HomeMy Public PortalAboutResolution 2019-06, Approving Modifications To Street Construction Plans Of Woods Estate, Regarding Maximum Grade and Reinforcing Mesh Requirements For Streets RESOLUTION NO. 2019-06
A RESOLUTION APPROVING MODIFICATIONS TO
STREET CONSTRUCTION PLANS OF THE WOODS
ESTATES OF RIVERDALE SUBDIVISION
REGARDING MAXIMUM GRADE AND
REINFORCING MESH REQUIREMENTS FOR STREETS
WHEREAS, Seth Woods, Seth Woods Construction and Development, Inc. ("Woods"),
and his civil engineer J & M Civil Design LLC, Bettendorf, upon finding a layer of bedrock in
the area where Madison Drive is to be constructed to rise from State Street (US 67) to the upper
elevations of the property, did request a modification from the City of Riverdale ("City")
Subdivision Ordinance to waive the seven percent maximum grade and allow for a nine percent
grade so as to avoid extensive rock removal by blasting or other concussive means; and,
WHEREAS, Woods civil engineer also requested alternate construction specifications for
street construction for Woods Estates of Riverdale Subdivision("Woods Estates"), proposed by
Bryce A. Johnson, Licensed Professional Engineer, Iowa License 13827 which called for
construction of said streets without the addition of reinforcement in the concrete; and,
WHEREAS, while the City's Subdivision Ordinance sets a maximum street slope at 7%,
it allows that in some cases topography may be such that this may be modified; and,
WHEREAS,the City's subdivision ordinance allows for utilization of state of Iowa
SUDAS standards for street construction specifications for streets having traffic projections
greater than 250 vehicle trips per day, and per the calculations and assessment by the City's
engineer, a pavement cross section with 6" PCC paving on 6"thick aggregate base is sufficient
per SUDAS standards to carry the projected traffic load for the subdivision, and further is
substantially the same cross section approved by a prior City Council for the reconstruction of
Manor Drive; and,
WHEREAS, in granting modifications, the City may require such conditions as will, in
its judgement, secure substantially the objectives of the requirements so modified; and,
WHEREAS, the City Engineer finds that the proposed modifications for street slope and
paving design proposed, with the addition of subgrade drainage as needed are a reasonable
adjustment to the difficulties in topography present and will not provide for a street that is less
durable than the basic Subdivision Ordinance specifications, but will secure substantially the
objectives of those requirements set forth in said Ordinance.
NOW THEREFORE, BE IT RESOLVED, BY THE CITY COUNCIL OF THE CITY
OF RIVERDALE IN THE STATE OF IOWA:
Prepared by City Administrator Tim Long February 7,2019
Resolution No. 2019-06 February 12, 2019
Woods Estates Street Construction Specifications Modifications
-2-
Section 1. That the sketch prepared by Woods' engineer, J& M Civil Design, Inc,
Bettendorf, Iowa, entitled "Approximate Subdrain Locations"proposing subdrain locations
along Madison Drive and at the intersections with Mason Lane and Gwyneth Way, highlighted
in blue, is attached to and hereafter is a part of this resolution.
Section 2. That the drawing prepared by MSA, dated 1/29/19 and entitled"Typical
Sections— Subdivision Streets: Woods Estates Engineering Review" is attached to and hereafter
a part of this resolution.
Section 3. That the Council, upon consideration of the recommendation of its engineer
and staff, and its own review and observations, does accept and approve a modification to its
Subdivision Ordinance allowing the street slope for Madison Drive, Woods Estates to have a rate
of slope not to exceed nine percent (9%).
Section 4. That the Council, upon consideration and recommendation of its engineer and
staff, and its own review and observations, does accept and approve a street construction cross
section with PCC paving of six inches (6")thickness with a six inch(6")thick compacted
aggregate base, with subgrade drainage and otherwise meeting SUDAS standards as determined
by the City Engineer.
PASSED AND APPROVED this day of
1Ov-.ie t vJ 18.
Mike Bawden, or
ATTEST:
Ronald Fullerlove, City Clerk
Prepared by City Administrator Tim Long February 7,2019
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250'10"E 362.01" Approximate Subdrain Locations
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L 1 JOINT TRAVERSE JOINTS SHALL BE 6'THICK PCC PAVEMENT 6 STANDARD CURB
TYPE C WITH 15'SPACING
6 THICK AGGREGATE BASE GRADED AND
IDOT GRADATION 13 COMPACTED
95%STANDARD DENSITY SUBGRADE
GRADATION NUMBER 29-TYP.
