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HomeMy WebLinkAboutA7 - Utility Report Stamped 1 TABLE OF CONTENTS Introduction ..................................................................................................................................... 3 Location ................................................................................................................................ 3 Existing Land Use ................................................................................................................. 3 SANITARY SEWER SYSTEM ..................................................................................................... 4 Sanitary Sewer Connectivity................................................................................................. 4 Local Sanitary Sewer System ............................................................................................... 5 Wastewater Loading Rates ................................................................................................... 5 WATER DISTRIBUTION SYSTEM............................................................................................. 7 Regional Water Distribution Plan and Connectivity ............................................................ 7 Proposed Development Design ............................................................................................. 8 SHALLOW UTILITIES ................................................................................................................. 9 CONCLUSION ............................................................................................................................. 10 REFERENCES ............................................................................................................................. 11 Exhibits A. Holy Cross Energy Will Serve Letter B. Black Hills Energy Will Serve Letter C. CenturyLink-Lumen Technologies Will Serve Letter D. Spring Valley Sanitation District Will Serve Letter 2 Vicinity Map 3 INTRODUCTION This report was prepared for an application to amend the subdivision Preliminary Plan and Planned Unit Development (P.U.D.) zoning to reflect the removal of the land west of County Road 114 from the P.U.D. The land west of County Road 114 in the previous application has been conserved and sterilized for agricultural uses and open space. The current amendment application is for 94 residential units in total. This reflects a reduction if 42 residential units from the approved Preliminary Plan that was last amended in 2016. Location The 203.7-acre Lake Springs P.U.D. is a proposed residential development located in within Sections 33 and 34 of Township 6 South, Range 88 West of the 6th Principal Meridian and Section 4 of Township 6 South, Range 88 West of the 6th Principal Meridian in Garfield County, Colorado. County Road 114 runs north to south through the west boundary of the existing property. County Road 114 intersects County Road 115 about 250 feet north of the property. The project is bounded by two separate parcels owned by the Colorado Mountain College to the south and east. Rivendell Distribution is located to the west of property. There are also some other private properties located to the west, north, and east of the property. The service area considered for sanitary sewer and water analysis in this report consists of the proposed Lake Springs P.U.D. and potential offsite flows. The proposed site will contain 84 single- family lots and 10 multi-family housing lots, resulting in 94 homes. Existing Land Use The project site is currently mostly undeveloped land and is covered with grasses, and woody stemmed plants. The land currently has a few small structures that will be removed with the proposed development and a few historic structures that will remain within open space parcels. The property includes the existing County Road 114 corridor contained within a 60’ easement and an existing pond along the east side of the County Road. A series of narrow ranch roads cross the property which will be removed from the proposed development. 4 SANITARY SEWER SYSTEM Sanitary Sewer System Connectivity There is an existing 15-inch sanitary sewer main located adjacent to the western property boundary of the proposed site in a 30-foot easement. The sanitary sewer runs from the north to the south, ultimately discharging to the Spring Valley Sanitation District sewage treatment plant that is operating at a small fraction is the plant’s capacity of 500,000 gallons per day. The Spring Valley Ranch sanitary sewer main was constructed based on the full build-out of the Lake Springs P.U.D. (originally planned for 210 units [194 single family and 16 multi-family]) as well as the entire Spring Valley Ranch (which was to include 500+ lots). See Exhibit D for the will serve letter provided by Spring Valley Sanitation District. The proposed development will connect to the existing 15-inch sanitary sewer segment that runs along County Road 114 in two locations. The existing projected volume of sewage flow entering the existing 15-inch segment of mainline during average daily flow is projected to be 0.065 cfs and the peak hour flow is projected to reach 0.163 cfs based on 300 gallons per day per dwelling unit assuming a typical home with 4 residents for all of the proposed units. A peak flow factor of 2.5 multiplied by the average daily flow was used to determine the peak discharge into the sanitary sewer main at the connection to Lake Springs P.U.D. A 16-hour day was assumed for the calculations of the average day and peak hour flow. Therefore, the plant will remain well below capacity with the proposed Lake Springs P.U.D. addition. According to the wastewater treatment plant operator, the existing 15-inch sanitary sewer main is also currently running at a very small portion of its capacity at the lowest tie-in location near the CMC campus. There are currently no measured flow rates on the existing pipe. The estimated allowable capacity of the 15-inch sanitary sewer main is 2.89 cfs flowing at 80% capacity at a grade of 0.21-percent. The