HomeMy WebLinkAboutCC - Storm Drain Report RINGNECK PLACE SUBDIVISION
STORM DRAINAGE REPORT
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D. NO
October 2023 2447 S. Vista Ave.
Boise, Idaho 83705
REV: Phone: (208) 344-1180
RiveRidge Fax: (208) 344-1182
ENGINEERING COMPANY
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V�, STORM DRAINAGE REPORT
TABLE OF CONTENTS
1 INTRODUCTION .............................................................................................1
1.1 SUBDIVISION AND LOCATION...................................................................................1
1.2 PROJECT DESCRIPTION ...........................................................................................1
1.2.1 EXISTING CONDITIONS.....................................................................................1
1.2.2 GROUNDWATER................................................................................................1
1.2.3 PROPOSED PROJECT.......................................................................................1
1.2.4 EXISTING IRRIGATION ......................................................................................2
1.2.5 ENTITIES WITH JURISDICTION OVER DESIGN ...............................................2
2 PRE-DEVELOPMENT DRAINAGE CONDITIONS..........................................2
2.1 MAP OF PREDEVELOPMENT CONDITIONS..............................................................2
2.2 STREET DRAINAGE....................................................................................................2
2.3 SITE INTERIOR ...........................................................................................................2
3 POST-DEVELOPMENT DRAINAGE CONDITIONS .......................................2
3.1 MAP OF POST-DEVELOPMENT CONDITIONS..........................................................2
3.2 STREET DRAINAGE....................................................................................................2
3.3 ON-SITE DRAINAGE ...................................................................................................2
3.4 COMPARISON OF PRE- VS. POST-DEVELOPMENT DRAINAGE .............................3
4 CALCULATION ASSUMPTIONS....................................................................3
4.1 ACHD STORMWATER FACILITIES.............................................................................3
Appendix A.............................................................................................Glossary of Terms A-1
Appendix B .....................................................Predevelopment Catchment Area Map B-1
Appendix C .................................................Post Development Catchment Area Map C-1
Appendix D ................................................................................Stormwater Calculations D-1
INTRODUCTION i I P a g e
STORM DRAINAGE REPORT
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INTRODUCTION ii I P a g e
STORM DRAINAGE REPORT
1 INTRODUCTION
1.1 SUBDIVISION AND LOCATION
Subdivision: Ringneck Place Subdivision
Location: Parcels S1105212448 and S1 1 0521 2449 lying within Government
Lot 3, Section 5, T.3N., R.1 E., B.M.
Main Crossroads: E. Ustick Rd. and N. Verado Ave.
County, City, State ADA County, Meridian, Idaho
Homeowners Association: Ringneck Place Subdivision Homeowners
Association.
1.2 PROJECT DESCRIPTION
1.2.1 EXISTING CONDITIONS
The overall Project Property is 1.538 acres located at 2315 W. Ustick
Rd. east of the intersection of W. Ustick Rd. and N. Verado Ave. in
Boise, Idaho. The property is currently zoned R-1 (Estate Residential).
The site is currently an existing residence with outbuilding. Residential
or bare land exists on the western, southern, and eastern property
boundaries. The northern property boundary is W. Ustick Rd. An
irrigation ditch crosses the southern portion of the property.
The current topography consists of relatively flat and level terrain across
the site with steeper slopes along the northern frontage of W. Ustick Rd.
Throughout most of the site, surface materials consist of native silty
gravel with sand fill materials underlain by silty sand sediments with
weak to moderate calcium carbonate cementation encountered
throughout this horizon. Poorly graded gravel with sand was
encountered at depth. Vegetation on the site consists primarily of native
weeds and grasses.
1.2.2 GROUNDWATER
The Geotech report completed in June 2022 by Atlas Technical
Consultants (Atlas), showed no groundwater encountered on site to a
maximum depth of 15.3 feet below ground surface. Additionally, based
on other projects in the area Atlas anticipates groundwater at depths
greater than 15 feet below ground surface.
