HomeMy WebLinkAboutMiscellaneous PLANNER 2/26/2004
.
~. 2-4 .
)
A-1:tz1--~d i
t'~',.<<.. 4- F'~ J
?~O\.VL s p~
~_, 8U -
POTENTIAL DEVELOPMENT REQUIREMENTS
BY THE PUBLIC WORKS DEPARTMENT
R~CE1VErf' OREGON
DRC STAFF REVIEW:<6~ry_26, 2003)
MOUNTAINGATE - PHASE-4
Prepared by Eric WaltQ~lvil Engineer
Drainage review by Ma~o'LJ\:;I, [IT
SITE PLAN TYPE II
SUB2003-00062
Planner: James Donovan, Planner II
NOTE: The intent of this list is to give a developer insight about requirements related to public
improvements before they develop their property. The Public Works Department individually
reviews each development for appropriate requirements.
ENGINEERING REQUIREMENTS
The conditions cited herein are from the Springfield Hearings Official Gary Darnielle's
decision conditionally approving the request for Master Plan approval of the Mountain Gate
development (Jo. No. 95-02-39) dated May 13, 1998 unless otherwise noted.
HILLSIDE DEVELOPMENT OVERLAY rSoDoC. 26 8i Master Plan Conditionsl:
~ Reports Required [SoD.C. 26.070]
FINDINGS:
1. A Development Plan was not submitted but will be required for Phase 4. A
proposed development plan shall be submitted, depicting building envelopes for
each lot including driveway approaches and all other associated impervious
surface areas. The plan shall be based upon the findings of the required reports
in this Section and the lot coverage standards of Section 26.040. Building
envelopes shall be specified in Covenants, Conditions, and Restrictions recorded
wilh the subdivision plat. SDC 26.070 (5): Development Plan Report.
2. A site specific, detailed soils and geology report was not submitted but will be
required for Phase 4. This report shall include data regarding the geology of the
site, the nature, distribution, and strength of existing soils, conclusions and
recommendations for grading procedures, design criteria for corrective measures,
and options and recommendations to maintain soil stability and minimize erosion
of the site to be developed in a manner imposing the minimum variance from the
natural conditions. The investigation and report shall be prepared by a civil
engineer/geologist. Applicant's building envelopes do not depict the strength of
Date Received; 2'Lh'o1
Planner; I D -r2L~o
ORe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 2 of21
existing soils, conclusions and recommendations for grading procedures, design
criteria for corrective measures and recommendation to maintain soil stability and
minimize erosion of the site to be developed in a manner imposing the minimum
variance from the natural conditions. The building envelopes as shown are likely
to include areas that are not suitable for buildings without engineered foundations.
Further, the building envelopes must be consistent with and "developed in a
manner imposing the minimum variance from the natural conditions." SDC
26.070(1): Soils and Geology Report. .
.
.
.
,~-. . ',:.1' ~~ f~~"
RECOMMENDED CONDITIONS OF APPROVAL:
1) Prior to the approval of the subdivision plat, the applicant shall submit a geotechnical
report for design of all streets, utility maintenance roads and driveways.
2) Prior to the approval of the subdivision plat, a proposed development plan shall be
submitted, depicting building envelopes for each lot including driveway approaches and all
other associated impervious surface areas. The plan shall be based upon the findings of
the required reports and the lot coverage standards of Section 16.040 and Condition 60.
Building envelopes shall be specified in Covenants, Conditions, and Restrictions recorded
with the subdivision plat.
PUBLIC INFRASTRUCTURE (STREET) [S.D.C. 32 & Master Plan Conditionsl:
~ Public Streets [S.D.C. 32.020]
>- Sign an Improvement Agreement [S.D.C. 32.020]
FINDINGS:
1. Unless otherwise agreed to between the City and the applicant, all of the required public
improvements must be constructed and accepted by City Council prior to building
construction on the lots. This is necessary to ensure adequate public and emergency
access and circulation to and from the site.
2. Construct Public Infrastructure Requirements (surface paving, curbs, gutters, drainage
systems, sanitary sewer systems, planter strips, street trees, sidewalks, A.D.A. handicap
ramps, traffic control devices, and street lights) to City of Springfield Standards and
Specifications. First obtain a Public Works construction permit for the privately
engineered public improvements from the Public Works Department. [S.D.C.' Article 32]
3. Condition No. 43 requires details and typical cross-sections with slope control measures
be submitted with each phase or development. The development application shall also
indicate the location and under what conditions retaining walls will be constructed. This
item has not been addressed since a site specific geotechnical report was not submitted
for this phase. Further, applicant has not shown any cross-sections or slope control
measures for utility maintenance roads.
f "
).... f
l:\Mountaingate\SUB200J'{)0062 MountaingatePhliSe '4 DRe Letter.doc
DRe STAFF REVIEW: 2-26-. .
MOUNTAIN GATE PHASE 4
Page 3 of21
4. The tentative plan submitted does not sho'f" private utilities serving individual lots.
Therefore, the tentative plan does not comply with SDC 32.010(1) and 35.060. In order
to achieve compliance, the applicant mustsubrilit a private utility plan prior to the
submittal of the Subdivision Plat consistent with SDC 32.010(1) and 35.060.
5. Condition 45: "General Construction Practices will need to include statements restricting
the construction of embankments on top of soils with a plastic index greater than 30 and
must show construction details for maintaining drainage to eliminate shrink well
problems evident in adjacent development~." Applicant has not shown these sites nor
submitted a geotechnical report showing why the area is exempt from this condition.
The tentative plan does not identify the location and extent of embankments needed to
construct the project, nor does the tentativ~ plan identify the location, depth, and extent
of soils with a plastic index greater than 30' or those with shrink swell potential. Without
this information, staff is unable to determine whether the subdivision layout and lotting
,I
proposed by the applicant will comply with this Condition.
. ,
,
RECOMMENDED CONDITIONS OF APPROVAL:
,
1) Unless otherwise agreed to between the City and the applicant, all of the required public
improvements must be constructed and a~'cepted by City Council prior to building
construction on the lots.
2) Public improvement plans must be prepared by a registered civil engineer and approved
by the City Engineer prior to commencing construction on any work within any public
rights-of-way or easements.
3) Applicant shall revise its plans demonstrating compliance with SDC 35.040.
