CHOH 206(1) 913(1) culvert report_revised per mde 062322 comments.pdf

CULVERT DESIGN COMPUTATIONS FOR PROPOSED 18” CMP AT STA 101+78.12

DATE: January 21, 2022

PROJECT NAME: CHESAPEAKE AND OHIO CANAL NATIONAL HISTORICAL PARK

FHWA PROJECT NUMBER: NP CHOH 206(1) 913(1) ETC

PURPOSE: Provide hydrologic justification for subject culvert sizing and outfall design as requested by

MDE

Revised: July 20, 2022 to address 1st Submittal June 23, 2022 MDE comments, numbers 12-15.

Hydrology summary, assumptions, design criteria, and justification

• Rational method hydrology (Q=cia). NRCS TR-55 100-year analysis added to address Embankment Code 378 evaluation.

• 25-year design return period.

• The hydrology was updated based on NRCS TR-55.

• Stone ballast and the aggregate tow path surface, assumed to be impervious in the rational method analysis for conservativeness, were taken as “Gravel” cover in the TR-55 analysis as it is appropriate and an available cover option.

• The time of concentration (Tc) value computed in the rational method analysis was carried forward to the TR-55 analysis. The TR-55 based 100-year discharge was computed to be 25.4 cfs.

• An updated FHWA HY-8 (ver 7.50) model was generated with the 100-year discharge and computed a 100-year headwater elevation of 238.85, resulting in a headwater depth of 9.46 feet (100-yr HW – culvert inv in (229.39).

• The embankment height was computationally raised to prevent any overtopping flow and thus maximize the 100-year headwater elevation solely due to the culvert capacity.

• Since the culvert and outfall profile are supercritical (significantly), there are no tailwater effects on the headwater.

• Since the effective headwater depth is less than 10.0 feet, according to MDE Stormwater, Dam Safety, and Flood Management Program Flow Chart for Determining Embankment Design Category and Approval Authority, the tow path and culvert configuration are not classified as an embankment and are thus not subject to any further dam hazard classification, and only subject to MDW SWM culvert review.

• Extreme caution was exercised in proposing any upsized culvert. It is important from an environmental standpoint that the current magnitude and frequency of inundation (hydrology) be maintained within the existing canal prism.

• All other hydrologic analyses and design outside of the 378 embankment evaluation are based on the previously submitted rational method hydrology.

• Rational method computations performed using FHWA Hydraulic Toolbox ® version 4.4 software.

• Rainfall data taken from latest NOAA Atlas 14 dataset at project location. Intensity for 25-year event = 5.12 inches/hr for the computed time of concentration (Tc) of 13.68 minutes.

• Atlas 14 rainfall precipitation is based on current geographically located NOAA Atlas 14 data.

FHWA Hydraulic Toolbox ® (ver 4.4) computationally fits and computes return period dependent coefficients to the standard IDF equation based on NOAA Atlas 14 rainfall intensities and/or depth data. The resulting IDF equation for the 25-year event is i = 33.98/(Tc + 5.969)^0.6353.

• Drainage area delineated using LIDAR mapping with supplemental field shots taken at critical topological elements, in combination with field recon to evaluate existing drainage structure-driven drain divides. The east DA boundary was located outside the mapping area, so it was evaluated via field recon. The total DA was evaluated to be 4.00 acres.

1. FHWA-EFL and NPS project staff decided that expending additional limited resources and time on generating new mapping to cover the east portion of the drainage area was not necessary given the shape and nature of the drainage area.

2. Given the uniform nature of the drainage area, located between 2 prismatic, linear and parallel features, i.e., the railroad embankment and the tow path, coupled with site visits and visual inspection of the drainage divides, the east areas of the drainage area outside of the available mapping area was evaluated within the bounds of acceptable accuracy for the hydrology of an 18-inch culvert.

3. The east lateral drainage divide and adjacent DA area was indicated by visual inspection of a prominent ridge co-located with an existing corrugated metal riser structure with concentric anti-vortex device and outfall pipe that either effectively blocks or diverts any westward moving flow to the proposed culvert. Digital chain-ties using Google Earth were then used to project the location of the east lateral divide onto the digital project LiDAR base mapping.

• The Tc flowpath was chosen based on 3 points:

1. It is located within the mapped limits of the drainage area.

2. Flow paths of long, narrowly shaped, and extremely flat drainage areas introduce significant runoff underestimation error. In this case, the longest flow path is not particularly representative of the hydrology.

3. Truncation of the flow path reduces the time of concentration, resulting in increased rainfall intensities, providing additional conservativeness in the discharge estimates.

• Actual cover includes gravel pavement and railroad stone ballast (c=0.90), open space (c=0.35), and woods (c=0.20). For conservative reasons, cover assumed to be only impervious (c=0.90) and open space (c=0.35), resulting in a weighted C = 0.44.

• 25-year design discharge computed to be 9.1 cfs.

• Drainage area is extremely flat, as evidenced by LIDAR topo and ponding areas observed in the field. It is unlikely that the full design discharge is conveyed to the culvert.

Hydraulic summary, assumptions, design criteria, and justification

• Hydraulic computations performed using the industry standard FHWA HY-8 version 7.50 software.

• FHWA design criteria: HW/D <= 1.50. Actual HW/D = [(231.39-229.39)/1.5] = 1.33 => ok

• The entrance loss conditions assumed are consistent with standard end section (Ke for headwall).

