Austin, Texas 78704 Phone: 512-326-8880 e-mail: lauren ... · Austin, Texas 78704 Phone:...

1405 Hillmont Street Austin, Texas 78704

Phone: 512-326-8880

e-mail: [email protected]

Glenrose Engineering, Inc. glenrose.com Texas Board of Professional Engineers Number F4092

February 17, 2018 Mr. Chad Gilpin City of Dripping Springs City Engineer PO Box 384 Dripping Springs, Texas 78620 Via email: [email protected] Subject: Civil Site Development Plans for Mark Black Wedding Venue

Dear Mr. Gilpin:

I have reviewed the stormwater management and pollution reduction measures

proposed for the Mark Black Wedding Venue. The proposed measures fail to achieve

City of Dripping Springs standards to protect the high quality and character of its

creeks, streams, springs and environment. The applicant’s failure to demonstrate the

required pollution reduction in stormwater treatment and the failure to provide

required storm runoff retention or detention for erosion control constitute major

shortfalls. They are not addressed by supplemental information that has been

provided to the applicant in response to our previous comments. The proposed

stormwater controls must be re-engineered to meet the City’s standards.

My review does not constitute an endorsement of any assumptions, calculations, or

engineering conclusions in the Civil Engineering Site Plans. There are assumptions,

and calculations which contradict both other information in the submittal and widely

published sources. To the extent that these are either insignificant, or could be easily

addressed, I have not included them in this letter.

Basis for Opinions

My opinion below are based on my review of these documents:

• Preliminary Drainage Study; Mark Black Wedding Venue by Kimley Horn,

November 2017;

Friendship Alliance, Inc. February 17, 2018 of 6


• Letter from Andrew Evans, P.E., Kimley-Horn and Associates, Inc. to Chad

Gilpin, P.E., Dripping Springs City Engineer, November 30, 2017;

• Civil Site Development Plans for the Mark Black Wedding Venue sealed by

Andrew S. Evans, P.E., on December 18, 2017;

• Letter from Andrew Evans, P.E., Kimley-Horn and Associates, Inc. to Chad

Gilpin, P.E., Dripping Springs City Engineer, February 12, 2018;

• Sizing Vegetative Filter Strips for S.O.S. Requirements, no date or seal;

• City of Dripping Springs, Texas Code of Ordinances Title II Building and

Development Regulations;1

• City of Dripping Springs Technical Construction Standards and Specifications

(TCSS) Manual; and

• City of Austin Environmental Criteria Manual, Section 1 – Water Quality

Management.

Failure to Comply with Title II Building and Development

Regulations: Missing Information

• §22.05.015(c)(3) requires the applicant to demonstrate 90% removal of the

net increase for the design storm event of total suspended solids, total

phosphorus, and oil and grease. The following required information is missing.

References in parentheses document the location of the requirement.

o Erosion and Sedimentation Control Engineering Report (City of

Dripping Springs TCSS, §7.2.5(f));

o Water Quality Control Engineering Report (City of Dripping Springs

TCSS, §7.2.5(c));

1 http://z2.franklinlegal.net/franklin/Z2Browser2.html?showset=drippingspringsset, accessed on February 15, 2018.

http://z2.franklinlegal.net/franklin/Z2Browser2.html?showset=drippingspringsset



o Water Quality Control Design Report (City of Dripping Springs TCSS,

§7.2.5(i));

o The length, width, and area of each vegetative filter strip (required for

the necessary calculations);

o Information regarding the length of the contributing drainage area to

vegetative filter strips in direction of flow (maximum 150 feet; level

spreader required at greater than 72 feet) (Austin ECM 1.6.7.B.

Vegetative Filter Strips);

o Information regarding the two-year, three-hour hydraulic loading rate

(<0.05 cfs/ft) to each vegetative filter strip (Austin ECM 1.6.7.B.

Vegetative Filter Strips);

o Failure to demonstrated at least 65% infiltration over the length of the

filter strip (Austin ECM 1.6.7.B. Vegetative Filter Strips);

o Failure to provide information regarding filter strip area per

contributing area (Austin ECM 1.6.7.B. Vegetative Filter Strips);

o Baseline pollutant loading calculations;

o Designation of vegetated filter strip easements or conservation lots

(Austin ECM 1.6.7.B. Vegetative Filter Strips);

o An Approved Integrated Pest Management Plan with recorded

restrictive covenant (Austin ECM 1.6.7.B. Vegetative Filter Strips);

o Accurate information regarding soil infiltration rates based on

published data (Austin ECM 1.6.7.B. Vegetative Filter Strips);

o Information regarding soil infiltration based on field sampling (Austin

ECM 1.6.7.B. Vegetative Filter Strips); and

o Calculations demonstrating 90% removal of increased with either total

phosphorus or oil and grease (City of Dripping Springs Code of

Ordinances §22.05.015(c)(3).

• §22.05.019(e) requires site designs to provide for discharge of stormwater

into a waterway, adequate retention and/or detention to limit flows into the



receiving waterway to the level consistent with the flow rate of the two-year,

three-hour rainfall event evenly distributed over a 24-hour period.

Failure to Comply with Title II Building and Development

Regulations: Wrong Information

• Sheet 37/42 Note 3 states the following: “According to TCEQ RG-348, vegetative

filter strips have a TSS removal efficiency of 85%, Bayfilters have a TSS removal

efficiency of 87% and rainwater harvesting has a TSS removal efficiency of

100%.” Firstly, City of Dripping Springs requires calculations based on the City

of Dripping Springs TCSS and the TCSS references the City of Austin

Environmental Criteria Manual as a basis for calculations, not TCEQ RG-348.