1.2.3 PROPOSED PROJECT
The project will consist of five residential structures (four duplex and
one single structures) on nine residential lots and two common lots. The
development will be served by the existing and new ACHD roads. The
lots will have underground utilities, municipal water, stormwater best
management practices (BMP's), and municipal sewer service.
INTRODUCTION 1 1 P a g e
STORM DRAINAGE REPORT
1.2.4 EXISTING IRRIGATION
There is an existing gravity irrigation line and associated structures
crossing the southern portion of the property. The existing facilities will
be piped north along Block 3, Lot 1 to a point on the common lot line
between Block 2, Lots 3 and 4, continuing along said common lot line to
the western boundary, and then south along the western boundary of
Block 2, Lot 4 to the discharge point of the existing irrigation ditch. A
wet well and pump station located in Block 3, Lot 1 at the turn to the
west.
1.2.5 ENTITIES WITH JURISDICTION OVER DESIGN
Entities that have jurisdiction over the design of stormwater and BMPs
for this site will be ACHD and the City of Boise.
2 PRE-DEVELOPMENT DRAINAGE CONDITIONS
2.1 MAP OF PREDEVELOPMENT CONDITIONS
See Appendix B Predevelopment Catchment Area Map for further information
on the contents in this section.
2.2 STREET DRAINAGE
Drainage from W. Ustick Rd. is maintained in the existing curb, gutter, drop
inlets, and does not enter the site.
2.3 SITE INTERIOR
Interior site drainage is achieved by percolation through surficial soils.
3 POST-DEVELOPMENT DRAINAGE CONDITIONS
3.1 MAP OF POST-DEVELOPMENT CONDITIONS
See Appendix C Post Development Catchment Area Map for further
information on the contents in this section.
3.2 STREET DRAINAGE
Runoff from W. Ustick Rd. will remain unchanged. Runoff from the interior
roadways will be collected and conveyed by curb, gutter, curb inlet, and a
stormwater system to the seepage bed along N. Lapis Ave.
3.3 ON-SITE DRAINAGE
Portions of the residential runoff will be conveyed through sheet flow, curb,
gutter, curb inlets, and a stormwater system to the seepage bed located along
N. Lapis Ave. Most of the site runoff from the predevelopment areas will be
directed into this system. Additional residential runoff will be retained within
their lot and percolated through surficial soils.
PRE-DEVELOPMENT DRAINAGE CONDITIONS 2 1 P a g e
STORM DRAINAGE REPORT
3.4 OFF-SITE DRAINAGE
Portions of the runoff will be conveyed through sheet flow, curb, gutter, curb
inlets, and a stormwater system to the existing ACHD stormwater facilities
located along E. Ustick Rd. This runoff will consist of only those portions of the
property between E. Ustick Rd. and the proposed retaining wall along the
south side of Block 1, Lot 1.
3.5 COMPARISON OF PRE- VS. POST-DEVELOPMENT DRAINAGE
The portions of runoff that contribute to off-site drainage along W. Ustick Rd.
will continue to be conveyed via the existing stormwater facilities along W.
Ustick Rd. The runoff from other on-site sources will be maintained on-site.
The off-site runoff from other sources is anticipated to be negligible and are
not anticipated to require additional measures beyond those already proposed.
4 CALCULATION ASSUMPTIONS
4.1 ACHD STORMWATER FACILITIES
Calculations for stormwater basins are included in Appendix D Stormwater
Calculations. These calculations use the Rational Method for peak discharge and
expected volumes. The following assumptions have been made:
Rational Method:
• Q = Total Runoff Volume in cfs
• C = Runoff Coefficient
• 1 = Storm Intensity
o For pipe sizing: Qpeak (100-year Tc=10 minutes) I = 2.18-2.58 in/hr
o For Seepage bed sizing: Qstorage (100-year 60-minute storm) 1=0.96
in/hr. 25% has been added for ACHD facilities.
