HomeMy WebLinkAboutRS_BFE_Letter_Harmsen_15022_135thAveSE_250106_v1
LAND SURVEYING ● LAND USE PLANNING ● CIVIL ENGINEERING ● ENVIRONMENTAL SERVICES
EVERETT
2822 Colby Ave, Suite 300
Everett, WA 98201
425-252-1884
MOUNT VERNON
603 South First Street
Mount Vernon, WA 98273
360-336-9199
www.HarmsenLLC.com
Ferose Babu
15022 135th Ave SE
Renton, WA 98058
TPN 2223059057
August 19, 2025
25HRM0215
(917) 423-5237
ferose2@gmail.com
Base Flood Elevation (BFE) Calculation at 15022 135th Ave SE, Renton
per current Cedar River FIS dated August 19, 2020 (NAVD 1988):
Cross Section River Feet Distance BFE
AM 21,843 77.6’
104 ft
North Side of Residence 21,947 77.8’
28 ft
North Side of Garage 21,975 77.9’
533 ft
AN 22,508 78.9’
Conclusion
The distance between cross-sections AM and AN is 665 feet.
According to the Flood Profile, the slope is constant between AM and AN.
By interpolation, the BFE at the North side (upstream) of the residence is 77.8’ and the BFE at
the North side of the garage is 77.9’
Discussion
The analyzed structures are primarily situate within the Zone AE (riverine) Flood Hazard Area;
only the western faces of the structures lie within the Zone AO (1’ ponding) Flood Hazard Area.
Lowest Adjacent Grade at the residence is the NW corner, elevation of 78.3’; this is 0.5’ above
the BFE. Lowest Adjacent Grade at the garage is the NE corner, elevation of 78.3’; this is 0.4’
above the BFE.
Per section 4.1 of the MT-1 Technical Guidance No.65, “if a subject is in more than one flood
zone, as mapped on the effective FIRM, the more hazardous zone is used in making a
determination” (FEMA 2024): due to the expected water velocity in Zone AE and the distance of
the site from the origin of the Zone AO backwater ponding, it is my opinion that the Zone AE
represents the higher hazard at this property.
25HRM0215 Babu 8/19/2025
PAGE 2 OF 2
Per section 4.7 of the MT-1 Technical Guidance, the following elements were considered in this
determination:
• The extent to which the Zone AO flooding will inundate the structures is limited to only
the west faces of the structures.
• The subject of this determination is located at the furthest extent of the Zone AO in the
area.
• The nature of the Zone AO appears to be a backwater area, where the Cedar River back-
flows through a low point in the terrain, down-gradient from the area in question.
• The street in front of the structures is 2-feet or more below adjacent grades of the
structures in the AO Zone.
• The projected depth of flooding in the AO Zone is 1-foot, and no velocity is defined.
• The LAGs of the subject structures is above the Zone AE Base Flood Elevation.
The LAGs of all structures on the property (residence and detached garage) are located above
the respective BFEs; minimal amounts of fill was emplaced only at the westerly face of the
residence. HAG at the garage is nearest to the Zone AE hazard, and 0.7’ above the BFE; HAG at
the residence is nearest to the Zone AE hazard, and 1.3’ above the BFE.
We at Harmsen appreciate your business, thank you. Please feel free to reach out if you have
any questions regarding your Elevation Certificate, or the information in this letter.
Erynn O. Sullivan │ CFM No. US-20-11712
USE OF THIS LETTER
These Calculations were prepared to determine if a dwelling is located within the FEMA Special Flood Hazard Area,
as defined by 21A.24.200 King County Code and to aid in compliance with applicable statute(s). We have not
attempted to investigate anything other than readily-observable conditions at your site.
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-122.159 47.468 Degrees
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FEMA's National Flood Hazard Layer (NFHL) Viewer with W
15022 135th Ave SE, Renton, WA
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15022 135th Ave SE, Renton
SECTION MEAN WITHOUT WITH
AREA VELOCITY FLOODWAY FLOODWAY
(FEET)(SQ.FEET) (FEET/SEC.) (FEET NAVD) (FEET NAVD) (FEET NAVD) (FEET)
12,1731 120 1,235 8.7 48.3 48.3 49.0 0.7
12,7411 95 1,183 11.5 48.7 48.7 49.5 0.8
13,1871 125 1,297 9.0 50.8 50.8 51.3 0.5
13,7261 92 1,514 12.0 51.3 51.3 51.8 0.5
14,4671 113 1,458 8.7 54.1 54.1 54.5 0.4
14,4811 113 1,458 8.7 54.2 54.2 54.5 0.3
15,6041 100 1,202 9.4 58.6 58.6 59.2 0.6
16,5761 132 1,267 7.9 61.3 61.3 62.0 0.7
18,0831 124 1,460 10.9 64.0 64.0 64.7 0.7
19,2811 115 1,150 10.2 68.2 68.2 68.5 0.3
19,6921 139 1,181 9.6 69.5 69.5 70.0 0.5
20,6701 125 1,151 9.0 74.4 74.4 75.1 0.7
21,8431 128 1,204 8.6 77.6 77.6 78.6 1.0
22,5081 94 1,129 11.8 78.9 78.9 79.7 0.8
23,0801 201 1,772 5.8 82.4 82.6 83.1 0.5
23,4921 124 2,108 10.5 82.6 82.4 82.8 0.4
24,1201 304 2,341 4.9 85.5 85.5 86.3 0.8
24,8751 675 2,407 3.5 87.2 87.2 87.8 0.6
26,2191 97 2,036 10.4 91.6 91.6 91.8 0.2
26,8481 628 2,258 3.9 96.5 96.5 96.8 0.3
27,2591 825 2,481 2.7 97.9 97.9 98.9 1.0
27,8331 645 2,293 3.5 98.9 98.9 99.9 1.0
5902 814 3,790 3.1 102.1 102.1 102.5 0.4
1,0712 760 2,713 4.3 103.0 103.0 103.4 0.4
1,5832 427 2,548 4.6 104.3 104.3 104.5 0.2
2,3472 207 1,081 10.8 106.6 106.6 106.6 0.0
TA
B
L
E
6
AND INCORPORATED AREAS
WIDTH REGULATORY
KING COUNTY, WA
1
INCREASE
FEDERAL EMERGENCY MANAGEMENT AGENCY
2
Feet above mouth
Thousands of feet above 590 feet downstream of 149th Avenue S.E.
AB
AC
1-PERCENT-ANNUAL-CHANCE FLOOD
WATER SURFACE ELEVATIONFLOODWAYFLOODING SOURCE
CROSS SECTION DISTANCE
CEDAR RIVER
FLOODWAY DATA
CEDAR RIVER
AD
AE
AF
AG
AH
AI
AR
AS
AJ
AK
AL
AM
AN
AO
AT
AU
AP
AQ
AZ
AA
AV
AW
AX
AY
190
25P