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HomeMy WebLinkAbout12-26 Engineering ReportENGINEERING REPORT SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 1)NARRATIVE AND CHANNEL & FLOOD PROTECTION 2)VRRM SPREADSHEET SUMMARY 3)TR-55 SCS METHOD WORKSHEETS 4)HYDROLOGIC MODELING AND CALCULATIONS 5)STORM SEWER & CHANNEL CALCULATIONS 6)E&SC AND MISCELLANEOUS CALCULATIONS 7)NRCS SOILS REPORT Dennie D. Dunlap III, P.E. Principal Engineer 03-05-2026 NARRATIVE AND CHANNEL & FLOOD PROTECTION SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 EROSION & SEDIMENT CONTROL NARRATIVE Project Description This narrative describes the erosion and sediment control plan for a proposed flex-space industrial storage project on a 5.48-acre parcel (TM 63-A-60B) located on Shady Elm Road in Frederick County, Virginia. The proposed development will include the construction of four 11,925 sq. ft. buildings with a new entrance and driveway, vehicle parking, overhead doors for interior access, sidewalks, and landscaping improvements. Access will be directly from Shady Elm Road with a new commercial entrance. There is a single stormwater management basin proposed to handle the runoff from the proposed development. The total estimated disturbed area is 5.36 acres, including a total of 3.41 acres of new impervious surface. The project is expected to commence in 2026. Site Conditions Vegetative Cover - The area to be disturbed is comprised of a mixture of range grass with pockets of trees. Prior to design, a portion of the existing site was cleared for the appropriate site investigation. The limits of disturbance shall be flagged/staked for any necessary clearing and to signify areas to be preserved. Topography – The existing topography rolls generally in the easterly direction across the site, and the western property line is situated along Shady Elm Road which is the high point of the site. The slopes are variable within the limits of disturbance and generally average approximately 5%. Drainage Patterns – The site drains from west to east across the site, where it then turns south along the eastern property line, mainly due to grading on the adjoining property to the east. Runoff then flows off- site at the southeast property corner, and flows overland until it is collected in the existing drainage system along Industrial Drive and Development Lane. It is then conveyed via an unnamed tributary until its convergence with Opequon Creek, approximately 7500’ southeast of the subject site. The drainage patterns exiting the site after development will be consistent with those in the pre-developed condition. A new stormwater management basin will be constructed near the eastern property boundary of the site in order to control the runoff from the new building and pavement areas. This basin will control and discharge the post-developed runoff into the existing drainage swale that flows off the site in the easterly direction. Soil Types – The soil types for the site were obtained from NRCS (see site plan sheet C-03). The site contains the following soil types: SOILS TABLE Symbol Name Erosion Potential Permeability Depth to Bedrock Hydrologic Soil Group 5B Carbo silt loam, 2-7% slopes High Very low to mod. low 20-40 in. D 6C Carbo-Oaklet, very rocky silt loam, 2-15% slopes High Very low to mod. high 20-40 in. C/D Adjacent Areas The adjacent properties consist of existing commercial/industrial uses. Since there are no structures immediately downstream from the site and all stormwater discharges from the site are controlled and directed to existing channels, there is little risk of damage to adjoining properties due to erosion. Off-site Areas Land disturbance will be confined to the subject property, therefore no disturbance to any off-site areas is anticipated. If any off-site disturbance is required during construction, those areas will be permitted accordingly. Geology There are no visible karst features located on the site. If any are encountered during construction activities, a geotechnical engineer will be consulted to ensure the necessary precautions are made and those areas are properly remediated. Critical Areas The areas over 15% slopes within the area of construction are controlled by perimeter erosion and sediment control measures. There are no wetlands or floodplain extents on the property. Any areas deemed by the Frederick County Erosion and Sediment Control Administrator as a potential serious erosion hazard shall be identified on the plan. Erosion and Sediment Control Measures Unless otherwise noted, the structural and vegetative practices shall be constructed and maintained according to the Minimum Standards of the Virginia Erosion and Sediment Control Law, Regulations and Certification Regulations and Specifications outlined in the latest edition of the Virginia Stormwater Management Handbook. The following summary(s) are for quick reference only and do not preclude any requirements or standards listed in the Virginia Stormwater Management Handbook. Also, other measures not specifically listed here or on the construction plans may be required to keep the site within regulatory compliance during construction. The need for such items may not be evident until the beginning of construction. The Warren County Erosion and Sediment Control Administrator will determine the need for additional erosion and sediment control measures. CONSTRUCTION BMPs 1. Temporary Diversion Dike (C-ECM-04) A temporary diversion dike is a temporary ridge of compacted soil constructed to convey clean stormwater runoff through or around a disturbed land area. In most cases, temporary diversion dikes collecting sediment-laden water work as conveyance in conjunction with other erosion and sediment control devices. A temporary diversion dike is used to protect work areas from upslope runoff and to divert sediment-laden water to appropriate traps or stable outlets. Inspect temporary diversion dikes after every storm and repair the dike, flow channel, outlet, or sediment trapping facility as necessary. In karst areas, the upslope edge of the diversion dike should be inspected for subsidence, especially at the downstream end and at the associated outlet structure/BMP. Subsidence is considered a mode of failure. Bi-weekly (whether a storm event has occurred or not), inspect the control measure and repair if needed. Repair damage caused by construction traffic or other activity before the end of each working day. Construct temporary diversions to operate with 6 inches or more of freeboard. Make height adjustments if frequent instances of overtopping are observed. 2. Outlet Protection (C-ESM-15) All storm pipe outlets shall be protected with a stone apron per specifications outlined in the latest edition of the Virginia Stormwater Management Handbook. When installed properly, outlet protection should require very little maintenance. However, it shall be inspected periodically for scour from high flows. Care must be taken to properly control sediment-laden construction runoff draining to the outlet protection until all up-gradient areas have been fully stabilized. 3. Silt Fence (C-PCM-04) Silt fence barriers shall be installed at locations shown on the Erosion and Sediment Control Plan. Silt fence intercepts and detains small amounts of sediment from disturbed ground areas during construction to prevent sediment from leaving the site. Silt fence decreases the water velocity of sheet flow and low-level channel flows to moderate-level channel flows. Inspect silt fences immediately after each rainfall and at least daily during prolonged rainfall. Make any repairs immediately. Pay close attention to the repair of damaged silt fence resulting from end runs and undercutting. This is commonly a sign the fence has either been improperly installed or is placed in a less than optimal location. If the fence cannot be relocated, then more frequent inspections will be warranted. Replace the fabric promptly if the fabric on a silt fence decomposes or becomes ineffective before the end of the expected usable life and the barrier is still necessary. Remove trash, floatables, and large sediment deposits after each storm event and when deposits reach approximately one half the height of the barrier. Dress to conform to existing grade, prepare, and seed any sediment deposits remaining in place after the silt fence is no longer required. 4. Dust Control (C-SCM-01) Dust control is used to prevent surface and air movement of dust from exposed soil surfaces and reduce the presence of airborne substances that may pose health hazards, traffic safety problems, or harm animal or plant life. Dust control applies to areas subject to dust on the ground surface and in the air where on-site and off-site damage is likely to occur if preventive measures are not taken. Maintain dust control measures through dry weather until all disturbed areas have been stabilized. Because the success of dust controls depends on specific site and weather conditions, inspection and maintenance requirements are unique for each site. However, dust control measures involving application of either water or chemicals require more monitoring than structural or vegetative controls to remain effective. Inspect structural controls for deterioration regularly to ensure the controls are still achieving its intended purpose. 5. Temporary Stone Construction Entrance (C-SCM-03) Construction entrances provide an opportunity for significant removal of mud from construction vehicle tires before they enter a public road, and, just as important, the soil adjacent to the paved surface can be kept intact. Temporary stone construction entrances reduce the tracking of mud onto paved public roads by motor vehicles or runoff and provide a stable entry to or exit from the construction site. This practice applies where traffic leaves a construction site and moves directly onto a public road or other paved area. Inspect the construction entrance weekly and immediately after each rainfall. Maintain the entrance to prevent tracking or flow of dirt, mud, or sediment onto public rights-of-way, including periodic top dressing with additional stone and repair or cleanout of structures that trap sediment or both. Maintain a stockpile of rock at the site for top dressing purposes. Mud and soil particles will eventually clog the voids in the stone and compromise the effectiveness of the construction entrance. When this occurs, top dress the pad with new stone. Complete stone replacement is necessary when the pad becomes wholly clogged with sediment and the topdressing is no longer effective at removing accumulated sediment from tires. Immediately remove all materials spilled, dropped, washed, or tracked from vehicles onto roadways or storm drains. Do not use water trucks to remove materials dropped, washed, or tracked onto roadways under any circumstances. Immediately remove stones from the adjoining roadway that construction traffic dislodged from the entrance. Maintain the area under the wash rack free of accumulated sediment. Repair or replace the wash rack if it becomes damaged. 