CALCULATION ASSUMPTIONS 3 1 P a g e
STORM DRAINAGE REPORT
Appendix A Glossary of Terms
Glossary of Terms A-1 I P a g e
STORM DRAINAGE REPORT
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Glossary of Terms A-2 1 P a g e
STORM DRAINAGE REPORT
AASHTO: American Association of Hotspot: A land use that generates
State Highway and Transportation highly contaminated runoff with
Officials Aquifer: A porous water concentrations higher than those
bearing geologic formation that typical to stormwater.
yields water for consumption.
Hydrological Soil Group: The soils
ACHD: Ada County Highway classification system developed by
District the U.S. Soil Conservation Service
(now the Natural Resource
ASTM: American Society for Conservation Service) that
Testing and Materials Best categorizes soils into four groups, A
Management Practice through D, based on runoff
potential. A soils have high
BMP: (Best Management Practice) permeability and low runoff whereas
A practice, or combination of D soils have low permeability and
practices, that is determined to be high runoff.
an effective and practicable
(including technological, economic, Impervious cover: Surfaces that
and institutional considerations) do not allow rainfall to infiltrate into
means of preventing or reducing the the soil. Examples include
amount of pollution generated by pavements, roofs, sidewalks,
nonpoint sources to a level driveways, etc.
compatible with water quality goals.
It can be a structural or non- Infiltration rate: The rate at which
structural device designed to stormwater moves through soil
infiltrate, temporarily store, or treat measured in inches per hour or
stormwater runoff in order to reduce meters per second.
pollution and flooding.
ICPI: Interlocking Concrete
Detention pond or structure: The Pavement Institute
temporary storage of stormwater
runoff in an area with the objective IDEA: Idaho Department of
of decreasing peak discharge rates Environmental Quality
and providing a settling basin for
pollutants. Observation well: A perforated
pipe inserted vertically into an
Erosion: The process of wearing opengraded base used to monitor
away of soil by water, wind, ice, and its infiltration rate.
gravity. 2. Detachment and
movement of soil particles by same. One year storm: A rainfall event
that occurs once a year or has a
Exfiltration\Exfiltrate: The 100% chance of occurring in a given
downward movement of water year.
through an open: graded, crushed
stone base into the soil beneath. One hundred year storm: A very
unusual rainfall event that occurs
A-31 Page
STORM DRAINAGE REPORT
once every 100 years or has a 1%
chance of occurring in a given year. Porous pavement: A surface full of
pores capable of supporting
Open-graded base: Generally a pedestrians and vehicles, e.g.
crushed stone aggregate material porous asphalt, porous concrete
used as a pavement base that has (cast: inplace or precast units).
no fine particles in it. The void
spaces between aggregate can Pretreatment: BMPs that provide
store water and allow it to freely storage and filtering pollutants
drain from the base. before they enter another BMP for
additional filtering, settling, and/or
Outlet: The point at which water is processing of stormwater pollutants.
discharged from an open: graded
base through pipes into a stream, Retention pond: A body of water
lake, river, or storm sewer. that collects runoff and stays full
permanently. Runoff flowing into the
Peak discharge rate: The pond that exceeds its capacity is
maximum instantaneous flow from a released into a storm sewer,
detention or retention pond, open: stream, lake, or river.
graded base, pavement surface,
storm sewer, stream or river usually Sediment: Soils transported and
related to a specific storm event. deposited by water, wind, ice, or
gravity.
Permeability: The rate of water
movement through a soil column
under saturated conditions, usually Time of concentration: The time
expressed as k in calculations per required for water to flow from the
specific ASTM or AASHTO tests, most remote point of a watershed or
and typically expressed in inches catchment to an outlet.
per hour or meters per second.
Void Ratio: Volume of voids around
Permeable pavement: A surface the aggregate divided by the volume
with penetrations capable of of solids.
passing and spreading water
capable of supporting pedestrians
and vehicles, e.g. permeable
interlocking concrete pavement.
Pervious or permeable
surfaces/cover: Surfaces that allow
the infiltration of rainfall such as
vegetated areas.
Porosity: Volume of voids in a base
divided by the total volume of a
base.
