HomeMy WebLinkAboutSite Certifications - 04/20/2000 (3)09/28/00 THU 13:30 FAX 970 491 9984 JR ENGINEERING 0 003
April 20, 2000
Mr. Jay Barber
City of Fort Collins
Storm Water Utility
700 Wood Street
Fort Collins, CO 80521
Re: Drainage Certification for Waterglen P.U.D.
JR Project 9145.02
Dear Jay,
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J•R ENGINEERING
A Subsidiary of Westri an
This letter certifies that the constructed drainage facilities for Waterglen P.U.D. are in general
conformance to the approved drainage and grading plan. Drainage facilities include all
detention and water quality ponds, storm drainage pipe system, drainage swales, street cross -
pans, permanent and temporary erosion control measures. All of these items were discussed
during an on -site meeting on April 19, 2000 with Glen Schlueter of the City of Fort Collins
Stormwater Department. JR Engineering has verified the adequacy of the following items
through field inspections and surveys.
1. Detention pond volumes, bottom and side slopes, inverts and spillway
elevations, outlet structures
2. Drainage swale capacities, bottom and side slopes, concrete trickle channel
sizes and slopes
3. Storm pipe sizes and slopes, inlet sizes, rim elevations
4. Street cross pan sizes and slopes
5. Curb cut sizes
6. Erosion control measures
The detention and water quality ponds and outlet structures were surveyed on January 20,
2000 and February 9, 2000. Additionally, the outlet structure for Pond C was modified and
resurveyed on March 24, 2000. The results of these surveys indicate that the record detention
and water quality ponds have adequate volumes and all of the pond outlets have been
constructed with positive drainage into either Cooper Slough or another downstream pond.
Enclosed with this letter you will find record contour drawings and stage -storage calculations
for all six ponds (A, B, C, D, E and F). Ponds A, B, C and F are water quality and detention
ponds. Ponds D and E are detention ponds only. The required water quality capture volumes
(WQCV) were obtained from the "Final Drainage and Erosion Control Report for Waterglen
P.U.D." (JR Eng. 1998) and the required detention volumes were obtained from the "Regional
Drainage Evaluation for the Waterglen P.U.D." (Lidstone & Anderson, 1998). Note that the
2620 East Prospect Road, Suite 190, Fort Collins, CO 80525
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09/28/00 THU 13:30 FAX 970 491 9984 JR ENGINEERING IM004
Mr. Jay Barber, April 20, 2000
Page 2 of 3
elevations as depicted herein may change subsequent to the date of the surveys due to natural
and/or artificial actions.
The major drainage swales and trickle pans were surveyed on December 16, 1999, January
20, 2000 and April 20, 2000. Two cross sections were taken for each Swale and several
additional spot elevations were taken to evaluate the longitudinal slope. The results of these
surveys indicate that all of the constructed swales have adequate capacity to convey the flows
specified in the "Final Drainage and Erosion Control Report for Waterglen P.U.D." (JR Eng.
1998). Cross sections and flow analysis for the major drainage swales are enclosed with this
letter. Note that the elevations as depicted herein may change subsequent to the date of the
surveys due to natural and/or artificial actions.
The storm drainage pipe and inlet system was surveyed on December 14, 1999. The result of
this survey indicates that the storm drainage pipe and inlet system has been constructed in
general conformance to the approved grading and drainage plans with the special conditions
as noted below.
1. A portion of storm drainage Pipe R is constructed with a slope of 1.64% versus 2.00%
as specified in the design plans.
2. Storm drainage Pipe I is constructed with a slope of 0.14% versus 0.3% as specified in
the design plans.
All other storm drainage pipes have been constructed with slopes equal to or greater than that
specified in the design plans. Subsequent analysis of the pipe systems with Pipes R and I
indicate that the shallower slopes will not adversely affect the overall performance of the
storm water conveyance system. Enclosed with this letter you will find both the Pipe R and
Pipe I system calculations used in formulation of the above conclusions. Also enclosed are
the drawings of record for all of the storm sewer plan and profiles.
The street cross -pans were surveyed on February 1, 2, and 3, 2000. The results of these
surveys indicated that certain cross -pans are constructed with slopes slightly below the design
slope. However, all cross -pans have positive drainage and they will be flow tested by the City
of Fort Collins Street Department next week. As agreed during our meeting with Glen
Schlueter on April 19, 2000, approval of the cross -pans by the Street Department is not
required for approval of this drainage certification. Copies of the street plan and profile
sheets with elevations of record are enclosed with this letter.
Temporary erosion control measures including silt fencing, straw bale barriers and gravel inlet
filters were reviewed during the April 19, 2000 meeting and all deficient measures have been
rectified as of this date. Permanent erosion control measures including riprap, matting and
seeding has been installed per the design plans.
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09/28/00 THU 13:31 FAX 970 491 9984 JR ENGINEERING
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Mr. Jay Barber, April 20, 2000
Page 3 of 3
In conclusion, all of the drainage facilities for Waterglen P.U.D. have been constructed in
general conformance to the approved plans. If you have any questions or comments please do
not hesitate to contact me at my office.
Sincerely,
o�p0o Flee
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Robert Almirall, P.E. ' ``PS�%'�
Division Manager
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