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Western Washington Division Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd, Cle Elum, WA 98922
Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419
www.EncompassES.net
PRELIMINARY TECHNICAL INFORMATION REPORT
For
Lincoln Peak Short Plat
3601 Lincoln Ave NE
Renton, WA 98056
April 22nd, 2026
Prepared by:
Gabe Garner
Encompass Engineering Job No. 25560
Prepared For:
Geoff Sherwin
Trumark Homes Washington, LLC
PO Box 100
Sumner, WA 98390
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | i
Table of Contents
List of Figures ................................................................................................................................... i
I. PROJECT OVERVIEW ................................................................................................................ 1
II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 7
III. DOWNSTREAM ANALYSIS ...................................................................................................... 12
IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN ........................... 17
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 20
VII. OTHER PERMITS ..................................................................................................................... 20
VIII. CSWPP ANALYSIS AND DESIGN .............................................................................................. 20
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT .................. 20
X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 20
List of Figures
Figure 1 – TIR Worksheet
Figure 2 – Vicinity Map
Figure 3 – Soils Map and Legend
Figure 4 – Existing Conditions Map
Figure 5 – Developed Conditions Map
Figure 6 – Drainage Review Flow Chart
Figure 7 – Downstream Map
Appendix A
Geotechnical Report by Terra Associates, Inc. dated July 23, 2025
Appendix B
Wetland and Stream Reconnaissance by Wetland Resources, Inc. dated January 30, 2026
Appendix C
Preliminary Tree Protection Plan by Washington Forestry Consultants, Inc. dated April 17, 2026
Appendix D
WWHM Output
CITY OF RENTON SURFACE WATER DESIGN MANUAL
2022 City of Renton Surface Water Design Manual 6/22/2022
8-A-1
REFERENCE 8-A
TECHNICAL INFORMATION REPORT (TIR)
WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner _____________________________
Phone ___________________________________
Address __________________________________
_________________________________________
Project Engineer ___________________________
Company _________________________________
Phone ___________________________________
Project Name __________________________
CED Permit # ________________________
Location Township ________________
Range __________________
Section _________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Land Use (e.g., Subdivision / Short Subd.)
Building (e.g., M/F / Commercial / SFR)
Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline
Management
Structural
Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
(check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
__________________
__________________
__________________
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
__________________
__________________
__________________
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: _______________________
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: SWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: _____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-3
Part 10 SOILS
Soil Type
______________________
______________________
______________________
______________________
Slopes
________________________
________________________
________________________
________________________
Erosion Potential
_________________________
_________________________
_________________________
_________________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 9 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Standard: _______________________________
or Exemption Number: ____________
Conveyance System Spill containment located at: _____________________________
Erosion and Sediment Control /
Construction Stormwater Pollution
Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet
per Threshold Discharge Area)
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. _______________________
On-site BMPs Describe:
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: SDO / MDP / BP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): _______________
Datum:
Flood Protection Facilities Describe:
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-Use Site: Yes / No
Treatment BMP: _________________________________
Maintenance Agreement: Yes / No
with whom? _____________________________________
Other Drainage Structures
Describe:
REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
2022 City of Renton Surface Water Design Manual 6/22/2022
Ref 8-A-5
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Control Pollutants
Protect Existing and Proposed
BMPs/Facilities
Maintain Protective BMPs / Manage
Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure
operation of Permanent BMPs/Facilities, restore
operation of BMPs/Facilities as necessary
Flag limits of sensitive areas and open space
preservation areas
Other _______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Description Water Quality Description On-site BMPs Description
Detention
Infiltration
Regional
Facility
Shared
Facility
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
Vegetated
Flowpath
Wetpool
Filtration
Oil Control
Spill Control
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
Full Dispersion
Full Infiltration
Limited Infiltration
Rain Gardens
Bioretention
Permeable
Pavement
Basic Dispersion
Soil Amendment
Perforated Pipe
Connection
Other
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
_____________
REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ____________________________
Cast in Place Vault
Retaining Wall
Rockery > 4′ High
Structural on Steep Slope
Other _______________________________
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were
incorporated into this worksheet and the attached Technical Information Report. To the best of my
knowledge the information provided here is accurate.
____________________________________________________________________________________
Signed/Date
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 1
I. PROJECT OVERVIEW
Project: Lincoln Peak Short Plat
Site Address: 3601 Lincoln Ave NE, Renton, WA 98056 (See Vicinity Map)
Tax Parcel: 334570-0230
Zoning District: R-8
Site Area: 48,066 SF (1.10 AC) – as surveyed
Site Location: The site is in the City of Renton within the NE quarter of Section 32,
Township 24 North, Range 5 East, W.M, King County, Washington. The
site is located on the west side of Lincoln Ave NE, at the intersection of
Lincoln Ave NE & NE 36th St.
Figure 2: Vicinity Map
Pre-developed Site Conditions:
The project site is located in the City of Renton on a 48,066 SF (1.10 AC) lot that is zoned as R-8. The
property may currently be accessed via Lincoln Ave NE in the eastern portion of the site. The site is
bordered to the north and west by single-family residential properties, to the south by an undeveloped
section of public right-of-way (ROW), and to the east by Lincoln Ave NE. The site is currently developed
with a single-family residence, detached garage, gravel driveway, and concrete driveway.
Stormwater runoff produced from the existing site sheet flows towards the natural discharge area (NDA)
located in the western portion of the site. The eastern portion of the site contains moderate slopes ranging
from 2-15%, and the western portion of the site contains steep slopes of up to 75%. The property is located
within the May Creek drainage basin, within the Cedar River/Lake Washington watershed. See the full
downstream analysis in Section III of this Technical Information Report (TIR) for more information. An
Existing Conditions Map is included as Figure 4 at the end of this Section.
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 2
Critical Areas:
According to King County iMap, City of Renton GIS Map, the Geotechnical Report by Terra Associates, Inc.
(Appendix A), and the Wetland and Stream Reconnaissance by Wetland Resources, Inc. (Appendix B), the
western portion of the site is located within an erosion hazard area as well as a landslide hazard area.
Additionally, there is a Category III wetland located approximately 100 feet south of the site, which must
honor an additional 15-foot building setback from the wetland buffer.
Soils:
Per the US Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Web Soil
Survey (WSS) information, the project site is underlain with Alderwood gravelly sandy loam & Alderwood
and Kitsap soils (See Figure 3 below). The Geotechnical Report prepared by Terra Associates, Inc.
(Appendix A) states that stormwater management at the site should not be managed with infiltration
facilities, as the soils underling the site largely consist of silty sand which exhibit low permeabilities and
would impede the downward migration of stormwater.
Figure 3: Soil Map and Legend
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 3
Developed Site Conditions
The project proposes the development of five (5) single-family lots within the 48,066 SF (1.10 AC) parcel.
Lot 1 is 7,307 SF and will be located in the northeastern portion of the site, Lot 2 is 8,387 SF and will be
located in the northwestern portion of the site, Lot 3 is 5,993 SF and will be located in the southeastern
portion of the site, Lot 4 is 6,096 SF and will be located directly west of Lot 3, and Lot 5 is 6,786 SF and will
be located in the southwestern portion of the site. A 1,421 SF private access tract (Tract A) is proposed
between Lots 4 and 5 and will provide access to Lots 2 and 5 via NE 36th Street in the southern portion the
site, a 4,358 SF critical area tract (Tract B) will be located along the western edge of the site, and a 7,719
SF ROW dedication is proposed along the southern and eastern property boundaries.
The proposed impervious surfaces associated with this short plat include a 1,421 SF asphalt access road,
4,863 SF of asphalt pavement widening, 1,648 SF of concrete sidewalk, 938 SF of concrete driveway
aprons, and 262 SF of concrete ADA ramps (for a total of 9,132 SF of impervious surfaces).
The parcel is zoned R-8, which allows for a maximum building coverage of 50% and a maximum impervious
surface coverage of 65%. For the preliminary design of the lots, the maximum impervious surface
coverage was assumed:
• Lot 1: The maximum allowable impervious surface coverage for Lot 1 is 7,307 SF * 0.65 = 4,750
SF. The final site layout of Lot 1 has not been determined at this stage; therefore, this report
assumes that the future impervious surfaces required to construct the residence on Lot 1 will use
the maximum coverage stated above (4,750 SF).
• Lot 2: The maximum allowable impervious surface coverage for Lot 2 is 8,387 SF * 0.65 = 5,452
SF. The final site layout of Lot 2 has not been determined at this stage; therefore, this report
assumes that the future impervious surfaces required to construct the residence on Lot 2 will use
the maximum coverage stated above (5,452 SF).
• Lot 3: The maximum allowable impervious surface coverage for Lot 3 is 5,993 SF * 0.65 = 3,895
SF. The final site layout of Lot 3 has not been determined at this stage; therefore, this report
assumes that the future impervious surfaces required to construct the residence on Lot 3 will use
the maximum coverage stated above (3,895 SF).
• Lot 4: The maximum allowable impervious surface coverage for Lot 4 is 6,096 SF * 0.65 = 3,962
SF. The final site layout of Lot 4 has not been determined at this stage; therefore, this report
assumes that the future impervious surfaces required to construct the residence on Lot 4 will use
the maximum coverage stated above (3,962 SF).
• Lot 5: The maximum allowable impervious surface coverage for Lot 5 is 6,786 SF * 0.65 = 4,411
SF. The final site layout of Lot 5 has not been determined at this stage; therefore, this report
assumes that the future impervious surfaces required to construct the residence on Lot 5 will use
the maximum coverage stated above (4,411 SF).
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 4
The total impervious surface area associated with the individual lots is 22,470 SF (based on the maximum
per zoning). The total impervious surface area that is being utilized in the drainage design for this project
is 31,602 SF (maximum impervious surface area for the individual lots + short plat improvements).
The proposed construction limits for this project not only include the parcel itself, but also the areas in
the ROW for both NE 36th Street and Lincoln Ave NE in which frontage improvements will be installed. In
the existing conditions, approximately 2,022 SF of area within the construction limits on the eastern side
of Lincoln Avenue NE discharges runoff to the north (due to the road being crowned). This is the only area
within the construction limits that discharges towards a separate basin than the rest of the construction
limits (these two basins do not converge within ¼ mile). In the proposed conditions, approximately 6,692
SF of area within the construction limits will be discharged to this same separate basin to the north, as
this proposed section of Lincoln Avenue NE will be graded at 2% towards the western curb line and cannot
be mitigated with the rest of the proposed surfaces due to topography/site constraints.
Therefore, stormwater runoff from the proposed development will be routed into two different basins –
Basin 1 (natural discharge area for the site) and Basin 2 (natural discharge location for the existing
pavement along the eastern side of Lincoln Avenue NE). In the existing conditions, Basin 1 is 52,011 SF
(1.194 AC) and Basin 2 is 2,022 SF (0.046 SF). In the developed conditions, Basin 1 is 47,341 SF (1.087 SF)
and Basin 2 is 6,692 SF (0.153 AC). In both the predeveloped and developed conditions, each of the two
basin areas combine to make up the total construction limits for the project of 54,033 SF (1.240 AC).