main was sized to function as the sole collection pipe to service future growth within the Spring Valley Ranch area down to the plant. The 0.163 cfs peak flow from Lake Springs P.U.D. would make up only about 5.6% of the existing pipe design capacity. Therefore, the potential offsite flows and the flows generated by the proposed development can be 5 conveyed by the existing and the proposed system of gravity sewer piping to the existing wastewater treatment plant. A new inline manhole will be required for one of the 2 connections to the 15” existing pipe and one existing manhole will need to be reworked to add a new 12” pipe connection. Local Sanitary Sewer System All of the proposed development in Lake Springs P.U.D. lies uphill of the existing mainline or its proposed extensions and no internal lift stations are required. The proposed sanitary sewer system for the Lake Springs P.U.D. residential development will service 84 single family units and 10 multi- family units. Preliminary layouts of the local streets, grading, and utility alignments were used to determine the sanitary basin boundaries. Laterals and interceptors of 8-inch and 12-inch diameter sewer line form a network of sanitary sewer piping that will eventually carry flows to the existing 15-inch diameter mainline in three different locations. A table of the proposed sanitary sewer lengths required to service the proposed development can be seen in Table 1 below. Table 1, Sanitary Sewer Improvements Required to Service Lake Springs P.U.D. Improvement Description Length of Line Size of Line Gravity Sewer 12,722 feet 8-inch and 12- inch Wastewater Loading Rates The sanitary sewer pipe sizing is based on the Spring Valley Sanitation District design guidelines. The average sanitary sewer flow rate for single-family residential developments is 300 gallons per dwelling unit per day. The 10 multi-family units were also assumed to have an average sanitary sewer flow rate of 300 gallons per dwelling unit per day. Peak factors associated with sanitary sewer loading rates were assumed to be 2.5. All sanitary sewer pipes were sized for a Peak Hourly Flow, which is the Average Day Flow, not including infiltration, multiplied by the Peaking Factor. The total Average Daily Flows, including a Peak Hourly (Design) Flow for the sanitary sewer system are summarized in Table 2 below. 6 Table 2, Lake Springs P.U.D. Sanitary Sewer Loading Rates Land Use Maximum Dwelling Units (DU) Loading Rate Gpd/DU Total Ave. Daily Flow Gpm Peaking Factor PF Peak Hour Flow Gpm Single Family Attached BASIN A 7 300 2.19 2.5 5.47 Single Family and Multi Family Attached BASIN B 87 300 27.19 2.5 67.97 TOTAL 136 29.38 2.5 73.44 Table 3 details the predicted sewer demand for each of the proposed 2 sanitary basins connecting to the 15-inch existing pipe and tabulates the flow totals for both the average daily and peak hour flows. The capacities in the 8-inch and 12-inch diameter pipes were determined throughout the proposed site and at the tie-in locations to the existing 15-inch sanitary sewer mainline. The estimated average daily flow from the proposed site that is being routed to the existing 15-inch diameter sanitary sewer mainline is 0.065 cfs and the peak hour flow from the proposed site that is being routed to the existing main from the site is 0.164 cfs. The combined flow from the existing parcels and the proposed site at the farthest downstream tie-in location along the existing 15-inch sanitary sewer main will be well below the pipe’s capacity during average day and peak hour demands of 2.89 cfs flowing at 80% capacity at a grade of 0.21-percent. This average daily flows and peak hour flows from the proposed preliminary plan is a 30.1% reduction in the flows from approved preliminary plan. The proposed sewer pipe network capacities are reflected in Table 3. 7 Table 3, Lake Springs P.U.D. Sanitary Sewer Demand by Basin Lake Springs P.U.D. Basins Max.# Units Peak. Hour (gpm) *** Pipe Size % Full Sub Basin A1 35 27.35 8” dia. 11.1% Sub Basin A2 52 40.63 8” dia. 14.0% Combined Basin A 87 67.98 12” dia. 8.6% Basin B 7 5.47 8” dia. 3.5% Total All Basins 94 73.44 ** Capacity calculations based on minimum pipe slope assumed 0.5% WATER DISTRIBUTION SYSTEM Regional Water Distribution Plan and Connectivity The proposed development, Lake Springs Ranch P.U.D., will not connect to any existing regional water districts or facilities. There are no plans for any future expansion of the proposed water system for offsite properties. The Lake Springs Ranch P.U.D. development will be served by Carbondale Fire Protection District and its closest fire station near the intersection of State Highway 82 and County Road 154. There are no fire hydrants in the area that are close enough to the property for use to fight a house fire on the property. The proposed fire hydrant placement is designed to provide all the necessary coverage for the 94 residential units. 8 Proposed Development A new community water system is to be installed to provide fire protection, irrigation, and domestic use for the 94 units proposed in the development. The proposed system will be supplied from two onsite wells that have been tested for a recoverable flowrate of 115 gpm and 100 gpm. The well pumps will be up a pair of separate 4” water lines up to a water treatment building just south of the wells for water quality treatment. A single 4-inch water storage tank supply line will transfer water from the water treatment building up the proposed road network about 1,500 feet with an elevation climb of 118 feet before injection into the 350,000 gallon storage tank. This tank size is a reduction of 50,000 gallons from the previous approved preliminary plan due to the reduction in demand from the removal of 42 residential units. The water will receive the necessary chorine contact time in this 4” pipe up to the tank. The proposed storage tank is located on Tank Road which is a gravel service road serving off of High Alpine Drive. The tank will provide water to all of the 94 residential units through a series of 12 inch and 8 inch water lines. There