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HomeMy WebLinkAboutOrdinance 2624 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 ORDINANCE NO. 2624 2 4 AN ORDINANCE OF THE CITY OF NORTH RlCHLAND HILLS, TEXAS, PROVIDING FOR DEVELOPMENT OF A DETENTION OR RETENTION DRAINAGE FACILITY IN THE CITY; DECLARING PURPOSES; STATING SCOPE OF AUTHORITY; DEFINING TERMS; DESCRIBING DESIGN REQUIREMENTS; DESCRIBING THE PLAN REVIEW AND APPROVAL PROCESS; PROVIDING FOR MAINTENANCE; PROVIDING FOR REPEAL; PROVIDING FOR SEVERABILITY; AND PROVIDING FOR AN EFFECTIVE DATE. 6 8 WHEREAS, the City Council desires to develop a detention or retention drainage facility; NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY OF NORTH RlCHLAND HILLS, TEXAS: SECTION 1. GENERAL A. Statement of Purpose This ordinance sets forth the minimum requirements for development of a detention or retention drainage facility within the city limits of North Richland Hills. The purpose for stating the minimum requirements is to achieve the following: (1.) Protect human life, health, and property. (2.) Minimize expenditure of public funds for maintenance of these types of drainage facilities. (3.) Help maintain a stable tax base and preserve land values. (4.) Preserve the natural beauty and aesthetics of the community. B. Authority Any person, firm, corporation, or business proposing to develop property or improve property within North Richland Hills is subject to the provisions of this ordinance. The ordinance would also apply to anyone wanting to install a detention basin or retention basin within an existing easement, right-of-way, or FIA/FEMA floodplain. C. Related Ordinances The adoption of this ordinance does not change any of the previous provisions of the Subdivision Ordinance No. 1982, the Public Works Design Manual (Resolution No. 95- 11) or the Flood Damage Prevention Ordinance No. 2498. The DetentionlRetention Drainage Facility Ordinance shall clarify, allow, and reasonably control the design, construction, and maintenance requirements of these facilities. W: \Nortt R ~chlandHills\General \Ordinances\Retent ion Drainage FaciE ty. ord. wpd 1 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 D. When DetentionlRetention Ponds will be Allowed 2 4 DetentionlRetention Ponds will only be allowed if the proposed development is discharging into a developed downstream system that does not have the capacity to handle the runoff as mandated in the City's drainage criteria. A developed downstream system may include Texas Department of Transportation drainage facilities and! or existing North Richland Hills subdivisions that have drainage improvements that were constructed after 1984. DetentionlRetention Ponds will not be allowed if discharging to an undeveloped street or property, or if discharging to an area where the City's Master Drainage Plan indicates drainage improvements are required. 6 8 E. Definitions Unless specifically defined below, words or phrases used in this ordinance shall be interpreted to have their common usage meaning and give this ordinance its most reasonable meaning, subject to final interpretation by the Public Works Department. (1.) Design Flood - The flood having a one percent (1 %) chance of being equaled or exceeded in any given year based upon fully developed watershed conditions. This is commonly known as the 100-year frequency flood, or base flood. "Fully developed" conditions shall be based on the most current Future Land Use Assumption Plan for the City of North Rich1and Hills, or current zoning map; whichever produces the higher runoff coefficients for the drainage area generating the design flood discharge. (2.) Detention Basin - A dry basin or depression constructed for the purpose of temporarily storing stormwater runoff and discharging all ofthat runoff over time at a rate of flow equal to or less than which would have occurred prior to installation of the basin. This definition includes all structural components proposed for the basin (i.e. inlet structures, outlet structures, walls, fences, piping, headwalls, etc.) (3.) Federal Emergency Management Agency (FEMA) - The Federal agency which has and does assist the Federal Insurance Administration administering the National Flood Insurance Program. (4.) Federal Insurance Administration (FIA) - The division of the Federal government which oversees the Flood Insurance Program with the help ofFEMA. (5.) Freeboard - The vertical distance between the design flood surface and the top of an open channel, dam, levee, detention or retention basin. The freeboard allows for wave run-up, wind tide, hydraulic jump, or other design conditions without overtopping the structure. W: \Nortr R .chlandHills\General \Ordinances\Retention Drainage Facility .ord. wpd 2 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2 (6.) Frequency - The reciprocal of the exceedance probability. For example, a 100- year frequency storm is one which has a one (1 %) percent chance of being equaled or exceeded in any year, and a 5-year storm has a twenty (20%) percent chance of being equaled or exceeded in any year. 4 6 (7.) Hydraulics - Hydraulics is concerned with the determination of the maximum stage or elevation reached by the waters of a flood at a given location. A flood is said to have occurred when the maximum stage or elevation results in an overflow upon lands that are traditionally useable by man and not normally covered by water. 