Furthermore, TCEQ RG-348 does not list Bayfilters as having a TSS removal

efficiency of 87%. Procedures for determining Bayfilter removal efficiencies

are described in TCEQ RG-348 Addendum Section 3.4.19.

• Based on information regarding the Bayfilters provided in the plans, the

Bayfilters proposed by the applicant would not achieve a removal efficiency of

85%. The estimated removal efficiencies, based on TCEQ RG-348 methods, are

significantly lower than those assumed by the applicant, as I have

demonstrated in the following table.

Pollutant Removal System

TSS Removal Efficiency Assumed

by Applicant

TSS Removal Efficiency based on TCEQ RG-348

Methods2

BF 1 87% 65%

BF 2 87% 68%

BF 3 87% 52%

BF 4 87% 58%

2 Based on the methods outlined in TCEQ RG-348 Addendum Section 3.4.19 and Bayfilter information presented on Sheet 42 of 42.



• The applicant has presented a calculation of total phosphorus and oil and

grease removal based on an analysis that assumes one single vegetative filter

strip to treat the entire site area of 64 acres.3 Based on the proposed plans,

however,4 the drainage areas to the vegetative filters will be significantly less

than 64 acres. The vegetative filter strip pollution load calculations also

assume that the 10 percent impervious cover proposed for the site is

distributed across this larger area. Both assumptions do not apply to the site

and, therefore, the calculated required filter strip area is meaningless. The

sizing methodology is based on LCRA Nonpoint Source Pollution Control

Technical Manual, January 1991, which is not equivalent to the City of Dripping

Springs standards for water quality protection. The document is not signed,

sealed, or dated by a Texas Registered Professional Engineer and is, therefore,

an unacceptable basis for site plan approval.

The applicant proposes numerous vegetative filter strip controls. The

effectiveness of each of these vegetative filter strips depends on its size relative

to the size and imperviousness of the contributing area. The applicant has

failed to provide the necessary information to evaluate effectiveness, which is

required both by the applicable engineering methods and by applicable City of

Dripping Springs standards.

• Sheet 25 of 42: The soil hydrologic group is identified as “C”. Most of the site,

including areas for which vegetative filter strips are proposed is designated as

hydrologic group “D”.5

3 Sizing Vegetative Filter Strips for S.O.S. Requirements, no date or seal.

4 See • Civil Site Development Plans for the Mark Black Wedding Venue sealed by Andrew S. Evans, P.E., on December 18, 2017 5 See attached relevant map and information from the USDA Natural Resources Conservation Service Soil Web Survey.



Please let me know if I can answer any questions.

Sincerely,

Lauren Ross, Ph. D., P. E. President Glenrose Engineering, Inc. Attachments: Sections from City of Dripping Springs TCSS Manual (sections of noncompliance highlighted) Sections from City of Austin Environmental Criteria Manual Sections from TCEQ RG-348 Addendum

Sealed on February 16, 2018

City of Dripping Springs TCSS

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TABLE OF CONTENTS SECTION 1. STANDARD SPECIFICATIONS AND DETAILS 1

1.1. General 1 1.1.1. Earthwork 1 1.1.2. Subgrade and Base Construction 1 1.1.3. Street Surface Courses 1 1.1.4. Concrete Structures and Miscellaneous Concrete 2 1.1.5. Underground Piped Utilities 2 1.1.6. Environmental Enhancement 3 1.1.7. Incidental Construction 4 1.1.8. Urban Transportation 4 1.1.9. Project Management 5 1.1.10. Electrical 6

1.2. Standards 6

1.3. Exceptions to the Referenced Standards 6

1.4. City of Austin, Texas Standard Specifications 6 1.4.1. Series 200 – “Subgrade and Base Construction” 6 1.4.2. Series 400 – “Concrete Structures and Miscellaneous Concrete 6 1.4.3. Series 500 – “Underground Piped Utilities” 6 1.4.4. Series 600 – “Environmental Enhancement” 7 1.4.5. Series 700 – “Incidental Construction” 8 1.4.6. Series 800 – “Urban Transportation” 8 1.4.7. Series 1800 – “Private Development” 8

1.5. Additions to the Referenced Standards 9 1.5.1. General 9 1.5.2. Indemnification 9

SECTION 2. TRANSPORTATION FACILITIES 10

2.1. General 10 2.2. Definition of Transportation Systems 10 2.3. Exceptions to the Referenced Standards 10

2.3.1. General 10 2.3.2. Hays County Subdivision and Development Regulations 10 2.3.3. Hays County Specifications for Paving and Drainage

Improvements 10 SECTION 3. WATER AND WASTEWATER FACILITIES 11


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3.1. General 11


SECTION 4. DRAINAGE FACILITIES 12

4.1. General 12

4.2. Definition of Drainage Facilities and Systems 12 4.3. Exceptions to the Referenced Standards 12

4.3.1. General 12 4.3.2. City of Austin, Texas Drainage Criteria Manual 12 4.3.3. City of Austin, Texas Standard Specifications 13

SECTION 5. ENVIRONMENT 14 5.1. General 14 5.2. Definition of Environmental Facilities and Systems 14 5.3. Exceptions to the Referenced Standards 14

5.3.1. General 14 5.3.2. City of Austin, Texas Environmental Criteria Manual 14 5.3.3. City of Austin, Texas Standard Specifications 17 5.3.4. Calculation of the Impervious Cover allowance for Isolation of

Roof Runoff and Irrigation 17

SECTION 6. BUILDINGS 20

6.1. General 20


SECTION 7. ENGINEERING SUBMITTALS 21

7.1. Licensed Engineer Requirements 21 7.1.1. General 21 7.1.2. “Issued for Review” 21 7.1.3. “Issued for Construction”, “Issued for Permitting”, “Issued for

