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HomeMy WebLinkAboutWater Supply Evaluation 04.22.2011April 22, 2011 Andrea Korber AIA, LEED AP Land + Shelter, Inc. Architecture Planning Development P.O. Box 550 978 Euclid Ave Carbondale, CO 81623 Re: Water Supply Evaluation, Missouri Heights, Property located in the NE 1/4SE1/4 of Section 19, T7S, R87W of the 6th P.M., Garfield County, Colorado. Sopris Engineering, LLC Project Number 29230.01 Dear Andi: Pursuant to your request, Sopris Engineering, LLC (SE) has reviewed pertinent information regarding the subject property's water well and performed a cursory assessment of reliability for adequate physical water supply from this resource. This evaluation provides our opinion of the feasibility to utilize available water resources from the existing domestic well to support the proposed accessory dwelling unit (ADU) within an existing barn structure at the subject site. In house water for the ADU can be served from the existing development's water distribution system that is supplied by the existing permitted exempt well. Our evaluation is intended to provide support for your applicable permit application and review process for the development of the ADU. Our evaluation is limited to an opinion that the existing well is an adequate water supply for the ADU. Our evaluation is based on addressing the general requirements for adequate water supply pursuant to Garfield County land use code Section 7-104 that requires the applicant to show that allowable uses will have sufficient legal and physical source of water. Legal water resource opinions are not included with this report. We have estimated the average water demands that would be required by the ADU to be 350 gpd equivalent to a single EQR. The property has an existing single family home and barn. The total estimated in-house water demand for the property, including the proposed ADU is approximately 700 gallons per day. The domestic well is permitted for up to 3 single family residences that equates to approximately 1050 gallons per day. Findings The estimate daily water demand for in house use is 700 gpd. The peak summer demand for 1 acre of lawn and garden irrigation is approximately 6800 gpd. The peak summer demand for live stock watering is estimated to be 800 gpd. Therefore the total peak water demand is approximately 8300 gpd. The instantaneous rate required for this peak demand is therefore 5.7 gpm for continuous pumping. To meet peak daily demand the well can pump for approximately 9 hours per day at 15 gpm. A 15 gpm well is more than adequate to satisfy the permitted uses on the parcel. The 38 acre site is located in the Missouri Heights area North of Carbondale. The site is served by an exempt domestic well that has a high production yield. Typical wells in the vicinity have significant production zones within a moderately deep aquifer. Therefore the site's existing well and other wells in 502 Main Street • Suite A3 • Carbondale, CO 81623 • (970) 704-0311 • Fax (970) 704-0313 SOPRIS ENGINEERING • LLC civil consultants Andrea Korber SE Job No.29230.01 _ _• April 22, 2011 Page 2 this area typically produce reliable water quantities year round. The existing permitted well (Permit No. 176510) on site is reported to have a sustained production rate of 15 gpm with a static water level at approximately 130 feet. The well was permitted and developed in 1994 and a well completion report was submitted pursuant to State regulations on 6-27-94. The yield of 15 gpm was reported based on the initial well test performed by Shelton drilling Co. pursuant to test protocol at the time. The existing well completion report indicates the geologic formations consisting of volcanic deposit materials to the boring depth of 180 feet. The report records a sustainable yield is a least 15 gpm. The well is cased to a total depth of 180 feet with plain solid casing to 130 feet and 5.5 inch diameter casing from 130 to 180 feet. The well is permitted for three single family dwellings, up to 1 acre of irrigation, fire protection and watering of domestic animals. The well is permitted for a maximum production rate of 15 gpm and meets the criteria for an exempt domestic well for the uses described above. A well test was performed by J & M Pump on March 1, 2011. The results of the 27 -hour test indicate that the well has a minimum sustained production rate of 15 gpm with extremely limited drawdown. The full recovery to the initial static water level occurred with 12 minutes. The total draw down was only 2 inches. The test indicates that the well is sustainable and can supply adequate water supply at the maximum pumping rate of 15 gpm allowed by the permit. A recent analysis of the well water was performed at the time of the well test by Grand Junction Laboratories to assess the water quality with regard to certain, state drinking water standards and EPA maximum containment levels. The sample was tested for TSS, Nitrate, Nitrite and E. Coli. The water analysis report indicates that wet chemistry and inorganic parameters tested is within expected ranges and does not exceed any EPA/State maximum containment levels. The water quality analysis results appear to be characteristic of the moderately deep groundwater sources in the vicinity. Conclusions A reliable physical water supply for all permitted uses that include the existing single family residence, the proposed ADU, up to 1 acre of garden and lawn irrigation and watering for domestic animals is available based on our review of available information and research. Available water from the underground aquifer below the site that is adequate to supply typical demands and allow for peak storage replenishment requirements during low demand periods. In-house water demand and fire storage requirements can be met by the utilization of this single water well on site, having a sustainable production rate of 15 gpm. If you have any questions, comments or need additional information please call. Sincerely, SOPRIS ENGINEERING, LLC Paul E. Rutledge Desig• Engi y ichol, P.E. ncipal