Stormwater Management

SSc6.1/SSc6.2

Discharge Rate and quantity

Project Name

ProjectName �1

Stormwater Management / Drainage Report Sample Outline: I. Summary

§ Site conditions and location § Percentile rainfall events calculations § Compliance with LEED requirements

II. Site Description Existing Conditions including:

§ Site area and location § Land use § Soil types and conditions § Surrounding conditions and adjacent developments § Existing drainage areas and catchment basins § Current stormwater flow and management

Proposed stormwater management § Best Management Practices BMP / Low Impact Development / Green Infrastructure

III. Hydrologic Analysis (SSc6.1) § Runoff rates § The approach for meeting LEED credit requirements for implementing a stormwater

management plan that replicates natural site hydrology processes, manages onsite the runoff from the developed site for the 95th percentile of local rainfall events using LID and green infrastructure.

§ 95th percentile calculations § Calculations of stormwater volume § Results demonstrating LID and green infrastructure managing onsite runoff for the 95th

percentile § Conclusions

IV. Water Quality Analysis (SSc6.2) § Approach for meeting LEED credit requirement that 80% of total suspended solids are

removed from the stormwater runoff for 90% of the average annual storm events § Details of project’s structural and nonstructural Best Management Practice (BMP)

methods incorporated into the design § Non-structural BMP measures (i.e. pervious pavement, Infiltration trench,

vegetated swale) § Conclusions

V. Conclusions § Evaluation of the quantity and quality of stormwater LID and green infrastructure

managing onsite runoff for the 95th percentile and demonstrated compliance with LEED requirements

VI. Annex § Local regulations § Bibliography and references

ProjectName �2

I.Summary

The following report presents an analysis of the proposed system for stormwater management for the project XXX in Guadalajara, a project located in XXX, XXXXX, Guadalajara, Jalisco.

- Site conditions and location

Under the Köppen climate classification, Guadalajara has a humid subtropical climate (Cwa) that is quite close to a tropical climate, featuring dry, warm winters and hot, wet summers. Guadalajara's climate is influenced by its high altitude and the general seasonality of precipitation patterns in western North America.

Although the temperature is warm year-round, Guadalajara has very strong seasonal variation in precipitation. The northward movement of the Inter-Tropical Convergence Zone brings a great deal of rain in the summer months, whereas for the rest of the year, the climate is rather arid. The extra moisture in the wet months moderates the temperatures, resulting in cooler days and nights during this period. The highest temperatures are usually reached in May averaging 33 °C (91 °F), but can reach up to 39 °C (102 °F) just before the onset of the wet season. March tends to be the driest month and July the wettest, with an average of 273 millimetres (10.7 in) of rain, over a quarter of the annual average of about 1,002 millimetres (39.4 in).

During the rainy season, afternoon storms are very common and can sometimes bring hail flurries to the city, especially toward late August or September. Winters are relatively warm despite the city's altitude, with January daytime temperatures reaching about 25 °C (77 °F) and nighttime temperatures about 10 °C (50 °F). However, the outskirts of the city (generally those close to the Primavera Forest) experience in average cooler temperatures than the city itself. There, temperatures around 0 °C (32 °F) can be recorded during the coldest nights. Frost may also occur during the coldest nights, but temperatures rarely fall below 0 °C (32 °F) in the city, making it an uncommon phenomenon. Cold fronts in winter can sometimes bring light rain to the city for several days in a row. Snowfall is extraordinarily rare, with the last recorded one occurring in December 1997, which was the first time in 116 years, since it last fell in 1881.

- Percentile rainfall events calculations

Daily rainfall data and the methodology in the United States Environmental Protection Agency’s Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act has been used to determine the 95th percentile amount.

- Compliance with LEED requirements

ProjectName �3

SSc6.1 - LEED Certification requires to limit the disruption of natural hydrology by reducing impervious cover, increasing on-site infiltration, reducing or eliminating pollution from stormwater runoff and eliminating contaminants. This project is under Option 2. Percentile rainfall events. Case 1: Non-zero lot line projects. This credit is achieved by replicating natural site hydrology processes, managing onsite, the runoff from the developed site for the 95th percentile of local rainfall events using Low Impact Development (LID) and green infrastructure.

SSc6.2 - LEED Certification requires to limit the disruption and pollution of natural water flows by managing stormwater runoff. This credit is achieved by implementing a stormwater management plan that reduces the impervious cover, promotes infiltration and captures and treats the stormwater runoff from 90% the average rainfall using acceptable BMP’s.