• The culvert material was changed to RCP for better durability, with a standard end section at the entrance and a headwall at the outlet.

• The outlet conditions were taken as a trapezoidal outfall channel per the outlet channel analysis and confirmed to be supercritical due to the steepness of the slope.

• The culvert and outfall channel are significantly supercritical (inlet control) due to steep slopes, thus the channel has no impact on the tailwater condition of the culvert.

• The proposed culvert maintains approximate current horizontal alignment and size (18”) and maintains historic barrel slope of approximately 6.0% so current hydrology is not impacted. This reduces the slope from the current 13%, which was a previous MDE comment.

1. Manning’s n values are hydraulically irrelevant from a capacity standpoint due to the supercritical slope of the culvert.

2. Standard design practice when hydraulic profile regimes are unknown, in the event of a sub-critical profile, a higher manning’s n value assumed in the hydraulic evaluation justifies design to allow more construction flexibility in pipe material choices should material shortages be experienced during construction. Thus, the more conservative Manning’s n value was carried forward for the super-critically sloped 18” RCP. However, per MDE comments, the analysis was modified for a Manning’s n value of 0.013, which is consistent with the proposed concrete pipe material shown on the plans.

• The steepness of the proposed outfall channel is fixed, governed by the proposed culvert outlet invert, and the existing ground elevation at the receiving stream. The culvert outlet invert is governed by the fixed culvert entrance invert elevation and maintaining the historic barrel slope of 6% to prevent impacts to the hydrology of the canal.

• Holding the current entrance invert elevation while maintaining a 6%-barrel slope results in a fill condition for the outfall channel, requiring that the riprap in the channel to be supported by granular fill material. The channel is then vertically tapered to existing ground around the horizontal bend.

• Use of the rock outlet protection procedures of MDE’s Standards and Specifications for Soil Erosion and Sediment Control manual (2011), Section D-4, page D.13 – D.22, in particular page D.18 nomograph for minimum tailwater conditions, would require extrapolation of the velocity and flow depth curves, which is neither advisable nor acceptable per the note “Note: Do not extrapolate length of curves” shown on D.18.

• EFL performed outlet channel and lining design utilizing the roadway industry standard FHWA Hydraulic Toolbox ® 4.4 software. The software is Manning’s based, varying n values iteratively with computed flow depth, and iteratively analyzes a variety of lining types for permissible shear. For a given channel section, slope, and design discharge, the software accounts for applicable variables, including Manning’s n value, D50 size, side slopes, specific weight of rock, and superelevation of flow in horizontal bends.

• However, due to the steepness of the outfall channel (34.85 %), hydraulic energy conservation and normal Manning’s flow considerations, the associated Manning’s flow computations break down when any channel slope exceeds 10% because the energy assumption of normal and hydrostatic flow depth equality is no longer valid. This impacts Manning’s-based flow depth, velocity, and shear computations. Additional levels of conservativeness, in the channel section, lining, hydrology, and riprap size are proposed to address these hydraulic uncertainties. In addition, 3-D reinforced turf matting (EFL designation RECP TRM (5.B) which is Enkamat ® or equal) is proposed outside of the outfall channel bend, outside of the channel in case superelevated flow manages to climb the 2 ft high channel side slope and spill over into unprotected ground, and to stabilized outfall channel fill berm.

• Culvert site and outfall area composed of NRCS soil symbol LsA soils (Lindside silt loam, 0 to 3 percent slopes). LsA at a depth of 0”- 13” is a cohesive silty loam (CL-ML, CL, ML), with a representative PI of 9. However, field recon and visual inspection of the existing outfall channel below the toe of embankment fill indicated solid weathered rock, bedrock, or very large boulders lining the channel with vegetative overgrowth. Other than the blowout at the existing culvert outfall within the fill section of the embankment, there was no scour noted in the outfall channel.

1. The NRCS soil survey map and report were downloaded from the NRCS Web Soil Survey website, and is provided in the appendix of the updated report. The entire culvert drainage area is enveloped by 100% Lindside silt loam (LsA, 0-3% slope, HSG C).

• The stable condition of the outfall channel just downstream of the culvert outfall blowout at the toe of embankment indicate no channel protection is necessary. However, because the proposed outfall channel is in a fill condition and the channel must be protected where the proposed culvert daylights mid-slope, the riprap is simply extended beyond the embankment toe for fill purposes, extended thru the 10’ radius horizontal bend, and tied-out to existing grade. Riprap protection beyond the toe of fill is not necessary for scour protection purposes.

Appendices

• Culvert Plan

• Culvert Profile

• Culvert Drainage Area

• Rational Method Hydrology Worksheet

• FHWA Hydraulic Toolbox Hydrology Output (Rational Method 25-Year Q)

• FHWA HY-8 Analysis (Rational Method 25-Year Q)

• NRCS TR-55 Analysis

• FHWA HY-8 Analysis (TR-55 100-Year Q)

• NOAA Altas 14 Rainfall Data

• Soil Survey Report

.0

P O

E

R

C P

TYPICAL

CONTOUR,

PROPOSED

CHANNEL

OUTFALL

RIPRAP

TYPE 5.B

RECP TRM

FOR LENGTH)

(MODIFIED

HEADWALL

END SECTION

STANDARD

101+78.12

0 10 20 30 40 50 60 70 80 90

190 190

200 200

210 210

220 220

230 230

240 240

250 250

260 260

1.

