Rainfall Runoff Management CNMP Core Curriculum Section 4 – Manure Wastewater Storage and Handling

CNMP Development Core Training Curriculum These course materials have been developed as a cooperative effort between five land-grant universities and The Natural Resources Conservation Service. Ames, Iowa 50011, (515) Copyright © , Iowa State University of Science and Technology. All rights reserved. Copyright Information

Objectives 1.Keep the clean water clean 2.Recognize rainfall runoff effects on: storage volume in liquid manure systems application logistics and nutrient content

Required Materials Animal Waste Management Field Handbook, Part 651, Chapter 10, Agricultural Waste Management System Component Design. NRCS Conservation Practice Standard 558 Roof Runoff Structure. Supplemental Resources –AWM and NOAA addresses and resources

Rainfall Runoff Management

Divert Clean Water

Rainfall Runoff Management Clean Water Diversion

Rainfall Runoff Management Roof Runoff

Rainfall Runoff Management Runoff Volume Characteristics 1.Rainfall Amount 2.Infiltration 3.Evaporation 4.Drainage Area

Rainfall Runoff Factors to Consider: 1. Normal precipitation from runoff area 2. Normal precipitation minus evaporation on Storage Structure 3. Emergency Storm from runoff areas 4. Emergency Storm on Storage Structure

Runoff Management Normal Precipitation and Evaporation is based on County and Weather Station rainfall record data. Runoff volume is based on this climate data and Runoff Curve Number information.

Normal Precipitation Climate Data Sources: *AWM Software *NOAA *State or Local

MonthPrec. (in)Evap. (in) January February March April May June July August September October November December Totals Typical AWM Data: State: TN County: Loudon Station: TN Yr, 24-Hr Storm Event: 5.6 inches

Evaporation Storage and treatment facilities require an allowance for precipitation less evaporation for the most critical design period.

Evaporation

Factors effecting free water surface evaporation 1. Effects of salinity 2. Coloration 3. Floating surface material, such as bedding or crusting Local records are available for average monthly evaporation.

The Runoff (Q) Equation Factors Q = Runoff in inches P = Rainfall in inches Ia = Initial abstraction in inches S = Potential maximum retention after runoff begins in inches

Runoff Curve Number (RCN or CN) CN = 1000/(10 + S) The RCN’s were developed by examining rainfall runoff data from small agricultural watersheds

Runoff Depth for selected CN’s and rainfall amounts Rainfall (in)CN=60CN=80CN=

Infiltration Cover description Curve Numbers for hydrologic soil group Cover type & hydrologic conditionABCD Pasture, grassland, or range, good condition Bare soil, pervious areas, no vegetation Impervious areas, paved lots, roofs, driveways98

Infiltration Runoff Factors: *soil hydrologic characteristics *type of cover

Infiltration Runoff Curve Number (RCN) of 90 is representative of an unpaved or unsurfaced feedlot A paved or surfaced feedlot typically has a RCN of about 97

Infiltration (Runoff from an earth feedlot near Dallas, TX.)

Class Example: Calculate the runoff depth from a 6-inch rainfall: 1.On a pasture with good hydrologic conditions and “B” hydrologic soil group 2.For an unsurfaced feedlot with a RCN of 90 (Hint: look at slide #19 & #20)

Class Example: 1.From slide 19- CN is 61; & slide 18 with CN of 61, the runoff depth can be interpolated for the 6-inch rainfall to be 2.01 inches 2.From slide 18, CN of 90, the runoff depth from interpolation is 4.86 inches (Note: same rainfall, over twice runoff on feedlot)

Determining Runoff Volume Runoff Volume is dependent on: –Surface area –Rainfall depth –Surface type (paved vs. unpaved) Maps in Appendix 10C of AWMFH can be used to determine runoff volumes from surfaced or unsurfaced feed lots –Surfaced, CN 97 –Unsurfaced, CN 90

Determining Runoff Volume Runoff Volume = Surface Area (ft 2 ) x Rainfall (ft) x (% Runoff from Surface ÷ 100)

In-Class Exercise A 6.0 acre open beef feedlot is being constructed near Ames, IA. The annual rainfall at Ames, IA is 30 inches. The earthen portion of the lot is 5.5 acres, and the concrete portion is 0.5 acres. Using the Annual Runoff charts for surfaced (CN 97) and unsurfaced (CN90) feedlots, determine the volume of runoff that will leave the 6 acre feedlot in Ames, IA.

In-class Exercise 1 acre = 43,560 ft 2 Concrete Area _______ ft 2 Earthen Lot Area _______ ft 2 Annual Rainfall _______ ft CN 90 Runoff Percentage ______ % CN 97 Runoff Percentage ______ %

In-class Exercise Concrete Area 21,780 ft2 Earthen Lot Area 239,580 ft2 Annual Rainfall 2.5 ft CN 90 Runoff Percentage 23 % CN 97 Runoff Percentage 55 % Runoff Volume = Area x Rainfall x (CN % Runoff ÷ 100) Total Runoff Volume = Runoff Volume earthen + Volume of Runoff concrete

In-class Exercise Runoff Vol. earthen = Area x Rainfall x (CN 90 % Runoff ÷ 100) = 239,580 ft 2 x 2.5 ft x 0.23 = 137,760 ft 3 Runoff Vol. concrete = Area x Rainfall x (CN 97 % Runoff ÷ 100) = 21,780 ft 2 x 2.5 ft x 0.55 = 29,950 ft 3 Total Runoff Vol. = Runoff Vol. earthen + Runoff Vol. concrete = 137,760 ft + 29,950 ft = 167,710 ft3

Runoff Management AWM uses a more conservative approach to estimating runoff from runoff areas as compared to tables in AWMFH. AWM includes a climate database with monthly precipitation and evaporation.