Platting” 21 7.1.4. Licensed Engineer Sealed Documents 21

7.2. Content of Engineering Submittals 24 7.2.1. Non-Residential Building Plan Requirements 24 7.2.2. Drainage 24 7.2.3. Transportation 28 7.2.4. Utilities 33


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7.2.5. Water Quality Management 40

SECTION 8. SITE PLAN REQUIREMENTS 46

8.1. Cover Sheet 46 8.2. Notes 46

8.3. Approval Blocks 46

8.4. Base Information 46

8.5. Additional Requirements 50

8.5.1. Compatibility Standards 50 8.5.2. Off-Site Parking 50

8.6. Drainage Plan 51 8.7. Construction Details 52

8.8. Environmental Site Plan and Report Submittal Information 53

8.9. Engineer’s Summary Letter 61

SECTION 9. DRAINAGE AND WATER QUALITY CONTROL DESIGN AND CONSTRUCTION ENVIRONMENT COMPATIBILITY REQUIREMENTS 63

9.1. General 63 9.2. Compatibility Design Standards 63

9.2.1. General 63 9.2.2. Drainage Control 63 9.2.3. Water Quality Controls 64

SECTION 10. NON-POINT SOURCE POLLUTION CONTROL MANAGEMENT PERFORMANCE STANDARDS 66

10.1. Removal of Annual Pollutant Load 66 10.1.1. For development not using on-site irrigation with treated

wastewater effluent 66 10.1.2. For development using on-site irrigation with treated wastewater

effluent or with septic system effluent 66 10.1.3. Background and Developed Sites Pollutant Concentrations and

Pollutant Loads 67 10.1.4. Water Quality Volume 67 10.1.5. Impervious Cover 67 10.1.6. Impervious Cover Allowances 68 10.1.7. Critical Water Quality Zones (CWQZ) 69


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10.1.8. Critical Environmental Features (CEF) 69 10.1.9. Overlapping Critical Water Quality Zones 69

10.2. Impervious Cover 70

10.2.1. The following shall be considered as impervious cover 70 10.2.2. The following will not be considered as impervious cover 70 10.2.3. The following shall not be included in the total site area against

which the allowable impervious cover percentage limit is applied 70 10.2.4. Restrictions 71

10.3. Critical Water Quality Zones (CWQZ) 71

10.3.1. All development activities, including temporary construction activities and landscaping activities, shall be restricted from the CWQZ, except the following development activities may be allowed if approved by the City 71

10.3.2. All utilities, other than wastewater shall be located outside the CWQZ except for crossings 71

10.3.3. All water quality control discharges and stormwater discharges onto a CWQZ shall 71

10.4. Overland Flow 72

10.5. Infiltration 72

10.6. Steep Slopes 72

10.7. Vegetation 73

10.8. Water Quality Controls (WQC) 73

10.9. Erosion Control Requirements 75

10.10. Isolation of Roof Runoff and Irrigation 76

10.11. Erosion Hazard Setbacks 77

10.12. Non-Residential and Multi-Family Permanent Construction 77

10.13. Residential Lots with a Building Permit 77


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SECTION 5. ENVIRONMENT

5.1. General

The environmental assessments and the design and construction of environmental facilities and systems within the incorporated limits and the ETJ of the City of Dripping Springs shall comply with the following standards, which are incorporated herein by reference and which are modified herein:

City of Austin, Texas Environmental Criteria Manual, Section 1 "Water Quality Management", latest edition; City of Austin, Texas Standard Specifications, latest edition;

5.2. Definition of Environmental Facilities and Systems

Environmental facilities and systems shall include environmental assessments, water quality controls, temporary erosion and sedimentation controls, permanent erosion and sedimentation controls, and on-site irrigation with wastewater effluent.

5.3. Exceptions to the Referenced Standards

10.3.4. General

(a) The following exceptions shall apply to the referenced standards.

(b) All references to the City of Austin shall be construed to mean

the City of Dripping Springs. (c) All provisions and standards of the City of Dripping Springs

Code of Ordinances shall be applicable and shall govern if there is a conflict with the standards referenced in Section 5.1.

10.3.5. City of Austin, Texas Environmental Criteria Manual, Section

1.

(a) Section 1.2.1 "Fiscal Security". Fiscal security shall be determined by the owner's consulting engineer in accordance with Subsection (c).

(b) Section 1.2.3.1. "Submittal Requirements for Projects in the

Barton Springs Zone". This section does not apply. (c) Subsection A, “Application of SOS Ordinance”. This

Subsection does not apply.

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(d) Section 1.2.3.2. "General Rules" (1) Subsection G. "Operating Permits"

i) Annual operating permits shall be required

for all water quality controls. ii) "Commercial" shall be construed to mean

"non-residential". iii) The City will not operate or maintain water

quality controls.

(e) Section 1.2.3.3. "Site Management". This section does not apply.

(f) Section 1.4.1.1. "City of Austin Erosion and Sediment Control

Policy".

(1) Subsection D. "Ordinance Authority". This section does not apply.

(g) Section 1.4.4 "Vegetative Practice". Vegetative types for

erosion and sedimentation control shall comply with the City of Dripping Springs Code of Ordinances.

(h) Section 1.5.0 "Revegetation Criteria". Revegetation types shall

comply with the City of Dripping Springs Code of Ordinances. (i) Section 1.6.0 "Design Guidelines for Water Quality Controls".