8 (8.) Hydrology - Hydrology is concerned with the magnitude and frequency of the flood flow. The magnitude of the flood flow is the statement ofthe quantity of water that results from a given storm, whereas, the frequency is the statement of the average return or occurrence of a flood event. (9.) Inflow Hydrograph - Inflow hydrographs are used to determine the stormwater flow volume into a detention basin or retention basin. A hydrograph describes the variation in flow rate over a fixed period oftime. (10.) Landscaping Plan - A plan that identifies how the detention basin or retention basin will be landscaped. This plan will need to include the types of plants, trees, shrubs, grass, decorative fencing, etc., that will be used and will need to be approved by the City. (11.) Normal Pool Elevation - The level at which a retention basin was designed to be prior to a rainfalVrunoff event. In a retention basin, this elevation will be the water surface of the conservation pool. (12.) Open Channel- A channel, branch, creek, or stream in which water flows with a free surface. (13.) Pond - A still body of water located on the surface ofthe earth. (14.) Rational Formula - A means of relating runoff from an area and the intensity of the storm rainfall as defined in the Public Works Design Manual. (15.) Retention Basin - A pond which has been designed to have both a conservation pool for holding water indefinitely, and a flood storage pool for storing stormwater runoff on a temporary basis, for the purpose of reducing the peak discharge from the basin. This definition includes all structural components proposed for the basin (i.e. inlet structures, outlet structures, walls, retaining walls, fences, piping, headwalls, aeration systems, etc.). W: \NortrR .chlandHills\General \Ordinances\Retention Drainage Facility. ord. wpd 3 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2 (16.) Surface Water - Surface water or sheet flow is water on the surface of the ground, the source of which is so temporary or limited that it cannot maintain for any considerable time a stream or body of water having well-defined and established existence. Surface water is derived from falling rains and melting snows, and continues to be such until it reaches some well-defined channel in which it concentrates and flows with other waters, whether derived from the surface or springs, and then it becomes the running water of a stream and ceases to be surface water. 4 6 8 (17.) Swale - A shallow waterway. Swales are required above underground storm drains with capacity, along with the storm drain, to carry a 100-year frequency storm. The City's Public Works Design Manual requires that such swales shall be concrete lined. (18.) Time of Concentration - The estimated time in minutes required for runoff to flow from the most remote section of the drainage area to the point at which the flow rate is to be determined. (19.) Watercourse - A stream of water of such well-defined existence as to make its flow valuable to the owners of the land along its course. A "recognized" watercourse is further defined as a channel, creek, or underground storm drain which has at least a 10-year conveyance of capacity without flooding adjacent property. (20.) Watershed - The area contributing storm runoff to a stream, pond, or drainage system. SECTION 2. DESIGN A. General The design criteria shown or referenced in this section are the minimum requirements to be allowed. The detention/retention basins are to be designed, signed, sealed, and dated by a Professional Civil Engineer registered in the State of Texas, and shall meet all ofthe City's design standards including, but not limited to, those specified in the Public Works Design Manual and the current practices and policies followed by the Public Works Department. The Public Works Director may, in some situations, require the Owner/Developer's Engineer to follow more stringent design guidelines if, in the opinion of the Public Works Director, the situation warrants more than the minimum. Geotechnical and/or soil studies and reports may be requested from the Owner/Developer's Engineer if, in the opinion of the Public Works Director, it is warranted for the proposed design. Any deviation from this criteria must be reviewed and approved by the Public Works Department for use by the Developer and his