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HomeMy WebLinkAboutRevised Stormwater Design Report Reduced - Part 1 - 08-05-2020 234 E Babcock Street, Suite 3  Bozeman, MT 59715  (406) 586-0277 DRAINAGE REPORT FOR ARROWLEAF PARK & PERENNIAL PARK Bozeman, Montana TD&H Engineering Project Number: B19-006 Prepared: July 24, 2020 TD&H ENGINEERING 234 E. Babcock Street, Suite 3 Bozeman, MT 59715 7/27/2020 TABLE OF CONTENTS Project Description 1 Geotechnical Information 1 Pre-Developed Basin Information 1 Post-Developed Basin Information 2 Methodology 4 Flood Hazard Evaluation 5 APPENDICES: A. Plans and Maps B. NRCS Soils Report C. Saccoccia Minor Subdivision – Basis of Design Report, dated January 2007 Bozeman Lowe’s Wetland Mitigation Plan, dated February 2006 D. Design Calculations E. Storm Water Management Plan F. Flood Analysis 1 PROJECT DESCRIPTION: The Arrowleaf Park & Perennial Park proposed project site is located within the Northwest ¼ of Section 1 of Township 2 South and Range 5 East P.M.M. The project located in Bozeman, Montana, is between Tschache Lane and East Baxter Lane and between Sacco Drive and Walton’s Stream/Ditch. The proposed site improvements cover the majority of the site with commercial buildings located on the south side of the property and apartment buildings scattered on the rest of the property. The proposed project also includes asphalt drives and parking lots, concrete sidewalks, utility services and landscaping. The existing drainage flows in a northerly direction and has relatively flat grades between 0% and 4%. Appendix A provides an existing site and drainage map. The site consists of approximately 12.5 acres of existing field with a sidewalk on the south side and a pedestrian trail on the east side of the property. GEOTECHNICAL INFORMATION: Soil information was obtained from the NRCS online soil survey. The soil onsite primarily consist of silt loam and sandy loam. The capacity to transmit water is considered moderately high. The frequency of ponding is considered to be none. Groundwater monitoring was performed onsite at 4 different monitoring locations onsite during the June of 2019. The depth of groundwater during that period of time ranged from approximately 3.6 to 5.0 feet deep. Groundwater shall also be measured this year in order to ensure that proposed retention ponds are located above ground water. Soil and ground water information has been included in appendix B. PRE-DEVELOPED BASIN INFORMATION: The site is relatively flat with sloping from the south to the north. Currently, any stormwater on the site generally flows to the north. Storm water from Tschache Lane also discharges to the site through an existing sidewalk chase on the south end of the development. Per the Saccoccia Minor Subdivision Basis of Design Report dated January 2007 all storm water currently drains to the existing storm water pond on the north side of the property which was designed to have 1 foot of constant ground water (which was originally used towards wetland mitigation requirements), and 1.5 feet of operating depth (i.e., capacity for stormwater detention). The composite C value calculated for this 36.8 acre subdivision was 0.76. The detention pond was surveyed as requested by the Bozeman Engineering Division. The actual, surveyed operating depth of the pond is less than designed, at 1.18 feet vs. 1.5 feet. 2 However, the actual total storage capacity is greater than designed, at 47,653 cubic feet vs. 44860 cubic feet. The groundwater that feeds the pond is kept at a constant level by the outlet at the east end of the pond. Therefore , the total depth of pond was not measured or included in the capacity. The actual capacity of the pond is measured from the top of groundwater to the overflow elevation. Table 1.1 shows the designed pond versus the actual surveyed stormwater pond. Table 1.1 Existing Storm Water Pond Designed Storm Pond Actual Storm Pond Operating