5:

2:1

WITH W/ GEOTEXTILE

CL. 4 RIPRAP D50 = 15", 30" THICK

2' DEEP, 4' BOTTOM, 2:1 SS W/

TRAPEZOIDAL OUTFALL CHANNEL

.85

FILL

GRANULAR

S T

A

.1

P G

L E

L

.2

END SECION

STD. CONC.

INV 229.39

INV 227.36 34.0 LF 18" R

CP @ 6.0%

2:1 MAX SLOPE.

AND TIE INTO ADJACENT GRADES.

TO DAYLIGHT CULVERT ENTRANCE

ADJUST GRADE AS NECESSARY

EX. GROUND

PROPOSED GRADE

TYPICAL SECTION

OUTFALL CHANNEL

FILL, TYPICAL

EMBANKMENT

FILL, TYPICAL

GRANULAR

CL 4 RIPRAP

TYPE 5.B

RECP TRM

CULVERT PROFILE

25-YR WSE = 231.39

25-YR Q = 9.1 CFS

D 2 5-Y

R = 0.

FT

V 2 5-Y

R = .10

FP

S

REMOVE EXISTING 18" CMP

L = 12', TOW = 229.86

MODIFIED FOR LENGTH

STD DET ET601-4

NOTE: CULVERT LENGTH SHOWN INCLUDES END SECTION AND HEADWALL

2:1 2:1

2:

EXISTING GROUND

GRADE

PROPOSED

OUTLET V25 = 8.06

FPS

100-YR WSE = 238.85 (TR-55)

100-YR Q = 25.4 CFS (TR-55)

0-Y

R T W

= 0 .34

20'10'0

Scale in Feet

.4'

12'

4'

2'

.0

P O

E

R

C P

TYPICAL

CONTOUR,

PROPOSED

CHANNEL

OUTFALL

RIPRAP

TYPE 5.B

RECP TRM

FOR LENGTH)

(MODIFIED

HEADWALL

END SECTION

STANDARD

DRAIN

AGE A

REA

FLO

WLIN

E

200'100'0

Scale in Feet

N

DRAINAGE AREA

FIELD DETERMINED

DRAINAGE AREA

FIELD DETERMINED

DRAINAGE AREA MAP

(Entire DA)

HSG = C

Soil Name LsA

TC = 13.68 MINS = 0.228 HRS

IMPERVIOUS AREA = 0.00 ACRES

CN = 75

DA = 4.00 ACRES

DRAINAGE AREA DATA

1" = 100'

RATIONAL METHOD HYDROLOGY WORKSHEET

PROJECT:

LOCATION: CULVERT 101+78.12

DATE:

CONDITION: EXISTING PROPOSED

COMPUTED: BLM

C VALUE 0.90 0.20 0.35

CULVERT 101+78.36 0.6400 0.0000 3.3600 4.0000 0.4380

SHEET FLOW

A RR BALLAST 0.024 2.98 246.40 246.00 28.0 0.0143 498.0 0.968

SUM Tt (MIN): 0.968

B FORRESTED (THIN COVER) 0.076 97 246.00 229.50 0.170 1.03 1.563

SUM Tt (MIN): 1.563

SEGMENT ID Q (CFS) MANNING'S n

L FLOW LENGTH

(FT)

US ELEV DS ELEV S SLOPE (FT/FT) Q (solver check) TRAVEL TIME (MIN)

C 9.10 0.06 525 229.50 229.00 0.0010 0.78 9.10 11.149

SUM Tt (MIN): 11.149

FLOW DEPTH (FT) BOTTOM WIDTH (FT) SIDE SLOPES (H:1) Af FLOW AREA (SF) Wp (FT) Rh = Af/Wp (FT)

1.61 4.00 2.0 11.59 11.19 1.04

Tc (MIN) 13.680

S SLOPE (FT/FT) Tt (MIN)

CONCENTRATED FLOW (CHANNEL)

CHANNEL GEOMETRY

SEGMENT ID SURFACE TYPE

k (HDS-2 TABLE 2.2)

L FLOW LENGTH

(FT)

US ELEV DS ELEV

L FLOW LENGTH (FT) S SLOPE (FT/FT)

LMAX MAX FLOW

LENGTH (FT)

Tt= 0.42·(n·L)0.8/(P2

0.5 · S0.4)

SHALLOW CONCENTRATED FLOW

SEGMENT ID SURFACE MANNING'S n P2 (2-YR) (IN) US ELEV DS ELEV

CHOH 206(1) 913(1)

STRUCTURE IMPERVIOUS (ac) WOODS (ac) OPEN SPACE (ac) TOTAL a (ac) C (weighted)

𝐕𝐕 = 𝟑𝟑𝟑𝟑 · 𝐤𝐤 · 𝐬𝐬𝟎𝟎. 𝟓𝟓

𝐕𝐕 = [1.49·Rh 2/3· 𝐒𝐒1/2]/n

Hydraulic Analysis Report Project Data

Project Title:

Designer:

Project Date: Wednesday, November 17, 2021 Project Units: U.S. Customary Units Notes:

Rational Analysis: culvert sta 101+78.12 Notes:

Rational Method Input Parameters Runoff Coefficient: 0.44 Basin Area: 4.0000 acres Rainfall Intensity: 5.12 in/hr Time of Concentration: 13.70 minutes Recurrence Year: 25 year

Rational Method Results Flowrate: 9.1 cfs

IDF Input Parameters User Supplied Data

IDF Results 25 year IDF equation: i = 33.9774 / (Tc + 5.96914)^0.635266 Intensity: 5.1198 in/hr