4) Submittal of a private utility plan consistent with SDC 32.010(1) and 35.060,
demonstrating how each lot can be served by individual private utilities. The private
utility plan must be submitted and approver by the City prior to submittal of the
Subdivision Plat. The.private utilities must be installed prior to subdivision plat approval.
5) The applicant shall not commence any con.struction activities on the site unless and until
the Director issues the Development Agreement.
6) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the applicant shall hire an Oregon registered professional
geotechnical engineer to conduct the site investigations and analyses necessary to
establish the soil and other geotechnical data necessary to comply with Master Plan
Condition 45 and shall redesign the subdivision lotting and layout as needed to fully
incorporate all of the provisions of the Master Plan, the findings and conditions of
approval adopted by the Hearings Official, and all other recommended conditions of
approval that are prepared for the Phase 4 subdivision proposal.
7) Prior to approval of any construction plans or final subdivision plats for the Phase 4
MountainGate development, the applicant shall submit construction plans bearing the
professional engineer's stamp of the Oregbn registered geotechnical engineer
1:\Mountaingate\SUB2003-00062 Mountaingate Phas~ 4 DRe Letter.doc
DRe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 4 of2I
responsible for the geotechnical aspects of the project design and the construction
plans.
.
.
B) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the applicant shall hire an Oregon registered professional
geotechnical engineer to conduct the site investigations and analyses necessary to
establish the soil and other geotechnical data necessary to comply with Master Plan
Condition 46 and shall redesign the subdivision lotting and layout as needed to fully
incorporate all of the provisions of the Master Plan, the findings and conditions of
approval adopted by the Hearings Official, and all other recommended conditions of
approval that are prepared for the Phase 4 subdivision proposal.
>- Street Trees [S.D.C. 32.050 & Master Plan Conditions]
FINDINGS:
1. Condition 58 requires, "An urban forester shall be employed to analyze the street design
and proposed cutting plan for the rights of way of each phase and determine what trees
can be retained to serve as required street trees. The trees shall be depicted on the
tentative subdivision plan and the final construction drawings for the public improvements.
Appropriate measures to protect the trees during construction shall be specified on the
construction drawings." Applicant has not submitted a street tree plan.
2. SDC 32.050(10) lists recommended street trees. This tree list does not support native
trees. The urban forester may be able to assist in identifying suitable tree species for
the site.
3. SDC 35.040(7) requires, "The locations and widths of all existing and proposed
sidewalks and access ways, including the location, size and type of plantings and
street trees in any required planter strip; pedestrian trails; and shared-use paths."
RECOMMENDED CONDITIONS OF APPROVAL:
1) Applicant shall submit a Street Tree Plan demonstrating conformance with master plan
conditions and SDC 32.050 prior to approval of the subdivision plat.
>- Dedicate Public andlor Private Easements [S.D.C. 32.120, OAR 333-61-0050]
FINDINGS:
1. Condition #1 indicates "All new water system facilities and modifications to water
systems facilities both inside and adjacent to the proposed development shall be placed
in the street right-of-way at a location and depth of bury that meets the standards of
SUB. Where street right-of-way width is inadequate to accommodate the facilities, then
the applicant must provide public utility easements abutting the right-of-way. The
applicant has not submitted plans showing water system facilities and necessary
I:\Mountaingate\SUB20D3-00062 Mountaingate Phase 4 ORe Letter.doc
DRe STAFF REVIEW, 2-26. .
MOUNTAlN GATE PHASE
Page 5 of21
documentation showing that SUB has approved proposed locations, details, and
easements.
2. Applicant's plans show 10-foot PUE's along the public right-of-ways. Applicant has not
shown all required slope easements for the proposed public roadways and maintenance
roads. In addition, a 25-foot maintenance easement is required around detention pond
and wetland areas. Condition #30 requires maintenance vehicle access must be
provided around the entire perimeter of each pond. All drainage facilities taking public
storm water shall be designed to public standards.
3. Applicant proposes to dedicate a 10-foot public utility easement along street rights-of-
way in compliance with SDC 32.120(5).
4. A 25-foot maintenance easement shall be dedicated around the perimeter of all
detention pond and wetland areas prior to approval of the subdivision plat to comply with
Condition #6. .
5. Storm drainage from the lots will flow to a wetland and wetland mitigation area.
Applicant shall obtain necessary approvals from the Division of State Lands.
6. Lots containing wetlands and/or drainage-ways, shall have deed restrictions for wetland
mitigation and drainage use only. The wetland mitigation area is for the benefit of all
other lots in the subdivision. Irrevocable joint use/maintenance agreements shall be
executed for joint use and maintenance of the wetland mitigation and drainage lots.
7. Deed restrictions shall be placed on affected lots to prevent the construction of fences,
landscaping and other private improvements on private utility easements to ensure that
adequate access is maintained for system maintenance. Lots 1 through 6 are being
shown with back-lot sewers. Applicant has not submitted required deed restrictions at
these locations.
8. Applicant shall record irrevocable joint use/maintenance agreements for the wetland
mitigation and drainage areas. Lots containing wetlands and/or drainage-ways shall
have deed restrictions limiting their use to wetland mitigation only or drainage only. A
deed restriction shall be placed on affected lots for wetland mitigation and storm water
detention use only.
9. Applicant shall record irrevocable joint use/maintenance agreements for joint
use driveways.
10.Applicant shall resubmit drawings demonstrating the need and adequacy of its
proposed private utility easements.
RECOMMENDED CONDITIONS OF APPROVAL:
1) PUE's shall be dedicated along all existing rights-of-way where there currently is
no PUE of adequate width, and along all proposed and required right-of-way
dedications described herein and required by SDC 32.120. The applicant shall
1:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
DRC STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 6 of21
dedicate additional public and private easements in the location and width
necessary to accommodate the development proposal and as determined
during the final review process.
.
.
2) A 25-foot maintenance easement shall be dedicated around all open channel,
ponds and wetland mitigation areas.
3) Applicant shall resubmit its drawings showing all easements, the purpose of the
easements, and their adequacy prior to final subdivision plat submission.
4) Applicant shall record all necessary private irrevocable joint use/maintenance
agreements for the wetland mitigation lots, joint use driveway, and private utility
easements prior to approval of the subdivision plat.
5) Deed restrictions shall be placed on lots containing wetlands limiting their use
for wetland mitigation and storm water control.
6) Prior to the approval of the subdivision plat, the applicant shall dedicate additional public
right-of-way to the City to accommodate public access, utilities, and other
appurtenances, to and along the frontage of the site.