Depth 1.5 ft 1.18 ft Operating Volume 44,860 CF 47,653 CF Invert Out Elev. 4,725.5 ft 4,725.43 ft Overflow Elev. 4,726.7 ft 4,726.61 ft Note: The actual pond area is larger than originally designed resulting in more storage capacity even though the actual depth is less than originally designed. The January 2007 basis of design report for the Saccoccia Minor Subdivision is included in Appendix C. POST-DEVELOPED BASIN INFORMATION: In order to meet City of Bozeman storm water requirements, the proposed storm water plan is to utilize the existing Lowe's PUD detention pond that was constructed to accommodate flow from the current development site. The Arrowleaf Park & Perennial Park project proposes to install three new retention ponds to capture the first 0.5 inch of storm water onsite. This is necessary because the existing detention pond was not designed to retain and dispose onsite the first 0.5 inch from a storm event. The proposed site development has been divided into 3 storm water basins. Basin 1 flows into Pond A by way of overland flow, catch basin and piping. Basin 2 functions the same way and flows into Pond B. Basin 3 flows into Pond C by means of overland flow and piping to collect the water received from Tschache Lane. Please see the Basin Map located in Appendix A for more information. Three retention ponds have been sized and are summarized in table 1.2 below. The ponds are sized to accommodate the first 0.5 inch rain event and treat onsite through gradual infiltration into the ground. Please see appendix D for calculations. 3 The soils onsite are highly permeable and will allow retained storm water to percolate into the ground. The ground water was monitored onsite in four different monitoring locations onsite during June of 2019. Table 1.3 shows the pond bottoms and ground water elevations as proposed. Table 1.3 Ground Water Elevations Monitoring Well No. Pond No. Pond Bottom Elev. (ft) Measured Ground Water Elev. (ft) 1 1 4,728.50 4,726.73 2 2 4,728.50 4,727.07 4 3 4,734.75 4,733.92 The combined C factor for proposed improvements is 0.66. This C factor is less than the average C factor determined in the Saccoccia Minor Subdivision Design Report for this development which was 0.76. There is an excess storage volume for this proposed project being approximately 2,793 cf (47653-44860). It should also be noted that 14,587 cf of storage volume has been added to the system, leaving a surplus of volume in the existing detention pond. Existing pond sizing verification calculations are located in appendix D. The collection system piping has been designed to handle the 25 year storm event. To be conservative, a runoff coefficient of 0.8 was used for the piping analysis. The gutter flow and inlet capacity was also analyzed to check that the collection system does meet and exceed the requirements of the 25 year storm. Please find calculations in appendix D. The 100 year storm water event shall travel via overland flow. In basins one and two, the 100 year flow shall travel from north to south through the parking area until it reaches the pond areas. Once in the ponds, all excess from the 100 year flow shall travel out of the overflows into the existing pond. Storm water from the 100 year storm in basin three shall travel east through the proposed parking lot and pour into proposed pond C. Storm water from the 100 year storm in basin four shall travel north along Sacco Drive until it reaches the ditch on the north side of the development. The 100 year flood will not reach the finished floor elevation on any of the buildings. For a map of the proposed 100 year storm water flow paths, see appendix A. Additionally, a storm water management plan has been prepared to educate the end user of on maintenance of the ponds. Table 1.2 Pond Volumes 1st 1/2 inch of storm water Basin Required Volume Provided Volume 1 3,202 4,382 2 6,059 6,296 3 2,532 3,909 Total Storage: 14,587 4 METHODOLOGY