will be 2 pressure zones in the system due to the high elevation change on the property. A pressure reducing valve will be located on Lake Springs drive above the 18 lots in Block 1 of the development. The Average Daily Demand for residential use was developed by using the proposed layout and the typical water demand rates of 350 gallons per day per dwelling unit (gpd/DU) for single family and multi-family lots. The water demands were based on a 16-hour day. Additionally, an irrigation demand of 58.5 gpm, which is based on 2,500 square feet of irrigated landscaping per lot during the month of June was also added to this number. Should the water storage tank be emptied due to a line break, the recovery time to refill the tank will be approximately 39 hours. This is based on a pumping rate of 150 gpm in the proposed 4-inch supply line. A 93 gpm pumping rate from the water treatment building is necessary to maintain a full water tank storage during the irrigation season. The final water report and community water system application for the State of Colorado will provide all of the WaterCAD analysis. 9 The proposed system within the Lake Springs Ranch P.U.D. residential development will be designed with one 12-inch C-900 diameter trunk line which reduces to 8” C-900 mains according to the needs of the system as listed in the WaterCAD analysis. Condition #13 of the 2016 Preliminary Plan Amendment resolution (Resolution No. 2016-35) asked that the water system be looped. There are portions of the higher elevations of water system that are now looped in order to get the required fire flow according to the estimated house size and fire rating for the single-family houses. However, there is no great benefit to the system pressures to loop the lower portion of the system since there is already a pressure reducing valve on the 8” water main just above where a potential lower loop could occur between the pipes in Van Cleve Lane and Lake Springs Drive. A looped connection line at this location would have also required a second pressure reducing valve vault on the Van Cleve Lane pipe and there would be only a minor benefit to the pressures of the homes below a tee. Therefore, the applicant is asking that this condition be eliminated due to the changes to the water system design layout. Each single-family unit shall have a single 2-inch diameter water service stub for irrigation and domestic use. The townhomes can be served with an ¾” water service. All fire hydrants, valves and other appurtenances shall be constructed in accordance to the Garfield County Unified Land Use Resolution of 2024 and international fire code. SHALLOW UTILITIES The Lake Springs Ranch P.U.D. will connect to existing telephone, gas, and electric lines. Holy Cross Energy will serve the site with electricity. A will serve letter is included as Exhibit A. The proposed development will tie into existing electric overhead power lines that run east to west near the southern boundary line. A portion of these overhead lines will be replaced with underground lines within most of the property boundary in order to not negatively impact the proposed lot layout. A second overhead electric line extends north on the neighboring Rivendell Distribution property on the west side of County Road 114. This second overhead line will also be replaced with a new underground electric alignment where it crosses the subject property and County Road 114. This line will go back to overhead electric at an existing power pole near the 10 current entrance to the Rivendell Distribution property before continuing north across the Rivendell Distribution property as per existing. Black Hill Energy will provide the proposed development with gas service. See Exhibit B for the will serve letter. The nearest Black Hills Energy facility is a regulator station on the Colorado Mountain College property to the southwest of the nearest proposed lots for Lake Springs Ranch P.U.D. A 4-inch diameter gas line is required to be extended along an existing Black Hills Energy gas easement on the Colorado Mountain College property and then up the east side of the right-of- way of County Road 114, a total of about 5,050 feet. Any future extensions to the north beyond the development would need to extend up County Road 114 off the 4-inch loop. Black Hills Energy will require a 4-inch loop up County Road 114 within the subject property and around Lake Springs Drive. All of the other dead-end lines would only need to be 2-inch in diameter. CenturyLink-Lumen Technologies will be the provider of fiber optic phone and data service. See Exhibit C for the will serve letter. The nearest location of the existing phone network is at the turn in County Road 114 north from the main part of campus and the Pinyon Pines Apartments. The fiber optic line would also be installed on the east side of County Road 114 off the paved surface in the right-of-way for a length of about 3,600 feet to the first lots of the proposed development. CONCLUSION This utility report was prepared in compliance with the Garfield County standards and specifications. It presents the proposed sanitary sewer and water distribution system layout with consideration of the Spring Valley Sanitation District system capacity and the flowrates of the well pump tests performed in 2023 by Zancanella and Associates. The proposed sanitary sewer system will provide adequate capacity to serve the proposed residential development. The proposed water distribution system will meet peak hour demands and maximum day demands plus fire flow while maintaining adequate flow and pressure. The existing segments of sanitary mainline, to which the Lake Springs Ranch P.U.D. development will connect, has been demonstrated to be adequate. The cost of extending service to the subject property is the responsibility of the applicant for each of the utilities. 11 REFERENCES International Fire Code: International Code Council, 2021. International Building Code: International Code Council (ICC), 2018. WaterCAD v8.0: WaterCAD for AutoCAD, Haested Methods Solution Center, Waterbury, CT, 2025.