ProjectName �4

II. Site Description

- EXISTING CONDITIONS

- Site area and location

The project is built in a suburban area of Guadalajara. The environment is completely developed and with a low infiltration rate.

- Land use

The project area is composed of a building, a parking lot, a landscaped area and a hardscape area.

- Soil types and conditions

The geotechnical survey unveils existing rocks under the surface and shows that the site is not totally permeable to rainfall events. A runoff coefficient of c=0.17 has been selected for this type of soil.

ProjectName �5

Site location on map

- Surrounding conditions and adjacent developments

The following image indicates the location of the BD+C project within the larger Industrial Park area, the site is already developed and with a high rate of imperviousness:

- Existing drainage areas and catchment basins

There are no drainage areas neither catchment basins within the LEED boundary.

- Current stormwater flow and management

The Industrial Park has a stormwater management system were 100% of the rainwater is infiltrated through a vegetated swale. Project Name will use the park´s existing rainwater infrastructure.

ProjectName �6

Site location on map

- PROPOSED STORMWATER MANAGEMENT

- Best Management Practices BMP / Low Impact Development / Green Infrastructure

The Industrial Park has a stormwater management system consisting of an open concrete channel that harvests rainwater from the park, it discharges into a vegetated swale. The following images were taken at different places along the channel to better explain the system.

ProjectName �7

Stormwater channel

1. View in the direction of project 2. View towards channel

3. View before discharge into non-concrete channel 4. Vegetated swale

PROJECT

Vegetated Swale.

The vegetated swale is a continuation to the open concrete channel, were stormwater from the whole industrial park is discharged. The objective of the vegetated swale is to mimic natural processes to:

1)infiltrate and recharge; 2)evapotranspirate.

For this project, the vegetated swale is used as a stand-alone storm water Best Management Practice (BMP).

The industrial park´s vegetated swale follows criteria from the EPA Storm Water Technology Fact Sheet “Vegetated Swales”: 1. Periodic maintenance is given to the vegetated swale to prevent it from lacking filtration

capabilities, to keep pollutant removal rates unchanged, and to prevent erosion of exposed soil.

2. Natural vegetation is allowed to grow (see picture number 7 and 8 below) which includes different types of grasses that require no additional maintenance.

3. The total surface area of the swale has been calculated to account for one percent of the area that drains to the channel and then to the swale (Refer to calculations below).

ProjectName �8

Stormwater open channel

Stormwater underground channel

Plan showing location of images above

ProjectName �9

Stormwater channel industrial Park

5. Vegetated Swale 6. Vegetated Swale

7. Vegetated Swale 8. Vegetated Swale

Stormwater open channel Stormwater underground channel

Plan showing location of images above

III. Hydrologic Analysis (SSc6.1) (QUANTITY)

Since the stormwater management plan addresses all of the Industrial Park, calculations below have been made considering the complete scope of the rainwater system, and not only the areas that fall within the Project Name LEED boundary.

- Runoff Rates

The following tables are used to find out the runoff rates for the developed site.

Source: IMSS, 1977

Runoff rate for the Developed site:

ProjectName �10

Runoff CoefficientSurface Type

ROOFSPATIOS AND PARKINGTileAsphaltHydraulic concreteConcrete brickOpen grid pavementGARDENS: SANDY SOILHorizontalAverageSlopedGARDENS: CLAY SOILHorizontalAverageSloped

Colour Code

Developed site type of surface Area sf Runoff coefficient

Non-roof areas (sf):

Landscaped 5,214,810.06 0.17

Non-Roof - impervious (asphalt, concrete). Stormwater conducted to the open channel.

7,854,802.94 0.95

Roof areas (sf):

Roof - impervious. Stormwater conducted to the open channel

7,427,717.07 0.95

TOTAL sf 20,497,330.07

�

�

�

ProjectName �11

- The approach for meeting LEED credit requirements for implementing a stormwater

management plan that replicates natural site hydrology processes, manages onsite the runoff from the developed site for the 95th percentile of local rainfall events using LID and green infrastructure.

For Option 2. Percentile rainfall events, credit SSc6.1 states two cases:

“Case 1. Non-zero lot line projects”. “In a manner best replicating natural site hydrology processes, manage onsite the runoff from the developed site for the 95th percentile of regional or local rainfall events using Low Impact Development (LID) and green infrastructure. Use daily rainfall data and the methodology in the United States Environmental Protection Agency’s Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act to determine the 95th percentile amount.”.