Storm water that will go to the existing onsite storm water pond shall first pass through basin ponds which are for the treatment of the first half inch of storm water from impervious surfaces. Volumes for treatment of Basins 1 and 2 shall be taken care of in this manner. VBasin# = Aimpervious * (½”/ 12) VBasin1 = 76,841 sf * (½”/ 12) VBasin1 = 3,202 cf of storage required VBasin2 = 145,594 sf * (½”/ 12) VBasin2 = 6,067 cf of storage required Ponds 1 and 2 are providing 4,382 cubic feet and 6,296 cubic feet of storage respectively. Basin 3 storm water, which will not pass through the existing onsite storm water pond, will go into a proposed retention pond on the east side of the basin. Retention volume calculations are used as per the City of Bozeman Design Standards. V = 7200*Q and Q = CIA Where: C = 0.65 as calculated in table listed in Appendix D I = 0.41 in/hr (10 year 2 hr storm) A = 60,758 / 43,560 = 1.40 Acres Q = 0.65 * 0.41 * 1.40 = 0.3731 cf V = 7200 * 0.3731 = 2,687 cf of storage required Pond 3 is providing 3,909 cubic feet of storage. The proposed retention ponds created onsite shall be 1.5 feet deep with 0.5 feet of freeboard. More calculations are located in Appendix D. 5 FLOOD HAZARD EVALUATION This project site lies adjacent to the Farmers Canal return flow watercourse and is also in proximity to Mandeville Creek which is located approximately 1,200-feet to the east of the property. A flood hazard evaluation study for this area was recently completed by KLJ Engineering for a proposed neighboring development (PT Land Phase 3 Subdivision) that estimated 100-yr flows and flood elevations for these two drainages and delineated the resulting inundation areas based on existing condition surface elevations. In correspondence with the KLJ project representative, it was reiterated that the purpose of the study was not to undertake a refined flood mapping effort for the property, but rather to analyze the unlikely worst-case scenario where the existing storm drain network is able to deliver the entire 100-yr flow from each drainage basin to the site simultaneously. Under such conditions, it was demonstrated that all flows not able to pass through the existing Baxter Lane / I-90 culverts to the north will overtop Baxter Lane and exit the site at the sag curve near the Sacco Drive intersection. The resulting calculated overtopping elevation was then used to determine the backwater inundation areas at the north end of the site, and 100-yr flow depths were calculated for several channel cross sections along each watercourse flowing into the site from the south. Upon review of the KLJ report, and because the existing conditions have not changed significantly for the site or contributing drainage basins since the study, we are comfortable accepting KLJ’s methods and findings to estimate conservative 100-yr flood elevations and inundation areas as they pertain to improvements proposed with this development. Exhibits 1 and 2 are attached in appendix F showing the proposed Arrowleaf Park and Perennial Park development overlaid on the KLJ estimated 100-yr inundation areas. Finish Floor elevations for each of the proposed buildings are also provided for comparison with the calculated 100-yr flood evaluations at the north end of the site and at cross sections along the adjacent incoming channel. As demonstrated by the exhibit, all proposed buildings are outside of the inundation areas, and all building floor elevations are proposed 1.5-feet or more above their adjacent calculated flood elevations. It should also be noted that no improvements are proposed with the development that would encroach or otherwise reduce existing flood conveyance or storage capacity in this part of the system. Additionally, the proposed buildings are to be elevated above interior parking lots and drive aisles with positive drainage intended to direct interior site run-off away from buildings and to the