HomeMy WebLinkAboutRIGDEN FARM, 5TH FILING, TRACT I, SETTLERS GREEN - PDP - 56-98J - CORRESPONDENCE - REVISIONS3. If the plan is to not disturb the existing reseeded/mulched areas, please add a note to
the plan indicating that it is not to be disturbed, otherwise the area will need to be
reseeded and mulched (your calculations won't hold up).
RESPONSE: SINCE ALMOST THE ENTIRE SITE WILL REQUIRE REGRADING,
A NEW COST HAS BEEN CALCULATED FOR SURETY (SEE TABLE 4 IN
DRAINAGE REPORT).
Please refer to the redlined plans and report for additional comments.
RESPONSE: ADDITIONAL POINTS HAVE BEEN ADDED ON THE GRADING
PLAN; ALSO, GRADES ALL ARE LESS THAN 4:1 NOW. RETAINING WALLS
HAVE BEEN REMOVED, AND, IF NEEDED, WILL BE A PART OF INDIVIDUAL
BUILDING PERMITS. GRASS -PAVED PARKING AREAS HAVE BEEN
REMOVED.
8. Please include C factors and Q2 values on the drainage summary table. Also, please
clarify where the carryover 2 cfs into Basin T 1 is from. If it is carryover from the
inlet in Basin T2, please show more clearly the capacity calculation of this inlet
versus the total runoff to the inlet. As a suggestion, the summary tables shown on the
plans would be easier to read if only the most important information was included
(i.e., current area, C, Q2, Q100).
RESPONSE: TABLE 1 SHOWS MINOR STORM FLOWS. TABLE 2 SHOWS C-
FACTORS. TABLE 3 INCLUDES AN EXPLANATION OF THE RF#1
CARRYOVER, AND THE IMPORTANT HYDROLOGY INFORMATION.
9. Please include more detailed calculations to justify the inlet capacity. The tables and
nomograph provided are hard to follow and without any explanation.
RESPONSE: COMPUTER PROGRAM DATA HAS BEEN ATTACHED TO THE
REPORT SHOWING INLET CAPACITY DATA.
10. Please include a note on the plat stating that Tracts A and B are to be drainage
easements.
RESPONSE: THIS WAS DONE ON THE PLAT.
Erosion/Sediment Control Comments:
1. The plan shows silt fencing crossing roadways, how does one do this? And if you
eliminate it across the roadways, how do you plan to protect against sediments
leaving through the resulting silt fence gaps?
RESPONSE: UNTIL ROADS ARE CONSTRUCTED, THE SILT FENCE WILL
CROSS THE ACCESS LOCATIONS; AFTER ROADS ARE CONSTRUCTED,
STRAW BALE FILTERS WILL BE USED AT FLOW LINES. THIS IS ADDED TO
THE REPORT. HALF OF THE STRAW BALES IN TABLE 4 ARE FOR THESE
FILTERS.
2. The surety calculation is incomplete.
RESPONSE: THIS HAS BEEN CORRECTED.
«...i.. ..,.....-,...« 1 A.... Tl--- 1 -CA
2. Please use the new IDF curve (1997 revision) in the hydrology calculations. It
appears that the old curve (LDGS) has been used, but this project has LUC status.
Please note that this will make changes in the flow calculations.
RESPONSE: THE FLOWS NOW REFLECT USE OF THE NEW IDF CURVES.
3. Please do not use the overall development C-factor in the Rational Method
calculations. It is more accurate to use individual subbasin C-factors. Please
calculate the individual factors and use them instead.
RESPONSE: INDIVIDUAL C-FACTORS WERE DEVELOPED FOR EACH OF THE
FIVE NEW SUB -BASINS.
4. Also, please show overland- and gutter flow distances separately and include time of
concentration calculations to verify the intensities being used. The hydrology
calculations will be checked in further detail when comments 1-3 have been
addressed.
RESPONSE: RAINFALL INTENSITIES NOW REFLECT BOTH OVERLAND AND
GUTTER DISTANCES TO CALCULATE PEAK FLOW TIMES.
5. Please see the redlined report and clarify the origins of the boxed values cited from
the Filing 1 report. Please make any revisions. Also, please note that there will be
changes in the comparative tables of the Filing 1 report and the proposed conditions.
RESPONSE: THE RIGDEN FARM TABLES AND PIPE SUMMARIES ARE
REFERRED IN THE REPORT, AND THOSE TABLES HAVE BEEN ATTACHED.
THE FINAL FLOWS CAN BE SEEN IN TABLE 3 OF THE REPORT. ONCE THE
REPORT IS APPROVED, I WILL SEND IT TO JR ENGINEERING FOR THEIR
REFERENCE.
6. Please call out, show slope, and show cross sections of all swales on the plans. Also,
please show calculations and cross sections with freeboard capacity of 1.33*Q100,
and use n=0.06 for grass channels with depth </= 2 feet, per SDDC Table 7-4.
RESPONSE: SWALES ARE SHOWN ON THE GRADING PLAN WITH CROSS -
SECTIONS. 100-YEAR STORM FLOWS ARE EASILY HANDLED WITHIN THE
EASEMENT WITHOUT FLOODING ANY LOTS.
7. Please show more details on the grading plan, including high points, low points, and
other spot elevations to help define the directions of flow. Examples are given on the
redlined grading sheet. Also, there appear to be a couple of areas of grading steeper
than 4:1, which are also marked on the plans. Please regrade these to a maximum of
4:1 or provide a retaining wall. If these slopes cannot be avoided, please request a
variance.
ADVANCED PROFESSIONAL ENGINEERING INC.
Registered Professional Engineers In Colorado Arizona, New Mevdo & Wyoming
P.O. Box 1391, 212 West Magnolia Street, Fort Collins CO 80522-1391
Phone 970-484-0533 Fax 970-484-5086 E-mail apeinc@frii.com Web Site: advancedpe.com
February 13, 2001
Basil Hamdan
City of Fort Collins Utilities/Stormwater
700 Wood Street
Fort Collins, CO 80521
Dear Basil:
SUBJECT: SETTLER'S GREEN
Below are the responses to the 2nd submittal of Settler's Green Plans and Drainage
Report. Please call if you have any questions.
Sincerely,
Dave Sneesby, PE
The configuration of the proposed drainage basins significantly do not match what
was proposed in the 1 a Filing. How will this effect the existing downstream
facilities? Please show that the downstream facilities will have adequate capacity,
including streets, inlets, storm sewers, etc. It may be prudent to contact JR
Engineering, which is currently working on designing facilities downstream of the l'
Filing. At least they can alter their analysis to match what is being proposed with this
development. If you have any questions about these concerns, please contact Basil
Hamdan at 221-6035.
RESPONSE: THE FLOW CHANGES ARE SHOWN ON TABLE 3 NOW, AND
EXISTING STORM WATER FACILITIES HAVE ADEQUATE CAPACITY FOR
ALL CHANGES. THE FLOWS AND ANALYSES ARE EXPLAINED IN
"PROPOSED DEVELOPMENT DRAINAGE CONDITIONS, 100-YEAR STORM' IN
THE REPORT.
A ENGINEERING'S AMBER REED WAS VERY HELPFUL IN DETERMINING
THOSE CAPACITIES.
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