A-4 Page
�✓ STORM DRAINAGE REPORT
Appendix B Predevelopment Catchment Area Map
Predevelopment Catchment Area Map B-1 I P a g e
STORM DRAINAGE REPORT
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Predevelopment Catchment Area Map B-2 1 P a g e
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LEGEND
PRELIMINARY PLAT BOUNDARY
PROPOSED LOT LINE A''�
15"SD O PROPOSED STORM DRAIN MAIN, SIZE, MANHOLE AND CATCH BASIN PRE DEVELOPMENT DRAINAGE AREA MAP
2780 PROPOSED 5' CONTOUR 0 15 30 60 90
DATE:
2779 PROPOSED 1' CONTOUR AUGUST 2023
JOB: 2447 S.Vista Ave.
2780 EXISTING 5' CONTOUR 22040 "45V Boise,Idaho 83705
2779 - EXISTING 1' CONTOUR SCALE: 1" - 30'
E-FILE:
22040 DRAINAGE MAP RiveRidge (208)344-1180
DRAWN BY: www.rvrdg.com
MJBJ ENGINEERING COMPANY
�✓ STORM DRAINAGE REPORT
Appendix C Post Development Catchment Area Map
Post Development Catchment Area Map C-1 I P a g e
STORM DRAINAGE REPORT
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Post Development Catchment Area Map C-2 1 P a g e
I I I
�6 A PROPOSED CATCH MANHOLE ACHD STORMWATER SEEPAGE BED 1 1I
II
(BASINS A,
PROPOSED CATCH BASINS A R S
CW: .69 8 ACRES II
u7
o BLOCK 3 I R
U) 12 BASIN A(INLET 1.2) —
AREA:0.21 ACRES
CW:0.68
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— N.LAPIS AVE.
o 8" —
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r
4,2 7s I / rr / r/ r // / r/ // rr r/ r ,� i r/ //
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BASIN B(IN 1.3) / /
LET
/ BASIN D BASIN C(INLET 1.4) AREA: 0.49 ACRES
AREA: 0.20 ACRES AREA: 0.28 ACRES / / r / / r / / / CW:0.64
1 CW:0.64 CW:0.80 / / / // rr
Y7s I / r /y /r r/ rr // r rr // rr / r r/ //r rr
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W // I/ r 3 F 4, S AREA: 0.27 ACRES 5
CW: 0.53
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AREA: 0.09 ACRES
CW: 0.20
II , 01 \ /
LEGEND
PRELIMINARY PLAT BOUNDARY
PROPOSED LOT LINE '
15"SD PROPOSED STORM DRAIN MAIN, SIZE, MANHOLE AND CATCH BASIN
PROPOSED 5' CONTOUR 0 15 30 60 90
DATE:
PROPOSED 1' CONTOUR AUGUST 2023
2447 S.Vista Ave.
2780 EXISTING 5' CONTOUR SOB. Boise, daho 83705
SCALE: 1" = 30' 22040 � �
2779 EXISTING 1' CONTOUR E—FILE:
22040 DRAINAGE MAP RiveRidge (2WW),ry 4- c80
DRAWN BY:
MJB ENGINEERING COMPANY
-\✓ STORM DRAINAGE REPORT
Appendix D Stormwater Calculations
Stormwater Calculations D-1 I P a g e
STORM DRAINAGE REPORT
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Stormwater Calculations D-2 I P a g e
22040- RINGNECK SUBDIVISION REVISIONS: REV: DATE DESCRIPTION
PreConstruction Drainage Calculations
August 2023 *Designed per ACHD Standards