~ Submit a Traffic Impact Study if use generates 250 or more vehicle trips per day
[S.D.C. 32.020].
(See traffic section comments)
~ Sanitary Sewer [S.D.C. 32.100 & Master Plan Conditions]:
FINDINGS:
1. The applicant proposes to build a gravity sanitary sewer to connect with the existing City
of Springfield sanitary sewer system. Condition 2 requires, "Construction of sanitary and
storm sewers must be done in a logical phasing sequence that corresponds to the
phasing of development. The sewers shall be planned and sized and extended to the
east and south boundaries of the development to serve future development areas in a
logical and convenient manner. " Applicant has not shown how the sewer lines within
many of the private utility easements will be extended nor how they will serve future
development on the project boundaries, Applicant's calculations have not included flow
from other phases or future developments on the project boundaries that will enter the
Phase One system.
2. Condition 3 requires, "Detailed plans for streets, sanitary, and storm systems must be
submitted with each phase of development which include existing and proposed
contours of the site to enable an adequate review of the location and routing of these
systems. Applicant has not submitted sufficient information, including a contour overlay
over utility p,lan, to adequately review the profile of the sewer lines or their routing
I:\Mountaingate\SUB2003-00062 Mountaingate Pha<;e 4 ORe Letter.doc
ORe STAFF REVIEW: 2-26_
MOUNTAIN GATE PHASE ~
Page 7 of21
through other phases.
.
3. Condition 5: "Sewer design shall comply with the Springfield Development Code Section
No. 32.100 and any other special provisions for hillside development that are approved
and required by the City Engineer." Plan and profiles along with stationing shall be
shown on the drawing to allow adequate review. Head losses and hydraulic jumps shall
be calculated through the manholes showing the system with all phases built.
Applicant's submittals do not include this information.
4. Condition 6: The Master Plan drawing shows sewers located along back lot lines.
Unless otherwise approved, on a case-by-case basis, and at the sole discretion of the
City Engineer, all publicly maintained sewer facilities must be located within street rights-
of-way, or in easements immediately adjacent to the right-of-way, or in paved driveway
or private street areas. The conceptual sanitary sewer plan may include provisions for
connecting up to 4 lots on private, shared, laterals in easements to eliminate the need
for back yard sewers. These private sewers would require joint use, joint maintenance
recorded agreements for the affected properties. In Mr. Darnielle's Justification For the
Decision, No.3, he states, "Appendix F of the Master Plan design depicts sewers
located along back lot lines, however, back lot line sewers are to be highly discouraged
because they are largely inaccessible to City maintenance crews, their installation
causes removal of many trees as well as damage to remaining vegetation, and sewer
line cover requirements (5 feet of soil over the line) often cause changes to grades that
affect surface drainage..."
5. Condition 7: "Sanitary sewers are to be extended to the boundaries of the development
area in order to allow flexibility in determining how homes will hook up to the system and
to provide more freedom in tree preservation and other considerations affected by the
design and placement of structures on the affected lots. Sewers internal to the site must
be sized to accommodate any flows that may be anticipated in the future from off-site
development areas. The over-sizing of the sanitary system to provide for off-site
development shall be pursuant to the existing City reimbursement policy". Applicant has
not provided detailed design and over-sizing check based on adjacent drainage basins
for possible future development.
6. Manholes located in any easements not within public rights-of-way or adjacent thereto
and access to the wetland and storm water facilities shall accommodate Maintenance
Division equipment. The maintenance access ways shall be designed and built in 25
foot maintenance easements using the following standards and demonstrate their
design is adequate for maintenance vehicle to turn all curves:
. 12-foot wide paved travel lane
. A maximum 2% cross grade
. A maximum 15% grade for a maximum distance of 200 feet.
. Commercial driveways adjacent to street rights-of-way
· Fences will only be allowed along the borders of the easement, not inside the
easement.
· Lockable bollards to restrict traffic where an easement is not a driveway.
1:\Mountaingate\SUB2003-00062 Mountaingale Phase 4 DRC Leller.doc
ORe STAFF REVIEW: 2-26-04
MOUNT AlN GATE PHASE 4
Page 80f21
7. Condition 10, "Sewer design for each phase shall address specific problems and special
design considerations for steep hillside development such as flow velocity, energy
dissipation, turbulence in manholes and bends and restraints on pipe movement."
Applicant's calculations are insufficient to determine if this condition has been met.
.
.
8. Condition 11, "Trench drainage measures, or other approved methods of handling flow
of water in trench backfill, must be incorporated into all trench sections with slopes
exceeding 10 percent and elsewhere when required by the City Engineer." The trench
drainage system is insufficient. Applicant has not provided calculations or design details
showing that this requirement has been met.
9. Applicant has not demonstrated compliance with Condition #11, including, but not
limited to calculations showing adequacy of its design. Manholes on sealed joint system
(tight line) and all drainage systems on slopes greater than ten percent shall be
constructed with a minimum 20-foot, parallel 6" diameter perforated line complying with
ASTM 03034 with geotextile to drain ground and trench water into the system.
1 O.ln order to comply with SDC 32.010(1) and 35.060 when there are multiple panhandle
lots, private utilities, including but not limited to: sanitary sewer; storm sewer; water and
electricity must be installed by the developer prior to the recording of the Subdivision
Plat.
RECOMMENDED CONDITIONS OF APPROVAL:
1) Applicant shall revise its plans showing a 12-foot wide all weather roads to sewer
manholes, around all storm water facilities and wetland mitigation areas for approval
prior to submission for approval of the subdivision plat.
2) Applicant shall revise its plans demonstrating compliance with Conditions #2, #3, #5, #6,
#7, #8, #10 and #11, for approval prior to submission of the subdivision plat.
3) Public improvement plans for sanitary sewer, showing conformance with SOC 32.100,
must be prepared by a registered civil engineer and approved by the City Engineer prior
to commencing construction on any work within any public rights-of-way or easements.
4) In order to comply with SOC 32.010(1) and 35.060 when there are multiple panhandle
lots, private utilities, including but not limited to: sanitary sewer; storm sewer; water and
electricity must be installed by the developer prior to the recording of the Subdivision
Plat.