(1) Section 1.6.1. "Introduction". "Commercial" shall

be construed to mean "non-residential" (2) Section 1.6.3. "Maintenance and Construction

Responsibilities".

i) Subsection A. "Maintenance Responsibilities". Owner/developer shall maintain all water quality controls.

ii) Subsection B. "Maintenance Design Requirements".

Fencing and barriers shall comply with the City of Dripping Springs Code of Ordinances.

(3) Section 1.6.8 "Rules to Implement On-Site Control of the Two-Year Storm ". All development shall be subject to the two-year storm runoff control requirements of this section.

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(4) Section 1.6.9.2 "Pollution Prevention Measures".

i) Subsection B through Subsection F.

These subsections do not apply. (5) Section 1.6.9.3 "Control Measure Design".

i) Subsection A. "Baseline Pollutant Load

Calculations". Baseline pollutant loads shall be calculated for all areas which are to be developed for the pollutants listed in the City of Dripping Springs Code of Ordinances.

(6) Table 1-9 "Runoff Coefficient Table". The runoff

values for the "NonRecharge Zone Runoff' shall be used.

(7) Table 1-10 "Baseline Pollutant Concentrations and

Unit Area Loads for Undeveloped Sites". Oil and Grease pollutant concentrations shall be added to Table 1-10 and shall be 0 mg/l.

(8) Table 1-11 "Standard Pollutant Concentrations for

Developed Sites".

i) "Commercial" shall be construed to mean `non-residential".

ii) Oil and Grease pollutant concentration shall be added to Table 111 and shall be 5 mg/1 for all conditions. The load calculation for oil and grease under developed conditions shall represent only the paved surfaces of the development and is not required to include rooftops.

(j) Section 1.7.0 "Floodplain Modification Criteria".

(1) Section 1.7.1 "Introduction". These guidelines apply only to development proposed in a floodplain or in a critical water quality zone.

(2) Section 1.7.3 "Application of Guidelines". These

guidelines apply to the development of all floodplains and critical water quality zones located within the jurisdictional boundaries of the City.

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(3) Section 1.7.4 "Appeals". This section does not apply.

(k) Section 1.8.0. "Impervious Cover Calculation Criteria".

(1) Section 1.8.1 "Calculations"

i) Subsection A. Impervious cover calculations shall include all swimming pool surface areas and sidewalks.

ii) Subsection D. Maximum pavement width for imperious cover calculations shall be 30 feet.

iii) Subsection E. Maximum pavement width for impervious cover calculation shall be 30 feet.

(2) Section 1.8.2. "Construction on Slopes"

i) Subsection A. This subsection does not apply. ii) Subsection B.

Building and parking areas may be constructed on slopes in excess of 15 percent, subject to the requirements of Subsection B.2 through B.6.

Subsection B.1. This subsection does not apply.

Subsection B.2. This subsection applies to development on slopes in excess of 15 percent.

Subsection B.3. This subsection applies to development on slopes in excess of 15 percent.

(l) Section 1.9.0 "Need for Water Quality Controls". This section does not apply.

(m) Section 1.10.0 "Point Recharge Identification Criteria". This

section does not apply.

10.3.6. City of Austin, Texas Standard Specifications.

The exceptions of the City of Austin's Standard Specifications with respect to environmental controls are given in Section 1.00 of this TCSS Manual.

10.3.7. Calculation of the Impervious Cover Allowance for Isolation of Roof Runoff and Irrigation

(a) General


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This section provides guidelines and example calculations for determining the impervious cover allowance if roof runoff is isolated, treated as a water quality control, and used for on-site irrigation.

(b) Guidelines and Example Calculations

(1) Example:

i) Non-residential development ii) 3-acres lot (130,680 square feet) iii) Roof area of 40,000 square feet iv) Requesting total impervious cover of 58,000

square feet (44.4% impervious cover) v) Requesting the use of isolation and treatment

and irrigation of roof runoff for the 40,000 \ square feet of roof area.

(2) Calculate the background TSS pollutant load for the

roof area.

i) Roof area = 40,000 ft2 = 0.9183 acres ii) TSS background pollutant load = 55 x 0.049 x

32.5 x 0.2267 x 0.9183 = 18.23 lbs/yr

(3) Calculate the total TSS pollutant load for the roof area. Example:

2. TSS total pollutant load = 110 x 0.248 x 32.5 x

0.2267 x 0.9183 = 184.57 lbs/yr

(4) Calculate the 95% TSS pollutant removal requirement.

i) TSS pollutant caused by development = 184.57

-18.23 = 166.34 ii) 95% removal = 0.95 x 166.34 = 158.03 lbs/yr

(5) Compare the 95% removal requirement against the pollutant removal capacity of the rainwater collection/irrigation system:

i) 1. If the capacity of the proposed system does

not exceed the 95% removal requirement, then zero impervious cover allowance is allowable.

ii) 2. If the capacity of the proposed system exceeds the 95% removal requirement, then


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proceed with the following calculations to determine the allowable allowance.

Example: In this case the capacity of the proposed system is being calculated, which will then be used in selection of the appropriate system that meets the capacity requirement.

(6) Calculate the allowable pollutant removal capacity of the system, which will be the lesser value of the following:

i) 1. Rated pollutant removal capacity of the

proposed system minus the 95% removal requirement; or

ii) 2. Baseline pollutant load plus 5% of the TSS pollutant load caused by development.

Example: The system capacity to be selected must at least be capable of removing the baseline pollutant load plus 5% of the TSS pollutant load caused by development.

Minimum System Capacity = 18.23 + (0.05 x 166.34) = 26.55 lbs/yr

(7) Calculate the developed impervious surface area that would contribute a TSS pollutant load equivalent to the minimum system capacity.

