil.or the use or
storage of erodible or leachable materials,wastes,or chemicals. For subdivisions.target pollution-
generating pervious surfaces typically include lawns and landscaped areas that are not firllv dispenser)
and from which there will not be a concentrated surface discharge in a natural channel or man-made
cote eyance system from the site.
The tbllowin_points summarize v,ihich site tlows must be treated and under what circumstances:
• All runoff Brom target pollution-generating inipervious surfaces is to be treated through the water
quality facility or facilities required in Chapter I and specified in the Chapter 6 menus.
• Runotf ti-om lawns and landscaped areas generalI}oyerflo"s toward street drainage systems where it
is comeyed to treatment facilities along with the road runoff. However.sometimes runoff fi-om
backyards drains into open space or buffer areas. In these cases,buffers may be used to provide the
requisite water qualit} treatment provided(I)runoff sheet flows into the buffer or a dispersal trench is
provided to disperse flows broadly into the buffer,and(2)the flow path through the pollution-
generating area is limited to about 200 feet.
• Drainage from impervious SUrfaces that are not pollution-generating(such as most roots)or are not
target pollution-generating surfaces may bypass the treatment facility.11 Roof rtmoff is, however.
still subject to t1mx control per Core Requirement 43. Note that metal roofs are considered pollution-
generating unless they are treated to present leaching.
Available data on the quality of roof runoff was examined. Although there are instances of polluted roof runoff,they tend to be
related to galvanized roofing materials or industrial processes. There is also data that suggests the pollutant concentration of
atmospheric fallout decreases with vertical elevation. See"Water Quality Thresholds Decision Paper,"April 1994..King County
Surface Water Management Division(now Water and Land Resources Division).
1/912009 2009 Surface Water Design Manual
6-18
d
SECTION 12 CORE REQUIREMENTS
TABLE 1.2.3.A
SUMMARY'OF FLOW CONTROL PERFORMANCE CRITERIA ACCEPTABLE FOR IMPACT MITIGATION"
IDENTIFIED PROBLEM AREA-SPECIFIC FLOW CONTROL FACILITY REQUIREMENT
DOWNSTREAM Basic Flow Control(FC)Areas Conservation FC Areas Flood Problem FC Areas
No Problem Identified Apply the Level 1 flow control Apply the historic site Apply the existing or historic
Apply the minimum area- standard,which matches existing conditions Level 2 flow control site conditions Level 2 flow
specific flow control site conditions 2-and 10-year standard,which matches control standard(whichever is
performance criteria. peaks historic durations for 50%of 2- appropriate based on
yr through 50-year peaks AND downstream flow control area)
matches historic 2-and 10- AND match existing site
year peaks conditions 100-year peaks
Type 1 Drainage Problem Additional Flow Control No additional flow control or No additional flow control or
Conveyance System Hold 10-year peak to overflow T, other mitigation is needed other mitigation is needed
Nuisance Problem peak(2)(3)
Type 2 Drainage Problem Additional Flow Control No additional flow control is No additional flow control is
Severe Erosion Apply the existing site conditions needed,but other mitigation needed,but other mitigation
Problem Level 2 flow control standard(')(') may be required4) may be required)
Type 3 Drainage Problem Additional Flow Control Additional Flow Control Additional Flow Control
Severe Flooding Apply the existing site conditions Apply the historic site If flooding is from a closed
Problem Level 3 flow control standard to conditions Level 3 flow control depression,make design
peak flows above the overflow T standard. If flooding is from a adjustments as needed to
peak. If flooding is from a closed closed depression,make meet the"special provision for
depression,make design design adjustments as needed closed depressions" 3 s
adjustments as needed to meet the to meet the"special provision
"special provision for closed for closed depressions"(3)r5)
depressions"tags)
Potential Impact to Additional Flow Control Additional Flow Control Additional Flow Control
Wetland Hydrology as DDES may require design DDES may require design DDES may require design
Determined through a adjustments per the wetland adjustments per the wetland adjustments per the wetland
Critical Area Review per hydrology protection guidelines in hydrology protection guidelines hydrology protection guide-
KCC 21A.24.100 Reference Section 5 in Reference Section 5 lines in Reference Section 5
Notes
More than one set of problem-specific performance criteria may apply if two or more downstream drainage problems are
identified through offsite analysis per Core Requirement#2. If this happens,the performance goals of each applicable
problem-specific criteria must be met. This can require extensive,time-consuming analysis to implement multiple sets of
outflow performance criteria if additional onsite flow control is the only viable option for mitigating impacts to these problems.