Time of Concentration Input Parameters Minimum Time of Concentration: 5.00 min Computed Time of Concentration Time of Concentration: 13.70 min

Sheet Flow Input Parameters Top Elevation: 246.40 ft Bottom Elevation: 246.00 ft Length: 28.00 ft Recommended length not to exceed 30 m. Maximum length is 90 m Manning's n: 0.0240 See HDS-2 Table 2.1 2 yr, 24 hr precip: 2.9800 in

Sheet Flow Results Slope: 0.0143 ft/ft Time of Concentration: 0.97 min

Hydrograph - culvert - Rational Hydrograph Method 25 year recurrence Interval, Peak Discharge: 4.082 cfs, Time to Peak: 5.00 (min), Total Volume:

1224.63 ft^3

Time (minutes) Flow cfs

0.00 0.00

1.00 0.82

2.00 1.63

3.00 2.45

4.00 3.27

5.00 4.08

6.00 3.27

7.00 2.45

8.00 1.63

9.00 0.82

10.00 0.00

HY-8 Culvert Analysis Report Crossing Discharge Data

Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 0 cfs Design Flow: 9.1 cfs Maximum Flow: 9.1 cfs

Table 1 - Summary of Culvert Flows at Crossing: 25-yr Headwater Elevation (ft)Total Discharge (cfs) 18 RCP 25-yr

Discharge (cfs) Roadway Discharge

(cfs) Iterations

229.39 0.00 0.00 0.00 1

229.86 0.91 0.91 0.00 1

230.06 1.82 1.82 0.00 1

230.24 2.73 2.73 0.00 1

230.42 3.64 3.64 0.00 1

230.57 4.55 4.55 0.00 1

230.72 5.46 5.46 0.00 1

230.87 6.37 6.37 0.00 1

231.03 7.28 7.28 0.00 1

231.21 8.19 8.19 0.00 1

231.40 9.10 9.10 0.00 1

237.27 23.00 23.00 0.00 Overtopping

Rating Curve Plot for Crossing: 25-yr

Table 2 - Culvert Summary Table: 18 RCP 25-yr Total

Discharg e (cfs)

Culvert Discharg e (cfs)

Headwate r

Elevation (ft)

Inlet Control Depth (ft)

Outlet Control Depth (ft)

Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity

(ft/s)

Tailwater Velocity

(ft/s)

0.00 0.00 229.39 0.000 0.000 0-NF 0.000 0.000 0.000 0.000 0.000 0.000

0.91 0.91 229.86 0.465 0.0* 1-S2n 0.188 0.351 0.194 0.047 6.730 4.695

1.82 1.82 230.06 0.669 0.0* 1-S2n 0.263 0.504 0.275 0.072 8.025 6.132

2.73 2.73 230.24 0.852 0.0* 1-S2n 0.321 0.625 0.342 0.091 8.741 7.156

3.64 3.64 230.42 1.025 0.0* 1-S2n 0.371 0.729 0.399 0.108 9.318 7.966

4.55 4.55 230.57 1.182 0.0* 1-S2n 0.416 0.817 0.452 0.124 9.818 8.662

5.46 5.46 230.72 1.332 0.0* 1-S2n 0.457 0.898 0.502 0.138 10.177 9.263

6.37 6.37 230.87 1.483 0.0* 1-S2n 0.496 0.970 0.556 0.151 10.329 9.802

7.28 7.28 231.03 1.644 0.0* 5-S2n 0.532 1.042 0.594 0.163 10.806 10.296

8.19 8.19 231.21 1.820 0.0* 5-S2n 0.567 1.105 0.643 0.175 10.943 10.744

9.10 9.10 231.40 2.013 0.173 5-S2n 0.600 1.162 0.685 0.186 11.201 11.161

* Full Flow Headwater elevation is below inlet invert.

Straight Culvert

Inlet Elevation (invert): 229.39 ft, Outlet Elevation (invert): 227.36 ft

Culvert Length: 34.06 ft, Culvert Slope: 0.0597

Culvert Performance Curve Plot: 18 RCP 25-yr

Water Surface Profile Plot for Culvert: 18 RCP 25-yr

Site Data - 18 RCP 25-yr Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 229.39 ft Outlet Station: 34.00 ft Outlet Elevation: 227.36 ft Number of Barrels: 1

Culvert Data Summary - 18 RCP 25-yr Barrel Shape: Circular Barrel Diameter: 1.50 ft Barrel Material: Concrete Embedment: 0.00 in Barrel Manning's n: 0.0130 Culvert Type: Straight Inlet Configuration: Square Edge with Headwall Inlet Depression: None

Table 3 - Downstream Channel Rating Curve (Crossing: 25-yr) Flow (cfs) Water Surface

Elev (ft) Depth (ft) Velocity (ft/s) Shear (psf) Froude Number

0.00 227.36 0.00 0.00 0.00 0.00

0.91 227.41 0.05 4.70 1.03 3.85

1.82 227.43 0.07 6.13 1.56 4.11

2.73 227.45 0.09 7.16 1.98 4.27

3.64 227.47 0.11 7.97 2.36 4.37

4.55 227.48 0.12 8.66 2.69 4.47

5.46 227.50 0.14 9.26 3.00 4.54

6.37 227.51 0.15 9.80 3.28 4.60

7.28 227.52 0.16 10.30 3.55 4.65

8.19 227.54 0.18 10.74 3.81 4.70

9.10 227.55 0.19 11.16 4.05 4.75

Tailwater Channel Data - 25-yr Tailwater Channel Option: Trapezoidal Channel Bottom Width: 4.00 ft Side Slope (H:V): 2.00 (_:1) Channel Slope: 0.3485 Channel Manning's n: 0.0240 Channel Invert Elevation: 227.36 ft

