HomeMy WebLinkAboutLot Certifications - 03/13/2014I
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Robinson.
319 South Grant
Bill Scott
4816 Chippendale Drive
Fort Collins, Colorado 80526
ring, inc
ollins, Colorado 890521
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City of Fort Collins Building Department
Dear Sirs.
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Match 13,2014
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Our office was asked to assess the affect to existing drainage flow on the property at, 4816 Chippendale Drive, Fort
Collins as a result of the proposed addition.
I have reviewed the drainage basin topographic map and the Ridge development Inventory maps from the city.
Initially the city thought this property crested the ridge between two basins. A site indicated the dividing lint
between the two basins was several hundred feet north and east of the property. I reexamined the maps and
confirmed the bourdary Hine be th
i tween e two basins is clearly north of the property. All water applied to this
property must drain south into the Fossil Creek drainage. The property is.gently sloped from the northeast boundary
to the south west boundary. I have attached, printouts from ;the pity T* I with the .property .indicated.
The planned garage adds structureIL the southeast ofthe 'ek - existing home. The I northe . ast garage wal I I will be parallel
the
e north east property line with the southeast garage wall parallel to the'.southeast property line. There -should be
approximately 16' and 20' between the walls and the respective property lines. Roof watcr.from the northwest
garage roof exposure will be shed to the northwest side of the garage. T The roof water and accurnuiated surface water
can be directed around the, east com er of the garage t6 drain to the southeast or direcied north west around the
existing home- The prppeity'is relatively flat but there exists sufficient slope to drain the drain the water away form
the garage then direct it around - thegarage, Drainage could, beimproved by installing a drain tile parallel to the-,
northeast garage wall, transferring the water around the east end of the garage dischargingtowards the southwest
property line. *Attached are the approximated existftdrainag d modified drainage plans,._ drainage an
The development has a 25.6% limit of impervious surf -aces to soil.surfaces ratio. The lot is 150 ft by 230,11 which -is
34,500 fe. The existing home footprint appears to bee -approximately 2300 fe. The existing driveway appears to be
approximaiely 3760, fe. 'Me,existing pr&iousto impervious'suiface ratio is 6066 WF 3000 fe,resultim'*
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approximate ratio of 17.5%.
With his addition as planned, it adds BM ft�-to, the home footprint, or 4635 f? total for the home andiddition. The
addition overlaps the current driveway by 1203 fe bufthe far right garage door would require about 1-20f? added -
drive surface for access. The new driveway would be approximately 26774e. The new previous to impervious
ratio is 7312 fe / 34506 fl2resulting in an approxiniatexatio of approximately 20.2%. 'Mat value is still well below
the 25.6% ratio limit noted.
hi summary, the property drains its entire surface area, including roof structure to the south west property boundary.
The added structure will change the drainage adjacent the home and garage, but the overall drainage off the property
will not be changed.
Based on the findings above, we would like to request a variance to the onsite detention and drainage report
requirements when adding over 1000, Wof new impervious area such that no additional retention areas be required.
If there are any questions, please call. OO RE
Sincerely, Q�P�Y C.q��ST
C
Geoff Robinson, PE �c MAR 13 2014
Civil / Structural Engineer s`S��NA1 E
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