~ Storm Water Management [S.D.C. 32.110 & Master Plan Conditions]:
FINDINGS:
1. The MountainGate Master Plan, adopted in 1998, included the following six issues that
will be incorporated into the storm water systems of the development (Master Plan,
1997, page 10):
l:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
ORe STAFF REVIEW: 2-26_
MOUNTAIN GATE PHASE
Page 9 of21
.
. All natural surface watercourses shall be retained as open conveyance channels
to the largest extent practicable.
. The post-development rate of drainage flow from the site into the City's
conveyance system should be the same as pre-development flows.
. Sediment basins and detention basins may be required at key locations.
. There shall be no net impact on the hydrology of the wetland system at the base
of the (north slope) property.
. The use of natural systems shall be required for stormwater conveyance and
infiltration to minimize loading and maintain the existing hydrology of the City's
storm water system.
. Cut-off drains on the downside of all lots and uphill side of all streets shall be
required throughout the development.
2. The MountainGate Master Plan, adopted in 1998, included the following goal statement
with regard to the storm water systems of the development (Master Plan, 1997, page
12): "Finally, the stormwater system envisioned for the project is viewed as one
component in a public facility network that contributes much more than simply protecting
the health, safety, and welfare of the project's future residents and members of the
community at large. It is one of the goals of the project to properly design and construct
where practical open conveyance channels and structures (drainageways and basins)
that can also contribute positively to other highly valued community resources like water
quality, wildlife habitat, public open space and recreational or educational opportunities."
3. The submitted hydrology study does not include calculations for pipe sizing, capacity,
velocity, slope, etc. As required in the Master Plan Conditions of Approval, numbers 16-
18, please include calculations showing the above mentioned items along with rim and
flow line elevations so that staff may determine how the on-site storm sewer system will
function.
4. Plan sheet 4 depicts a 15 inch storm sewer pipe stub located between lots 102 and 103
which will serve all upstream phases of the Mountaingate development. Calculations
from the hydrology study indicate on the order of 60-70 cfs will be served via this 15 inch
storm line. This 15 inch line will not have capacity to serve this much flow. The sizing of
this pipe (and the pipe downstream to the detention pond) needs to be reviewed and
sized appropriately to accommodate flows from the upstream areas.
5. Please submit calculations for the 1 O-year event for both the pre and post developed
conditions. This is consistent with Phases 1 2, & 3.
6. In the submitted hydrology, there is a note in the narrative stating the detention pond will
be lined with one foot of soil with a minimum of 35% clay content. Due to nature of the
fractured rock underlying the bottom of the detention pond, the City feels that this liner
will not suffice to stop infiltration into the ground. Therefore, an alternative liner is
requested to eliminate water from infiltrating into the rock.
7. The hydrology study narrative and associated detention pond calculations indicate only
flows from the "8" basins will enter into the detention pond as part of Mountaingate .
Phase 4 development. After inspection, it has been determined that sub-basin A6 is to
I:\MollRtaingate\SUB2003-00062 Mountaingate Phase 4 ORe Letter.doc
DRe STAFF REVIEW; 2-26-04
MOUNTAIN GATE PHASE 4
Page 10 of21
be built with Phase 4. Therefore, the detention pond calculations shall be re-configured
to reflect this addition of flow.
.
.
8. The calculations for the detention pond end after approximately one day, but still show a
large volume of storage within the pond. Please include the rest of the printouts
showing the drawdown time for the pond for both the 25-year and 1 DO-year storm event
so that it can be determined how long it takes the pond to empty.
9. Submittal does not include a preliminary design and cross section of how water will be
channelized down the steep embankment prior to entering the detention pond.
Currently, no information has been submitted regarding this area of the subdivision. It
appears from the plan set drawings that a large portion of the embankment will re-
graded and changed from initial conditions.
10. Plan sheet 5 of the submitted plan set depicts a jurisdictional drainage way crossing
Mountaingate Drive near lots 106 and 99. After inspection of the plan set, it cannot be
determined how water from the drainage way crosses the road. Please revise the plan
set to clearly demonstrate how water from the drainage way will cross Mountaingate
,Drive.
11. Currently, stormwater discharge from the detention pond is proposed to discharge into
the mitigated wetland area below the pond, and then run to an existing 18 inch storm
culvert before discharging into a roadside ditch. Discharge of stormwater into the
roadside ditch shall not be allowed. Instead, the proposed 12 inch storm line which
ends at lot 118 shall be upsized accordingly and extended to the location of the existing
18 inch culvert.
12. The existing 18 inch culvert that will receive runoff from the detention pond shall be
replaced with a concrete pipe.
13. The use of "one" water quality manhole (described in the hydrology study to be a
"Baysaver") will not be sufficient. Water quality manholes will be required before
discharge into the swale areas, before discharge of stormwater into the pond (from
Mountaingate Drive), and prior to discharge into 5yth Street. _
14. Plan sheet 5 of the submitted plan set depicts two drainage swale located near the
wetland areas in the middle of the proposed subdivision. These swales are to provide
water quality treatment along with a "Baysaver" manhole as described in the narrative of
the hydrology study.
15. Currently, no information has been submitted for the swale design regarding sizing
(length, width, side slopes, etc) or the hydraulic design (velocity, quantity of flow, etc).
Please demonstrate that the swale design will meet the BES requirements as stated
under Section 3.02 of the City's EDSPM interim design standards. Specifically, please
show how the swale functions for a water quality storm event as well as the 25-year
storm event.
1:\Mountaingatc\SUB2003-00062 Mountaingate Phase 4 DRC Letter.doc
ORe STAFF REVIEW: 2-26A .
MOUNTAIN GATE PHASE 4"W'
Page 11 of21
16. There has been no information submitted showing inlet structure detaiL for the proposed
swales. Erosion and scour are of concern due to high flow velocities resulting from
larger storm events.
17. Flows for sub-basins in the hydrology study were computed using a weighted curve
number (CN). City staff has determined these CN values are low due to a variety of
factors (amount of impervious areas in the subdivision, Yo acre lots in several places,
development on steep hillsides, etc.). It is requested the hydrology study is re-
formulated using higher curve numbers that reflect the above mentioned items.
18. The post-development weighted CN of 75 assigned to sub-basin D1 appears low.
Approximately 3 acres of the basin has been designated as multi-family, with the
remaining 10 acres as open space. After inspection of the north cluster area on the
Master plan, it appears that multi-family units will encompass an area larger than 3
acres. Additional calculations are requested using a modified CN which adequately
reflects the developed conditions of sub-basin D1.