In these cases,it may be easier and more prudent to implement the historic site conditions Level 3 flow control standard in
place of the otherwise required area-specific standard. Use of the historic Level 3 flow control standard satisfies the specified
performance criteria for all the area-specific and problem-specific requirements except if adjustments are required per the
special provision for closed depressions described below in Note 5.
z Overflow T,is the return period of conveyance system overflow. To determine T requires a minimum Level 2 downstream
analysis as detailed in Section 2.3.1.1. To avoid this analysis.a T,of 2 years may be assumed.
3 Offsite improvements may be implemented in lieu of or in combination with additional flow control as allowed in Section 1.2.2.2
(p. 1-28)and detailed in Section 3.3.5.
(4) A tightline system may be required regardless of the flow control standard being applied if needed to meet the discharge
requirements of Core Requirement#1 (p. 1-21)or the outfall requirements of Core Requirement#4(p. 1-54),or if deemed
necessary by DDES where the risk of severe damage is high.
st Special Provision for Closed Depressions with a Severe Flooding Problem:
IF the proposed project discharges by overland flow or conveyance system to a closed depression experiencing a severe
flooding problem AND the amount of new impervious surface area proposed by the project is greater than or equal to 10%
of the 100-year water surface area of the closed depression,THEN use the"point of compliance analysis technique"
described in Section 3.3.6 to verify that water surface levels are not increasing for the return frequencies at which flooding
occurs,up to and including the 100-year frequency. If necessary,iteratively adjust onsite flow control performance to prevent
increases. Note.The point of compliance analysis relies on certain field measurements taken directly at the closed
depression(e.g.,soils tests,topography etc.). If permission to enter private property for such measurements is denied,
DDES may waive this provision and apply the existing site conditions Level 3 flow control standard with a mandatory 20%
safety factor on the storage volume.
1/9!2009 2009 Surface Water Desien Manual
1-36
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
KING COUNTY,WASHINGTON
SURFACE WATER DESIGN MANUAL
REFERENCE 5
WETLAND HYDROLOGY PROTECTION
GUIDELINES
DOE GUIDE SHEET 1B: STORMWATER
WETLAND ASSESSMENT CRITERIA
DOE GUIDE SHEET 2B: GUIDELINES FOR
PROTECTION FROM ADVERSE IMPACTS
OF MODIFIED RUNOFF QUANTITY
DISCHARGED TO WETLANDS
2009 Surface Water Design Manual 1/9/2009
E
Guide Sheet 1B: Stormwater Wetland Assessment Criteria
Excerpted from 2005 DOE Stormwater Manual for Western Washington
This guide sheet gives criteria that disqualify a natural wetland from being structurally or
hydrologically engineered for control of stormwater quantity, quality, or both. These
criteria should be applied only after performing the alternatives analysis outlined in
Guide Sheet IA.
1. A wetland should not be structurally or hydrologically engineered for runoff quantity
or quality control and should be given maximum protection from overall urban
impacts (see Guide Sheet 2, Wetland Protection Guidelines) under any of the
following circumstances:
• In its present state it is primarily an estuarine or forested wetland or a
priority peat system.
• It is a rare or irreplaceable wetland type, as identified by the Washington
Natural Heritage Program, the Puget Sound Water Quality Preservation
Program, or local government.
• It provides rare, threatened, or endangered species habitat that could be
impaired by the proposed action. Determining whether or not the
conserved species will be affected by the proposed project requires a
careful analysis of its requirements in relation to the anticipated habitat
changes.
• It provides a high level of many functions.
In general, the wetlands in these groups are classified in Categories I and 11 in the
"Washington State Wetland Rating System of Western Washington."That publication is
available on-line at httpaiwww.ecv.«�a.gov/biblio/sea.htmles.
2. A wetland can be considered for structural or hydrological modification for runoff
quantity or quality control if most of the following circumstances exist:
• It is classified in Category IV in the"Washington State Wetland Rating
System of Western Washington". In general, Category IV wetlands have
monotypic vegetation of similar age and class, lack special habitat
features, and are isolated from other aquatic systems. Any functions lost
through hydrologic or structural modification in a Category IV wetland
would have to be compensated/replaced.
• The wetland has been previously disturbed by human activity, as
evidenced by agriculture, fill. ditching, and/or introduced or invasive
weedy plant species.
s
• The wetland has been deprived of a significant amount of its water supply
by draining or previous urbanization (e. g.,by loss of groundwater
supply), and stormwater runoff is sufficient to augment the water supply.
A particular candidate is a wetland that has experienced an increased
summer dry period, especially if the drought has been extended by more
than two weeks.
• Construction for structural or hydrologic modification in order to provide
runoff quantity or quality control will disturb relatively little of the
wetland.
• The wetland can provide the required storage capacity for quantity or
quality control through an outlet orifice modification to increase storage of
water. rather than through raising the existing overflow. Orifice
modification is likely to require less construction activity and consequent
negative impacts.