Roadway Data for Crossing: 25-yr Roadway Profile Shape: Constant Roadway Elevation Crest Length: 50.00 ft Crest Elevation: 237.27 ft Roadway Surface: Gravel Roadway Top Width: 8.00 ft

WinTR-55 Current Data Description

--- Identification Data ---

User: BLM Date: 7/22/2022 Project: CHOH 206(1) 913(1) Etc Units: English SubTitle: CULVERT 101+78.12 Areal Units: Acres State: Maryland County: Frederick NOAA_C Filename: C:\Users\Brett.Morris\Documents\working projects\CHOH 206(1) 913(1) Etc\COMPUTATIONS\CHOH 206(1)

--- Sub-Area Data ---

Name Description Reach Area(ac) RCN Tc CULVERT 101+78.12 Outlet 4 75 0.228

Total area: 4 (ac)

--- Storm Data --

Rainfall Depth by Rainfall Return Period

2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr

(in) (in) (in) (in) (in) (in) (in)

3.07 3.9 4.64 5.77 6.79 7.95 2.54

Storm Data Source: Frederick NOAA_C County, MD (NRCS) Rainfall Distribution Type: Type II Dimensionless Unit Hydrograph: <standard>

WinTR-55, Version 1.00.10 Page 1 7/22/2022 3:35:49 PM

BLM CHOH 206(1) 913(1) Etc

CULVERT 101+78.12

Frederick NOAA_C County, Maryland

Storm Data

Rainfall Depth by Rainfall Return Period

2-Yr 5-Yr 10-Yr 25-Yr 50-Yr 100-Yr 1-Yr

(in) (in) (in) (in) (in) (in) (in)

3.07 3.9 4.64 5.77 6.79 7.95 2.54

Storm Data Source: Frederick NOAA_C County, MD (NRCS) Rainfall Distribution Type: Type II Dimensionless Unit Hydrograph: <standard>

Frederick NOAA_C County, Maryland

Watershed Peak Table

Sub-Area Peak Flow by Rainfall Return Period or Reach 100-Yr Identifier (cfs)

SUBAREAS

CULVERT 25.42

REACHES

OUTLET 25.42

Frederick NOAA_C County, Maryland

Hydrograph Peak/Peak Time Table

Sub-Area Peak Flow and Peak Time (hr) by Rainfall Return Period or Reach 100-Yr Identifier (cfs) (hr)

SUBAREAS

CULVERT 25.42

12.03

REACHES

OUTLET 25.42

Frederick NOAA_C County, Maryland

Sub-Area Summary Table

Sub-Area Drainage Time of Curve Receiving Sub-Area Identifier Area Concentration Number Reach Description

(ac) (hr) CULVERT 4.00 0.228 75 Outlet 101+78.12

Total Area: 4 (ac)

Frederick NOAA_C County, Maryland

Sub-Area Time of Concentration Details

Sub-Area Flow Mannings's End Wetted Travel Identifier/ Length Slope n Area Perimeter Velocity Time

(ft) (ft/ft) (sq ft) (ft) (ft/sec) (hr)

CULVERT

User-provided 0.228

Time of Concentration 0.228

Frederick NOAA_C County, Maryland

Sub-Area Land Use and Curve Number Details

Sub-Area Hydrologic Sub-Area Curve Identifier Land Use Soil Area Number Group (ac) CULVERT Gravel (w/ right-of-way) C .64 89 Woods - grass combination (good) C 3.36 72

Total Area / Weighted Curve Number 4 75

HY-8 Culvert Analysis Report Crossing Discharge Data

Discharge Selection Method: Specify Minimum, Design, and Maximum Flow Minimum Flow: 0 cfs Design Flow: 25.42 cfs Maximum Flow: 25.42 cfs

Table 1 - Summary of Culvert Flows at Crossing: 100-yr Headwater Elevation (ft)Total Discharge (cfs) 18 RCP 100-yr

Discharge (cfs) Roadway Discharge

(cfs) Iterations

229.39 0.00 0.00 0.00 1

230.20 2.54 2.54 0.00 1

230.66 5.08 5.08 0.00 1

231.10 7.63 7.63 0.00 1

231.66 10.17 10.17 0.00 1

232.39 12.71 12.71 0.00 1

233.31 15.25 15.25 0.00 1

234.41 17.79 17.79 0.00 1

235.71 20.34 20.34 0.00 1

237.19 22.88 22.88 0.00 1

238.85 25.42 25.42 0.00 1

239.00 25.64 25.64 0.00 Overtopping

Rating Curve Plot for Crossing: 100-yr

Table 2 - Culvert Summary Table: 18 RCP 100-yr Total

Discharg e (cfs)

Culvert Discharg e (cfs)

Headwate r

Elevation (ft)

Inlet Control Depth (ft)

Outlet Control Depth (ft)

Flow Type

Normal Depth (ft)

Critical Depth (ft)

Outlet Depth (ft)

Tailwater Depth (ft)

Outlet Velocity

(ft/s)

Tailwater Velocity

(ft/s)

