HomeMy WebLinkAboutNEWTON SINGLE-FAMILY DETACHED - BASIC DEVELOPMENT REVIEW - BDR180019 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE RELATED DOCUMENTKai Kleer August 3rd , 2018
City Planning Department 0309.18
281 N College
City of Fort Collins 80524
RE: 1520 West Vine Drive – Site Drainage and Erosion Control Report - Revised
Dear Kai,
GENERAL INFORMATION
The proposed development located at 1520 West Vine Drive includes the construction of a four
bedroom single family residence on a large vacant lot. The total structure square footage is 2,593
including the two car garage and will be situated on a 1.44 acre site. Access will be utilized from
the existing driveway at 1516 West Vine Drive and onto West Vine Drive. A separate emergency
pervious gravel surface access will be constructed adjacent to the existing 1516 West Vine Drive
and will access onto West Vine Drive.
SITE DRAINAGE
The site is located just north of West Vine Drive and slopes gradually less than 0.33% to the
southeast towards West Vine Drive. Due to the small footprint of the proposed structure and
driveway that are located on 1.44 acres, runoff is expected to be very minimal. There are no
proposed storm sewer or detention pond designed for this site. Drainage is likely to infiltrate into
the soil or gradually migrate to West Vine Drive and very slowly drain to the east.
The impervious area is about 3,200 square feet and approximately 5.2 percent of the lots gross
area. This is well below the 30 percent assumed impervious area of the West Vine Drainage
Master Plan.
As shown in the attachment, the Q100 pre-development runoff from the site is 0.93 cfs versus the
Q100 post development runoff of 1.79 cfs. The additional runoff pre-development versus post-
development is 987 cubic feet of water or 0.02 acre feet.
The site is also located in both the City Floodway and City Flood Fringe. The finish floor, ductwork,
HVAC, and electrical components of the proposed structure will be constructed at an elevation
2.5 feet above the 100 year water surface elevation for that area. For the City Floodway area, all
proposed development will be constructed to the existing elevation or just below the existing
elevation to prevent a rise in the water surface elevation. An elevation certification will be provided
once construction is completed for both the structure and the portions of the driveway constructed
in the floodway.
The structure will be elevated with existing soil material backfilled, compacted and sloping down
from the just below the finish floor at a 4:1 slope to the existing ground. This slope will provide
positive drainage away from the structure.
EROSION CONTROL
Site Description
As described in the drainage section of this report, this project includes the construction of a single
family residence on a large vacant lot. The site is currently vegetated with approximately 95
percent non-native grasses and bordered with numerous trees. The site is and has been used
for grazing and hay production. It is the intent to minimize impacts to the existing trees and
vegetation as much as possible to construct the single family home.
Construction phasing includes installing the erosion control features prior to any other
construction activities. This includes the silt fence, tracking pad and inlet protection devices to
minimize sediment runoff.
Following the installation of the erosion control measures, striping vegetation and topsoil will
follow to the limits for the proposed grading, structure, utilities and access. Topsoil will be stored
in manageable piles outside of the proposed grading areas but inside the silt fence area.
Once the site is stripped, the foundation limits for the house will be excavated and stored inside
the silt fence area. While the contractor is waiting for the concrete to cure and gain strength,
utilities will be installed from the main connection points to the foundation. Typical utility
installation includes excavating the utility trench, installing the proposed utility, backfilling and
compacting. The utility work will be confined within the silt fence limits. Once the foundation
concrete has cured and of sufficient strength, the foundation will be backfilled with the excavation
material.
Once the foundation is backfilled, construction of the home will begin. The proposed home
includes typical framing, sheeting, and standard home construction. The proposed home
construction is common for the area and will minimize erosion control issues.
Conservatively, it is estimated 32,000 square feet or 0.74 acres will be disturbed for construction
purposes. Of the 30,000 square feet, approximately 13,000 square feet will be disturbed for the
major grading and foundation construction, 6,000 square feet will be disturbed for utility
construction, ~4,000 square feet for access construction and ~9,000 square feet of disturbance
for staging areas. Actual disturbance may be less depending on activities. The gross site area
is 1.42 acres, drains to the southeast and will focus most of the erosion control measures in the
0.74 acre area to prevent material from being transported offsite. The receiving waters
downstream is the Cache La Poudre River.
