HomeMy WebLinkAboutLDS TEMPLE (OF FORT COLLINS) - FDP - FDP130029 - REPORTS - DRAINAGE REPORTFINAL DRAINAGE REPORT
FOR THE CHURCH OF JESUS CHRIST
OF LATTER DAY SAINTS TEMPLE,
FORT COLLINS, COLORADO
Prepared for:
Church of Jesus Christ of Latter Day Saints
50 E. North Temple Street, 10th Floor
Salt Lake City, Utah 84150-6300
Contact: Mark Tingey P.970.391.0212
mtingey@comcast.net
September, 2013
Project No. ARCHNE-1L8A-01-301
Consulting Engineer
LANDMARK ENGINEERING, LTD.
3521 West Eisenhower Blvd.
Loveland, CO 80537
Ph: (970) 667-6286/Toll Free (866)-379-6252
TABLE OF CONTENTS
SECTION 1 - EXECUTIVE SUMMARY ............................................................... Page No.
Introduction ............................................................................................................................. 1-1 & 1-2
Findings, Conclusions and Recommendations ............................................................................ 1-2
1) Existing Drainage Patterns
2) Proposed On-site Drainage Patterns & Storm Drainage System
3) Constructed Wetland Channels, Detention & Water Quality Facilities
SECTION 2 - PROJECT HYDROLOGIC DESCRIPTION
Major Basin Paths & Topographic Description ........................................................................... 2-1
Drainage Basin Map
Vicinity Map
SECTION 3 - DRAINAGE FACILITY DESIGN
General Concept ............................................................................................................................... 3-1
Details for On-site Storm Drainage Systems ............................................................... 3-1 to 3-11
SECTION 4 – DETENTION / WATER QUALITY PONDS & NATURAL AREAS
Detention Ponds ............................................................................................................................... 4-1
Water Quality Ponds ........................................................................................................................ 4-2
Constructed Wetland/Natural Channels ..................................................................................... 4-2
SECTION 5 - SOILS
Natural Resources Conservation Service .................................................................................... 5-1
Soil Map
SECTION 6 - EROSION CONTROL REPORT
Erosion Control .................................................................................................................... 6-1 to 6-5
References ........................................................................................................................................... 6-6
APPENDIX
City of Fort Collins Drainage Standards
City of Fort Collins Flood Plain Review Checklist
Detention Pond Calculations
Basin Calculations
Historic Basin Calculations
Storm Cad – Pipe & Inlet Run Calculations
Street Capacity, - UD-Inlet & Nyoplast Inlet Calculations
Outlet & Swale Protection Calculations
Map Pockets:
Historic Drainage Exhibit
Developed Drainage Plan
Erosion Control Plan
Detention Pond Outlet Structure Details
Natural Habitat Buffer Zones
6-1
SECTION 6
EROSION CONTROL REPORT
CURRENT SITE CONDITION
The existing site encompasses 35.6 acres and was acquired by the Church of Jesus Christ of
Latter Day Saints (LDS) in year 2011. It is bordered on the west by Timberline Avenue, on the
north by Trilby road and on the south by a private drive (Rock Castle Lane). It is in the
Northwest Quarter of Section 17, Township 6 North, Range 68 West of the 6th Principal
Meridian. With the exception of one single family residence that will be demolished, the
property is fallow cropland and is now covered in native grasses and sparse alfalfa, with an
assortment of trees near the property lines of the two roadways. Because the one existing
residence/driveway area is less than 0.3% of total site, the total site is considered vegetated.
NATURE AND PURPOSE OF CONSTRUCTION
The Church of Jesus Christ of Latter Day Saints (LDS) will construct a temple and related
facilities on the northwest 15.7 acres of the site. The project will consist of a Temple structure,
a Temple President’s parsonage, a stand alone mechanical enclosure, maintenance/utility building,
parking, drainage facilities, and utilities. There is one proposed road (Majestic Drive) that will
encompass the south and east sides of the Temple site, connecting Timberline Road to Trilby
Road. The main vehicular access to the site will occur from two commercial style driveways
that will loop through the parking lot that is situated south of the Temple. Various pedestrian
walks also extend to the Temple and parking lot from all of the surrounding roads.
Because of earthwork grading and stockpiling activities, approximately 31 acres of the 35.6 on-
site acres sight will be disturbed. In addition, approximately 3.5 off-site acres will be disturbed
on the north and west sides of the site and will involve on-site street connections to Trilby
Road and road improvements to Timberline Road.
All stormwater runoff will be to either: (1) along Timberline road to the Fossil Creek
wetlands/open space area about 0.54 miles to the south which, in turn, flows to Fossil Creek
Reservoir; or (2) to the Westchase Tract N detention pond which flows into Fossil Creek
Reservoir, or (3) to the southeast corner of the site, then south through existing drainage
ditches to the west end of Fossil Creek Reservoir located about 0.4 miles to the south of the
site. Any water release from Fossil Creek Reservoir flows east under Interstate 25 and to
irrigated cropland east of the interstate, eventually reaching the Poudre River which is located
1.4 miles east of Fossil Creek Reservoir.