designated stormwater collection system and designed overflow routes. Therefore, it is reasonable to assume the proposed development will be safe from flooding as designed. In the event North 15th Avenue gets extended to Baxter Lane, the flood hazard on the Arrowleaf Park and Perennial Park site is not expected to increase. The 100-yr flow from the Farmers Canal drainage basin will continue to be conveyed on the west side of 15th next to the site as currently modeled, and contributing flows from the Mandeville Creek basin will either be entirely conveyed beneath 15th by design, or will more likely be impounded to some extent on the east side of the new roadway thereby lessening flood elevations on the north end of this site. APPENDIX A Plans and Maps 30'-0"20'-0"FF=4736.00FF=4735.00FF=4734.75FF=4734.50FF=4735.25FF=4735.75FF=4735.25FF=4734.75FF=4734.50FF=4736.00TSCHACHE LANE85FAMILY PROMISEFF=4739.00COMMUNITY HEALTHPARTNERSFF=4740.00SHEETDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:ARROWLEAF PARK AND PERENNIAL PARK BOZEMAN, MONTANA B19-006XX7/24/20REV DATE REVISION Engineering 234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715 406.586.0277 • tdhengineering.com POND APOND BOTTOMELEV= 4728.50VOL.@1.5'=4382 CFPOND BOTTOMAREA=1985 SFB19-006-BASIN MAP-20200722BASIN MAP .DWG1KJMKJMHSEPOND BPOND BOTTOMELEV= 4728.50VOL.@1.5'=6298 CFPOND BOTTOMAREA=3186 SFBASIN 2APVMT AREA= 17,128 SFWALK AREA= 4144 SFROOF AREA= 10,377 SFNPGIS AREA=10,957 SFTOTAL AREA= 42,606 SFTc=175 LFBASIN 3APVMT AREA= 28,735 SFWALK AREA= 7495 SFROOF AREA= 11,587 SFNPGIS AREA= 23,924 SFTOTAL AREA= 71,741 SFTc=350 LFBASIN 2CPVMT AREA= 9466 SFWALK AREA= 1157 SFROOF AREA= 4120 SFNPGIS AREA= 6556 SFTOTAL AREA= 21,299 SFTc=140 LFBASIN 1APVMT AREA= 2648 SFWALK AREA= 766 SFROOF AREA= 0 SFNPGIS AREA= 979 SFTOTAL AREA= 4393 SFTc=70 LFBASIN 2EPVMT AREA= 5207 SFWALK AREA= 1975 SFROOF AREA= 1931 SFNPGIS AREA= 7045 SFTOTAL AREA= 16,158 SFTc=100 LFBASIN 1BPVMT AREA= 5491 SFWALK AREA= 3106 SFROOF AREA= 8808 SFNPGIS AREA= 2765 SFTOTAL AREA= 20,170 SFTc=115 LFBASIN 1CPVMT AREA= 10,540 SFWALK AREA= 3574 SFROOF AREA= 9809 SFNPGIS AREA= 6043 SFTOTAL AREA= 29,966 SFTc=190 LFBASIN 2FPVMT AREA= 16,881 SFWALK AREA= 4520 SFROOF AREA= 14,847 SFNPGIS AREA= 19,044 SFTOTAL AREA= 55,292 SFTc=195 LFBASIN 2BPVMT AREA= 9909 SFWALK AREA=904 SFROOF AREA= 2943 SFNPGIS AREA= 3930 SFTOTAL AREA= 17,686 SFTc=130 LFBASIN 2DPVMT AREA= 8258 SFWALK AREA= 3431 SFROOF AREA= 12,756 SFNPGIS AREA= 13,120 SFTOTAL AREA= 37,565 SFTc=160 LFBASIN 2GPVMT AREA= 8949 SFWALK AREA= 1504 SFROOF AREA= 5187 SFNPGIS AREA= 6051 SFTOTAL AREA= 21,691 SFTc=155 LFBASIN 1EPVMT AREA= 7876 SFWALK AREA= 1814 SFROOF AREA= 5187 SFNPGIS AREA= 7588 SFTOTAL AREA= 22,465 SFTc=200 LFBASIN 1DPVMT AREA= 8223 SFWALK AREA= 2817 SFROOF AREA= 6182 SFNPGIS AREA= 6855 SFTOTAL AREA= 24,077 SFTc=140 LFPOND CPOND BOTTOMELEV= 4734.75VOL.@1.5'=5102 CFPOND BOTTOMAREA=2246 SFGROUNDWATERELEVATION MW #1=4724.95GROUNDWATERELEVATION AT MW #2=4725.13GROUNDWATERELEVATION AT MW #4=4731.75GROUNDWATERELEVATION AT MW #3=4727.25BASIN 3BPVMT AREA= 10,308 SFWALK AREA= 2633 SFROOF AREA= 0 SFNPGIS AREA= 3037 SFTOTAL AREA= 15,978 SFTc=280 LFEXISTING POND STORMWATER CAPACITY ±47,653 CFAVAILABLE OPERATING CAPACITY DEPTH=1.18'BASIN 4PVMT AREA= 0 SFWALK AREA= 4765 SFROOF AREA= 36,012 SFNPGIS AREA= 9902 SFTOTAL AREA= 50,679 SFTc=465 LF See Plan set dated May 4, 2020 for Arrowleaf Park and Perennial Park 30'-0"20'-0"FF=4736.00FF=4735.00FF=4734.75FF=4734.50FF=4735.25FF=4735.75FF=4735.25FF=4734.75FF=4734.50FF=4736.00TSCHACHE LANE85FAMILY PROMISEFF=4739.00COMMUNITY HEALTHPARTNERSFF=4740.00SHEETDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:ARROWLEAF PARK AND PERENNIAL PARK BOZEMAN, MONTANA B19-006XX5/05/20REV DATE REVISION Engineering 234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715 406.586.0277 • tdhengineering.com POND APOND BOTTOMELEV= 4728.50VOL.