Example: 26.55 = 110 x 0.248 x 32.5 x 0.2267 x area

area= 0.1321 acres= 5,754 ft2

(8) Calculate the impervious cover allowance, which will be the lesser of: i) The equivalent impervious surface area times

50%; or ii) Site area times 5%.

Example:

Equivalent impervious surface area times 50%

0.50 x 5,754 ft2 = 2,877 ft2

Site area times 5%

0.05 x 130,680 ft2 = 6,534 ft2


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Maximum allowable increase in impervious cover = 2,877 ft2


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(d) Water Quality Phasing Plan (with the Water Quality Engineering Report) - Provide documentation of conformance with the standards for:

(1) Delineation of each phase of water quality control

construction; (2) Water quality engineering information necessary to

construct the proposed development for each phase of development.

(e) NPS Annual Operating Permit Application

(1) Delineation of the number and location and type of each water quality control;

(2) Water quality report; (3) Maintenance plan for all required water quality

controls; (4) Concurrence letter certifying that the engineer has

inspected the control and that it is operating as designed.

(f) Erosion and Sedimentation Control Engineering Report -

Provide documentation of conformance with the standards for:

(1) Drainage control analysis; (2) Sedimentation control and filtration analysis; (3) 2-year frequency flood peak flow and velocity for

temporary control; (4) 25-year and 100-year frequency flood peak flows

and velocities for permanent controls; (5) Identification of drainage patterns and disturbed

areas; (6) Identification of drainage control points; (7) Identification of the function of the controls,

including diversion, flow spreading, detention/filtration, and detention/sedimentation;

(8) Selection of control devices;

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(9) Design computation for flow through barriers;

diversion, interceptor and perimeter dikes; interceptor and perimeter swales; stone outlet structures; rock berms; silt fences; sediment filter dikes; sediment basins; sediment traps; stabilized construction entrances; pipe slope drains;

(10) Design computations for permanent controls

including diversions; grasslined swales; level spreaders; stone riprap; gabions; subsurface drains; land grading; grade stabilization structures, paved chutes, and paved flumes;

(11) Vegetative and re-vegetative practices; (12) Permit requirements.

(g) Building and Site Development Plans and Specifications for the Erosion and Sedimentation Control Plan.

(1) Detailed sequence of development showing phases

of construction and at what time and what specific controls are required during each phase of the development;

(2) Schematic representation of each control measure

for each phase of construction, with adequate specifications and details for the controls;

(3) For detention/filtration control devices, a summary

of calculations for runoff from the 2-year storm, including runoff flow rate and assumed flow capacity for each barrier;

(4) Approved areas for materials and equipment storage

and staging, construction traffic, parking, vehicular maintenance, concrete truck washing, and, if appropriate, vehicle washing;

(5) Temporary spoils storage areas, including size, time

of use, and ultimate re-vegetation schedules; (6) On-site permanent spoils disposal areas, including

size, depth of fill and re-vegetation procedures; (7) Contour maps, showing lightly dashed lines for

existing contours and solid lines for proposed

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contours, with each having a contour interval of two (2) feet;

(8) A map of suitable scale on which are indicated all

contributing drainage subareas both on and off-site; (9) Re-vegetation plans for all disturbed areas including

topsoil requirements; seed, sod, and mulch type and rate of application; watering requirements, application technique; maintenance requirements for each specific area, delineation of temporary and permanent vegetation; clear definition of criteria to be utilized in determining when acceptable re-vegetation has taken place;

(10) Delineation of specific areas where specified

slope stabilization techniques are to be utilized and the extent of stabilization to be achieved; and all detention, sedimentation, or sedimentation/filtration ponds;

(11) The identity, address and phone number of

the owner, the owner's engineer, and the designated representative(s) of the owner who will be responsible for the maintenance of the controls and who can authorize appropriate changes to the control plan, if it is discovered to be inadequate;

(12) Dust control.

(h) Building and Site Development Plans and Specifications for the Re-Vegetation Plan for Erosion and Sedimentation Control

(1) Description of vegetation currently existing within

the limits of the development; (2) Description of vegetative cover to be installed,

including temporary and permanent vegetative covers;

(3) Results of analysis of available soil nutrients (N, P,

K, Zn, Mn, Cu, and S) for materials proposed for use as topsoil and a discussion of nutrient amendments required to support the proposed vegetative cover;

(4) Specifications of re-vegetation, including site

preparation; soil nutrient amendments; seed bed

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preparation; seeding rates and composition; mulching rates and composition;

(5) Specifications of re-vegetation using transplanted

live plant materials, including site preparation; soil nutrient amendments; preparation of substrate; transplanting rates and composition; mulching rates and composition;

(6) Maintenance plan for re-vegetation areas including

irrigation, replanting of bare areas; erosion control, fertilizer application; weed control.

(i) Water Quality Control Design Report (as part of the Water

Quality Engineering Report) - Provide documentation of conformance with the standards for:

(1) Delineation of contributing and non-contributing

areas to the water quality volume; (2) Water quality volume calculations; (3) 25-year and 100-year floods peak flows rates and

routing through water quality ponds; (4) Maintenance design requirements; (5) Selection criteria for type of water quality controls; (6) Design calculations for sizing water quality

controls; (7) Calculation of pollutant removal efficiencies; (8) 2-year flood detention analysis; (9) Calculations of baseline pollutant loads; (10) Calculations of developed condition

pollutant loads; (11) Calculations of requirements for reductions

in pollutant loading; (12) Evaluation of the water quality controls to

meet the required pollutant reduction; (13) Calculation of pollutant removal efficiencies

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(j) Plan for Land Application of Treated Wastewater Effluent -

Provide documentation of conformance with the standards for:

(1) Determination of Depth of Effective Soil;

i) General soil survey, ii) Detailed soil survey.