RAINFALL ERODIBILITY & EROSION SEDIMENT CONTROL METHODS
Temporary and permanent erosion and sediment control measures will be required for the site.
Initial grading operations will result in vegetation removal and transport of soils both on and off-
site to achieve final subgrades. The work will expose significant portions of the site to erosion
from precipitation and wind. As a result, temporary erosion and sediment control measures will
be needed to minimize impact to adjacent properties during the initial grading, during
infrastructure and utilities construction, and during vertical structure construction.
This site will require a Fugitive Dust Control Permit. If dust becomes a problem during
construction, the problem areas will be watered on an as needed basis.
6-2
Permanent erosion and sediment control measures will be provided to minimize longer term
erosion and sediment transport, and to provide detention facilities with water quality
enhancement.
An Erosion Control Plan sheet is included in the Final Utility Plan drawings for this project
showing the proposed erosion control measures for the following construction phases:
1. Prior to construction and during grading,
2. During infrastructure and utility construction,
3. During individual structure construction, and
4. Final stabilization.
The Erosion Control Plan will need to be referenced for all phases of construction and modified,
if necessary, during construction to mitigate unanticipated erosion and sediment transport issues
that may arise. The choices for erosion control are shown below in the following section.
Non-stormwater discharges may occur during utilities installation. Soils boring information
indicates fluctuating groundwater levels that may be encountered, requiring dewatering
operations. If encountered, the required state permits will be acquired, and any groundwater
discharge will be routed to proposed on-site detention basins. Ultimate release of non-
stormwater discharges from detention basins will be to the Timberline Road drainage swale or
to the drainage way to the Westchase Tract N detention pond.
Information regarding soils borings, groundwater levels and laboratory testing can be found in a
report titled “Geotechnical Engineering Report, Fort Collins Temple Southeast of South
Timberline Road and East Trilby Road, Fort Collins, Colorado” dated June 24, 2013, Terracon
Project No. 20115025, prepared by Terracon Consultants, Inc., Fort Collins, Colorado.
STORMWATER MANAGEMENT CONTROLS (SWMC)
Multiple best management practice (BMP) stormwater controls will be required for this project.
The sequencing for both temporary and permanent erosion control is shown on the utility
drawing’s erosion control plan. Temporary controls include the following:
- Vehicle tracking control pad.
- Silt fencing to minimize downhill sediment transport on the east and south sides of the
site, and around the topsoil stockpile area.
- Watering operations for dust abatement.
- Weighted coir wattles for curbside check dams.
- Weighted coir wattles for curb inlets.
- Staked coir wattles for area (drop) inlet controls.
- Gravel berms at detention basin outlets.
- Concrete washout area.
- Temporary erosion control mat.
- Disturbed area seed mix (topsoil stockpile area).
Permanent erosion controls include the following:
- Turf reinforcing mat.
- Revetment scour protection mat.
6-3
- Landscape work (grass sod, vegetation, mulch, etc.)
- Sidewalks, curb & gutter, pavement.
The Storm Water Management Plan (SWMP) Administrator will be responsible for directing the
installation and maintenance of temporary and permanent erosion control facilities. In addition,
the administrator will be responsible for preparing the necessary bi-weekly and/or storm
occurrence and maintenance reports. The administrator for this project is:
Name: ____________________________________________________________
Position/Title _______________________________________________________
Address: __________________________________________________________
Phone Number: _____________________________________________________
Cell Phone Number: __________________________________________________
Email Address: ______________________________________________________
The primary pollutant source from this project will be sediment and dust transport resulting
from site development. There are no known contaminated soils on the site, and the SWMP
Administrator will take the necessary actions to prevent any soils contamination from on-site
equipment repair and servicing, routine maintenance activities, and materials storage
(construction materials, pesticide, fertilizer, etc.). If soils become contaminated from on-site
activities, the contaminated soils will be removed from the site and disposed of per city, county
and state requirements.
Asphalt and concrete plants are readily available in the Fort Collins area, and no dedicated
asphalt or concrete batch plants will be located on the site.
To minimize off-site sediment tracking, the locations for employee parking, portable toilets,
worker trash disposal, construction materials staging, vehicle/equipment maintenance and
refueling should be near the construction site entrance on Trilby Road. Construction of
temporary gravel pads may be required to minimize sediment transport to Trilby Road.
Special attention should be given to insure routine maintenance activities involving fertilizers,
chemicals, detergents, fuels, soluble oils, etc., do not create pollution issues. Storage of these
and similar items may require temporary shelters with pallets on raised pads and/or lined and
bermed containment enclosures to minimize soils contamination issues.
Small dumpsters will be used initially for on-site waste management. During vertical
construction of buildings and related facilities, larger waste containers may be required. All
containers should be placed in locations where minimal off-site sediment tracking by haul
vehicles will occur. A local waste management company will be used to supply and remove
containers from the site. Placement of these containers will be determined or approved by the
SWMP Administrator.