0.00 0.00 229.39 0.000 0.000 0-NF 0.000 0.000 0.000 0.000 0.000 0.000

2.54 2.54 230.20 0.812 0.0* 1-S2n 0.310 0.601 0.328 0.087 8.590 6.964

5.08 5.08 230.66 1.270 0.0* 1-S2n 0.440 0.863 0.481 0.132 10.050 9.025

7.63 7.63 231.10 1.709 0.0* 5-S2n 0.545 1.066 0.613 0.168 10.851 10.465

10.17 10.17 231.66 2.268 0.422 5-S2n 0.639 1.227 0.728 0.199 11.556 11.612

12.71 12.71 232.39 3.002 1.091 5-S2n 0.726 1.341 0.839 0.227 12.112 12.569

15.25 15.25 233.31 3.916 1.876 5-S2n 0.810 1.414 0.944 0.253 12.626 13.396

17.79 17.79 234.41 5.017 2.706 5-S2n 0.894 1.305 1.030 0.277 13.363 14.134

20.34 20.34 235.71 6.323 3.824 5-S2n 0.981 1.500 1.199 0.299 13.079 14.797

22.88 22.88 237.19 7.804 4.980 5-S2n 1.074 1.500 1.227 0.320 14.423 15.404

25.42 25.42 238.85 9.459 6.273 5-S2n 1.183 1.500 1.333 0.340 15.012 15.958

* Full Flow Headwater elevation is below inlet invert.

Straight Culvert

Inlet Elevation (invert): 229.39 ft, Outlet Elevation (invert): 227.36 ft

Culvert Length: 34.06 ft, Culvert Slope: 0.0597

Culvert Performance Curve Plot: 18 RCP 100-yr

Water Surface Profile Plot for Culvert: 18 RCP 100-yr

Site Data - 18 RCP 100-yr Site Data Option: Culvert Invert Data Inlet Station: 0.00 ft Inlet Elevation: 229.39 ft Outlet Station: 34.00 ft Outlet Elevation: 227.36 ft Number of Barrels: 1

Culvert Data Summary - 18 RCP 100-yr Barrel Shape: Circular Barrel Diameter: 1.50 ft Barrel Material: Concrete Embedment: 0.00 in Barrel Manning's n: 0.0130 Culvert Type: Straight Inlet Configuration: Square Edge with Headwall Inlet Depression: None

Table 3 - Downstream Channel Rating Curve (Crossing: 100-yr) Flow (cfs) Water Surface

Elev (ft) Depth (ft) Velocity (ft/s) Shear (psf) Froude Number

0.00 227.36 0.00 0.00 0.00 0.00

2.54 227.45 0.09 6.96 1.90 4.24

5.08 227.49 0.13 9.03 2.87 4.51

7.63 227.53 0.17 10.47 3.65 4.67

10.17 227.56 0.20 11.61 4.33 4.79

12.71 227.59 0.23 12.57 4.94 4.88

15.25 227.61 0.25 13.40 5.50 4.95

17.79 227.64 0.28 14.13 6.01 5.02

20.34 227.66 0.30 14.80 6.50 5.07

22.88 227.68 0.32 15.40 6.96 5.12

25.42 227.70 0.34 15.96 7.40 5.16

Tailwater Channel Data - 100-yr Tailwater Channel Option: Trapezoidal Channel Bottom Width: 4.00 ft Side Slope (H:V): 2.00 (_:1) Channel Slope: 0.3485 Channel Manning's n: 0.0240 Channel Invert Elevation: 227.36 ft

Roadway Data for Crossing: 100-yr Roadway Profile Shape: Constant Roadway Elevation Crest Length: 50.00 ft Crest Elevation: 239.00 ft Roadway Surface: Gravel Roadway Top Width: 8.00 ft

NOAA Atlas 14, Volume 2, Version 3 Location name: Knoxville, Maryland, USA*

Latitude: 39.3063°, Longitude: -77.5897° Elevation: 230.01 ft**

* source: ESRI Maps ** source: USGS

POINT PRECIPITATION FREQUENCY ESTIMATES

G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley

NOAA, National Weather Service, Silver Spring, Maryland

PF_tabular | PF_graphical | Maps_&_aerials

PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1

Duration Average recurrence interval (years)

1 2 5 10 25 50 100 200 500 1000

5-min 4.01 (3.59-4.48)

4.79 (4.28-5.34)

5.75 (5.14-6.41)

6.48 (5.77-7.20)

7.42 (6.58-8.22)

8.16 (7.20-9.04)

8.90 (7.81-9.86)

9.70 (8.45-10.7)

10.8 (9.30-11.9)

11.6 (9.92-12.8)

10-min 3.17 (2.84-3.55)

3.80 (3.41-4.25)

4.55 (4.07-5.08)

5.11 (4.55-5.68)

5.83 (5.17-6.47)

6.39 (5.64-7.08)

6.96 (6.11-7.70)

7.52 (6.56-8.32)

8.29 (7.16-9.18)

8.89 (7.61-9.84)

15-min 2.62 (2.35-2.94)

3.15 (2.82-3.52)

3.80 (3.40-4.24)

4.27 (3.81-4.75)

4.88 (4.33-5.42)

5.34 (4.72-5.92)

5.82 (5.11-6.44)

6.29 (5.48-6.96)

6.93 (5.98-7.68)

7.42 (6.36-8.22)

30-min 1.78 (1.59-1.99)

