HomeMy WebLinkAboutDrainage Reports - 08/10/2016Ir
FORBES ENGINEERING
Full Service Civil & Structural Engineering
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July 28, 2016 LA 20, W, q;si'
Dan Mogen
City of Fort Collins
Stormwater Engineering Crut_ sobb� « 444-
700 Wood Street�5�:�.�<9
Fort Collins, CO 80521
RE: Grading & drainage memo for site improvements
Parcel #97014-05-020
729 Martinez Street
Fort Collins, CO 80521
Mr. Mogen,
This letter and attached exhibit are to serve as a drainage memo for the above
referenced single family residential property. The property is located along the
west side of Martinez Street and has an approximate lot area of 6288 square feet.
The property is vacant & covered with native vegetation but for a small patch of
concrete and asphalt (approximately 300 square feet). The surrounding
neighborhood to the north, south and east are single family residential lots and the
land to the west is an undeveloped field.
The existing spot elevations for the proposed grading & drainage plan are based, .-
on survey data provided by Centerline Surveying LLC, dated September 11, 2015.
The proposed improvements include a 1680 square foot pre -manufactured home
and a small amount of concrete flatwork (see attached grading plan). The existing
asphalt & concrete flatwork will be removed and it is the intent of the builder to
maintain the natural lot grade which flows towards the east.
Approximately 2331 square feet of impervious area will be added to the property.
The existing percent impervious has been calculated at 13.4% and the proposed
percent impervious has been calculated at 35.4%.
The property is located within the Poudre River 500-year floodplain and the
historic storm water runoff presently is directed towards the east and into the street
gutter system of Martinez Street. The finish floor elevation has been established at
approximately 20" above existing grade. Historic drainage patterns will be
maintained (see grading & drainage plan) with a small change on the west portion
of the property which will contain the spoil pile from the crawlspace excavation
(any additional soil not used for the berm will be transported off the property). A
swale on the south side of the home will be constructed to divert storm water run-
off towards the west and towards the east with a high -point located approximately
20' east of the west gable end of the home.
Any necessary erosion control measures will be provided at the time of
construction including, but not limited to, perimeter silt fencing and a vehicle
tracking control mat if necessary.
It is my conclusion that with proper construction practice and observance to the set
finish floor elevation, no adverse affects to the site or to the surrounding
properties are anticipated from the proposed improvement of this site.
9
729 MARTINEZ ST
FT COLLINS, CO
COUNTY LAND & HOMES LLC
PERCENT IMPERVIOUS VALUES
BASED ON THE FOLLOWING
Character
of Surface
Streets
Paved
Gravel
Walks
Roofs
Lawns
EXISTING CONDITIONS
AL(Lawns) AC (Cone)
Sq Ft Sq Ft
6263 169
Percent
Impervious
100
40
90
90
0
AR(Roofs)
Sq Ft
0
Percent Impervious 13.4%
PROPOSED
CONDITIONS
AL (Lawns)
AC (Cone) AR(Roofs)
Sq Ft
Sq Ft Sq Ft
4014
210 1680
Percent Impervious 35.4%
FORBES ENGINEERING
Project #: 2605
By: KEF
Date: 6-28-16
NOTE; THE TOTAL AREA & PERCENT
IMPERVIOUS CALCULATIONS INCLUDE
LANDSCAPING AND ASPHALT WITHIN
3i OF THE ROAD ROW
AG(Gravel)
Sq Ft
0
AG(Pavement)
Sq Ft
816
AG(Gravel) AG(Pavement)
Sq Ft Sq Ft
800 544
At (Total)
Sq Ft
7248
At (Total)
Sq Ft
7248
Page 1
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14 ' epl i
I N 00*59*070 E
W. 1 7.
.WI.
SPOIL PILE, SIZE DETERMINED \
FROM CRAWLSPACE EXCAVATION,
(TOP OF BERM ELEVATION NOT
TO EXCEED 57.5) '
MAINTAIN MIN.
'
SWALE SLOPE
N
AT 1.33%
SOUTH SIDE SWALE SLOPED
Ln 0 cD
® 1.5% TOWARDS THE FRONT 5ya.,
tov
-4&
r
BACK, HIGH POINT LOCATED NP
$
DAPPROXIMATELY
20' EAST OFWEST
END OF HOMEZ
Z
13
m
m
�31
Z
LOT 21
T� 733 MARTINEZ
STREET
LOT 19
725 MARTINEZ
STREET
20' WIDE RECYCLED
ASPHALT DRIVEWAY,
SLOPE AS NEEDED
'955.0 • -�_ _ 4r��•- 'r I i
SITE BENCHMARK T W
SE PROP CORNER
ELEV. ®4954.60 4ss4.s _ , �sj---''�e+•�
4954.0 •- S-59� 2 1W .------''i = (s40
495.15 ---- - I `�- -- j '�' 07J
EOA-------------------�----
ROAD CL
SITE BENCHMARK
LOCATION: SE PROP CORNER
TOP OF #4 REBAR
ELEVATION: 4954.60
4s515 ---- EOA
-MARTINEZ ST.
--- T3� -- ROAD CL
l
FLOW LINE OF STREET
GRADING & DRAINAGE PLAN
SCALE In = 20'
"• °T LEGEND
E.Fp',�+
/ R�F� •�� EXISTING GRADE 69.61
PROPOSED GRADE x — =9-6
0
DOWNSPOUT ®0S
SLOPE DIRECTION —�
4--n d-W
PROPERTY INFORMATION
OWNER: ALEJANDRO & MARIA GOMEZ
4412 E. MULBERRY ST
FORT COLLINS, CO 80524
ADDRESS: 729 MARTINEZ ST.
FORT COWNS, CO 80524
LEGAL: LOT 20. ALTA VISTA
PARCEL #: 97014-05-020
FOR B E S ENGINEERING
2908 CHERLY STREET,
CLIENT &HOMES LAND C
PREPARED BY
KEl/lN FORBES
PROJECT' 729 MARTINEZ ST
DRAWN.
DATE
Ft. Collins, Colorado 80524
Tele: (970) 295-4874
FT COLLINS, CO
KEF
6-28-16
SHEET T/lLE.• GRADING &
PROJECT
DWG
FWL SMrQ- GMEDWr, MFMC MD DEN&V
aWVS7REX7UR1L F0L#"n A% MW: MINPAL PraaM
DRAINAGE PLAN
16-2605
2605—EX