In the developed conditions, Basin 1 will include the future impervious surfaces to be constructed on Lots
1-5 (22,470 SF total based on the maximum per zoning), 1,421 SF of asphalt access road, 931 SF of concrete
sidewalk, 748 SF of concrete driveway aprons, 18,080 SF of pervious/lawn surfacing, and 3,691 SF of
asphalt pavement widening. All of the surfaces within Basin 1 will be collected and conveyed into a 25 FT
x 50 FT x 12 FT deep detention vault located to the south of the site within the public ROW for NE 36th
Street. This detention vault will discharge stormwater into an existing storm pipe which routes runoff
towards May Creek.
In the developed conditions, Basin 2 will include 1,172 SF of asphalt pavement widening, 3,276 SF of
existing pavement (in which a grind & overlay will be performed on), 190 SF of concrete driveway aprons,
979 SF of concrete sidewalk, and 1,075 SF of pervious/lawn surfacing. All of the surfaces within Basin 2
will be collected and conveyed into the existing storm system within Lincoln Ave NE which routes runoff
in the northern direction (separate discharge area from Basin 1).
Please refer to Core Requirement #9 in Section II and Section IV of this TIR for additional discussion on
stormwater BMPs and flow control. A Developed Conditions Map is provided as Figure 5 at this end of this
Section.
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ON-SITE IMPERVIOUS AREAS:
OFF-SITE IMPERVIOUS AREAS:
TOTAL IMPERVIOUS AREAS: 13,440 SF
NE 36TH ST
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ON-SITE IMPERVIOUS AREAS:
OFF-SITE IMPERVIOUS AREAS:
TOTAL IMPERVIOUS AREAS: 9,132 SF
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 7
II. CONDITIONS AND REQUIREMENTS SUMMARY
The 2022 City of Renton Surface Water Design Manual (RSWDM) was utilized to determine and address
all core and special requirements. Based on the criteria specified in Figure 1.1.2.A of the RSWDM, the
project falls under Full Drainage Review. Per Section 1.1.2.4 of the RSWDM, the project must meet all nine
(9) core and all six (6) special requirements. See Figure 6 below for more information on how the type of
drainage review was determined.
Figure 6: Drainage Review Flow Chart
Lincoln Peak Short Plat Preliminary Technical Information Report
04/22/2026 P a g e | 8
Core Requirements
Core Requirement #1: Discharge at the Natural Location
This project proposes a detention vault (for Basin 1) that will discharge runoff to the west where
it eventually converges with May Creek, just as in the existing conditions. Runoff from Basin 2 will
be collected and conveyed into the existing storm system within Lincoln Avenue NE which routes
runoff in the northern direction (separate discharge area from Basin 1). As this project will be
directing more runoff towards Basin 2 in the developed conditions than in the existing conditions
(6,692 SF vs. 2,022 SF), a drainage adjustment application regarding Core Requirement #1 has
been prepared and is included in the submittal package. Please refer to the full Downstream
Analysis provided in Section III of this TIR.
Core Requirement #2: Downstream Analysis
A Level 1 Downstream analysis has been completed for the site and no existing or potential
problems have been identified. This analysis is included in Section III of this TIR.
Core Requirement #3: Flow Control Facilities
Based on the City of Renton’s flow control application map, the project site is located within the
Duration Flow Control Standard (Forested Conditions). Flow control facilities are required to
match the developed peak discharge rates to historical (forested) site conditions over the range
of flows extending form 50% of the 2-year up to the full 50-year flow and match the peaks for the
2- and 10-year return periods.
A 25 FT x 50 FT x 12 FT deep detention vault is proposed the meet stormwater requirements for
Basin 1. This stormwater facility will be located to the south of the site within the public ROW for
NE 36th Street.
Stormwater runoff from Basin 2 will be collected and conveyed into the existing storm system
within Lincoln Ave NE which routes runoff in the northern direction (separate discharge area from
Basin 1). This basin is exempt from flow control, as the proposed surfaces in this area result in a
0.0905 CFS increase in the 100-year flow using 15-minute time steps, which is below the
exemption threshold of 0.15 CFS. No flow control facilities are proposed at this time for Basin 2;
however, flow control BMPs have been analyzed as described under Core Requirement #9. Please
refer to Appendix D for a copy of the full WWHM data output. See Chapter IV of this TIR for
additional discussion
Core Requirement #4: Conveyance System
Conveyance in compliance with the requirements detailed in Section 1.2.4.1 of the City of Renton
2022 SWDM is provided in Section V of this report.
Core Requirement #5: Construction Stormwater Pollution Prevention
A temporary erosion and sediment control (TESC) plan providing details on best management
practices (BMPs) to be implemented during construction is included in the engineering plan set.
A Construction Stormwater Pollution Prevention Plan (CSWPPP) will be provided with final
engineering. Please refer to Section VIII of this TIR for additional discussion.
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Core Requirement #6: Maintenance and Operations
An Operation and Maintenance Manual will be provided with final engineering.
Core Requirement #7: Financial Guarantees and Liability
The owner will arrange for any financial guarantees and liabilities required by the permit.
Core Requirement #8: Water Quality Facilities
In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is required
for this project as new plus replaced pollution generating impervious surfaces (PGIS) exceed 5,000
SF. To address water quality requirements, a Contech StormFilter catch basin is proposed post-
detention for Basin 1.
Core Requirement #9: Flow Control BMPs
This project is classified as a small subdivision; therefore, it is subject to the Small Subdivision
Project BMP Requirements detailed in Section 1.2.9.3.1 in the RSWDM (both Basin 1 and Basin 2
have been analyzed separately). Although implementation of individual lot BMPs is not required
until building permit application, BMPs have been considered for the future improvements on
Lots 1-5 based on Section 1.2.9.2.1 of the RSWDM. See Section IV of this TIR for further discussion
and flow control analysis.
1.2.9.3.1 Small Subdivision Project BMP Requirements (Basin 1)
Full Dispersion: Infeasible. A 100-foot native vegetated flowpath segment is not available on-site
for the 6,791 SF of impervious surfaces to be constructed within Basin 1 of the short plat (out of
9,132 SF total short plat improvements associated with the entire project).
Full Infiltration / Bioretention / Limited Infiltration / Permeable Pavement: Infeasible. The
Geotechnical Report prepared by Terra Associates, Inc. (Appendix A) states that stormwater
management at the site should not be managed with infiltration facilities, as the soils underling
the site largely consist of silty sand which exhibit low permeabilities and would impede the
downward migration of stormwater.
Basic Dispersion: Infeasible. A 25-foot vegetated flowpath is not available on-site for the 6,791 SF
of impervious surfaces to be constructed within Basin 1 of the short plat (out of 9,132 SF total
short plat improvements associated with the entire project).
Soil Moisture Holding Capacity: The soil moisture holding capacity of new pervious surfaces must
be protected in accordance with KCC 16.82.100 (F) and (G). KCC 16.82.100(F) requires that the
duff layer or native topsoil be retained to the maximum extent practicable. KCC 16.82.100(G)
requires soil amendment to mitigate for lost moisture holding capacity where compaction or
removal of some or all of the duff layer or underlying topsoil has occurred. The amendment must
be such that the replaced topsoil is a minimum of 8 inches thick, unless the applicant
demonstrates that a different thickness will provide conditions equivalent to the soil moisture
holding capacity native to the site. The replaced topsoil must have an organic content of 5-10%
dry weight and a pH suitable for the proposed surface vegetation (for most soils in King County, 4
inches of well-rotted compost tilled into the top 8 inches of soil is sufficient to achieve the organic
content standard.) The amendment must take place between May 1 and October 1.
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As no BMPs are feasible for the mitigation of the 6,791 SF of impervious surfaces to be constructed
within Basin 1 of the short plat (out of 9,132 SF total short plat improvements associated with the
entire project), stormwater runoff will be collected and conveyed into a 25 FT x 50 FT x 12 FT deep
detention vault located to the south of the site within the public ROW for NE 36th Street (this vault
will also be responsible for mitigating the 22,470 SF of maximum impervious per zoning on the
individual lots). This detention vault will discharge stormwater into an existing storm pipe which
routes runoff towards May Creek. A Developed Conditions Map is provided as Figure 5 of this
report.
1.2.9.3.1 Small Subdivision Project BMP Requirements (Basin 2)
Full Dispersion: Infeasible. A 100-foot native vegetated flowpath segment is not available on-site
for the 2,341 SF of impervious surfaces to be constructed within Basin 2 of the short plat (out of
9,132 SF total short plat improvements associated with the entire project).
Full Infiltration / Bioretention / Limited Infiltration / Permeable Pavement: Infeasible. The
Geotechnical Report prepared by Terra Associates, Inc. (Appendix A) states that stormwater
management at the site should not be managed with infiltration facilities, as the soils underling
the site largely consist of silty sand which exhibit low permeabilities and would impede the
downward migration of stormwater.
Basic Dispersion: Infeasible. A 25-foot vegetated flowpath is not available on-site for the 2,341 SF
of impervious surfaces to be constructed within Basin 2 of the short plat (out of 9,132 SF total
short plat improvements associated with the entire project).
Soil Moisture Holding Capacity: The soil moisture holding capacity of new pervious surfaces must
be protected in accordance with KCC 16.82.100 (F) and (G). KCC 16.82.100(F) requires that the
duff layer or native topsoil be retained to the maximum extent practicable. KCC 16.82.100(G)
requires soil amendment to mitigate for lost moisture holding capacity where compaction or
removal of some or all of the duff layer or underlying topsoil has occurred. The amendment must
be such that the replaced topsoil is a minimum of 8 inches thick, unless the applicant
demonstrates that a different thickness will provide conditions equivalent to the soil moisture
holding capacity native to the site. The replaced topsoil must have an organic content of 5-10%
dry weight and a pH suitable for the proposed surface vegetation (for most soils in King County, 4
inches of well-rotted compost tilled into the top 8 inches of soil is sufficient to achieve the organic
content standard.) The amendment must take place between May 1 and October 1.
As no BMPs are feasible for the mitigation of the 2,341 SF of impervious surfaces to be constructed
within Basin 2 of the short plat (out of 9,132 SF total short plat improvements associated with the
entire project), stormwater runoff will be collected and conveyed into the existing storm system
within Lincoln Ave NE which routes runoff in the northern direction (separate discharge area from
Basin 1). A Developed Conditions Map is provided as Figure 5 of this report.
1.2.9.2.1 Small Lot BMP Requirements
For the design of Lots 1-5, the maximum impervious surface coverage was assumed while
evaluating future stormwater BMPs. Their final location and design shall be determined under the
single-family building permit process.
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Full Dispersion: Infeasible. A 100-foot native vegetated flowpath segment is not available on any
of the proposed lots.
Full Infiltration / Bioretention / Limited Infiltration / Permeable Pavement: Infeasible. The
Geotechnical Report prepared by Terra Associates, Inc. (Appendix A) states that stormwater
management at the site should not be managed with infiltration facilities, as the soils underling
the site largely consist of silty sand which exhibit low permeabilities and would impede the
downward migration of stormwater.
Basic Dispersion: Basic Dispersion may be feasible on the proposed lots, depending on the building
footprints/layout for the future single-family residences. Conservatively, it has been deemed
infeasible and all runoff produced from the future development of Lots 1-5 has been designed to
be directed into the proposed 25 FT x 50 FT x 12 FT deep detention vault located south of the site
within the public ROW for NE 36th Street.