• Under existing conditions the wetland's experiences a relatively high
degree of water level fluctuation and a range of velocities(i.e., a wetland
associated with substantially flowing water, rather than one in the
headwaters or entirely isolated from flowing water).
• The wetland does not exhibit any of the following features:
- Significant priority peat system or forested zones that will
experience substantially altered hydroperiod as a result of the
proposed action;
- Regionally unusual biological community types,
- Animal habitat features of relatively high value in the region (e.g.,
a protected, undisturbed area connected through undisturbed
corridors to other valuable habitats, an important breeding site for
protected species);
- The presence of protected commercial or sport fish:
- Configuration and topography that will require significant
modification that may threaten fish stranding;
- A relatively high degree of public interest as a result of, for
example, offering valued local open space or educational,
scientific, or recreational opportunities, unless the proposed action
would enhance these opportunities;
• The wetland is threatened by potential impacts exclusive of stormwater
management, and could receive greater protection if acquired for a
stormwater management project rather than lett in existing ownership.
• There is good evidence that the wetland actually can be restored or
enhanced to perform other functions in addition to runoff quantity or
quality control.
• There is good evidence that the wetland lends itself to the effective
application of the Wetland Protection Guidelines in Guide Sheet 2.
• The wetland lies in the natural routing of the runoff. Local regulations
often prohibit drainage diversion from one basin to another.
• The wetland allows runoff discharge at the natural location.
(
Guide Sheet 213: Guidelines for Protection from Adverse
Impacts of Modified Runoff Quantity Discharged to Wetlands
Excerpted from 2001 DOE Stormwater Manual for Western Washington
1. Protection of wetland plant and animal communities depends on controlling the
wetland's hydroperiod, meaning the pattern of fluctuation of water depth and the
frequency and duration of exceeding certain levels, including the length and onset of
drying in the summer. A hydrologic assessment is useful to measure or estimate elements
of the hydroperiod under existing pre-development and anticipated postdevelopment
conditions. This assessment should be performed with the aid of a qualified hydrologist.
Post-development estimates of watershed hydrology and wetland hydroperiod must
include the cumulative effect of all anticipated watershed and wetland modifications.
Provisions in these guidelines pertain to the full anticipated build-out of the wetland's
watershed.
This analysis hypothesizes a fluctuating water stage over time before development that
could fluctuate more, both higher and lower after development; these greater fluctuations
are termed stage excursions. The guidelines set limits on the frequency and duration of
excursions, as well as on overall water level fluctuation, after development. To determine
existing hydroperiod use one of the following methods, listed in order of preference:
• Estimation by a continuous simulation computer model—
The model should be calibrated with at least one year of data taken using a
continuously recording level gage under existing conditions and should be run for
the historical rainfall period. The resulting data can be used to express the
magnitudes of depth fluctuation, as well as the frequencies and durations of
surpassing given depths. [Note: Modeling that yields high quality information of
the type needed for wetland hydroperiod analysis is a complex subject. Providing
guidance on selecting and applying modeling options is beyond the scope of these
guidelines but is being developed by King County Surface Water Management
Division and other local jurisdictions. An alternative possibility to
modeling depths, frequencies, and durations within the wetland is to model
durations above given discharge levels entering the wetland over various time
periods (e. g., seasonal, monthly, weekly). This option requires further
development.]
• Measurement during a series of time intervals (no longer than one month in
length)over a period of at least one year of the maximum water stage, using a
crest stage gage, and instantaneous water stage, using a staff gage--The resulting
data can be used to express water level fluctuation (WLF) during the interval as
follows:
Average base stage=(instantaneous stage at beginning of interval +
Instantaneous stage at end of interval)/2
WLF =Crest stage- Average base stage
4 �
Compute mean annual and mean monthly VLF as the arithmetic averages for each
year and month for which data are available.
To forecast future hydroperiod use one of the following methods, listed in order of
preference:
• Estimation by the continuous simulation computer model calibrated during pre-
development analysis and run for the historical rainfall period—
The resulting data can be used to express the magnitudes of depth fluctuation, as
well as the frequencies and durations of surpassing given depths. [Note: Post-
development modeling results should generally be compared with
predevelopment modeling results, rather than directly with field measurements,
because different sets of assumptions underlie modeling and monitoring. Making
pre-and post-development comparisons on the basis of common assumptions
allows cancellation of errors inherent in the assumptions.]
• Estimation according to general relationships developed from the Puget Sound
Wetlands and Stormwater Management Program Research Program, as follows
(in part adapted from Chin 1996):
-Mean annual WLF is very likely (100% of cases measured)to be <20
cm (8 inches or 0.7 ft) if total impervious area (TIA)cover in the
watershed is<6%(roughly corresponding to no more than 15% of the
watershed converted to urban land use).
