HomeMy WebLinkAboutSite Certifications - 07/08/2010June 14, 2010
Mr. Basil Hamdan
City of Fort Collins-Utilities
Stormwater
700 Wood Street
Fort Collins, CO 80522
RE: Drainage Certification
SE Community BMX Track ~
Dear Basil:
INTERWEST co ·NSULTING GROUP ._----
Please accept this letter and the attached drawing as the Drainage Certification for the above
project. King Surveyors , Inc. surveyed the storm drainage and porous landscape detention for
the SE Community BMX Track. The results of this survey indicate that the porous landscape
detention pond has adequate surface area (1350 sf) and the pond outlet structure has been
constructed in substantial conformance with the approved design.
This letter certifies that these facilities are in substantial conformance with the approved plans .
Enclosed with this letter you will find the As-Built Survey drawing. We therefore request that
the facilities listed above be deemed acceptable to the City of Fort Collins.
If you should have any questions or comments , please contact me at (970) 674-3300 Ext. 102 .
Thank you for your assistance.
Sincerely,
28
Michael Oberlander, P.E., LEED AP \ ... ff l t'{ ···-···· Attachments
12 l 8 WEST ASH , SUITE C • WINDSOR , COLORADO 80550
TEL. 970.674.3300 • FAX. 970 674 .3 303
VERTICAL DATUM:
BENCHMARK: CITY OF FORT COLLINS BENCHMARK 3-02.
ELEVATION=4915.40
HORIZONTAL DATUM :
COLORADO STATE PLANE COORDINATES NAO 83(1992) DATUM .
HORIZONTAL CONTROL BASED UPON TRIMBLE VRS NETWORK .
NOTE:
1. THIS DRAWING IS AT MODIFIED STATE PLANE. TO REDUCE TO STA TE
PLANE COORDINATES, SCALE AT .99973537 (1 .00026470) ABOUT THE
ORIGIN 0,0 .
2 . THIS AUTOCAD DRAWING CONTAINS INFORMATION THAT IS NOT
VISIBLE ON THE PLOTTED COPY . TO OBTAIN ALL 'THE INFORMATION THAT
IS AVAILABLE IN THIS DRAWING, ALL THE AUTOCAD LAYERS MUST BE
TURNED ON AND THAWED .
3. THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND
UTILITIES ARE APPROXIMATE WHEN SHOWN ON THESE DRAWINGS . IT
SHALL BE THE RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE
EXISTENCE OF ALL UNDERGROUND UTILITIES IN THE AREA OF THE WORK
BEFORE COMMENCING NEW CONSTRUCTION. THE CONTRACTOR SHALL BE
RESPONSIBLE FOR LOCATING ALL UNDERGROUND UTILITIES AND SHALL
BE RESPONSIBLE FOR ALL UNKNOWN UNDERGROUND UTILITIES.
40' 20' 0 40'
1" = 40'
12" RCP PIPE -""' f RIP RAP WE IR
AREA INLET FL=4898.87 -_-_-,.~a;; _-___-_ _ _ ,, _ _ [RIP RAP WEIR ___ -!RIP RAP W~l:_:.:::~~9:~,
TOP GRATE=4899 .07 ..-"0 ____ ------_ -4902----,, ,.., 1 ,
INV E 4895 51 ,.,... .,,,... A9v ....._, ......_ ....._ _ ------_ -- - -- --..,.,,. _,,.,.. ,,,,. , = . ,... ----- --- - -.... .... -----_....,----------______ ----- ----/ / ,:;{' INV SE=4893 .19 ,./'-------------'-. --.... -~---_;:-;-_______ -.--:..._ .... _--__ -----,,"r,.~-----
CENTER INV=4892.59, "'..._ __ 4901 _ _ _ ,, ---. ----4900---..-..--.. ------ --1 , ? p' - - - - -- -::: ...... -...... ...... -------_.. .,,,... -......................... -4 900--.-- - - - -_.. .,,,,... 4-'?
I"-.-. ---./ -. -. --:::: :::: ;90]--_-_-_----:-_ - - --..-----------:_ :_;..::_:_ ____ ,.:-.;.;~----_
--./ I / ~-:::: ......, - - - - -
It(,~' ----.:::--.. 12" RCP PIPE
-..