As no BMPs are feasible, stormwater runoff from the maximum impervious surface area
associated with the individual lots (22,470 SF – based on the maximum per zoning) will be
collected and conveyed into a 25 FT x 50 FT x 12 FT deep detention vault located to the south of
the site within the public ROW for NE 36th Street. This detention vault will discharge stormwater
into an existing storm pipe which routes runoff towards May Creek. A Developed Conditions Map
is provided as Figure 5 of this report.
Special Requirements
Special Requirement #1: Other Adopted Area-Specific Requirements
Critical Drainage Area – N/A
Master Drainage Plan – N/A
Basin Plan – N/A
Lake management Plan – N/A
Shared Facility Drainage Plan – N/A
Special Requirement #2: Flood Hazard Area Delineation
The limits of this project do not lie within a delineated FEMA 100-year floodplain.
Special Requirement #3: Flood Protection Facilities
This project does not rely on or propose to modify/construct a new flood protection facility.
Special Requirement #4: Source controls
Source controls for the proposed short plat development are not applicable.
Special Requirement #5: Oil Control
This project is not considered high-use in need of oil control.
Special Requirement #6: Aquifer Protection Area
The site is not located within an Aquifer Protection Area per the Groundwater Protection Areas
Map in the RSWDM.
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III. DOWNSTREAM ANALYSIS
A Level 1 Downstream analysis has been conducted per the requirements in Section 1.2.2.1 of the
RSWDM. Please see Tasks 1 through 4 below for a summary of the results.
Task 1: Define and Map the Study Area
It should be noted that the property itself only contains one natural discharge area (NDA); however, as
the proposed construction limits for the project extend past the property boundaries and into the public
ROW, it was found that a small portion within the northeastern section of the construction limits (on
Lincoln Avenue NE) drains to a separate basin than the property itself. Therefore, this site contains two
separate drainage basins – Basin 1 and Basin 2. The area of analysis extends approximately a quarter-mile
downstream from the site. A Downstream Map is provided in Figure 7 below.
Figure 7: Downstream Map
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Task 2: Review All Available Information on the Study Area
Per King County resources, there have been no significant drainage complaints within a quarter-mile
downstream of the site.
Task 3: Field Inspect the Study Area
A field inspection was performed by Encompass Engineering & Surveying on October 3rd, 2025. Please
refer to Task 4 for a detailed description of the downstream drainage system and analysis.
Task 4: Describe the Drainage System
It should be noted that the property itself only contains one natural discharge area (NDA); however, as
the proposed construction limits for the project extend past the property boundaries and into the public
ROW, it was found that a small portion within the northeastern section of the construction limits (on
Lincoln Avenue NE) drains to a separate basin than the property itself. Therefore, this site contains two
separate drainage basins – Basin 1 and Basin 2.
Basin 1: Stormwater runoff produced from within the construction limits in the existing conditions for
Basin 1 leaves from the natural discharge location in the northwestern/western portion of the site.
Stormwater from the site begins by sheet flowing to the northwest over moderate slopes ranging from 2-
15% in the eastern portion of the site; once the stormwater reaches the western portion of the site, it
reaches a steep slope area with slopes of up to 75% where it continues to sheet flow off site through the
natural discharge location (Basin 1 - A). Once stormwater leaves the site, it continues to sheet flow over
steep slopes and through neighboring lots in the northwestern direction until eventually reaching Jones
Ave NE approximately 450 feet downstream of the subject site (Basin 1 - B). Once reaching Jones Ave NE,
the stormwater sheet flows across the asphalt street and continues to follow the natural topography to
the west. After approximately 250 more feet, the runoff would eventually converge with May Creek (Basin
1 - C). After the stormwater converges with May Creek, it is conveyed in the northern direction following
the natural flow path of the creek. At the ¼ mile downstream limit, stormwater is still being conveyed in
the northern direction within May Creek.
Basin 2: Stormwater runoff produced from within the construction limits in the existing conditions for
Basin 2 sheet flows towards the eastern side of Lincoln Ave NE and converges with a catch basin located
along the eastern side of the street (Basin 2 - A). From here, the storm public stormwater system conveys
stormwater north beneath Lincoln Avenue NE until the ¼ mile downstream limit is reached. It should be
noted that per Renton’s GIS Mapping System, the storm system in Lincoln Ave NE does not appear to
discharge runoff into the stream that passes through Lincoln Ave NE (Basin 2 - B).
No drainage related issues were observed downstream of the site for either drainage basin, and no
relevant drainage complaints were identified on the King County iMap system within a quarter mile of the
site discharge location. Please refer to Figure 7 on the previous page for the approximate location of
identified drainage features. Photographs from the site visit are included below.
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Basin 1 (A) – Runoff sheet flows northwest towards the natural discharge location (edge of steep
slope seen in photograph)
Basin 1 (B) – Runoff sheet flows over Jones Ave NE to the west
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Basin 1 (C) – Runoff converges with May Creek
Basin 2 (A) – Runoff enters stormwater system along eastern side of Lincoln Ave NE
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Basin 2 (B) – Storm system appears to convey runoff north through the intersection of Lincoln Ave NE
& NE 40th Street (Per Renton GIS Mapping System, the storm system does not converge with the
unnamed stream that can be seen on the Downstream Drainage Map)
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IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
Part A: Existing Site Hydrology
This property is located within the May Creek drainage basin, within the Cedar River/Lake Washington
watershed. The 48,066 SF (1.10 AC) site is currently developed with a single-family residence, detached
garage, gravel driveway, and concrete driveway. Stormwater runoff produced from the existing site sheet
flows towards the natural discharge area (NDA) located in the western portion of the site. The eastern
portion of the site contains moderate slopes ranging from 2-15%, and the western portion of the site
contains steep slopes of up to 75%. Stormwater ultimately converges with May Creek, located
approximately 700 feet west of the site. See the full downstream analysis in Section III of this Technical
Information Report (TIR).
The Geotechnical Report prepared by Terra Associates, Inc. (Appendix A) states that stormwater
management at the site should not be managed with infiltration facilities, as the soils underling the site
largely consist of silty sand which exhibit low permeabilities and would impede the downward migration
of stormwater.
Part B: Developed Site Hydrology
The project proposes the development of five (5) single-family lots within the 48,066 SF (1.10 AC) parcel.
Lot 1 is 7,307 SF and will be located in the northeastern portion of the site, Lot 2 is 8,387 SF and will be
located in the northwestern portion of the site, Lot 3 is 5,993 SF and will be located in the southeastern
portion of the site, Lot 4 is 6,096 SF and will be located directly west of Lot 3, and Lot 5 is 6,786 SF and will
be located in the southwestern portion of the site. A 1,421 SF private access tract (Tract A) is proposed
between Lots 4 and 5 and will provide access to Lots 2 and 5 via NE 36th Street in the southern portion the
site, a 4,358 SF critical area tract (Tract B) will be located along the western edge of the site, and a 7,719
SF ROW dedication is proposed along the southern and eastern property boundaries.
The proposed impervious surfaces associated with this short plat include a 1,421 SF asphalt access road,
4,863 SF of asphalt pavement widening, 1,648 SF of concrete sidewalk, 938 SF of concrete driveway
aprons, and 262 SF of concrete ADA ramps (for a total of 9,132 SF of impervious surfaces). The total
impervious surface area associated with the individual lots is 22,470 SF (based on the maximum per
zoning). The total impervious surface area that is being utilized in the drainage design for this project is
31,602 SF (maximum impervious surface area for the individual lots + short plat improvements).
All of the surfaces within Basin 1 will be collected and conveyed into a 25 FT x 50 FT x 12 FT deep detention
vault located to the south of the site within the public ROW for NE 36th Street. This detention vault will
discharge stormwater into an existing storm pipe which routes runoff towards May Creek. All of the
surfaces within Basin 2 will be collected and conveyed into the existing storm system within Lincoln Ave
NE which routes runoff in the northern direction (separate discharge area from Basin 1).
WWHM 2012 was used to model the proposed condition using target surfaces per Section 1.2.3 of the
2022 RSWDM. It should be noted that within the 54,033 SF (1.240 AC) clearing limits, there are two
drainage basins (Basin 1 & Basin 2). Each of the basin areas are different in the developed conditions than
in the existing conditions due to the additional pavement on Lincoln Avenue that will be conveyed north
when developed. The maximum impervious area per zoning for the future lot developments has been
modeled as rooftop. Additionally, 3,276 SF of existing pavement on Lincoln Ave NE will have a grind &
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overlay performed on it; this portion of roadway has been modeled as road in both the existing and
developed conditions. A summary of the analyses is provided in the tables below:
Existing Developed
Condition Measured Modeled Measured Modeled
C, Forest, Mod: 50,442 SF
(1.158 AC)
50,442 SF
(1.158 AC)
C, Lawn, Mod:
17,958 SF
(0.413 AC)
17,958 SF
(0.413 AC)
Roof Tops/Flat:
22,243 SF
(0.511 AC)
22,243 SF
(0.511 AC)
Roads/Flat: 5,461 SF
(0.125 AC)
5,461 SF
(0.125 AC)
Roads/Mod: 1,569 SF
(0.036 AC)
1,569 SF
(0.036 AC)
Driveways/Mod:
748 SF
(0.017 AC)
748 SF
(0.017 AC)
Sidewalks/Flat:
931 SF
(0.021 AC)
931 SF
(0.021 AC)
Total Area: 52,011 SF
(1.194 AC)
52,011 SF
(1.194 AC)
47,341 SF
(1.087 AC)
47,341 SF
(1.087 AC)
WWHM Conditions Model (Basin 1)
Existing Developed
Condition Measured Modeled Measured Modeled
C, Forest, Mod: 315 SF
(0.007 AC)
315 SF
(0.007 AC)
C, Lawn, Mod:
1,075 SF
(0.025 AC)
1,075 SF
(0.025 AC)
Roads/Mod: 1,707 SF
(0.039 AC)
1,707 SF
(0.039 AC)
4,448 SF
(0.102 AC)
4,448 SF
(0.102 AC)
Driveways/Mod:
190 SF
(0.004 AC)
190 SF
(0.004 AC)
Sidewalks/Flat:
979 SF
(0.022 AC)
979 SF
(0.022 AC)
Total Area: 2,022 SF
(0.046 AC)
2,022 SF
(0.046 AC)
6,692 SF
(0.153 AC)
6,692 SF
(0.153 AC)
WWHM Conditions Model (Basin 2)
Part C: Performance Standards
Based on the City of Renton’s flow control application map, the project site is located within the Duration
Flow Control Standard (Forested Conditions). Flow control facilities are required to match the developed
peak discharge rates to historical (forested) site conditions over the range of flows extending form 50% of
the 2-year up to the full 50-year flow and match the peaks for the 2- and 10-year return periods. This
project is classified as a small subdivision; therefore, it is subject to the Small Subdivision Project BMP
Requirements detailed in Section 1.2.9.3.1 in the RSWDM. Although implementation of individual lot
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04/22/2026 P a g e | 19
BMPs is not required until building permit application, BMPs have been considered for the future
improvements on Lots 1-5 based on Section 1.2.9.2.1 and of the RSWDM. The site falls within a Basic
Water Quality treatment area in accordance with Section 1.2.8.1.A of the RSWDM.
Part D: Flow Control System
Flow control will be provided for Basin 1 with a 25 FT x 50 FT x 12 FT deep detention vault located to the
south of the site within the public ROW for NE 36th Street. This detention vault will discharge stormwater
into an existing storm pipe which routes runoff towards May Creek. A Contech StormFilter catch basin is
proposed after the control structure in order to provide water quality for the pollution generating
impervious surfaces. Per WWHM modeling, the required storage volume of the system is 14,985 CF (0.344
ac-ft). The proposed vault has a provided volume of 15,000 CF.