engineer. W: \Nortt R LchlandHill s\General \Ordinances\Retention Drainage Facil ity. ord. wpd 4 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 B. Runoff Calculations 2 4 Detention/retention facilities shall be designed based on a 100-year frequency storm runoff for the upstream drainage watershed area. 6 (1.) Rational Method - The "rational method" can be used to calculate the runoff rate and volume for drainage areas less than 750 acres. The formula for this method is Q = CIA. 8 (2.) Hydrograph Method - The "hydro graph method" will be used to calculate the runoffrate and volume for drainage areas equal to or greater than 750 acres. One of the following unit hydrograph procedures shall be used. a. HEC-1 developed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers. b. TR55 developed by the U.S. Department of Agriculture, Soil Conservation Service. Use of other hydrograph methods must be approved by the Public Works Department prior to beginning design. C. Flood Routing Methods The flood routing computer program to be used shall be either HEC-2 from the U.S. Army Corps of Engineers, or TR20 from the Soil Conservation Service. Use of other computer program routing methods must be approved by the Public Works Department prior to beginning design. D. Parameters (1.) Inlet - The inlet structure shall allow for the upstream 100-year runoff to be discharged to the pond in a manner which minimizes erosion. (2.) Outlet - The outlet structure for detention basin/retention basin shall be constructed to minimize erosion and allow for the 100-year storm runoff to be discharged in a controlled manner. An outlet control structure will be installed on detention/retention basins to achieve the design discharge equal to or less than the runoff rate which existed from the watershed prior to this proposed development. On the outlet structure for retention basins, an emergency outlet valve and pipe shall be installed. The valve and pipe shall be at least eight (8) inches in diameter and meet all City requirements for water system pipe and valves. Installation of the emergency outlet valve and pipe shall allow the retention basin to be drained to within a maximum of one (1) foot of its design bottom. W: \Narc)' R .chlandHillø\General \ordinances\Retention Drainage Facility.ord. wpd 5 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2 (3.) Storage - The detention/retention storage basin shall be designed to store that volume required to reduce the discharge rate out of the basin to not more than the runoff rate which existed from the watershed prior to this proposed development which includes the basin. The detention/retention storage volume, excluding conservation pool, shall drain out completely within 24 hours of the end of a rainfall event. 4 6 8 (4.) Freeboard - A minimum freeboard of one (1) foot shall be required. This will be the difference in elevation between the 100-year storm design water surface elevation, plus increased elevation created by wave action, wind time or hydraulic jump, anywhere on the detention/retention basin or decorative pond, and the lowest point on the surrounding embankment within the drainage easement. (5.) Side Slopes - The embankment side slopes for the different basins or ponds will be as noted below. The top of the side slope shall be a maximum of twelve (12) inches above the surrounding ground. The embankment of the basin shall not "act" as a levee. The 100-year event shall not be higher than the surrounding ground. a. Detention Basin - Slopes shall be 5:1 or milder. b. Retention Basin - Slopes shall be 4:1 below normal pool depth and 5:1 above. (6.) Overbank - The overbank ofthe retention basin (and all detention basins) shall be block sodded with a Public Works Department-approved native grass. The grass must be relatively established prior to final approval ofthe construction by the City. (7.) Depth- a. Retention Basin - The minimum depth ofthe retention basin shall be four (4) feet from the normal pool elevation to the bottom between the toe of slopes. The maximum depth of a retention basin shall be no greater than ten (10) feet. b. Detention Basin - The maximum depth of the detention storage in a parking lot can be designed is eight (8) inches. For all other detention storage basins, the maximum depth shall not exceed ten (10) feet. (8.) Velocity - The average velocity of flow through the detention or retention basin shall be no greater than five (5) feet per second. W: \Nortt"R .chlandHills\General \Ordinances\Retention Drainage Facility. ord. wpd. 6 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2 (9.) Erosion Control- Erosion control upstream and downstream ofthe basins shall be considered in the design. Erosion control systems shall be installed where necessary as determined by the Public Works Department. 