(2) Calculation of living unit equivalents; (3) Delineation of irrigation areas; (4) Delineation of slopes in excess of 15 percent

gradient; (5) Delineation of critical environmental features and

water quality buffer zones and easements; (6) Delineation of the 100-year floodplain; (7) Irrigation system details.

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Addendum Sheet

Complying with the Edwards Aquifer Rules

Technical Guidance on Best Management Practices

RG-348 (Revised July 2005)

January 20, 2017

This addendum sheet lists additional information that is approved for inclusion in “Complying with the Edwards Aquifer Rules Technical Guidance on Best M a n a g e m e n t Practices” (Revised July 2005). The list indicates the location (chapter and section) where this additional information will be placed in a subsequent r e v i s i o n of the manual and provides the specific technical language that has been approved by the TCEQ Edwards Aquifer Protection Program.

RG-348 Location

RG-348 Language Justification

1.4.19 1.4.19 Sediment Control Rolls TCEQ Figure 1-44 Sediment Control Rolls (SCRs) trap detached sediments, reduce slope lengths, and

decrease runoff velocity while allowing runoff to filter through the device. They are reusable, recyclable and constructed of overlapping layers of perforated polymeric sheets

Approval of Innovative Technology

and one or more integrated filter. They are typically hollow tubular or rectangular assemblies that include a location flap and a method to interconnect. This measure has been tested by TxDOT and is approved for use on their projects.

They function similar to silt fences, but because of their lower height are not appropriate for use where overtopping will occur except for extreme events. SCRs reduce runoff water velocity, filter out dislodged soil particles and significantly reduce the effects of slope steepness. SCRs are also used as water flow velocity dissipaters, filtering and trapping sediment. SCRs are designed to be reshaped after being run-over by construction equipment. A picture of a SCR installation is shown in Figure 1-44. This technology may be appealing for use in areas adjacent to foot traffic, since the lack of posts reduces the potential for injury.

Figure 5 Schematic of the BaySeparator System

Selection Criteria

Use only when space constraints make installation of a surface treatment system infeasible

Appropriate for retrofits as well as new development

Achieves greater than 80% TSS removal when properly sized

Can be used as a stand-alone system or in a treatment train configuration Limitations

Requires annual removal of accumulated pollutants

Cost for annual pumping and disposal of accumulated material in the facility is substantial

Manhole cover must be removed to determine whether maintenance is required

Below grade installation may inhibit maintenance access and require special equipment to remove accumulated sediment and other pollutants

Cost Considerations

The cost for a BaySeparator System, based on price/acre and the volume of runoff treated, may be significantly higher than many alternative technologies. Consequently, its primary use will be in space-constrained locations where surface systems such as sand filters may not be feasible.

Section 3.4.19

Design Criteria for BaySeparator System

The BaySeparator is available with several manhole configurations to provide ample options when sizing according to surface area. Table 1 below lists the BaySeparator

units and manhole configurations currently available.

BaySeparator should be located as far upstream in the drainage system as possible. The frequency of the magnitude of a flow rate is dependent on the upstream drainage areas and the level of imperviousness of that drainage area. If the drainage area is too large, the required capture rate may exceed the capacity of a single unit; therefore, the use of multiple units located on lateral storm lines rather than the main trunk line may be more beneficial both physically and economically.

Table 1: BaySeparator Manhole size and surface area (ft2)

Model

Number Surface

Area (ft2) Model

Number Surface Area

(ft2)

1/2K-48” 25.13 5K-72” 56.54

1/2K-60” 39.26 5K-96” 100.53

1K-48” 25.13 10K-120” 157.07

1K-60” 39.26 10K-144” 226.19

3K-60” 39.26

3K-72” 56.54

Design Methodology

As a flow-based BMP, the BaySeparator is designed using the treatment flow rate for the site, as calculated using the Rational Method. The runoff rate from the tributary area is calculated using Equation 3.4:

Q CIA

Where Q = flow rate (cfs)

C = runoff coefficient for the tributary area

I = design rainfall intensity (1.1 in/hr)

A = tributary area (ac).

The runoff coefficient is calculated as the weighted average of the impervious and pervious areas. Runoff coefficient for impervious areas is assumed to be 0.90 and runoff coefficient for pervious areas is assumed to be 0.03.

The overflow rate (hydraulic loading rate) is calculated using Equation 3.5:

VOR Q / A

Where VOR = overflow rate (ft/s)

Q = flow rate calculated using Equation 3.4

A = combined surface area of the primary and storage manholes

The overflow rate can then be used with Table 2 to determine the annual TSS removal for the proposed unit. Select the BaySeparator unit that provides the desired TSS removal.

The BaySeparator unit should be designed to treat the 1.1 in/hr storm, as well as passing the 4 in/hr storm through the unit. In this way, the system will treat virtually all of the annual runoff, and can be assumed to have a value of F = 1 (where F is the fraction of annual runoff treated by the BMP, in Equation 3.9).

For flows in excess of the 4 in/hr storm that may be required to meet local design requirements, the need for external bypass should be evaluated. External bypass needs should be evaluated on a case-by-case basis.

Table 2: BMP Efficiency and Overflow Rate (VOR)

Below is an example sizing using the sizing form required for the BaySeparator. This example shows a BaySeparator being sized for a 0.15 acre site with 0.10 acres of impervious cover.

PROJECT: BaySeparator 10K-120” OT Example Watershed: 1 Date: 3/19/09

EAPP BaySeparator EXAMPLE Compensation Worksheet (Rev. 3/19/09): Use additional sheets for additional catchment areas.