Stormwater runoff from Basin 2 will be collected and conveyed into the existing storm system within
Lincoln Ave NE which routes runoff in the northern direction (separate discharge area from Basin 1). This
basin is exempt from flow control, as the proposed surfaces in this area result in a 0.0905 CFS increase in
the 100-year flow using 15-minute time steps, which is below the exemption threshold of 0.15 CFS. Please
refer to Appendix D for a copy of the full WWHM data output. See WWHM data inputs for the Basin 1
detention system and the flow frequency output for Basin 2 below:
Basin 1 Detention Vault
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Basin 2 Flow Frequency (0.0905 CFS < 0.15 CFS √)
Part E: Water Quality System
In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is required for this
project as new plus replaced pollution generating impervious surfaces (PGIS) exceed 5,000 SF. To address
water quality requirements, a Contech StormFilter catch basin is proposed post-detention for Basin 1.
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Conveyance system analysis and design will be completed with final engineering.
VI. SPECIAL REPORTS AND STUDIES
• Geotechnical Report by Terra Associates, Inc. dated July 23, 2025
• Wetland and Stream Reconnaissance by Wetland Resources, Inc. dated April 15, 2025
• Preliminary Tree Protection Plan by Washington Forestry Consultants, Inc. dated May 28, 2025
VII. OTHER PERMITS
• Civil Construction Permit
• Building Permits
• Right-of-Way Use Permit
VIII. CSWPP ANALYSIS AND DESIGN
A CSWPPP will be provided with final engineering.
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of
COVENANT
Bond Quantities, Facility Summaries, and a Declaration of Covenant will be provided with final
engineering.
X. OPERATION AND MAINTENANCE MANUAL
An Operation and Maintenance Manual will be provided with final engineering.
Appendix A
Geotechnical Report by Terra Associates, Inc. dated July 23, 2025
Appendix B
Wetland and Stream Reconnaissance by Wetland Resources, Inc. dated January 30, 2026
9505 19th Avenue SE, Suite 106, Everett, WA 98208 425.337.3174 www.wetlandresources.com
January 30, 2026
JKM Holdings, LLC
Attn: Geoffrey Sherwin
PO Box 188
Puyallup, WA 98371
RE: Wetland and Stream Reconnaissance – 3601 Lincoln Avenue NE, Renton, WA
Wetland Resources, Inc. (WRI) performed a site investigation on April 7, 2025, at the 1.10-acre
property located at the address referenced above. The King County tax identification number for
the subject parcel is 3345700230. The site is located within the May Creek sub-basin of the Cedar
River/Lake Washington watershed, Water Resource Inventory Area 8. The Public Land Survey
System (PLSS) locator for this parcel is Section 32, Township 24, Range 5E, W.M.
The parcel is developed with a single-family residence, a shop/garage, and driveway. Vegetation
near the house is maintained landscaping and lawn and a row of trees is present along the western
edge of the parcel. The site is relatively flat, with a west-facing slope beginning near the western
property line. Surrounding land use is generally single-family residential. May Creek, May Creek
Park, and associated undeveloped open space is located to the west/southwest of the parcel.
The purpose of this report is to present information related to wetlands and streams on and in the
vicinity of the subject parcel. Landslide, erosion, and other geological hazard areas are beyond the
scope of this report.
REVIEW OF EXISTING INFORMATION
Prior to conducting the site investigation, public resource information was reviewed to gather
background information on the subject property and the surrounding area regarding wetlands,
streams, and other critical areas. These sources include the following:
• United States Fish and Wildlife Service (USFWS) National Wetlands Inventory (NWI): This
resource maps a riverine feature (May Creek) to the west, on the west side of Jones Avenue NE.
• USDA/NRCS Web Soil Survey: The Web Soil Survey indicates that the property is underlain
by Alderwood gravelly sandy loam, 8 to 15 percent slopes.
• WDFW Priority Habitat and Species (PHS) Interactive Map: The PHS Interactive Map maps
May Creek off site to the west. This stream is listed as habitat for Chinook salmon, sockeye
salmon, coho salmon, and steelhead trout.
Wetland Resources, Inc. Lincoln Avenue Reconnaissance Report
Revision 1: January 30, 2026 WRI #25103 2
• King County iMap: King County depicts May Creek to the west of the site, on the west side of
Jones Avenue NE.
• City of Renton interactive GIS map: This resource maps May Creek and an associated wetland
over 300 feet off site to the west. Another wetland is mapped approximately 100 feet to the
south of the property. Landslide and erosion hazard areas are shown in the western portion of
the site. Geologically hazardous areas are outside of the scope for this report.
METHODOLOGY
The Washington State Department of Ecology document Determining the Ordinary High Water Mark
for Shoreline Management Act Compliance in Washington State (Anderson et al. 2016) was used to determine
the presence of any streams on the subject site.
Wetland areas were determined using the routine determination approach described in the Corps
of Engineers Wetlands Delineation Manual (Environmental Laboratory 1987) and the Regional Supplement
to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version
2.0) (U.S. Army Corps of Engineers 2010). Under the routine methodology, the process for making
a wetland determination is based on three steps:
1) Examination of the site for hydrophytic vegetation (species present and percent cover);
2) Examination of the site for hydric soils;
3) Determining the presence of wetland hydrology
The wetland identified was rated pursuant to the Washington State Wetland Rating System for Western
Washington: 2014 Update as required by Renton Municipal Code (RMC) 4-3-050G.9.c. Please note
the wetland ratings presented in this report are based on preliminary information and are subject
to change if the wetlands are formally delineated.
FINDINGS
On-site vegetation near the residence includes Japanese maples, wisteria, rhododendrons, and
other installed landscaping plants. Native vegetation observed near the western boundary of the
site includes big leaf maple (Acer macrophyllum; FACU), western hemlock (Tsuga heterophylla; FACU),
snowberry (Symphoricarpos albus; FACU), and sword fern (Polystichum munitum; FACU). Sampled soils
were dry and generally very dark brown (10YR 2/2) in the upper layer and dark brown (10YR
3/3) in the second layer. Soil texture was typically loam or sandy loam across the site. Given the
lack of hydrophytic vegetation, wetland hydrology, or hydric soil indicators, there are no wetland
areas present on the property. No flowing water, channels, scours, or sorted material were observed
on the site; therefore, there are no streams on the site.
Off-site Wetlands and Streams
May Creek and an adjacent wetland are approximately 320 feet to the west/southwest of the site.
Since May Creek and the adjacent wetland are over 300 feet from the subject property, these
features do not cast a buffer onto the parcel. Shoreline jurisdiction would extend 200 feet from the
edge of these features and per the City of Renton’s GIS map information, the shoreline
environment associated with May Creek terminates west of the site.
Wetland Resources, Inc. Lincoln Avenue Reconnaissance Report
Revision 1: January 30, 2026 WRI #25103 3
A second wetland mapped by the City of Renton is present a little over 100 feet to the south the of
property. This wetland (Wetland A) was evaluated and is discussed below.
Wetland A (Off-site)
HGM Category: Slope
Wetland Rating Category: III
City of Renton Buffer: 100 feet
Wetland A is a located approximately 100 feet south of the subject property along a sloped area
east of Jones Avenue NE. As this wetland is off-site, information about this wetland was gathered
from aerial imagery, publicly available resources like the City of Renton interactive map, and
observations from adjacent rights-of-way.
Vegetation in Wetland A includes black cottonwood (Populus balsamifera; FAC), red alder (Alnus
rubra; FAC), Himalayan blackberry (Rubus armeniacus; FAC), horsetail (Equisetum sp.), and reed
canarygrass (Phalaris arundinacea; FACW). Saturation and standing water were observed at the toe
of the slope, along the west side of Jones Avenue NE. As the wetland is located off of the property,
soils within the wetland area were not sampled.
Wetland A is a Category III wetland with a moderate (five points) habitat score. Per RMC 4-3-
050G.2, this wetland requires a 100-foot buffer and a 15-foot building setback from the wetland
buffer.
USE OF THIS REPORT
This Wetland and Stream Reconnaissance Report has been prepared for JKM Holdings, LLC to
assist with identifying on-site and nearby critical areas as required by the City of Renton. This
report is based largely on readily observable conditions and, to a lesser extent, on readily
ascertainable conditions. No attempt has been made to determine hidden or concealed conditions.
The laws applicable to critical areas are subject to varying interpretations and may be changed at
any time by the courts or legislative bodies. This report is intended to provide information deemed
relevant in the applicant's attempt to comply with the laws now in effect.
This report conforms to the standard of care employed by ecologists. No other representation or
warranty is made concerning the work or this report and any implied representation or warranty
is disclaimed.
Wetland Resources, Inc.
Meryl Kamowski, PWS
Senior Ecologist
Enclosure: Reconnaissance Map
Appendix C
Preliminary Tree Protection Plan by Washington Forestry Consultants, Inc. dated April 17, 2026
WASHINGTON FORESTRY CONSULTANTS, INC.
FORESTRY AND VEGETATION MANAGEMENT SPECIALISTS W F C I
O: 360/943-1723
C: 360/561-4407 9136 Yelm Hwy SE Olympia, WA 98513
URBAN/RURAL FORESTRY • TREE APPRAISAL • TREE RISK ASSESSMENT RIGHT-OF-WAYS • VEGETATION MANAGEMENT • FOREST/TREE MGT. PLANS • EXPERT TESTIMONY Member of International Society of Arboriculture and Society of American Foresters
-Preliminary Tree Protection Plan-
LINCOLN PEAK SHORT PLAT
3601 Lincoln Avenue NE Renton, WA 98055
Prepared for: Trumark Homes Washington, LLC
Prepared by: Washington Forestry Consultants, Inc.
Date of Report: April 17, 2026
Introduction
The project proponent is planning to construct a new 5 lot short plat on one parcel totaling 1.10-acres at Lincoln Peak Short Plat in Renton. The proponent has retained WFCI to:
•Evaluate and inventory all trees on the site pursuant to the requirements of the City of
Renton 4-4-130 Tree Retention and Land Clearing Regulations.
•Make recommendations for retention of significant trees, along with required protectionand cultural measures.
•Complete the City of Renton Tree Retention and Credit Worksheet.
Observations
Methodology
WFCI has evaluated all trees with a caliper of at least 6" diameter at breast height (DBH), except
alder or cottonwood trees, which qualify as significant trees with a caliper of 8" or greater. To be a significant tree, it must have a condition rating of Fair or better. Trees rated as Poor, Very Poor, or Dead or are defective, diseased and/or in decline and are not long-term trees and are not considered to be significant trees. All off-site trees with driplines or root protection zones (RPZ’s) encroaching the site were assessed as well.
The tree evaluation phase used methodology developed by Nelda Matheny and Dr. James Clark in their 1998 publication Trees and Development: A Technical Guide to Preservation of Trees during Land Development.
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Site Description
The project site consists of one 1.10-acre parcel, #3345700230. A single-family home and
associated outbuildings are on the site. Most of the parcel is gently sloping to the west with very steep slopes on the western edge. There is a 0.10-acre steep slope critical area in this part of the site. The site is bordered by single-family homes to the north, south, and west, and Lincoln Avenue to the east.