\ \ ....... ...... ...... --::: --/ _,,__ __ ---,:_ ~'o ---/ / l FL= 4898. 98
-.. --0 --------------:::-4 900--i --------4 900:: ' , ' -.. '--.. \
...... ...... " ......
'-.., :-.. "', 1 UNDER DRAIN
-...... __ , ,,.'/ / CLEANOUT
0 r---.,,,.",,,,. --......,_..
\____ 12" RCP W /
FL=4891.58
FES
,..._
DAT[:
Ol/10/10
Fl.£ NAM£:
201 ---
04(0<£0 BY:
RE
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Design Procedure Form : Porous Landscape Detention (PLD )
Designer: Erika Schneider
Company: lnterwest Con sultin g Group
Date: J u ne 14, 2010
Pr oject: BMX
Location: City of Fort Collins
1. Basin Storage Volume
( 10 = 100% if all paved and roofed areas u/s of PLO) 1. = 40.00 %
A) Tributary Area's Imperviousness Ratio (i = 10 / 100 ) i= 0.40
B) Contributing Watershed Area Includ ing the PLO (Area) Area= 70 ,000 square feet
C) Water Quality Capture Volume (WQCV) WQCV= 0.14 watershed inches
fWQCV = 0 .8 • /0 .91 • 13 -1.19 • 12 + 0. 78 • Ill
D) Design Volume : Vol PlD = (WQCV / 12) • Area Vol= 839 cubic feet
2 . PLO Surface Area (APLD l and Average Depth (davl APLO = 850 square feet
(from 839 .25 square feet to 1678 .51 square feet)
(d •• : =(Vol/ APLol , Min=0 .5', Max=1 .0') d av = 0 .99 feet
3. Draining of PLO (Check A, or B, o r C, answer D) Infiltration to Subgrade w ith Permeable
Based on answers to 3A through 3D , check the appropriate method Membrane : 3(C) checked and 3(E) = no
A) Check box if subgrade is heavy or expansive clay ~ Underdrain with Impermeable
B) Check box if subgrade is silty or clayey sand Liner: 3(A) checked or 3(E) = yes
C) Check box if subgrade is well-draining soil
X Underdrain with Woven Geotextile Fabric (See note 1 ):
D) Check box if underdrains are not desirable or I I 3(B) checked and 3(E) = no
if underdrains are not feasible at this site.
16-Mil. Impermeable Membrane with No Underdrain :
E) Does tributary catchment contain land uses that may have 3(D) checked -Evapotranspiration only
petroleum products , greases , or other chem icals
present , such as gas station , ~es no Other:
hardware store , restaurant , etc .? I I X I
4. Sand /Peat Mix and Gravel Subbase (See Figure PLD-1)
A) Heavy or Expansive Clay (NRCS Group D Soils) Present; 18" Minimum Depth Sand-Peat M ix w ith 8" Grave l Layer. 16-Mil.
Perforated HOPE Underdrain Used . Impermeable Liner and a 3" to 4" Perforated HOPE Underdrain .
B) Silty or Clayey Sand (NRCS Group C Soils) Present;
Perforated HOPE Underdrain Used . X 18" Minimum Depth Sand-Peat Mix with 8" Gravel Layer and a
3" to 4" Perforated HOPE Underdrain w/ Non-Woven Pemeable Membrane .
C) No Potential For Contamination And Well-Draining 18" Minimum Depth Sand-Peat M ix with Non-Woven
(NRCS Group A or B Soils) Are Present; Underdrains Elliminated. Pemeable Membrane and No Underdra in (Direct Infi ltration).
D) Underdrains Are Not Desirable Or Are Not Feasible At This Site . 18" Minimum Depth Sand-Peat Mix w ith An Additional 18"
Minimum Layer Sand-Peat Mix or Sand-Class 'A' Compost Bottom
Layer (Total Sand-Peat Depth of 36"). 16-Mil. Impermeable Liner Used .
E) Other: Other:
Notes : 1) Woven geotext1le fabric shall meet ASTM D4751 -AOS U.S . Std . Se1ve #50 to #70 , ASTM D4633 min . trapezoidal tear strength 100 x
60 lbs , min . COE specified open area of 4%.
2) It is critical that vegetation planting be in accordance with US DCM V3 guidelines for PLD's
BMX Track Site UD-BMP _2 .1 .xls , PLO 6/14/2010 , 1 0 :32 AM