19. CN values for sub-basins E1 and 89 also appear low. The assigned CN for developed
sub-basin 89 is 70. The actual CN for this sub-basin will b~ higher due to the fact that
the quarry/detention pond is located within the basin boundary. The quarry area will be
mostly impervious, raising the overall CN for sub-basin 89. Sub-basin E1 will also have
a higher CN than 70 after development, due to Mountaingate Drive which encompasses
approximately 30% of the sub-basin. Please revise the hydrology calculations to reflect
an accurate depiction of the developed sub-basins 89 and E1.
20. Please resubmit wetland calculations showing how the post developed flow rates to the
wetlands are the same as pre existing flow rates. Specifically, please address the issue
of C*A. The calculated values shown do no add up mathematically. Also, please
provide documentation from the geotechnical engineer of record showing that the 15%
and 5% numbers used for sub-surface pre and post flow rate estimation to the wetlands
are legitimate.
21. Condition 13 indicates that storm drainage design shall comply with the Springfield
Development Code Section No. 32.110 and any other special provisions for hillside
development that are approved and required by the City Engineer. This condition has
not been fully satisfied in the applicant's Tentative Subdivision submittal in that the
provisions of Article 32.110 have not been adequately addressed and special provisions
hillside development included in the Master Plan and the Hearings Official's Decision
have not been fully incorporated into the project design. Applicant did not submit
sufficient documentation to demonstrate compliance with this condition.
22.ln order to comply with SDC 32.010(1) and 35.060 when there are multiple panhandle
lots, private utilities, including but not limited to: sanitary sewer; storm sewer; water and
electricity must be installed by the developer prior to the recording of the Subdivision
Plat.
23. Condition 14 states "The storm sewer system shall be constructed in a manner that
provides a storm sewer lateral to every lot for conveyance of roof drains, building
I:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 ORe Letter.doc
ORe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 12 of21
foundation drains, and private property surface and underground drainage. These storm
laterals shall not be permitted to drain to the gutter." The tentative plan shows storm
sewer laterals to each lot. However, insufficient information is provided on the plans to
determine that these laterals will provide all of the drainage functions listed in Condition
14.
.
.
24. Condition 17 states "For each phase of development the developer must provide an
analysis of the drainage tributary areas, both on-site and off-site, and the site system
capacity to ensure that adequate capacity is provided."
25. Condition 18: "Storm drain design for each phase shall address potential problems and
special design considerations for steep hillside development such as flow velocity,
energy dissipation, turbulence in manholes and bends and restraints on pipe
movement." The Stormwater Evaluation submitted with the Phase 4 tentative plan is
insufficient for staff to determine that this Condition has been satisfied. The applicant
proposes addressing these special design issues during the preparation of the
construction plans for the project. However, various methods are available to the
applicant for addressing these special design considerations, and some of these
methods may require significant changes in the layout and location of elements of the
stormwater system. These changes could result in modifications to the proposed lot
pattern or to the proposed easement locations. Applicant's drainage calculations do not
include hydraulic energy grade line or hydraulic jumps in manholes.
26. Condition 19: "Trench drainage measures,.or acceptable alternatives to control water
flow in trench backfill, must be incorporated into all trench sections with slopes
exceeding 10 percent or as required by the City Engineer." Applicant has not submitted
adequate information to substantiate its design. Manholes on sealed joint system'(tight
line) and all drainage systems on slopes greater than ten percent shall be constructed
with a minimum 20-foot, parallel 6" diameter perforated line complying with ASTM
03034 with geotextile to drain ground and trench water into the system. The
Stormwater Evaluation submitted with the Phase 4 tentative plan does not include a
"Trench Drainage System" detail drawing. In addition, manholes on sealed joint
systems (tight line) and all drainage systems on slopes greater than ten percent shall be
constructed with a minimum 20-foot, parallel 6" diameter perforated line complying with
ASTM 03034 with geotextile to drain ground and trench water into the storm water
collection system.
27. Condition 21: "Design of the storm drainage system must be done so that 'no net
change in volume or flow rate is experienced in any of the wetlands on or adjacent to the
site." The applicant's Itemized Response to Master Plan Conditions with the Phase 4
tentative plan states that analysis calculates existing and proposed flows into the
wetland area within Phase IV and concludes that there will be no significant change. he
condition requires that any wetlands on or adjacent to the site must not experience a net
change in volume or flow rate. Applicant has not submitted adequate information to
demonstrate its compliance with this condition.
28. Condition 22: "The project shall incorporate the standard drawings for development of
hillside areas recommended in Appendix A the Hillside Pavement Distress Study, 1994,
1:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
ORe STAFF REVIEW: 2-26. .
MOUNTAIN GATE PHASE
Page 13 of21
by Dames & Moore (please see Attachment 1), deviations from these requirements may
be considered on a case-by-case basis, at the sole discretion of the City Engineer,
during the development of each phase." The applicant's Itemized Response to Master
Plan Conditions with the Phase 4 tentative plan states that conditions will be met and
the applicable details will be incorporated into their design details for the project. The
applicant proposes no deviations from these requirements at this time.
29. Condition 23: "During the design of each phase of the project, the developer shall
provide catch basin sizing calculations to show that adequate inlet capacity is provided
to capture all of the water flowing in the street. Catch basin design shall include the
following considerations: length of run on the street; velocity of flow in gutter bar; volume
of flow in gutter bar; curb openings with depressed gutter bars up-slope of catch basins;
and the control of flow past catch basins." The applicant's Itemized Response to Master
Plan Conditions with the Phase 4 tentative plan states that the applicable details will be
incorporated into the final design drawings for the project. Applicant has provided
preliminary calculations.
30. Condition 25: "Driveway curb cuts and approaches shall be designed to prevent water
flowing in the gutter from entering private properties with emphasis on the outside of
curves on steep down slopes." Applicant has not submitted enough information to
demonstrate its compliance with this condition. The applicant's Itemized Response to
Master Plan Conditions with the Phase 4 tentative plan states that the applicable details
will be incorporated into the final design drawings for the project.
31. Condition 26: "Prior to approval of the first subdivision tentative plat for any phase of the
development, the developer and the City shall enter into an agreement specifying
responsibilities for the long-term access and maintenance of the storm drainage
detention and water quality ponds." This condition has not been satisfied in the
applicant's Tentative Subdivision submittal in that the developer and the City have not
entered into the required access and maintenance agreement.