Soils Description According to the USDA Natural Resource Conservation Service soil survey the three soil types in the project area are variants of the Alderwood gravelly sandy loam, a moderately deep, moderately
well drained soil found on glacial till plains. It is formed in ablation till overlying basal till. A
weakly cemented hardpan is at a depth of 20 to 40 inches. Permeability is moderately rapid above the hardpan and very slow in the pan. Available water capacity is low. Effective rooting depth is 20-40 inches. A perched seasonal high-water table is at a depth of 18-36 inches from November to March. The potential for windthrow of trees is moderate under normal conditions. New trees
require irrigation for establishment.
In areas where grading brings the hardpan nearer to the surface, the hardpan must be fractured under new trees to provide soil volume for root development and to improve drainage around the tree.
Figure 1. Lincoln Peak Short Plat Soils Map
AgC - Alderwood gravelly sandy loam 8 – 15% slope AgD – Alderwood gravelly sandy loam 15 – 30% slope AkF – Alderwood and Kitsap soils – very steep
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Existing Tree Conditions
There is one forest cover type on the project area for the purpose of description. The aerial photo
of the project, with tree locations, is shown in Attachment 1.
Type I. -- This cover type includes the entire project site. A total of 24 trees were found on the
parcel. There are introduced trees planted around the home and naturally seeded trees throughout the site. The size of significant trees ranges from 6 inches to 41 inches in diameter at breast height (DBH). Tree species include bigleaf maple (Acer macrophyllum), Callery pear (Pyrus calleryana), giant sequoia (Sequoiadendron giganteum), noble fir (Abies procera), smoke tree (Cotinus
coggygria), weeping willow (Salix babylonica), and western hemlock (Tsuga heterophylla).
Tree conditions on the site range from ‘Poor’ to ‘Good,’ with 92% being rated in ‘Fair’ or better condition. Twenty-two of the 24 significant trees could be potentially retained on this site when only tree health is considered. The remaining trees are multi-stemmed resprouted stumps that are
not quality formed trees to save. The eight Landmark sized tree on the project site are healthy.
Sixteen of the trees are located in a steep slope critical area. Table 1. Summary of trees on Lincoln Peak Short Plat Site.
Species DBH Range (in.)
# of Healthy Trees
# of Unhealthy Trees*
Total # of Trees
# of Landmark Trees**
Bigleaf Maple 6 – 12 11 2 13 3
Callery Pear 9 – 11 3 0 3 0
Giant Sequoia 28 – 36 3 0 3 3
Noble Fir 12 1 0 1 0
Smoke Tree 8 1 0 1 0
Weeping Willow 41 1 0 1 1
Western Hemlock 19 2 0 2 1
Sum 6 – 41 22 2 24 8
*Trees rated as dead, very poor, or poor.
** Trees ≥24” DBH, bigleaf maple, red alder, cottonwood ≥30” DBH The understory vegetation throughout the type is grass, weeds, and other planted shrubs in the landscape. Himalayan blackberry (Rubus armeniacus) covers a large portion of the site.
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Photo 1: View of trees on the Lincoln Peak Short Plat Site.
Off-site Impacts
Five off-site trees will be removed from the Lincoln Avenue and NE 36th Street rights-of-ways to construct this project. These trees are included in the tree list in Attachment 3. Discussion
Potential for Tree Retention The site plan shows no trees being retained on the buildable area of the site. The topography and required grading restrict the retention of trees and the strict application of the code would prevent reasonable use of the property.
Trees 1, 2, 3, 11, 12, & 13 are all located under new required sidewalks. Tree 7 is in the middle of the proposed access tract. Tree 8 is within 4 feet of the access tract and will have 2 – 4 feet of fill covering the entire root protection zone. None of these trees have opportunities to be saved based on these conditions.
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Sixteen bigleaf maple, western hemlock, noble fir, and giant sequoia trees will be saved in the critical area.
Tree Density Calculations
Title 4-4-130H(a) of the Renton Municipal Code (RMC) requires 30% of the significant trees on the site to be retained. There are a total of 8 significant sized trees on the parcel outside the critical area for calculating the 30% requirement. A total of 2 significant trees will need to be retained in the project area to meet the requirement.
Total # of Healthy Significant Trees: 24 Trees # of High Risk Significant Trees: 0 Trees # of Trees in Steep Slope Critical Area: 16 Trees
# of Significant Trees After Deductions: 8 Trees
# of Significant Trees Required to be Saved (30% of 8 Trees): 2 Trees
# of Significant Trees Planned to be Saved 0 Trees
Shortfall of Significant Tree Requirement 2 Trees Additionally, RMC4-4-130H(b) requires a minimum tree credit density of 30 tree credits per acre
of net developable acreage. The following is a summary of the projected tree density requirements:
Gross Site Acreage: 1.10 Acres Proposed Rights-of-way Acreage: 0.21 Acres Critical Area Acreage: 0.10 Acres
Net Developable Acres: 0.79 Acres
Required Tree Credit Density (0.79 Acres x 30 Credits/Acre): 24.0 Tree Credits
Proposed Tree Retention:
Developed Area (0 trees) 0.0 Tree Credits Shortfall of Tree Credit Requirement: 24.0 Tree Credits
By retaining no trees in the buildable area of the site this plan falls short of the minimum significant
tree retention requirement by 2 trees. Planned tree credit retention is less than the minimum tree credits by 24.0 credits. Twenty-four tree credits will be required to replace the minimum credit shortfall and 18 tree credits are required to meet the significant tree requirement. When the required number of protected trees cannot be retained, replacement trees, with at least a two-inch (2")
caliper deciduous or an evergreen at least six feet (6') tall, shall be planted based on the tree credit
value of each protected tree removed. The replacement trees should be planted on the backs of lots 1, 2 & 5. A fee in lieu of tree planting, the cost of which can be determined by the City of Renton can also substitute for tree replacement if replanting on-site is not feasible.
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All reasonable efforts have been taken to preserve trees utilizing the highest priority possible. The small lots, location of existing trees, required grading, utilities, and mandatory road improvements
prevents trees to be saved on the project. The required tree credits will be met through the planting
of 21 large replacement trees. Recommendations
Tree Protection Measures
All save trees, including off-site edge trees, must be protected during construction by a temporary chain-link fence (Attachment 8). Placards shall be placed on the fencing every 50 feet indicating the words, "NO TRESPASSING - Protected Trees". The individual tree RPZ is the dripline (6
feet minimum), unless otherwise delineated by WFCI in the field and described in the attached tree list (Attachment 3). If approved, the silt-fence could double as the tree protection fence for select off-site trees.
Tree protection fences should be placed around the edge of the root protection zone (RPZ). The
fence should be erected after logging but prior to the start of clearing. The fences should be maintained until the start of the landscape installation. There should be no equipment activity (including rototilling) within the root protection zone. No
irrigation lines, trenches, or other utilities should be installed within the RPZ. Cuts or fills should
impact no more than 20% of a tree’s root system. If topsoil is added to the root zone of a protected tree, the depth should not exceed 2 inches of a sandy loam or loamy fine sand topsoil and should not cover more than 20% of the root system.
If roots are encountered outside the RPZ during construction, they should be cut cleanly with a
saw and covered immediately with moist soil. Noxious vegetation within the root protection zone should be removed by hand. If a proposed save tree must be impacted by grading or fills more than allowed for by WFCI in the tree list, then the tree should be re-evaluated by WFCI to determine if the tree can be saved with mitigating measures, or if the tree should be removed.
Pruning and Thinning Pruning should be done to coincide with land clearing, to facilitate clean-up and while access to the trees is available (before construction).
All individual trees to be saved near or within developed areas should have their crowns raised to provide a minimum of 8 feet of ground clearance over sidewalks and landscape areas, 15 feet over parking lots or streets, and at least 10 feet of building clearance. Care will need to be taken to avoid trespassing when pruning offsite trees. This is best achieved by getting cooperation and
permission from the tree owner. If no permission is obtained, then legally one cannot prune
beyond the property line – ground to sky.
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All pruning should be done according to the ANSI A300 standards for proper pruning and be completed by an International Society of Arboriculture Certified Arborist® or be supervised by a
Certified Arborist®. Conclusions and Timeline for Activity
1. No trees outside of the critical area are proposed to be retained on the site.
2. The final, approved tree protection plan map should be included in the construction drawings for bid and construction of the project and should be labeled as such. 3. Stake and heavily flag the clearing limits. 4. Contact WFCI to attend pre-job conference and discuss tree protection issues with contractors.
WFCI can verify all trees to be saved and/or removed are adequately marked.
5. Conduct logging. Complete necessary hazard tree removals and invasive plant removals from the tree protection areas. No equipment should enter the tree protection areas during logging. 6. Before land clearing is complete, do all necessary pruning on save trees and off-site trees to provided new home clearances.
7. Contact WFCI to inspect the tree tracts after logging, but prior to land clearing to identify any
additional hazard trees that should be removed. 8. Install tree protection fences along the 'limits of construction'. The fences should be located at the limits of construction or at the dripline of the save tree or as otherwise specified by WFCI. Maintain fences throughout construction.
9. Complete clearing of the project.
10. Do not excavate stumps within 10’ of trees to be saved. These should be individually evaluated by WFCI to determine the method of removal. 11. Complete grading and construction of the project. 12. Contact WFCI to final inspect the tree protection areas after grading.
13. All save trees within reach of targets should be inspected annually for 2 years by a qualified
professional forester retained by the homeowner’s association, and bi-annually thereafter. The purpose of these inspections is to identify trees that develop problems due to changing micro-site conditions and to prescribe cultural care or removal.
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Summary
The City of Renton Municipal Code calls for 2 of the healthy, significant trees and 24.0 tree credits
be retained on the site. Based on the current site plan no trees will be retained because all healthy, significant trees in the buildable area are under the footprint of proposed improvements. An additional 21 large scale trees are planned to replace the 30% significant tree requirement and tree credit shortfall.
Please give us a call if you have any questions. Respectfully submitted,
Washington Forestry Consultants, Inc.