6. Inlet Protection (C-SCM-04) The purpose of inlet protection is to prevent sediment from entering storm drainage systems before permanent stabilization of the disturbed area. Every storm drain inlet, catch basin, curb inlet, or similar drainage structure receiving sediment-laden runoff should be protected by a combination of upstream erosion control and temporary inlet protection. This practice will significantly reduce sediment loads and will help prevent floatable waste materials and other construction wastes from entering stormwater systems . Routine inspection and maintenance are critical to ensuring the adequate performance of inlet protection. Include the following activities as part of any maintenance program: • Inspect all inlet protection devices at least twice weekly (72 hours or more between each inspection) and after every significant rainfall event (0.25 inch or more). • During extended rainfall events, inspect inlet protection devices at least once every 24 hours. • Replace clogged aggregate or filter fabric immediately. • Look for damage or tears to fabric caused by large flows. • Inspect downstream inlets, pipes, and other infrastructure after severe storms to check for bypassed material. • Remove sediment from temporary inlet protection methods when sediment reaches depths of 2 or 3 inches. More frequent sediment removal is required from paved areas such as streets or parking lots. • Remove all inlet protection devices within 30 days after the site is stabilized, or when the inlet protection is no longer needed. • Bring the disturbed area to final grade and appropriately stabilize all bare areas around the inlet with vegetation. • Clean storm drainage system of sediment and debris before final inspection. • In karst areas, inspect excavated drop inlet sediment traps regularly and after each precipitation event for subsidence. Subsidence is a criterion of failure. As such, mitigate subsidence immediately using the appropriate engineering practice. 7. Culvert Inlet Protection (C-SCM-05) Culvert inlet protection prevents sediment from entering, accumulating in, and being transported by a culvert and associated drainage system before the permanent stabilization of a disturbed project area. Culvert inlet protection also controls erosion at culvert inlets during the phase of a project in which elevation and drainage patterns change, causing original control measures to be ineffective or in need of removal. Use culvert inlet protection where a culvert is to be made operational before permanent stabilization of the disturbed drainage area or to control erosion/remove sediment from water before flowing into an existing culvert. Inspect the structure after each rain event and make repairs as needed. Replace or clean aggregate when inspection reveals that clogged voids are causing ponding problems that interfere with on-site construction. Remove sediment and restore the impoundment to its original dimensions when sediment has accumulated to one half the design depth. The deposit removed sediment in a suitable area so that it would not erode and cause further sedimentation problems. In karst areas, sinkholes may form in the vicinity of inlet protection and capture site runoff into groundwater. Inspect inlets for subsidence features and repair any subsidence features identified using the appropriate sinkhole repair BMP. Remove temporary structures when they have served their useful purpose, but not before the upslope area has been permanently stabilized. 8. Temporary Sediment Basin (C-SCM-12) A temporary sediment basin is used to detain sediment-laden runoff from disturbed areas in “wet” and “dry” storage long enough for much of the sediment to settle out. These structures are limited to a useful life of 18 months unless the basins are designed as permanent impoundments. Inspect the basin embankment regularly to ensure that it is structurally sound and has not been damaged by erosion or construction equipment. Inspect the emergency spillway regularly to ensure that its lining is well established and erosion-resistant. After every runoff producing rainfall, inspect the principal spillway and dewatering orifice for clogging and remove accumulated debris to maintain free flow from the basin. Inspect the vegetative stabilization, soil stabilization matting, slope drains and baffles if present, and maintain or repair immediately. Inspect the basin after each runoff-producing rainfall for sediment cleanout. When the sediment reaches the cleanout level, remove and properly dispose of the sediment. Inspect the basin for sinkhole formation, and if found, repair promptly. 9. Topsoiling (C-SSM-02) Topsoiling provides a suitable growth medium for final site-stabilizing vegetation. Topsoiling applies where the preservation or importation of topsoil is determined to be the most effective method of providing a suitable growth medium, high-quality turf is desirable to withstand intense use or meet aesthetic requirements, permanent vegetation will be established, and slopes are 2H:1V or flatter unless other measures are taken to prevent erosion and sloughing. Slopes and areas that will not be mowed may be left rough after spreading topsoil. A disc may be used to promote bonding at the interface between topsoil and subsoil. After topsoil application, follow procedures for seedbed preparation, taking care to avoid excessive mixing of topsoil into the subsoil. Apply stabilization to areas that remain dormant for 7 days after topsoil has been spread. 10. Surface Roughening (C-SSM-03) Surface roughening is the practice of providing a rough soil surface with horizontal depressions to reduce runoff velocity, increase infiltration, aid the establishment of vegetation, and reduce erosion. Periodically check the seeded slopes for rills and washes. Fill these areas slightly above the original grade, then reseed and mulch as soon as possible. Seeded slopes should be inspected after every recordable rain event. Seed should be reapplied in areas where it may have washed away during the previous rain event. 11. Temporary Seeding (C-SSM-09) Temporary seeding is the establishment of a temporary vegetative cover on disturbed areas by seeding with appropriate rapidly growing annual plants. This can be used to reduce erosion and sedimentation by stabilizing disturbed areas that will not be brought to final grade for a period of more than 14 days, reduce damage from sediment and runoff to downstream or offsite areas, and to protect bare soils exposed during construction until permanent vegetation or other erosion control measures can be established. This applies where exposed soil surfaces are not to be fine-graded for periods longer than 14 days. Such areas include bare areas, soil stockpiles, dikes, dams, sides of sediment basins, temporary road banks, non-vegetated cuts and fills, and diversions (see MS #1 and MS #2). Apply a permanent vegetative cover to areas that will be left dormant for a period of more than 1 year. 12. Permanent Seeding (C-SSM-10) Permanent seeding is the establishment of perennial vegetative cover on disturbed areas by planting seed. Permanent seeding applies in disturbed areas where permanent, long-lived vegetative cover is needed to stabilize the soil; and rough-graded areas that will not be brought to final grade for 1 year or more. MANAGEMENT STRATEGIES The following guidelines shall be utilized in the planning of construction: 1) The silt fence, construction entrance, and other measures intended to remove sediment shall be constructed as a first step in the land disturbing activity and shall be functional before up slope land is disturbed. These measures shall also be stabilized with vegetation prior to up slope land disturbance. 2) The contractor shall install inlet protection and outlet protection for all storm utilities immediately after installation of said structures to prevent sediment from collecting in the said structures and being deposited down stream. Rock check dams if used shall be constructed during this step. 3) Construction shall be sequenced so that grading operations can begin and end as quickly as possible. 4) Temporary seeding and other stabilization shall follow immediately after the site is stripped of topsoil if it is determined that final grading will not begin within 7 days. 5) The developer shall be responsible for the installation and maintenance of all Erosion and Sediment Control practices. 6) The topsoil stockpile location shall be immediately protected by silt fence on the down slope side. NOTE: The contractor shall ensure that at the end of each working day all erosion and sediment control measures are in place and functioning properly. This will be strictly enforced. Permanent Stabilization Permanent stabilization shall be applied to denuded areas immediately after final grade is achieved on any portion of the site. Temporary soil stabilization shall be applied within seven (7) days to denuded areas that may not be at final grade but will remain undisturbed for more than 14 days. Permanent stabilization shall be applied to areas left dormant for more than one year. Seeding shall be conducted in accordance with the latest edition of the Virginia Stormwater Handbook. Permanently seeded areas shall be protected during establishment with straw mulch. Hydro-seeding also requires straw mulch protection. Maintenance In general, all erosion and sediment control measures shall be inspected every 5 business days and within 24 hours of a measureable storm event or every 4 business days. A measurable storm event is considered 0.25 inches of rainfall over a 24-hour period. The following items shall be checked in particular: 1. The silt fence, inlet and outlet protection areas, and temporary construction entrance shall be checked for undermining, stability, deterioration, and functionality. 2. All seeded areas shall be checked for adequate growth. If adequate growth is not evident, the area shall be re-seeded to prevent the soils from eroding. 3. All temporary erosion and sediment control measures shall be removed only when all contributing drainage areas are fully stabilized and when authorized by the Frederick County Erosion and Sediment Control Administrator. 4. Trapped sediment and the disturbed soil areas resulting from the removal of the temporary measures shall be permanently stabilized to prevent further erosion and sedimentation. 5. Long term maintenance of all storm water associated items is the sole responsibility of the owner. A long-term Stormwater Management Facility Maintenance Agreement with Frederick County is required for the stormwater management basin. All erosion and sediment controls needing remediation shall be repaired immediately upon the discovery of damage or lack of functionality to ensure the proper functioning of the control(s). Construction Sequence 1. Contractor shall schedule and hold an on-site preconstruction meeting with the Frederick County E&SC Administrator. 2. Install construction entrance, silt fence, sediment basin, and diversions as indicated. 3. Clear and strip topsoil within the limits of disturbance and stockpile as necessary with silt fence protection on the downstream side of the stockpile. 