32. Condition 27: "All proposed or required detention ponds must include water quality
measures or water quality Best Management Practices must be incorporated into the
overall design of the master storm water system sufficiently to comply with Section
32.110(4) as determined by the City Engineer." The applicant's Itemized Response to
Master Plan Conditions with the Phase 1 tentative plan states that the ponds will include
all necessary BMP's.
33.At a minimum detention ponds and other open impoundment facilities such as
landscape areas, open playing fields and parklands, must comply with the requirements
of ORS 537, in general and more specifically ORS 537.4 Ponds and Reservoirs: .
a. Interior side slopes up to the maximum water surface shall be no steeper than
3H:1V. If the interior slope needs to be mowed, the slope shall be 4H:1V
b. Exterior side slopes shall not be steeper than 2H:1V unless analyzed for stability
by a geotechnical engineer.
c. Pond walls and/or dikes may be retaining walls, provided that the design is
prepared and stamped by a registered professional engineer and that a fence is
I:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
ORe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 14 of21
.
.
provided along the top of the wall and that at least 25 percent of the pond
perimeter will be a vegetated soil slope of not greater than 3H:1V.
d. Pond bottoms shall be level, and shall be located a minimum of 0.5 feet below
the inlet and outlet to provide sediment storage.
e. A pond overflow system must provide controlled discharge of the design storm
event for developed contributing area without overtopping any part of the pond
embankment or exceeding the capacity of the emergency spillway. The design
must provide controlled discharge directly into the downstream conveyance
system. An emergency overflow spillway (secondary overflow) must be provided
to safely pass the 1 DO-year, 24-hour design storm event over the pond
embankment in the event of control structure failure and for storm/runoff events
exceeding design. The spillway must be located to direct overflows safely towards
the downstream conveyance system. The emergency spillway shall be stabilized
with riprap or other approved means and shall extend to the toe of each face of
the berm embankment.
f. Pond berm embankments higher than six-feet shall require a design by a
geotechnical -civil engineer. The berm embankment shall have a minimum 15-
foot top width where necessary for maintenance access.
g. Pond berm embankment must be constructed on native consolidated soil (or
adequately compacted and stable fill soils analyzed by a geotechnical engineer)
free of loose surface soil materials, roots and other organic debris.
h. Pond berm embankments must be constructed by excavating a 'key' equal to 50
percent of the berm embankment cross-sectional height and width or as designed
by a geotechnical engineer.
i. The berm embankment shall be constructed on compacted soil (95 percent .
minimum dry density, per AASHTO T99, placed in six-inch lifts, with the following
silt characteristics: a minimum of 30 percent clay, a maximum of 60 percent sand,
a maximum of 60 percent silt, with nominal gravel content or as designed by a
geotechnical engineer. .
J. Anti-seepage collars must be placed on pipes in berm embankments, which
impound water greater than four feet in depth at the design water surface.
k. Exposed earth on the pond bottom and side slopes shall be seeded with seed mixture
approved by the City.
34. Condition 28: Prior to or concurrent with development of any phase south of Line "A" on
Exhibit 2, Appendix E, the applicant shall provide detailed plans for the detention ponds
proposed at the "Public Park" site. Detailed plans for the detention pond have not been
submitted with application for Phase 4 and will need to be submitted with construction
plans.
35. Condition 30: "For all publicly maintained ponds, maintenance vehicle access must be
provided around the entire perimeter of each pond. For publicly maintained open
drainage channels, access paths, a minimum of 7 feet wide, must be provided along at
least one side of every channel. Access must also be provided and guaranteed for all
storm drain manholes located outside of a street right-of-way." This condition has not
been satisfied in the applicant's Tentative Subdivision submittal in that the developer
and the City have not entered into the access and maintenance agreement required
pursuant to Master Plan Condition No. 26 which will define the public and private
I:\Mountamgate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
DRe STAFF REVIEW: 2-26. .
MOUNTAIN GATE PHASE 4
Page 15 of21
maintenance responsibilities. Furthermore, the Master Plan provisions and Hearings
Official's Decision concerning the use of open drainage channels have not been
considered in the design of the project. Therefore, insufficient information is available
for staff to determine whether the pedestrian access path requirements of the condition
have been satisfied. Applicant has not provided access around the perimeter of each
pond. Applicant has not provided adequate access for manholes located outside of the
street rights-of-way. .
36. Condition 32: "The design engineer shall incorporate drainage benches, private storm
drain systems, and other features as may be recommended by the project geotechnical
engineer and approved by the City Engineer, at the top of all cut slopes, and along the
exposed face of all cut and fill slopes to reduce the potential of erosion on these slopes."
A site specific Geotechnical Evaluation was not submitted with the Phase 4 tentative
plan. Therefore, staff is unable to determine that this Condition has been satisfied.
37. Finding 1: The Mountaingate Master Plan; adopted in 1998, included the following
Statement of Purpose for Section III. Groundwater Control Plan (Master Plan, 1997,
page 16): "This plan's intent is to provide an integrated approach to the control of
groundwater where soil conditions may warrant the need for such control as to prevent
future maintenance problems and safety hazards experienced to the east of the
MountainGate Project."
38. Finding 2: The Hearings Official, in his decision on the MountainGate Master Plan,
Journal No. 95-02-39, dated May 13, 1998, stated in his "Facts Relied Upon (Findings)"
number 13. (Master Plan page 12 of 42), that: "Persistent groundwater flows in the
hillside areas of Springfield are significant cause of degradation and instability of street
structures. Collection of groundwater flows and discharge to curb weepholes results in
persistent flow on the street surface with unpredictable flow rates. The City anticipates
that there will be persistent flows throughout the development."
39. The Hearings Official further found that (Master Plan page 13 of 42):
. Complex groundwater conditions exist in the area of the subject property and are
caused by the fractured nature of rock deposits and the presence of lower-
permeability soil layers.
. Pavement distress is a hazard in areas .of complex groundwater conditions and
steep slopes.
. Springs can be created through the excavation into a natural slope with near-
surface groundwater, lowering the ground surface below the normal groundwater
surface.
. The complex geologic structure of the subject property makes predicting spring
locations and sources very difficult.
. Surface water can be controlled by several methods.
. Fill settlement problems often are the result of insufficient fill composition and/or
compaction.
40. Condition 46: All persistent flow conditions, except for the identified open water
component of the stormwater master plan, shall be directed into the piped storm system.