**Designed per City of Meridian Standards
Average Rainfall Intensity/Peak Discharge
TOTAL ASPHALT/ LAWN/
DRAINAGE AREA AREA CONCRETE ROOF GRAVEL LANDSCAPE Cw Tc 125* Q25* 1100 Q100
(C=0.95) (C=0.95) (C=0.5) (C=0.2)
(AC) (AC) (AC) (AC) (AC) (Min.) (IN/Hr) (CFS) (IN/Hr) (CFS)
Pre-Construction 1.54 0.02 0.03 0.02 1.49 0.23 10 1.85 0.65 3.11 1.10
PAGE 1 OF 1
22040-RINGNECK SUBDIVISION REVISIONS: REV: I DATE DESCRIPTION
Post Construction Drainage Calculations
October 2023 *Designed per ACHD Standards
**Designed per City of Meridian Standards
Average Rainfall Intensity/Peak Discharge
TOTAL ASPHALT/ ROOF LAWN/
DRAINAGEAREA AREA CONCRETE **** LANDSCAPE Cw Tc 125* 0,25* 1100* Q100*
(C=0.95) (C=0.95) (C=0.2)
(AC) (AC) (AC) (AC) (Min.) (IN/Hr) (CFS) (IN/Hr) (CFS)
Seepage Bed 1* 0.98 0.46 0.18 0.34 0.69 10 1.85 1.25 2.58 1.75
Basin A(On-Site)* 0.21 0.13 0.00 0.08 0.68 10 1.85 0.26 2.58 0.37
Basin B(On-Site)* 0.49 0.20 0.09 0.20 0.64 10 1.85 0.57 2.58 0.80
Basin C(On-Site)* 0.28 0.13 0.09 0.06 0.80 10 1.85 0.42 2.58 0.58
Basin D(On-Site)** 1 0.20 0.02 0.09 1 0.08 1 0.64 1 10 1 1.85 1 0.23 2.58 0.33
Basin E(On-Site)** 0.27 0.02 0.10 0.15 0.53 10 1.85 0.26 2.58 0.36
Basin F(Off-Site)** 0.09 1 0.00 0.00 0.09 0.20 10 1.85 0.03 2.58 0.05
2.52
1 Hour Runoff Volume
25 YR 100 YR
DRAINAGEAREA Tc 125* Q25* VOLUME I100* Q100* VOLUME
(Min.) (IN/Hr) (CFS) (CF) (IN/Hr) (CFS) (CF)
Seepage Bed 1* 60 0.69 0.47 1685 0.96 0.65 2344
Basin A(On-Site)* 60 0.69 0.10 353 0.96 0.14 491
Basin B(On-Site)* 60 0.69 1 0.21 1769 0.96 1 0.30 1070
Basin C(On-Site)* 60 0.69 0.16 563 0.96 1 0.22 783
Basin D(On-Site)** 60 0.69 0.09 313 0.96 0.12 436
Basin E(On-Site)** 60 0.69 0.10 351 0.96 0.14 489
Basin F(Off-Site)** 60 0.69 0.01 46 0.96 0.02 64
Seepage Bed
MINIMUM
STORAGE PIPE CROSS INFILTRATION
100YR 25% VOLUME BED BED BED #OF PIPE SECTIONAL VOLUME PIPE ROCK VOLUME DESIGN
DRAINAGEAREA VOLUME VOLUME REQUIRED VOID RATIO INFILTRATION RATE DEPTH WIDTH LENGTH PIPES PIPE SIZE LENGTH AREA PER HR VOLUME VOLUME PROVIDED CHECK
(CF) (IN\HR) (LF) (LF) (LF) (FT) (LF) (SF) (CF) (CF) (CF) (CF)
Seepage Bed 1* 2344 586 2930 0.40 8.00 6.0 12.0 80.0 1 1.50 80 1.77 640 141 2163 2944 OK
TIME TO DRAIN INFILTRATION RATE= 8.00 (IN\HR)
MAX **** Roof Areas based on surveyed values or proposed designs.
VOLUME 90%OF DRAINAGE DRAINAGE DESIGN
DRAINAGE AREA TO DRAIN VOL TIME TIME CHECK
(CF) (CF) (HRS) (HRS) (HRS)
Seepage Bed 1* 2930 2637 48.00 4.12 OK
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Njo(lt'
2447 S. Vista Ave.
Boise, Idaho 83705
RiveRid a Phone: (208) 344-1180
g Fax: (208) 344-1182
ENGINEERING COMPANY