Runoff Management AWM allows input based on Pervious and Impervious watershed Impervious - concrete, roofs Curve Number of 98 - cannot be modified Pervious - manure pack or other CN of 90 - can modify

Emergency Storm Runoff Variables 1) Depth of 25- year, 24-hour storm on storage structure 2) Depth of 25- year, 24-hour storm from runoff areas to storage structure

4 Components of Runoff

Determining Rainfall Runoff Amounts Site Visit – Sample CNMP Dairy

Identify Areas that contribute runoff Determining Rainfall Runoff Amounts

To Storage pond Determining Rainfall Runoff Amounts Rainfall on Open and Concrete Lots

Roof Area Determining Rainfall Runoff Amounts Runoff from roofs

Rainfall on Storage Structure Determining Rainfall Runoff Amounts

Concrete Areas that Contribute Runoff Determining Rainfall Runoff Amounts

Silage Bunker Runoff - Condition when Full Drain- to storage pond

Silage Bunker - Condition when empty Runoff = 6000 ft 2 To Storage pond Determining Rainfall Runoff Amounts

Determining Rainfall Runoff Amounts

Total 30,420 sf

1.Assuming a sufficient storage of 90 days. 2.What can we do to reduce runoff into the storage structure and increase the storage period? 3.Why would you need more than 90 days of storage? Determining Rainfall Runoff Amounts

1.What can we do to reduce runoff into the storage structure and increase the storage period? Enlarge pond, gutter roof, diversions 2.Why would you need more than 90 days of storage? Land application restraints, climate, crop needs, etc Determining Rainfall Runoff Amounts

Critical Storage Interval Based on initial site conditions, the critical storage interval for the sample CNMP dairy was determined to be 151 days, November - March

What If we Gutter 10,000 sq ft? Determining Rainfall Runoff Amounts 20,420 ft 2

Adequate storage for 120 to 150 days; enough to survive critical winter months of Dec thru March by Guttering Determining Rainfall Runoff Amounts

115,980 cu. Ft. (all runoff areas) -77,850 cu. Ft. 38,130 cu. Ft. (clean water removed) 38,130 cu. Ft. x 7.48 gallons/ cu. Ft. = 285,212 gallons Benefits of Guttering: 1) 10 to 12 hours less pumping per year 2) storage period is increased (120 to 150 days) 3) low cost ($6.00 linear foot) $6.00 x 150 linear feet = $1000 to $2000 How much clean water is removed by guttering? Determining Rainfall Runoff Amounts

What if we install more roofs & gutters? Determining Rainfall Runoff Amounts 10,420 ft 2

Adequate storage for 180 days; IDEAL by Guttering and Roofing Determining Rainfall Runoff Amounts

115,980 cu. Ft. (runoff from all areas) -39,730 cu. Ft. 76,250 cu. Ft. (clean water removed) 76,250 cu. Ft. x 7.48 gallons/ cu. Ft. = 570,350 gallons Benefits of Roofing & guttering: 1) 20 hours less pumping per year 2) storage period is increased Disadvantage: COST - $5.00 sq. ft. x 10,000 sq. ft. = $50,000 Roofing? Determining Rainfall Runoff Amounts

GIVEN: It was determined that existing storage capacity is not adequate to last through winter months. SOLUTION: Look at the previous alternatives and discuss each with the decision-maker. Decision-maker's Alternatives

Alternatives: >>>> #1 Increase storage structure #2 Gutter existing roof (10,000 sf) #3 #2 plus additional roofing & guttering (10,000 sf) Objectives met: >>>> Increased storage Increased storage (to days) Reduced pumping time Increased storage (to 180 days) Reduced pumping time Cost: >>>>Moderate $15k-$20k Low $6/ linear ft $1k-$2k High Roof $5/sq ft = $50k + $2 = $52k

Runoff Management Summary 1.Keep the clean water clean (diversions, roofs & gutters) 2.Evaluate and appropriately collect contaminated runoff into storage structures or properly treat runoff from the heavy use areas (pervious or impervious) 3. Consider the effect of rainfall runoff on application logistics and nutrient content of the waste material 4. Design a runoff management system with adequate capacity

Questions or Comments?

Gutter Design Procedure 1)Compute the capacity of the selected gutter size 2)Compute the capacity of the downspout 3)Determine whether the system is controlled by the gutter capacity or downspout capacity and adjust number of downspouts if desired 4)Determine the roof area that can be served

Gutter Position

Gutter Design Final Step: Adequate discharge pipeline or trough based on gutter/downspout design capacity Material Quality