SUBGRADE DRAINAGE SHALL BE
INSTALLED IN THE FOLLOWING AREAS'.
SUBGRADE STABILIZATION FABRIC SHALL 1R-R 158'
BE INSTALLED BETWEEN THE IDOT A.)BETWEEN US 67 AND STATION 14+00,
GRADATION 13 AGGREGATE BASE AND THE In B, MADISON DRIVE
IDOT GRADATION 29 SUBGRADE DRAINAGE
2%SLOPE 2%SLOPE
AGGREGATE le.
TVP I .)20 FEET ON EITHER SIDE OF
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;1, I I II Iy� �LI'1 1 =�'•I- - -i=�1'Fa tL� C.)STALL LOCATIONS AI WH. ERE GROUND
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Jf4'.t ki WATER HAS BEEN ENCOUNTERED DURING
'�t I„ THE INSTALLATION OF UTILITIES OR
°i1 19' 4'DIA PERFORATED a' GRADING.
-
:,�: 1 HOPE CONFORMING ��AM' THE TRENCH SHALL BE WRAPPED IN
TO IDOT 4143 SUBSURFACE DRAINAGE FABRIC
-104^ CONFORMING TO IDOT 4196.01-2.
TYPICAL SECTION NOTE:IF PROOFROLL INDICATES A
SUBDIVISION STREETS(RESIDENTIAL) SHAKNESS IN THE LBEEXCAVATE ONEFO,THEAREA
NOTE:THE SUBGRADE DRAIN TRENCH SHALL BE EXCAVATED ONE FOOT DEEP BY
CAH SHALL BE 1E INCHES DE DRAINAGEEPT AT EL THE WIDTH OF THE E SURFACE AREA.THE
EINGLOCATIONS WHLLERD E TO TO CON . IS HAF TTEENTIRE ROAD SHALL SUBGRADE ONE
THING IHETRENC WIDTHCHALLTIONC. NTS ST LEN FABEC SHALL B. LACED
THEN THE TRENCH WIDTH SHALL BE 14". STABILIZATIONTHEXCAVATED
FABRIC SHALL PLACED
AND THE ED WITH CR AREASHALLBOCBE
BACKFILLEDLOWITH CRUSHED THE
LEVEL SHALL THE ECONNE T DTHE STABILIZED
DR I AT BE CONNECTEDBYSUBGRADE
DRAINAGE TO THE STORM SEWER SYSTEM.
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PLOT EWE 1/2210,rOmmiaFmmmnnmrusomConsi*moneRroner.w. r nmmrsrmraRooW11wae_ a........., SCOTT COUNTY,IOWA
1
2550 Middle Road, Suite 602
Bettendorf, IA 52722
civil design Itc Ph. 563.345.3470
www.jmcivildesign.com
January 22, 2019
Mayor and City Council
City of Riverdale
110 Manor Drive
Riverdale, IA 52722
RE: Request for Variance— Street Slope of 9%
Woods Estates 1St Addition
Woods Development would like to request of variance from the City Code of Ordinances to construct
Madison Avenue northwest of State Street at a 9% slope rather than at a 7% slope. The purpose of this
variance request is to raise the grade of the street and rock base above high groundwater levels that were
encountered in the hillside during construction. Some bedrock has also been encountered in the area and
the developer is also concerned that some of the drainage structures may encounter bedrock issues at the
currently designed 7% slope.
We believe that the requested change in grade will reduce the potential impact on the street subgrade and
rock subbase from the high groundwater levels. The developer also intends to construct subdrain tile along
both sides of the street along the Madison Drive hillside to provide additional protection from high
groundwater levels to provide a good pavement that will last a long time in the future.
Sincerely,
Bryce A. Johnson, P.E.
Partner/Civil Engineer
encl.
RIVERDALE } _F
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110 MANOR DRIVE • RIVERDALE IA 52722 • g ,?t`- - -,
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PHONE(563)355-2511 1 1'7 •�
Memorandum
Date: January 15, 2019
To: Mayor Bawden,Council Members
C: Chris Cooper/MSA,Staff
From: Tim Long,City Administrator
Subject: Street Specifications,Woods Estates
In a meeting today,following our engineer's review and recommendations on engineering,and mine
regarding intent and justification of the Subdivision Ordinance,the Mayor,City Engineer and I
presented,and Woods and his engineer concurred that a 6"pcc pavement properly installed over 6"
compacted base rock,combined with subgrade drainage for the hill and any other low spot flowing
water when excavated,is both sufficient and justifiable by Ordinance and prior experience and
approval. We will prepare a resolution spelling this out in detail for a subsequent meeting. Our points
of determination leading to this follow,along with a cross section of the Manor Drive reconstruction in
2012.