4 6 (10.) Aeration - All retention basins will require aeration systems to be installed. The aeration system will be designed to keep the standing water from stagnating. All electrical service and maintenance costs for an aeration system shall be the Owner/Developer or Homeowners Association responsibility to pay. The aeration system will need to be approved by the Public Works Department with the approval of the basin. The Owner/Developer's Engineer will provide appropriate design calculations and/or shop drawings showing that the aeration system is "sized" adequately for the pond. The aeration system will need to have a screening/filter device to minimize pump blockage. 8 (11.) Water Supply - Provisions shall be made to keep the water surface elevation in a retention basin at the normal pool elevation. This will require the Developer to submit plans and specifications for installation of a water well or wells. Another alternative is a separate irrigation service connection to the City's water system to provide the water supply to recharge the basin or pond as needed. The cost of the water used to recharge the basin shall be the Owner/Deve1oper or Homeowners Association responsibility to pay. Recharge design shall comply with all State and Federal requirements. (12.) Type of Detention - The City will consider different types of detention facilities. Underground detention and parking lot detention are two examples of alternative detention facilities that may be allowed. Underground Detention - will need to include one or more access points for maintenance, and be designed to minimize maintenance. Parking Lot Detention - will need to be designed in the "extra" parking spaces. No detention will be allowed in the required parking spaces. As stated previously, the maximum depth for parking lot detention shall be eight (8) inches. SECTION 3. REVIEW AND APPROVAL A. Submittal Requirements Sufficient information should be submitted on all proposed detention/retention basins. This includes the following items: (1.) Hydraulic Study - All necessary computer runs should be submitted in a bound and labeled booklet form. This should include backwater curve runs on existing conditions prior to development of the subject property, proposed existing W: \NortrR LchlandHi 118 \General \Ordinances \Retent ion Dra inage Fac i 1 i ty . ord. wpd 7 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 2 conditions after development of the subject property, and fully developed conditions after development of the subject property. 4 (2.) Final Construction Plans - Construction plans shall be submitted on standard 24- inch by 36-inch blue line sheets. The plans will include plan and profile of the entire basin with its inlet and outlet structures, edge treatments, fence, landscaping plan, and upstream and downstream erosion control. All design calculations and graphs showing the detention/retention storage design must be included in the construction plans. A grading plan for the basin or pond area, along with the drainage area map, must be included. 6 8 (3.) Landscaping Plan - In addition to Final Construction Plans, a Landscaping Plan shall be submitted on standard 24-inch by 36-inch b1ue1ine sheets. The plans will need to include the locations and types of all plans, trees, shrubs and grass. This plan will also need to include all decorative features such as fencing, waterfalls, etc. The landscaping plan will be approved by the City prior to or with the final plat. (4.) Homeowners Association (HOA) Declarations and Covenants - The HOA Declarations and Covenants must be approved by the City prior to the final plat approval by the City Council. The HOA Declarations and Covenants must provide the following: a. Specifically indicate all maintenance responsibilities ofthe HOA. Provide a detailed list of items the HOA is responsible to maintain (i.e., the HOA is responsible for the maintenance and repair of the aeration fountains, landscaping upkeep, replacement, etc.). b. Provide a detailed schedule indicating when the maintenance is planned to take place and the number of times per year the maintenance will be performed. Include the estimated annual cost for the maintenance of the detention/retention pond and everything associated with the pond. c. An estimate of the annual cost to maintain the pond and a provision for deposit of this sum into an HOA account. This shall be maintained as a minimum balance in the HOA account. The cost will include mowing and maintaining the pond, any aeration fountains, and all other HOA responsibilities. d. Such declarations and covenants must provide for assessments of property owners and for liens to be placed on all property in the subdivision if such assessments for maintenance ofthe detention/retention pond or any item associated with the pond (i.e., aeration fountains, mowing, etc.). Such declarations and covenants shall provide that the City shall have the right to enforce all HOA