4. Remove any unsuitable material which will interfere with grading and/or stability of fill areas and dispose of properly. 5. Perform the necessary grading for construction to bring the proposed site to the design elevations provided on the grading plan. Construction activities should be such that erosion and daily land disturbance is minimized as much as possible. 6. Once grading operations are complete, remove any sediment deposition from the sediment basin and convert the outlet structure to its permanent configuration. 7. Once all construction activities are complete and all areas stabilized, schedule inspection with the Frederick County E&SC Administrator. Please note that the Notice of Termination (NOT) package needs to be submitted, and accepted as complete, prior to scheduling a final site inspection. Information pertaining to the NOT requirements can be found on the Frederick County website. 8. Once the Frederick County E&SC Administrator has granted approval, remove temporary erosion and sediment control measures and stabilize any areas disturbed during removal of these measures. STORMWATER MANAGEMENT SUMMARY Pre-Development Condition Summary In the pre-development condition, the site is comprised of a single drainage area which flows in an easterly direction off the site. The area is described as: • DA ‘A’ – This area consists of 5.93 acres and includes the entire project site (5.48 acres) as well as the area fronting the site on Shady Elm Road (0.45 acres). The existing land cover consists of range grasses with pockets of trees. A portion of the site was cleared in order to conduct required site investigations, but the stormwater calculations assumed the previous cover condition prior to clearing activities. This area drains to an existing swale that flows off the site in the southeasterly direction. Post-Development Condition Summary In the post-development condition, the site and surrounding contributing areas is divided into a single drainage area which ultimately discharges in the same location as the area identified in the pre-developed analysis. That area is described as: • DA ‘A’ – This area consists of a total of 5.93 acres that includes the identical drainage area comprised in the pre-developed condition. For post-development, this area is further subdivided by three separate sub-areas: o DA ‘A’ (to SWMB) - , This sub-area includes 4.81 acres that contains a vast majority of the area to be developed. The runoff from this area is directed to the proposed on-site stormwater management basin located near the eastern property boundary, and is discharged into an existing swale that flows to the southeast from the site. o DA ‘A’ (offsite to SWMB) – This sub-area includes 0.45 acres that contains the off-site area along Shady Elm Road (within the R/W), which all drains to the proposed onsite stormwater management basin and is controlled prior to discharge from the site. o DA ‘A’ (SWMB Bypass) – This sub-area includes 0.67 acres that bypass the proposed stormwater management basin, but converges with the discharge from the basin and is directed to an existing swale that flows to the southeast from the site. Channel Protection • DA ‘A’ – This area discharges into a natural (undefined) channel at the eastern property line, therefore the Energy Balance equation is utilized to verify compliance with the regulations. The computed 1-year peak flow of 2.55 cfs is less than the allowable discharge of 2.59 cfs, therefore the site is in compliance with channel protection requirements. Flood Protection • DA ‘A’ – The existing stormwater conveyance system does not indicate evidence that localized flooding occurs. However, the post-developed peak flow rates resulting from the 10-year 24-hour storms are controlled via the on-site stormwater management basin which reduces the post- developed peak flow rate (13.87 cfs) to less than the pre-developed rate (14.08 cfs). Therefore, further downstream analysis is not warranted and flood protection requirements are met. The 1, 2, 10, 25, and 100-year storms were analyzed to determine the impacts of the post-development runoff in comparison to the pre-developed runoff rates. The following table presents a comparison of the pre vs. post-development flows for the subject area: DRAINAGE AREA 1-YR (CFS) 2-YR (CFS) 10-YR (CFS) 25-YR (CFS) 100-YR (CFS) TOTAL PRE FOR DA 'A' 4.83 7.15 14.08 18.93 27.77 TOTAL POST FOR DA 'A' 2.55 3.06 13.87 21.39 31.74 Please note that the off-site drainage area for DA ‘A’ is also included in the above totals, since that area drains onto the subject site and is therefore controlled via the on-site storm sewer system and stormwater management basin. The 100-year storm event was also analyzed to determine adequacy of the proposed stormwater management basin. The resulting 100-year storm elevations indicate that a minimum 1-foot of freeboard is provided at the basin embankment, assuming discharge strictly from the emergency spillway. Water Quality Utilizing the Virginia Runoff Reduction Method spreadsheets (see Engineering Report), there is a Total Phosphorus (TP) load reduction requirement of 3.25 lbs/yr. The total TP load will be satisfied by purchasing nutrient credits in order to fulfill the TP reduction requirement of 3.25 lbs/yr. CHANNEL PROTECTION - ENERGY BALANCE EQUATION SHADY ELM CONTRACTOR STORAGE DRAINAGE AREA 'A' MAX PEAK FLOW FOR 1-YEAR, 24-HOUR STORM: ACTUAL DEVELOPED CONDITION: QDEV = ALLOWABLE DEVELOPED PEAK FLOW RATE (CFS) I.F. = IMPROVEMENT FACTOR (0.8 IF > 1 AC., 0.9 IF ≤ 1 AC.) AREA = 5.48 AC. I.F. = 0.8 QPRE = 4.65 CFS RVPRE = 0.77 IN. RVDEV = 1.59 IN. QDEV ≤1.80 CFS QDEV ≤2.59 CFS FORESTED CONDITION CHECK: QFOREST = 3.99 CFS RVFOREST = 0.66 IN. RVDEV = 1.59 IN. QDEV =1.66 CFS QDEV =2.54 CFS (INCLUDES OFF-SITE 0.79 CFS) USE THE GREATER OF THE TWO QDEV VALUES, THEREFORE QDEV = 2.59 CFS COMPUTED PEAK FLOW FOR 1-YEAR, 24-HOUR STORM = 2.55 CFS NOTE: REFER TO HYDROGRAPH #9 2.55 CFS ≤2.59 ((1.69 * 4.81 ac.) + (0.87 * 0.67 ac.)) / 5.48 ac. QFOREST = FOREST CONDITION PEAK FLOW RATE (CFS) RVFOREST = FOREST CONDITION RUNOFF VOLUME (IN.) RVDEV = DEVELOPED RUNOFF VOLUME (IN.) THERE IS AN ADDITIONAL 0.45 ACRES (OFFSITE FROM WEST) THAT FLOWS TO THE SAME DISCHARGE ANALYSIS POINT. THEREFORE, THE 1-YEAR STORM PEAK DISCHARGE FOR THAT OFF-SITE AREA (0.79 CFS) IS ADDED TO THE ALLOWABLE DISCHARGE. REFER TO SWM NARRATIVE FOR FURTHER EXPLANATION. QDEV = (QFOREST * RVFOREST) / RVDEV, WHERE: QDEV = ALLOWABLE DEVELOPED PEAK FLOW RATE (CFS) CFS, THEREFORE OK RVDEV = DEVELOPED RUNOFF VOLUME (IN.) PROJECT: LOCATION: QDEV ≤ I.F. * (QPRE * RVPRE) / RVDEV, WHERE: QPRE = PRE-DEVELOPED PEAK FLOW RATE (CFS) RVPRE = PRE-DEVELOPED RUNOFF VOLUME (IN.) FLOOD PROTECTION SHADY ELM CONTRACTOR STORAGE DRAINAGE AREA 'A' QPRE (10-YR) = 14.08 CFS QPOST (10-YR) =13.87 CFS SINCE QPOST (10-YR) IS LESS THAN QPRE (10-YR), FLOOD PROTECTION REQUIREMENTS ARE MET AND NO FURTHER ANALYSIS IS REQUIRED. PROJECT: LOCATION: IT IS OUR UNDERSTANDING THAT THE EXISTING DRAINAGE SYSTEM AT THIS LOCATION DOES NOT EXPERIENCE SIGNIFICANT FLOODING. THEREFORE, THE 10- YEAR PRE AND POST-DEVELOPED STORMS ARE COMPARED TO SEE IF THE POST- DEVELOPED FLOW IS LESS THAN THE PRE-DEVELOPED FLOW. VRRM SPREADSHEET SUMMARY SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 Project Name: Date: BMP Design Specifications List: Site Information Post-Development Project (Treatment Volume and Loads) Land Cover (acres) A Soils B Soils C Soils D Soils Totals Forest (acres) -- undisturbed, protected forest or reforested land 0.00 Mixed Open (acres) -- undisturbed/infrequently maintained grass or shrub land 0.00 Managed Turf (acres) -- disturbed, graded for yards or other turf to be mowed/managed 2.07 2.07 Impervious Cover (acres)3.41 3.41 5.48 3.25 Forest Cover (acres) 0.00 0.3131 Weighted Rv (forest) 0.00 13,638 % Forest 0%4.68 Mixed Open (acres) 0.00 60.71 Weighted Rv (mixed open) 0.00 % Mixed Open 0% Managed Turf Cover (acres) 2.07 Weighted Rv (turf) 0.25 % Managed Turf 38% Impervious Cover (acres) 3.41 Rv (impervious) 0.95 % Impervious 62% Site Area (acres)5.48 Site Rv 0.69 DEQ Virginia Runoff Reduction Method New Development Compliance Spreadsheet - Version 4.1 Treatment Volume (cubic feet) TP Load (lb/yr) TN Load (lb/yr) Post-Development Requirement for Site Area LAND COVER SUMMARY -- POST DEVELOPMENT Treatment Volume and Nutrient Loads Treatment Volume (acre-Ō) Land Cover Summary SHADY ELM CONTRACTOR STORAGE 3/5/2026 2024 Stds & Specs TP Load Reduction Required (lb/yr) data input cells constant values calculation cells final results data input cells constant values calculation cells final results CLEAR ALL (Ctrl+Shift+R) Drainage Area A Drainage Area A Land Cover (acres) A Soils B Soils C Soils D Soils Totals Land Cover Rv Composite Loading P Forest (acres)0.00 0.00 0.00 Mixed Open (acres)0.00 0.00 0.00 Managed Turf (acres)2.07 2.07 0.25 0.85 Impervious Cover (acres) 3.41 3.41 0.95 0.86 4.68 Total 5.48 13,638 Stormwater Best Management Practices (RR = Runoff Reduction) Practice Runoff Reduction Credit (%) Mixed Open Credit Area (acres) Managed Turf Credit Area (acres) Impervious Cover Credit Area (acres) Volume from Upstream Practice (ft3) Runoff Reduction (ft3) Remaining Runoff Volume (ft3) Total BMP Treatment Volume (ft3) Phosphorus Removal Efficiency (%) Phosphorus Load from Upstream Practices (lb) Untreated Phosphorus Load to Practice (lb) Phosphorus Removed By Practice (lb) Remaining Phosphorus Load (lb) 1. Vegetated Roof (RR) 1.a. Vegetated Roof #1 (P-FIL-02) 45 0000 0.000.000.00 1.b. Vegetated Roof #2 (P-FIL-02) 60 0000 0.000.000.00 2. Rooftop Disconnection (RR) 2.a. Simple Disconnection to A/B Soils (P-FIL-01)50 000000.000.000.000.00 2.b. Simple Disconnection to C/D Soils (P-FIL-01)25 000000.000.000.000.00 2.c. To Soil Amended Filter Path as per specifications (existing C/D soils) (P-FIL-08)50 000000.000.000.000.00 2.d. To Dry Well or French Drain #1, Micro-Infilration #1 (P-FIL-04)50 0000250.000.000.000.00 2.e. To Dry Well or French Drain #2, Micro-Infiltration #2 (P-FIL-04)90 0000250.000.000.000.00 2.f. To Rain Garden #1, Micro-Bioretention #1 (P-FIL-05)40 0000250.000.000.000.00 2.g. To Rain Garden #2, Micro-Bioretention #2 (P-FIL-05)80 0000500.000.000.000.00 2.h. To Rainwater Harvesting (P-BAS-04)0 000000.000.000.000.00 2.i. To Stormwater Planter, Urban Bioretention (P-FIL-05)40 0000250.000.000.000.00 3. Permeable Pavement (RR) 3.a. Permeable Pavement #1 (P-FIL-03)45 0000250.000.000.000.00 3.b. Permeable Pavement #2 (P-FIL-03) 75 0 0 0 25 0.00 0.00 0.00 4. Grass Channel (RR) 4.a. Grass Channel A/B Soils (P-CNV-01) 20 0000150.000.000.000.00 4.b. Grass Channel C/D Soils (P-CNV-01) 10 0000150.000.000.000.00 4.c. Grass Channel with Compost Amended Soils as per specs (P-FIL-08)20 0000150.000.000.000.00 5. Dry Swale (RR) 5.a. Dry Swale #1 (P-CNV-02)40 0000200.000.000.000.00 5.b. Dry Swale #2 (P-CNV-02)60 0000400.000.000.000.00 6. Bioretention (RR) 6.a. Bioretention #1 or Micro-Bioretention #1 or Urban Bioretention (P-FIL-05)40 0000250.000.000.000.00 6.b. Bioretention #2 or Micro-Bioretention #2 (P-FIL-05)80 0000500.000.000.000.00 7. Infiltration (RR) 7.a. Infiltration #1 (P-FIL-04)50 