Stormwater Management Controls
Erosion Control measures for the proposed improvements have been shown on the Landscape
and Erosion Control Plan. Erosion control measures include silt fence surrounding and located
just outside the construction limits of the project, tracking pad at the entrance, and inlet protection
for the approach culvert. As stated in the drainage section, the site is relatively flat which will help
minimize sediment runoff. During rain events, sediment will be captured by the silt fence, tracking
pad, and inlet protection measures to prevent from traveling offsite. After rain events, the
stormwater manager will evaluate the site and to determine if best management practices need
to be altered to better accommodate the site conditions.
The site will also include a sediment tracking pad at the construction site exit. This will include
larger aggregate or fabricated pad to be selected by the project Contractor. This will minimize
material being tracked offsite onto West Vine Drive. In the event material is tracked offsite, the
Contractor will be responsible to remove said material and dispose of properly.
The site includes one storm sewer pipe culvert that is located at West Vine Drive and the proposed
emergency access. Straw waddles will be placed at the entrance of the pipe culvert to minimize
sediment entering said pipe culvert. In the event sediment enters the pipe, the Contractor will be
responsible to remove said material and dispose of properly.
The Contractor will modify erosion control measures as necessary for conditions, and construction
phases. The final stages of construction will include seeding and reclamation efforts. Once the
site has been stabilized with final surfacing materials and vegetation, the Owner or Contractor will
be able to remove the silt fence and straw waddles.
SWMP Administrator
Following is the stormwater administrator and his contact information.
Jordan Ishii
Craftsmen Builders
Jordan.prevail@hotmail.com
(970) 416-9300
(720) 641-5912 – mobile
Jordan will be responsible for all aspects of the storm water management plan and implementing
changes as required.
Potential Pollutant Sources
Potential pollutant sources include sediment and typical pollutants associated with construction
equipment. Sediment will be contained on site per the erosion control features and bmp’s
established onsite. During fueling or service of machinery onsite may result in a small fuel spill
or other small pollutants such as grease or other fluids. In the event of a fuel spill or other
contamination, the swmp administrator will identify the area and remove the contaminated
material offsite immediately after it occurs to prevent the material from leaving the site.
Stockpiling of Stored Soils
Stockpiling of dirt during construction may be necessary for the sequencing of construction
activities and should be somewhat minimal and temporary for this site. Stockpiles that are
generated shall be contained within the silt fence area to minimize sediment issues. It is
anticipated stockpile material will be utilized to backfill around the concrete foundation once
concrete strength has been achieved.
Vehicle Tracking or Sediments
The owner and site manager realizes that vehicle tracking of sediments is a major potential
pollution source and will be fully engaged to minimize this risk. A tracking pad will be installed at
the entrance as main mitigation for offsite tracking. The site will also only utilize one entrance/exit
to the site as well. If tracking of offsite material does occur, the swmp manager will remove the
material by scraping and sweeping up of said material. Not only will the site utilize a tracking
pad, but a gravel approach from the tracking pad to the construction site. Said gravel approach
shall be constructed prior to other construction activities.
Management of Contaminated Soils
The owner has not discovered any existing contaminated soils on-site but if discovered during
construction, the swmp administrator will stop construction, notify the Owner, determine what they
are and dispose of properly and legally.
Loading and Unloading Operations
Traffic operations include delivering materials from Vine Drive via the single entrance to the
construction site. Due to small proposed structure, site deliveries will be minor in amount.
Materials will be delivered as needed and required.
Outdoor Storage Activities
Outdoor storage will be minimal as materials will be used as they are delivered. Since the
proposed structure is relatively small, outdoor storage will not be required.