@1.5'=4382 CFPOND BOTTOMAREA=1985 SFB19-006-BASIN MAP-20200501100 YEAR STORM WATER FLOW PATH MAP .DWG1KJMKJMHSEPOND BPOND BOTTOMELEV= 4728.50VOL.@1.5'=6298 CFPOND BOTTOMAREA=3186 SFPOND CPOND BOTTOMELEV= 4734.75VOL.@1.5'=5102 CFPOND BOTTOMAREA=2246 SFGROUNDWATERELEVATION MW #1=4724.95GROUNDWATERELEVATION AT MW #2=4725.13GROUNDWATERELEVATION AT MW #4=4731.75GROUNDWATERELEVATION AT MW #3=4727.25 APPENDIX B GROUNDWATER MONITORING & NRCS SOILS REPORT REVISIONSHEETDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:19006T2-1REV DATE ARROWLEAF PARK & PERENNIAL PARK - TOPOGRAPHIC SURVEY BOZEMAN, MONTANA LOT 3A OF MINOR SUB 407A & SACCOCIA COMMON OPEN SPACE OF MINOR SUB 407 IN THE NW 1/4 OF SEC 1, T2S, R5E, P.M.M., GALLATIN COUNTY B19-0067/31/19194/20, 27.DWG2/2SCA406.586.0277 • tdhengineering.com Engineering 234 E. BABCOCK ST., SUITE 3 • BOZEMAN, MONTANA 59715 HGW = 4726.73 ARROWLEAF PARK & PERENNIAL PARK Groundwater Monitoring Date Water Level (ft)GW Elev Ht Change DEPTH BG DEPTH BG 5.00 4726.10 2019 4/14/20 6/3/2019 4.38 4726.73 0.63 2.47 3.3 6/11/2019 4.70 4726.40 -0.32 2.80 6/17/2019 4.75 4726.35 -0.05 2.85 6/24/2019 4.67 4726.43 0.08 2.77 7/1/2019 4.88 4726.22 -0.21 2.98 Date Water Level (ft)GW Elev Ht Change DEPTH BG DEPTH BG 4.67 4726.23 2019 4/14/20 6/3/2019 4.08 4726.82 0.59 1.98 6/11/2019 4.13 4726.77 -0.05 2.03 6/17/2019 4.00 4726.90 0.13 1.90 6/24/2019 3.83 4727.07 0.17 1.73 2.1 7/1/2019 4.25 4726.65 -0.42 2.15 Date Water Level (ft)GW Elev Ht Change DEPTH BG DEPTH BG 4.75 4728.15 2019 4/14/20 6/3/2019 4.04 4728.86 0.71 2.04 6/11/2019 4.00 4728.90 0.04 2.00 6/17/2019 3.83 4729.07 0.17 1.83 6/24/2019 3.63 4729.27 0.20 1.63 1.8 7/1/2019 4.00 4728.90 -0.37 2.00 Date Water Level (ft)GW Elev Ht Change DEPTH BG DEPTH BG 5.42 4733.08 2019 4/14/20 6/3/2019 4.94 4733.56 0.48 2.84 6/11/2019 5.00 4733.50 -0.06 2.90 6/17/2019 4.67 4733.83 0.33 2.57 6/24/2019 4.58 4733.92 0.09 2.48 3.2 7/1/2019 4.88 4733.62 -0.30 2.78 Monitoring Well #1 Monitoring Well #2 Monitoring Well #3 Monitoring Well #4 Notes Notes Notes Brief storm yesterday with heavy precipitation. Notes Brief storm yesterday with heavy precipitation. Brief storm yesterday with heavy precipitation. Brief storm yesterday with heavy precipitation. United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Gallatin County Area, MontanaNatural Resources Conservation Service April 7, 2020 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................8 Soil Map................................................................................................................9 Legend................................................................................................................10 Map Unit Legend................................................................................................11 Map Unit Descriptions.........................................................................................11 Gallatin County Area, Montana.......................................................................13 50B—Blackdog silt loam, 0 to 4 percent slopes..........................................13 506A—Saypo silt loam, 0 to 2 percent slopes.............................................14 509B—Enbar loam, 0 to 4 percent slopes...................................................15 542A—Blossberg loam, 0 to 2 percent slopes............................................17 References............................................................................................................19 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and Custom Soil Resource Report 6 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 9 Custom Soil Resource Report Soil Map 5060330506039050604505060510506057050606305060690506075050603305060390506045050605105060570506063050606905060750495370 495430 495490 495550 495610 495670 495370 495430 495490 495550 495610 495670 45° 42' 2'' N 111° 3' 35'' W45° 42' 2'' N111° 3' 19'' W45° 41' 46'' N 111° 3' 35'' W45° 41' 46'' N 111° 3' 