HomeMy WebLinkAboutLot Certifications - 01/20/2022
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
January 12, 2022
Dan Mogen, EI, CFM
Development Review Engineer
Stormwater Engineering & Development Review Division
City of Fort Collins Utilities
dmogen@fcgov.com
Re: Final Drainage Certification Letter for 232 Lyons Street Proposed Garage
Dear Dan,
This letter serves as Final drainage certification for the constructed garage at 232 Lyons Street along
with the following documents requested by the city to complete the inspections and obtain a Certificate
of Occupancy.
The proposed garage was built in substantial accordance with the approved site plan and building
permit. Gutters were installed on the north and south side of the garage with the downspouts on the
west end of the garage. The downspouts will release into water barrels on the west end and into a hose
that conveys roof runoff to a constructed rain garden in the yard. The rain garden was built in
substantial compliance with the approved design.
The plan does indeed call for specific hydrophilic plants to be present in the rain garden, and this
remains to be the intent. Unfortunately, the garage construction ran too late in the season (late fall –
early winter) to plant them this year. In addition to the mulch that is covering the rain garden presently,
the plan remains to plant these bushes/shrubs in the spring. The planting will be completed in the spring
of this year
The plan does indeed call for a slope toward the center of the garden (toward the trench) of
“approximately” 12 inches. In looking at the Standard Cross Section on the detail you provided,
however, it states that “the maximum allowable ponding depth is 12 inches from the top of the
mulch”. Unless I’m reading this incorrectly, this means that the ponding depth must be “up to” 12
inches. The ponding depth in the constructed rain garden is just under 9 inches and is indeed sloped
toward the center from the edges. Jason provided you a photo of this in an email dated 12/30/2021
As for the 4” pipe to be utilized to convey runoff from garage to rain garden, this ultimately proved
unfeasible. Such reasons included, but were not limited to, the existing slope (or lack thereof) of the
property, the existing structures on the property (need to bore under existing patio or garage
foundation from north side of garage), and the inability to monitor freezing of runoff in a buried pipe
during colder months. As a result, the plan to utilize hoses to convey runoff from rain barrels to rain
garden was devised. Although this will require a more active management on the owners part, it is
believed that it will also be a more effective strategy. In regard to your question of whether the hoses
will remain in place, that remains to be determined. One advantage to the hose option is that
adjustments can be made to account for the variability of the seasonal weather (i.e. summer storms,
winter snows, freeze/thaw cycles, etc.).
Reclamation Village
Lot 25
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
I understand your concern with any deviation from the original plan, but I want to assure you that the
overall goal has not changed in any way. The principal objective of keeping roof runoff away from the
alley and/or adjacent properties has been accomplished. Although the final design does contain minor
deviations from the original plan, it continues to accomplish this primary objective. In fact, I would
argue that the current plan accomplishes this objective more effectively and will in fact be easier to
maintain over time to continue to accomplish the goal.
The runoff from the proposed garage will not have any adverse impact on adjoining or downstream
properties. I stand by my original letter and provide this additional letter at the request of the City of
Fort Collins Stormwater Utility. Please feel free to contact me if you have any questions.
Sincerely
Mark Oberschmidt, PE
35721
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 1: south side of garage
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 2: valve and hose to rain garden
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 3: looking SE towards rain garden
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 4: rain garden
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 5: rain garden looking east
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 6: west side of garage
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 7: rain garden trench
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 8: trench backfilled
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 9: rain garden trench measurement
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 10: trench dug
235 Lyons Street moberschmidt@gmail.com (970) 980 3557
Figure 11: aggregate bedding