2.16 (1.93-2.41)

2.67 (2.39-2.98)

3.05 (2.72-3.39)

3.56 (3.16-3.95)

3.96 (3.49-4.39)

4.37 (3.84-4.84)

4.80 (4.18-5.31)

5.38 (4.65-5.96)

5.86 (5.01-6.48)

60-min 1.10 (0.986-1.23)

1.34 (1.20-1.50)

1.70 (1.52-1.89)

1.97 (1.76-2.19)

2.35 (2.08-2.61)

2.66 (2.35-2.94)

2.98 (2.62-3.30)

3.33 (2.90-3.68)

3.82 (3.30-4.23)

4.22 (3.61-4.67)

2-hr 0.652 (0.583-0.730)

0.794 (0.712-0.890)

1.01 (0.902-1.13)

1.18 (1.05-1.32)

1.43 (1.27-1.60)

1.64 (1.45-1.83)

1.87 (1.64-2.08)

2.12 (1.84-2.35)

2.49 (2.14-2.76)

2.80 (2.38-3.10)

3-hr 0.470 (0.421-0.529)

0.570 (0.510-0.641)

0.722 (0.645-0.811)

0.845 (0.751-0.946)

1.02 (0.905-1.15)

1.18 (1.03-1.31)

1.34 (1.17-1.49)

1.52 (1.32-1.69)

1.79 (1.53-1.99)

2.02 (1.71-2.25)

6-hr 0.293 (0.264-0.330)

0.354 (0.318-0.398)

0.445 (0.398-0.500)

0.521 (0.464-0.583)

0.632 (0.559-0.705)

0.728 (0.640-0.810)

0.832 (0.726-0.925)

0.948 (0.819-1.05)

1.12 (0.957-1.24)

1.27 (1.07-1.41)

12-hr 0.179 (0.160-0.201)

0.215 (0.193-0.242)

0.270 (0.242-0.303)

0.317 (0.282-0.355)

0.387 (0.342-0.432)

0.449 (0.393-0.499)

0.518 (0.449-0.575)

0.595 (0.511-0.659)

0.713 (0.602-0.790)

0.816 (0.679-0.903)

24-hr 0.103 (0.095-0.112)

0.124 (0.114-0.135)

0.156 (0.144-0.171)

0.184 (0.169-0.201)

0.226 (0.206-0.245)

0.262 (0.238-0.284)

0.302 (0.272-0.327)

0.347 (0.309-0.374)

0.415 (0.363-0.447)

0.473 (0.409-0.509)

2-day 0.059 (0.055-0.065)

0.072 (0.066-0.078)

0.090 (0.083-0.098)

0.106 (0.097-0.115)

0.129 (0.118-0.140)

0.149 (0.136-0.162)

0.171 (0.154-0.186)

0.196 (0.175-0.212)

0.232 (0.204-0.252)

0.263 (0.228-0.286)

3-day 0.042 (0.039-0.046)

0.051 (0.047-0.055)

0.064 (0.059-0.069)

0.075 (0.069-0.081)

0.091 (0.083-0.099)

0.105 (0.096-0.114)

0.121 (0.109-0.130)

0.137 (0.123-0.149)

0.163 (0.143-0.176)

0.184 (0.160-0.199)

4-day 0.034 (0.031-0.036)

0.040 (0.037-0.044)

0.051 (0.047-0.055)

0.059 (0.055-0.064)

0.072 (0.066-0.078)

0.083 (0.076-0.090)

0.095 (0.086-0.102)

0.108 (0.097-0.117)

0.128 (0.113-0.138)

0.144 (0.126-0.156)

7-day 0.022 (0.021-0.024)

0.027 (0.025-0.029)

0.033 (0.031-0.036)

0.038 (0.036-0.041)

0.046 (0.043-0.050)

0.053 (0.048-0.057)

0.060 (0.054-0.064)

0.067 (0.061-0.072)

0.078 (0.070-0.085)

0.088 (0.078-0.095)

10-day 0.018 (0.017-0.019)

0.021 (0.020-0.023)

0.026 (0.024-0.028)

0.030 (0.028-0.032)

0.036 (0.033-0.038)

0.040 (0.037-0.043)

0.045 (0.041-0.048)

0.050 (0.046-0.054)

0.058 (0.052-0.062)

0.064 (0.057-0.069)

20-day 0.012 (0.011-0.013)

0.014 (0.013-0.015)

0.017 (0.016-0.018)

0.019 (0.018-0.020)

0.022 (0.020-0.023)

0.024 (0.023-0.026)

0.026 (0.025-0.028)

0.029 (0.027-0.031)

0.032 (0.029-0.034)

0.035 (0.032-0.037)

30-day 0.010 (0.009-0.010)

0.012 (0.011-0.012)

0.014 (0.013-0.014)

0.015 (0.014-0.016)

0.017 (0.016-0.018)

0.019 (0.018-0.020)

0.020 (0.019-0.022)

0.022 (0.020-0.023)

0.024 (0.022-0.026)

0.026 (0.024-0.027)

45-day 0.008 (0.008-0.009)

0.010 (0.009-0.010)

0.011 (0.011-0.012)

0.012 (0.012-0.013)

0.014 (0.013-0.014)

0.015 (0.014-0.015)

0.016 (0.015-0.017)

0.017 (0.016-0.018)

0.018 (0.017-0.019)

0.019 (0.018-0.020)

60-day 0.007 (0.007-0.008)

0.009 (0.008-0.009)

0.010 (0.009-0.010)

0.011 (0.010-0.011)

0.012 (0.011-0.012)

0.013 (0.012-0.013)

0.013 (0.013-0.014)

0.014 (0.013-0.015)

0.015 (0.014-0.016)

0.016 (0.015-0.017)

1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).

Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.

Please refer to NOAA Atlas 14 document for more information.

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11/17/2021https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=39.3063&lon=-77.5897&da...

PF graphical

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Maps & aerials

Small scale terrain

Large scale terrain

3km

2mi

100km

60mi

100km

60mi

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US Department of Commerce National Oceanic and Atmospheric Administration

National Weather Service National Water Center

1325 East West Highway Silver Spring, MD 20910

Questions?: HDSC.Questions@noaa.gov

Disclaimer

100km

60mi

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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, Maryland, and Loudoun County, Virginia

Natural Resources Conservation Service

July 6, 2022

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 http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/ https://offices.sc.egov.usda.gov/locator/app?agency=nrcs http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?cid=nrcs142p2_053951 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.

Contents Preface How Soil Surveys Are Made Soil Map

Soil Map Legend Map Unit Legend Map Unit Descriptions

Frederick County, Maryland CdE—Catoctin-Highfield complex, 25 to 45 percent slopes, very rocky CgA—Codorus and Hatboro silt loams, 0 to 3 percent slopes CmA—Combs fine sandy loam, 0 to 3 percent slopes DoB—Downsville gravelly loam, 3 to 8 percent slopes DoC—Downsville gravelly loam, 8 to 15 percent slopes LsA—Lindside silt loam, 0 to 3 percent slopes MaA—Melvin-Lindside silt loams, 0 to 3 percent slopes MoB—Mt. Zion-Codorus complex, 0 to 8 percent slopes MxB—Myersville-Burkittsville complex, 3 to 8 percent slopes ScC—Spoolsville-Burkittsville complex, 8 to 15 percent slopes ScD—Spoolsville-Burkittsville complex, 15 to 25 percent slopes UdB—Udorthents, smooth, 0 to 8 percent slopes W—Water

Loudoun County, Virginia 7A—Huntington silt loam, 0 to 2 percent slopes, occasionally flooded 20C—Purcellville and Tankerville soils, 7 to 15 percent slopes 20D—Purcellville and Tankerville soils, 15 to 25 percent slopes 20E—Tankerville and Purcellville soils, 25 to 45 percent slopes

References

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 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 identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately.

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.

Soil Map

276500 276800 277100 277400 277700 278000 278300 278600 278900 279200

276500 276800 277100 277400 277700 278000 278300 278600 278900 279200

39° 19' 2'' N

5'

7' ' W

39° 19' 2'' N

3'

7' ' W

39° 18' 2'' N

5'

7' ' W

39° 18' 2'' N

3'

7' ' W

N

Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 0 500 1000 2000 3000

Feet 0 150 300 600 900

Meters Map Scale: 1:13,100 if printed on A landscape (11" x 8.5") sheet.

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 1:12,000.

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, Maryland Survey Area Data: Version 18, Aug 27, 2021

Soil Survey Area: Loudoun County, Virginia Survey Area Data: Version 18, Sep 14, 2021

Your area of interest (AOI) includes more than one soil survey area. These survey areas may have been mapped at different scales, with a different land use in mind, at different times, or at different levels of detail. This may result in map unit symbols, soil properties, and interpretations that do not completely agree across soil survey area boundaries.

Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Sep 23, 2020—Nov 20, 2020

The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background

MAP LEGEND MAP INFORMATION

imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Map Unit Legend

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

CdE Catoctin-Highfield complex, 25 to 45 percent slopes, very rocky

19.1 3.2%

CgA Codorus and Hatboro silt loams, 0 to 3 percent slopes

16.6 2.8%

CmA Combs fine sandy loam, 0 to 3 percent slopes

67.9 11.5%

DoB Downsville gravelly loam, 3 to 8 percent slopes

32.4 5.5%

DoC Downsville gravelly loam, 8 to 15 percent slopes

109.1 18.5%

LsA Lindside silt loam, 0 to 3 percent slopes

61.0 10.4%

MaA Melvin-Lindside silt loams, 0 to 3 percent slopes

1.0 0.2%

MoB Mt. Zion-Codorus complex, 0 to 8 percent slopes

10.1 1.7%

MxB Myersville-Burkittsville complex, 3 to 8 percent slopes

5.8 1.0%

ScC Spoolsville-Burkittsville complex, 8 to 15 percent slopes

17.7 3.0%

ScD Spoolsville-Burkittsville complex, 15 to 25 percent slopes

46.3 7.9%

UdB Udorthents, smooth, 0 to 8 percent slopes

3.6 0.6%

W Water 158.6 26.9%

Subtotals for Soil Survey Area 549.3 93.2%

Totals for Area of Interest 589.3 100.0%

Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI

7A Huntington silt loam, 0 to 2 percent slopes, occasionally flooded

0.2 0.0%

20C Purcellville and Tankerville soils, 7 to 15 percent slopes

2.0 0.3%

20D Purcellville and Tankerville soils, 15 to 25 percent slopes

14.2 2.4%

20E Tankerville and Purcellville soils, 25 to 45 percent slopes

23.6 4.0%

Subtotals for Soil Survey Area 40.0 6.8%

Totals for Area of Interest 589.3 100.0%

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, 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.