Galen M. Wright, ACF, ASCA Joshua Sharpes ISA Bd. Certified Master Arborist PN-129BU Professional Forester Certified Forester No. 44 ISA Certified Arborist®,
ISA Tree Risk Assessor Qualified Urban Forest Professional, PN- 5939AM
ASCA Tree and Plant Appraisal Qualified ISA Tree Risk Assessor Qualified
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Attachment 1. Aerial Photo of Lincoln Peak Short Plat Site
(2023 King County)
Parcel Area Boundary
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Attachment 2. Current Site Conditions of Lincoln Peak Short Plat
Parcel Area Boundary
Critical Area Boundary
Healthy Tree
Unhealthy Tree
Off-Site Tree
Critical Area Tree
1
2 3
4 5 6
7
8
9 10
11
12
13 29
28
27
26
25
24
23 22
14 15
16 17
18 19
20 21
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Attachment 3. Lincoln Peak Short Plat Site Plan
Project Area Boundary
Tree Protection Fence Location
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Attachment 4. List of Trees on Lincoln Peak Short Plat
Trees in Critical Area
Off-site Tree
Tree # Species DBH (in.) Calculated DBH (in.) Condition Average Dripline (feet)
Landmark Tree
Save Based on Condition Alone? Yes or No
Tree Protection Zone (feet)
Project Plan. Save or Remove
Tree Credits Comment
1 Callery Pear 11 Fair 10 Yes 10 Remove 5 topped for powerline
2 Callery Pear 9 Fair 10 Yes 10 Remove 4 topped for powerline
3 Callery Pear 9 Fair 10 Yes 10 Remove 4 topped for powerline
4 Callery Pear 11 Fair 10 Yes 10 Remove 5 topped for powerline
5 Hawthorn 12 Good 12 Yes 12 Remove 6
6 Western Hemlock 13, 14 19 Good 16 Yes 16 Remove 8
7 Weeping Willow 41 Good 20 Yes Yes 30 Remove 13
8 Smoke Tree 8 Fair 8 Yes 8 Remove 4
9 Black Cottonwood 10, 11 15 Good 12 Yes 12 Remove 6 no #
10 Black Cottonwood 9 Good 10 Yes 10 Remove 4 no #
11 Bigleaf Maple 3 - 6 10 Poor 8 No 8 Remove 5 5 stem sprouted stump
12 Bigleaf Maple 6 Good 10 Yes 10 Remove 4
13 Bigleaf Maple 3 -5 12 Poor 10 No 10 Remove 5 8 stem sprouted stump
14 Bigleaf Maple 24 Good Yes Yes Save in steep slope critical area
15 Bigleaf Maple 18 Good Yes Save in steep slope critical area
16 Bigleaf Maple 17 Good Yes Save in steep slope critical area
17 Bigleaf Maple 9 Good Yes Save in steep slope critical area
18 Bigleaf Maple 9 Good Yes Save in steep slope critical area
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Tree # Species DBH (in.) Calculated DBH (in.) Condition Average Dripline (feet)
Landmark Tree
Save Based on Condition Alone? Yes or No
Tree Protection Zone (feet)
Project Plan. Save or Remove
Tree Credits Comment
19 Bigleaf Maple 20 Good Yes Save in steep slope critical area
20 Bigleaf Maple 14 Good Yes Save in steep slope critical area
21 Bigleaf Maple 34 Good Yes Yes Save in steep slope critical area
22 Bigleaf Maple 26 Good Yes Yes Save in steep slope critical area
23 Bigleaf Maple 14 Good Yes Save in steep slope critical area
24 Giant Sequoia 36 Good Yes Yes Save in steep slope critical area
25 Giant Sequoia 30 Good Yes Yes Save in steep slope critical area
26 Giant Sequoia 28 Good Yes Yes Save in steep slope critical area
27 Western Hemlock 24 Good Yes Yes Save in steep slope critical area
28 Western Hemlock 20 Good Yes Save in steep slope critical area
29 Noble Fir 12 Good Yes Save in steep slope critical area
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Attachment 5. City of Renton Tree Retention and Credit Worksheet (3 pages)
rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 1 of 3
CITY OF RENTON Ι PERMIT CENTER
TREE RETENTION AND CREDIT WORKSHEET
TREE RETENTION REQUIREMENTS
A minimum retention of thirty percent (30%) of all significant trees (as defined in RMC 4-11-200) is required on site.
Please complete the form below to verify compliance with minimum tree retention requirements.
• Identify total number of trees 6-inch caliper or greater (or alder or
cottonwood trees 8-inch caliper or greater) on site: Trees
Trees
Trees
Trees
Trees
Trees Required
Trees Proposed
•Deductions – Certain trees are excluded from the retention calculation:
o Trees that are high-risk, as defined in RMC 4-11-200:
o Trees within existing and proposed public right-of-way:
o Trees within wetlands, streams, very high landslide hazards,
protected slopes, and associated buffers:
•Total remaining trees after deductions:
•Required tree retention (30%):
•Identify number of trees proposed for retention:
•Identify number of trees requested for replacement in lieu of retention
(skip page 3 if no tree replacement is requested):Trees
TREE CREDIT REQUIREMENTS
Tree credit requirements apply at a minimum rate of thirty (30) credits per net acre. Complete the form below to
determine minimum tree credit requirements.
•Gross area of property in square feet: Square Feet
•Deductions: Certain areas are excluded from tree credit calculation:
o Existing and proposed public right-of-way: Square Feet
o Wetlands, streams, very high landslide hazards, protected slopes,
and associated buffers: Square Feet
•Total excluded area:Square Feet
•Net land area (after deductions) in square feet:Square Feet
•Net land area (after deductions) in acres:Acres
•Required tree credits:Tree Credits Required
rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 2 of 3
TREE RETENTION AND CREDIT WORKSHEET
PROPOSED TREE CREDITS
Please complete the table below to calculate the total tree credits proposed for your project. Identify the quantity of trees
for each tree category, after deducting trees within excluded areas, as shown in the previous section.
TREE SIZE TREE CREDITS TREE QUANTITY TOTAL TREE CREDITS
RETAINED TREES
Preserved tree 6 – 9” caliper 4
Preserved tree 10 – 12” caliper 5
Preserved tree 12 – 15” caliper 6
Preserved tree 16 – 18” caliper 7
Preserved tree 19 – 21” caliper 8
Preserved tree 22 – 24” caliper 9
Preserved tree 25 – 28” caliper 10
Preserved tree 29 – 32” caliper 11
Preserved tree 33 – 36” caliper 12
Preserved tree 37” caliper and greater 13
NEW TREES
New small species tree (30' or less at maturity) 0.25
New medium species tree (30' to 50' at maturity)
1
New large species tree (50' or more at maturity) 2
TREE CREDITS PROPOSED:
rentonwa.gov/permitcenter | planningcustomerservice@rentonwa.gov | 425-430-7294 10/6/2022 Page 3 of 3
TREE RETENTION AND CREDIT WORKSHEET
TREE REPLACEMENT JUSTIFICATION
Replacement may be authorized as an alternative to 30% retention provided the removal is the minimum necessary to
accomplish the desired purpose and provided the proposal meets one of the following options:
a. There are special circumstances related to the size, shape, topography, location, or surroundings of the subject
property; or
b. The strict application of the code would prevent reasonable use of property; or
c. The strict application of the code would prevent compliance with minimum density requirements of the zone; or
d. The project is a short plat with four (4) or fewer lots.
Please attach a written justification demonstrating compliance with the requirements and criteria as descripted above.
TREE REPLACEMENT QUANTITY
Tree replacement quantity is determined based on the credit value of the trees proposed for removal. Larger, higher
priority trees shall be used for calculation of tree replacement. Identify the quantity of each tree requested to be removed
in lieu of 30% retention, based on tree size. List the identification number of each tree, as indicated in the arborist report.
TREE SIZE TREE CREDITS TREE QUANTITY TREE INDENTIFICATION # TOTAL TREE CREDITS
Tree 37” caliper + 13
Tree 33 – 36” caliper 12
Tree 29 – 32” caliper 11
Tree 25 – 28” caliper 10
Tree 22 – 24” caliper 9
Tree 19 – 21” caliper 8
Tree 16 – 18” caliper 7
Tree 12 – 15” caliper 6
Tree 10 – 12” caliper 5
Tree 6 – 9” caliper 4
REPLACEMENT CREDITS REQUIRED:
TREE REPLACEMENT PLANTING
Identify the quantity of proposed new replacement trees (minimum size of 2-inch caliper). The total replacement credits
proposed should be equal to or greater than the replacement credits required, as shown in the previous section.
TREE SIZE TREE CREDITS TREE QUANTITY TOTAL TREE CREDITS
New small species tree (30' or less at maturity) 0.25
New medium species tree (30' to 50' at maturity)
1
New large species tree (50' or more at maturity) 2
REPLACEMENT CREDITS PROPOSED:
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Attachment 6. Individual Tree Rating Key for Tree Condition
RATING SYMBOL DEFINITION
Very Good VG • Balanced crown that is characteristic of the species
• Normal lateral and terminal branch growth rates for the species and soil type
• Stem sound, normal bark vigor
• No root problems
• No insect or disease problems
• Long-term, attractive tree Good G • Crown lacking symmetry but nearly balanced
• Normal lateral and terminal branch growth rates for the species and
soil type
• Minor twig dieback O.K.
• Stem sound, normal bark vigor
• No root problems
• No or minor insect or disease problems – insignificant
• Long-term tree
Fair F • Crown lacking symmetry due to branch loss
• Slow lateral and terminal branch growth rates for the species and soil type
• Minor and major twig dieback – starting to decline
• Stem partly unsound, slow diameter growth and low bark vigor
• Minor root problems
• Minor insect or disease problems
• Short-term tree 10-30 years
RATING SYMBOL DEFINITION
Poor P • Major branch loss – unsymmetrical crown
• Greatly reduced growth
• Several structurally import dead or branch scaffold branches
• Stem has bark loss and significant decay with poor bark vigor
• Root damage
• Insect or disease problems – remedy required
• Short-term tree 1-10 years
Very Poor VP • Lacking adequate live crown for survival and growth
• Severe decline
• Minor and major twig dieback
• Stem unsound, bark sloughing, previous stem or large branch failures, very poor bark vigor
• Severe root problems or disease
• Major insect or disease problems
• Mortality expected within the next few years Dead DEAD • Dead
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Attachment 7. Description of Tree Evaluation Methodology The evaluation of the tree condition on this site included the visual assessment of:
1. Live-crown ratio, 2. Lateral and terminal branch growth rates, 3. Presence of dieback in minor and major scaffold branches and twigs, 4. Foliage color, 5. Stem soundness and other structural defects,
6. Visual root collar examination, 7. Presence of insect or disease problems. 8. Windfirmness if tree removal will expose this tree to failure. In cases where signs of internal defect or disease were suspected, a core sample was taken to look
for stain, decay, and diameter growth rates. Also, root collars were exposed to look for the presence of root disease. In all cases, the overall appearance of the tree was considered relative to its ability to add value to either an individual lot or the entire subdivision. Also, the scale of the tree and its proximity
to both proposed and existing houses was considered. Lastly, the potential for incorporation into the project design is evaluated, as well as potential site plan modifications that may allow otherwise removed tree(s) to be both saved and protected in the development.
Trees that are preserved in a development must be carefully selected to make sure that they can survive construction impacts, adapt to a new environment, and perform well in the landscape. Healthy, vigorous trees are better able to tolerate impacts such as root injury, changes in soils moisture regimes, and soil compaction than are low vigor trees.
Structural characteristics are also important in assessing suitability. Trees with significant decay and other structural defects that cannot be treated are likely to fail. Such trees should not be preserved in areas where damage to people or property could occur.
Trees that have developed in a forest stand are adapted to the close, dense conditions found in such stands. When surrounding trees are removed during clearing and grading, the remaining trees are exposed to extremes in wind, temperature, solar radiation, which causes sunscald, and other influences. Young, vigorous trees with well-developed crowns are best able to adapt to these changing site conditions.
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Attachment 8. Tree Protection Fence Detail
6 ft. Temporary Chain Link Fence
NO TRESPASSING - Protected Trees
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Attachment 9. Assumptions and Limiting Conditions
1) Any legal description provided to the Washington Forestry Consultants, Inc. is assumed to be correct. Any
titles and ownership's to any property are assumed to be good and marketable. No responsibility is assumed for matters legal in character. Any and all property is appraised or evaluated as though free and clear, under
responsible ownership and competent management.
2) It is assumed that any property is not in violation of any applicable codes, ordinances, statutes, or other governmental regulations, unless otherwise stated.