-Mean annual WLF is very likely (89%of cases measured)to be> 20 cm
if TIA in the watershed is> 211% (roughly corresponding to more than
30% of the watershed converted to urban land use).
-Mean annual WLF is somewhat likely (50% of cases measured)to be>
30 cm (1.0 ft) if TIA in the watershed is> 21%(roughly corresponding to
more than 30% of the watershed converted to urban land use).
-Mean annual WLF is likely (75%of cases measured)to be> 30 em, and
somewhat likely (50%of cases measured)to be 50 cm (20 inches or 1.6 ft)
or higher, if TIA in the watershed is>40%(roughly corresponding to
more than 70%of the watershed converted to urban land use).
-The frequency of stage excursions greater than 15 cm (6 inches or 0.5 ft)
above or below pre-development levels is somewhat likely(54%of cases
measured)to be more than six per year if the mean annual WLF increases
to> 24 cm (9.5 inches or 0.8 ft).
—The average duration of stage excursions greater than 15 cm above or
below pre-development levels is likely(69%of cases measured)to be
more than 72 hours if the mean annual WLF increases to>20 cm.
2. The following hydroperiod limits characterize wetlands with relatively high vegetation
species richness and apply to all zones within all wetlands over the entire year. If these
limits are exceeded,then species richness is likely to decline. If the analysis described
above forecasts exceedences, one or more of the management strategies listed in step 5
should be employed to attempt to stay within the limits.
• Mean annual WLF (and mean monthly WLF for every month of the year)does
not exceed 20 cm. Vegetation species richness decrease is likely with: (i)a mean
annual (and mean monthly) WLF increase of more than 5 cm (2 inches or 0.16 ft)
if predevelopment mean annual (and rnean monthly) WLF is greater than 15 cm,
or(2) a mean annual (and mean monthly) WLF increase to 20 cm or more if pre-
development mean annual (and mean monthly) WLF is 15 cm or less.
• The frequency of stage excursions of 15 cm above or below predevelopment stage
does not exceed an annual average of six.Note: A short-term lagging or
advancement of the continuous record of water levels is acceptable. The 15 cm
limit applies to the temporary increase in maximum water surface elevations
(hydrograph peaks)after storm events and the maximum decrease in water
surface elevations (hydrograph valley bottoms)between events and during the dry
season.
• The duration of stage excursions of 15 cm above or below predevelopment stage
does not exceed 72 hours per excursion.
• The total dry period (when pools dry down to the soil surface everywhere in the
wetland)does not increase or decrease by more than two weeks in any year.
• Alterations to watershed and wetland hydrology that may cause perennial
wetlands to become vernal are avoided.
I The following hydroperiod limit characterizes priority peat wetlands(bogs and fens
as more specifically defined by the Washington Department of Ecology)and applies to
all zones over the entire year. If this limit is exceeded, then characteristic bog or fen
wetland vegetation is likely to decline. if the analysis described above forecasts
exceedence, one or more of the management strategies listed in step 5 should be
employed to attempt to stay within the limit.
• The duration of stage excursions above the predevelopment stage does not exceed
24 hours in any year.
• Note: To apply this guideline a continuous simulation computer model needs to
be employed. The model should be calibrated with data taken under existing
conditions at the wetland being analyzed and then used to forecast post-
development duration of excursions.
4. The following hydroperiod limits characterize wetlands inhabited by breeding native
amphibians and apply to breeding zones during the period 1 February through 31 May. If
these limits are exceeded,then amphibian breeding success is likely to decline. If the
analysis described above forecasts exceedences, one or more of the management
strategies listed in step 5 should be employed to attempt to stay within the limits.
• The magnitude of stage excursions above or below the pre-development stage
does not exceed 8 cm, and the total duration of these excursions does not exceed
24 hours in any 30 day period.
• Note: To apply this guideline a continuous simulation computer model needs to
be employed. The model should be calibrated with data taken under existing
conditions at the wetland being analyzed and then used to forecast post-
development magnitude and duration of excursions.
5. If it is expected that the hydroperiod limits stated above could be exceeded, consider
strategies such as:
• Reduction of the level of development;
• Increasing runoff infiltration [Note: Infiltration is prone to failure in many Puget
Sound Basin locations with glacial till soils and generally requires pretreatment
to avoid clogging. In other situations infiltrating urban runoff may contaminate
groundwater. Consult the stormwater management manual adopted by the
jurisdiction and carefully analyze infiltration according to its prescriptions.]:
• Increasing runoff storage capacity, and
• Selective runoff bypass.
6. After development, monitor hydroperiod with a continuously recording level gauge or
staff and crest stage gauges. If the applicable limits are exceeded, consider additional
applications of the strategies in step 5 that may still be available. It is also recommended
that goals be established to maintain key vegetation species, amphibians, or both, and that
these species be monitored to determine if the goals are being met.