Initial best management control measures will include installation of the vehicle tracking control
pad and silt fencing before heavy equipment unloading and earthwork operations begin. The
SWMP Administrator will insure sediment is not transferred to Trilby Road, and operations
such as street sweeping and scraping activities may be required to insure Trilby Road is kept
clean.
6-4
During land disturbing activities, dust abatement and erosion and sediment controls will be
implemented. All exposed soils are to be kept in a roughened condition by ripping or disking
along land contours until temporary seeding, mulch, vegetation, or other permanent erosion
control BMP’s are installed. Installation of temporary drainage swales and wattles may be
required during construction as a result of stockpiling soils, and the SWMP Administrator will
assess potential dust, erosion and runoff conditions, taking the necessary measures to minimize
the same. No soils in areas outside project street rights-of-way shall remain exposed by land
disturbing activity for more than thirty (30) days before required temporary or permanent
erosion control (seed/mulch, landscaping, etc.) is installed, unless otherwise approved by the
City of Fort Collins.
A concrete washout pit will be constructed near the site entrance after overlot grading work is
complete or before any concrete placement operations occur. Completion of detention basin
grading and outlet structures will require the installation of turf reinforcing mats and revetment
scour protection mat.
Installation of building foundations and subsurface utilities including storm sewers will require
installation of inlet protecting wattles. If dewatering operations are required, piping and/or
drainage swales will be installed to direct pumped waters to stormwater detention basins.
Curbside check dams will be installed after curb & gutter and pavement installation occurs.
The SWMP Administrator will inspect temporary erosion control BMP’s every two weeks or
after storm events to determine if maintenance, repair or replacement work is required.
Examples where maintenance work is required include silted in detention basins and gravel
berms, torn, leaning, or silted-in silt fences, torn or silted-in wattles, and excessive erosion in
drainage swales. All BMP facilities should be maintained and repaired so that they will function
as required.
After permanent landscaping and BMP’s are installed and become functional, temporary BMP’s
will be removed as directed by the SWMP Administrator.
DRYLAND VEGETATION
The above mentioned Terracon Geotechnical Engineering report showed the following typical
site soils profile:
Topsoil: top ½ foot
Lean clay with sand to sandy silty clay: from ½ foot to about 23 to 27 feet
Weathered claystone bedrock: from 27 feet to 21.5 feet or to max. explored depth.
Claystone bedrock: to max. explored depth of about 40.5 feet.
Landscape drawings prepared for site work call for topsoil to be removed and stockpiled during
earthwork operations. The topsoil will be used in place of a soil amendment.
Temporary seeding of disturbed areas shall consist of the following or approved equal:
Seed Mix for Clay Soils (29lbs/Acre)
(48%) Buffalograss
(10%) Sideoats Grama (Vaughn)
6-5
(4%) Blue Grama (Hachita)
(27%) Western Wheatgrass (Arriba)
(4%) Alkali Sacaton
(7%) Inland Saltgrass
Final site sodding, seeding, vegetation, and mulch requirements for specific site areas are shown
in the landscape drawings for this project. Those drawings show mulch to be decorative gravels
to a three inch depth. The utility drawings erosion control plan shows locations for drainage
swales, detention basins with turf reinforcing mats, and scour protection mats to minimize
erosion and promote vegetation growth.
DETAILED SEQUENCE OF CONSTRUCTION ACTIVITIES
As mentioned above, a detailed sequence of land disturbing activity erosion control measures is
provided on the utility drawings erosions control plan. The plan shows the construction phases
and the erosion control measures required for each phase.
EROSION CONTROL SECURITY CALCULATIONS
Erosion control costs for the site are provided below. The city requires the higher of an
itemized estimate times a 1.5 factor, or an alternate based on $900.00 per acres times a 1.5
factor.
Description Quantity Unit Unit
Price
Total
Price
Concrete Washout Area 1 Each 600 600
Coir Wattles 1,020 Feet 3 3,060
Silt Fence 3,100 Feet 3 9,300
Gravel Filter Dam 70 Feet 20 1,400
Surface Roughening 25 Acres 200 5,000
Vehicle Tracking Control 1 Each 900 900
Seeding & Mulching 30 Acres 500 15,000
Erosion Control Fabric SC 150/250Crosion 3,745 Sq. Yards 4 14,980
Erosion control Fabric P550 474 Sq. Yards 9 4,266
Erosion Control Mat ShoreMax w/SC250 786 Sq. Yards 85 66,810
Total 121,316
Total x 1.5 181,974
Alternate Cost Est. 37 Acres 900 33,300
Alternate cost Estimate x 1.5 49,950
Greater of the two = $181,974.
6-6
References
1. Final Drainage Report for Westchase P.U.D.
Final Approved Report 4/6/01
2. Westchase P.U.D. Construction Plans
P.E. Stamped 1/30/01
3. Urban Drainage and Flood Control District Manual
With amendments unique to Fort Collins adopted December 2011
4. Natural Resources Conservation Service
Web Soil Survey
5. Natural Habitat Buffer Zones Mitigation & Monitoring Plan
LDS Property
Larimer County, Colorado
Design Software
1. Tensar / North American Green
Erosion Control Materials Design Software
2. Flowmaster
3. StormCAD