HomeMy WebLinkAboutTR 35337 HYDROLOGY REPORT-031 Spyglass Ranch Tract 35337
Hydrology Study \`y
required for this sub—area. Tables 2 and 3 provide a complete summary of
the rational method analysis for each drainage area.
Basin Spillways and Auxiliary Outlets
In the event that any of the basins do not drain properly, each
basin is equipped with an emergency spillway. The concrete lined spillway
for Basin #1, an infiltration basin, is located on the easterly side of the
basin adjacent to Elsinore Hills Road. The spillway is set just above the
design water surface elevation and is sized to manage the maximum
flowrate that is designed to bifurcate into the basin plus any additional
runoff that is directly tributary to the basin. In addition to the spillway,
an emergency outlet pipe with a shear gate is provided near the basin
bottom in the event that standing water would need to be drained for any
reason.
The concrete lined spillway for Basin #2, a dual purpose extended
detention basin, is located on the westerly side of the basin adjacent to
Camino Del Norte. The spillway is set above the outlet structure baffle
wall weir and is sized to manage the maximum design flowrate tributary to
the basin. The outlet structure provides a shear gate clean out in the
event that standing water would need to be drained for any reason.
The concrete lined spillway for Basin #3, a dual purpose extended
detention basin, is located on the southerly side of the basin adjacent to
the south tract boundary. The spillway is set above the outlet structure
baffle wall weir and is sized to manage the maximum design flowrate
tributary to the basin. The outlet structure provides a shear gate clean out
in the event that standing water would need to be drained for any reason.
The critical hydraulic routing calculations for the spillways are
provided in the Appendix of this report.
— Conclusion —
The projected flows that will be discharged to the existing properties
and facilities downstream of the proposed development are permissible
within the criteria and specifications indicated in this study and satisfy the
City conditions of approval for increased runoff criteria. All tributary
offsite flows are either mitigated to match the historic flows, or conveyed
to a public drainage facility, or accepted by the receiving property via a
joint development agreement (drainage acceptance agreement).
The three onsite basins are designed to provide the necessary water
quality treatment to be in compliance with NPDES guidelines and
regulations. Two of the three onsite basins are also designed for storm
mitigation based upon the increased runoff criteria for the 10—Year storm
frequency at the 6 hour and 24 hour storm durations. The proposed
streets and storm drain system provide sufficient capacity to manage all
10—year and 100—year flows at their required limits per the Conditions of
Approval. Overall, the entire site is designed to safely convey and manage
the runoff from the 100—year storm frequency.
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