0000250.000.000.000.00 7.b. Infiltration #2 (P-FIL-04)90 0000250.000.000.000.00 8. Extended Detention Pond (RR) 8.a. ED #1 (P-BAS-03) 0 0000150.000.000.000.00 8.b. ED #2 (P-BAS-03) 15 0000150.000.000.000.00 9. Sheetflow to Filter/Open Space (RR) 9.a. Sheetflow to Conservation Area, A/B Soils (P-FIL-07)75 000000.000.000.000.00 9.b. Sheetflow to Conservation Area, C/D Soils (P-FIL-07)50 000000.000.000.000.00 9.c. Sheetflow to Vegetated Filter Strip, A Soils or Compost Amended B/C/D Soils (Spec P-FIL-07 & P-FIL-08) 50 000000.000.000.000.00 10. Regenerative Stormwater Conveyance 10.a. Regenerative Stormwater Conveyance (P- CNV-04)0 0000200.000.000.000.00 10.b. Regenerative Stormwater Conveyance (P- CNV-04)0 0000400.000.000.000.00 11. Tree BMP 11.a. Trees over Pervious, A/B (P-FIL-09)16 000000.000.000.000.00 11.b. Trees over Pervious, C/D (P-FIL-09)12 000000.000.000.000.00 11.c. Trees over Impervious (P-FIL-09)3.5 000000.000.000.000.00 TOTAL IMPERVIOUS COVER TREATED (ac)0.00 AREA CHECK:OK. TOTAL MIXED OPEN TREATED (ac)0.00 AREA CHECK:OK. TOTAL MANAGED TURF AREA TREATED (ac)0.00 AREA CHECK:OK. TOTAL RUNOFF REDUCTION IN D.A. A (ft3)0 TOTAL PHOSPHORUS AVAILABLE FOR REMOVAL IN D.A. A (lb/yr)4.68 TOTAL PHOSPHORUS REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)0.00 TOTAL PHOSPHORUS REMAINING AFTER APPLYING RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)4.68 SEE WATER QUALITY COMPLIANCE TAB FOR SITE COMPLIANCE CALCULATIONS 12. Wet Swale (no RR) 12.a. Wet Swale #1 (P-CNV-03)0 0000200.000.000.000.00 12.b. Wet Swale #2 (P-CNV-03)0 0000400.000.000.000.00 13. Filtering Practices (no RR) 13.a.Filtering Practice #1 (P-FIL-06)0 0000600.000.000.000.00 13.b. Filtering Practice #2 (P-FIL-06)0 0000650.000.000.000.00 14. Constructed Wetland (no RR) 14.a.Constructed Wetland #1 (P-BAS-01)0 0000500.000.000.000.00 14.b. Constructed Wetland #2 (P-BAS-01)0 0000750.000.000.000.00 15. Wet Ponds (no RR) 15.a. Wet Pond #1 (P-BAS-02)0 0000500.000.000.000.00 15.b. Wet Pond #1 (Coastal Plain) (P-BAS-02)0 0000450.000.000.000.00 15.c. Wet Pond #2 (P-BAS-02)0 0000750.000.000.000.00 15.d. Wet Pond #2 (Coastal Plain) (P-BAS-02)0 0000650.000.000.000.00 16.a. Manufactured Treatment Device- Hydrodynamic 0 0000200.000.000.000.00 16.b. Manufactured Treatment Device- Filtering 0 0000200.000.000.000.00 16.c. Manufactured Treatment Device-Generic 0 0000200.000.000.000.00 TOTAL IMPERVIOUS COVER TREATED (ac)0.00 AREA CHECK:OK. TOTAL MIXED OPEN TREATED (ac)0.00 AREA CHECK:OK. TOTAL MANAGED TURF AREA TREATED (ac)0.00 AREA CHECK:OK. TOTAL PHOSPHORUS REMOVAL REQUIRED ON SITE (lb/yr)3.25 TOTAL PHOSPHORUS AVAILABLE FOR REMOVAL IN D.A. A (lb/yr)4.68 TOTAL PHOSPHORUS REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)0.00 TOTAL PHOSPHORUS REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)0.00 TOTAL PHOSPHORUS LOAD REDUCTION ACHIEVED IN D.A. A (lb/yr)0.00 TOTAL PHOSPHORUS REMAINING AFTER APPLYING BMP LOAD REDUCTIONS IN D.A. A (lb/yr)4.68 SEE WATER QUALITY COMPLIANCE TAB FOR SITE COMPLIANCE CALCULATIONS NITROGEN REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)0.00 NITROGEN REMOVED WITHOUT RUNOFF REDUCTION PRACTICES IN D.A. A (lb/yr)0.00 TOTAL NITROGEN REMOVED IN D.A. A (lb/yr)0.00 --Select from dropdown lists-- Total Phosphorus Available for Removal in D.A. A (lb/yr) Post Development Treatment Volume in D.A. A (ft3) VRRM 4.1, 2024 Downstream Practice to be Employed 16. Manufactured Treatment Devices (no RR) CLEAR BMP AREAS Site Results (Water Quality Compliance) VRRM 4.1, 2024 Area ChecksD.A. A D.A. B D.A. C D.A. D D.A. E AREA CHECKFOREST (ac)0.00 0.00 0.00 0.00 0.00OK.MIXED OPEN AREA (ac)0.00 0.00 0.00 0.00 0.00OK.MIXED OPEN AREA TREATED (ac)0.00 0.00 0.00 0.00 0.00OK.MANAGED TURF AREA (ac)2.07 0.00 0.00 0.00 0.00OK.MANAGED TURF AREA TREATED (ac)0.00 0.00 0.00 0.00 0.00OK.IMPERVIOUS COVER (ac)3.41 0.00 0.00 0.00 0.00OK.IMPERVIOUS COVER TREATED (ac)0.00 0.00 0.00 0.00 0.00OK.AREA CHECK OK. OK. OK. OK. OK.Site Treatment Volume (ft3)13,638Runoff Reduction Volume and TP By Drainage AreaD.A. A D.A. B D.A. C D.A. D D.A. E TOTALRUNOFF REDUCTION VOLUME ACHIEVED (ft3)000000TP LOAD AVAILABLE FOR REMOVAL (lb/yr)4.68 0.00 0.00 0.00 0.00 4.68TP LOAD REDUCTION ACHIEVED (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00TP LOAD REMAINING (lb/yr)4.68 0.00 0.00 0.00 0.00 4.68NITROGEN LOAD REDUCTION ACHIEVED (lb/yr)0.00 0.00 0.00 0.00 0.00 0.00Total Phosphorus FINAL POST-DEVELOPMENT TP LOAD (lb/yr)4.68TP LOAD REDUCTION REQUIRED (lb/yr)3.25TP LOAD REDUCTION ACHIEVED (lb/yr)0.00TP LOAD REMAINING (lb/yr):4.68REMAINING TP LOAD REDUCTION REQUIRED (lb/yr):3.25Total Nitrogen (For Information Purposes)POST-DEVELOPMENT LOAD (lb/yr)60.71NITROGEN LOAD REDUCTION ACHIEVED (lb/yr)0.00REMAINING POST-DEVELOPMENT NITROGEN LOAD (lb/yr)60.71 Runoff Volume and Curve Number Calculations,VRRM 4.1, 2024 1-year storm 2-year storm 10-year storm 2.40 2.89 4.21 *Notes (see below): A Soils B Soils C Soils D Soils Total Area (acres):5.48 Area (acres) 0.00 0.00 0.00 0.00 CN 30 55 70 77 0 Area (acres) 0.00 0.00 0.00 0.00 CN 34 59 72 79 Area (acres) 0.00 0.00 0.00 2.07 CN 39 61 74 80 Area (acres) 0.00 0.00 0.00 3.41 CN 98 98 98 98 CN(D.A. A) 91 1-year storm 2-year storm 10-year storm 1.52 1.97 3.22 1.52 1.97 3.22 Adjusted CN*91 91 91 *See Notes above RVDeveloped (watershed-inch) with no Runoff Reduction* RVDeveloped (watershed-inch) with Runoff Reduction* Impervious Cover Mixed Open -- undisturbed/infrequently maintained grass or shrub land Enter design storm rainfall depths (in): [1] The curve numbers and runoff volumes computed in this spreadsheet for each drainage area are limited in their applicability for determining and demonstrating compliance with water quantity requirements. See VRRM User's Guide and Documentation for additional information. [2] Runoff Volume (RV) for pre- and post-development drainage areas must be in volumetric units (e.g., acre-feet or cubic feet) when using the Energy Balance Equation. Runoff measured in watershed-inches and shown in the spreadsheet as RV(watershed-inch) can only be used in the Energy Balance Equation when the pre- and post-development drainage areas are equal. Otherwise RV(watershed-inch) must be multiplied by the drainage area. [3] Adjusted CNs are based on runoff reduction volumes as calculated in D.A. tabs. An alternative CN adjustment calculation for Vegetated Roofs is included in BMP specification No. 5. Drainage Area Curve Numbers and Runoff Depths* Drainage Area A Forest -- undisturbed, protected forest or reforested land Runoff Reduction Volume (ft3): Managed Turf -- disturbed, graded for yards or other turf to be mowed/managed Use NOAA Atlas 14 (http://hdsc.nws.noaa.gov/hdsc/pfds/) TR-55 SCS METHOD WORKSHEETS SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 Project By Date Location Checked Date Check one: 1. Runoff curve number acres mi2 % 98 14.70 80 136.00 77 279.51 - - - - - - *Use only one CN source per line 430.21 total product 430.21 total area 5.48 2. Runoff Frequency …………………………………...…….yr Rainfall, P (24-hour) …………………....…..……..in Runoff, Q …………………………………..………in (Use P and CN with table 2-1, figure 2-1, or equations 2-3 and 2-4) 2.40 2.89 4.21 0.77 1.11 2.14 79 Storm #1 Storm #2 Storm #3 1 2 10 Totals 5.48 CN (weighted)===78.51 ;Use CN 0.15 D Range - Good Condition 1.70 D Woods - Good Condition 3.63Figure 2-3Figure 2-4(cover type, treatment, and hydrologic condition; percent impervious; unconnected/connected impervious area ratio) Impervious Cover - Road, Roof, Driveway Present Developed Soil name & hydrologic group Cover description CN*Area Product of CN x area Table 2-2Worksheet 2: Runoff curve number and runoff Shady Elm Contractor Storage DDD 03/05/26 Pre-Dev. DA 'A' (onsite)DDD 03/05/26 Project By Date Location Checked Date Drainage Area Check One:Present Developed Check One:TC Tt through subarea Notes:Space for as many as two segments per flow type can be used for each worksheet. Include a map, schematic, or description of flow segments. Sheet Flow (Applicable to TC only) Segment ID 1. Surface description (table 3-1) 2. Manning's roughness coefficient, n (table 3-1) 3. Flow Length, L (not to exceed 300')ft 4. Two-year 24-hour rainfall, P2 in 5. Land slope, s ft/ft 6. Tt =hr 0.285 0.000 =0.285 Shallow Concentrated Flow Segment ID 7. Surface description 8. Flow Length, L ft 9. Watercourse slope, s ft/ft 10. Average velocity, V (figure 3-1)ft/s 11. Tt =hr 0.047 0.000 =0.047 Channel Flow Segment ID 12. Cross sectional flow area, a ft2 13. Wetted perimeter, PW ft 14. Hydraulic radius, r = a/Pw ft 15. Channel Slope, s ft/ft 16. Manning's roughness coefficient, n 17. V =ft/s 18. Flow length, L ft 19. Tt =hr 0.00 0.00 =0.000 (Kirpich) 20. Watershed or subarea TC or Tt (Total)19.933 Minutes Worksheet 3: Time of Concentration (TC) or Travel Time (Tt) Shady Elm Contractor Storage DDD 03/05/26 Frederick County, VA DDD 03/05/26Pre-Dev. DA 'A' AB Woods 0.40 100.00 2.89 0.0400 + BC Unpaved 530.00 0.038 3.15 0.00 + CD + Project By Date Location Checked Date Check one: 1. Runoff curve number acres mi2 % 98 11.76 80 15.20 77 10.78 - - - - - - *Use only one CN source per line 37.74 total product 37.74 total area 0.45 2. Runoff Frequency …………………………………...…….yr Rainfall, P (24-hour) …………………....…..……..in Runoff, Q …………………………………..………in (Use P and CN with table 2-1, figure 2-1, or equations 2-3 and 2-4) Worksheet 2: Runoff curve number and runoff Shady Elm Contractor Storage DDD 03/05/26 Pre-Dev. DA 'A' (offsite)DDD 03/05/26 Present Developed Soil name & hydrologic group Cover description CN*Area Product of CN x area Table 2-2Figure 2-3Figure 2-4(cover type, treatment, and hydrologic condition; percent impervious; unconnected/connected impervious area ratio) Impervious Cover - Road, Roof, Driveway 0.12 D Range - Good Condition 0.19 D Woods - Good Condition 0.14 Totals 0.45 CN (weighted)===83.87 ;Use CN 84 Storm #1 Storm #2 Storm #3 1 2 10 2.40 2.89 4.21 1.04 1.43 2.56 Project By Date Location Checked Date Check one: 1. Runoff curve number acres mi2 % 98 330.26 80 115.20 77 0 - - - - - - *Use only one CN source per line 445.46 total product 445.46 total area 4.81 2. Runoff Frequency …………………………………...…….yr Rainfall, P (24-hour) …………………....…..……..in Runoff, Q …………………………………..