I:\Mountaingate\SUB2003~00062 Mountaingate Phase 4 ORe Letter.doc
DRe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 16 of2]
This condition has not been fully satisfied in the applicant's Tentative Subdivision
submittal in that the tentative plan does not address the open water components of the
Master Plan, nor is there information in the applicant's submittal concerning how and
when persistent flow conditions will be identified, intercepted and conveyed. Without
additional information, staff is unable to determine whether the stormwater system,
subdivision layout and lotting proposed by the applicant will comply with this Condition.
.
.
41. Condition 47: The developer shall include longitudinal drainage systems along the uphill
side of all streets constructed on cut slopes for each phase of the development. These
drains shall discharge to a piped drainage facility, not the street gutter. This condition
has not been fully satisfied in the applicant's Tentative Subdivision submittal in that the
tentative plan and the Stormwater Evaluation do not adequately identify the location and
extent of the cut slopes, nor are the required drains shown on the plan for the storm
drainage system. Without this information, staff is unable to determine whether the
applicant's proposal will comply with this Condition.
42. Condition 48: Each phase of the project shall be designed to intercept and remove from
the street structural section and subgrade the flows from all known and unknown springs
and watercourses encountered for street construction and lot pad grading, if any
performed by the developer. Saturation of the street subgrade and building pads must
be prevented. This condition has not been fully satisfied in the applicant's Tentative
Subdivision submittal in that the tentative plan and the Stormwater Evaluation do not
adequately identify the location of the longitudinal drains proposed by the applicant or
the trench drainage measures required pursuant to Master Plan Condition 19. Without
this information, staff is unable to determine whether the applicant's proposal will comply
with this Condition.
RECOMMENDED CONDITIONS OF APPROVAL:
1) In order to comply with SDC 32.010(1) and 35.060 when there are multiple panhandle
lots, private utilities, including but not limited to: sanitary sewer, stonn sewer; water and
electricity must be installed by the developer prior to the recording of the Subdivision
Plat.
2) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the applicant shall demonstrate that the stonn sewer
laterals provided for each lot can provide conveyance for roof drains, building foundation
drains, and private property surface and underground drainage.
3) Prior to approval of any construction plans or final subdivision plats for the Phase 4
MountainGate development, the applicant shall obtain City Engineer approval of a
Drainage Study prepared in compliance with the Stonnwater Capacity design standards,
attached hereto and made a part hereof, and that accounts for all of the surface and
subsurface flows that are required to be addressed pursuant to the Master Plan
approval.
4) Prior to approval of any construction plans or final subdivision plats for the Phase 4
MountainGate development, the applicant shall design the trench drainage measures to
I:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
ORe STAFF REVIEW: 2-26. .
MOUNTAIN GATE PHASE 4
Page 17 of21
the satisfaction of the City Engineer to fully incorporate all of the provisions of the Master
Plan, the findings and conditions of approval adopted by the Hearings Official, and all
. other recommended conditions of approval that are prepared for the Phase 4
subdivision proposal.
5) Prior to approval of any construction plans or final subdivision plats for the Phase 4
MountainGate development, the applicant shall submit a revised wetland delineation
and mitigation plan, approved by the Division of State Lands and the US Army Corps of
Engineers, with the associated approved permits for wetland fill and removal.
6) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the developer and the City shall enter into an agreement
specifying responsibilities for the long-term access and maintenance of the storm
drainage detention and water quality ponds.
7) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the applicant shall submit a site specific geotechnical
evaluation, prepared by an Oregon registered geotechnical engineer, that is based upon
the project design and Master Plan conditions and requirements.
8) Prior to approval of any construction plans or final subdivision plats for the Phase 4
Mountaingate development, the applicant shall submit construction plans bearing the
professional engineers stamp of the Oregon registered geotechnical engineer
responsible for the geotechnical aspects of the project design and the construction
plans.
9) Pursuant to Master Plan Condition of Approval, and prior to the approval of any
construction plans or final subdivision plats for the Phase 4 Mountaingate development,
the applicant shall design the storm drainage facilities including storm water quality Best
Management Practices and subdivision lotting and layout to fully incorporate all of the
provisions of the Master Plan, the findings and conditions of approval adopted by the
Hearings Official, the Stormwater Quality Design Standards attached hereto and made a
part hereof, and all other recommended conditions of approval that are prepared for the
Phase 4 subdivision proposal.
SUBDIVISION STANDARDS rS.D.C. ARTICLE 351:
~ Tentative Plan - Site Assessment Requirements [S.D.C. 35.040-2]
FINDINGS:
A Site Assessment plan was submitted for DRC review; however, the plan needs additional
detailed information regarding the existing conditions. A complete Site Assessment plan
must be submitted with the development plans or LDAP application and include the
following detailed information:
a. Site Assessment of existing conditions must show location, direction of flow, and top of
banks of all jurisdictional drainages. Army Corps of Engineers approval and permit is
I:\Mountaingate\SUB2003~00062 Mountaingate Phase 4 DRC Letter.doc
DRC STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 18 of21
required for all jurisdictional drainages indicated on plans.
.
.
b. Site Assessment of present existing road conditions must clearly be shown on the plans.
The plans must clearly indicate existing cut, fill, and embankment locations, depths, and
specifications of existing materials at proposed public road locations. This is required in
order to adequately review existing conditions and parameters for proposed public road
construction.
c. Site Assessment of existing conditions must include location, direction of flow, and top
of banks of all existing wetlands and mitigated wetlands as delineated and approved by
Oregon Division of State Lands.
d. Site Assessment of existing conditions physical features including, significant clusters of
trees and shrubs, riparian areas, wetlands and rock outcroppings - indicate whether
they will remain or be removed or altered by the proposed development.
e. Site Assessment of existing conditions soil types and water table information as mapped
and specified in the Soils Survey of Lane County.
RECOMMENDED CONDITIONS OF APPROVAL:
1) Prior to the approval of the subdivision plat, the applicant shall submit a detailed Site
Assessment plan clearly indicating existing conditions as outlined herein.
}- Comply with Master Plans (Metro, Refinement, Green way, Streets, Sanitary,
Drainage, etc.) .
Official, in his decision on the MountainGate.MasterPlan, Joumal No. 95-02-39, dated May
13,1998, made the following Decision (MasterPlan page 15 of 42): "The request (Jo. No.