“Case 2. Zero lot line projects”. “For zero lot line projects located in urban areas with a minimum density of 1.5 FAR (13,800 square meters per hectare net), in a manner best replicating natural site hydrology processes, manage onsite the runoff from the developed site for the 85th percentile of regional or local rainfall events using LID and green infrastructure.”.

This project falls under CASE 1.

- 95th Percentile calculations

A long period of precipitation records, i.e., a minimum of 10 years of data, is needed to determine the 95th percentile rainfall event for a location. Thirty years or more of monitoring data are desirable to conduct an unbiased statistical analysis. The National Meteorological Service (SMN for its acronym in Spanish) provides long-term precipitation data for many locations of Mexico. For the closest meteorological station to the project (14169 Zapopan Jalisco) maintains records since 1980. Data reporting format includes the following basic information: - Location (monitoring station) - Date (on a daily basis) - Total precipitation depth during the time-step

There are several data processing steps to determine the 95th percentile rainfall event using a spreadsheet. These steps are summarized below:

1. Obtain a long-term 24-hr precipitation data set for a location of interest 2. Impor t t he da ta i n to a sp readshee t . I n MS Exce l v4_Ra in fa l l Even ts

Calculator_v02_0_ProjectName 3. Rearrange all of the daily precipitation records into one column if the original data set has

multiple columns of daily precipitation records.

ProjectName �12

4. Review the records to identify if there are early periods with a large number of flagged data

points (e.g., erroneous data points). Select a long period of good recording data that represents, ideally, 30 years or more of data. Remove all of the extra data (if not using the entire dataset).

5. Remove all flagged data points (i.e., erroneous data points) from the selected data set for further analysis.

6. Remove small rainfall events (typically less than 0.1 inches), which may not contribute to rainfall runoff. These small events are categorized as depressional storage, which, in general, does not produce runoff from most sites.

7. Calculate the 95th percentile rainfall amount by applying the PERCENTILE spreadsheet function at a cell. (The v4_Rainfall Events Calculator_v02_0_ProjectName calculates it automatically)

8. The 95th percentile was calculated in the previous step. However, if the user would like to see this information represented graphically and get a relative sense of where individual storm percentiles fall in terms of rainfall depths, the following methodology can be used. Derive a table showing percentile versus rainfall depth to draw a curve as shown below. The PERCENTILE spreadsheet function can be used for each selected percent. It is recommended to include at least 6 points between 0% and 100% (several points should be between 80% and 100% to draw an accurate curve).

Use the spreadsheet software to create of plot of rainfall depth versus percentile, as shown above. The 95th percentile storm event should correlate to the rainfall depth calculated in step 7, however the graph can be used to calculate rainfall depths at other percentiles (e.g., 50%, 90%).

ProjectName �13

The “v4_Rainfall Events Calculator_v02_0_ProjectName” was used to calculate the 95th Percentile.

- Calculations of stormwater volume

According to the recommendations and guidelines for the sewer design indicated by the local authority, the amount of stormwater collection is determined by the following formula:

R= Runoff from the developed site for the 95th percentile rainfall event in liters P= 95th percentile rainfall event in mm (Please note: 1mm of rain is equivalent to 1 liter of water in a 1m2 surface). C= Runoff coefficient A= Area of collection in square meters

R = PCA

Developed site type of surface

*For the Guadalajara Technology

Park, including the LEED

project

Area of collection A Runoff Coefficient C

95th Percentile P R(lt) = P 95th Percentile(mm)x C

Runoff coefficient x A Area (m2)

m2 ft2 mm in lt

Landscaped area 484,471.73 5,214,810.10 0.17

19.50 0.77

1,606,023.78

Non-roof impervious 729,735.10 7,854,802.94 0.95 13,518,342.73

Roof impervious 690,057.52 7,427,717.04 0.95 12,783,315.56

Total (lt) 27,907,682.07

ProjectName �14

- Results demonstrating LID and green infrastructure managing onsite runoff for the 95th

percentile

The vegetated swale is able to manage 29,088.28 m3 (1,027,243.88 f3) which exceeds the 27,907,982.07 lt or 27,982.68 m3 (985,551.42 f3) of stormwater runoff stormwater volume for the Industrial Park (including Project Name project site) according to calculations for the 95th Percentile above.

The following image shows the area occupied by the vegetated swale:

The vegetated swale occupies and area of 14,544.14 m2 (156,551.81 f2) and it has an average of 2m height. The design of the vegetated swale complies with design criteria from the EPA´s Storm Water Technology Fact Sheet: Vegetated Swales.