………in (Use P and CN with table 2-1, figure 2-1, or equations 2-3 and 2-4) 2.40 2.89 4.21 1.69 2.15 3.42 93 Storm #1 Storm #2 Storm #3 1 2 10 Totals 4.81 CN (weighted)===92.61 ;Use CN 3.37 D Managed Turf - Good Condition 1.44 D Forest - Good Condition 0.00Figure 2-3Figure 2-4(cover type, treatment, and hydrologic condition; percent impervious; unconnected/connected impervious area ratio) Impervious Cover - Road, Roof, Driveway Present Developed Soil name & hydrologic group Cover description CN*Area Product of CN x area Table 2-2Worksheet 2: Runoff curve number and runoff Shady Elm Contractor Storage DDD 03/05/25 Post-Dev. DA to SWMB (onsite)DDD 03/05/25 Project By Date Location Checked Date Drainage Area Check One:Present Developed Check One:TC Tt through subarea Notes:Space for as many as two segments per flow type can be used for each worksheet. Include a map, schematic, or description of flow segments. Sheet Flow (Applicable to TC only) Segment ID 1. Surface description (table 3-1) 2. Manning's roughness coefficient, n (table 3-1) 3. Flow Length, L (not to exceed 300')ft 4. Two-year 24-hour rainfall, P2 in 5. Land slope, s ft/ft 6. Tt =hr 0.011 0.000 =0.011 Shallow Concentrated Flow Segment ID 7. Surface description 8. Flow Length, L ft 9. Watercourse slope, s ft/ft 10. Average velocity, V (figure 3-1)ft/s 11. Tt =hr 0.066 0.000 =0.066 Channel Flow Segment ID 12. Cross sectional flow area, a ft2 13. Wetted perimeter, PW ft 14. Hydraulic radius, r = a/Pw ft 15. Channel Slope, s ft/ft 16. Manning's roughness coefficient, n 17. V =ft/s 18. Flow length, L ft 19. Tt =hr 0.00 0.00 =0.050 (Kirpich) 20. Watershed or subarea TC or Tt (Total)7.626 Minutes Worksheet 3: Time of Concentration (TC) or Travel Time (Tt) Shady Elm Contractor Storage DDD 07/11/25 Frederick County, VA DDD 07/11/25Post-Dev. DA to SWMB (onsite) AB Asphalt 0.01 85.00 2.89 0.0800 + BC Paved 595.00 0.015 2.49 0.00 + CD + Project By Date Location Checked Date Check one: 1. Runoff curve number acres mi2 % 98 3.92 80 50.40 77 0 - - - - - - *Use only one CN source per line 54.32 total product 54.32 total area 0.67 2. Runoff Frequency …………………………………...…….yr Rainfall, P (24-hour) …………………....…..……..in Runoff, Q …………………………………..………in (Use P and CN with table 2-1, figure 2-1, or equations 2-3 and 2-4) 2.40 2.89 4.21 0.87 1.23 2.30 81 Storm #1 Storm #2 Storm #3 1 2 10 Totals 0.67 CN (weighted)===81.07 ;Use CN 0.04 D Managed Turf - Good Condition 0.63 D Forest - Good Condition 0.00Figure 2-3Figure 2-4(cover type, treatment, and hydrologic condition; percent impervious; unconnected/connected impervious area ratio) Impervious Cover - Road, Roof, Driveway Present Developed Soil name & hydrologic group Cover description CN*Area Product of CN x area Table 2-2Worksheet 2: Runoff curve number and runoff Shady Elm Contractor Storage DDD 03/05/25 Post-Dev. DA SWMB Bypass (onsite)DDD 03/05/25 Project By Date Location Checked Date Check one: 1. Runoff curve number acres mi2 % 98 15.68 80 23.20 77 0 - - - - - - *Use only one CN source per line 38.88 total product 38.88 total area 0.45 2. Runoff Frequency …………………………………...…….yr Rainfall, P (24-hour) …………………....…..……..in Runoff, Q …………………………………..………in (Use P and CN with table 2-1, figure 2-1, or equations 2-3 and 2-4) 2.40 2.89 4.21 1.16 1.57 2.74 86 Storm #1 Storm #2 Storm #3 1 2 10 Totals 0.45 CN (weighted)===86.40 ;Use CN 0.16 D Managed Turf - Good Condition 0.29 D Forest - Good Condition 0.00Figure 2-3Figure 2-4(cover type, treatment, and hydrologic condition; percent impervious; unconnected/connected impervious area ratio) Impervious Cover - Road, Roof, Driveway Present Developed Soil name & hydrologic group Cover description CN*Area Product of CN x area Table 2-2Worksheet 2: Runoff curve number and runoff Shady Elm Contractor Storage DDD 03/05/25 Post-Dev. DA to SWMB (offsite)DDD 03/05/25 HYDROLOGIC MODELING AND CALCULATIONS SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 1 2 3 4 5 6 7 8 9 Watershed Model Schematic Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Project: SWM-03-05-26.gpw Thursday, 03 / 5 / 2026 Hyd.Origin Description Legend 1 SCS Runoff Pre-Dev-onsite 2 SCS Runoff Pre-Dev-offsite 3 Combine Total Pre-Dev 4 SCS Runoff Post to SWMB - offsite 5 SCS Runoff Post to SWMB - onsite 6 Combine Total Post-Dev to SWMB 7 Reservoir SWMB routing 8 SCS Runoff Post-Bypass 9 Combine Total Post-Dev Discharge Pond Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Pond No. 1 - SWMB Pond Data Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 772.00 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 772.00 00 0 0 1.00 773.00 1,500 500 500 2.00 774.00 3,250 2,319 2,819 3.00 775.00 5,300 4,233 7,052 4.00 776.00 7,400 6,320 13,372 5.00 777.00 9,000 8,186 21,558 6.00 778.00 10,300 9,642 31,200 7.00 779.00 11,600 10,942 42,143 7.50 779.50 12,500 6,023 48,166 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in)= 18.00 6.00 0.00 0.00 Span (in)= 18.00 6.00 0.00 0.00 No. Barrels = 1 110 Invert El. (ft)= 772.00 772.00 0.00 0.00 Length (ft)= 50.00 0.00 0.00 0.00 Slope (%)= 0.50 0.00 0.00 n/a N-Value = .012 .013 .013 n/a Orifice Coeff.= 0.60 0.60 0.60 0.60 Multi-Stage = n/a NoNoNo Crest Len (ft)= 12.57 20.00 0.00 0.00 Crest El. (ft)= 776.65 777.65 0.00 0.00 Weir Coeff.= 3.33 2.60 3.33 3.33 Weir Type = 1 Broad --- --- Multi-Stage = Yes NoNoNo Exfil.(in/hr)= 0.000 (by Contour) TW Elev. (ft)= 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 Stage (ft) 0.00 772.00 2.00 774.00 4.00 776.00 6.00 778.00 8.00 780.00 Elev (ft) Discharge (cfs) Stage / Discharge Total Q Hydrograph Return Period Recap Hyd. Hydrograph Inflow Peak Outflow (cfs) Hydrograph No. type hyd(s)Description (origin) 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr 1 SCS Runoff ------ 4.654 6.859 ------- ------- 13.55 18.27 ------- 26.85 Pre-Dev-onsite 2 SCS Runoff ------ 0.793 1.082 ------- ------- 1.916 2.479 ------- 3.480 Pre-Dev-offsite 3 Combine 1, 2 4.834 7.153 ------- ------- 14.08 18.93 ------- 27.77 Total Pre-Dev 4 SCS Runoff ------ 0.882 1.186 ------- ------- 2.033 2.599 ------- 3.598 Post to SWMB - offsite 5 SCS Runoff ------ 12.53 15.78 ------- ------- 24.47 30.14 ------- 40.10 Post to SWMB - onsite 6 Combine 4, 5 13.41 16.95 ------- ------- 26.45 32.66 ------- 43.57 Total Post-Dev to SWMB 7 Reservoir 6 1.767 1.902 ------- ------- 13.26 19.86 ------- 29.72 SWMB routing 8 SCS Runoff ------ 0.994 1.398 ------- ------- 2.587 3.413 ------- 4.898 Post-Bypass 9 Combine 7, 8 2.551 3.064 ------- ------- 13.87 21.39 ------- 31.74 Total Post-Dev Discharge Proj. file: SWM-03-05-26.gpw Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Summary Report Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff 4.654 2 726 15,340 ------ ------ ------ Pre-Dev-onsite 2 SCS Runoff 0.793 2 718 1,591 ------ ------ ------ Pre-Dev-offsite 3 Combine 4.834 2 724 16,931 1, 2 ------ ------ Total Pre-Dev 4 SCS Runoff 0.882 2 716 1,780 ------ ------ ------ Post to SWMB - offsite 5 SCS Runoff 12.53 2 718 29,429 ------ ------ ------ Post to SWMB - onsite 6 Combine 13.41 2 718 31,209 4, 5 ------ ------ Total Post-Dev to SWMB 7 Reservoir 1.767 2 738 31,207 6 775.75 11,766 SWMB routing 8 SCS Runoff 0.994 2 718 1,988 ------ ------ ------ Post-Bypass 9 Combine 2.551 2 718 33,195 7, 8 ------ ------ Total Post-Dev Discharge SWM-03-05-26.gpw Return Period: 1 Year Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 1 Pre-Dev-onsite Hydrograph type = SCS Runoff Peak discharge = 4.654 cfs Storm frequency = 1 yrs Time to peak = 12.10 hrs Time interval = 2 min Hyd. volume = 15,340 cuft Drainage area = 5.480 ac Curve number = 79 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 20.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 Q (cfs) Time (hrs) Pre-Dev-onsite Hyd. No. 1 -- 1 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 2 Pre-Dev-offsite Hydrograph type = SCS Runoff Peak discharge = 0.793 cfs Storm frequency = 1 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 1,591 cuft Drainage area = 0.450 ac Curve number = 84 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 0.10 0.10 0.20 0.20 0.30 0.30 0.40 0.40 0.50 0.50 0.60 0.60 0.70 0.70 0.80 0.80 0.90 0.90 1.00 1.00 Q (cfs) Time (hrs) Pre-Dev-offsite Hyd. No. 2 -- 1 Year Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 3 Total Pre-Dev Hydrograph type = Combine Peak discharge = 4.834 cfs Storm frequency = 1 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 16,931 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 5.930 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 Q (cfs) Time (hrs) Total Pre-Dev Hyd. No. 3 -- 1 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 4 Post to SWMB - offsite Hydrograph type = SCS Runoff Peak discharge = 0.882 cfs Storm frequency = 1 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 1,780 cuft Drainage area = 0.450 ac Curve number = 86 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 0.10 0.10 0.20 0.20 0.30 0.30 0.40 0.40 0.50 0.50 0.60 0.60 0.70 0.70 0.80 0.80 0.90 0.90 1.00 1.00 Q (cfs) Time (hrs) Post to SWMB - offsite Hyd. No. 4 -- 1 Year Hyd No. 4 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 5 Post to SWMB - onsite Hydrograph type = SCS Runoff Peak discharge = 12.53 cfs Storm frequency = 1 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 29,429 cuft Drainage area = 4.810 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) Post to SWMB - onsite Hyd. No. 5 -- 1 Year Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 6 Total Post-Dev to SWMB Hydrograph type = Combine Peak discharge = 13.41 cfs Storm frequency = 1 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 31,209 cuft Inflow hyds. = 4, 5 Contrib. drain. area = 5.260 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) Total Post-Dev to SWMB Hyd. No. 6 -- 1 Year Hyd No. 6 Hyd No. 4 Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 7 SWMB routing Hydrograph type = Reservoir Peak discharge = 1.767 cfs Storm frequency = 1 yrs Time to peak = 12.30 hrs Time interval = 2 min Hyd. volume = 31,207 cuft Inflow hyd. No. = 6 - Total Post-Dev to SWMB Max. Elevation = 775.75 ft Reservoir name = SWMB Max. Storage = 11,766 cuft Storage Indication method used. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) SWMB routing Hyd. No. 7 -- 1 Year Hyd No. 7 Hyd No. 6 Total storage used = 11,766 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 8 Post-Bypass Hydrograph type = SCS Runoff Peak discharge = 0.994 cfs Storm frequency = 1 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 1,988 cuft Drainage area = 0.670 ac Curve number = 81 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 0.10 0.10 0.20 0.20 0.30 0.30 0.40 0.40 0.50 0.50 0.60 0.60 0.70 0.70 0.80 0.80 0.90 0.90 1.00 1.00 Q (cfs) Time (hrs) Post-Bypass Hyd. No. 8 -- 1 Year Hyd No. 8 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 9 Total Post-Dev Discharge Hydrograph type = Combine Peak discharge = 2.551 cfs Storm frequency = 1 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 33,195 cuft Inflow hyds. = 7, 8 Contrib. drain. area = 0.670 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 Q (cfs) Time (hrs) Total Post-Dev Discharge Hyd. No. 9 -- 1 Year Hyd No. 9 Hyd No. 7 Hyd No. 8 Hydrograph Summary Report Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff 6.859 2 726 22,055 ------ ------ ------ Pre-Dev-onsite 2 SCS Runoff 1.082 2 716 2,184 ------ ------ ------ Pre-Dev-offsite 3 Combine 7.153 2 724 24,239 1, 2 ------ ------ Total Pre-Dev 4 SCS Runoff 1.186 2 716 2,402 ------ ------ ------ Post to SWMB - offsite 5 SCS Runoff 15.78 2 718 37,522 ------ ------ ------ Post to SWMB - onsite 6 Combine 16.95 2 718 39,924 4, 5 ------ ------ Total Post-Dev to SWMB 7 Reservoir 1.902 2 742 39,923 6 776.30 15,808 SWMB routing 8 SCS Runoff 1.398 2 718 2,803 ------ ------ ------ Post-Bypass 9 Combine 3.064 2 718 42,726 7, 8 ------ ------ Total Post-Dev Discharge SWM-03-05-26.gpw Return Period: 2 Year Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 1 Pre-Dev-onsite Hydrograph type = SCS Runoff Peak discharge = 6.859 cfs Storm frequency = 2 yrs Time to peak = 12.10 hrs Time interval = 2 min Hyd. volume = 22,055 cuft Drainage area = 5.480 ac Curve number = 79 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 20.