3) Care has been taken to obtain all information from reliable sources. All data has been verified insofar as
possible; however, Washington Forestry Consultants, Inc. can neither guarantee nor be responsible for the accuracy of information.
4) Washington Forestry Consultants, Inc. shall not be required to give testimony or to attend court by reason of this report unless subsequent contractual arrangements are made, including payment of an additional fee for such services as described in the fee schedule and contract of engagement.
5) Loss or alteration of any part of this report invalidated the entire report.
6) Possession of this report or a copy thereof does not imply right of publication or use for any purpose by any other than the person to whom it is addressed, without the prior expressed written or verbal consent of Washington Forestry Consultants, Inc.
7) Neither all or any part of the contents of this report, nor copy thereof, shall be conveyed by anyone, including the client, to the public through advertising, public relations, news, sales or other media, without the prior expressed written or verbal consent of Washington Forestry Consultants, Inc. -- particularly as to value conclusions, identity of Washington Forestry Consultants, Inc., or any reference to any professional society or to any initialed designation conferred upon Washington Forestry Consultants, Inc. as stated in its qualifications.
8) This report and any values expressed herein represent the opinion of Washington Forestry Consultants, Inc., and the fee is in no way contingent upon the reporting of a specified value, a stipulated result, the occurrence neither of a subsequent event, nor upon any finding in to reported. 9) Sketches, diagrams, graphs, and photographs in this report, being intended as visual aids, are not necessarily to scale and should not be construed as engineering or architectural reports or surveys. 10) Unless expressed otherwise: 1) information contained in this report covers only those items that were examined and reflects the condition of those items at the time of inspection; and 2) the inspection is limited to visual examination of accessible items without dissection, excavation, probing, or coring. There is no warranty or guarantee, expressed or implied, that problems or deficiencies of the tree or other plant or property in question may not arise in the future.
Note: Even healthy trees can fail under normal or storm conditions. The only way to eliminate all risk is to remove all trees within reach of all targets. Annual inspections by an ISA Certified Arborist or Certified Forester will reduce the potential of tree failures. It is impossible to predict with certainty that a tree will stand or fail, or the timing of the failure. It is considered an ‘Act of God’ when a tree fails, unless it is directly felled or pushed over by man’s actions.
Appendix D
WWHM Output
WWHM2012
PROJECT REPORT
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General Model Information
WWHM2012 Project Name:Lincoln Peak Short Plat
Site Name:Lincoln Peak Short Plat
Site Address:3601 Lincoln Ave NE
City:Renton
Report Date:2/27/2026
Gage:Seatac
Data Start:1948/10/01
Data End:2009/09/30
Timestep:15 Minute
Precip Scale:1.000
Version Date:2024/10/15
Version:4.3.1
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
Low Flow Threshold for POC2:50 Percent of the 2 Year
High Flow Threshold for POC2:50 Year
Lincoln Peak Short Plat 2/27/2026 2:37:39 PM Page 3
Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Forest, Mod 1.158
Pervious Total 1.158
Impervious Land Use acre
ROADS MOD 0.036
Impervious Total 0.036
Basin Total 1.194
Element Flow Componants:
Surface Interflow Groundwater
Componant Flows To:
POC 1 POC 1
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Basin 2
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Forest, Mod 0.007
Pervious Total 0.007
Impervious Land Use acre
ROADS MOD 0.039
Impervious Total 0.039
Basin Total 0.046
Element Flow Componants:
Surface Interflow Groundwater
Componant Flows To:
POC 2 POC 2
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Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Lawn, Mod 0.413
Pervious Total 0.413
Impervious Land Use acre
ROADS FLAT 0.125
ROOF TOPS FLAT 0.511
DRIVEWAYS MOD 0.017
SIDEWALKS FLAT 0.021
Impervious Total 0.674
Basin Total 1.087
Element Flow Componants:
Surface Interflow Groundwater
Componant Flows To:
Vault 1 Vault 1
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Basin 2
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Lawn, Mod 0.025
Pervious Total 0.025
Impervious Land Use acre
ROADS MOD 0.102
DRIVEWAYS MOD 0.004
SIDEWALKS MOD 0.022
Impervious Total 0.128
Basin Total 0.153
Element Flow Componants:
Surface Interflow Groundwater
Componant Flows To:
POC 2 POC 2
Lincoln Peak Short Plat 2/27/2026 2:37:39 PM Page 7
Routing Elements
Predeveloped Routing
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Mitigated Routing
Vault 1
Width:25 ft.
Length:50 ft.
Depth:13 ft.
Discharge Structure
Riser Height:12 ft.
Riser Diameter:18 in.
Orifice 1 Diameter:0.516 in.Elevation:0 ft.
Orifice 2 Diameter:0.750 in.Elevation:8 ft.
Element Outlets:
Outlet 1 Outlet 2
Outlet Flows To:
Vault Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs)
0.0000 0.028 0.000 0.000 0.000
0.1444 0.028 0.004 0.002 0.000
0.2889 0.028 0.008 0.003 0.000
0.4333 0.028 0.012 0.004 0.000
0.5778 0.028 0.016 0.005 0.000
0.7222 0.028 0.020 0.006 0.000
0.8667 0.028 0.024 0.006 0.000
1.0111 0.028 0.029 0.007 0.000
1.1556 0.028 0.033 0.007 0.000
1.3000 0.028 0.037 0.008 0.000
1.4444 0.028 0.041 0.008 0.000
1.5889 0.028 0.045 0.009 0.000
1.7333 0.028 0.049 0.009 0.000
1.8778 0.028 0.053 0.009 0.000
2.0222 0.028 0.058 0.010 0.000
2.1667 0.028 0.062 0.010 0.000
2.3111 0.028 0.066 0.011 0.000
2.4556 0.028 0.070 0.011 0.000
2.6000 0.028 0.074 0.011 0.000
2.7444 0.028 0.078 0.012 0.000
2.8889 0.028 0.082 0.012 0.000
3.0333 0.028 0.087 0.012 0.000
3.1778 0.028 0.091 0.012 0.000
3.3222 0.028 0.095 0.013 0.000
3.4667 0.028 0.099 0.013 0.000
3.6111 0.028 0.103 0.013 0.000
3.7556 0.028 0.107 0.014 0.000
3.9000 0.028 0.111 0.014 0.000
4.0444 0.028 0.116 0.014 0.000
4.1889 0.028 0.120 0.014 0.000
4.3333 0.028 0.124 0.015 0.000
4.4778 0.028 0.128 0.015 0.000
4.6222 0.028 0.132 0.015 0.000
4.7667 0.028 0.136 0.015 0.000
4.9111 0.028 0.140 0.016 0.000
5.0556 0.028 0.145 0.016 0.000
5.2000 0.028 0.149 0.016 0.000
5.3444 0.028 0.153 0.016 0.000
Lincoln Peak Short Plat 2/27/2026 2:37:39 PM Page 9
5.4889 0.028 0.157 0.016 0.000
5.6333 0.028 0.161 0.017 0.000
5.7778 0.028 0.165 0.017 0.000
5.9222 0.028 0.169 0.017 0.000
6.0667 0.028 0.174 0.017 0.000
6.2111 0.028 0.178 0.018 0.000
6.3556 0.028 0.182 0.018 0.000
6.5000 0.028 0.186 0.018 0.000
6.6444 0.028 0.190 0.018 0.000
6.7889 0.028 0.194 0.018 0.000
6.9333 0.028 0.199 0.019 0.000
7.0778 0.028 0.203 0.019 0.000
7.2222 0.028 0.207 0.019 0.000
7.3667 0.028 0.211 0.019 0.000
7.5111 0.028 0.215 0.019 0.000
7.6556 0.028 0.219 0.020 0.000
7.8000 0.028 0.223 0.020 0.000
7.9444 0.028 0.228 0.020 0.000
8.0889 0.028 0.232 0.025 0.000
8.2333 0.028 0.236 0.028 0.000
8.3778 0.028 0.240 0.030 0.000
8.5222 0.028 0.244 0.032 0.000
8.6667 0.028 0.248 0.033 0.000
8.8111 0.028 0.252 0.035 0.000
8.9556 0.028 0.257 0.036 0.000
9.1000 0.028 0.261 0.037 0.000
9.2444 0.028 0.265 0.039 0.000
9.3889 0.028 0.269 0.040 0.000
9.5333 0.028 0.273 0.041 0.000
9.6778 0.028 0.277 0.042 0.000
9.8222 0.028 0.281 0.043 0.000
9.9667 0.028 0.286 0.044 0.000
10.111 0.028 0.290 0.045 0.000
10.256 0.028 0.294 0.046 0.000
10.400 0.028 0.298 0.046 0.000
10.544 0.028 0.302 0.047 0.000
10.689 0.028 0.306 0.048 0.000
10.833 0.028 0.310 0.049 0.000
10.978 0.028 0.315 0.050 0.000
11.122 0.028 0.319 0.051 0.000
11.267 0.028 0.323 0.051 0.000
11.411 0.028 0.327 0.052 0.000
11.556 0.028 0.331 0.053 0.000
11.700 0.028 0.335 0.054 0.000
11.844 0.028 0.339 0.054 0.000
11.989 0.028 0.344 0.055 0.000
12.133 0.028 0.348 0.827 0.000
12.278 0.028 0.352 2.305 0.000
12.422 0.028 0.356 3.929 0.000
12.567 0.028 0.360 5.236 0.000
12.711 0.028 0.364 5.993 0.000
12.856 0.028 0.368 6.614 0.000
13.000 0.028 0.373 7.146 0.000
13.144 0.028 0.377 7.642 0.000
13.289 0.000 0.000 8.106 0.000
Lincoln Peak Short Plat 2/27/2026 2:37:39 PM Page 10
Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area:1.158
Total Impervious Area:0.036