ProjectName �15

Plan showing location and extension of vegetated swale

Vegetated Swale

The “v4_Rainfall Events Calculator_v02_0_ProjectName” table shows that the strategies manage 100% of the runoff volume from the 95th Percentile Runoff Volume.

- Conclusions

The Stormwater Management Plan is considered to be appropriate because the expected runoff volume for the project site (as well as for the Industrial Park area that is managed under the industrial park´s stormwater management system) is 27,907,682.07 lt or 27,907.68 m3 (985,551.42 f3) and the vegetated swale is able to manage 29,088.28 m3 (1,027,243.88 f3). For this reason, the runoff for the 95th percentile is successfully managed through LID and green infrastructure.

ProjectName �16

For all of the Industrial Park, since the stormwater management system is not exclusive for the LEED project.

IV. Water Quality Analysis (SSc6.2) (QUALITY)

- Approach for meeting LEED credit requirement that 80% of total suspended solids are removed from the stormwater runoff for 90% of the average annual storm events

The intent of the project is to keep most green areas as possible, which should be able to improve the quality of rainwater that is used and infiltrate into the ground. The stormwater management system, under the proposed conditions, is designed to reduce runoff caused by the increase in impervious area.

Stormwater fallen on the Industrial Park (including LEED project) is channeled to a 29,088.28 m3 (1,027,243.88 f3) capacity vegetated swale.

The stormwater management plan manages onsite runoff for the 95th percentile through LID and green infrastructure.

- Details of project’s structural and nonstructural Best Management Practice (BMP) methods incorporated into the design

-Non-structural BMP measures (i.e. pervious pavement, Infiltration trench, vegetated swale)

Infiltration of stormwater. Stormwater is infiltrated by the vegetated swale to recharge aquifers.

Average TS Removal: 81% Area (all of the Industrial Park): 1,904,264.35 m2 (20,497,330.06 sf)

The following Table has been taken from the EPA´s Storm Water Technology Fact Sheet-Vegetated Swales. The TSS removal efficiency for vegetated swales is listed here:

ProjectName �17

- Conclusions

As a result of the water quality analysis and the implemented design, more than 80% of the TSS are removed from 90% of the average rainfall.

ProjectName �18

V. Conclusions

- Evaluation of the quantity and quality of stormwater LID and green infrastructure managing onsite runoff for the 95th percentile and demonstrated compliance with LEED requirements

The implemented Stormwater Management Plan contributes to maintain natural stormwater flows by promoting infiltration. Vegetated swale was designed to minimize impervious surfaces and remove TSS for the Industrial Park (including LEED project).

SSC6.1 - LEED Certification requires to limit the disruption of natural hydrology by replicating natural site hydrology processes, managing onsite, the runoff from the developed site for the 95th percentile of local rainfall events using Low Impact Development (LID) and green infrastructure. The Stormwater Management Plan is considered to be appropriate because the expected runoff volume for the project site (as well as for the Industrial Park area that is managed under the industrial park´s stormwater management system) is 27,907,682.07 lt or 27,907.68 m3 (985,551.42 f3) and the vegetated swale is able to manage 29,088.28 m3 (1,027,243.88 f3). For this reason, the runoff for the 95th percentile is successfully managed through LID and green infrastructure.

SSC6.2 - LEED Certification requires to remove 80% of the average annual post-development total suspended solids (TSS) for 90% of the average rainfall. As a result of the implemented Stormwater Management Plan and the solid removal practices implemented in the design, 81% of the TSS are removed from the stormwater runoff.

ProjectName �19

VI. APPENDIX.

-Bibliography

Normas de Instalaciones Sanitarias, Hidráulicas y Especiales. ND-01-IMSS-HSE-1977. Instituto Mexicano del Seguro Social.

Reglamento de Construcciones para el Distrito Federal. Gaceta Oficial del Distrito Federal publicada el 29 de enero del 2004.

-Electronic References

Secretaria de Comunicaciones y Transportes. Dirección General de Servicios Técnicos. Isoyetas de intensidad de lluvia. [en línea] [México]. Disponible en World Wide Web: http://www.sct.gob.mx http://dgst.sct.gob.mx/index.php?id=452 http://www.inegi.org.mx/geo/contenidos/recnat/clima/ http://www.leeduser.com/credit/NC-2009/SSc6.1#doc-tab

ProjectName �20