1. Woods'engineer notes that the City Council approved Manor Drive to be reconstructed in
2012 with a 6"thick poured concrete surface without reinforcement.
2. The City's Subdivision Ordinance states on page 36 that local residential streets,25o vehicle
per day(vpd)or less,shall be 6"reinforced concrete.
3. The 25o vpd standard in Appendix 1 of our Subdivision Ordinance raises the matter of the
specifications set forth more explicitly in the Ordinance. The FHWA's 2009 calculation of the
average number of trips per day for households like us is 7.8. Multiplying that times 113
households suggests a number in excess of 250 vpd(883,in fact). Further,Woods/the City/
the Iowa DOT approved an intersection design based upon a peak hour number of trips being
40 for one hour traveling up and down Madison from US 67 being as many as 2,700 vpd. This
brings us back to relying on SUDAS standards,cited in"4"below,which Chris further assesses
in his write-up following.
4. Chapter 6:i-a,"Specifications and Requirements",of the City's subdivision ordinance states
that"Acceptable paving surface(either a orb)"is
a. Reinforced Portland Cement Concrete of the thickness and width shown on the
typical cross section shall be in accordance with Section Tomo Portland Cement
Concrete Pavement of the SUDAS Standard Specifications(current addition). The
concrete mixture shall conform to Section 7010 of the SUDAS manual and the Iowa
DOT concrete mix specifications.If an adequate approved base cannot be attained
utilizing existing material an aggregate base will be required.Joint spacing and joint
Subdivision Street Specifications January 16, 2019 Page 1
,CITY OF ,
RIVERDALES: r111 Amid
A sr
110 MANOR DRIVE • RIVERDALE,IA 52722 - ` n
44E-
PHONE(563)355-2511 �j: - �':
details tvill be in accordance with SUDAS standard drawings. See Chris Cooper's
research on this,below.
b. Note: "b"refers to hot mix asphalt paving as an alternate; is not relevant to this
discussion.
From: Christian Cooper/MSA
Tuesday,January is,2019
MSA identified at full build-out the PM peak number of vehicles entering the subdivision at the
Arconic Intersection Entrance will be about 14o Vehicles PH. The number of vehicles exiting the
subdivision will be comparable,at about 130 vehicles per hour(VPH). The VPH for the first phase are
obviously lower. As we analyzed the first phase,this phase includes homes and the development of the
commercial property. So,our analysis of the first phase is not comparable to the first phase that is
approved for construction. Obviously,in all likelihood,the first phase of the development approved
for construction will generate lower numbers. However,in terms of pavement life,I suggest the only
numbers of concern are at full build out.
A crude approximation of the Average Daily Traffic is to multiply the peak hour by 10. Therefore,the
average daily traffic(ADT)of vehicles exiting or entering the Woods Estates Subdivision at full build
out is 2,700 vehicles per day(VPD).
To convert this number to equivalent axles loads(ESALs)for pavement design is a little more fruitless.
At full buildout,truck traffic will be limited to a weekly garbage truck and a few assorted school buses.
So the percentage of truck traffic will be very low. If we assume 1 percent,that equates to 27 trucks per
day. Multiplying by 365 gives us about 10,000 trucks per year. The Iowa DOT allows the conversion
from trucks to ESALS by multiplying the number of trucks by 0.4 for low volume roads. Thus,the
design number of ESALS is about 4000.
SUDAS indicates for poor soil with a 6-inch thick granular base for local roads that the 6-inch
thickness of PCC pavement is acceptable up to 1 million ESALS. So the pavement,as proposed by Seth
is probably sufficient.
In other matters,assuming the welded wire fabric that is utilized for 6-inch thick roadway pavement is
a fairly common WWF 6 x 6—W2.1/W2.1 the additional shear strength the WWF provides is
equivalent to about another 3 inches of PCC. However,as we already established. Unreinforced
concrete with a pavement thickness of 6 inches is more than sufficient according to SUDAS.
MSA's plans for PN 10876013(Reconstruction of Manor Drive,Circle Drive,etc)did provide for 6-
inches of unreinforced concrete on 6-inch thick granular subbase with subgrade drainage. Please see
attached highlighted detail. I did confirm with our engineer at the time that the sub-grade drainage
was installed.
Subdivision Street Specifications January 16, 2019 Page 2