Table 1

Use additional sheets for additional BMPs.

AI = Impervious Cover

Ap = Pervious Cover

A = Total Area

P = Avg. Annual Rainfall (33” for example)

ANI = Increase in impervious cover (new IC – existing IC)

TSS = LM = 27.2 x ANI x P

Effective Area (ac) BaySeparator Model

Surface Area (ft2)

EA < 0.03 1/2K/1K-48” 25.13

0.03 < EA < 0.05 1/2K/1K-60” 39.26

0.05 < EA < 0.07 3K/5K-72” 56.54

0.07 < EA < 0.12 5K-96” 100.53

0.12 < EA < 0.19 10K-120” 157.07

0.19 < EA < 0.27 10K-144” 226.19

Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s)

40% 1.74E-02 55% 6.28E-03 70% 2.54E-03 85% 8.38E-04 41% 1.66E-02 56% 6.00E-03 71% 2.42E-03 86% 7.78E-04 42% 1.58E-02 57% 5.72E-03 72% 2.30E-03 87% 7.18E-04 43% 1.51E-02 58% 5.44E-03 73% 2.18E-03 88% 6.58E-04 44% 1.43E-02 59% 5.16E-03 74% 2.06E-03 89% 5.98E-04 45% 1.35E-02 60% 4.87E-03 75% 1.93E-03 90% 5.36E-04 46% 1.27E-02 61% 4.59E-03 76% 1.81E-03 91% 4.95E-04 47% 1.20E-02 62% 4.35E-03 77% 1.69E-03 92% 4.54E-04 48% 1.12E-02 63% 4.11E-03 78% 1.57E-03 93% 4.13E-04 49% 1.04E-02 64% 3.87E-03 79% 1.45E-03 94% 3.72E-04 50% 9.65E-03 65% 3.63E-03 80% 1.33E-03 95% 3.31E-04 51% 8.88E-03 66% 3.39E-03 81% 1.23E-03 96% 2.90E-04 52% 8.11E-03 67% 3.14E-03 82% 1.13E-03 97% 2.49E-04 53% 7.34E-03 68% 2.90E-03 83% 1.04E-03 98% 2.08E-04 54% 6.56E-03 69% 2.66E-03 84% 9.38E-04 99% 1.67E-04

List only the uncaptured area being compensated for in the BMP. TSS compensation for uncaptured areas can be divided up between multiple BMPs.

BMP Catchment Area A Uncaptured/Untreated Areas (for compensation in BMP)

AI1 = 0.10 AI2 = 0.00

AP1= 0.05 AP2= 0.00

A1 = 0.15 A2 = 0.00

ANI1 = 0.10 ANI2= 0.00

LM1= 90 LM2= 0.00

1 BaySeparator Model Sizing based on Individual Catchment Area to the BMP. Use additional sheets as necessary.

Effective Area (EA) = (0.9 x AI) + (0.03 x AP)

EA = (0.9 x 0.10 _) + (0.03 x 0.05 ) = 0.0915 EA

Model (from Table 1to start) _5K-96” ; Surface area (SA) of model (Table 2) 100.53_ Sq. Ft.

Required TSS Removal for Catchment Area

LM1= 27.2 x 0.10 AI x 33_ P” = 90 _#TSS

2 Overflow Rate

(EA) x 1.1 / Unit surface area (SA)

(( 0.0915 ) x 1.1) / 100.53 = 0.001 f/s

3 BMP Efficiency (Table 2) If the overflow rate is between two percent efficiencies, use the smaller percent efficiency (round the overflow rate to the larger overflow value). Enter rounded overflow value:

Vor = .00104 f/s

BMP % = 83 % / 100 = 0.83 BMP Eff

4 Maximum TSS Removal of BMP: LR1

LR1 = (BMP Eff x P) x [(AI1 x 34.6) + (AP1 x 0.54)]

LR1 = (0.83 x _33 ”) x [( 0.10 x 34.6) + ( 0.05 x 0.54)] = 96 #TSS

TSS Load Credit (LC) to be counted towards untreated areas = LR1 – LM1

LC = [( 96 _) – ( 90 )] = _6 #TSS

5 Required TSS Removal for Uncaptured Area LM2 = 27.2 x 0 ac x _33 ” = 0 #TSS

6 Treatment Available?

If TSSC > TSSUC; Model size is adequate.

If TSSC < TSSUC; Model size is inadequate. Choose a larger model size or redefine the catchment areas. Repeat steps 1 - 6.

6 TSSC (<, >, >, pick) 0 TSSUC

Final Model Size: 5K-96”

7 TSS Treatment per BMP

TSSCA (step 1) + TSSC (step 5) = TSS Removal by BMP

90 #TSS + 0_ #TSS = 90_ #TSS

8 Sub-catchment

Area

Model Number

Drainage Area (Acres)

Impervious Cover (Acres)

Target TSS Removal (lb/yr)

BaySeparator Model

TSS Removal Provided (lb/yr)

BMP Catchment 5K-96” 0.15 0.10 90 5K-96” 90

Uncaptured/Untreated 0.00 0.00 0.00 0.00

Total --- 0.15 0.10 90 90

BaySeparator Worksheet 3_9_09

Table 2: BMP Efficiency and Overflow Rate (VOR)

Table 3: BMP Summary Table for the Site

Complete this table to show the types of BMPs and TSS treatment amounts for the site. Provide additional, as needed.