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 6.00 6.00 7.00 7.00 Q (cfs) Time (hrs) Pre-Dev-onsite Hyd. No. 1 -- 2 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 2 Pre-Dev-offsite Hydrograph type = SCS Runoff Peak discharge = 1.082 cfs Storm frequency = 2 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 2,184 cuft Drainage area = 0.450 ac Curve number = 84 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 Q (cfs) Time (hrs) Pre-Dev-offsite Hyd. No. 2 -- 2 Year Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 3 Total Pre-Dev Hydrograph type = Combine Peak discharge = 7.153 cfs Storm frequency = 2 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 24,239 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 5.930 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 Q (cfs) Time (hrs) Total Pre-Dev Hyd. No. 3 -- 2 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 4 Post to SWMB - offsite Hydrograph type = SCS Runoff Peak discharge = 1.186 cfs Storm frequency = 2 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 2,402 cuft Drainage area = 0.450 ac Curve number = 86 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 Q (cfs) Time (hrs) Post to SWMB - offsite Hyd. No. 4 -- 2 Year Hyd No. 4 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 5 Post to SWMB - onsite Hydrograph type = SCS Runoff Peak discharge = 15.78 cfs Storm frequency = 2 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 37,522 cuft Drainage area = 4.810 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 Q (cfs) Time (hrs) Post to SWMB - onsite Hyd. No. 5 -- 2 Year Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 6 Total Post-Dev to SWMB Hydrograph type = Combine Peak discharge = 16.95 cfs Storm frequency = 2 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 39,924 cuft Inflow hyds. = 4, 5 Contrib. drain. area = 5.260 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 Q (cfs) Time (hrs) Total Post-Dev to SWMB Hyd. No. 6 -- 2 Year Hyd No. 6 Hyd No. 4 Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 7 SWMB routing Hydrograph type = Reservoir Peak discharge = 1.902 cfs Storm frequency = 2 yrs Time to peak = 12.37 hrs Time interval = 2 min Hyd. volume = 39,923 cuft Inflow hyd. No. = 6 - Total Post-Dev to SWMB Max. Elevation = 776.30 ft Reservoir name = SWMB Max. Storage = 15,808 cuft Storage Indication method used. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 Q (cfs) Time (hrs) SWMB routing Hyd. No. 7 -- 2 Year Hyd No. 7 Hyd No. 6 Total storage used = 15,808 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 8 Post-Bypass Hydrograph type = SCS Runoff Peak discharge = 1.398 cfs Storm frequency = 2 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 2,803 cuft Drainage area = 0.670 ac Curve number = 81 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 Q (cfs) Time (hrs) Post-Bypass Hyd. No. 8 -- 2 Year Hyd No. 8 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 9 Total Post-Dev Discharge Hydrograph type = Combine Peak discharge = 3.064 cfs Storm frequency = 2 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 42,726 cuft Inflow hyds. = 7, 8 Contrib. drain. area = 0.670 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 Q (cfs) Time (hrs) Total Post-Dev Discharge Hyd. No. 9 -- 2 Year Hyd No. 9 Hyd No. 7 Hyd No. 8 Hydrograph Summary Report Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff 13.55 2 724 42,476 ------ ------ ------ Pre-Dev-onsite 2 SCS Runoff 1.916 2 716 3,916 ------ ------ ------ Pre-Dev-offsite 3 Combine 14.08 2 724 46,391 1, 2 ------ ------ Total Pre-Dev 4 SCS Runoff 2.033 2 716 4,192 ------ ------ ------ Post to SWMB - offsite 5 SCS Runoff 24.47 2 718 59,793 ------ ------ ------ Post to SWMB - onsite 6 Combine 26.45 2 718 63,985 4, 5 ------ ------ Total Post-Dev to SWMB 7 Reservoir 13.26 2 726 63,983 6 777.06 22,171 SWMB routing 8 SCS Runoff 2.587 2 716 5,242 ------ ------ ------ Post-Bypass 9 Combine 13.87 2 724 69,225 7, 8 ------ ------ Total Post-Dev Discharge SWM-03-05-26.gpw Return Period: 10 Year Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 1 Pre-Dev-onsite Hydrograph type = SCS Runoff Peak discharge = 13.55 cfs Storm frequency = 10 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 42,476 cuft Drainage area = 5.480 ac Curve number = 79 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 20.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) Pre-Dev-onsite Hyd. No. 1 -- 10 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 2 Pre-Dev-offsite Hydrograph type = SCS Runoff Peak discharge = 1.916 cfs Storm frequency = 10 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 3,916 cuft Drainage area = 0.450 ac Curve number = 84 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 Q (cfs) Time (hrs) Pre-Dev-offsite Hyd. No. 2 -- 10 Year Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 3 Total Pre-Dev Hydrograph type = Combine Peak discharge = 14.08 cfs Storm frequency = 10 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 46,391 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 5.930 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 Q (cfs) Time (hrs) Total Pre-Dev Hyd. No. 3 -- 10 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 4 Post to SWMB - offsite Hydrograph type = SCS Runoff Peak discharge = 2.033 cfs Storm frequency = 10 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 4,192 cuft Drainage area = 0.450 ac Curve number = 86 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 Q (cfs) Time (hrs) Post to SWMB - offsite Hyd. No. 4 -- 10 Year Hyd No. 4 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 5 Post to SWMB - onsite Hydrograph type = SCS Runoff Peak discharge = 24.47 cfs Storm frequency = 10 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 59,793 cuft Drainage area = 4.810 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) Post to SWMB - onsite Hyd. No. 5 -- 10 Year Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 6 Total Post-Dev to SWMB Hydrograph type = Combine Peak discharge = 26.45 cfs Storm frequency = 10 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 63,985 cuft Inflow hyds. = 4, 5 Contrib. drain. area = 5.260 ac 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) Total Post-Dev to SWMB Hyd. No. 6 -- 10 Year Hyd No. 6 Hyd No. 4 Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 7 SWMB routing Hydrograph type = Reservoir Peak discharge = 13.26 cfs Storm frequency = 10 yrs Time to peak = 12.10 hrs Time interval = 2 min Hyd. volume = 63,983 cuft Inflow hyd. No. = 6 - Total Post-Dev to SWMB Max. Elevation = 777.06 ft Reservoir name = SWMB Max. Storage = 22,171 cuft Storage Indication method used. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) SWMB routing Hyd. No. 7 -- 10 Year Hyd No. 7 Hyd No. 6 Total storage used = 22,171 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 8 Post-Bypass Hydrograph type = SCS Runoff Peak discharge = 2.587 cfs Storm frequency = 10 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 5,242 cuft Drainage area = 0.670 ac Curve number = 81 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 Q (cfs) Time (hrs) Post-Bypass Hyd. No. 8 -- 10 Year Hyd No. 8 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 9 Total Post-Dev Discharge Hydrograph type = Combine Peak discharge = 13.87 cfs Storm frequency = 10 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 69,225 cuft Inflow hyds. = 7, 8 Contrib. drain. area = 0.670 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) Total Post-Dev Discharge Hyd. No. 9 -- 10 Year Hyd No. 9 Hyd No. 7 Hyd No. 8 Hydrograph Summary Report Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff 18.27 2 724 57,104 ------ ------ ------ Pre-Dev-onsite 2 SCS Runoff 2.479 2 716 5,121 ------ ------ ------ Pre-Dev-offsite 3 Combine 18.93 2 724 62,225 1, 2 ------ ------ Total Pre-Dev 4 SCS Runoff 2.599 2 716 5,424 ------ ------ ------ Post to SWMB - offsite 5 SCS Runoff 30.14 2 718 74,669 ------ ------ ------ Post to SWMB - onsite 6 Combine 32.66 2 718 80,092 4, 5 ------ ------ Total Post-Dev to SWMB 7 Reservoir 19.86 2 724 80,091 6 777.34 24,798 SWMB routing 8 SCS Runoff 3.413 2 716 6,968 ------ ------ ------ Post-Bypass 9 Combine 21.39 2 722 87,059 7, 8 ------ ------ Total Post-Dev Discharge SWM-03-05-26.gpw Return Period: 25 Year Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 1 Pre-Dev-onsite Hydrograph type = SCS Runoff Peak discharge = 18.27 cfs Storm frequency = 25 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 57,104 cuft Drainage area = 5.480 ac Curve number = 79 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 20.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 21.00 21.00 Q (cfs) Time (hrs) Pre-Dev-onsite Hyd. No. 1 -- 25 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 2 Pre-Dev-offsite Hydrograph type = SCS Runoff Peak discharge = 2.479 cfs Storm frequency = 25 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 5,121 cuft Drainage area = 0.450 ac Curve number = 84 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 Q (cfs) Time (hrs) Pre-Dev-offsite Hyd. No. 2 -- 25 Year Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 3 Total Pre-Dev Hydrograph type = Combine Peak discharge = 18.93 cfs Storm frequency = 25 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 62,225 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 5.930 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 21.00 21.00 Q (cfs) Time (hrs) Total Pre-Dev Hyd. No. 3 -- 25 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 4 Post to SWMB - offsite Hydrograph type = SCS Runoff Peak discharge = 2.599 cfs Storm frequency = 25 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 5,424 cuft Drainage area = 0.450 ac Curve number = 86 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 Q (cfs) Time (hrs) Post to SWMB - offsite Hyd. No. 4 -- 25 Year Hyd No. 4 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 5 Post to SWMB - onsite Hydrograph type = SCS Runoff Peak discharge = 30.14 cfs Storm frequency = 25 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 74,669 cuft Drainage area = 4.810 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) Post to SWMB - onsite Hyd. No. 5 -- 25 Year Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 6 Total Post-Dev to SWMB Hydrograph type = Combine Peak discharge = 32.66 cfs Storm frequency = 25 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 80,092 cuft Inflow hyds. = 4, 5 Contrib. drain. area = 5.260 ac 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) Total Post-Dev to SWMB Hyd. No. 6 -- 25 Year Hyd No. 6 Hyd No. 4 Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 7 SWMB routing Hydrograph type = Reservoir Peak discharge = 19.86 cfs Storm frequency = 25 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 80,091 cuft Inflow hyd. No. = 6 - Total Post-Dev to SWMB Max. Elevation = 777.34 ft Reservoir name = SWMB Max. Storage = 24,798 cuft Storage Indication method used. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) SWMB routing Hyd. No. 7 -- 25 Year Hyd No. 7 Hyd No. 6 Total storage used = 24,798 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 8 Post-Bypass Hydrograph type = SCS Runoff Peak discharge = 3.413 cfs Storm frequency = 25 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 6,968 cuft Drainage area = 0.670 ac Curve number = 81 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 Q (cfs) Time (hrs) Post-Bypass Hyd. No. 8 -- 25 Year Hyd No. 8 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 9 Total Post-Dev Discharge Hydrograph type = Combine Peak discharge = 21.39 cfs Storm frequency = 25 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 87,059 cuft Inflow hyds. = 7, 8 Contrib. drain. area = 0.670 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 Q (cfs) Time (hrs) Total Post-Dev Discharge Hyd. No. 9 -- 25 Year Hyd No. 9 Hyd No. 7 Hyd No. 8 Hydrograph Summary Report Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph No. type flow interval Peak volume hyd(s) elevation strge used Description (origin) (cfs) (min) (min) (cuft) (ft) (cuft) 1 SCS Runoff 26.85 2 724 84,304 ------ ------ ------ Pre-Dev-onsite 2 SCS Runoff 3.480 2 716 7,320 ------ ------ ------ Pre-Dev-offsite 3 Combine 27.77 2 724 91,624 1, 2 ------ ------ Total Pre-Dev 4 SCS Runoff 3.598 2 716 7,659 ------ ------ ------ Post to SWMB - offsite 5 SCS Runoff 40.10 2 718 101,186 ------ ------ ------ Post to SWMB - onsite 6 Combine 43.57 2 718 108,845 4, 5 ------ ------ Total Post-Dev to SWMB 7 Reservoir 29.72 2 724 108,843 6 777.94 30,615 SWMB routing 8 SCS Runoff 4.898 2 716 10,153 ------ ------ ------ Post-Bypass 9 Combine 31.74 2 722 118,996 7, 8 ------ ------ Total Post-Dev Discharge SWM-03-05-26.gpw Return Period: 100 Year Thursday, 03 / 5 / 2026 Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 1 Pre-Dev-onsite Hydrograph type = SCS Runoff Peak discharge = 26.85 cfs Storm frequency = 100 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 84,304 cuft Drainage area = 5.480 ac Curve number = 79 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 20.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) Pre-Dev-onsite Hyd. No. 1 -- 100 Year Hyd No. 1 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 2 Pre-Dev-offsite Hydrograph type = SCS Runoff Peak discharge = 3.480 cfs Storm frequency = 100 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 7,320 cuft Drainage area = 0.450 ac Curve number = 84 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 Q (cfs) Time (hrs) Pre-Dev-offsite Hyd. No. 2 -- 100 Year Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 3 Total Pre-Dev Hydrograph type = Combine Peak discharge = 27.77 cfs Storm frequency = 100 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 91,624 cuft Inflow hyds. = 1, 2 Contrib. drain. area = 5.930 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) Total Pre-Dev Hyd. No. 3 -- 100 Year Hyd No. 3 Hyd No. 1 Hyd No. 2 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 4 Post to SWMB - offsite Hydrograph type = SCS Runoff Peak discharge = 3.598 cfs Storm frequency = 100 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 7,659 cuft Drainage area = 0.450 ac Curve number = 86 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 Q (cfs) Time (hrs) Post to SWMB - offsite Hyd. No. 4 -- 100 Year Hyd No. 4 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 5 Post to SWMB - onsite Hydrograph type = SCS Runoff Peak discharge = 40.10 cfs Storm frequency = 100 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 101,186 cuft Drainage area = 4.810 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 8.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 10.00 10.00 20.00 20.00 30.00 30.00 40.00 40.00 50.00 50.00 Q (cfs) Time (hrs) Post to SWMB - onsite Hyd. No. 5 -- 100 Year Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 6 Total Post-Dev to SWMB Hydrograph type = Combine Peak discharge = 43.57 cfs Storm frequency = 100 yrs Time to peak = 11.97 hrs Time interval = 2 min Hyd. volume = 108,845 cuft Inflow hyds. = 4, 5 Contrib. drain. area = 5.260 ac 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 10.00 10.00 20.00 20.00 30.00 30.00 40.00 40.00 50.00 50.00 Q (cfs) Time (hrs) Total Post-Dev to SWMB Hyd. No. 6 -- 100 Year Hyd No. 6 Hyd No. 4 Hyd No. 5 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 7 SWMB routing Hydrograph type = Reservoir Peak discharge = 29.72 cfs Storm frequency = 100 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 108,843 cuft Inflow hyd. No. = 6 - Total Post-Dev to SWMB Max. Elevation = 777.94 ft Reservoir name = SWMB Max. Storage = 30,615 cuft Storage Indication method used. 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 10.00 10.00 20.00 20.00 30.00 30.00 40.00 40.00 50.00 50.00 Q (cfs) Time (hrs) SWMB routing Hyd. No. 7 -- 100 Year Hyd No. 7 Hyd No. 6 Total storage used = 30,615 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 8 Post-Bypass Hydrograph type = SCS Runoff Peak discharge = 4.898 cfs Storm frequency = 100 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 10,153 cuft Drainage area = 0.670 ac Curve number = 81 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 1.00 1.00 2.00 2.00 3.00 3.00 4.00 4.00 5.00 5.00 Q (cfs) Time (hrs) Post-Bypass Hyd. No. 8 -- 100 Year Hyd No. 8 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 9 Total Post-Dev Discharge Hydrograph type = Combine Peak discharge = 31.74 cfs Storm frequency = 100 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 118,996 cuft Inflow hyds. = 7, 8 Contrib. drain. area = 0.670 ac 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) Total Post-Dev Discharge Hyd. No. 9 -- 100 Year Hyd No. 9 Hyd No. 7 Hyd No. 8 Hydraflow Rainfall Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Return Intensity-Duration-Frequency Equation Coefficients (FHA) Period (Yrs) B D E (N/A) 1 0.0000 0.0000 0.0000 -------- 2 44.3500 9.5000 0.8400 -------- 3 0.0000 0.0000 0.0000 -------- 5 45.4100 8.5000 0.7900 -------- 10 43.3300 7.7500 0.7500 -------- 25 37.0200 5.7500 0.6700 -------- 50 35.1900 4.7500 0.6300 -------- 100 33.8100 3.7500 0.5900 -------- File name: Frederick County.IDF Intensity = B / (Tc + D)^E Return Intensity Values (in/hr) Period (Yrs)5 min1015202530354045505560 1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2 4.69 3.66 3.02 2.58 2.27 2.02 1.83 1.67 1.54 1.43 1.34 1.26 3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5 5.81 4.53 3.75 3.22 2.83 2.54 2.31 2.12 1.96 1.82 1.71 1.61 10 6.42 5.01 4.16 3.58 3.17 2.85 2.59 2.39 2.21 2.07 1.94 1.83 25 7.54 5.84 4.85 4.20 3.73 3.37 3.09 2.86 2.67 2.50 2.36 2.24 50 8.38 6.46 5.37 4.66 4.15 3.76 3.46 3.21 3.00 2.83 2.68 2.54 100 9.40 7.20 6.00 5.22 4.66 4.24 3.91 3.64 3.41 3.22 3.06 2.91 Tc = time in minutes. Values may exceed 60. Rainfall Precipitation Table (in) Precip. file name: D:\Projects\2025\25-11 Shady Elm storage\Calculations\Shady Elm.pcp Storm Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr SCS 24-hour 2.40 2.89 0.00 3.95 4.21 5.08 6.30 6.62 SCS 6-Hr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-1st 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Custom 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 STORM SEWER & CHANNEL CALCULATIONS SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 STR ID AREA (AC.) WEIGHTED 'C' 2-YR. RUNOFF (CFS) 10-YR. RUNOFF (CFS) 2 0.27 0.85 1.07 1.47 3 1.08 0.60 3.02 4.13 7 0.06 0.20 0.06 0.08 8 0.92 0.68 2.93 4.01 9 0.35 0.84 1.38 1.89 10 0.35 0.86 1.41 1.93 15 0.06 0.20 0.06 0.08 17 0.69 0.62 1.99 2.73 RD1 0.02 0.90 0.08 0.12 RD2 0.05 0.90 0.21 0.29 RD3 0.05 0.90 0.21 0.29 RD4 0.05 0.90 0.14 0.19 RD5 0.05 0.90 0.21 0.29 RD6 0.05 0.90 0.21 0.29 RD7 0.02 0.90 0.08 0.12 RD8 0.02 0.90 0.08 0.12 RD9 0.05 0.90 0.21 0.29 RD10 0.05 0.90 0.21 0.29 RD11 0.05 0.90 0.21 0.29 RD12 0.05 0.90 0.21 0.29 RD13 0.05 0.90 0.15 0.21 RD14 0.02 0.90 0.08 0.12 RD15 0.02 0.90 0.08 0.12 RD16 0.05 0.90 0.21 0.29 RD17 0.05 0.90 0.21 0.29 RD18 0.05 0.90 0.21 0.29 RD19 0.05 0.90 0.21 0.29 RD20 0.05 0.90 0.14 0.19 RD21 0.02 0.90 0.05 0.07 RD22 0.02 0.90 0.08 0.12 RD23 0.05 0.90 0.21 0.29 RD24 0.05 0.90 0.21 0.29 RD25 0.05 0.90 0.21 0.29 RD26 0.05 0.90 0.21 0.29 RD27 0.05 0.90 0.21 0.29 RD28 0.02 0.90 0.08 0.12 STORM SEWER STRUCTURE DRAINAGE TABLE E&SC AND MISCELLANEOUS CALCULATIONS SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 STRUCTURE ID 10-YR. RUNOFF (CFS) 10-YR. VELOCITY (FT/S) DIA. (IN.) LENGTH, L (FT.) WIDTH, W (FT.) D50 (IN.) RIPRAP DEPTH, d (IN.) 1 20.35 7.47 24 14 16 6 12 16 2.73 4.15 15 8106 12 SWMB 13.26 7.50 18 10 12 6 12 OUTLET PROTECTION TABLE SEDIMENT BASIN CALCULATIONS: Project: Shady Elm Contractor Storage Basin #: Sediment Basin (Future SWMB) Location: Frederick Co., VA Drainage Area: 5.30 acres Wet Storage: Required volume = 1809 ft3 x drainage area = 1809 x 5.30 acres = 9588 ft3 From stage/storage curve, get 9588 ft3 at elevation = Cleanout volume = 900 ft3 x drainage area =ft3 From stage/storage curve, cleanout elevation = Dry Storage: Required volume = 1809 ft3 x drainage area = 1809 x 5.30 acres = 9588 ft3 From stage/storage curve, get 9588 ft3 at elevation = Dewatering Orifice: Driving head = 1.25 Flowrate for 24-hour drawdown = 0.22 cfs Orifice area = 0.041 ft2 Orifice dia. = 2.8 in. use 3 in. Diameter of flexible tubing = 6 in. Basin Shape: Flow length = 200 ft Effective Width = 25 ft Length/Width = 8.0 therefore baffles are not required Anti-Seep Collar: Depth of water at principal spillway crest = 4.65 ft Slope of upstream face of embankment = 2 : 1 Slope of principal spillway barrel = 0.5 % Length of barrel in saturated zone = 26 ft Number of collars required = 1 (5.5' x 5.5') Final Design Elevations: Top of embankment = 779.50 Emergency spillway crest = 777.65 Principal spillway crest = 776.65 Dewatering elevation = 775.00 Cleanout elevation = 774.00 Bottom of wet storage = 772.00 777.2025-Year design storm elevation = 4770 774.00 775.00 776.25 NOTE: Since the sediment trap riser will also be used as the permanent SWM riser, the actual elevation of the top of the riser will be set based on the final configuration to avoid later modification. In this case, the top of riser will be set at 776.65, which is 0.40' higher than the computed dry storage elevation. Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 11 DA to DD Hydrograph type = SCS Runoff Peak discharge = 7.796 cfs Storm frequency = 10 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 17,015 cuft Drainage area = 1.460 ac Curve number = 93 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 Q (cfs) Time (hrs) DA to DD Hyd. No. 11 -- 10 Year Hyd No. 11 Pond Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Pond No. 2 - SB Pond Data Contours -User-defined contour areas. Conic method used for volume calculation. Begining Elevation = 772.00 ft Stage / Storage Table Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cuft) 0.00 772.00 00 0 0 1.00 773.00 1,500 500 500 2.00 774.00 3,250 2,319 2,819 3.00 775.00 6,825 4,928 7,747 4.00 776.00 12,100 9,337 17,083 5.00 777.00 17,400 14,669 31,752 6.00 778.00 24,950 21,060 52,812 7.00 779.00 37,150 30,845 83,657 7.50 779.50 40,700 19,454 103,111 Culvert / Orifice Structures Weir Structures [A] [B] [C] [PrfRsr] [A] [B] [C] [D] Rise (in)= 18.00 3.00 0.00 0.00 Span (in)= 18.00 3.00 0.00 0.00 No. Barrels = 1 110 Invert El. (ft)= 772.00 775.00 0.00 0.00 Length (ft)= 50.00 0.00 0.00 0.00 Slope (%)= 0.50 0.00 0.00 n/a N-Value = .012 .013 .013 n/a Orifice Coeff.