Northlake Wood-CS030505
MEMORANDUM
FROM THE
DEPARTMENT OF ENGINEERING
To:
Greg Jones, Chief Building Official
Kenneth M. Griff'm, P.E., Director of EngineeringlPublic Works y-:,
May S, 2003
Northlake Woodlands, Lot 22 Block 2
From:
Date:
RE:
The N orthlake Woodlands plat was filed in 1974 and on the face of the plat there were finished
floor requirements associated with the creek that meanders through the subdivision from north to
south. On Lot 22 Block 2 the minimum finished floor was set at 492.0. I have researched our
files and have been unable to ascertain the basis for the finished floor of 492. However, I have
reviewed our Citywide Stormwater Management Study from January 1991 to determine what the
I DO-year water surface would be in a fully developed condition adjacent to Lot 22.
The creek adjacent to Lot 22 is a tributary of Grapevine Creek and is named Stream G-4. The
ultimate flood study from January 1991 shows the water surface elevation at the downstream side
of Bethel School Road at approximately 493. However, this water surface drops off dramatically
as you proceed south from Bethel School Road. The water surface drops to about 488 within the
first 50 feet. In looking at the site plan for the house location, the house is located approximately
50 south of Bethel School Road. Therefore, the elevation for the I DO-year water surface
coinciding with the front of the house is approximately 488. Because the January 1991
Stormwater Management Study information is more current than the 1974 information, it is my
opinion that the FFE for the proposed house at 413 E Bethel School Road could be set at 489.
The 489 elevation is derived from our Ordinances which state that FFE's have to be 2 feet above
the I DO-year existing floodplain elevation or one foot above the ultimate floodplain elevation as
shown in the Stormwater Management Study of January 1991. This creek is not represented on
the Floodplain Management maps as being within the floodplain; therefore the only document that
addresses the finished floor is the Stormwater Management Study. Being one foot above the
ultimate I DO-year water surface elevation at the beginning of the house places the minimum FFE
at 489. This is the 488 water surface elevation plus one foot.
In reviewing the grading plan for the property, the natural ground elevation around the structure
ranges from 491 to 497 in the first 50 feet from Bethel School Road back to the house. This
bermed area leads to the entrance to the basement level. The I DO-year water surface elevation as
you proceed further south toward the rear of the house is at approximately 487. Therefore,
maintaining an FFE of 489 keeps you above the I DO-year water surface anywhere along the
property adjacent to the structure.
"CITY OF COPPELL ENGINEERING - EXCELLENCE BY DESIGN"
I have attached to this memo a Hold Harmless letter from the prospective homeowners indicating
that they are fully aware that the finished floor elevation has been administratively lowered based
on the best information available, and that in the event there is any flooding of the property due to
rising waters, the City is not liable for damages. In addition to this information, I've also
discussed the purchase of flood insurance with the prospective homeowner. While the property
itself is not within the floodplain, the City of Coppell participates in the flood insurance program
so any property owner within the corporate limits of Coppell is eligible to purchase flood
msurance.
In summary, it is my opinion that the finished floor elevation for Lot 22 Block 2 (413 E.
Bethel School Rd.) can be adjusted down to 489 without any adverse impact to the property.
"CITY OF COPPELL ENGINEERING - EXCELLENCE BY DESIGN"
THE'CITY.OF
COPPELL
P.O. Box 478
255 Parkway Blvd
Coppell. TX 75019
Phone: (972)304-3679
Fax: (972)304-3570
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ENGINEERING DEPARTMENT
FAX COVER SHEET
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Fax: 972.313. CfZS-
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May 5, 2003
Mr. Ken Griffin
Director of Engineering and Public Works
City of Coppell
255 Parkway Blvd.
Coppell, TX 75019
Dear Mr. Griffin,
Thank you for meeting with me Friday to discuss the situation with our
lot at 41 3 E. Bethel School Road. I appreciated your investigating the
issue of minimum floor level. I understand the reason for the change and
support the compromise of 489 feet above sea level. My husband and I
agree to not hold the City of Coppellliable in the event of any flooding
encountered due to this change. I am grateful for your assistance in this
matter.
Sincerely,
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