obligations concerning such maintenance if the HOA W: \Nort l""RichlandHills\General \Ordlnances\Retention Drainage FactIi ty. ord. wpd 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 2 4 6 8 fails to perform, including the right to assess, place liens, and foreclose the same. B. City Review and Approval The normal subdivision review process will be followed. Preliminary construction plans will be submitted with the preliminary plat. Upon approval ofthe preliminary plat by the Planning and Zoning Commission, the Developer can submit the final construction plans, HOA Declarations and Covenants, and final plat to City staff for review and approval. The final plat, plans, and HOA Declarations and Covenants will be reviewed and approved by the Public Works Department and submitted to the Planning and Zoning Commission for their consideration. If the Planning and Zoning Commission recommends approval, then the City Council will consider the plat and plans. If the plat and plans are approved by the City Council, then construction can begin subject to any State and Federal review being necessary. C. Federal and State Review and Approval All projects will be reviewed in accordance with the Flood Damage Prevention Ordinance. Those projects which require a Flood Insurance Rate Map revision will be required to comply with the paragraphs contained in this subsection. (1.) Conditional Letter of Map Revision (CLOMR) - The Developer's engineer will submit the necessary hydrologic and hydraulic studies, along with an application for a CLOMR. The application will include the preliminary application fee, along with all support documentation deemed necessary by the City. After review and approval by the City, the application will be forwarded to the appropriate Federal and State agencies. A permit to construct the necessary fill and/or public improvements will not be issued until a favorable response is received from the appropriate Federal and State agencies. (2.) Revision to the Current Flood Insurance Rate Map - After the items of construction have been installed and inspected by the City, the Developer's Engineer will submit an application for a map revision or amendment as appropriate. The City will review the application and supportive documents for compliance with City ordinances. After review and approval by the City, the application and supporting documents will be forwarded to the appropriate Federal and State agencies for review. The City will not grant permission to occupy a new structure within the existing floodplain until a favorable response has been received from the necessary Federal and State agencies. W: \Nort ~ichlandHil18\General \Ordinances\Retention Drainage Facility. ord. wpd 9 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 SECTION 4. CONSTRUCTION 2 A. Preconstruction Meeting 4 6 The normal preconstruction conference must be held for any project to be constructed in the City. The following items will be required for the basin prior to or at the meeting: 8 (1.) City inspection fees for Public Works construction. (2.) Any necessary Federal, State, railroad company, or utility company permits. (3.) Owner/Developer Maintenance Covenant. (4.) Homeowners Association Declarations and Covenants / deed restrictions (filed copy). B. Erosion Control The Owner and the Contractor are totally responsible for the control of erosion during construction. The Owner and Contractor shall provide all erosion control systems necessary during the construction period in order to minimize the detrimental effect of the sedimentation on downstream property owners and its accumulation in the public rights- of-way and drainage system. C. Landscaping All landscaping must be installed in accordance with the approved landscaping plan prior to the Public Works Department approving the construction. D. Maintenance Bond A two-year Maintenance Bond on the construction of all basins and their associated facilities (including landscaping) will be required. The Maintenance Bond will be for twenty percent (20%) of the total construction price for the basin. E. City Approval The Public Works Department will issue a "letter of approval" for the detention or retention basin after all construction on the basin is complete. No building permits will be issued in a residential subdivision until this approval has been given. In a commercial, industrial, or multi-family addition, only the permit to install the plumbing and foundation will be allowed prior to this approval, unless Federal and State permits are required. W: \Nor~ichlandHills\General \Ordinances\Retention Drainage FaCility.ord.wpd 10 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 F. Construction Standards 2 4 All construction is to be in accordance with the City of North Richland Hills' standards and specifications. 