19'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84 0 100 200 400 600 Feet 0 30 60 120 180 Meters Map Scale: 1:2,330 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Gallatin County Area, Montana Survey Area Data: Version 23, Sep 16, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 3, 2009—Sep 1, 2016 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Custom Soil Resource Report 10 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 50B Blackdog silt loam, 0 to 4 percent slopes 1.6 7.8% 506A Saypo silt loam, 0 to 2 percent slopes 6.8 34.0% 509B Enbar loam, 0 to 4 percent slopes 11.6 57.6% 542A Blossberg loam, 0 to 2 percent slopes 0.1 0.6% Totals for Area of Interest 20.1 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. Custom Soil Resource Report 11 The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 12 Gallatin County Area, Montana 50B—Blackdog silt loam, 0 to 4 percent slopes Map Unit Setting National map unit symbol: 56vq Elevation: 4,350 to 5,500 feet Mean annual precipitation: 15 to 19 inches Mean annual air temperature: 37 to 43 degrees F Frost-free period: 90 to 110 days Farmland classification: All areas are prime farmland Map Unit Composition Blackdog and similar soils: 90 percent Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Blackdog Setting Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Parent material: Calcareous loess Typical profile A - 0 to 10 inches: silt loam Bt - 10 to 19 inches: silty clay loam Bk - 19 to 60 inches: silt loam Properties and qualities Slope: 0 to 4 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high (0.20 to 0.57 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 30 percent Available water storage in profile: High (about 10.9 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: C Ecological site: Silty (Si) 15-19" p.z. (R044XS355MT), Upland Grassland (R044BP818MT) Hydric soil rating: No Minor Components Meagher Percent of map unit: 4 percent Landform: Alluvial fans, stream terraces Down-slope shape: Linear Custom Soil Resource Report 13 Across-slope shape: Linear Ecological site: Silty (Si) 15-19" p.z. (R044XS355MT) Hydric soil rating: No Bowery Percent of map unit: 3 percent Landform: Stream terraces, alluvial fans Down-slope shape: Linear Across-slope shape: Linear Ecological site: Silty (Si) 15-19" p.z. (R044XS355MT) Hydric soil rating: No Quagle Percent of map unit: 3 percent Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Limy (Ly) 15-19" p.z. (R044XS357MT) Hydric soil rating: No 506A—Saypo silt loam, 0 to 2 percent slopes Map Unit Setting National map unit symbol: 56vl Elevation: 4,050 to 5,100 feet Mean annual precipitation: 12 to 18 inches Mean annual air temperature: 37 to 45 degrees F Frost-free period: 90 to 110 days Farmland classification: Farmland of local importance Map Unit Composition Saypo and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Saypo Setting Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Parent material: Loamy alluvium Typical profile A - 0 to 10 inches: silt loam Bk - 10 to 21 inches: silt loam Bkg - 21 to 60 inches: silt loam Properties and qualities Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Custom Soil Resource Report 14 Natural drainage class: Somewhat poorly drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high (0.20 to 0.57 in/hr) Depth to water table: About 24 to 42 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 40 percent Salinity, maximum in profile: Very slightly saline to moderately saline (2.0 to 8.0 mmhos/cm) Sodium adsorption ratio, maximum in profile: 5.0 Available water storage in profile: Moderate (about 7.7 inches) Interpretive groups Land capability classification (irrigated): 4w Land capability classification (nonirrigated): 6w Hydrologic Soil Group: C Ecological site: Saline Subirrigated (SSb) 9-14" p.z. (R044XS333MT), Subirrigated Grassland (R044BP815MT) Hydric soil rating: No Minor Components Newtman Percent of map unit: 