Vehicle, Equipment Maintenance and Fueling Operations
Equipment maintenance and fueling operations will likely occur on a weekly basis but very
minimal due to the size of the construction site. If contamination occurs during maintenance
procedures or operations, the contaminated soil will be removed and disposed of properly.
Significant Dust or Particulate Processes
On site dust can occur during construction but will be controlled by wetting the area frequently.
This will minimize dust pollution generated during construction. Other potential airborne
particulates are not anticipated from the site.
On-Site Waste Management Practices
All waste material will be stored in a covered self-contained industrial dumpster to be stored at a
minimum of 50 feet from any inlet, structures, or watercourses.
Concrete Truck Washout Facilities
No concrete washout facilities will be utilized on-site for this project. All concrete trucks will be
required to clean at their batch plant facility.
Dedicated Asphalt and Concrete Batch Plants
There are no dedicated asphalt and or concrete batch plants planned for this project.
Non-Industrial Waste Sources
Portable toilets will be located onsite but 50 feet from any inlets, drainage features or
watercourses. There are no other non-industrial waste sources anticipated for this project.
Other Potential Spills
No other potential spill sources are anticipated for this project.
Establishment of Dryland Vegetation
Establishment of dryland vegetation is very important to the Owner as they prefer to have
vegetation established as quickly as possible both for aesthetic and erosion control purposes.
The sooner vegetation is established, means less work for the Owner in regards to maintenance.
The existing soil types include clay, sandy, moist to wet, medium stiff, dark brown (CL) in the top
two feet followed by sand/gravel, wet, medium dense to dense brown (SP, GP, GW, SP-SM) to a
depth of 10-15 feet. The topsoil and material excavated for the foundations will be stored
separately from other materials during construction. Once construction is complete, the existing
topsoil will be placed at a thicker depth than original site and will contain seed from the original
vegetation. The Contractor will seed and mulch with an alkaline mix/buffalo grass seed mix for
all exposed areas at a rate of 3.27 lbs/pls/acre. Straw mulch will be weed free and crimped into
the soil to minimize erosion immediately after seed is applied.
It is anticipated that reclamation efforts will be performed in the spring of 2019 taking advantage
of the optimum growing season. The Owner will water intermediately if needed to assist with
germination and plant growth. Once established, the Owner will provide weed control as needed.
Construction Phasing and Sequencing
The construction phasing is as follows:
1) Install pipe culvert extension, tracking pad, gravel approach, inlet protection, and silt
fence. Later Summer/Fall 2018.
2) Clearing, grubbing, topsoil removal for utilities and foundation. Topsoil storage piles
will be created storing materials onsite. Fall 2018.
3) Excavate for foundation, and store materials on-site and out of the way for
construction. Fall 2018.
4) Install utilities, backfill and compact trenches. Fall 2018.
5) Backfill foundation and compact with foundation excavation materials once foundation
has cured. Adjust bmp’s as needed. Late Fall 2018.
6) Vertical construction such as framing, roofing, flooring, windows and all other tasks
associated with normal home construction. Winter 2018/2019.
7) Placing topsoil, reclamation efforts including seeding, mulching, and planting trees.
Later Winter 2019/Early Spring 2019.
8) Once vegetation has been established, the Owner will remove silt fence and inlet
protection devices. Summer 2019.
Fortunately, the site is large enough and the construction activities small requiring little adjustment
to the proposed bmp’s.
Structure Construction
The excavated material in and around the proposed building area will be contained during
construction so sediment is not transported to the parking lot during storm events. This should
be contained by means of silt fence or straw wattles. Dirt that will remain for an extended period
of time shall be covered with reinforced poly plastic sheets ore seeded.
SUMMARY
Due to existing conditions, slopes of the property and comparing the size of the proposed
development to the existing lot, no negative impacts are anticipated for this development or create
issues for adjacent properties.
I appreciate your time and consideration in reviewing this submittal. Please contact me at 970-
420-0086 or kent@avipc.com if you have any questions.
Respectfully Submitted,
AVI PROFESSIONAL CORPORATION
Thomas Kent, P.E.
Appendix
Drainage Calculations