6 SECTION 5. MAINTENANCE RESPONSIBILITIES 8 A. General The maintenance ofthe detention or retention basin is essential to its proper functioning. This section outlines those maintenance responsibilities with reference to all parties involved. B. Contractor The Contractor is initially responsible for all erosion control and other maintenance items related to the basin construction until it is approved as complete in writing by the City. C. OwnerIDeve1oper The OwnerlDeveloper shall execute the DetentionlRetention Storage Facility Maintenance Covenant prior to Council approval ofthe plat. The Owner/Deve10per shall be responsible for all maintenance absent aHOA or until the HOA assumes responsibility. D. Homeowners Association In residential subdivisions where a detention or retention basin is to be constructed, a Homeowners Association (HOA) must be established. The HOA shall collect assessments no less often than once annually. This assessment shall include an amount to be collected and used for maintenance of the basin. The amount shall cover expected annual routine maintenance costs. The HOA Declarations and Covenants must provide a means for the HOA to maintain a minimum balance adequate to meet anticipated annual expenditures. The HOA shall be responsible for the following: (1.) Mowing ofthe basin and all areas around the basin controlled by the HOA based on a pre-approved schedule. (2.) The upkeep and replacement of all landscaping. (3.) Operation and maintenance of aeration systems (including power cost and replacement cost). (4.) Trash and debris removal based on a pre-approved cleaning schedule and scope. W: \Nort t1tichlandHills\General \Ordinanceø\Retention Drainage Facility. ord .wpd 11 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 2 (5.) Operation and maintenance of decorative lighting around the basin. 4 (6.) Any necessary dredging or silt removal from the basin and/or inlet and outlet structures. 6 (7.) Repair and replacement of decorative fencing. 8 (8.) Any "specialty" items not covered by any other party. E. Lot Owners The Owner/Deve1oper Maintenance Covenant and the HOA Declarations and Covenants will be executed by the Owner ofthe subdivision on which the basin is to be installed, and will run with the land. Such Covenants shall provide for assessments to be levied as liens ifunpaid, and for enforcement and collection by the City if the HOA fails to perform. F. City The City will retain the responsibility to insure that the maintenance of a basin is accomplished. The Owner/Deve1oper Covenant shall authorize the City to order maintenance be done if the Owner or HOA does not. If the City has to pay for maintenance costs, it will invoke the lien provision in the Owner/Developer Covenant and/or HOA Declarations and Covenants in order to collect the maintenance expense and any reasonable legal fees incurred. The City will be responsible for the repair and replacement of all structural components deemed necessary by the City. The structural components will include the inlet and outlet structures, storm drainage piping and retaining walls. The City will establish the repair and replacement schedule for all structural components. The City is required, by being a member of the National Flood Insurance Program, to assure that all drainage facilities are maintained which are located within the 100-year floodplain as designated on the Federal Insurance Administration's Flood Insurance Rate Maps (FIRM). SECTION 6. REPEAL. All other Ordinances, or parts of Ordinances in conflict herewith, are hereby repealed to the extent that they are in conflict. W: \Nor j,R1chlandHills\General \Ordinances\Retent1on Drainage Facility .ord, wpd 12 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 It is hereby declared to be the intention of the City Council that the sections, paragraphs, sentences, clauses and phrases of this ordinance are severable and, if any phrase, clause, sentence, paragraph or section of this ordinance shall be declared unconstitutional or otherwise invalid by the final judgment or decree of any court of competent jurisdiction, such invalidity shall not affect any of the remaining phrases, clauses, sentences, paragraphs and sections ofthis ordinance, since the same would have been enacted by the city council without the incorporation in this ordinance of any such invalid phrase, clause, sentence, paragraph or section. SECTION 7. SEVERABILITY. 2 4 6 8 SECTION 8. EFFECTIVE DATE. This ordinance shall be in full force and effect immediately upon passage. AND IT IS SO ORDAINED. PASSED AND APPROVED this ~f day of 'N)~ ,2002. CITY OF NORTH RlCHLAND HILLS \\\\\.~"'~ '" ," ., ,'~~ ......... ~" ~~" ·~;n··· ..,'..----. ~. \, ~ '/ \ -~ ?I.L.I r \.. ~ ~~\ j~' ~~\ h ./fl¡' ,A T).ES.T: ....... ~, '1" 111/1 W """ " _~AtMÂ/ ~ Patricia Hutson, City Secretary By: ~¿L Mayor W: \Nor.:I' RichlandHills\General \Ordinances\Retention Drainage Facility .ord. wpd 13 , !\/)I N /. P 6-'-..p{ . \..,,"