5 percent Landform: Terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Wet Meadow (WM) 9-14" p.z. (R044XS349MT) Hydric soil rating: Yes Tetonview Percent of map unit: 5 percent Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Wet Meadow (WM) 9-14" p.z. (R044XS349MT) Hydric soil rating: Yes Reycreek Percent of map unit: 5 percent Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Saline Subirrigated (SSb) 9-14" p.z. (R044XS333MT) Hydric soil rating: No 509B—Enbar loam, 0 to 4 percent slopes Map Unit Setting National map unit symbol: 56vp Elevation: 4,400 to 6,000 feet Custom Soil Resource Report 15 Mean annual precipitation: 15 to 19 inches Mean annual air temperature: 37 to 45 degrees F Frost-free period: 90 to 110 days Farmland classification: All areas are prime farmland Map Unit Composition Enbar and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Enbar Setting Landform: Flood plains Down-slope shape: Linear Across-slope shape: Linear Parent material: Loamy alluvium Typical profile A - 0 to 22 inches: loam Cg - 22 to 49 inches: sandy loam 2C - 49 to 60 inches: very gravelly loamy sand Properties and qualities Slope: 0 to 4 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat poorly drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1.98 in/hr) Depth to water table: About 24 to 42 inches Frequency of flooding: Rare Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Moderate (about 8.8 inches) Interpretive groups Land capability classification (irrigated): 3w Land capability classification (nonirrigated): 3w Hydrologic Soil Group: C Ecological site: Subirrigated (Sb) 15-19" p.z. (R044XS359MT), Bottomland (R044BP801MT) Hydric soil rating: No Minor Components Nythar Percent of map unit: 10 percent Landform: Flood plains Down-slope shape: Linear Across-slope shape: Linear Ecological site: Wet Meadow (WM) 15-19" p.z. (R044XS365MT) Hydric soil rating: Yes Straw Percent of map unit: 5 percent Custom Soil Resource Report 16 Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Silty (Si) 15-19" p.z. (R044XS355MT) Hydric soil rating: No 542A—Blossberg loam, 0 to 2 percent slopes Map Unit Setting National map unit symbol: 56wx Elevation: 4,200 to 5,550 feet Mean annual precipitation: 12 to 18 inches Mean annual air temperature: 39 to 45 degrees F Frost-free period: 90 to 110 days Farmland classification: Farmland of local importance Map Unit Composition Blossberg and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Blossberg Setting Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium Typical profile A - 0 to 15 inches: loam Bg - 15 to 24 inches: sandy clay loam 2C - 24 to 60 inches: extremely gravelly loamy coarse sand Properties and qualities Slope: 0 to 2 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Poorly drained Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 1.98 in/hr) Depth to water table: About 12 to 24 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline to slightly saline (0.0 to 4.0 mmhos/cm) Available water storage in profile: Low (about 5.5 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 5w Hydrologic Soil Group: B/D Custom Soil Resource Report 17 Ecological site: Wet Meadow (WM) 15-19" p.z. (R044XS365MT), Subirrigated Grassland (R044BP815MT) Hydric soil rating: Yes Minor Components Bonebasin Percent of map unit: 10 percent Landform: Terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Wet Meadow (WM) 15-19" p.z. (R044XS365MT) Hydric soil rating: Yes Meadowcreek Percent of map unit: 5 percent Landform: Stream terraces Down-slope shape: Linear Across-slope shape: Linear Ecological site: Subirrigated (Sb) 15-19" p.z. (R044XS359MT) Hydric soil rating: No Custom Soil Resource Report 18 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 19 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 20 APPENDIX C SACCOCCIA MINOR SUBDIVISION BASIS OF DESIGN REPORT – JANUARY 2007 & BOZEMAN LOWE’S WETLAND MITIGATION PLAN FEBRUARY 2006