= 0.60 0.60 0.60 0.60 Multi-Stage = n/a NoNoNo Crest Len (ft)= 12.57 20.00 0.00 0.00 Crest El. (ft)= 776.65 777.65 0.00 0.00 Weir Coeff.= 3.33 2.60 3.33 3.33 Weir Type = 1 Broad --- --- Multi-Stage = Yes NoNoNo Exfil.(in/hr)= 0.000 (by Contour) TW Elev. (ft)= 0.00 Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s). 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 Stage (ft) 0.00 772.00 2.00 774.00 4.00 776.00 6.00 778.00 8.00 780.00 Elev (ft) Discharge (cfs) Stage / Discharge Total Q Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 12 DA to SB Hydrograph type = SCS Runoff Peak discharge = 13.35 cfs Storm frequency = 1 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 27,410 cuft Drainage area = 5.300 ac Curve number = 91 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.40 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) DA to SB Hyd. No. 12 -- 1 Year Hyd No. 12 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 13 SB Routing Hydrograph type = Reservoir Peak discharge = 0.240 cfs Storm frequency = 1 yrs Time to peak = 16.23 hrs Time interval = 2 min Hyd. volume = 19,616 cuft Inflow hyd. No. = 12 - DA to SB Max. Elevation = 776.16 ft Reservoir name = SB Max. Storage = 19,371 cuft Storage Indication method used. 0 8 16 24 32 40 48 56 64 72 80 Q (cfs) 0.00 0.00 2.00 2.00 4.00 4.00 6.00 6.00 8.00 8.00 10.00 10.00 12.00 12.00 14.00 14.00 Q (cfs) Time (hrs) SB Routing Hyd. No. 13 -- 1 Year Hyd No. 13 Hyd No. 12 Total storage used = 19,371 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 12 DA to SB Hydrograph type = SCS Runoff Peak discharge = 17.09 cfs Storm frequency = 2 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 35,512 cuft Drainage area = 5.300 ac Curve number = 91 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 2.89 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 Q (cfs) Time (hrs) DA to SB Hyd. No. 12 -- 2 Year Hyd No. 12 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 13 SB Routing Hydrograph type = Reservoir Peak discharge = 0.286 cfs Storm frequency = 2 yrs Time to peak = 16.63 hrs Time interval = 2 min Hyd. volume = 27,718 cuft Inflow hyd. No. = 12 - DA to SB Max. Elevation = 776.58 ft Reservoir name = SB Max. Storage = 25,663 cuft Storage Indication method used. 0 8 16 24 32 40 48 56 64 72 80 Q (cfs) 0.00 0.00 3.00 3.00 6.00 6.00 9.00 9.00 12.00 12.00 15.00 15.00 18.00 18.00 Q (cfs) Time (hrs) SB Routing Hyd. No. 13 -- 2 Year Hyd No. 13 Hyd No. 12 Total storage used = 25,663 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 12 DA to SB Hydrograph type = SCS Runoff Peak discharge = 27.18 cfs Storm frequency = 10 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 58,056 cuft Drainage area = 5.300 ac Curve number = 91 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 4.21 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) DA to SB Hyd. No. 12 -- 10 Year Hyd No. 12 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 13 SB Routing Hydrograph type = Reservoir Peak discharge = 8.122 cfs Storm frequency = 10 yrs Time to peak = 12.07 hrs Time interval = 2 min Hyd. volume = 50,261 cuft Inflow hyd. No. = 12 - DA to SB Max. Elevation = 776.97 ft Reservoir name = SB Max. Storage = 31,383 cuft Storage Indication method used. 0 4 8 12 16 20 24 28 32 36 40 44 48 Q (cfs) 0.00 0.00 4.00 4.00 8.00 8.00 12.00 12.00 16.00 16.00 20.00 20.00 24.00 24.00 28.00 28.00 Q (cfs) Time (hrs) SB Routing Hyd. No. 13 -- 10 Year Hyd No. 13 Hyd No. 12 Total storage used = 31,383 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 12 DA to SB Hydrograph type = SCS Runoff Peak discharge = 33.78 cfs Storm frequency = 25 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 73,225 cuft Drainage area = 5.300 ac Curve number = 91 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 5.08 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) DA to SB Hyd. No. 12 -- 25 Year Hyd No. 12 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 13 SB Routing Hydrograph type = Reservoir Peak discharge = 17.20 cfs Storm frequency = 25 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 65,431 cuft Inflow hyd. No. = 12 - DA to SB Max. Elevation = 777.20 ft Reservoir name = SB Max. Storage = 35,943 cuft Storage Indication method used. 0 4 8 12 16 20 24 28 32 36 40 Q (cfs) 0.00 0.00 5.00 5.00 10.00 10.00 15.00 15.00 20.00 20.00 25.00 25.00 30.00 30.00 35.00 35.00 Q (cfs) Time (hrs) SB Routing Hyd. No. 13 -- 25 Year Hyd No. 13 Hyd No. 12 Total storage used = 35,943 cuft Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 12 DA to SB Hydrograph type = SCS Runoff Peak discharge = 45.36 cfs Storm frequency = 100 yrs Time to peak = 11.93 hrs Time interval = 2 min Hyd. volume = 100,377 cuft Drainage area = 5.300 ac Curve number = 91 Basin Slope = 0.0 % Hydraulic length = 0 ft Tc method = User Time of conc. (Tc) = 5.00 min Total precip. = 6.62 in Distribution = Type II Storm duration = 24 hrs Shape factor = 484 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 Q (cfs) 0.00 0.00 10.00 10.00 20.00 20.00 30.00 30.00 40.00 40.00 50.00 50.00 Q (cfs) Time (hrs) DA to SB Hyd. No. 12 -- 100 Year Hyd No. 12 Hydrograph Report Hydraflow Hydrographs Extension for Autodesk® Civil 3D® by Autodesk, Inc. v2025 Thursday, 03 / 5 / 2026 Hyd. No. 13 SB Routing Hydrograph type = Reservoir Peak discharge = 19.35 cfs Storm frequency = 100 yrs Time to peak = 12.03 hrs Time interval = 2 min Hyd. volume = 92,583 cuft Inflow hyd. No. = 12 - DA to SB Max. Elevation = 777.65 ft Reservoir name = SB Max. Storage = 45,496 cuft Storage Indication method used. 0 4 8 12 16 20 24 28 32 36 40 Q (cfs) 0.00 0.00 10.00 10.00 20.00 20.00 30.00 30.00 40.00 40.00 50.00 50.00 Q (cfs) Time (hrs) SB Routing Hyd. No. 13 -- 100 Year Hyd No. 13 Hyd No. 12 Total storage used = 45,496 cuft NRCS SOILS REPORT SHADY ELM CONTRACTOR STORAGE Frederick County, Virginia (25-11) March 5, 2026 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 Frederick County, VirginiaNatural Resources Conservation Service November 21, 2025 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 Frederick County, Virginia...............................................................................13 5B—Carbo silt loam, 2 to 7 percent slopes.................................................13 6C—Carbo-Oaklet, very rocky silt loams, 2 to 15 percent slopes...............14 References............................................................................................................16 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 43344704334510433455043345904334630433467043347104334470433451043345504334590433463043346704334710741500 741540 741580 741620 741660 741700 741740 741780 741820 741860 741900 741500 741540 741580 741620 741660 741700 741740 741780 741820 741860 741900 39° 7' 41'' N 78° 12' 22'' W39° 7' 41'' N78° 12' 5'' W39° 7' 32'' N 78° 12' 22'' W39° 7' 32'' N 78° 12' 5'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 17N WGS84 0 50 100 200 300 Feet 0 25 50 100 150 Meters Map Scale: 1:1,920 if printed on A landscape (11" x 8.5") 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 1:15,800. 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: Frederick County, Virginia Survey Area Data: Version 20, Sep 5, 2025 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 2, 2023—Oct 4, 2023 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 5B Carbo silt loam, 2 to 7 percent slopes 1.9 28.1% 6C Carbo-Oaklet, very rocky silt loams, 2 to 15 percent slopes 4.7 71.9% Totals for Area of Interest 6.6 100.0% 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. 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, Custom Soil Resource Report 11 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 Frederick County, Virginia 5B—Carbo silt loam, 2 to 7 percent slopes Map Unit Setting National map unit symbol: kh8r Elevation: 900 to 2,600 feet Mean annual precipitation: 36 to 50 inches Mean annual air temperature: 52 to 55 degrees F Frost-free period: 160 to 190 days Farmland classification: All areas are prime farmland Map Unit Composition Carbo and similar soils:85 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Carbo Setting Landform:Hills Landform position (two-dimensional):Summit Landform position (three-dimensional):Interfluve Down-slope shape:Linear Across-slope shape:Linear Parent material:Residuum weathered from limestone Typical profile H1 - 0 to 9 inches: silt loam H2 - 9 to 26 inches: clay H3 - 26 to 36 inches: bedrock Properties and qualities Slope:2 to 7 percent Depth to restrictive feature:20 to 40 inches to lithic bedrock Drainage class:Well drained Runoff class: Very high Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.5 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 2e Hydrologic Soil Group: D Ecological site: F147XY003PA - Mixed Limestone Upland Hydric soil rating: No Custom Soil Resource Report 13 6C—Carbo-Oaklet, very rocky silt loams, 2 to 15 percent slopes Map Unit Setting National map unit symbol: kh8t Elevation: 500 to 2,600 feet Mean annual precipitation: 36 to 50 inches Mean annual air temperature: 52 to 55 degrees F Frost-free period: 160 to 190 days Farmland classification: Farmland of statewide importance Map Unit Composition Carbo and similar soils:50 percent Oaklet and similar soils:45 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Carbo Setting Landform:Hills Landform position (two-dimensional):Summit Landform position (three-dimensional):Interfluve Down-slope shape:Convex Across-slope shape:Convex Parent material:Residuum weathered from limestone Typical profile H1 - 0 to 9 inches: silt loam H2 - 9 to 26 inches: clay H3 - 26 to 36 inches: bedrock Properties and qualities Slope:2 to 15 percent Depth to restrictive feature:20 to 40 inches to lithic bedrock Drainage class:Well drained Runoff class: Very high Capacity of the most limiting layer to transmit water (Ksat):Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Low (about 4.5 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: D Ecological site: F147XY003PA - Mixed Limestone Upland Hydric soil rating: No Custom Soil Resource Report 14 Description of Oaklet Setting Landform:Hills Landform position (two-dimensional):Summit Landform position (three-dimensional):Interfluve Down-slope shape:Convex Across-slope shape:Convex Parent material:Residuum weathered from limestone Typical profile H1 - 0 to 5 inches: silt loam H2 - 5 to 11 inches: silt loam H3 - 11 to 31 inches: clay H4 - 31 to 63 inches: clay Properties and qualities Slope:2 to 15 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Runoff class: High Capacity of the most limiting layer to transmit water (Ksat):Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Available water supply, 0 to 60 inches: Moderate (about 7.7 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 4e Hydrologic Soil Group: C Ecological site: F147XY003PA - Mixed Limestone Upland Hydric soil rating: No Custom Soil Resource Report 15 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 16 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 17