BMP BMP Type Total Impervious Calculated TSS TSS Treatment by

Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s) Eff (%) Overflow (ft/s)

40% 1.74E-02 55% 6.28E-03 70% 2.54E-03 85% 8.38E-04

41% 1.66E-02 56% 6.00E-03 71% 2.42E-03 86% 7.78E-04

42% 1.58E-02 57% 5.72E-03 72% 2.30E-03 87% 7.18E-04

43% 1.51E-02 58% 5.44E-03 73% 2.18E-03 88% 6.58E-04

44% 1.43E-02 59% 5.16E-03 74% 2.06E-03 89% 5.98E-04

45% 1.35E-02 60% 4.87E-03 75% 1.93E-03 90% 5.36E-04

46% 1.27E-02 61% 4.59E-03 76% 1.81E-03 91% 4.95E-04

47% 1.20E-02 62% 4.35E-03 77% 1.69E-03 92% 4.54E-04

48% 1.12E-02 63% 4.11E-03 78% 1.57E-03 93% 4.13E-04

49% 1.04E-02 64% 3.87E-03 79% 1.45E-03 94% 3.72E-04

50% 9.65E-03 65% 3.63E-03 80% 1.33E-03 95% 3.31E-04

51% 8.88E-03 66% 3.39E-03 81% 1.23E-03 96% 2.90E-04

52% 8.11E-03 67% 3.14E-03 82% 1.13E-03 97% 2.49E-04

53% 7.34E-03 68% 2.90E-03 83% 1.04E-03 98% 2.08E-04

54% 6.56E-03 69% 2.66E-03 84% 9.38E-04 99% 1.67E-04

Catchment Area

or Model Drainage Area (ac)

Cover (ac) Removal (lb/yr) (Lm)

BMP (lb/yr)

A 5K-96” 0.15 0.10 90 90

B C D

Uncaptured --- 0.00 0.00 0.00 ---

Total --- 0.15 0.10 90 90

Section 3.5.21

Maintenance Guidelines for BaySeparator™ System The BaySeparator system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. Like any system that collects pollutants, the BaySeparator™ systems must be periodically maintained for continued effectiveness. Maintenance is a simple procedure performed using a vacuum truck. One of the advantages of the BaySeparator™ systems is the ease of maintenance. The systems were designed to minimize the volume of water removed during routine maintenance, reducing disposal costs. Contractors can access the pollutants stored in each manhole through a 30″ manhole cover. This allows them to gain unobstructed access to the full depth of the system. There is no confined space entry necessary for inspection or maintenance. Vacuum hoses can reach the entire sump area of both manholes to remove sediments and trash. The entire maintenance procedure typically takes less than an hour.

Local regulations may apply to the maintenance procedure. Safe and legal disposal of pollutants is the responsibility of the maintenance contractor. Maintenance should be performed only by a qualified contractor. Contact BaySaver Technologies Inc. at 1-800- 229-7283 for a list of approved contractors in your area.

Inspection and Maintenance

Periodic inspection is required to determine the need for and frequency of maintenance. Inspections should be performed initially every six (6) months. Accumulated sediment and other pollutants must be removed at a minimum every 12 months or when 2 feet of sediment (1.5 feet for the 1/2K model) has accumulated in the bottom of either structure or when visual inspection shows a large accumulation of debris or oil, whichever comes first. Oil or gasoline/diesel spills should be cleaned out immediately.

Inspection Instructions

1. For each BaySeparator™ unit, there are 2 manholes to inspect: the Primary Manhole and Storage Manhole.

2. Remove the manhole covers to provide access to the pollutant storage.

3. Use a dipstick tube equipped with a ball valve (typically a Sludge Judge® or Core Pro®). Follow the proper operating instructions associated with the dipstick tube.

4. Measure the sediment depth in each manhole. After recording the sediment levels, let the dipstick tube drain back into the BaySeparator unit to ensure

pollutants do not leave the unit or the site. Conduct maintenance if necessary.

5. Conduct a visual observation of the unit for trash/debris and structural integrity (cracks, slumping pipes, etc.).

6. Replace the two manhole covers.

7. Conduct a visual observation of the discharge point for soil erosion.

Maintenance Instructions

1. For each BaySeparator™ system, there are 2 manholes to clean: the Primary Manhole and Storage Manhole.

2. Remove the manhole covers to provide access to the pollutant storage.

3. Storage Manhole: Use a vacuum truck to remove and collect all water, debris, oils, and sediment.

4. Storage Manhole: Use a high pressure hose to clean the manhole of all the remaining sediment and debris. Then, use the vacuum truck to remove the rinse water.

5. Primary Manhole: Use a submersible pump to pump the bulk of the water from the Primary Manhole into the clean Storage Manhole. Stop pumping when the water surface falls to one foot above the accumulated sediments.

6. Primary Manhole: Use a vacuum truck to remove and collect all remaining water, debris, and sediment.

7. Primary Manhole: Use a high pressure hose to clean the manhole of all the remaining sediment and debris. Then, use the vacuum truck to remove the rinse water.

8. Both Manholes: On sites with a high water table or other conditions which may cause flotation, it is necessary to fill the manholes with clean water after maintenance

9. Replace the two manhole covers.

10. Dispose of the polluted water, oils, sediment, and trash at an approved facility.

Most local regulations prohibit the discharge of solid material into the sanitary system. Check with the local sewer authority for any required permits and/or conditions to discharge the liquid.

Many places require the pollutants removed from BaySeparator™ systems to be treated in a leachate treatment facility. Check with local regulators about disposal requirements.

11. Additional local regulations may apply to the maintenance procedure.

This procedure is intended to remove all the collected pollutants from the system while minimizing the volume of water that must be disposed. Additional local regulations may apply to the maintenance procedure. Safe and legal disposal of pollutants is the responsibility of the maintenance contractor; therefore maintenance should be performed only by a qualified contractor.

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