95-02-39) for master plan approval for the MountainGate subdivision is conditionally
approved Prior to submitting any development applications pursuant to the approved
master plan, the applicant shall provide a revised Conceptual Master Plan incorporating the
following conditions of this Decision:" herein.
Section 1.01 FEES AND PERMITS
SYSTEMS DEVELOPMENT CHARGE:
}- Pay a Systems Development Charge when the building permits are issued for
developments within the City limits or within the Springfield Urban Growth
Boundary. (The cost relates to the amount of increase in impervious surface
area, transportation trip rate, and plumbing fixture units. Some exceptions apply
to Springfield Urban Growth areas.) [Springfield Code Chapter II, Article 11]
SDC's are collected with private construction permitting. Until development
proposals are submitted, no estimate of the SDC's can be prepared.
SANITARY SEWER IN-L1EU-OF-ASSESSMENT CHARGE:
}- Pay a Sanitary Sewer In-Lieu-of-Assessment charge in addition to the regular
I:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 DRe Letter.doc
ORe STAFF REVIEW, 2-26__
MOUNTAIN GATE PHASE ~
Page 19 of2I
.
connection fees if the property or portions of the property being developed have
not previously been assessed or otherwise participated in the cost of a public
sanitary sewer. Contact the Engineering Division to determine if an In-Lieu-of-
Assessment charge is applicable. [Ordinance No. 5584] (The current rate is $0.35
per square foot of land.)
PUBLIC INFRASTRUCTURE FEES:
~ The private developer funds public infrastructure.
OTHER CITY PERMITS:
~ Encroachment Permit or Sewer Hookup Permit (working within right-of-way or
public easements) example: new tap to the public storm or sanitary sewer, or
adjusting a manhole. [The current rate is $120 for processing plus applicable
fees and deposits]
An Encroachment Permit is required for all work in public easements and rights-of-
way.
~ Wetlands, Erosion Control, Flood Plain, Land & Drainage Alteration Permits
[Contact the Springfield Development Services Department]
Land & Drainage Alteration Permits are required for all construction that will disturb
50 cubic yards or more of material on a site or more than 5,000 square feet of
surface area.
ADDITIONAL PERMITS/APPROVALS MAY BE NECESSARY:
~ Metropolitan Wastewater Management Commission (Pump station, sanitary
sewers 24 inches or larger)
~ Lane County Facilities Permit (If the project is within Lane County jurisdiction)
~ Railroad (If the project crosses a railroad)
~ Oregon Department of Transportation (If the project is within ODOT
jurisdiction)
Will be required.
~ Division of State Lands (Storm water discharge, wetlands)
Will be required. .
~ Oregon Department of Environmental Quality (Erosion control (5 acres or
greater), pump station, storm water discharge, wetlands)
Will be required.
~ U.S. Army Corps of Engineers (Storm water discharge, wetlands)
Will be required.
ENGINEERING CHECKLIST
NOTE: The following is a checklist of items to confirm before submitting plans for
building permits. Please use this as a guide to help expedite the Public Works
Department review process. The stars (**) represent items that must be
completed before the building permits can be issued.
1:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 ORe Letter.doc
ORe STAFF REVIEW: 2-26-04
MOUNTAIN GATE PHASE 4
Page 20 of21
.
.
o Comply with the Development Review Committee requirements.
o **Show all easements (size and location) on the plans. No building can be
constructed within an easement.
o **North arrow and scale of drawing.
o **Show the property lines to scale and label the dimensions.
o ** Show the location of the following existing items: utilities, catch basins,
street lights, structures, topography, curbcuts, handicap ramps, street edge or
curbs from property line, sidewalks, condition of sidewalks & pavement, street
names and special features - Le. wetlands, trees, flood plain/way, drainage way,
etc.
o **Show the location of the proposed items: structures or additions, driveway
width & curbcuts, parking lot, street lights, drainage systems - include future site
grading, sanitary sewer systems (private utilities must be outside of public
easements).
o **Showa detailed drainage plan that includes existing and proposed: drainage
systems; contours; grades; up-gradient flows/impacts; down-gradient
flows/impacts; drainage area map; and hydrologic and hydraulic calculations to
support the proposed drainage design. Parking lots having 5,000 square feet or
more of paved surfacing must address Springfield Development Code 32.110(4)
[see below - Drainage Best Management Practices.]
PUBLIC WORKS DEVELOPMENT AGREEMENT REQUIREMENTS:
..
1. Oil/water separator catch basins, if approved by the City, and other drainage
systems are required to be checked and cleaned to remove pollutants as needed
(at least once a year, usually in September). All waste material must be disposed
of in a lawful manner. The owner/developer must document the maintenance
activities at the site and to have the documents available on site for the City of
Springfield to inspect and review.
2. Site drainage must drain to an approved drainage way with sufficient capacity
to accept the discharge. Surrounding property drainage, which drains onto the
newly developed property, must be incorporated into the grading and drainage
plan.
DRAINAGE BEST MANAGEMENT PRACTICES
[Springfield Development Code 32.110(4)]
1. Temporary ponding of water
2. Permanent storage basins
1:\Mountaingate\SUB2003-00062 Mountaingate Phase 4 ORe Letter.doc
ORe STAFF REVIEW: 2-26_
MOUNTAIN GATE PHASE 4
Page 21 of21
.
3. Minimizing impervious surfaces
4. Emphasizing natural water percolation and natural drainage ways
5. Preventing water flowing from the roadway in an uncontrolled fashion
6. Stabilizing natural drainage ways as necessary below drainage and culvert
discharge points for a distance sufficient to convey the discharge without channel
erosion
7. On-site filtration or skimming of run-off that will enter natural drainage ways to
maintain water quality
8. On-site constructed wetlands and water quality ponds
9. Biofiltration systems
10. Sheet flow (drainage passing over landscape areas before entering drainage
systems)
11. Parking lot drainage passing through oil/water separators with coalescing
plates, filters, and/or multiple chambers
12. Roof drainage to a dry well with an overflow to the storm system
13. Drainage passing through compost or sand filtering systems before entering
the storm system
1. Truck wells or loading areas should have a storm sewer system shut off valve with a visible
sign within the dock area explaining the location and procedure for using the valve. If
feasible, construct a covered truck loading area with a sanitary catch basin system that has
a shut off valve. The sanitary sewer valve will normally be in the "off' position.
l:\Mounlaingate\SUB2003-00062 Mountaingate Phase 4 ORe Letter.doc
.
.