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.413
Total Impervious Area:0.674
Flow Frequency Method:Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.044041
5 year 0.06812
10 year 0.08598
25 year 0.11062
50 year 0.130441
100 year 0.151494
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.019738
5 year 0.029055
10 year 0.036633
25 year 0.048012
50 year 0.057935
100 year 0.069219
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.060 0.015
1950 0.063 0.019
1951 0.083 0.047
1952 0.032 0.014
1953 0.024 0.017
1954 0.033 0.017
1955 0.053 0.017
1956 0.047 0.020
1957 0.045 0.017
1958 0.039 0.018
Lincoln Peak Short Plat 2/27/2026 2:38:19 PM Page 11
1959 0.034 0.015
1960 0.066 0.042
1961 0.035 0.019
1962 0.023 0.013
1963 0.034 0.017
1964 0.046 0.018
1965 0.037 0.020
1966 0.029 0.016
1967 0.071 0.018
1968 0.043 0.017
1969 0.041 0.016
1970 0.035 0.017
1971 0.040 0.018
1972 0.065 0.040
1973 0.031 0.020
1974 0.042 0.018
1975 0.054 0.016
1976 0.041 0.017
1977 0.016 0.014
1978 0.033 0.018
1979 0.024 0.013
1980 0.092 0.045
1981 0.030 0.017
1982 0.064 0.030
1983 0.046 0.018
1984 0.029 0.014
1985 0.017 0.015
1986 0.066 0.020
1987 0.063 0.036
1988 0.025 0.015
1989 0.022 0.015
1990 0.150 0.042
1991 0.088 0.038
1992 0.039 0.019
1993 0.032 0.014
1994 0.016 0.013
1995 0.042 0.019
1996 0.104 0.048
1997 0.076 0.049
1998 0.031 0.015
1999 0.095 0.038
2000 0.034 0.019
2001 0.019 0.012
2002 0.043 0.020
2003 0.064 0.016
2004 0.063 0.046
2005 0.047 0.017
2006 0.049 0.020
2007 0.118 0.064
2008 0.135 0.047
2009 0.069 0.020
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.1502 0.0637
2 0.1350 0.0487
3 0.1178 0.0475
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4 0.1040 0.0473
5 0.0947 0.0467
6 0.0918 0.0462
7 0.0881 0.0446
8 0.0830 0.0422
9 0.0758 0.0415
10 0.0710 0.0401
11 0.0688 0.0384
12 0.0662 0.0379
13 0.0657 0.0358
14 0.0654 0.0302
15 0.0645 0.0203
16 0.0636 0.0201
17 0.0635 0.0201
18 0.0634 0.0201
19 0.0631 0.0201
20 0.0599 0.0200
21 0.0540 0.0196
22 0.0534 0.0190
23 0.0493 0.0189
24 0.0475 0.0187
25 0.0474 0.0187
26 0.0463 0.0186
27 0.0462 0.0184
28 0.0454 0.0181
29 0.0434 0.0181
30 0.0434 0.0179
31 0.0423 0.0179
32 0.0422 0.0179
33 0.0412 0.0177
34 0.0407 0.0174
35 0.0397 0.0174
36 0.0388 0.0173
37 0.0386 0.0171
38 0.0374 0.0171
39 0.0354 0.0169
40 0.0349 0.0169
41 0.0341 0.0169
42 0.0340 0.0167
43 0.0336 0.0166
44 0.0330 0.0163
45 0.0330 0.0162
46 0.0321 0.0162
47 0.0317 0.0159
48 0.0311 0.0152
49 0.0306 0.0151
50 0.0298 0.0150
51 0.0294 0.0150
52 0.0294 0.0147
53 0.0252 0.0145
54 0.0245 0.0143
55 0.0237 0.0143
56 0.0228 0.0141
57 0.0216 0.0135
58 0.0192 0.0133
59 0.0166 0.0129
60 0.0162 0.0125
61 0.0161 0.0119
Lincoln Peak Short Plat 2/27/2026 2:38:19 PM Page 14
Duration Flows
The Facility PASSED
Flow(cfs)Predev Mit Percentage Pass/Fail
0.0220 11434 3525 30 Pass
0.0231 10158 3431 33 Pass
0.0242 9069 3335 36 Pass
0.0253 8117 3253 40 Pass
0.0264 7296 3136 42 Pass
0.0275 6545 3014 46 Pass
0.0286 5905 2890 48 Pass
0.0297 5341 2766 51 Pass
0.0308 4857 2618 53 Pass
0.0319 4395 2470 56 Pass
0.0330 3989 2282 57 Pass
0.0341 3638 2106 57 Pass
0.0352 3328 1939 58 Pass
0.0363 3037 1707 56 Pass
0.0374 2770 1476 53 Pass
0.0384 2530 1282 50 Pass
0.0395 2304 1147 49 Pass
0.0406 2084 1012 48 Pass
0.0417 1900 859 45 Pass
0.0428 1727 726 42 Pass
0.0439 1567 616 39 Pass
0.0450 1423 449 31 Pass
0.0461 1271 288 22 Pass
0.0472 1148 197 17 Pass
0.0483 1049 152 14 Pass
0.0494 961 133 13 Pass
0.0505 892 124 13 Pass
0.0516 834 114 13 Pass
0.0527 773 102 13 Pass
0.0538 722 63 8 Pass
0.0549 654 34 5 Pass
0.0560 588 9 1 Pass
0.0571 531 8 1 Pass
0.0582 483 5 1 Pass
0.0593 433 5 1 Pass
0.0604 384 4 1 Pass
0.0614 343 1 0 Pass
0.0625 309 1 0 Pass
0.0636 268 1 0 Pass
0.0647 237 0 0 Pass
0.0658 209 0 0 Pass
0.0669 180 0 0 Pass
0.0680 158 0 0 Pass
0.0691 141 0 0 Pass
0.0702 125 0 0 Pass
0.0713 111 0 0 Pass
0.0724 98 0 0 Pass
0.0735 87 0 0 Pass
0.0746 77 0 0 Pass
0.0757 66 0 0 Pass
0.0768 55 0 0 Pass
0.0779 46 0 0 Pass
0.0790 40 0 0 Pass
Lincoln Peak Short Plat 2/27/2026 2:38:19 PM Page 15
0.0801 35 0 0 Pass
0.0812 27 0 0 Pass
0.0823 24 0 0 Pass
0.0833 22 0 0 Pass
0.0844 19 0 0 Pass
0.0855 19 0 0 Pass
0.0866 17 0 0 Pass
0.0877 15 0 0 Pass
0.0888 12 0 0 Pass
0.0899 12 0 0 Pass
0.0910 11 0 0 Pass
0.0921 9 0 0 Pass
0.0932 8 0 0 Pass
0.0943 8 0 0 Pass
0.0954 7 0 0 Pass
0.0965 7 0 0 Pass
0.0976 7 0 0 Pass
0.0987 7 0 0 Pass
0.0998 7 0 0 Pass
0.1009 7 0 0 Pass
0.1020 7 0 0 Pass
0.1031 6 0 0 Pass
0.1042 5 0 0 Pass
0.1053 5 0 0 Pass
0.1063 5 0 0 Pass
0.1074 5 0 0 Pass
0.1085 5 0 0 Pass
0.1096 5 0 0 Pass
0.1107 5 0 0 Pass
0.1118 5 0 0 Pass
0.1129 5 0 0 Pass
0.1140 5 0 0 Pass
0.1151 5 0 0 Pass
0.1162 4 0 0 Pass
0.1173 4 0 0 Pass
0.1184 3 0 0 Pass
0.1195 3 0 0 Pass
0.1206 3 0 0 Pass
0.1217 3 0 0 Pass
0.1228 3 0 0 Pass
0.1239 3 0 0 Pass
0.1250 3 0 0 Pass
0.1261 3 0 0 Pass
0.1272 3 0 0 Pass
0.1283 3 0 0 Pass
0.1293 3 0 0 Pass
0.1304 3 0 0 Pass
Lincoln Peak Short Plat 2/27/2026 2:38:19 PM Page 16
Water Quality
Water Quality BMP Flow and Volume for POC #1
On-line facility volume:0 acre-feet
On-line facility target flow:0 cfs.
Adjusted for 15 min:0 cfs.
Off-line facility target flow:0 cfs.
Adjusted for 15 min:0 cfs.
Lincoln Peak Short Plat 2/27/2026 2:38:19 PM Page 17
POC 2
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #2
Total Pervious Area:0.007
Total Impervious Area:0.039
Mitigated Landuse Totals for POC #2
Total Pervious Area:0.025
Total Impervious Area:0.128
Flow Frequency Method:Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #2
Return Period Flow(cfs)
2 year 0.017409
5 year 0.0221
10 year 0.0253
25 year 0.029463
50 year 0.032657
100 year 0.035937
Flow Frequency Return Periods for Mitigated. POC #2
Return Period Flow(cfs)
2 year 0.05847
5 year 0.074948
10 year 0.086504
25 year 0.101874
50 year 0.113902
100 year 0.126439
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #2
Year Predeveloped Mitigated
1949 0.022 0.077
1950 0.023 0.076
1951 0.013 0.045
1952 0.011 0.038
1953 0.014 0.045
1954 0.014 0.047
1955 0.017 0.056
1956 0.016 0.051
1957 0.016 0.056
1958 0.014 0.047
1959 0.016 0.051
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1960 0.015 0.052
1961 0.015 0.049
1962 0.012 0.041
1963 0.015 0.051
1964 0.015 0.050
1965 0.017 0.058
1966 0.012 0.042
1967 0.020 0.069
1968 0.027 0.090
1969 0.016 0.053
1970 0.016 0.054
1971 0.019 0.065
1972 0.019 0.066
1973 0.013 0.041
1974 0.018 0.062
1975 0.019 0.063
1976 0.015 0.049
1977 0.014 0.049
1978 0.021 0.070
1979 0.026 0.085
1980 0.027 0.093
1981 0.017 0.056
1982 0.024 0.082
1983 0.020 0.066
1984 0.013 0.043
1985 0.016 0.055
1986 0.014 0.048
1987 0.022 0.074
1988 0.015 0.049
1989 0.023 0.077
1990 0.028 0.100
1991 0.025 0.086
1992 0.013 0.044
1993 0.016 0.053
1994 0.014 0.046
1995 0.015 0.051
1996 0.020 0.067
1997 0.015 0.053
1998 0.016 0.054
1999 0.035 0.120
2000 0.016 0.055
2001 0.020 0.066
2002 0.020 0.070
2003 0.021 0.071
2004 0.034 0.116
2005 0.013 0.045
2006 0.012 0.043
2007 0.032 0.109
2008 0.023 0.080
2009 0.025 0.081
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #2
Rank Predeveloped Mitigated
1 0.0346 0.1199
2 0.0337 0.1158
3 0.0317 0.1095
4 0.0282 0.1003
Lincoln Peak Short Plat 2/27/2026 2:38:57 PM Page 19
5 0.0269 0.0930
6 0.0266 0.0902
7 0.0256 0.0865
8 0.0247 0.0846
9 0.0246 0.0817
10 0.0238 0.0808
11 0.0234 0.0800
12 0.0229 0.0768
13 0.0228 0.0765
14 0.0223 0.0758
15 0.0221 0.0743
16 0.0212 0.0712
17 0.0208 0.0703
18 0.0205 0.0700
19 0.0200 0.0690
20 0.0199 0.0672
21 0.0197 0.0664
22 0.0196 0.0662
23 0.0193 0.0657
24 0.0193 0.0654
25 0.0191 0.0626
26 0.0180 0.0616
27 0.0171 0.0581
28 0.0166 0.0562
29 0.0166 0.0561
30 0.0164 0.0559
31 0.0163 0.0550
32 0.0162 0.0547
33 0.0162 0.0541
34 0.0161 0.0537
35 0.0159 0.0535
36 0.0157 0.0532
37 0.0157 0.0526
38 0.0156 0.0515
39 0.0154 0.0515
40 0.0152 0.0512
41 0.0151 0.0511
42 0.0150 0.0508
43 0.0150 0.0495
44 0.0149 0.0493
45 0.0145 0.0491
46 0.0145 0.0491
47 0.0144 0.0485
48 0.0142 0.0476
49 0.0142 0.0474
50 0.0141 0.0472
51 0.0140 0.0463
52 0.0135 0.0453
53 0.0133 0.0448
54 0.0132 0.0446
55 0.0129 0.0437
56 0.0128 0.0428
57 0.0126 0.0425
58 0.0124 0.0415
59 0.0124 0.0415
60 0.0124 0.0412
61 0.0113 0.0378
Lincoln Peak Short Plat 2/27/2026 2:38:57 PM Page 24
Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
Lincoln Peak Short Plat 2/27/2026 2:38:57 PM Page 25
Appendix
Predeveloped Schematic
Lincoln Peak Short Plat 2/27/2026 2:38:59 PM Page 26
Mitigated Schematic